LP5524

LP5524 Parallel LED Driver with PWM Brightness Control in Micro SMD Package July 2007 LP5524 Parallel LED Driver with PWM Brightness Control in Micro SMD Package General Description The LP5524 is a highly integrated dual-zone LED driver that can drive up to four LEDs in parallel with a total output current of 100mA. Regulated high side internal current sources deliver excellent current and brightness matching in all LEDs. LED driver current sources are split into two independently controlled banks for driving secondary displays, keypad and indicator LEDs. Brightness control is achieved by applying PWM signals to each enable pin. Default LED current is factory-programmable and an optional external resistor can be used to set LED current to user programmable values. LP5524 is available in National’s tiny 9-bump thin micro SMD package. Features ■ High side LED driver ■ Drives 4 LEDs with Up to 25mA per LED ■ Ultra-Small Solution Size: ■ ■ ■ ■ — No External Components — Micro SMD-9 Package with 0.4 mm pitch: 1.215mm x 1.215mm x 0.6mm (LxWxH) 0.4% Typical Current Matching PWM Brightness Control Over-Current Protection Wide Input Voltage Range: 2.7V to 5.5V Applications ■ Sub display Backlight ■ Keypad LED Backlight ■ Indicator LED Typical Application 30007601 © 2007 National Semiconductor Corporation 300076 www.national.com LP5524 Connection Diagrams and Package Mark Information Connection Diagrams Micro SMD-9 package, 1.215 x 1.215 x 0.60 mm body size, 0.4 mm pitch NS Package Number TMD09AAA 30007602 30007603 Top View Bottom View PACKAGE MARK 30007604 ORDERING INFORMATION Order Number LP5524TM-5 LP5524TMX-5 Default LED Current (Note 1) 5 mA 5 mA Package Marking V2 V2 Supplied As TNR 250 TNR 3000 Spec/Flow NOPB NOPB Note 1: Other current options are available upon request, please contact the National Semiconductor Sales Office. PIN DESCRIPTIONS Pin A1 A2 A3 B1 B2 B3 C1 C2 C3 Name ISET ENB ENA D1B VIN D1A D2B GND D2A Type AI DI DI AO P AO AO G AO Current set input Enable for bank B Enable for bank A Current source output, bank B LED1 Power supply pin Current source output, bank A LED1 Current source output, bank B LED2 Ground Current source output, bank A LED2 Description A: Analog Pin D: Digital Pin G: Ground Pin P: Power Pin I: Input Pin O: Output Pin www.national.com 2 LP5524 Absolute Maximum Ratings (Notes 2, 3) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. V (VIN, DX, ISET) Voltage on logic pins (ENA, ENB) Continuous Power Dissipation (Note 4) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Reflow soldering, 3 times) ESD Rating (Note 6) Human Body Model -0.3V to +6.0V -0.3V to +6.0V Internally Limited 125°C -65°C to +150°C (Note 5) Operating Ratings (Notes 2, 3) Voltage on power pin (VIN) 2.7V to 5.5V Junction Temperature (TJ) Range -40°C to +125°C Ambient Temperature (TA) Range -40°C to +85°C (Note 7) Thermal Properties Junction-to-Ambient Thermal Resistance (θJA), TMD09 Package (Note 8) 80 - 125°C/W 2 kV (Notes 3, 9) Limits in standard typeface are for TJ = 25°C. Limits in boldface type apply over the operating ambient temperature range (-40°C < TA < +85°C). Unless otherwise noted, specifications apply to the LP5524 Block Diagram with: VIN = 3.6V, RISET = 32.4 kΩ, CIN = 100 nF. Symbol IVIN IDX IOUT Parameter Shutdown Supply Current Active Mode Supply Current Recommended LED Current LED Output Current Accuracy LED Output Current Accuracy IMATCH ΔIDX%/ΔVIN ΔIDX%/ΔVDX VHR IMIRROR VISET IISET tPWM MIN VIL VIH IIN tSD LED Current Matching (Note 10) Line Regulation Load Regulation Minimum Headroom Voltage (VIN - VDX)(Note 11) External RISET to LED Current Mirroring Ratio ISET Reference Voltage ISET Pin Current Range Recommended Minimum On Time For PWM Signal Logic Input Low Level Logic Input High Level CTRL Input Current Shutdown Delay Time ENA / ENB = 1.2V Delay from ENA and ENB = low to IDX = 0.1 x IDX nom 1.2 1.2 20 1.9 25 2.5 33 0.4 VDX < VIN - 0.2V IDX set to 5 mA IDX set to 15 mA IDX = 5mA, VDX = VIN - 0.2V ISET = open IDX = 15.9mA, VDX = VIN - 0.2V IDX = 15.9mA Condition ENA = ENB = 0V ENA = ENB = H, ISET = open 3 0.5 0.5 0.4 1 0.4 10 30 1:416 1.237 62.5 V µA μs V V µA µs 75 Min Typ 0.2 170 Max 1 210 25 5 4 2.5 Units µA µA mA % % % %/V %/V mV mV Electrical Characteristics Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 3: All voltages are with respect to the potential at the GND pin. Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=160°C (typ.) and disengages at TJ=140°C (typ.). Note 5: For detailed soldering specifications and information, please refer to National Semiconductor Application Note AN1112 : Micro SMD Wafer Level Chip Scale Package. Note 6: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. MIL-STD-883 3015.7 Note 7: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. 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 (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). 3 www.national.com LP5524 Note 8: .Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. Note 9: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm. Note 10: Matching is the maximum difference from the average. Note 11: The current source is connected internally between VIN an VDX. The voltage across the current source, (VIN - VDX), is referred to a Headroom Voltage (VHR). Minimum Headroom Voltage is defined as the VHR voltage when the LED current has dropped 20% from the value measured at VDX = VIN - 1V. LP5524 Block Diagram 30007636 www.national.com 4 LP5524 LED Driver Typical Performance Characteristics TJ = 25°C. Unless otherwise noted, typical performance characteristics apply to the LP5524 Block Diagram with: VIN = 3.6V, RISET = 32.4 kΩ, CIN = 100 nF. Output Current vs RISET (Expanded Range) Output Current vs RISET 30007622 30007623 Output Current vs Input Voltage (ISET Connected To VDD) Output Current vs Headroom Voltage 30007625 30007624 PWM Responce (Both Channels) PWM Response (Single Channel) 30007629 30007627 5 www.national.com LP5524 Application Information ENABLE MODE The LP5524 has four constant current LED outputs which are split into two independently controlled banks. Each bank has its own enable input. ENA is used to control bank A and ENB is used to control bank B. Both enables are active high and have internal pull–down resistors. When both enables are low part is in low power standby mode. Driving either enable high will activate the part and corresponding LED outputs. ISET PIN An external resistor (RISET) connected to ISET pin sets the output current of all the LEDs. The internal current mirror sets the LEDs output current with a 416:1 ratio to the current through RISET. The following equation approximates the LED current: IDX = 515 / RISET (Amps) The use of RISET is optional. If RISET is not used ISET pin can be left floating or connected to VIN. In these cases LED current is set to default current. PWM BRIGHTNESS CONTROL The brightness of LEDs can be linearly varied from zero up to the maximum programmed current level by applying a Pulse– Width–Modulated signal to the ENx pin of the LP5524. The following procedures illustrate how to program the LED drive current and adjust the output current level using a PWM signal. 1. Determine the maximum desired LED current. Use the IDX equation to calculate RISET. 2. Brightness control can be implemented by pulsing a signal at the ENx pin. LED brightness is proportional to the duty cycle (D) of the PWM signal. For linear brightness control over the full duty cycle adjustment range, the LP5524 uses a special turn–off time delay to compensate the turn–on time of the device. If the PWM frequency is much less than 100Hz, flicker may be seen in the LEDs. For the LP5524, zero duty cycle will turn off the LEDs and a 50% duty cycle will result in an average IDX being half of the programmed LED current. For example, if RISET is set to program LED current to 15 mA, a 50% duty cycle will result in an average IDX of 7.5mA. LED HEADROOM VOLTAGE A single current source is connected internally between VIN and DX outputs (D1A, D2A, D1B and D2B). The voltage across the current source, (VIN – VDX), is referred to as headroom voltage (VHR). The current source requires a sufficient amount of headroom voltage to be present across it in order to regulate properly. FigureOutput Current vs Headroom Voltage shows how output current of the LP5524 varies with respect to headroom voltage. On the flat part of the graph, the current is regulated properly as there is sufficient headroom voltage for regulation. On the sloping part of the graph the headroom voltage is too small, the current source is squeezed, and the current drive capability is limited. Thus, operating the LP5524 with insufficient headroom voltage across the current source should be avoided. LED OUTPUTS If more than 25 mA of output current is required LED outputs can be connected parallel. Connecting LED outputs of different group parallel generates a simply two stage brightness control. With IDX set to 25 mA, enabling one group sets the LED current to 25 mA. Enabling second bank increases the LED current to 50 mA. Unused LED outputs can be left floating or tied to VIN. www.national.com 6 LP5524 Recommended External Components INPUT CAPACITOR, CIN Although not required for normal operation, a capacitor can be added to VIN to reduce line noise. A surface-mount multilayer ceramic capacitor (MLCC) is recommended. MLCCs with a X7R or X5R temperature characteristic are preferred. CURRENT SET RESISTOR, RISET If other than 5 mA current is required, RISET resistor can be used to adjust the current. For 15.9 mA current 32.4 kΩ resistor is required. Accuracy of the resistor directly effects to the accuracy of the LED current. 1% or better is recommended. LED Forward voltage of LED must be less than minimum input voltage minus minimum headroom voltage (VHR). For example with 2.7V input voltage and 20 mA LED current the maximum LED forward voltage is 2.7V - 100 mV = 2.6V. List of Recommended External Components Symbol CIN RISET LEDs Symbol Explanation VDD Bypass Capacitor Value 100 User defined Unit nF kΩ Type Ceramic, X7R or X5R 1% Current Set Resistor for 15.9 mA LED Current 32.4 Recommended E96 Series (1% Tolerance) Current Set Resistors RISET (kΩ) 169 127 102 84.5 73.2 64.9 56.2 51.1 46.4 42.2 39.2 36.5 IDX = 515 / RISET (Amps) IDX (mA) 3.0 4.1 5.0 6.1 7.0 7.9 9.2 10.1 11.1 12.2 13.1 14.1 RISET (kΩ) 34.0 32.4 30.1 28.7 26.7 25.5 24.3 23.2 22.1 21.5 20.5 IDX (mA) 15.1 15.9 17.1 17.9 19.3 20.2 21.2 22.2 23.3 24.0 25.1 7 www.national.com LP5524 Physical Dimensions inches (millimeters) unless otherwise noted The dimension for X1, X2 and X3 are as given: — X1 = 1.215 mm ±0.03 mm — X2 = 1.215 mm ±0.03 mm — X3 = 0.60 mm ±0.075 mm NS Package Number TMD09AAA microSMD-9 See National Semiconductor Application Note 1112 Micro SMD Wafer Level Chip Scale Package for PCB design and assembly instructions. www.national.com 8 LP5524 Notes 9 www.national.com LP5524 Parallel LED Driver with PWM Brightness Control in Micro SMD Package Notes THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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