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SP7682/SP7682A Backlight and Flash Driver in QFN 3mm x 3mm
FEATURES Output current up to 500mA for Flash LED Up to 94% efficiency in 1x mode Triple mode 1x, 1.5x and 2x charge pump Built-in current setting DAC SP7682 - I2C serial interface VIN SP7682A - Single Line Programmable Serial Interface PGND 2.4MHz switching frequency Flash LED output current adjustable in 10mA steps to 500mA EN Backlight LED output current adjustable in 0.5mA steps to 31.5mA SCL (SETFL) Power-saving shutdown mode of 1A Time Out function to protect the LED in Flash mode (2s) Thermal shutdown protection Built-in over-voltage and over-current protection Automatic soft start limits in-rush current Lead Free, RoHS Compliant Packaging: Space saving 16-pin 3X3mm QFN package C1+ C2+ VOUT SGND LED 1 LED 2 SDA (SETBL) FLASH LED 4 LED 3 DESCRIPTION The SP7682 or SP7682A provides a complete LED backlight and flash solution that is designed to drive 4 low current LEDs for backlighting and a single channel high current output for a LED flash. The SP7682 and SP7682A have serial interfaces that can program the backlight LED current in steps of 0.5mA up to 31.5mA and flash LED current in steps of 10mA up to 500mA. The SP7682A uses two single line serial interfaces for programming the backlight current and flash current. The SP7682 uses an I2C serial interface which also allows programming active, standby and shutdown states, selecting flash timeout periods and switching individual LEDs for the backlight. The data is loaded into internal registers upon power up and stored while in shutdown. When the chip is enabled, the stored values set the LED currents. The SP7682/SP7682A automatically detects 1x, 1.5x or 2x operation for optimal efficiency. TYPICAL APPLICATION CIRCUIT C1 1uF VIN = 2.7V to 5.5V VIN C1+ C1- C2+ CIN SDA (SETBL) SCL (SETFL) 4.7uF SDA (SETBL) SCL (SETFL) FLASH Flash C2VOUT COUT 2.2uF C2 1uF C1C2-
SP7682 (SP7682A)
EN EN LED1 LED2 LED3 LED4 PGND SGND
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ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. VCC, Enable, SCL, SDA, VFLASH, VLED..............-0.3V to 6.0V 1 Power Dissipation...............................Internally limited Storage Temperature............................-65 C to 150 C Junction Temperature................................-40C to +125C ESD @ LED pins.......................................+/-4kV HBM ESD all other pins......................................+/-2kV HBM
ELECTRICAL SPECIFICATIONS Unless otherwise specified: VIN =3.6V, CIN=4.7uF, COUT=2.2uF, CFLY=1uF, TA = -40C to +85C, Tj=-40C to +125C. Bold values apply over the full operating temperature range (-40C to 85C).
PARAMETER Operating VIN Range Operating Input Current Quiescent Current Shutdown Supply Current ILED Voltage for DAC=000000 ILED for DAC=000001 ILED for DAC=111111 IFLASH for DAC=000001 IFLASH for DAC=110010 Current DAC Resolution Backlight Current DAC LSB Flash Current DAC LSB DAC Current Accuracy Switching Frequency Equivalent Resistance, 1x mode Equivalent Resistance, 1.5x mode Equivalent Resistance, 2x mode LEDx Pin dropout voltage FLASH Pin dropout voltage Thermal Regulation Thermal Shutdown Die Temperature Thermal Shutdown Hysteresis Over-current Protection Over-voltage protection Settle time (TS) after last count SDA, SCL, SETB, SETFL input logic low voltage SDA, SCL, SETB, SETFL input logic high voltage Turn-off time (TOFF) into shutdown Time Duration before standby, SP7682 Time Duration before standby, SP7682A Enable logic low voltage Enable logic high voltage 150 0.7 5.4 160 20 1.2 6.0 100 0.4 1.6 50 2 1 1.6 4 2 6 3 0.4 -7 1.9 2.4 1.0 10 8 0.25 0.25 0.01 170 465 MIN 2.7 2 25 0.01 0.5 31.5 10 500 6 0.5 10 7 2.9 1.8 535 1 0 34.8 TYP MAX 5.5 UNITS V mA A A mA mA mA mA mA Bit mA mA % MHz Ohm Ohm Ohm V V %/C C C A V s V V s s s V V EN pin high to low TD0=TD1=0V, IFLASH>ITHRESHOLD (defined by bits TOUT0, TOUT1) IFLASH>ITHRESHOLD = 230mA Driver shutdown Driver enabled Driver turns off Driver turns on again Vout =0V Vout open To 1x mode from STANDBY mode Iout=200mA Iout=80mA Iout=500mA ILED=20mA, measure mode switching IFLASH=200mA, measure mode switching 5mA< ILED<30mA, 80mA< IFLASH<500mA Standby Mode VEN = 0V (shutdown), Ta = 25C Measure LED1-LED4 and FLASH pins Measure current into LED1-LED4 Measure current into LED1-LED4 Measure current into FLASH Measure current into FLASH CONDITIONS
