LP8556TME-E04/NOPB

Product Folder Order Now Support & Community Tools & Software Technical Documents Reference Design LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 LP8556 High-Efficiency LED Backlight Driver For Tablets 1 Features 3 Description • The LP8556 device is a white-LED driver featuring an asynchronous boost converter and six high precision current sinks that can be controlled by a PWM signal or an I2C master. 1 • • • • • • • • • • High-efficiency DC/DC boost converter with integrated 0.19-Ω power MOSFET and three switching frequency options: 312 kHz, 625 kHz, and 1250 kHz 2.7-V to 36-V Boost switch input voltage range supports multi-cell Li-Ion batteries (2.7-V to 20-V VDD input range) 7-V to 43-V Boost switch output voltage range supports as few as 3 WLEDs in series per channel and as many as 12 Configurable channel count (1 to 6) Up to 50 mA per channel PWM and / or I2C brightness control Phase-shift PWM mode reduces audible noise Adaptive dimming for higher LED drive optical efficiency Programmable edge-rate control and spread spectrum scheme minimize switching noise and improve EMI performance LED fault (short and open) detection, UVLO, TSD, OCP, and OVP (up to 6 threshold options) Available in tiny 20-pin, 0.4-mm pitch DSBGA package and 24-pin, 0.5-mm pitch WQFN package 2 Applications The boost converter uses adaptive output voltage control for setting the optimal LED driver voltages as low as 7 V and as high as 43 V. This feature minimizes the power consumption by adjusting the output voltage to the lowest sufficient level under all conditions. The converter can operate at three switching frequencies: 312 kHz, 625 kHz, and 1250 kHz, which can be set with an external resistor or pre-configured via EPROM. Programmable slew rate control and spread spectrum scheme minimize switching noise and improve EMI performance. LED current sinks can be set with the PWM dimming resolution of up to 15 bits. Proprietary adaptive dimming mode allows higher system power saving. In addition, phase shifted LED PWM dimming allows reduced audible noise and smaller boost output capacitors. The LP8556 device has a full set of fault-protection features that ensure robust operation of the device and external components. The set consists of input undervoltage lockout (UVLO), thermal shutdown (TSD), overcurrent protection (OCP), up to 6 levels of overvoltage protection (OVP), LED open and short detection. The LP8556 device operates over the ambient temperature range of –30°C to +85°C. It is available in space-saving 20-pin DSBGA and 24-pad WQFN packages. LED backlights for tablet LCDs space Simplified Schematic Device Information(1) 7V ± 43V 2.7V - 20V L1 D1 1.1 ” 9OUT / VIN ” 15 VOUT VIN CIN PART NUMBER COUT LP8556 VDD EN / VDDIO 1.62V ± 3.6V SW EN / VDDIO VBOOST PACKAGE BODY SIZE DSBGA (20) 2.401 mm × 1.74 mm (MAX) WQFN (24) 4.00 mm × 4.00 mm (NOM) (1) For all available packages, see the orderable addendum at the end of the data sheet. CVLDO VLDO LED1 RFSET FSET LED2 RISET ISET LP8556 LED3 Optional LED4 LED5 PWM MCU LED6 SDA SCL GNDs 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Device Options....................................................... Pin Configuration and Functions ......................... Specifications......................................................... 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 8 1 1 1 2 3 4 6 Absolute Maximum Ratings ...................................... 6 ESD Ratings.............................................................. 6 Recommended Operating Conditions....................... 6 Thermal Information .................................................. 7 Electrical Characteristics........................................... 7 Electrical Characteristics — Boost Converter .......... 8 Electrical Characteristics — LED Driver ................... 9 Electrical Characteristics — PWM Interface ............. 9 Electrical Characteristics — Logic Interface .......... 10 I2C Serial Bus Timing Parameters (SDA, SCL) .... 10 Typical Characteristics .......................................... 11 Detailed Description ............................................ 12 8.1 Overview ................................................................. 12 8.2 8.3 8.4 8.5 8.6 9 Functional Block Diagram ....................................... Feature Description................................................. Device Functional Modes........................................ Programming........................................................... Register Maps ......................................................... 12 13 28 28 32 Application and Implementation ........................ 45 9.1 Application Information............................................ 45 9.2 Typical Application ................................................. 47 10 Power Supply Recommendations ..................... 51 11 Layout................................................................... 51 11.1 Layout Guidelines ................................................. 51 11.2 Layout Examples................................................... 52 12 Device and Documentation Support ................. 54 12.1 12.2 12.3 12.4 12.5 Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 54 54 54 54 54 13 Mechanical, Packaging, and Orderable Information ........................................................... 54 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision L (May 2019) to Revision M • Page Changed Description statement for clarification at Register CFG9E .................................................................................. 38 Changes from Revision K (March 2019) to Revision L Page • Deleted 03H register from Table 9 ....................................................................................................................................... 32 • Deleted 8.6.1.4 Identification section from the Register Bit Explanations............................................................................ 33 Changes from Revision J (January 2018) to Revision K • Added separate ESD Rating for the WQFN package - changed from "±2000" to "±1000".................................................... 6 Changes from Revision I (March 2016) to Revision J • Page Page Added content in VBOOST_RANGE description of CFG9E ................................................................................................ 38 Changes from Revision H (December 2014) to Revision I Page • Changed "25 mA" to "23 mA" - E00, E08 and E09 SQ rows, E09, E11 TME rows ............................................................... 3 • Changed Handing Ratings table to ESD Ratings .................................................................................................................. 6 • Added updated Thermal Information ..................................................................................................................................... 7 • Changed "8" to "10" in PWMres row ...................................................................................................................................... 9 • Changed subtracted 1 from bit value of all Table 4 "ƒPWM [Hz] (Resolution)" entries ......................................................... 20 • Changed subtracted 1 from bit value of all Table 5 "ƒPWM [Hz] (Resolution)" entries except 2402 .................................... 21 • Changed subtracted 1 from bit value of all Table 11 "ƒPWM [Hz] (Resolution)" entries ....................................................... 45 2 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 • Changed "via EPROM" in Table 13 title to "With an External Resistor" ............................................................................. 46 • Changed subtracted 1 from bit values of all Table 13 "ƒPWM [Hz] (Resolution)" entries except 2402 ................................. 46 Changes from Revision G (November 2013) to Revision H • Page Added Pin Configuration and Functions section, Handling Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section ................................................................................................................................................................................... 1 Changes from Revision E (August 2013) to Revision G Page • Changed Description of "1=" for OCP row in Fault table, STATUS Register Section.......................................................... 34 • Changed A7h values for E02, E03, E04, E06, E07, E09, E11 DSGBA EPROM Bit Explanations tables ........................... 36 • Deleted E00, E01, E08, E10, E12, E13 columns and A8H row from 3 EPROM Bit Explanations table.............................. 36 • Changed values for E00, E08, E09 WQFN EPROM Settings table..................................................................................... 37 5 Device Options ORDERABLE DEVICE (1) PACKAGE TYPE DEVICE OPTION LP8556SQ-E00/NOPB LP8556SQE-E00/NOPB LP8556SQX-E00/NOPB LP8556SQ-E08/NOPB LP8556SQE-E08/NOPB LP8556SQX-E08/NOPB WQFN BOOST OUTPUT VOLTAGE RANGE “PWM Only” – Recommended for systems without an I2C master. 23 mA 16 V to 34.5 V 6 25 mA 16 V to 30 V 5 20 mA 16 V to 34.5 V 6 20 mA 16 V to 25 V Can be programmed to any available. 25 mA Can be programmed to any available. 5 25 mA 16 V to 39 V 4 20 mA 12.88 V to 30 V 6 23 mA 16 V to 34.5 V 3 23 mA 7 V to 21 V 4 6 “PWM and I2C” - Recommended for systems with an I2C master. LP8556TME-E02/NOPB LP8556TMX-E02/NOPB LP8556TME-E03/NOPB LP8556TMX-E03/NOPB “PWM Only” – Recommended for systems without an I2C master. LP8556TME-E04/NOPB LP8556TMX-E04/NOPB DSBGA “Non-programmed” – This option is for evaluation purposes only. LP8556TME-E06/NOPB LP8556TMX-E06/NOPB LP8556TME-E07/NOPB LP8556TMX-E07/NOPB “PWM Only” – Recommended for systems without an I2C master. LP8556TME-E09/NOPB LP8556TMX-E09/NOPB LP8556TME-E11/NOPB LP8556TMX-E11/NOPB (1) MAXIMUM LED CURRENT 5 LP8556SQ-E09/NOPB LP8556SQE-E09/NOPB LP8556SQX-E09/NOPB LP8556TME-E05/NOPB LP8556TMX-E05/NOPB LED CHANNEL COUNT “PWM and I2C” - Recommended for systems with an I2C master. For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 3 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 6 Pin Configuration and Functions YFQ Package 20-Pin DSBGA Top View 1 A 2 SW B SW C VDD D VLDO E 3 GND SW SDA GND SW PWM VBOOST FSET ISET LED6 YFQ Package 20-Pin DSBGA Bottom View 4 3 2 1 SCL SDA GND SW SW A EN VDDIO PWM GND SW SW B LED3 FSET VBOOST VDD C LED2 GND ISET VLDO D LED1 LED4 LED5 LED6 E SCL EN VDDIO LED3 GND LED5 4 LED2 LED4 LED1 RTW Package 24-Pin WQFN Top View GND NC 8 23 ISET PWM 9 22 VDD 20 VBOOST 12 19 VLDO 15 16 17 18 LED6 11 LED5 GND LED4 FSET GND 21 LED3 10 LED2 GND 14 GND_SW SDA SCL 1 2 3 4 5 6 GND 24 7 EN / VDDIO ISET 23 8 NC VDD 22 9 PWM FSET 21 10 GND VBOOST 20 11 GND VLDO 19 12 LED1 Submit Documentation Feedback 18 17 16 15 14 13 LED2 24 LED3 7 13 GND_SW PIN 1 ID GND SW 1 LED4 SW 2 SW GND_SW 3 SW GND_SW 4 LED5 SDA 5 LED6 SCL 6 PIN 1 ID EN/VDDIO LED1 4 RTW Package 24-Pin WQFN Bottom View Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Pin Functions PIN NAME TYPE (1) DESCRIPTION DSBGA WQFN A1, B1 1, 2 SW A A connection to the drain terminal of the integrated power MOSFET. A2, B2 3, 4 GND_SW G A connection to the source terminal of the integrated power