LTC3209EUF-2

LTC3209-1/LTC3209-2 600mA Main/Camera LED Controller DESCRIPTIO U FEATURES ■ ■ Multimode Charge Pump Provides Up to 94% Efficiency (1x, 1.5x, 2x) Up to 600mA Total Output Current LTC3209-1: 8 Current Sources Available as 6 × 25mA MAIN, 1 × 400mA CAM and 1 × 15mA AUX LTC3209-2: 8 Current Sources Available as 5 × 25mA MAIN, 2 × 200mA CAM and 1 × 15mA AUX LED On/Off and Brightness Level Programmable Using 2-Wire I2CTM Interface Automatic Charge Pump Mode Switching or Fixed Mode for Power Supply Generation Low Noise Constant Frequency Operation* Internal Soft-Start Limits Inrush Current During Start-up and Mode Switching Short Circuit/Thermal/Open-Shorted LED Protection 256 Brightness States for MAIN Display 16 Brightness States for CAM Display 4 Brightness States for AUX Display 20-Lead (4mm × 4mm) QFN Package ■ Video/Camera Phones with QVGA+ Displays ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ U APPLICATIO S , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. Patents, including 6411531 The LTC ®3209-1/LTC3209-2 are highly integrated multidisplay LED controllers. These parts contain a high efficiency, low noise charge pump to provide power to MAIN, CAM and AUX LED displays. The LTC3209-1/ LTC3209-2 require only four small ceramic capacitors and one current set resistor to form a complete LED power supply and current controller. The maximum display currents are set by a single external resistor. Current for each LED is controlled by a precision internal current source. Dimming and On/Off for all displays is achieved via the I2C serial interface. 256 states are available for the MAIN display. Sixteen states are available for the CAM display and four states are available for the AUX display. The charge pump optimizes efficiency based on the voltage across the LED current sources. The part powers up in 1x mode and will automatically switch to boost mode whenever any enabled MAIN or CAM LED current source begins to enter dropout. The first dropout switches the part into 1.5x mode and a subsequent dropout switches the part into 2x mode. The part resets to 1x mode whenever a data bit is updated via the I2C port. The parts are available in a 4mm × 4mm 20-lead QFN package. U TYPICAL APPLICATIO LTC3209-1 6 MAIN/1 CAM Operation 2.2µF 2.2µF C1P C1M C2P C2M VBAT LTC3209-2 5 MAIN/2 CAM Operation 2.2µF 2.2µF MAIN CAM C1P C1M C2P C2M VBAT CPO VBAT1,2 RED 2.2µF 24.3k RED SCL I2C 6 CAMHL RREF CAM LTC3209-2 MAIN1-6 5 SDA CAM LOW HI MAIN 2.2µF SCL SDA 2.2µF CPO VBAT1,2 LTC3209-1 I2C 2.2µF AUX GND MAIN1-5 CAM 3209 TA01 LOW HI CAMHL RREF AUX GND 2 3209 TA02 24.3k 320912fa 1 LTC3209-1/LTC3209-2 W W U W ABSOLUTE AXI U RATI GS (Note 1) VBAT, DVCC, CPO to GND ............................... –0.3 to 6V SDA, SCL, CAMHL ..................... –0.3V to (DVCC + 0.3V) ICPO (Note 4)....................................................... 700mA IMAIN1-6 (Note 5) ................................................... 31mA IAUX (Note 5) ......................................................... 30mA ICAM1-2 (Note 5) .................................................. 250mA ICAM (Note 5) ...................................................... 