30.2
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I2C SPECIFICATIONS PARAMETER
Serial Clock Frequency Bus Free Time Between a STOP and a START Hold Time, Repeated START Condition Repeated START Condition Setup Time STOP Condition Setup Time Data Hold Time Input Data Hold Time Data Setup Time SCL Clock Low Period SCL Clock High Period Rise Time of Both SDA and SCL Signals, receiving Fall Time of Both SDA and SCL Signals, Receiving Fall Time of SDA Transmitting Pulse Width of Spike Suppressed Capacitive Load for Each Bus Line IC startup time after UVLO clears
SYMBOL
fSCL tBUF t HD_STA t SU,STA tSU,STO tHD,DAT(OUT) tHD,DAT(IN) tSU,DAT tLOW tHIGH tR tF tF.TX tSP Cb tSRT
MIN
1.3 0.6 0.6 0.6 225 0 100 1.3 0.6 20+ 0.1Cb 20+ 0.1Cb 20+ 0.1Cb 0 400 1
TYP
MAX
400
UNITS
kHz s s s s ns ns ns s s ns ns ns ns pF s
CONDITIONS
900 900
300 300 250 50 400 1
(Notes2, 3) (Note2, 3) (Note2, 3, 4) (Note5) (Note 2) (Note 2)
Note 1: All parameters tested at TA=25 C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design. Note 3: Cb = total capacitance of one bus line in pF. tR and tF measured between 0.3 x VDD and 0.7 x VDD. Note 4: ISINK 6mA. Cb =total capacitance of one bus line in pF. tR and tF measured between 0.3 x VDD and 0.7 VDD. Note5: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns.
SP7682A: SINGLE LINE PROGRAMMABLE SERIAL INTERFACE SPECIFICATIONS
PARAMETER SET_BL, SET_FL logic low threshold SET_BL, SET_FL logic high threshold SET_BL, SET_FL logic low time SET_BL, SET_FL logic high time SET_BL shutdown delay SET_FL shutdown delay SYMBOL VIL VIH tLO tHI tSHDN tSHDN MIN 1.6 0.5 225 325 0.5 500 500 TYP 0.4 MAX UNITS V V s s s s CONDITIONS
250 800 700
VSET_BL < 0.4V VSET_BL > 1.6V VSET_BL < 0.4V VSET_FL < 0.4V
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PIN DESCRIPTION
PIN # 1 2 3 4, 5
PIN NAME VIN PGND EN SCL,SDA (SP7682) SETFL
(SP7682A)
DESCRIPTION Power supply input. Place a 4.7uF decoupling capacitor next to this pin. Power ground pin. Enable/Shutdown (Logic high = enable, logic low = shutdown). Used to immediately disable the driver and reset the output current level. These pins connect to the I2C bus. Multiple functions can be programmed through his interface. Used to serially program the Flash LED current Used to serially program the Backlight LED's output current High current internal current source. Connect a high brightness LED between this pin and VOUT. The value of the current can be programmed via the I2C interface between 0mA and 500mA with 10mA increments. During operation this pin is monitored for dropout. When dropout condition detected the charge pump increases operation mode from 1x to 1.5x to 2x. If the FLASH current is set to above the maximum threshold the time-out protection circuit is activated. After the maximum time of constant operation, FLASH current is reduced to zero. Internal current source for LCD backlight. Connect an LED between each of these pins and VOUT. The value of the current can be programmed via the I2C interface between 0mA and 32mA with 0.5mA increments. During operation this pin is monitored for dropout. When dropout condition detected the charge pump increases operation mode from 1x to 1.5x to 2x. If any of the LEDs are not used connect the corresponding pin to Vout. Signal ground pin. Output voltage of the internal charge pump. Connect the LEDs between this pin and the corresponding internal current source. Connect a 2.2uF capacitor between VOUT and PGND. Connect external flying capacitors between these pins. Connect thermal pad to PGND pin.