MOSFET. A3 5 SDA I/O I2C data input/output pin A4 6 SCL I I2C clock input pin B3 9 PWM I PWM dimming input. Supply a 75-Hz to 25-kHz PWM signal to control dimming. This pin must be connected to GND if unused. B4 7 EN / VDDIO P Dual-purpose pin serving both as a chip enable and as a power supply reference for PWM, SDA, and SCL inputs. Drive this pin with a logic gate capable of sourcing a minimum of 1 mA. C1 22 VDD P Device power supply pin. Provide 2.7-V to 20-V supply to this pin. This pin is an input of the internal LDO regulator. The output of the internal LDO is what powers the device. C2 20 VBOOST A Boost converter output pin. The internal feedback (FB) and overvoltage protection (OVP) circuitry monitors the voltage on this pin. Connect the converter output capacitor bank close to this pin. C3 21 FSET A A connection for setting the boost frequency and PWM output dimming frequency by using an external resistor. Connect a resistor, RFSET, between this pin and the ground reference (see Table 5). This pin may be left floating if PWM_FSET_EN = 0 AND BOOST_FSET_EN = 0 (see Table 10). C4 14 LED3 A LED driver - current sink terminal. If unused, it may be left floating. D1 19 VLDO P Internal LDO output pin. Connect a capacitor, CVLDO, between this pin and the ground reference. D2 23 ISET A A connection for the LED current set resistor. Connect a resistor, RISET, between this pin and the ground reference. This pin may be left floating if ISET_EN = 0 (see Table 10). D3 10, 11, 15, 24, DAP GND I Ground pin. D4 13 LED2 A LED driver - current sink pin. If unused, it may be left floating. E1 18 LED6 A LED driver - current sink pin. If unused, it may be left floating. E2 17 LED5 A LED driver - current sink pin. If unused, it may be left floating. E3 16 LED4 A LED driver - current sink pin. If unused, it may be left floating. E4 12 LED1 A LED driver - current sink pin. If unused, it may be left floating. — 8 NC — No Connect pin. (1) A: Analog Pin, G: Ground Pin, P: Power Pin, I: Digital Input Pin, I/O: Digital Input/Output Pin Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 5 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 7 Specifications 7.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) MIN MAX VDD –0.3 24 Voltage on Logic Pins (SCL, SDA, PWM) –0.3 6 Voltage on Analog Pins (VLDO, EN / VDDIO) –0.3 6 Voltage on Analog Pins (FSET, ISET) –0.3 VLDO + 0.3 V (LED1...LED6, SW, VBOOST) –0.3 UNIT V 50 Junction Temperature (TJ-MAX) (3) 125 °C Maximum Lead Temperature (Soldering) 260 °C 150 °C Storage temperature, Tstg (1) (2) (3) –65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability, see the Electrical Characteristics tables. If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/ Distributors for availability and specifications. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be de-rated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA × PD-MAX). 7.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001, DSBGA Package (1) ±2000 Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001, WQFN Package (1) ±1000 Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) ±500 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 7.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) (1) MIN MAX 2.7 20 V 1.62 3.6 V 0 48 V Junction temperature, TJ –30 125 °C Ambient temperature, TA –30 85 °C VDD EN / VDDIO V (LED1...LED6, SW, VBOOST) (1) 6 UNIT All voltages are with respect to the potential at the GND pins. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 7.4 Thermal Information LP8556 THERMAL METRIC (1) YFQ (DSBGA) RTW (WQFN) 20 PINS 24 PINS UNIT 66.2 35.0 °C/W RθJA Junction-to-ambient thermal resistance RθJC(top) Junction-to-case (top) thermal resistance 0.5 32.2 °C/W RθJB Junction-to-board thermal resistance 15.1 13.7 °C/W ψJT Junction-to-top characterization parameter 1.9 0.3 °C/W ψJB Junction-to-board characterization parameter 15.0 13.8 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance n/a 3.3 °C/W (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report (SPRA953). 7.5 Electrical Characteristics Unless otherwise specified: VDD = 12 V, EN / VDDIO = 1.8 V, TA = 25°C (1) (2) PARAMETER VDDIO Supply voltage for digital I/Os VDD Input voltage for the internal LDO Standby supply current IDD Normal mode supply current fOSC Internal oscillator frequency accuracy VLDO LDO output voltage TTSD Thermal shutdown threshold TTSD_hyst Thermal shutdown hysteresis (1) (2) (3) TEST CONDITIONS MIN TYP MAX 3.6 V 2.7 20 V 1.6 μA EN / VDDIO = 0 V, LDO disabled, –30°C ≤ TA ≤ 85°C LDO enabled, boost disabled 0.9 1.5 LDO enabled, boost enabled, no load 2.2 3.65 –4% 4% –30°C ≤ TA ≤ 85°C –7% 7% VDD ≥ 3.1 V 2.95 2.7 V ≤ VDD < 3.1 V See (3) UNIT 1.62 3.05 3.15 VDD – 0.05 mA V 150 °C 20 °C All voltages are with respect to the potential at the GND pins. Minimum (MIN) and Maximum (MAX) limits are verified by design, test, or statistical analysis. Typical numbers are for information only. Verified by design and not tested in production. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 7 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 7.6 Electrical Characteristics — Boost Converter over operating free-air temperature range (unless otherwise noted) (1) PARAMETER TEST CONDITIONS RDS_ON Switch ON resistance ISW = 0.5A VBOOST_MIN Boost minimum output voltage VBOOST_RANGE = 0 VBOOST_RANGE = 1 VBOOST_MAX ILOAD_MAX VOUT/VIN Boost maximum output voltage Maximum continuous output load current V =0 =0 =0 =0 19 24.0 28.0 32 21 25 30 34 22 27 32 37 V VBOOST_MAX = 010, VBOOST_MAX = 011, VBOOST_MAX = 100, VBOOST_MAX = 101, VBOOST_MAX = 110, VBOOST_MAX = 111, VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE =1 =1 =1 =1 =1 =1 17.9 22.8 27.8 32.7 37.2 41.8 21 25 30 34.5 39 43 23.1 27.2 31.5 36.6 40.8 44.2 V VIN = 3 V, VOUT = 18 V 220 VIN = 3 V, VOUT = 24 V 160 VIN = 3 V, VOUT = 30 V 120 Switching frequency VOVP Overvoltage protection voltage VBOOST_RANGE = 1 VUVLO VIN undervoltage lockout threshold VUVLO_hyst VUVLO hysteresis VUVLO[rising] VUVLO[falling] tPULSE Switch minimum pulse width No load mA 15 12 312 625 1250 kHz VBOOST + 1.6 V 2.5 5.2 V UVLO_EN = 1 UVLO_TH = 0, falling UVLO_TH = 1, falling See UVLO_TH = 0 50 UVLO_TH = 1 100 mV 50 (3) ns 8 IBOOST_LIM_2X = 0 SW pin current limit Ω 7 16 fSW = 1250 kHz Start-up time UNIT 0.19 fSW = 625 kHz Conversion ratio (2) MAX VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE VBOOST_RANGE fSW ISW_LIM TYP VBOOST_MAX = 100, VBOOST_MAX = 101, VBOOST_MAX = 110, VBOOST_MAX = 111, BOOST_FREQ = 00 BOOST_FREQ = 01 BOOST_FREQ = 10 tSTARTUP MIN (4) IBOOST_LIM_2X = 1 IBOOST_LIM IBOOST_LIM IBOOST_LIM IBOOST_LIM = 00 = 01 = 10 = 11 IBOOST_LIM = 00 IBOOST_LIM = 01 IBOOST_LIM = 10 0.66 0.88 1.12 1.35 0.9 1.2 1.5 1.8 ms 1.16 1.40 1.73 2.07 A 1.6 2.1 2.6 A ΔVSW / toff_on EN_DRV3 = 0 AND EN_DRV2 = 0 SW pin slew rate during OFF EN_DRV3 = 0 AND EN_DRV2 = 1 to ON transition EN_DRV3 = 1 AND EN_DRV2 = 1 3.7 5.3 7.5 V/ns ΔVSW / ton_off SW pin slew rate during ON to OFF transition EN_DRV3 = 0 AND EN_DRV2 = 0 EN_DRV3 = 0 AND EN_DRV2 = 1 EN_DRV3 = 1 AND EN_DRV2 = 1 1.9 4.4 4.8 V/ns ΔtON / tSW Peak-to-peak switch ON time deviation to SW period ratio (spread spectrum feature) SSCLK_EN = 1 1% (1) (2) (3) (4) 8 Minimum (MIN) and Maximum (MAX) limits are verified by design, test, or statistical analysis. Typical numbers are for information only. Verified by design and not tested in production. Start-up time is measured from the moment boost is activated until the VBOOST crosses 90% of its target value. 1.8 A is the maximum ISW_LIM supported with the DSBGA package. For applications requiring the ISW_LIM to be greater than 1.8 A and up to 2.6 A, WQFN package should be considered. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 7.7 Electrical Characteristics — LED Driver over operating free-air temperature range (unless otherwise noted) (1) PARAMETER TEST CONDITIONS MIN MAX 0.1 1 ILED_LEAKAGE Leakage current ILED_MAX Maximum sink current LED1...LED6 Output current set to 23 mA –3% 1% 3% ILED LED current accuracy (2) Output current set to 23 mA, –30°C ≤ TA ≤ 85°C –4% 1% 4% IMATCH Matching Output current set to 23 mA PWMDUTY fLED (2) (3) (4) LED PWM output pulse duty cycle (3) PWM output frequency VSAT (1) Outputs LED1...LED6, VOUT = 48 V TYP Saturation voltage (4) 50 UNIT µA mA 0.5% 100 Hz < fPWM ≤ 200 Hz 0.02% 100% 200 Hz < fPWM ≤ 500 Hz 0.02% 100% 500 Hz < fPWM ≤ 1 kHz 0.02% 100% 1 kHz < fPWM ≤ 2 kHz 0.04% 100% 2 kHz < fPWM ≤ 5 kHz 0.1% 100% 5 kHz < fPWM ≤ 10 kHz 0.2% 100% 10 kHz < fPWM ≤ 20 kHz 0.4% 100% 20 kHz < fPWM ≤ 30 kHz 0.6% 100% 30 kHz < fPWM ≤ 39 kHz 0.8% 100% PWM_FREQ = 1111 38.5 kHz Output current set to 23 mA 200 mV Minimum (MIN) and Maximum (MAX) limits are specified by design, test, or statistical analysis. Typical numbers are not verified, but do represent the most likely norm. Output Current Accuracy is the difference between the actual value of the output current and programmed value of this current. Matching is the maximum difference from the average. For the constant current sinks on the part (OUT1 to OUT6), the following are determined: the maximum output current (MAX), the minimum output current (MIN), and the average output current of all outputs (AVG). Two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN/AVG). The largest number of the two (worst case) is considered the matching figure. The typical specification provided is the most likely norm of the matching figure for all parts. Note that some manufacturers have different definitions in use. Verified by design and not tested in production. Saturation voltage is defined as the voltage when the LED current has dropped 10% from the value measured at 1 V. 7.8 Electrical Characteristics — PWM Interface (1) PARAMETER TEST CONDITIONS (2) MIN TYP 25 000 UNIT fPWM PWM frequency range tMIN_ON Minimum pulse ON time 1 tMIN_OFF Minimum pulse OFF time 1 tSTARTUP Turnon delay from standby to backlight on PWM input active, VDDIO pin transitions from 0 V to 1.8 V 10 tSTBY Turnoff delay PWM input low time for turnoff 50 ms PWMRES PWM input resolution ƒIN < 9 kHz 10 bits (1) (2) 75 MAX Hz μs ms Minimum (MIN) and Maximum (MAX) limits are specified by design, test, or statistical analysis. Typical numbers are for information only. Verified by design and not tested in production. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 9 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 7.9 Electrical Characteristics — Logic Interface PARAMETER (1) TEST CONDITIONS MIN TYP MAX UNIT LOGIC INPUTS (PWM, SDA, SCL) VIL Input low level –30°C ≤ TA ≤ 85°C VIH Input high level –30°C ≤ TA ≤ 85°C II Input current (VDDIO = 0 V or 3.6 V), (VI = 0 V or 3.6 V), –30°C ≤ TA ≤ 85°C 0.3 × VDDIO 0.7 × VDDIO V V –1 1 µA LOGIC OUTPUTS (SDA) IOUT = 3 mA (pull-up current) 0.3 VOL Output low level IOUT = 3 mA (pull-up current), –30°C ≤ TA ≤ 85°C 0.3 IL Output leakage current VOUT = 5 V, –30°C ≤ TA ≤ 85°C (1) 0.4 –1 1 V µA Minimum (MIN) and Maximum (MAX) limits are specified by design, test, or statistical analysis. Typical numbers are for information only. 7.10 I2C Serial Bus Timing Parameters (SDA, SCL) (1) MIN ƒSCL Clock frequency 1 Hold time (repeated) START condition 2 3 MAX UNIT 400 kHz 0.6 µs Clock low time 1.3 µs Clock high time 600 ns 4 Setup time for a repeated START condition 600 ns 5 Data hold time 50 ns 6 Data set-up time 7 Rise time of SDA and SCL 20 + 0.1Cb 300 ns 8 Fall time of SDA and SCL 15 + 0.1Cb 300 ns 9 Setup time for STOP condition 600 ns 10 Bus-free time between a STOP and a START condition 1.3 µs Cb Capacitive load parameter for each bus line load of 1 pF corresponds to 1 ns. 10 (1) 100 ns 200 ns Verified by design and not tested in production. Figure 1. I2C-Compatible Timing 10 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 7.11 Typical Characteristics Unless otherwise specified: VIN = 3.8 V, CVLDO = 10 μF, L1 = 4.7 μH, CIN = 2.2 μF, COUT = 4.7 μF, ƒSW = 1.25 MHz. VSW 20V/DIV EN/VDDIO 2V/DIV IL 500 mA/DIV VSW 20V/DIV IOUT 100 mA/DIV VBOOST 20V/DIV VBOOSTac 200 mV/DIV 4 ms/DIV 1 Ps/DIV Figure 2. Steady-State Operation Waveforms Figure 3. Start-Up Waveforms Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 11 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8 Detailed Description 8.1 Overview LP8556 is a white LED driver featuring an asynchronous boost converter and six high-precision current sinks that can be controlled by a PWM signal or an I2C master. The boost converter uses adaptive output voltage control for setting the optimal LED driver voltages as high as 43 V. This feature minimizes the power consumption by adjusting the voltage to the lowest sufficient level under all conditions. The converter can operate at three switching frequencies: 312, 625, and 1250 kHz pre-configured via EPROM or can be set through an external resistor. Programmable slew rate control and spread spectrum scheme minimize switching noise and improve EMI performance. LED current sinks can be set with the PWM dimming resolution of up to 15 bits. Proprietary adaptive dimming mode allows higher system power saving. In addition, phase shifted LED PWM dimming allows reduced audible noise and smaller boost output capacitors. The LP8556 device has a full set of safety features that ensure robust operation of the device and external components. The set consists of input undervoltage lockout, thermal shutdown, overcurrent protection, up to six levels of overvoltage protection, LED open, and short detection. 8.2 Functional Block Diagram VIN VOUT VDD SW VBOOST Boost Converter VLDO LDO Reference Voltage Thermal shutdown Switching Frequency 312, 625, 1250 kHz PWM Control BOOST_FREQ Oscillator Headroom Control POR Fault Detection (Open LED, OCP, OVP) LED Current Sinks LED1 PWM LED2 PWM Detector LED3 BRIGHTNESS EN/VDDIO LED4 CONTROL SDA LED5 2 12 SCL I C Slave FSET BOOST_FREQ PWM_FREQ LED6 ISET EPROM Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.3 Feature Description 8.3.1 Boost Converter 8.3.1.1 Boost Converter Operation The LP8556 boost DC-DC converter generates a 7-V to approximately 43-V of boost output voltage from a 2.7-V to 36-V boost input voltage. The boost output voltage minimum, maximum value and range can be set digitally by pre-configuring EPROM memory (VBOOST_RANGE, VBOOST, and VBOOST_MAX fields). The converter is a magnetic switching PWM mode DC-DC boost converter with a current limit. It uses CPM (current programmed mode) control, where the inductor current is measured and controlled with the feedback. During start-up, the soft-start function reduces the peak inductor current. The LP8556 has an internal 20-MHz oscillator which is used for clocking the boost. Figure 4 shows the boost block diagram. VBOOST SW Startup OVP Light Load R R R S R R Spread Spectrum OCP VREF Edge Rate Control + gm + VFB Osc/ ramp + - 6 Active Load Figure 4. LP8556 Boost Converter Block Diagram 8.3.1.2 Setting Boost Switching Frequency The LP8556 boost converter switching frequency can be set either by an external resistor (BOOST_FSET_EN = 1 selection), RFSET, or by pre-configuring EPROM memory with the choice of boost frequency (BOOST_FREQ field). Table 1 summarizes setting of the switching frequency. Note that the RFSET is shared for setting the PWM dimming frequency in addition to setting the boost switching frequency. Setting the boost switching frequency and PWM dimming frequency using an external resistor is separately shown in Table 5. Table 1. Configuring Boost Switching Frequency via EPROM RFSET [Ω] BOOST_FSET_EN BOOST_FREQ[1:0] ƒSW [kHz] don't care 0 00 312 don't care 0 01 625 don't care 0 10 1250 don't care 0 11 undefined 1 don't care See (1) See (1) (1) See Table 5. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 13 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.1.3 Output Voltage Control The LP8556 device supports two modes of controlling the boost output voltage: Adaptive Boost Voltage Control (see Adaptive Control) and Manual Boost Output Control (see Manual Control). 8.3.1.3.1 Adaptive Control LP8556 supports a mode of output voltage control called Adaptive Boost Control mode. In this mode, the voltage at the LED pins is periodically monitored by the control loop and adaptively adjusted to the optimum value based on the comparator thresholds set using LED DRIVER_HEADROOM, LED_COMP_HYST, BOOST_STEP_UP, BOOST_STEP_DOWN fields in the EPROM. Settings under LED DRIVER_HEADROOM along with LED_COMP_HYST fields determine optimum boost voltage for a given condition. Boost voltage is raised if the voltage measured at any of the LED strings falls below the threshold setting determined with LED DRIVER_HEADROOM field. Likewise, boost voltage is lowered if the voltage measured at any of the LED strings is above the combined setting determined under LED DRIVER_HEADROOM and LED_COMP_HYST fields. LED_COMP_HYST field serves to fine tune the headroom voltage for a given peak LED current. The boost voltage up/down step size can be controlled with the BOOST_STEP_UP and BOOST_STEP_DN fields. The initial boost voltage is configured with the VBOOST field. This field also sets the minimum boost voltage. The VBOOST_MAX field sets the maximum boost voltage. When an LED pin is open, the monitored voltage never has enough headroom, and the adaptive mode control loop keeps raising the boost voltage. The VBOOST_MAX field allows the boost voltage to be limited to stay under the voltage rating of the external components. NOTE Only LED strings that are enabled are monitored and PS_MODE field determines which LED strings are enabled. The adaptive mode is selected using ADAPTIVE bit set to 1 (CFGA EPROM Register) and is the recommended mode of boost control. VBOOST Driver headroom OUT1 string VF OUT6 string VF OUT5 string VF OUT4 string VF OUT3 string VF OUT2 string VF OUT1 string VF VBOOST Time Figure 5. Boost Adaptive Control Principle 8.3.1.3.2 Manual Control User can control the boost output voltage with the VBOOST EPROM field when adaptive mode is not used. Equation 1 shows the relationship between the boost output voltage and the VBOOST field. VBOOST = VBOOST_MIN + 0.42 × VBOOST[dec] (1) The expression is only valid when the calculated values are between the minimum boost output voltage and the maximum boost output voltage. The minimum boost output voltage is set with the VBOOST_RANGE field. The maximum boost output voltage is set with the VBOOST_MAX EPROM field. 14 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.3.1.4 EMI Reduction The LP8556 device features two EMI reduction schemes. The first scheme, Programmable Slew Rate Control, uses a combination of three drivers for boost switch. Enabling all three drivers allows boost switch on/off transition times to be the shortest. On the other hand, enabling just one driver allows boost switch on/off transition times to be the longest. The longer the transition times, the lower the switching noise on the SW pin. Note that the shortest transition times bring the best efficiency as the switching losses are the lowest. EN_DRV2 and EN_DRV3 bits in the EPROM determine the boost switch driver configuration. Refer to the SW pin slew rate parameter listed under Electrical Characteristics — Boost Converter for the slew rate options. The second EMI reduction scheme is the spread spectrum. This scheme deliberately spreads the frequency content of the boost switching waveform, which inherently has a narrow bandwidth, makes the bandwidth of the switching waveform wider, and ultimately reduces its EMI spectral density. Duty cycle D = 1 - VIN / VOUT tSW = 1/fSW Slew rate control, programmable Spread spectrum scheme, programmable pseudo random duty cycle changes minimize EMI Figure 6. Principles of EMI Reduction Scheme 8.3.2 Brightness Control LP8556 enables various methods of brightness control. The brightness can be controlled using an external PWM signal or the Brightness register accessible by users via an I2C interface or both. How these two input sources are selected and combined is set by the BRT_MODE EPROM bits and described in BRT_MODE = 00 through BRT_MODE = 11, Figure 7, and Table 2. The LP8556 can also be preconfigured via EPROM memory to allow direct and unaltered brightness control by an external PWM signal. This mode of operation is obtained by setting PWM_DIRECT EPROM bit to 1 (CFG5[7] = 1). 8.3.2.1 BRT_MODE = 00 With BRT_MODE = 00, the LED output is controlled by the PWM input duty cycle. The PWM detector block measures the duty cycle at the PWM pin and uses this 16-bit value to generate an internal to the device PWM data. Before the output is generated, the PWM data goes through the PWM curve-shaper block. Then, the data goes into the adaptive dimming function which determines the range of the PWM and Current control as described in Output Dimming Schemes. The outcome of the adaptive dimming function is 12-bit current and/or up to 6 PWM output signals. The current is then passed through the non-linear compensation block while the output PWM signals are channeled through the dither block. 8.3.2.2 BRT_MODE = 01 With BRT_MODE = 01, the PWM output is controlled by the PWM input duty cycle and the Brightness register. The PWM detector block measures the duty cycle at the PWM pin and uses this 16-bit value to generate the PWM data. Before the output is generated, the PWM data is first multiplied with BRT[7:0] register, then it goes through the PWM Curve Shaper block. Then, the data goes into the Adaptive Dimming function which determines the range of the PWM and Current control as described in Output Dimming Schemes. The outcome of the Adaptive Dimming function is 12-bit current and/or up to 6 PWM output signals. The current is then passed through the non-linear compensation block while the output PWM signals are channeled through the Dither block. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 15 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.2.3 BRT_MODE = 10 With BRT_MODE = 10, the PWM output is controlled only by the Brightness register. From BRT[7:0] register, the data goes through the PWM Curve Shaper block. Then, the data goes into the Adaptive Dimming function which determines the range of the PWM and Current control as described in Output Dimming Schemes. The outcome of the Adaptive Dimming function is 12-bit Current and / or up to 6 PWM output signals. The current is then passed through the non-linear compensation block while the output PWM signals are channeled through the Dither block. 