500mA CPO, RREF Short-Circuit Duration ....................Indefinite Operating Temperature Range (Note 2) .. –40°C to 85°C Storage Temperature Range ................. –65°C to 125°C U W U PACKAGE/ORDER I FOR ATIO 13 CAMHL MAIN2 3 MAIN3 4 12 CAM MAIN3 4 MAIN4 5 11 DVCC MAIN4 5 7 8 9 10 MAIN5 MAIN6 AUX VBAT2 RREF 6 C2M C1M 15 SCL 14 SDA 13 CAMHL 21 12 CAM2 11 CAM1 6 7 8 9 10 DVCC MAIN1 2 RREF 14 SDA VBAT2 MAIN1 2 21 VBAT1 C1P CPO 1 AUX 15 SCL MAIN5 C1M VBAT1 C2P C1P C2M 20 19 18 17 16 20 19 18 17 16 CPO 1 MAIN2 3 C2P TOP VIEW TOP VIEW UF PACKAGE 20-LEAD (4mm × 4mm) PLASTIC QFN UF PACKAGE 20-LEAD (4mm ´ 4mm) PLASTIC QFN TJMAX = 125°C, θJA = 40°C/W EXPOSED PAD IS GND (PIN 21), MUST BE SOLDERED TO PCB TJMAX = 125°C, θJA = 40°C/W EXPOSED PAD IS GND (PIN 21), MUST BE SOLDERED TO PCB ORDER PART NUMBER UF PART MARKING ORDER PART NUMBER UF PART MARKING LTC3209EUF-1 32091 LTC3209EUF-2 32092 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBAT1,2 = 3.6V, DVCC = 3V, RREF = 24.3k, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted. PARAMETER CONDITIONS ● VBAT Operating Voltage IVBAT Operating Current MIN 2.9 ICPO = 0, 1x Mode, LED Disabled ICPO = 0, 1.5x Mode ICPO = 0, 2x Mode VBAT UVLO Threshold ● DVCC Operating Voltage DVCC Operating Current DVCC = 1.8V, Serial Port Idle MAX 4.5 ● V mA mA mA 1.5 V 1.5 4.5 V 1 µA 1 DVCC = 3V UNITS 0.4 2.7 4.5 ● DVCC UVLO Threshold VBAT Shutdown Current TYP 3 V 7 µA 320912fa 2 LTC3209-1/LTC3209-2 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBAT1,2 = 3.6V, DVCC = 3V, RREF = 24.3k, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted. PARAMETER White LED Current (MAIN1-6), 8-Bit Linear DAC CONDITIONS Full-Scale LED Current MAIN = 1V Minimum (1LSB) LED Current MAIN = 1V LED Current Matching Any Two MAIN Outputs at 50% FS LED Dropout Voltage Mode Switch Threshold, IMAINx = FS MIN ● 25 TYP MAX 28 31 UNITS mA µA 110 1 % 180 mV White LED Current (CAM), LTC3209-1, 4-Bit Linear DAC Full-Scale LED Current CAM = 1V Minimum (1LSB) LED Current CAM = 1V ● 360 LED Dropout Voltage Mode Switch Threshold, ICAM = FS White LED Current (CAM1-2), LTC3209-2, 4-Bit Linear DAC Full-Scale LED Current CAM = 1V Minimum (1LSB) LED Current CAM = 1V LED Current Matching CAM1-2 at 50% FS LED Dropout Voltage Mode Switch Threshold, ICAM = FS ● 180 400 440 mA 26.8 mA 400 mV 200 220 mA 13.3 mA 1 % 400 mV AUX LED Current, 2-Bit Linear DAC ● Full-Scale LED Current AUX = 1V 12.5 13.75 15 mA Minimum (1LSB) LED Current AUX = 1V 4.4 mA VOL IAUX = 1mA; C0, C1 = High 18 mV 1x Mode Output Impedance 1.5x Mode Output Impedance VBAT = 3V, VCPO = 4.2V (Note 3) 0.5 2.7 Ω Ω 2x Mode Output Impedance VBAT = 3V, VCPO = 4.8V (Note 3) 3.2 Ω CPO Voltage Regulation 1.5x Mode, ICPO = 2mA 2x Mode, ICPO = 2mA 4.6 5.1 V V 0.85 MHz Charge Pump (CPO) CLOCK Frequency SDA, SCL, CAMHL VIL (Low Level Input Voltage) ● VIH (High Level Input Voltage) ● 0.3 • DVCC V 0.4 V 0.7 • DVCC V VOL, Digital Output Low (SDA) IPULLUP = 3mA ● IIH SDA, SCL, CAMHL = DVCC ● –1 1 µA IIL SDA, SCL, CAMHL = 0V ● –1 1 µA 400 kHz 0.16 Serial Port Timing (Notes 6, 7) tSCL Clock Operating Frequency tBUF Bus Free Time Between Stop and Start Condition 1.3 µs tHD,STA Hold Time After (Repeated) Start Condition 0.6 µs tSU,STA Repeated Start Condition Setup Time 0.6 µs tSU,STO tHD,DAT(OUT) Stop Condition