4 5
SETBL
(SP7682A)
6
FLASH
7,8,9, 10 11 12 13,14, 15,16 -
LED1LED4 SGND VOUT C2+, C2-, C1+, C1Thermal Pad
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FUNCTIONAL DIAGRAM
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THEORY OF OPERATION
The SP7682 and SP7682A are charge pump based backlight and flash LED drivers with I2C and serial single wire interface (SWI) control respectively. The SP7682 family provides very accurate current drive capability for up-to four backlight LED channels and a flash LED. The backlight LED current can be set through a serial interface controlled 6-bit current DAC with 0.5mA steps, up to 31.5mA. Similarly, FLASH LED current is set thru a serial interface controlled 6-bit current DAC with 10mA steps, up to 500mA. Backlight and Flash current loops make sure that the corresponding output currents at each individual LED output are regulated to their DAC set current values. The inherent decision and control logic decides the operation mode of the "gear-box" charge pump to maximize overall efficiency. In order to decide on the most efficient operation mode for the charge pump, the decision and control logic observes the battery voltage, output voltage, load current, dropout voltage, over-voltage, over-current conditions and in-regulation feedback signals and forces the charge pump to operate in one of the 1x, 1.5x and 2x modes and dynamically switches between modes to maximize overall efficiency. The charge pump used in the heart of the design is a regulated charge pump and regulates the minimum of the LEDx outputs and FLASH output to be 350mV typical. Regulated output voltage depends on the forward voltage drop of the external LEDs used. The
charge pump switches at a high frequency of 2.4MHz which allows tiny 1uF external capacitors to be used as flying capacitors. When any of the LED outputs or the FLASH output voltage drops below the "dropout" voltage (200mV typical), the charge pump decides to switch up to a less efficient mode, i.e. in 1x mode it switches to 1.5x mode, in 1.5x mode it switches to 2x mode. This switching to a less efficient mode guarantees the part to sustain LED currents in regulation. For the decision to switch back to a more efficient mode, the mode decision logic uses battery voltage, output voltage and load current information and relies on preset margins on the mode switching comparator thresholds. The FLASH channel can be used in torch mode as well as in Flash time-out mode. When used for a momentary Flash output, it is recommended to activate the I2C control for timeout. Once the I2C timeout is activated and for as long as the Flash is active, the SP7682 charge pump will operate in 2x mode in order to provide the continuous voltage and high current needed for Flash. For the SP7682A, which uses the single wire interface, the Flash channel will be in 2x mode whenever the Flash current is at least 230mA. The SP7682 and SP7682A are furnished with undervoltage lockout, current limit, thermal shutdown and over voltage protection features.
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TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
Backlight & Flash VOUT Efficiency
4LE s=20mA lash=0mA D ,F 4LE s=20mA lash=100mA D ,F 4LE s=20mA lash=200mA D ,F
100 95 90
Backlight VOUT Efficiency
100 95 90
Efficiency (%)
Efficiency (%)
4LE Ds=15mA 4LE Ds=20mA 4LE Ds=25mA
85 80 75 70 65 60 55 50 3.0 3.3 3.6
85 80 75 70 65 60 55 50 3.0 3.3 3.6 3.9 4.2
3.9
4.2
Vin (V)
Vin (V)
110 100
Backlight Output Current Vs VIN
300
Backlight & Flash Output Current Vs VIN
Output Current (mA)
250
4LE Ds=20mA,F lash=0mA 4LE Ds=20mA,F lash=100mA 4LE Ds=20mA,F lash=200mA
