LTC3209EUF-2

LTC3209-1/LTC3209-2 600mA Main/Camera LED Controller DESCRIPTIO 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. 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 APPLICATIO S ■ Video/Camera Phones with QVGA+ Displays , 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 TYPICAL APPLICATIO 2.2µF 2.2µF LTC3209-1 6 MAIN/1 CAM Operation 2.2µF LTC3209-2 5 MAIN/2 CAM Operation 2.2µF C1P C1M C2P C2M VBAT 2.2µF VBAT1,2 CPO 2.2µF MAIN CAM VBAT RED 2.2µF C1P C1M C2P C2M VBAT1,2 LTC3209-2 SCL CPO LTC3209-1 SCL I2C 6 SDA MAIN1-6 CAM LOW HI CAMHL RREF 24.3k AUX GND 3209 TA01 I2C SDA MAIN1-5 CAM 2 LOW HI CAMHL RREF 24.3k AUX GND U 5 U U 2.2µF MAIN CAM RED 3209 TA02 320912fa 1 LTC3209-1/LTC3209-2 ABSOLUTE (Note 1) AXI U RATI GS 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 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 PACKAGE/ORDER I FOR ATIO TOP VIEW VBAT1 C1M C2M C1P C2P VBAT1 C1M RREF 20 19 18 17 16 CPO 1 MAIN1 2 MAIN2 3 MAIN3 4 MAIN4 5 6 MAIN5 20 19 18 17 16 15 SCL 14 SDA CPO 1 MAIN1 2 MAIN2 3 MAIN3 4 MAIN4 5 6 7 8 9 10 21 15 SCL 14 SDA 13 CAMHL 12 CAM2 11 CAM1 21 13 CAMHL 12 CAM 11 DVCC 7 MAIN6 8 AUX 9 10 VBAT2 RREF MAIN5 AUX 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 LTC3209EUF-1 UF PART MARKING 32091 ORDER PART NUMBER LTC3209EUF-2 VBAT2 DVCC C2M C1P C2P 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. 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 VBAT Operating Voltage IVBAT Operating Current ICPO = 0, 1x Mode, LED Disabled ICPO = 0, 1.5x Mode ICPO = 0, 2x Mode ● ELECTRICAL CHARACTERISTICS CONDITIONS ● VBAT UVLO Threshold DVCC Operating Voltage DVCC Operating Current DVCC UVLO Threshold VBAT Shutdown Current DVCC = 3V ● DVCC = 1.8V, Serial Port Idle 2 U U W WW U W TOP VIEW UF PART MARKING 32092 MIN 2.9 TYP 0.4 2.7 4.5 1.5 MAX 4.5 UNITS V mA mA mA V 1.5 1 3 4.5 1 7 V µA V µA 320912fa ● LTC3209-1/LTC3209-2 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 Full-Scale LED Current Minimum (1LSB) LED Current LED Current Matching LED Dropout Voltage Full-Scale LED Current Minimum (1LSB) LED Current CONDITIONS MAIN = 1V MAIN = 1V Any Two MAIN Outputs at 50% FS Mode Switch Threshold, IMAINx = FS CAM = 1V CAM = 1V ● ● ELECTRICAL CHARACTERISTICS MIN 25 TYP 28 110 1 180 MAX 31 UNITS mA µA % mV White LED Current (CAM), LTC3209-1, 4-Bit Linear DAC 360 400 26.8 400 ● 440 mA mA mV LED Dropout Voltage Mode Switch Threshold, ICAM = FS White LED Current (CAM1-2), LTC3209-2, 4-Bit Linear DAC Full-Scale LED Current Minimum (1LSB) LED Current LED Current Matching LED Dropout Voltage AUX LED Current, 2-Bit Linear DAC Full-Scale LED Current Minimum (1LSB) LED Current VOL Charge Pump (CPO) 1x Mode Output Impedance 1.5x Mode Output Impedance 2x Mode Output Impedance CPO Voltage Regulation CLOCK Frequency SDA, SCL, CAMHL VIL (Low Level Input Voltage) VIH (High Level Input Voltage) VOL, Digital Output Low (SDA) IIH IIL Serial Port Timing (Notes 6, 7) tSCL tBUF tHD,STA tSU,STA tSU,STO tHD,DAT(OUT) tHD,DAT(IN) tSU,DAT tLOW tHIGH tf tr Clock Operating Frequency Bus Free Time Between Stop and Start Condition Hold Time After (Repeated) Start Condition Repeated Start Condition Setup Time Stop Condition Setup Time Data Hold Time Input Data Hold Time Data Setup Time Clock Low Period Clock High Period Clock Data Fall Time Clock Data Rise Time 1.3 0.6 0.6 0.6 0 0 100 1.3 0.6 20 20 