Setup Time Data Hold Time 0.6 0 tHD,DAT(IN) Input Data Hold Time tSU,DAT tLOW tHIGH tf tr 900 µs ns 0 ns Data Setup Time 100 ns Clock Low Period 1.3 µs Clock High Period Clock Data Fall Time Clock Data Rise Time 0.6 20 20 300 300 µs ns ns 320912fa 3 LTC3209-1/LTC3209-2 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBAT1,2 = 3.6V, DVCC = 3V, RREF = 24.3k, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted. PARAMETER tSP RREF VRREF RRREF CONDITIONS Spike Suppression Time ● RREF = 24.3k Reference Resistor Range Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC3209-1/LTC3209-2 are guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C ambient operating temperature range are assured by design, characterization and correlation with statistical process controls. MIN 50 TYP MAX UNITS ns 1.20 20 1.23 1.26 30 V kΩ Note 3: 1.5x mode output impedance is defined as (1.5VBAT – VCPO)/IOUT. 2x mode output impedance is defined as (2VBAT – VCPO)/IOUT. Note 4: Based on long term current density limitations. Assumes an operating duty cycle of ≤ 10% under absolute maximum conditions for duration less than 10 seconds. Max Charge Pump current for continuous operation is 300mA. Note 5: Based on long term current density limitations. Note 6: All values are referrenced to VIH and VIL levels. Note 7: Guaranteed by design. U W TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted Mode Switch Fast Dropout Times 1.5x Mode CPO Ripple 2x Mode CPO Ripple 2x 1.5x 1x VCPO 20mV/DIV AC COUPLED VCPO 1V/DIV VCPO 20mV/DIV AC COUPLED 320912 G01 1ms/DIV OPEN-LOOP OUTPUT RESISTANCE (Ω) SWITCH RESISTANCE (Ω) 0.60 VBAT = 3.6V VBAT = 3.3V 0.50 VBAT = 3.9V 0.45 0.40 0.35 –40 –15 10 35 TEMPERATURE (°C) 60 85 3209 G05 3.0 1.5x Mode CPO Voltage vs Load Current 4.8 VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2µF 2.8 2.6 2.4 2.2 2.0 –40 C2 = C3 = C4 = 2.2µF 4.6 CPO VOLTAGE (V) 3.2 320912 G03 500ns/DIV 1.5x Mode Charge Pump OpenLoop Output Resistance vs Temperature (1.5VBAT–VCPO)/ICPO ICPO = 200mA 0.55 320912 G02 500ns/DIV 1x Mode Switch Resistance vs Temperature 0.65 VBAT = 3.6V ICPO = 200mA CCPO = 2.2µF VBAT = 3.6V ICPO = 200mA CCPO = 2.2µF VBAT = 3.6V REGC C2 = Hi 4.4 3.6V 4.2 VBAT = 3V 3.1V 4.0 3.2V 3.3V 3.4V 3.8 3.5V 3.6 –15 10 35 TEMPERATURE (°C) 60 85 3209 G06 0 100 200 300 400 LOAD CURRENT (mA) 500 3209 G07 320912fa 4 LTC3209-1/LTC3209-2 U W TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted 2x Mode Charge Pump Open-Loop Output Resistance vs Temperature (2VBAT–VCPO)/ICPO 5.2 3.6 DVCC Shutdown Current vs DVCC Voltage 0.7 C2 = C3 = C4 = 2.2µF 5.1 3.4V 5.0 3.4 3.2 3.0 3.5V 4.9 4.8 3.3V 4.7 3.2V 4.6 3.1V 4.5 VBAT = 3V 4.4 2.8 –15 10 35 TEMPERATURE (°C) 60 4.2 85 100 0 300 400 200 LOAD CURRENT (mA) 3209 G08 TA = –40°C 0.5 TA = 85°C 0.4 0.3 TA = 25°C 0.2 0.1 3.9 3.6 3.3 DVCC VOLTAGE (V) 3 4.2 1x Mode No Load VBAT Current vs VBAT Voltage 1.5x Mode Supply Current vs ICPO (IVBAT–1.5ICPO) 30 400 DVCC = 3V 4.5 3209 G11 VBAT = 3.6V 380 5.0 360 VBAT CURRENT (µA) 4.5 TA = 85°C 4.0 3.5 TA = 25°C 3.0 TA = –40°C 2.5 SUPPLY CURRENT (mA) 5.5 0 2.7 500 3209 G09 VBAT Shutdown Current vs VBAT Voltage VBAT SHUTDOWN CURRENT (µA) VBAT = 3.6V 0.6 4.3 2.6 –40 340 320 300 280 260 20 10 240 2.0 220 1.5 2.7 0 200 