8.3.2.4 BRT_MODE = 11 With BRT_MODE = 11, the PWM control signal path is similar to the path when BRT_MODE = 01 except that the PWM input signal is multiplied with BRT[7:0] data after the Curve-Shaper block. Table 2. Brightness Control Methods Truth Table 16 PWM_DIRECT BRT_MODE [1:0] 0 00 External PWM signal BRIGHTNESS CONTROL SOURCE 0 01 External PWM signal and Brightness Register (multiplied before Curve Shaper) 0 10 Brightness Register 0 11 External PWM signal and Brightness Register (multiplied after Curve Shaper) 1 don't care External PWM signal Submit Documentation Feedback OUTPUT ILED FORM Adaptive. See Output Dimming Schemes Same as the external PWM input Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Current_Max [2:0] BRT_MODE = 00 Current [11:0] Non-linear Compensation PWM Input PWM Detector Temp Curve Limiter Shaper CURRENT Adaptive Dimming Dither PWM Gen PWM PWM_TO_I_THRESHOLD [3:0] Current_Max [2:0] BRT_MODE = 01 Current [11:0] Brightness Non-linear Compensation PWM Input PWM Detector Temp Curve Limiter Shaper CURRENT Adaptive Dimming Dither PWM Gen PWM PWM_TO_I_THRESHOLD [3:0] Current_Max [2:0] BRT_MODE = 10 Current [11:0] Non-linear Compensation Brightness Temp Curve Limiter Shaper CURRENT Adaptive Dimming Dither PWM Gen PWM PWM_TO_I_THRESHOLD [3:0] Current_Max [2:0] BRT_MODE = 11 Current [11:0] Non-linear Compensation Brightness Temp Curve Limiter Shaper Dither PWM Input CURRENT Adaptive Dimming PWM Gen PWM PWM Detector PWM_TO_I_THRESHOLD [3:0] Figure 7. Brightness Control Signal Path Block Diagrams Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 17 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.2.5 Output Dimming Schemes The LP8556 device supports three types of output dimming control methods: PWM Control, Pure Current Control and Adaptive Dimming (Hybrid PWM and Current) Control. 8.3.2.5.1 PWM Control PWM control is the traditional way of controlling the brightness using PWM of the outputs with the same LED current across the entire brightness range. Brightness control is achieved by varying the duty cycle proportional to the input PWM. PWM frequency is set either using an external set fesistor (RFSET) or using the PWM_FREQ EPROM field. The maximum LED current is set by using an external set Resistor (RISET), CURRENT, and CURRENT_MAX EPROM bits. PWM frequency can also be set by simply using the CURRENT and CURRENT_MAX EPROM bits. NOTE The output PWM signal is de-coupled and generated independent of the input PWM signal eliminating display flicker issues and allowing better noise immunity. PWM CONTROL (PWM_TO_I_THRESHOLD = 1111b) Max current is set with CURRENT and CURRENT_MAX EPROM bits or CURRENT and CURRENT_MAX EPROM bits and RISET resistor LED CURRENT 100% 25% 100% 50% BRIGHTNESS Figure 8. PWM Only Output Dimming Scheme 8.3.2.5.2 Pure Current Control In Pure Current Control mode, brightness control is achieved by changing the LED current proportionately from maximum value to a minimum value across the entire brightness range. Like in PWM Control mode, the maximum LED current is set by using an external set Resistor (RISET), CURRENT, and CURRENT_MAX EPROM bits. The maximum LED current can also be set by just using the CURRENT and CURRENT_MAX EPROM bits. Current resolution in this mode is 12 bits. PURE CURRENT CONTROL (PWM_TO_I_THRESHOLD = 0000b) Max current is set with CURRENT and CURRENT_MAX EPROM bits LED CURRENT 100% or CURRENT and CURRENT_MAX EPROM bits and RISET resistor 50% 25% 25% 50% 100% BRIGHTNESS Figure 9. Pure Current or Analog Output Dimming Scheme 18 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.3.2.5.3 Adaptive Control Adaptive dimming control combines PWM Control and Pure Current Control dimming methods. With the adaptive dimming, it is possible to achieve better optical efficiency from the LEDs compared to pure PWM control while still achieving smooth and accurate control at low brightness levels. Current resolution in this mode is 12 bits. Switch point from Current to PWM control can be set with the PWM_TO_I_THRESHOLD EPROM field from 0% to 100% of the brightness range to get good compromise between good matching of the LEDs brightness/white point at low brightness and good optical efficiency. PWM frequency is set either using an external set Resistor (RFSET) or using the PWM_FREQ EPROM bits. The maximum LED current is set either by using an external set Resistor (RISET), CURRENT, and CURRENT_MAX EPROM bits. Or the maximum LED current may be set using the CURRENT and CURRENT_MAX EPROM bits. PWM & CURRENT CONTROL with Switch Point at 25% of ILED_MAX (PWM_TO_I_THRESHOLD = 0111b) PWM CONTROL CURRENT CONTROL LED CURRENT 100% 50% 25% Max current is set with CURRENT and CURRENT_MAX EPROM bits or CURRENT and CURRENT_MAX EPROM bits and RISET resistor 25% 50% 100% BRIGHTNESS Figure 10. Adaptive Output Dimming Scheme 8.3.2.6 Setting Full-Scale LED Current The maximum or full-scale LED current is set either using an external set Resistor (RISET), CURRENT, and CURRENT_MAX EPROM bits or just by using the CURRENT and CURRENT_MAX EPROM bits. Table 3 summarizes setting of the full-scale LED current. Table 3. Setting Full-Scale LED Current (1) RISET [Ω] ISET_EN CURRENT_MAX CURRENT[11:0] don't care 0 000 FFFh FULL-SCALE ILED [mA] 5 don't care 0 001 FFFh 10 don't care 0 010 FFFh 15 don't care 0 011 FFFh 20 don't care 0 100 FFFh 23 don't care 0 101 FFFh 25 don't care 0 110 FFFh 30 don't care 0 111 FFFh 50 don't care 0 000 - 111 001h - FFFh See (1) 24k 1 000 FFFh 5 24k 1 001 FFFh 10 24k 1 010 FFFh 15 24k 1 011 FFFh 20 24k 1 100 FFFh 23 24k 1 101 FFFh 25 24k 1 110 FFFh 30 24k 1 111 FFFh 50 12k - 100k 1 000 - 111 001h - FFFh See (1) See CFG0. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 19 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.2.7 Setting PWM Dimming Frequency LP8556 PWM dimming frequency can be set by an external resistor, RFSET, or by pre-configuring EPROM Memory (CFG5 register, PWM_FREQ[3:0] bits). Table 4 summarizes setting of the PWM dimming frequency. Note that . NOTE The RFSET is shared for setting the boost switching frequency, too. Setting the boost switching frequency and PWM dimming frequency using an external resistor is shown in Table 5. Table 4. Configuring PWM Dimming Frequency via EPROM RFSET [kΩ] PWM_FSET_EN don't care See (1) (1) 20 0 1 PWM_FREQ[3:0] ƒPWM [Hz] (Resolution) 0000 4808 (11-bit) 0001 6010 (10-bit) 0010 7212 (10-bit) 0011 8414 (10-bit) 0100 9616 (10-bit) 0101 12020 (9-bit) 0110 13222 (9-bit) 0111 14424 (9-bit) 1000 15626 (9-bit) 1001 16828 (9-bit) 1010 18030 (9-bit) 1011 19232 ((9-bit) 1100 24040 (8-bit) 1101 28848 (8-bit) 1110 33656 (8-bit) 1111 38464 (8-bit) don't care See (1) See Table 5. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Table 5. Setting Switching and PWM Dimming Frequency With an External Resistor RFSET [Ω] (Tolerance) ƒSW [kHz] ƒPWM [Hz] (Resolution) Floating or FSET pin pulled HIGH 1250 9616 (10-bit) 470k - 1M (±5%) 312 2402 (12-bit) 300k, 330k (±5%) 312 4808 (11-bit) 200k (±5%) 312 6010 (10-bit) 147k, 150k, 154k, 158k (±1%) 312 9616 (10-bit) 121k (±1%) 312 12020 (9-bit) 100k (±1%) 312 14424 (9-bit) 86.6k (±1%) 312 16828 (9-bit) 75.0k (±1%) 312 19232 (9-bit) 63.4k (±1%) 625 2402 (12-bit) 52.3k, 53.6k (±1%) 625 4808 (11-bit) 44.2k, 45.3k (±1%) 625 6010 (10-bit) 39.2k (±1%) 625 9616 (10-bit) 34.0k (±1%) 625 12020 (9-bit) 30.1k (±1%) 625 14424 (9-bit) 26.1k (±1%) 625 16828 (9-bit) 23.2k (±1%) 625 19232 (9-bit) 20.5k (±1%) 1250 2402 (12-bit) 18.7k (±1%) 1250 4808 (11-bit) 16.5k (±1%) 1250 6010 (10-bit) 14.7k (±1%) 1250 9616 (10-bit) 13.0k (±1%) 1250 12020 (9-bit) 11.8k (±1%) 1250 14424 (9-bit) 10.7k (±1%) 1250 16828 (9-bit) 9.76k (±1%) 1250 19232 (9-bit) FSET pin shorted to GND 1250 Same as PWM input Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 21 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.2.8 Phase Shift PWM Scheme Phase shift PWM scheme allows delaying the time when each LED driver is active. When the LED drivers are not activated simultaneously, the peak load current from the boost output is greatly decreased. This reduces the ripple seen on the boost output and allows smaller output capacitors. Reduced ripple also reduces the output ceramic capacitor audible ringing. PSPWM scheme also increases the load frequency seen on the boost output six times and therefore transfers the possible audible noise to the frequencies outside of the audible range. Description of the PSPWM mode is seen inTable 6. PSPWM mode is set with bits. Table 6. LED String Configuration PS_MODE[2:0] WAVEFORMS Phase Delay 60 degrees CONNECTION Cycle Time 1/(fPWM) VBOOST LED1 LED2 000 LED3 1 2 3 4 5 6 5 6 LED4 LED5 LED6 6 LED strings with 60 degree phase shift. One driver for each LED string. Phase Delay 72 degrees Cycle Time 1/(fPWM) VBOOST LED1 LED2 001 1 LED3 2 3 4 LED4 LED5 5 LED strings with 72 degree phase shift. One driver for each LED string. (Driver #6 not used). 22 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Table 6. LED String Configuration (continued) PS_MODE[2:0] WAVEFORMS Phase Delay 90 degrees CONNECTION Cycle Time 1/(fPWM) VBOOST LED1 010 LED2 1 2 3 4 5 6 5 6 5 6 LED3 LED4 4 LED strings with 90 degree phase shift. One driver for each LED string. (Drivers #5 and #6 not used). VBOOST Phase Delay 120 degrees Cycle Time 1/(fPWM) LED1 011 LED2 1 2 3 4 LED3 3 LED strings with 120 degree phase shift. One driver for each LED string. (Drivers #4, #5 and #6 not used). VBOOST Phase Delay 180 degrees 100 Cycle Time 1/(fPWM) LED1 1 2 3 4 LED2 2 LED strings with 180 degree phase shift. One driver for each LED string. (Drivers #3, #4, #5 and #6 not used). Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 23 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Table 6. LED String Configuration (continued) PS_MODE[2:0] WAVEFORMS Phase Delay 120 degrees CONNECTION Cycle Time 1/(fPWM) VBOOST LED1 LED2 101 LED3 1 2 3 4 5 6 5 6 LED4 LED5 LED6 3 LED strings with 120 degree phase shift. Two drivers for each LED string. (Drivers 1&2, 3&4 and 5&6 are tied and with the same phase). Phase Delay 180 degrees Cycle Time 1/(fPWM) VBOOST LED1 LED2 110 LED3 1 2 3 4 LED4 LED5 LED6 2 LED strings with 180 degree phase shift. Three divers for each LED string. (Drivers 1&2&3 and 4&5&6 are tied and with the same phase). 24 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Table 6. LED String Configuration (continued) PS_MODE[2:0] WAVEFORMS Phase Delay 0 degrees CONNECTION Cycle Time 1/(fPWM) VBOOST LED1 LED2 111 LED3 1 2 3 4 5 6 LED4 LED5 LED6 1 LED string driven by all six drivers. (All drivers are tied and with the same phase). Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 25 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.3.2.9 Slope and Advanced Slope Transition time between two brightness values can be programmed with EPROM bits from 0 to 500 ms. Same slope time is used for sloping up and down. With advanced slope the brightness changes can be made more pleasing to a human eye. Brightness (PWM) Sloper Input Brightness (PWM) PWM Output Time Normal slope Advanced slope Time Slope Time Figure 11. Sloper Operation 8.3.2.10 Dithering Special dithering scheme can be used during brightness changes and in steady state condition. It allows increased resolution and smaller average steps size during brightness changes. Dithering can be programmed with EPROM bits from 0 to 3 bits. EPROM bit sets whether the dithering is used also in steady state or only during slopes. Example below is for 1-bit dithering. For 3-bit dithering, every 8th pulse is made 1 LSB longer to increase the average value by 1/8th. PWM value 510 (10-bit) +1 LSB PWM value 510 1/2 (10-bit) PWM value 511 (10-bit) Figure 12. Example of the Dithering, 1-bit Dither, 10-bit Resolution 26 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.3.3 Fault Detection LP8556 has fault detection for LED open and short conditions, UVLO, overcurrent, and thermal shutdown. The cause for the fault can be read from status register. Reading the fault register also resets the fault. 