Output Current (mA)
90 80 70 60 50 3.0
4LE s=15mA D 4LE s=20mA D 4LE s=25mA D
200
150
100
3.3
3.6
3.9
4.2
50 3.0
3.3
3.6
3.9
4.2
Vin (V)
Vin (V)
100 95 90
Backlight LED Efficiency
4LE Ds=15mA 4LE Ds=20mA 4LE Ds=25mA
100 95 90
Backlight & Flash LED Efficiency
4LE Ds=20mA,F lash=0mA 4LE Ds=20mA,F lash=100mA 4LE Ds=20mA,F lash=200mA
Efficiency (%)
80 75 70 65 60 55 50 3.0 3.3 3.6 3.9 4.2
Efficiency (%)
85
85 80 75 70 65 60 55 50 3.0 3.3 3.6 3.9 4.2
Vin (V)
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Vin (V)
(c) 2007 Exar Corporation
TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
Flash PWF4 2x Timeout Mode, IOUT Vs VIN
500
Vin(AC)
Output Current (mA)
400
300
200
Vout(AC)
Flash=500mA 2x Timeout M ode Flash=400mA 2x Timeout M ode Flash=300mA 2x Timeout M ode Flash=200mA A M uto ode
100 3.0
3.3
Vin (V)
3.6
3.9
4.2
400mA 2x Timeout Mode Ripple
Flash PWF4 1.5x Mode Forced, IOUT Vs VIN
500
Flash=500mA 1.5x Forced M ode Flash=400mA 1.5x Forced M ode Flash=300mA 1.5x Forced M ode Flash=200mA 1.5x Forced M ode
Output Current (mA)
400
Vin(AC)
300
200
Vout(AC)
100 3.0
3.3
Vin (V)
3.6
3.9
4.2
400mA Forced 1.5x Mode Ripple
Flash PWF4 Auto Mode, IOUT Vs VIN
500
Output Current (mA)
400
Vin(AC)
300
200
Vout(AC)
Flash=500mA A M uto ode Flash=400mA A M uto ode Flash=300mA A M uto ode Flash=200mA A M uto ode
100 3.0
3.3
Vin (V)
3.6
3.9
4.2
400mA Auto Mode 1.5x to 2x Mode Ripple
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TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
LEDs = 20mA 1x Startup from Shutdown
LEDs = 20mA 1.5x Startup from Shutdown
Ch1=EN
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
Flash = 200mA 1x Startup from Shutdown
Flash = 200mA 1.5x Startup from Shutdown
Ch1=EN
Ch1=EN
Ch2=Vout
Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
Flash = 300mA 2x Timeout Startup from SHDN
Flash = 400mA 2x Timeout Startup from SHDN
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TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
Ch1=SET_BL Ch2=Vout
Ch1=SET_BL Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
SP7682A SET_BL=41 Pulses LEDs=20mA 1x
SP7682A SET_BL=41 Pulses LEDs=20mA, 1.5x
Ch1=SET_FL Ch2=Vout
Ch1=SET_FL
Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
SP7682A SET_FL=31 Pulses Flash=0.3A 1x
SP7682A SET_FL=31 Pulses Flash = 0.3A 2x
Ch1=SET_FL
Ch2=Vout
Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.2A/div
SP7682A SET_FL=31 Pulses Flash=0.3A 2s
SP7682 TD0=TD1=0V Flash=0.3A 4s
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TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
22
20mA Backlight Output Current Vs VIN
LE D1
Ch1=Vin
21
LE D2 LE D3 LE D4
Output Current (mA)
20
19
Ch2=Vout
18 3.0
3.3
3.6
3.9
4.2
Vin (V)
20mA Backlight: 1.5x Mode Ripple
Ch1=EN
Ch1=EN
Ch2=LEDx
Ch2=FLASH
Ch4=Iin 0.2A/div
Ch4=Iin 0.5A/div
Turn-off time into SHDN LEDs=20mA
Turn-off time into SHDN Flash=0.3A
Ch1=SCL Ch2=Vout
Ch1=SCL Ch2=Vout
Ch4=Iin 0.2A/div
Ch4=Iin 0.5A/div
Settle last count Standby LEDs=20mA 1x
Settle last count Standby LEDs=20mA 1.5x
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APPLICATIONS INFORMATION I2C Specifications The I2C protocol defines any device that sends data to the bus as a transmitter and any device that reads the data as a receiver. The device that controls the data transfer is known as the master and the other Data input format:
S SP7682 Address 7-bit R/W 1/0 A Data for Status1 8-bit A Data for Status2 8-bit A Data For LED 8-bit A Data for Flash 8-bit A SP
device as the slave. The master will always initiate a data transfer and will provide the serial clock for synchronization.