3.9 3.6 3.3 VBAT VOLTAGE (V) 3 4.2 4.5 2.7 3.0 3.6 3.9 3.3 VBAT VOLTAGE (V) 4.2 3209 G12 400 VBAT = 3.6V CAM PIN CURRENT (mA) 20 10 200 300 400 LOAD CURRENT (mA) 500 LTC3209-1 CAM Pin Current vs Input Code LTC3209-1 CAM Pin Current vs CAM Pin Voltage 15 100 3209 G14 400 VBAT = 3.6V 360 300 CAM PIN CURRENT (mA) 25 0 4.5 3209 G13 2x Mode Supply Current vs ICPO (IVBAT–2ICPO) SUPPLY CURRENT (mA) DVCC SHUTDOWN CURRENT (µA) VBAT = 3V VCPO = 4.8V C2 = C3 = C4 = 2.2µF CPO VOLTAGE (V) OPEN-LOOP OUTPUT RESISTANCE (Ω) 3.8 2x Mode CPO Voltage vs Load Current 200 100 VBAT = 3.6V 320 280 240 200 160 120 80 5 40 0 0 100 300 400 200 LOAD CURRENT (mA) 500 3209 G15 0 0 0 0.2 0.6 0.8 0.4 CAM PIN VOLTAGE (V) 1.0 3209 G22 0 1 2 3 4 5 6 7 8 9 A B C D E F HEX CODE 3209 G23 320912fa 5 LTC3209-1/LTC3209-2 U W TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted LTC3209-1 CAM Pin Dropout Voltage vs CAM Pin Current 200 VBAT = 3.6V 200 VBAT = 3.6V 180 280 220 200 160 120 80 160 CAM PIN CURRENT (mA) 320 CAM PIN CURRENT (mA) CAM PIN DROPOUT VOLTAGE (mV) 400 360 120 80 40 160 140 120 100 80 60 20 200 100 300 CAM PIN CURRENT (mA) 0 0 400 0 0.2 0.6 0.8 0.4 CAM PIN VOLTAGE (V) 3209 G24 400 MAIN Pin Current vs Input Code 30 MAIN PIN CURRENT (mA) 280 220 200 160 120 80 MAIN PIN CURRENT (mA) 25 320 20 15 10 5 40 0 100 50 150 CAM PIN CURRENT (mA) 0 VBAT = 3.6V 0 200 0 0.2 1.0 0.4 0.6 0.8 MAIN PIN VOLTAGE (V) 3209 G24 16 180 120 100 80 60 40 100 90 EFFICIENCY (PLED/PIN) (%) AUX PIN CURRENT (mA) 140 12 10 8 6 4 2 20 0 0 5 15 20 25 10 MAIN PIN CURRENT (mA) 30 80 70 60 50 40 30 20 10 0 1 2 3 HEX CODE 3209 G27 0 10 20 30 40 50 60 70 80 90 A0 B0 C0D0 E0 F0 FF HEX CODE 6-LED MAIN Display Efficiency vs VBAT VBAT = 3.6V VAUX = 1V 14 160 VBAT = 3.6V 3209 G17 AUX Pin Current vs Input Code VBAT = 3.6V 0 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 3209 G26 MAIN Pin Dropout Voltage vs MAIN Pin Current 200 0 1 2 3 4 5 6 7 8 9 A B C D E F HEX CODE 3209 G17 MAIN Pin Current vs MAIN Pin Voltage VBAT = 3.6V 360 0 1.0 3209 G16 LTC3209-2 CAM Pin Dropout Voltage vs CAM Pin Current CAM PIN DROPOUT VOLTAGE (mV) VBAT = 3.6V 40 40 0 MAIN PIN DROPOUT VOLTAGE (V) LTC3209-2 CAM Pin Current vs Input Code LTC3209-2 CAM Pin Current vs CAM Pin Voltage 3209 G20 6 LEDS AT 15mA/LED (TYP VF AT 15mA = 3.2V) 0 3.0 3.2 3.4 3.6 3.8 VBAT (V) 4.0 4.2 4.4 3209 G21 320912fa 6 LTC3209-1/LTC3209-2 U U U PI FU CTIO S (LTC3209-1/LTC3209-2) CPO (Pin 1/Pin 1): Output of the Charge Pump Used to Power LEDs. A 2.2µF X5R or X7R ceramic capacitor should be connected to ground. MAIN1-6 (Pins 2, 3, 4, 5, 6, 7, LTC3209-1): Current Source Outputs for the MAIN Display White LEDs. The LEDs on the MAIN display can be set from 0mA to 28mA in 256 steps via software control and internal 8-bit linear DAC. Each output can be disabled externally by connecting the output to CPO. Setting data in REGA to 0 disables all MAIN outputs. MAIN1-5 (Pins 2, 3, 4, 5, 6, LTC3209-2): Current Source Outputs for the MAIN Display White LEDs. The LEDs on the MAIN display can be set from 0mA to 28mA in 256 steps via software control and internal 8-bit linear DAC. Each output can be disabled externally by connecting the output to CPO. Setting data in REGA to 0 disables all MAIN outputs. AUX (Pin 