8.3.3.1 LED Fault Detection With LED fault detection, the voltages across the LED drivers are constantly monitored. Shorted or open LED strings are detected. 8.3.3.1.1 Open Detect The logic uses the LOW comparators and the requested boost voltage to detect the OPEN condition. If the logic is asking the boost for the maximum allowed voltage and a LOW comparator is asserted, then the OPEN bit is set in the STATUS register (ADDR = 02h). In normal operation, the adaptive headroom control loop raises the requested boost voltage when the LOW comparator is asserted. If it has raised it as high as it can and an LED string still needs more voltage, then it is assumed to be disconnected from the boost voltage (open or grounded). The actual boost voltage is not part of the OPEN condition decision; only the requested boost voltage and the LOW comparators. 8.3.3.1.2 Short Detect The logic uses all three comparators (HIGH, MID and LOW) to detect the SHORT condition. When the MID and LOW comparators are de-asserted, the headroom control loop considers that string to be optimized - enough headroom, but not excessive. If at least one LED string is optimized and at least one other LED string has its HIGH comparator asserted, then the SHORT condition is detected. It is important to note that the SHORT condition requires at least two strings for detection: one in the optimized headroom zone (LOW/MID/HIGH comparators all de-asserted) and one in the excessive headroom zone (HIGH comparator asserted). Fault is cleared by reading the fault register. 8.3.3.2 Undervoltage Detection The LP8556 device has detection for too-low VIN voltage. Threshold level for the voltage is set with EPROM register bits as shown in Table 7. Table 7. UVLO Truth Table UVLO_EN UVLO_TH THRESHOLD (V) 0 don't care OFF 1 0 2.5 1 1 5.2 When undervoltage is detected the LED outputs and the boost shuts down, and the corresponding fault bit is set in the fault register. The LEDs and the boost start again when the voltage has increased above the threshold level. Hysteresis is implemented to threshold level to avoid continuous triggering of fault when threshold is reached. Fault is cleared by setting the EN / VDDIO pin low or by reading the fault register. 8.3.3.3 Overcurrent Protection LP8556 has detection for too-high loading on the boost converter. When overcurrent fault is detected, the boost shuts down and the corresponding fault bit is set in the fault register. The boost starts again when the current has dropped below the OCP threshold. Fault is cleared by reading the fault register. 8.3.3.4 Thermal Shutdown If the LP8556 reaches thermal shutdown temperature (150°C) the LED outputs and boost shut down to protect it from damage. The device re-activates when temperature drops below 130°C. Fault is cleared by reading the fault register. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 27 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.4 Device Functional Modes 8.4.1 Shutdown Mode The device is in shutdown mode when the EN/VDDIO input is low. Current consumption in this mode from VDD pin is < 1.6 µA. 8.4.2 Active Mode In active mode the backlight is enabled either with setting the ON register bit high (BRTMODE = 0 1, 10, 11) or by activating PWM input (BRTMODE=00). The powers supplying the VDD and EN/VDDIO pins must be present. Brightness is controlled with I2C writes to brightness registers or by changing PWM input duty cycle (operation without I2C control). Configuration registers are not accessible in Active mode to prevent damage to the device by accidental writes. Current consumption from VDD pin this mode is typically 2.2 mA when boost is enabled and LEDs are not drawing any current. 8.5 Programming 8.5.1 I2C-Compatible Serial Bus Interface 8.5.1.1 Interface Bus Overview The I2C-compatible synchronous serial interface provides access to the programmable functions and registers on the device. This protocol uses a two-wire interface for bidirectional communications between the ICs connected to the bus. The two interface lines are the Serial Data Line (SDA) and the Serial Clock Line (SCL). These lines must be connected to a positive supply via a pull-up resistor and remain HIGH even when the bus is idle. Every device on the bus is assigned a unique address and acts as either a Master or a Slave depending on whether it generates or receives the SCL. The LP8556 can operate as an I2C slave. 8.5.1.2 Data Transactions One data bit is transferred during each clock pulse. Data is sampled during the high state of the serial clock SCL. Consequently, throughout the clock’s high period, the data should remain stable. Any changes on the SDA line during the high state of the SCL and in the middle of a transaction, aborts the current transaction. New data should be sent during the low SCL state. This protocol permits a single data line to transfer both command/control information and data using the synchronous serial clock. SDA SCL Data Line Stable: Data Valid Change of Data Allowed Figure 13. Bit Transfer Each data transaction is composed of a Start Condition, a number of byte transfers (set by the software) and a Stop Condition to terminate the transaction. Every byte written to the SDA bus must be 8 bits long and is transferred with the most significant bit first. After each byte, an Acknowledge signal must follow. The following sections provide further details of this process. 28 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Programming (continued) Data Output by Transmitter Transmitter Stays Off the Bus During the Acknowledgment Clock Data Output by Receiver Acknowledgment Signal From Receiver SCL 1 2 3-6 7 8 9 S Start Condition Figure 14. Start and Stop The Master device on the bus always generates the Start and Stop Conditions (control codes). After a Start Condition is generated, the bus is considered busy and it retains this status until a certain time after a Stop Condition is generated. A high-to-low transition of the data line (SDA) while the clock (SCL) is high indicates a Start Condition. A low-to-high transition of the SDA line while the SCL is high indicates a Stop Condition. SDA SCL S P Start Condition Stop Condition Figure 15. Start and Stop Conditions In addition to the first Start Condition, a repeated Start Condition can be generated in the middle of a transaction. This allows another device to be accessed, or a register read cycle. 8.5.1.3 Acknowledge Cycle The Acknowledge Cycle consists of two signals: the acknowledge clock pulse the master sends with each byte transferred, and the acknowledge signal sent by the receiving device. The master generates the acknowledge clock pulse on the ninth clock pulse of the byte transfer. The transmitter releases the SDA line (permits it to go high) to allow the receiver to send the acknowledge signal. The receiver must pull down the SDA line during the acknowledge clock pulse and ensure that SDA remains low during the high period of the clock pulse, thus signaling the correct reception of the last data byte and its readiness to receive the next byte. 8.5.1.4 Acknowledge After Every Byte Rule The master generates an acknowledge clock pulse after each byte transfer. The receiver sends an acknowledge signal after every byte received. There is one exception to the acknowledge after every byte rule. When the master is the receiver, it must indicate to the transmitter an end of data by not-acknowledging (“negative acknowledge”) the last byte clocked out of the slave. This negative acknowledge still includes the acknowledge clock pulse (generated by the master), but the SDA line is not pulled down. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 29 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Programming (continued) 8.5.1.5 Addressing Transfer Formats Each device on the bus has a unique slave address. The LP8556 operates as a slave device with 7-bit address combined with data direction bit. Slave address is 2Ch as 7-bit or 58h for write and 59h for read in 8-bit format. Before any data is transmitted, the master transmits the slave I.D. The slave device should send an acknowledge signal on the SDA line, once it recognizes its address. The slave address is the first seven bits after a Start Condition. The direction of the data transfer (R/W) depends on the bit sent after the slave address — the 8th bit. When the slave address is sent, each device in the system compares this slave address with its own. If there is a match, the device considers itself addressed and sends an acknowledge signal. Depending upon the state of the R/W bit (1:read, 0:write), the device acts as a transmitter or a receiver. MSB LSB ADR6 Bit7 ADR5 bit6 ADR4 bit5 ADR3 bit4 ADR2 bit3 ADR1 bit2 ADR0 bit1 x x x x x x x R/W bit0 2 I C SLAVE address (chip address) Figure 16. I2C Chip Address (0x2C) 8.5.1.6 Control Register Write Cycle • Master device generates start condition. • Master device sends slave address (7 bits) and the data direction bit (r/w = 0). • Slave device sends acknowledge signal if the slave address is correct. • Master sends control register address (8 bits). • Slave sends acknowledge signal. • Master sends data byte to be written to the addressed register. • Slave sends acknowledge signal. • If master sends further data bytes the control register address is incremented by one after acknowledge signal. • Write cycle ends when the master creates stop condition. 8.5.1.7 Control Register Read Cycle • Master device generates a start condition. • Master device sends slave address (7 bits) and the data direction bit (r/w = 0). • Slave device sends acknowledge signal if the slave address is correct. • Master sends control register address (8 bits). • Slave sends acknowledge signal. • Master device generates repeated start condition. • Master sends the slave address (7 bits) and the data direction bit (r/w = 1). • Slave sends acknowledge signal if the slave address is correct. • Slave sends data byte from addressed register. • If the master device sends acknowledge signal, the control register address is incremented by one. Slave device sends data byte from addressed register. • Read cycle ends when the master does not generate acknowledge signal after data byte and generates stop condition. 