Start Condition
Acknowledge, sent by slave
Acknowledge, sent by slave when R/W =0 Or, sent by master when R/W =1
Stop condition
SP7682 I2C Slave Address Map: (7-bit Default Address: 0x28) Fuses Fuse1 0 0 1 1 Fuse0 0 1 0 1 A7 0 0 0 0 A6 1 1 1 1 Device Address A5 0 0 1 1 A4 1 0 1 0 A3 0 0 0 0 A2 0 0 0 0 A1 0 0 0 0 R/W 1/0 A0 0 0 0 0 7-bit address Hex A7-A1 0x28 0x20 0x38 0x30
Theory of Operation - IC Serial Interface The SP7682 has four data registers which can be programmed serially via the IC interface. The first register is a status register which has two bits used for shutdown/power up options, 4 bits used for individual backlight LED ON/OFF control, and 2 bits for charge pump mode. The second STATUS register contains settings of the FLASH time-out,
Temperature OK, Voltage OK, and Flash time-out expired conditions. After the Flash timeout has expired the FTO bit will toggle on and then off for intervals set by the TDO bits. The next two registers are used to set the brightness levels of the backlight LEDs and Flash LED. The register bits are as follows:
REGISTER STATUS1 STATUS2 LEDS FLASH
B7 WZ TOUT0 D5 D5
B6 WP TOUT1 D4 D4
B5 PMP0 TD0 D3 D3
B4 PMP1 TD1 D2 D2
B3 LED0 TOK D1 D1
B2 LED1 VOK D0 D0
B1 LED2 FTO dc dc
B0 LED3 dc dc dc
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APPLICATIONS INFORMATION The following table defines the states for bits PMP0 and PMP1. These bits can be used to set the operating mode for the internal charge pump. PMP0 0 0 1 1 PMP1 0 1 0 1 State Automatic mode detection. 1x mode only. 1.5x and 2x modes are prohibited 1.5x mode only. 1x and 2x modes are prohibited. 1x or 1.5x mode auto detection. 2x mode is prohibited.
The following table defines the states for bits TOUT0 and TOUT1. These bits can be used to adjust current threshold for the time-out feature in Flash mode. TOUT0 0 0 1 1 TOUT1 0 1 0 1 State Time-out disabled Timeout enabled for 110mA and above Timeout enabled for 160mA and above Timeout enabled for 230mA and above
The following table defines the states for bits LED0 to LED3. These bits can be used to turn LEDs On or OFF.
The following table defines the states for bits TD0 and TD1. These bits can be used to adjust time-out delay for the time-out feature in Flash mode. TD0 TD1 0 1 0 1 State 4s 2s 1s 0.5s
LED0 1 0 0 0
LED1 0 1 0 0
LED2 0 0 1 0
LED3 0 0 0 1
State LED0 OFF, other LEDs ON. LED1 OFF, other LEDs ON. LED2 OFF, other LEDs ON. LED3 OFF, other LEDs ON.
0 0 1 1
Addressing and Writing Data to the SP7682 To write data to the SP7682 one of the following two cycles must be obeyed: Easy shutdown/startup sequence
The following table defines the states for bits WZ and WP. These bits can be used to put the SP7682 into shutdown, standby or active. WZ 0 0 1 1 WP 0 1 0 1 State Shutdown, data registers are reset to 000000 Shutdown, data registers are unchanged Standby. Output current is zero, data registers are unchanged. Active. Output current corresponds to the register contents
[Slave Address with write bit][Data for Status] Full shutdown/startup sequence [Slave Address with write bit][Data for Status1][Data for Status2][Data for LEDs][Data for FLASH]
Addressing and Reading Data from the SP7682 To read data from the SP7682 the following data cycle must be obeyed: [Slave Address with read bit][Data for Status1][Data for Status2][Data for LEDs][Data for FLASH]
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APPLICATIONS INFORMATION DAC table for Backlight LED intensity In the LED register bits B7, B6, B5, B4, B3 and B2 represent the DAC codes D5-D0 used to set the LED current in the four LEDs. The following table lists the DAC codes and the corresponding current for each channel in mA: B7-B2
000000 000001 000010 000011 000100 000101 000110 000111 001000 001001 001010 001011 001100 001101 001110 001111 010000 010001 010010 010011 010100 010101 010110 010111 011000 011001 011010 011011 011100 011101 011110 011111 BL (mA) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5
DAC table for FLASH LED intensity In the FLASH register bits B7, B6, B5, B4, B3 and B2 represent the DAC codes D5-D0 used to set the LED current in the four LEDs. The following table lists the DAC codes and the corresponding current for each channel in mA: B7-B2
000000 000001 000010 000011 000100 000101 000110 000111 001000 001001 001010 001011 001100 001101 001110 001111 010000 010001 010010 010011 010100 010101 010110 010111 011000 011001 011010 011011 011100 011101 011110 011111 Flash (mA) 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310
B7-B2
100000 100001 100010 100011 100100 100101 100110 100111 101000 101001 101010 101011 101100 101101 101110 101111 110000 110001 110010 110011 110100 110101 110110 110111 111000 111001 111010 111011 111100 111101 111110 111111