8/Pin 7): Current Source Output for the AUX Display LED. The LED current source can be set from 0mA to 13.75mA in 4 steps via software control and internal 2bit DAC. AUX does not have dropout sensing and cannot be disabled by connecting to CPO. This pin can also be used as an I2C controlled general purpose output. VBAT2,1 (Pins 9, 18/Pins 8, 18): Supply Voltage for the Entire Device. Two separate pins are used to isolate the charge pump from the analog sections to reduce noise. Both pins must be connected together externally and bypassed with a single 2.2µF low ESR ceramic capacitor close to VBAT1. VBAT2 may require a 0.1µF capacitor. RREF (Pin 10/Pin 9): This pin controls the maximum amount of LED current for all displays. The RREF voltage is 1.23V. An external 24.3k resistor to ground sets the reference currents for all display DACs and support circuits for nominal MAIN full-scale current of 28mA and total CAM full-scale current of 400mA. The value for RREF is limited to a range of 20k to 30k. DVCC (Pin 11/Pin 10): Supply Voltage for All Digital I/O Lines. This pin sets the logic reference level of the LTC3209-1/LTC3209-2. Decouple DVCC to GND with a 0.1µF capacitor. A UVLO circuit on the DVCC pin forces all registers to all 0s whenever DVCC is below the UVLO threshold. CAM1-2 (Pins 11, 12, LTC3209-2): Current Source Outputs for the CAM1 and CAM2 Display White LEDs. The LEDs on the two CAM displays can each be set from 0mA to 200mA in 16 steps via software control and internal 4-bit linear DAC. Two 4-bit registers are available. One is used to program the high camera current and the second the low camera current. These registers can be selected via the serial port or the CAMHL pin. Each output can be disabled by connecting the output to CPO. Setting data in REGB to 0 disables both CAM outputs. (See Applications Information). CAM (Pin 12, LTC3209-1): Current Source Output for the CAM Display White LED. The LED on the CAM display can be set from 0mA to 400mA in 16 steps via software control and internal 4-bit linear DAC. Two 4-bit registers are available. One is used to program the high camera current and the second the low camera current. These registers can be selected via the serial port or the CAMHL pin. Each output can be disabled by connecting the output to CPO. Setting data in REGB to 0 disables the CAM output. (See Applications Information). CAMHL (Pin 13/Pin 13): This pin selects CAM high current register when asserted high and CAM low current register when low. The high to low transition automatically resets the charge pump mode to 1x. SDA (Pin 14/Pin 14): I2C Data Input for the Serial Port. Serial data is shifted in one bit per clock to control the LTC3209-1/LTC3209-2. The logic level is referenced to DVCC. SCL (Pin 15/Pin 15): I2C Clock Input. The logic level for SCL is referenced to DVCC. C1P, C2P, C1M, C2M (Pins 20, 19, 17, 16/Pins 20, 19, 17, 16): Charge Pump Flying Capacitor Pins. A 2.2µF X7R or X5R ceramic capacitor should be connected from C1P to C1M and C2P to C2M. Exposed Pad (Pin 21/Pin 21): System Ground. Connect Exposed Pad to PCB ground plane. 