IPULLUP = 3mA SDA, SCL, CAMHL = DVCC SDA, SCL, CAMHL = 0V ● ● ● ● ● CAM = 1V CAM = 1V CAM1-2 at 50% FS Mode Switch Threshold, ICAM = FS AUX = 1V AUX = 1V IAUX = 1mA; C0, C1 = High 180 200 13.3 1 400 220 mA mA % mV ● 12.5 13.75 4.4 18 0.5 2.7 3.2 4.6 5.1 0.85 15 mA mA mV Ω Ω Ω V V MHz VBAT = 3V, VCPO = 4.2V (Note 3) VBAT = 3V, VCPO = 4.8V (Note 3) 1.5x Mode, ICPO = 2mA 2x Mode, ICPO = 2mA 0.3 • DVCC 0.7 • DVCC 0.16 –1 –1 0.4 1 1 400 V V V µA µA kHz µs µs µs µs ns ns ns µs µs ns ns 320912fa 900 300 300 3 LTC3209-1/LTC3209-2 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 ● ELECTRICAL CHARACTERISTICS MIN 50 1.20 20 TYP MAX UNITS ns V kΩ 1.23 1.26 30 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. 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. TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted Mode Switch Fast Dropout Times 2x 1.5x 1x VCPO 1V/DIV VBAT = 3.6V REGC C2 = Hi 1ms/DIV 320912 G01 1x Mode Switch Resistance vs Temperature 0.65 0.60 SWITCH RESISTANCE (Ω) ICPO = 200mA OPEN-LOOP OUTPUT RESISTANCE (Ω) 0.55 0.50 0.45 0.40 0.35 –40 VBAT = 3.6V VBAT = 3.3V VBAT = 3.9V 2.8 2.6 2.4 2.2 2.0 –40 CPO VOLTAGE (V) –15 10 35 TEMPERATURE (°C) 4 UW 60 85 3209 G05 1.5x Mode CPO Ripple 2x Mode CPO Ripple VCPO 20mV/DIV AC COUPLED VBAT = 3.6V ICPO = 200mA CCPO = 2.2µF 500ns/DIV 320912 G02 VCPO 20mV/DIV AC COUPLED VBAT = 3.6V ICPO = 200mA CCPO = 2.2µF 500ns/DIV 320912 G03 1.5x Mode Charge Pump OpenLoop Output Resistance vs Temperature (1.5VBAT–VCPO)/ICPO 3.2 3.0 VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2µF 4.8 4.6 4.4 4.2 1.5x Mode CPO Voltage vs Load Current C2 = C3 = C4 = 2.2µF 3.6V VBAT = 3V 3.1V 4.0 3.2V 3.3V 3.4V 3.8 3.5V 3.6 0 100 200 300 400 LOAD CURRENT (mA) 500 3209 G07 –15 10 35 TEMPERATURE (°C) 60 85 3209 G06 320912fa LTC3209-1/LTC3209-2 TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted 2x Mode Charge Pump Open-Loop Output Resistance vs Temperature (2VBAT–VCPO)/ICPO 3.8 OPEN-LOOP OUTPUT RESISTANCE (Ω) 3.6 3.4 3.2 3.0 2.8 DVCC SHUTDOWN CURRENT (µA) VBAT = 3V VCPO = 4.8V C2 = C3 = C4 = 2.2µF CPO VOLTAGE (V) 2.6 –40 –15 10 35 TEMPERATURE (°C) VBAT Shutdown Current vs VBAT Voltage 5.5 DVCC = 3V 400 380 VBAT SHUTDOWN CURRENT (µA) 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 2.7 3 3.9 3.6 3.3 VBAT VOLTAGE (V) 4.2 4.5 3209 G12 VBAT CURRENT (µA) TA = 85°C 340 320 300 280 260 240 220 200 2.7 3.0 3.6 3.9 3.3 VBAT VOLTAGE (V) 4.2 4.5 3209 G13 SUPPLY CURRENT (mA) TA = 25°C TA = – 40°C 2x Mode Supply Current vs ICPO (IVBAT–2ICPO) 25 VBAT = 3.6V 400 CAM PIN CURRENT (mA) CAM PIN CURRENT (mA) 20 SUPPLY CURRENT (mA) 15 10 5 0 0 100 300 400 200 LOAD CURRENT (mA) UW 60 85 3209 G08 2x Mode CPO Voltage vs Load Current 5.2 5.1 5.0 4.9 4.8 4.7 4.6 4.5 4.4 4.3 4.2 0 100 300 400 200 LOAD CURRENT (mA) 500 3209 G09 DVCC Shutdown Current vs DVCC Voltage 0.7 VBAT = 3.6V TA = – 40°C TA = 85°C 0.4 0.3 0.2 0.1 0 2.7 TA = 25°C C2 = C3 = C4 = 2.2µF 3.4V 3.5V 0.6 0.5 3.3V 3.2V 3.1V VBAT = 3V 3 3.9 3.6 3.3 DVCC VOLTAGE (V) 4.2 4.5 3209 G11 1x Mode No Load VBAT Current vs VBAT Voltage 30 1.5x Mode Supply Current vs ICPO (IVBAT–1.5ICPO) VBAT = 3.6V 360 20 10 0 0 100 200 300 400 LOAD CURRENT (mA) 500 3209 G14 LTC3209-1 CAM Pin Current vs CAM Pin Voltage VBAT = 3.6V 400 360 320 280 240 200 160 120 80 40 LTC3209-1 CAM Pin Current vs Input Code VBAT = 3.6V 300 200 100 500 3209 G15 0 0 0 0.2 0.6 0.8 