BL (mA) 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 30.5 31.0 31.5
B7-B2
100000 100001 100010 100011 100100 100101 100110 100111 101000 101001 101010 101011 101100 101101 101110 101111 110000 110001 110010 110011 110100 110101 110110 110111 111000 111001 111010 111011 111100 111101 111110 111111
Flash (mA) 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 500 500 500 500 500 500 500 500 500 500 500 500 500
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SP7682A APPLICATIONS INFORMATION SP7682A Single Line Programmable Serial Interface SET_FL (or SET_BL) pin programming waveform shown below:
EN SET_FL tHI=0.5us min tLO=0.5us to 0.25ms tSHDN=0.5ms i shutdown
Backlight Code Table (programmed via SETBL) BL (mA) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 BL (mA) 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5 18 18.5 19 19.5 20 20.5 BL (mA) 21 21.5 22 22.5 23 23.5 24 24.5 25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 30.5 31 31.5
40mA 10mA IFLASH 0mA
In the above example code 5 is programmed as there are five rising edges. Serially Programmable Codes Flash Code Table (programmed via SETFL) code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Flash (mA) 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 code 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Flash (mA) 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 code 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Flash (mA) 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500
code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
code 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
code 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
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(c) 2007 Exar Corporation
APPLICATIONS INFORMATION LED Selection The SP7682 is designed as a driver for backlight white LEDs and Flash white LEDs, but is capable of driving other LED types with forward voltage specifications ranging from 2.0V to 3.8V. LED applications may include LCD display backlighting, camera photo-flash applications, infrared (IR) diodes for remotes, and other loads benefiting from a controlled output current generated from a varying input voltage. Since the D1 to D4 output current-sinks are matched with negligible voltage dependence, the LED brightness will be matched regardless of the specific LED forward voltage (VF) levels. In flash applications, it may be necessary to drive highVF type LEDs. The typical characteristic curves illustrate low VF Flash LEDs using the LumiLEDs PWF4 LED, but the low dropout currentsinks in the SP7682 make it capable of driving LEDs with forward voltages as high as 4.0V from an input supply as low as 3.2V but at a reduced output current. Device Switching Noise Performance The SP7682 operates at a fixed frequency of approximately 2.4MHz to control noise and limit harmonics that can interfere with the RF operation of cellular telephone handsets or other communication devices. Back-injected noise appearing on the input pin of the charge pump can be much less than 100mV peak-to-peak, typically less than inductor-based DC/DC boost converter white LED backlight solutions. The SP7682 soft-start feature helps prevent noise transient effects associated with inrush currents during startup of the charge pump circuit. here for reference. The second case of LED power efficiency is included to show the user the true power delivered to the LEDs. As one can see in the curves, the LED efficiency is greatest when VIN is higher than the VF of the LEDs (and higher than the voltage required on the constant current-sink outputs of the LEDs) and that is when the SP7682 is in the 1x mode. When VIN is less than the VF (and less than the voltage required on the constant current-sink outputs of the LEDs) the SP7682 is in the 1.5x mode or 2x mode and in these modes the input current is 1.5 times or 2 times the output current and therefore the efficiency will be reduced. VOUT efficiency = VOUT*IOUT/(VIN*IIN)*100% LED efficiency = (VOUT -VLED) *IOUt/(VIN*IIN)*100% Refer to the Typical Characteristics section of this document for measured plots of efficiency versus input voltage and output load current versus input voltage for given LED output current options. Capacitor Characteristics Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the SP7682. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor has very low ESR, is lower in cost, has a smaller PCB footprint, and is non-polarized. Low ESR ceramic capacitors help to maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage. Equivalent Series Resistance (ESR) ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several Ohms for tantalum or aluminum electrolytic capacitors.