320912fa 7 LTC3209-1/LTC3209-2 W BLOCK DIAGRA C1P C1M C2P C2M GND 850kHz OSCILLATOR CPO CHARGE PUMP VBAT1 ENABLE CP – VBAT2 + MAIN1 + MAIN2 MAIN3 – MAIN CURRENT SOURCES 6 MAIN4 MAIN5 RREF DVCC CAMHL MAIN6 (LTC3209-1) 1.23V CAM CURRENT SOURCES CAM1 CONTROL LOGIC MASTER/SLAVE REG SDA 2 CAM2 (LTC3209-2) AUX CURRENT SOURCE AUX SHIFT REGISTER SCL 320912 BD 320912fa 8 LTC3209-1/LTC3209-2 U OPERATIO The LTC3209-1 has 6 MAIN outputs, 1 CAM output and 1 AUX output. The LTC3209-2 has 5 MAIN outputs, 2 CAM outputs and 1 AUX output. Power Management The LTC3209-1/LTC3209-2 use a switched capacitor charge pump to boost CPO to as much as 2 times the input voltage up to 5.1V. The part starts up in 1x mode. In this mode, VBAT is connected directly to CPO. This mode provides maximum efficiency and minimum noise. The LTC3209-1/LTC3209-2 will remain in 1x mode until a MAIN or CAM LED current source drops out. Dropout occurs when a current source voltage becomes too low for the programmed current to be supplied. When dropout is detected, the LTC3209-1/LTC3209-2 will switch into 1.5x mode. The CPO voltage will then start to increase and will attempt to reach 1.5x VBAT up to 4.6V. Any subsequent dropout will cause the part to enter the 2x mode. The CPO voltage will attempt to reach 2x VBAT up to 5.1V. The part will be reset to 1x mode whenever a DAC data bit is updated via the I2C port or on the falling edge of the CAMHL signal. A 2-phase nonoverlapping clock activates the charge pump switches. In the 2x mode the flying capacitors are charged on alternate clock phases from VBAT to minimize input current ripple and CPO voltage ripple. In 1.5x mode the flying capacitors are charged in series during the first clock phase and stacked in parallel on VBAT during the second phase. This sequence of charging and discharging the flying capacitors continues at a constant frequency of 850kHz. The currents delivered by the LED current sources are controlled by an associated DAC. Each DAC is programmed via the I2C port. Soft-Start Initially, when the part is in shutdown, a weak switch connects VBAT1 to CPO. This allows VBAT1 to slowly charge the CPO output capacitor and prevent large charging currents to occur. The LTC3209-1/LTC3209-2 also employs a soft-start feature on its charge pump to prevent excessive inrush current and supply droop when switching into the step-up modes. The current available to the CPO pin is increased linearly over a typical period of 125µs. Soft-start occurs at the start of both 1.5x and 2x mode changes. Charge Pump Strength When the LTC3209-1/LTC3209-2 operate in either 1.5x mode or 2x mode, the charge pump can be modeled as a Thevenin-equivalent circuit to determine the amount of current available from the effective input voltage and effective open-loop output resistance, ROL (Figure 1). ROL is dependent on a number of factors including the switching term, 1/(2fOSC • CFLY), internal switch resistances and the nonoverlap period of the switching circuit. However, for a given ROL, the amount of current available will be directly proportional to the advantage voltage of 1.5VBAT - CPO for 1.5x mode and 2VBAT - CPO for 2x mode. ROL + – + CPO 1.5VBAT OR 2VBAT – 320912 F01 Figure 1. Charge Pump Thevenin Equivalent Open-Loop Circuit 320912fa 9 LTC3209-1/LTC3209-2 U OPERATIO Consider the example of driving white