30 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Programming (continued) Table 8. Data Read and Write Cycles ADDRESS MODE Data Read [Ack] [Ack] [Ack] [Register Data] … additional reads from subsequent register address possible Data Write [Ack] [Ack] [Ack] … additional writes to subsequent register address possible Data from master [ ] Data from slave 8.5.1.8 Register Read and Write Detail S Slave Address (7 bits) '0' A Control Register Add. (8 bits) Register Data (8 bits) A A P Data transfered, byte + Ack R/W From Slave to Master A - ACKNOWLEDGE (SDA Low) S - START CONDITION From Master to Slave P - STOP CONDITION Figure 17. Register Write Format S Slave Address (7 bits) '0' A Control Register Add. (8 bits) A Sr Slave Address (7 bits) R/W '1' A R/W Data- Data (8 bits) A/ P NA Data transfered, byte + Ack/NAck Direction of the transfer will change at this point From Slave to Master A - ACKNOWLEDGE (SDA Low) NA - ACKNOWLEDGE (SDA High) From Master to Slave S - START CONDITION Sr - REPEATED START CONDITION P - STOP CONDITION Figure 18. Register Read Format Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 31 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6 Register Maps Table 9. Register Map ADDR REGISTER D7 D6 00H Brightness Control D5 D4 D3 D2 D1 D0 RESET 01H Device Control FAST 02H Status OPEN 04H Direct Control LED 0000 0000 16H LED Enable LED_EN 0011 1111 BRT[7:0] 0000 0000 BRT_MODE SHORT VREF_OK VBOOST_OK OVP OCP TSD BL_CTL 0000 0000 UVLO 0000 0000 Table 10. EPROM Memory Map 32 ADDR REGISTER D7 98H CFG98 IBOOST_LIM_2X 9EH CFG9E A0H CFG0 A1H CFG1 A2H CFG2 A3H CFG3 A4H CFG4 A5H CFG5 A6H CFG6 BOOST_FREQ A7H CFG7 RESERVED A8H CFG8 RESERVED A9H CFG9 AAH CFGA ABH CFGB ACH CFGC ADH CFGD AEH CFGE AFH CFGF D6 D5 D4 D3 D2 D1 RESERVED RESERVED VBOOST_RANGE D0 RESERVED RESERVED HEADROOM_OFFSET CURRENT LSB PDET_STDBY CURRENT_MAX RESERVED UVLO_EN RESERVED CURRENT MSB UVLO_TH ISET_EN SLOPE PWM_DIRECT BOOST_FSET_EN FILTER PWM_TO_I_THRESHOLD RESERVED PWM_FSET_EN PWM_INPUT_HYSTERESIS STEADY_DITHE R PS_MODE DITHER PWM_FREQ VBOOST EN_DRV3 EN_DRV2 RESERVED RESERVED VBOOST_MAX SSCLK_EN BL_ON RESERVE D JUMP_EN RESERVED IBOOST_LIM RESERVED RESERVED JUMP_THRESHOLD JUMP_VOLTAGE ADAPTIVE DRIVER_HEADROOM RESERVED RESERVED RESERVED RESERVED STEP_UP STEP_DN LED_FAULT_TH LED_COMP_HYST REVISION Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.1 Register Bit Explanations 8.6.1.1 Brightness Control Address 00h Reset value 0000 0000b BRIGHTNESS CONTROL REGISTER 7 6 5 4 3 2 1 0 BRT[7:0] NAME BIT ACCESS BRT 7:0 R/W DESCRIPTION Backlight PWM 8-bit linear control. 8.6.1.2 Device Control Address 01h Reset value 0000 0000b DEVICE CONTROL REGISTER 7 6 5 4 3 FAST 2 1 BRT_MODE[1:0] NAME BIT FAST 7 BRT_MODE 2:1 ACCESS 0 BL_CTL DESCRIPTION Skip refresh of trim and configuration registers from EPROMs when exiting the low power STANDBY mode. 0 = read EPROMs before returning to the ACTIVE state 1 = only read EPROMs once on initial power-up. R/W Brightness source mode Figure 7 00b = PWM input only 01b = PWM input and Brightness register (combined before shaper block) 10b = Brightness register only 11b = PWM input and Brightness register (combined after shaper block) BL_CTL 0 R/W Enable backlight when Brightness Register is used to control brightness (BRT_MODE = 10). 0 = Backlight disabled and chip turned off 1 = Backlight enabled and chip turned on This bit has no effect when PWM pin control is selected for brightness control (BRT_MODE = 00). In this mode the state of PWM pin enable or disables the chip. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 33 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.1.3 Status Address 02h Reset value 0000 0000b FAULT REGISTER 7 6 5 4 3 2 1 0 OPEN SHORT VREF_OK VBOOST_OK OVP OCP TSD UVLO NAME BIT ACCESS OPEN 7 R DESCRIPTION LED open fault detection 0 = No fault 1 = LED open fault detected. The value is not latched. SHORT 6 R LED short fault detection 0 = No fault 1 = LED short fault detected. The value is not latched. VREF_OK 5 R Internal VREF node monitor status 1 = VREF voltage is OK. VBOOST_OK 4 R Boost output voltage monitor status 0 = Boost output voltage has not reached its target (VBOOST < Vtarget – 2.5V) 1 = Boost output voltage is OK. The value is not latched. OVP 3 R Overvoltage protection 0 = No fault 1 = Overvoltage condition occurred. Fault is cleared by reading the register 02h. OCP 2 R Over current protection 0 = No fault 1 = Overcurrent condition occurred. Fault bit is cleared by reading this register. TSD 1 R Thermal shutdown 0 = No fault 1 = Thermal fault generated, 150°C reached. Boost converter and LED outputs are disabled until the temperature has dropped down to 130°C. Fault is cleared by reading this register. UVLO 0 R Undervoltage detection 0 = No fault 1 = Undervoltage detected on the VDD pin. Boost converter and LED outputs are disabled until VDD voltage is above the UVLO threshold voltage. Threshold voltage is set with EPROM bits. Fault is cleared by reading this register. 8.6.1.4 Direct Control Address 04h Reset value 0000 0000b DIRECT CONTROL REGISTER 7 6 5 4 3 2 1 0 OUT[5:0] NAME BIT ACCESS OUT 5:0 R/W DESCRIPTION Direct control of the LED outputs 0 = Normal operation. LED output are controlled with the adaptive dimming block 1 = LED output is forced to 100% PWM. 34 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.1.5 LED String Enable Address 16h Reset value 0011 1111b TEMP LSB REGISTER 7 6 5 4 3 2 1 0 LED_EN[5:0] NAME BIT ACCESS LED_EN 5:0 R/W DESCRIPTION Bits 5:0 correspond to LED Strings 6:1 respectively. Bit value 1 = LED String Enabled Bit value 0 = LED String Disabled Note: To disable string(s), it is recommended to disable higher order string(s). For example, for 5-string configuration, disable 6th String. For 4-string configuration, disable 6th and 5th string. These bits are ANDed with the internal LED enable bits that are generated with the PS_MODE logic. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 35 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.2 EPROM Bit Explanations 8.6.2.1 LP8556TM (DSBGA) Configurations and Pre-Configured EPROM Settings ADDRESS (1) LP8556-E02 LP8556-E03 LP8556-E04 LP8556-E05 (1) 98h[7] 0b 0b 0b 0b 9Eh 22h 24h 24h 22h A0h FFh FFh FFh A1h 5Fh BFh 3Fh A2h 20h 28h 2Fh A3h 5Eh 5Eh 5Eh A4h 72h 72h 72h A5h 04h 14h 04h A6h 80h 80h 80h A7h F7h F7h F7h A9h 80h A0h 60h AAh 0Fh 0Fh 0Fh ABh 00h 00h 00h ACh 00h 00h 00h ADh 00h 00h 00h AEh 0Fh 0Fh 0Fh AFh 05h 03h 03h LP8556-E05 is a device option with un-configured EPROM settings. This option is for users that desire programming the device by themselves. Bits 98h[7] and 9Eh[5] are always pre-configured. 8.6.2.2 LP8556TM (DSBGA) Configurations and Pre-configured EPROM Settings Continued ADDRESS 36 LP8556-E06 LP8556-E07 LP8556-E09 LP8556-E11 98h[7] 0b 0b 0b 0b 9Eh 22h 04h 22h 02h A0h FFh FFh FFh FFh A1h DBh BFh CFh 4Fh A2h 2Fh 0Dh 2Fh 20h A3h 02h 02h 02h 03h A4h 72h 72h 72h 12h A5h 14h 20h 04h 3Ch A6h 40h 4Eh 80h 40h A7h F7h F6h F7h F4h A9h DBh C0h A0h 80h AAh 0Fh 0Fh 0Fh 0Fh ABh 00h 00h 00h 00h ACh 00h 00h 00h 00h ADh 00h 00h 00h 00h AEh 0Fh 0Fh 0Eh 0Fh AFh 05h 03h 05h 01h Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.2.3 LP8556SQ (WQFN) Configurations and Pre-configured EPROM Settings ADDRESS LP8556-E00 LP8556-E08 LP8556-E09 98h[7] 1b 1b 1b 9Eh 22h 22h 22h A0h FFh FFh FFh A1h CFh CFh CFh A2h 2Fh 2Fh 2Fh A3h 5Eh 5Eh 02h A4h 72h 72h 72h A5h 14h 24h 04h A6h 80h 80h 80h A7h F6h F6h F6h A9h A0h A0h A0h AAh 0Fh 0Fh 0Fh ABh 00h 00h 00h ACh 00h 00h 00h ADh 00h 00h 00h AEh 0Fh 0Fh 0Fh AFh 01h 01h 01h 8.6.2.4 CFG98 Address 98h CFG98 REGISTER 7 6 5 NAME BIT ACCESS IBOOST_LIM_2X 7 R/W 4 3 2 1 0 IBOOST_LIM_2X (1) DESCRIPTION Select the inductor current limit range. When IBOOST_LIM_2X = 0, the inductor current limit can be set to 0.9 A, 1.2 A, 1.5 A or 1.8 A. When IBOOST_LIM_2X = 1, the inductor current limit can be set to 1.6 A, 2.1 A, or 2.6 A . This option is supported only on WQFN package and not on DSBGA package. See (1). 1.8 A is the maximum ISW_LIM supported with the DSBGA package. For applications requiring the ISW_LIM to be greater than 1.8 A and up to 2.6 A, WQFN package should be considered. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 37 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.2.5 CFG9E Address 9Eh CFG9E REGISTER 7 6 5 4 3 2 VBOOST_RANGE 1 0 HEADROOM_OFFSET NAME BIT ACCESS VBOOST_RANGE 5 R/W DESCRIPTION Select VBOOST range. When VBOOST_RANGE = 0, the output voltage range is from 7 V to 34 V When VBOOST_RANGE = 1, the output voltage range is from 16 V to 43 V For E07 and E11 version, VBOOST_RANGE=1 is not applicable. HEADROOM_ OFFSET 3:0 R/W LED driver headroom offset. This adjusts the LOW comparator threshold together with LED_HEADROOM bits and contributes to the MID comparator threshold. 0000 = 460 mV 0001 = 390 mV 0010 = 320 mV 0100 = 250 mV 1000 = 180 mV 8.6.2.6 CFG0 Address A0h CFG0 REGISTER 7 6 5 4 3 2 1 0 CURRENT LSB[7:0] NAME BIT ACCESS DESCRIPTION CURRENT LSB 7:0 R/W The 8-bits in this register (LSB) along the 4-bits defined in CFG1 Register (MSB) allow LED current to be set in 12-bit fine steps. These 12-bits further scale the maximum LED current set using CFG1 Register, CURRENT_MAX bits (denoted as IMAX ). If ISET_EN = 0, the LED current is defined with the bits as shown below. If ISET_EN = 1, then the external resistor connected to the ISET pin scales the LED current as shown below. 38 ISET_EN = 0 ISET_EN = 1 0000 0000 0000 0A 0A 0000 0000 0001 (1/4095) × IMAX (1/4095) × IMAX × 20,000 × 1.2V / RISET 0000 0000 0010 (2/4095) × IMAX (2/4095) x IMAX × 20,000 × 1.2V / RISET ... ... ... 0111 1111 1111 (2047/4095) × IMAX (2047/4095) × IMAX × 20,000 × 1.2V / RISET ... ... ... 1111 1111 1101 (4093/4095) × IMAX (4093/4095) × IMAX × 20,000 × 1.2V / RISET 1111 1111 1110 (4094/4095) × IMAX (4094/4095) × IMAX × 20,000 x 1.2V / RISET 1111 1111 1111 (4095/4095) × IMAX (4095/4095) × IMAX × 20,000 x 1.2V / RISET Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.2.7 CFG1 Address A1h CFG1 REGISTER 7 6 5 PDET_STDBY 4 3 2 CURRENT_MAX[2:0] 1 0 CURRENT MSB[11:8] NAME BIT ACCESS PDET_STDBY 7 R/W DESCRIPTION Enable Standby when PWM input is constant low (approx. 50 ms timeout). CURRENT_MAX 6:4 R/W Set Maximum LED current as shown below. This maximum current is scaled as described in the CFG0 Register. 000 = 5 mA 001 = 10 mA 010 = 15 mA 011 = 20 mA 100 = 23 mA 101 = 25 mA 110 = 30 mA 111 = 50 mA CURRENT MSB 3:0 R/W These bits form the 4 MSB bits for LED Current as described in CFG0 Register. 8.6.2.8 CFG2 Address A2h CFG2 REGISTER 7 6 RESERVED 5 4 3 2 1 0 UVLO_EN UVLO_TH BL_ON ISET_EN BOOST_ _FSET_EN PWM_ _FSET_EN NAME BIT ACCESS RESERVED 7:6 R/W DESCRIPTION UVLO_EN 5 R/W Undervoltage lockout protection enable. UVLO_TH 4 R/W UVLO threshold levels: 0 = 2.5 V 1 = 5.2 V BL_ON 3 R/W Enable backlight. This bit must be set for PWM only control. 0 = Backlight disabled. This selection is recommended for systems with an I2C master. With an I2C master, the backlight can be controlled by writing to the register 01h. 1 = Backlight enabled. This selection is recommended for systems with PWM only control. ISET_EN 2 R/W Enable LED current set resistor. 0 = Resistor is disabled and current is set with CURRENT and CURRENT_MAX EPROM register bits. 1 = Resistor is enabled and current is set with the RISET resistor AND CURRENT AND CURRENT_MAX EPROM register bits. BOOST_FSET_EN 1 R/W Enable configuration of the switching frequency via FSET pin. 0 = Configuration of the switching frequency via FSET pin is is disabled. The switching frequency is set with BOOST_FREQ EPROM register bits. 1 = Configuration of the switching frequency via FSET pin is is enabled. PWM_FSET_EN 0 R/W Enable configuration of the PWM dimming frequency via FSET pin. 0 = Configuration of the switching frequency via FSET pin is is disabled. The switching frequency is set with PWM_FREQ EPROM register bits. 1 = Configuration of the PWM dimming frequency via FSET pin is is enabled. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 39 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.2.9 CFG3 Address A3h CFG3 REGISTER 7 6 5 RESERVED 4 3 SLOPE[2:0] 2 FILTER[1:0] 1 0 PWM_INPUT_HYSTERESIS[1:0] NAME BIT ACCESS RESERVED 7 R/W DESCRIPTION SLOPE 6:4 R/W Select brightness change transition duration 000 = 0 ms (immediate change) 001 = 1 ms 010 = 2 ms 011 = 50 ms 100 = 100 ms 101 = 200 ms 110 = 300 ms 111 = 500 ms FILTER 3:2 R/W Select brightness change transition filtering strength 00 = No filtering 01 = light smoothing 10 = medium smoothing 11 = heavy smoothing PWM_INPUT_ _HYSTERESIS 1:0 R/W PWM input hysteresis function. 00 = OFF 01 = 1-bit hysteresis with 13-bit resolution 10 = 1-bit hysteresis with 12-bit resolution 11 = 1-bit hysteresis with 8-bit resolution 8.6.2.10 CFG4 Address A4h CFG4 REGISTER 7 6 5 PWM_TO_I_THRESHOLD[3:0] NAME BIT ACCESS PWM_TO_I_THRESHOLD 7:4 R/W 40 4 3 2 RESERVED STEADY_ _DITHER 1 0 DITHER[1:0] DESCRIPTION Select switch point between PWM and pure current dimming 0000 = current dimming across entire range 0001 = switch point at 10% of the maximum LED current. 0010 = switch point at 12.5% of the maximum LED current. 0011 = switch point at 15% of the maximum LED current. 0100 = switch point at 17.5% of the maximum LED current. 0101 = switch point at 20% of the maximum LED current. 0110 = switch point at 22.5% of the maximum LED current. 0111 = switch point at 25% of the maximum LED current. This is a recommended selection. 1000 = switch point at 33.33% of the maximum LED current. 1001 = switch point at 41.67% of the maximum LED current. 1010 = switch point at 50% of the maximum LED current. 1011 to 1111 = PWM dimming across entire range RESERVED 3 R/W STEADY_DITHER 2 R/W Dither function method select: 0 = Dither only on transitions 1 = Dither at all times DITHER 1:0 R/W Dither function control 00 = Dithering disabled 01 = 1-bit dithering 10 = 2-bit dithering 11 = 3-bit dithering Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.2.11 CFG5 Address A5h CFG5 REGISTER 7 6 PWM_DIRECT 5 4 3 PS_MODE[2:0] 2 1 0 PWM_FREQ[3:0] NAME BIT ACCESS PWM_DIRECT 7 R/W DESCRIPTION Intended for certain test mode purposes. When enabled, the entire pipeline is bypassed and PWM output is connected with PWM input. PS_MODE 6:4 R/W Select PWM output phase configuration: 000 = 6-phase, 6 drivers (0°, 60°, 120°, 180°, 240°, 320°) 001 = 5-phase, 5 drivers (0°, 72°, 144°, 216°, 288°, OFF) 010 = 4-phase, 4 drivers (0°, 90°, 180°, 270°, OFF, OFF) 011 = 3-phase, 3 drivers (0°, 120°, 240°, OFF, OFF, OFF) 100 = 2-phase, 2 drivers (0°, 180°, OFF, OFF, OFF, OFF) 101 = 3-phase, 6 drivers (0°, 0°, 120°, 120°, 240°, 240°) 110 = 2-phase, 6 drivers (0°, 0°, 0°, 180°, 180°, 180°) 111 = 1-phase, 6 drivers (0°, 0°, 0°, 0°, 0°, 0°) PWM_FREQ 3:0 R/W 0h = 4,808 Hz (11-bit) 1h = 6,010 Hz (10-bit) 2h = 7,212 Hz (10-bit) 3h = 8,414 Hz (10-bit) 4h = 9,616 Hz (10-bit) 5h = 12,020 Hz (9-bit) 6h = 13,222 Hz (9-bit) 7h = 14,424 Hz (9-bit) 8h = 15,626 Hz (9-bit) 9h = 16,828 Hz (9-bit) Ah = 18,030 Hz (9-bit) Bh = 19,232 Hz (9-bit) Ch = 24,040 Hz (8-bit) Dh = 28,848 Hz (8-bit) Eh = 33,656 Hz (8-bit) Fh = 38,464 Hz(8-bit) Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 41 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.2.12 CFG6 Address A6h CFG6 REGISTER 7 6 5 4 BOOST_FREQ[1:0] 3 2 1 0 VBOOST[5:0] NAME BIT ACCESS BOOST_FREQ 7:6 R/W DESCRIPTION Set boost switching frequency when BOOST_FSET_EN = 0. 00 = 312 kHz 01 = 625 kHz 10 = 1250 kHz 11 = undefined VBOOST 5:0 R/W Boost output voltage. When ADAPTIVE = 1, this is the boost minimum and initial voltage. 8.6.2.13 CFG7 Address A7h CFG7 REGISTER 7 6 RESERVED 42 5 4 EN_DRV3 EN_DRV2 ACCESS 3 2 RESERVED 1 0 IBOOST_LIM[1:0] NAME BIT DESCRIPTION RESERVED 7:6 EN_DRV3 5 R/W Selects boost driver strength to set boost slew rate. See EMI Reduction for more detail. 0 = Driver3 disabled 1 = Driver3 enabled EN_DRV2 4 R/W Selects boost driver strength to set boost slew rate. See EMI Reduction for more detail. 0 = Driver2 disabled 1 = Driver2 enabled RESERVED 3:2 R/W IBOOST_LIM 1:0 R/W Select boost inductor current limit (IBOOST_LIM_2X = 0 / IBOOST_LIM_2X = 1) 00 = 0.9 A / 1.6 A 01 = 1.2 A / 2.1 A 10 = 1.5 A / 2.6 A 11 = 1.8 A / not permitted Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 8.6.2.14 CFG9 Address A9h CFG9 REGISTER 7 6 5 4 VBOOST_MAX[2:0] JUMP_EN 3 2 1 JUMP_THRESHOLD[1:0] NAME BIT ACCESS VBOOST_MAX 7:5 R/W Select the maximum boost voltage (typ values) ( VBOOST_RANGE = 0 / VBOOST_RANGE = 1) 010 = NA / 21 V 011 = NA / 25 V 100 = 21 V / 30 V 101 = 25 V / 34.5 V 110 = 30 V / 39 V 111 = 34 V / 43 V 0 JUMP_VOLTAGE[1:0] DESCRIPTION JUMP_EN 4 R/W Enable JUMP detection on the PWM input. JUMP_THRESHOLD 3:2 R/W Select JUMP threshold: 00 = 10% 01 = 30% 10 = 50% 11 = 70% JUMP_VOLTAGE 1:0 R/W Select JUMP voltage: 00 = 0.5 V 01 = 1 V 10 = 2 V 11 = 4 V 8.6.2.15 CFGA Address AAh CFGA REGISTER 7 6 SSCLK_EN RESERVED 5 4 NAME BIT ACCESS RESERVED 3 ADAPTIVE 2 1 0 DRIVER_HEADROOM[2:0] DESCRIPTION SSCLK_EN 7 R/W RESERVED 6 R/W Enable spread spectrum function RESERVED 5:4 R/W ADAPTIVE 3 R/W Enable adaptive boost control DRIVER_HEADROOM 2:0 R/W LED driver headroom control. This sets the LOW comparator threshold and contributes to the MID comparator threshold. 000 = HEADROOM_OFFSET + 875 mV 001 = HEADROOM_OFFSET + 750 mV 010 = HEADROOM_OFFSET + 625 mV 011 = HEADROOM_OFFSET + 500 mV 100 = HEADROOM_OFFSET + 375 mV 101 = HEADROOM_OFFSET + 250 mV 110 = HEADROOM_OFFSET + 125 mV 111 = HEADROOM_OFFSET mV Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 43 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 8.6.2.16 CFGE Address AEh CFGE REGISTER 7 6 5 STEP_UP[1:0] 4 STEP_DN[1:0] 3 2 1 LED_FAULT_TH[2:0] 0 LED_COMP_HYST[1:0] NAME BIT ACCESS STEP_UP 7:6 R/W DESCRIPTION Adaptive headroom UP step size 00 = 105 mV 01 = 210 mV 10 = 420 mV 11 = 840 mV STEP_DN 5:4 R/W Adaptive headroom DOWN step size 00 = 105 mV 01 = 210 mV 10 = 420 mV 11 = 840 mV LED_FAULT_TH 3:2 R/W LED headroom fault threshold. This sets the HIGH comparator threshold. 00 = 5 V 01 = 4 V 10 = 3 V 11 = 2 V LED_COMP_HYST 1:0 R/W LED headrom comparison hysteresis. This sets the MID comparator threshold. 00 = DRIVER_HEADROOM + 1000 mV 01 = DRIVER_HEADROOM + 750 mV 10 = DRIVER_HEADROOM + 500 mV 11 = DRIVER_HEADROOM + 250 mV 8.6.2.17 CFGF Address AFh CFGF REGISTER 7 6 5 4 3 2 1 0 REVISION 44 NAME BIT ACCESS REV 7:0 R/W DESCRIPTION EPROM Settings Revision ID code Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 9.1 Application Information 9.1.1 Using LP8556 With I2C Host 9.1.1.1 Setting Boost Switching and PWM Dimming Frequencies Boost switching and PWM dimming frequencies can be set via EEPROM when BOOST_FSET_EN = 0 and PWM_FSET_EN = 0. Available options are shown in Table 11 and Table 12. Table 11. Configuring Boost Switching Frequency via EPROM BOOST_FSET_EN BOOST_FREQ[1:0] ƒSW [kHz] 0 00 312 0 01 625 0 10 1250 0 11 Reserved Table 12. Configuring PWM Dimming Frequency via EPROM PWM_FSET_EN PWM_FREQ[3:0] ƒPWM [Hz] (Resolution) 0 0000 4808 (11-bit) 0 0001 6010 (10-bit) 0 0010 7212 (10-bit) 0 0011 8414 (10-bit) 0 0100 9616 (10-bit) 0 0101 12020 (9-bit) 0 0110 13222 (9-bit) 0 0111 14424 (9-bit) 0 1000 15626 (9-bit) 0 1001 16828 (9-bit) 0 1010 18030 (9-bit) 0 1011 19232 (9-bit) 0 1100 24040 (8-bit) 0 1101 28848 (8-bit) 0 1110 33656 (8-bit) 0 1111 38464 (8-bit) 9.1.1.2 Setting Full-Scale LED Current The LED current per output is configured by programming the CURRENT_MAX and CURRENT registers when ISET_EN = 0. Available options are shown below. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 45 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Table 13. Setting Full-Scale LED Current with EEPROM ISET_EN CURRENT_MAX CURRENT[11:0] FULL-SCALE ILED [mA] 0 0 FFFh 5 0 1 FFFh 10 0 10 FFFh 15 0 11 FFFh 20 0 100 FFFh 23 0 101 FFFh 25 0 110 FFFh 30 0 111 FFFh 50 0 000 – 111 001h – FFFh (CURRENT/4095) × CURRENT_IMAX 9.1.2 Using LP8556 With Configuration Resistors and IO Pins 9.1.2.1 Setting Boost Switching and PWM Dimming Frequencies Boost switching and PWM dimming frequencies can be set via resistor when BOOST_FSET_EN = 1 and PWM_FSET_EN = 1. Available options are shown in Table 14. Table 14. Configuring PWM Dimming Frequency With an External Resistor 46 RFSET [kΩ] (TOLERANCE) ƒSW [kHz] BOOST_FSET_EN = 1 ƒPWM [Hz] (RESOLUTION) PWM_FSET_EN = 1 Floating or FSET pin pulled HIGH 1250 9616 (10-bit) 470 k - 1 M (±5%) 312 2402 (12-bit) 300 k, 330 k (±5%) 312 4808 (11-bit) 200 k (±5%) 312 6010 (10-bit) 147 k, 150k, 154 k, 158k (±1%) 312 9616 (10-bit) 121 k (±1%) 312 12020 (9-bit) 100 k (±1%) 312 14424 (9-bit) 86.6 k (±1%) 312 16828 (9-bit) 75 k (±1%) 312 19232 (9-bit) 63.4 k (±1%) 625 2402 (12-bit) 52.3 k, 53.6 k (±1%) 625 4808 (11-bit) 44.2k, 45.3 k (±1%) 625 6010 (10-bit) 39.2 k (±1%) 625 9616 (10-bit) 34 k (±1%) 625 12020 (9-bit) 30.1k (±1%) 625 14424 (9-bit) 26.1 k (±1%) 625 16828 (9-bit) 23.2 k (±1%) 625 19232 (9-bit) 20.5 k (±1%) 1250 2402 (12-bit) 18.7 k (±1%) 1250 4808 (11-bit) 16.5k (±1%) 1250 6010 (10-bit) 14.7 k (±1%) 1250 9616 (10-bit) 13 k (±1%) 1250 12020 (9-bit) 11.8k (±1%) 1250 14424 (9-bit) 10.7 k (±1%) 1250 16828 (9-bit) 9.76 k (±1%) 1250 19232 (9-bit) FSET pin shorted to GND 1250 Same as PWM input frequency Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 9.1.2.2 Setting Full-Scale LED Current The LED current per output is configured by ISET resistor when ISET_EN=1. In this mode the CURRENT_IMAX and CURRENT registers can also further scale the LED current. Available options are shown in Table 15. Table 15. Setting Full-Scale LED Current with ISET Resistor RISET [Ω] ISET_EN CURRENT_MAX CURRENT[11:0] FULL-SCALE ILED [mA] 24 k 1 0 FFFh 5 24 k 1 1 FFFh 10 24 k 1 10 FFFh 15 24 k 1 11 FFFh 20 24 k 1 100 FFFh 23 24 k 1 101 FFFh 25 24 k 1 110 FFFh 30 24 k 1 111 FFFh 50 12 k – 100 k 1 000–111 001h–FFFh (CURRENT/4095) × IMAX × 20,000 × 1.2 V / RISET 9.2 Typical Application 7V ± 43V L1 2.7V - 36V D1 1.1 ” 9OUT / VIN ” 15 VOUT VIN CIN 2.7V ± 20V VDD COUT SW VDD CVDD VBOOST EN / VDDIO 1.62V ± 3.6V EN / VDDIO LED1 CVLDO VLDO LED2 RFSET FSET RISET LP8556 LED3 ISET LED4 Optional LED5 PWM MCU LED6 SDA SCL GNDs Figure 19. LP8556 Typical Application Schematic Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 47 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Typical Application (continued) 9.2.1 Design Requirements Table 16. Recommended Inductance ƒSW MIN 1250 3.3 625 312 TYP MAX UNIT 22 µH 6.8 68 µH 10 100 µH MAX UNIT Table 17. Recommended Output Capacitance ƒSW MIN TYP 1250 4.7 µF 625 4.7 µF 312 10 µF 9.2.2 Detailed Design Procedure 9.2.2.1 Recommended Inductance for the Boost Power Stage Assumes 20 mA as the maximum LED current per string and 3.3 V as the maximum LED forward voltage. NUMBER OF LED STRINGS NUMBER OF LEDS PER STRING 6 6 L1 INDUCTANCE BOOST INPUT VOLTAGE RANGE ƒSW = 1250 kHz ƒSW = 625 kHz ƒSW = 312 kHz 2.7 V - 4.4 V 3.3 μH - 6.8 μH 6.8 μH - 15 μH 10 μH - 33 μH 5.4 V - 8.8 V 10 μH - 22 μH 22 μH - 47 μH 47 μH - 100 μH 2.7 V - 4.4 V 4.7 μH - 10 μH 10 μH - 15 μH 22 μH - 33 μH 5.4 V - 8.8 V 10 μH - 22 μH 22 μH - 68 μH 47 μH - 100 μH 6 8 4 10 5.4 V - 8.8 V 6.8 μH - 22 μH 22 μH - 47 μH 47 μH - 100 μH 4 12 5.4 V - 8.8 V 10 μH - 22 μH 22 μH - 47 μH 33 μH - 100 μH 9.2.2.2 Recommended Capacitances for the Boost and LDO Power Stages (1) (1) 48 SWITCHING FREQUENCY [kHz] CIN [μF] COUT [μF] CVLDO [μF] 1250 2.2 4.7 10 625 2.2 4.7 10 312 4.7 10 10 Capacitance of Multi-Layer Ceramic Capacitors (MLCC) can change significantly with the applied DC voltage. Use capacitors with good capacitance versus DC bias characteristics. In general, MLCC in bigger packages have lower capacitance de-rating than physically smaller capacitors. Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 9.2.3 Application Curves Unless otherwise specified: VIN = 3.8 V, CVLDO = 10 μF, L1 = 4.7 μH, CIN = 2.2 μF, COUT = 4.7 μF, ƒSW = 1.25 MHz 95 95 Boost Efficiency 85 EFFICIENCY [%] EFFICIENCY [%] 85 Boost Efficiency LED Efficiency 75 VIN = 3.8V 6x7 LED Array ILEDMAX = 20 mA/CH L = 10 PH 1.5 mm Max Height fSW = 625 kHz 65 55 LED Efficiency 75 VIN = 6.3V 6x7 LED Array ILEDMAX = 20 mA/CH L = 10 PH 1.5 mm Max Height fSW = 625 kHz 65 55 45 45 0 20 40 60 80 100 0 20 BRIGHTNESS [%] 80 100 BRIGHTNESS [%] Figure 21. Boost and LED Drive Efficiency 95 95 Boost Efficiency Boost Efficiency 85 EFFICIENCY [%] EFFICIENCY [%] 60 Figure 20. Boost and LED Drive Efficiency 85 LED Efficiency 75 VIN = 8.6V 6x7 LED Array ILEDMAX = 20 mA/CH L = 10 PH 1.5 mm Max Height fSW = 625 kHz 65 55 LED Efficiency 75 VIN = 12.9V 6x7 LED Array ILEDMAX = 20 mA/CH L = 10 PH 1.5 mm Max Height fSW = 625 kHz 65 55 45 45 0 20 40 60 80 100 0 20 BRIGHTNESS [%] 40 60 80 100 BRIGHTNESS [%] Figure 22. Boost and LED Drive Efficiency Figure 23. Boost and LED Drive Efficiency 200 500 Adaptive Dimming Adaptive Dimming 180 400 PWM Dimming LUMINANCE [Nits] OPTICAL EFFICIENCY [Nits/W] 40 160 VIN = 3.6V 10" Panel 6x7 LED Array ILEDMAX = 23 mA/CH L = 4.7 PH 1.5 mm Max Height fSW = 1.25 MHz 140 120 PWM Dimming 300 VIN = 3.6V 10" Panel 6x7 LED Array ILEDMAX = 23 mA/CH L = 4.7 PH 1.5 mm Max Height fSW = 1.25 MHz 200 100 100 0 0 20 40 60 80 100 0 BRIGHTNESS [%] Figure 24. Optical Efficiency 20 40 60 80 100 BRIGHTNESS [%] Figure 25. Luminance as a Function of Brightness Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 49 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Unless otherwise specified: VIN = 3.8 V, CVLDO = 10 μF, L1 = 4.7 μH, CIN = 2.2 μF, COUT = 4.7 μF, ƒSW = 1.25 MHz 5 100 INPUT POWER [W] 4 3 2 POWER SAVINGS [mW] VIN = 3.6V 10" Panel 6x7 LED Array ILEDMAX = 23 mA/CH L = 4.7 PH 1.5 mm Max Height fSW = 1.25 MHz PWM Dimming 1 80 60 VIN = 3.6V 10" Panel 6x7 LED Array ILEDMAX = 23 mA/CH L = 4.7 PH 1.5 mm Max Height fSW = 1.25 MHz 40 20 Adaptive Dimming 0 0 0 100 200 300 400 500 0 LUMINANCE [Nits] 40 60 80 100 BRIGHTNESS [%] Figure 26. Input Power as a Function of Brightness 50 20 Figure 27. Power Savings With Adaptive Dimming when Compared to PWM Dimming Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 10 Power Supply Recommendations The device is designed to operate from a VDD input voltage supply range from 2.7 V to 20 V. This input supply must be well regulated and able to withstand maximum input current and maintain stable voltage without voltage drop even at load transition condition (start-up or rapid brightness change). The resistance of the input supply rail must be low enough that the input current transient does not cause drop high enough in the LP8556 supply voltage that can cause false UVLO fault triggering. If the input supply is located more than a few inches from the LP8556 device, additional bulk capacitance may be required in addition to the ceramic bypass capacitors. Depending on device EEPROM configuration and usage case the boost converter is configured to operate optimally with certain input voltage range. 11 Layout 11.1 Layout Guidelines Figure 28 and Figure 29 follow proper layout guidelines and should be used as a guide for laying out the LP8556 circuit. The LP8556 inductive boost converter has a high switched voltage at the SW pin, and a step current through the Schottky diode and output capacitor each switching cycle. The high switching voltage can create interference into nearby nodes due to electric field coupling (I = C × dV/dt). The large step current through the diode and the output capacitor can cause a large voltage spike at the SW and VBOOST pins due to parasitic inductance in the step current conducting path (V = L × di/dt). Board layout guidelines are geared towards minimizing this electric field coupling and conducted noise. The following list details the main (layout sensitive) areas of the device inductive boost converter in order of decreasing importance: 1. Boost Output Capacitor Placement – Because the output capacitor is in the path of the inductor current discharge path, there is a high-current step from 0 to IPEAK each time the switch turns off and the Schottky diode turns on. Any inductance along this series path from the diodes cathode, through COUT, and back into the LP8556 GND pin contributes to voltage spikes (VSPIKE = LP_ × dI/dt) at SW and OUT. These spikes can potentially overvoltage the SW and VBOOST pins, or feed through to GND. To avoid this, COUT+ must be connected as close to the cathode of the Schottky diode as possible, and COUT− must be connected as close to the LP8556 GND bumps as possible. The best placement for COUT is on the same layer as the LP8556 to avoid any vias that can add excessive series inductance. 2. Schottky Diode Placement – In the device boost circuit the Schottky diode is in the path of the inductor current discharge. As a result the Schottky diode has a high-current step from 0 to IPEAK each time the switch turns off and the diode turns on. Any inductance in series with the diode causes a voltage spike (VSPIKE = LP_ × dI/dt) at SW and OUT. This can potentially over-voltage the SW pin, or feed through to VOUT and through the output capacitor, into GND. Connecting the anode of the diode as close to the SW pin as possible, and connecting the cathode of the diode as close to COUT+ as possible reduces the inductance (LP_) and minimize these voltage spikes. 3. Boost Input/VDD Capacitor Placement – The LP8556 input capacitor filters the inductor current ripple and the internal MOSFET driver currents. The inductor current ripple can add input voltage ripple due to any series resistance in the input power path. The MOSFET driver currents can add voltage spikes on the input due to the inductance in series with the VIN/VDD and the input capacitor. Close placement of the input capacitor to the VDD pin and to the GND pin is critical because any series inductance between VIN/VDD and CIN+ or CIN– and GND can create voltage spikes that could appear on the VIN/VDD supply line and GND. – Close placement of the input capacitor at the input side of the inductor is also critical. The source impedance (inductance and resistance) from the input supply, along with the input capacitor of the LP8556, forms a series RLC circuit. If the output resistance from the source is low enough, the circuit is underdamped and will have a resonant frequency (typically the case). – Depending on the size of LS, the resonant frequency could occur below, close to, or above the switching frequency of the LP8556. This can cause the supply current ripple to be: Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 51 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com Layout Guidelines (continued) – Approximately equal to the inductor current ripple when the resonant frequency occurs well above the LP8556 switching frequency. – Greater than the inductor current ripple when the resonant frequency occurs near the switching frequency. – Less than the inductor current ripple when the resonant frequency occurs well below the switching frequency. 11.2 Layout Examples CIN COUT D1 L1 ISET FSET SW GND SW SDA SCL SW GND SW PWM EN VDDIO VDD VBOOST FSET LED3 VLDO ISET GND LED2 LED6 LED5 LED4 LED1 CVDD CVLDO Figure 28. DSBGA Layout 52 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 LP8556 www.ti.com SNVS871M – JULY 2012 – REVISED JUNE 2020 Layout Examples (continued) CIN COUT L1 D1 SCL SDA GND _SW GND _SW SW SW CVDD EN/VDDIO GND NC ISET PWM VDD GND FSET GND VBOOST LED1 VLDO LED 2 LED 3 GND LED 4 LED 5 LED 6 ISET FSET CVLDO Figure 29. WQFN Layout Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 53 LP8556 SNVS871M – JULY 2012 – REVISED JUNE 2020 www.ti.com 12 Device and Documentation Support 12.1 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 12.2 Community Resources TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight from the experts. Search existing answers or ask your own question to get the quick design help you need. Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. 12.3 Trademarks E2E is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 12.4 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 12.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 13 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 54 Submit Documentation Feedback Copyright © 2012–2020, Texas Instruments Incorporated Product Folder Links: LP8556 PACKAGE OPTION ADDENDUM www.ti.com 13-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LP8556SQ-E00/NOPB ACTIVE WQFN RTW 24 1000 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E0 LP8556SQ-E08/NOPB ACTIVE WQFN RTW 24 1000 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E8 LP8556SQ-E09/NOPB ACTIVE WQFN RTW 24 1000 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E9 LP8556SQE-E00/NOPB ACTIVE WQFN RTW 24 250 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E0 LP8556SQE-E08/NOPB ACTIVE WQFN RTW 24 250 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E8 LP8556SQE-E09/NOPB ACTIVE WQFN RTW 24 250 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E9 LP8556SQX-E00/NOPB ACTIVE WQFN RTW 24 4500 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E0 LP8556SQX-E08/NOPB ACTIVE WQFN RTW 24 4500 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E8 LP8556SQX-E09/NOPB ACTIVE WQFN RTW 24 4500 RoHS & Green NIPDAU | SN Level-1-260C-UNLIM -30 to 85 L8556E9 LP8556TME-E02/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E2 LP8556TME-E03/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E3 LP8556TME-E04/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E4 LP8556TME-E05/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E5 LP8556TME-E06/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E6 LP8556TME-E09/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E9 LP8556TME-E11/NOPB ACTIVE DSBGA YFQ 20 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 6E11 LP8556TMX-E02/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E2 LP8556TMX-E03/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E3 LP8556TMX-E04/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E4 LP8556TMX-E05/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E5 Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com Orderable Device 13-Dec-2020 Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LP8556TMX-E06/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E6 LP8556TMX-E09/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 56E9 LP8556TMX-E11/NOPB ACTIVE DSBGA YFQ 20 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -30 to 85 6E11 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of