Power Efficiency The charge pump efficiency shown in the typical characteristic curves is shown for two cases. The first case is called output efficiency which is the power efficiency to the output as a ratio of the output voltage power to the input voltage power and expressed as a percentage. The second case is called LED efficiency and is the power efficiency to the LED outputs and is expressed as a ratio of the power to the LEDs to the input voltage power. These expressions are shown at the end of this section in their formulas. The first case is what is generally shown in competitors' datasheets and is shown
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SP7682: Backlight and Flash Driver Page 16
(c) 2007 Exar Corporation
APPLICATIONS INFORMATION Ceramic Capacitor Materials Capacitors with large output values are typically composed of X7R, X5R, Z5U, or Y5V dielectric materials, but Z5U and Y5V are not recommended since they have a large change in value with temperature. X5R and X7R capacitors are recommended since they are relatively low in cost and their output value changes with temperature are relatively small. Capacitor Selection Careful selection of the four external capacitors CIN, C1, C2, and COUT is important because they will affect turn-on time, output ripple, and transient performance. Optimum performance will be obtained when low equivalent series resistance (ESR) ceramic capacitors are used. In general, low ESR may be defined as less than 100m. A value of 4.7F for the input and 2.2F for the output capacitor is sufficient for most applications. The flying capacitors C1 and C2 Table 1: SP7682/SP7682A Capacitor Selection
Manufacturers/ Website TDK/www.tdk.com TDK/www.tdk.com TDK/www.tdk.com TDK/www.tdk.com Murata/www.murata.com Murata/www.murata.com Murata/www.murata.com Murata/www.murata.com Part Number C1005X5R0J474K C1005X5R0J105K C1608X5R0J225K C1608X5R0J475K GRM155R60J474KE19 GRM155R60J105KE19 GRM185R60J225KE26 GRM188R60J475KE19 Capacitance/ Voltage 0.47uF/6.3V 1uF/6.3V 2.2uF/6.3V 4.7uF/6.3V 0.47uF/6.3V 1uF/6.3V 2.2uF/6.3V 4.7uF/6.3V Capacitor Size/Type/Thickness 0402/X5R/0.55mm 0402/X5R/0.55mm 0603/X5R/0.9mm 0603/X5R/0.9mm 0402/X5R/0.55mm 0402/X5R/0.55mm 0603/X5R/0.55mm 0603/X5R/0.8mm ESR at 100kHz 0.05 0.03 0.03 0.02 0.05 0.03 0.03 0.02
can be 1F for most applications for backlight and Flash, and for light output currents flying capacitors of 0.47uF can be used. For applications when the 4 backlight LED drivers are drive 20mA or more and the Flash driver is driven to 100mA or more, it is advisable to use a 4.7F input capacitor in order to reduce the input ripple as seen by the battery. If the LED currentsinks are only programmed for low current levels, or if the application is not very noise sensitive, then a 2.2F input capacitor may be used. See table 1 for capacitor selection.
Thermal Protection The SP7682 has a thermal protection circuit that will shut down the internal LDO and charge pump if the die temperature rises above the thermal limit, and will restart when the die temperature drops about 20C below the thermal limit.
FOOTPRINT: 3x3mm 16 pin QFN
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SP7682: Backlight and Flash Driver Page 17
(c) 2007 Exar Corporation
PACKAGE: 3x3mm 16 pin QFN
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EXAR
SP7682: Backlight and Flash Driver Page 18 (c) 2007 Exar Corporation
ORDERING INFORMATION
Part Number SP7682ER1-L SP7682ER1-L/TR SP7682EB SP7682AER1-L SP7682AER1L/TR SP7682AEB Control Min Max Theta JA RoHS Interface Temp C Temp C C/W IC IC IC Single Wire Single Wire Single Wire
2 2 2
MSL Level L3 @ 260C L3 @ 260C
Pack Type Canister Tape & Reel
Quantity Package Any 3000 3x3 16 Pin QFN 3x3 16 Pin QFN Board 3x3 16 Pin QFN 3x3 16 Pin QFN Board
-40 -40 -40 -40 -40 -40
85 85 85 85 85 85
Yes Yes
33.3 33.3
Not Applicable to Eval Board Yes Yes 33.3 33.3 L3 @ 260C L3 @ 260C Canister Tape & Reel Any 3000
Not Applicable to Eval Board
For further assistance: Email: WWW Support page: Application Notes: Sipexsupport@sipex.com http://www.sipex.com/content.aspx?p=support http://www.sipex.com/applicationNotes.aspx
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
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SP7682: Backlight and Flash Driver Page 19
(c) 2007 Exar Corporation

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