LEDs from a 3.1V supply. If the LED forward voltage is 3.8V and the current sources require 100mV, the advantage voltage for 1.5x mode is 3.1V • 1.5 – 3.8V – 0.1V or 750mV. Notice that if the input voltage is raised to 3.2V, the advantage voltage jumps to 900mV—a 20% improvement in available strength. From Figure 1, for 1.5x mode the available current is given by: IOUT = 1.5VBAT – VCPO ROL For 2x mode, the available current is given by: 2VBAT – VCPO ROL OPEN-LOOP OUTPUT RESISTANCE (Ω) 3.2 3.0 2.8 2.6 2.4 2.2 –15 10 35 TEMPERATURE (°C) Shutdown Current Shutdown occurs when all the current source data bits have been written to zero or when DVCC is below the DVCC UVLO threshold. Although the LTC3209-1/LTC3209-2 is designed to have very low shutdown current, it will draw about 3µA from VBAT when in shutdown. Internal logic ensures that the LTC3209-1/LTC3209-2 is in shutdown when DVCC is grounded. Note, however that all of the logic signals that are referenced to DVCC (SCL, SDA, CAMHL) will need to be at DVCC or below (i.e., ground) to avoid violation of the absolute maximum specifications on these pins. 3.8 VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2µF 2.0 –40 Typical values of ROL as a function of temperature are shown in Figures 2 and 3. OPEN-LOOP OUTPUT RESISTANCE (Ω) IOUT = Notice that the advantage voltage in this case is 3.1V • 2 – 3.8V – 0.1V = 2.3V. ROL is higher in 2x mode but a significant overall increase in available current is achieved. 60 85 3209 G06 Figure 2. Typical 1.5x ROL vs Temperature 3.6 VBAT = 3V VCPO = 4.8V C2 = C3 = C4 = 2.2µF 3.4 3.2 3.0 2.8 2.6 –40 –15 10 35 TEMPERATURE (°C) 60 85 3209 G08 Figure 3. Typical 2x ROL vs Temperature 320912fa 10 LTC3209-1/LTC3209-2 U OPERATIO Serial Port Camera Current Sources The microcontroller compatible I2C serial port provides all LTC3209-1 of the command and control inputs for the LTC3209-1/ LTC3209-2. Data on the SDA input is loaded on the rising edge of SCL. D7 is loaded first and D0 last. There are three data registers and one address register. Once all address bits have been clocked into the address register acknowledge occurs. After the data registers have been written a load pulse is created after the stop bit. The load pulse transfers all of the data held in the data registers to the DAC registers. At this point the LED current will be changed to the new settings. The serial port uses static logic registers so there is no minimum speed at which it can be operated. MAIN Current Sources LTC3209-1 There are six MAIN current sources. These current sources have an 8-bit linear DAC for current control. For RREF = 24.3k, the output current range is 0mA to 28mA in 256 steps. The current sources are disabled when a block receives an all zero data word. The supply current for that block is reduced to zero. In addition unused LED outputs can be connected to CPO to turn off the current source output and reduce the operating current to typically 10µA. LTC3209-2 There are five MAIN current sources. These current sources have an 8-bit linear DAC for current control. For RREF = 24.3k, the output current range is 0mA to 28mA in 256 steps. The current sources are disabled when a block receives an all zero data word. The supply