0.4 CAM PIN VOLTAGE (V) 1.0 3209 G22 0123456789ABCDEF HEX CODE 3209 G23 320912fa 5 LTC3209-1/LTC3209-2 TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted LTC3209-1 CAM Pin Dropout Voltage vs CAM Pin Current 400 CAM PIN DROPOUT VOLTAGE (mV) 360 320 VBAT = 3.6V CAM PIN CURRENT (mA) 280 220 200 160 120 80 40 0 0 200 100 300 CAM PIN CURRENT (mA) 400 3209 G24 CAM PIN CURRENT (mA) LTC3209-2 CAM Pin Dropout Voltage vs CAM Pin Current 400 CAM PIN DROPOUT VOLTAGE (mV) 360 320 280 220 200 160 120 80 40 0 VBAT = 3.6V MAIN PIN CURRENT (mA) 20 15 10 5 0 0 0.2 VBAT = 3.6V 0.4 0.6 0.8 MAIN PIN VOLTAGE (V) 1.0 3209 G26 0 100 50 150 CAM PIN CURRENT (mA) 200 3209 G24 MAIN PIN CURRENT (mA) MAIN Pin Dropout Voltage vs MAIN Pin Current 200 VBAT = 3.6V 16 14 AUX PIN CURRENT (mA) 12 10 8 6 4 2 0 0 5 15 20 25 10 MAIN PIN CURRENT (mA) 30 3209 G27 MAIN PIN DROPOUT VOLTAGE (V) 180 160 140 120 100 80 60 40 20 0 EFFICIENCY (PLED/PIN) (%) 6 UW LTC3209-2 CAM Pin Current vs CAM Pin Voltage 200 VBAT = 3.6V 200 180 160 160 140 120 100 80 60 40 20 0 0 0.2 0.6 0.8 0.4 CAM PIN VOLTAGE (V) 1.0 3209 G16 LTC3209-2 CAM Pin Current vs Input Code VBAT = 3.6V 120 80 40 0 0123456789ABCDEF HEX CODE 3209 G17 MAIN Pin Current vs MAIN Pin Voltage 30 25 MAIN Pin Current vs Input Code 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 VBAT = 3.6V 0 10 20 30 40 50 60 70 80 90 A0 B0 C0D0 E0 F0 FF HEX CODE 3209 G17 AUX Pin Current vs Input Code VBAT = 3.6V VAUX = 1V 100 90 80 70 60 50 40 30 20 10 6-LED MAIN Display Efficiency vs VBAT 6 LEDS AT 15mA/LED (TYP VF AT 15mA = 3.2V) 3.0 3.2 3.4 3.6 3.8 VBAT (V) 4.0 4.2 4.4 0 1 HEX CODE 2 3 3209 G20 0 3209 G21 320912fa LTC3209-1/LTC3209-2 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. U U U 320912fa 7 LTC3209-1/LTC3209-2 BLOCK DIAGRA 850kHz OSCILLATOR VBAT1 – VBAT2 + MAIN1 + – RREF DVCC CAMHL 1.23V CAM CURRENT SOURCES CONTROL LOGIC 2 MAIN CURRENT SOURCES 6 SDA SCL 320912 BD 8 W C1P C1M C2P C2M GND CPO CHARGE PUMP ENABLE CP MAIN2 MAIN3 MAIN4 MAIN5 MAIN6 (LTC3209-1) CAM1 CAM2 (LTC3209-2) AUX CURRENT SOURCE AUX MASTER/SLAVE REG SHIFT REGISTER 320912fa LTC3209-1/LTC3209-2 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. U 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 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: IOUT = 2VBAT – VCPO ROL 3.2 OPEN-LOOP OUTPUT RESISTANCE (Ω) 3.0 2.8 2.6 2.4 2.2 OPEN-LOOP OUTPUT RESISTANCE (Ω) VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2µF 2.0 –40 Figure 2. Typical 1.5x ROL vs Temperature 10 U 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. Typical values of ROL as a function of temperature are shown in Figures 2 and 3. 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 3.6 3.4 3.2 3.0 2.8 2.6 –40 VBAT = 3V VCPO = 4.8V C2 = C3 = C4 = 2.2µF –15 10 35 TEMPERATURE (°C) 60 85 3209 G06 –15 10 35 TEMPERATURE (°C) 60 85 3209 G08 Figure 3. Typical 2x ROL vs Temperature 320912fa LTC3209-1/LTC3209-2 OPERATIO Serial Port The microcontroller compatible I2C serial port provides all 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. U Camera Current Sources LTC3209-1 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 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 = CAM = CAM = AUX = 1.23V • 550 RREF (LTC3209-1) (LTC3209-2) 1.23V • 7900 RREF 1.23V • 3950 RREF 1.23V • 272 RREF 12 U 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