current for that block is reduced to zero. In addition unused LED outputs can be connected to CPO to turn off the current source output and reduce the operating current to typically 10µA. There is one CAM current source. This current source has a 4-bit linear DAC for current control. The output current range is 0mA to 400mA in 16 steps (RREF = 24.3k). The current source is disabled when the block receives an all zero data word. The supply current for the block is reduced to zero. In addition, the LED output can be connected to CPO to turn off the current source output and reduce operating current to typically 10µA. This pin cannot be allowed to float if unused since dropout will be erroneously detected. LTC3209-2 There are two CAM current sources. These current sources have a 4-bit linear DAC for current control. The output current range of each current source is 0mA to 200mA in 16 steps (RREF = 24.3k). The current sources are disabled when the block receives an all zero data word. The supply current for the block is reduced to zero. In addition unused LED outputs can be connected to CPO to turn off the current source output and reduce the operating current to typically 10µA. These pins cannot be allowed to float if unused since dropout will be erroneously detected. Auxiliary Current Source There is one AUX current source. This current source has a 2-bit Linear DAC for current control. The output current range is 0mA to 13.75mA in 4 steps (OFF, 33%, 67%, 100%). The AUX output does not have dropout detection and cannot be disabled when connected to CPO. The current source is disabled when the block receives an all zero data word and the supply current for the block is reduced to zero. This output can also be used as an I2C controlled digital open-drain general purpose output. 320912fa 11 LTC3209-1/LTC3209-2 U OPERATIO CAMHL The CAMHL pin quickly selects the camera high register for flash applications without reaccessing the I2C port. When low the CAM current range will be controlled by the camera low 4-bit register. When CAMHL is asserted high the current range will be set by the camera high 4-bit register. The dropout delay is reduced from 150ms to 2ms when CAMHL is asserted high so that the charge pump can quickly change modes if required. When CAMHL is asserted from high to low the charge pump mode is reset to 1x. Thermal Protection The LTC3209-1/LTC3209-2 have built-in overtemperature protection. At internal die temperatures of around 150°C thermal shutdown will occur. This will disable all of the current sources and charge pump until the die has cooled by about 15°C. This thermal cycling will continue until the fault has been corrected. RREF Current Set Resistor The current set resistor is connected between the RREF pin and ground. This resistor sets the full-scale current for all three displays (MAIN, CAM and AUX) according to the following equations: MAIN = 1.23V • 550 RREF CAM = 1.23V • 7900 RREF (LTC32009-1) CAM = 1.23V • 3950 RREF (LTC3209-2) AUX = 1.23V • 272 RREF A 24.3k, 1% resistor provides full-scale currents of 28mA for the MAIN; 400mA (total) current for CAM and 13.75mA for AUX current sources. This input is protected against shorts to ground or low value resistors