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Low Noise Backlight and Flash Driver With Serial Interface
POWER MANAGEMENT POWER MANAGEMENT Description
The SC614 is a high efficiency charge pump LED driver using Semtech's proprietary mAhXLife TM technology. Performance is optimized for use in Li-ion battery applications. Each of 7 LED currents can be programmed via the I 2C serial control bus. M1 through M4 are for LED backlighting of LCD main displays. S1/FL3 through S3/FL1 can be used for backlighting sub displays and/ or for driving flash LEDs. These three current sinks are configurable over the I2C interface for any combination of pins for sub or flash use. The charge pump automatically selects an operating mode based on the number of active loads, input voltage, and load currents required. Any combination of LED drivers can be enabled at one time, allowing the SC614 to power any combination of backlight and flash required by the application. Two dedicated pins, MDIM and SDIM, are provided to allow PWM dimming of the main and sub-backlights and one dedicated pin, FL, allows direct control of the flash. All three pins can be utilized without having to use the I2C interface once the registers are set up. The enable pin can be used to put the device in low-current shutdown mode drawing 0.1A (typ), or a register can be written that sets the device in a sleep mode that reduces the current to 50A (typ).
SC614
Features
Four independent current sinks for main backlight, adjustable from 0.4mA to 32mA each Dedicated MDIM pin for PWM dimming of main backlight Three independent current sinks for sub-backlight or flash, adjustable from 0.4mA to 102mA each Configurable sub-backlight or flash sinks Dedicated SDIM pin for PWM dimming of subbacklight Dedicated FL pin for flash control Current accuracy to within 1.5% down to 4.8mA Current matching to within 0.5% down to 4.8mA Very high efficiency over 90% of battery life Shutdown current 0.1A (typ) Three charge pump operating modes: 1x, 1.5x, and 2x I2C serial interface Soft-start/in-rush current limiting 1.33MHz and 250kHz programmable fixed frequency options Short-circuit/thermal protection Output open circuit protection MLPQ-24 package (4mm x 4mm), fully WEEE and RoHS compliant
Applications
Cellular phone backlighting and flash LCD modules PDA backlighting and flash RGB LED Driver
Typical Application Circuit
VBAT VLOGIC
11 17 U1 VIN VIN VOUT VOUT 328mA Max Continuous 434mA Max (500ms)
MAIN BACKLIGHT
FLASH
9 16
R1 Pull-up
R2 Pull-up
C1 2u2
C2 1u
D1 LED
D2 LED
D3 LED
D4 LED
D5 LED
EN SDIM MDIM
2 3 4
EN SDIM
M1 M2
1 24 23 22 20 19 18
32mA Max 32mA Max 32mA Max 32mA Max 306mA Max.
MDIM
M3
SDA SCL FL
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL
S3/FL1
5
ASEL GND TPAD C1+ C2+ 15 C1GND C214
Note: R1 and R2 pull-up resistors are a requirement of the I2C specification
12 21
10
C3 1u
13
C4 1u
April 28, 2006
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United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability.
Parameter Supply Voltage Output Voltage Pin Voltage - C1+, C2+ Pin Voltage - All other pins VOUT Short Circuit Duration Thermal Resistance, Junction to Ambient (1) Operating Ambient Temperature Range Junction Temperature Range Storage Temperature Range IR Reflow (Soldering) 10s to 30s ESD Rating (Human Body Model) (2)
Symbol VIN VOUT
Maximum -0.3 to 6.5 -0.3 to 6.5 -0.3 to VOUT +0.3 -0.3 to VIN +0.3
Units V V V V s C/W C C C C kV
tSC JA TA TJ TSTG TLEAD V ESD
Indefinite 40 -40 to +85 -40 to +150 -65 to +150 260 2
Notes: (1) Calculated from package in still air, mounted to a 3" x 4.5", 4-layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. (2) Tested according to JEDEC standard JESD22-A114-B.
Electrical Characteristics
Unless specified, TA = 25C for Typ, -40C to 85C for Min and Max, VIN = 3.2V to 4.2V, CIN = 2.2F, COUT = CPUMP = 1F (ESR = 0.03).
Parameter
Symbol
Conditions
Min
Typ
Max
Units
Charge Pump Electrical Specifications Input Supply Voltage Maximum Total Output Current Individual LED Current Setting, Main Backlight Individual LED Current Setting, Sub/Flash Individual LED Current Accuracy VIN IOUT(MAX) IMx ISx/FLy ILED_ACC VIN > 3.4V, sum of all active LED currents, VOUT(MAX) = 4.2V, 500ms max. Nominal Settings Nominal Settings VIN = 3.7V, ISET = 0.4mA VIN = 3.7V, ISET = 20mA Flash pins only, VIN = 3.7V, ISET = 102mA LED Matching(1) ILED-LED VIN = 3.7V, ISET = 0.4mA VIN = 3.7V, ISET = 20mA Flash pins only, VIN = 3.7V, ISET = 102mA
(c) 2006 Semtech Corp. 2
3.0 434 0.4 0.4 30 -8.0 1.5 2 20 -3.5 0.5 1
5.5
V mA
32 102
mA mA A
+8.0
% % A
+3.5
%
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Electrical Characteristics (Cont.)
Parameter Symbol Conditions Min Typ Max Units
Charge Pump Electrical Specifications (Cont.) 1x Mode to 1.5x Mode Falling Transition Voltage 1.5x Mode to 1x Mode Hysteresis 1.5x Mode to 2x Mode Falling Transition Voltage 2x Mode to 1.5x Mode Hysteresis Shutdown Current VTRANS1x VHYST1x VTRANS1.5x VHYST1.5x IQ(OFF) IOUT = 70mA (10mA/LED), VOUT = 4V IOUT = 70mA (10mA/LED), VOUT = 4V IOUT = 70mA (10mA/LED), VOUT = 4V IOUT = 70mA (10mA/LED), VOUT = 4V EN = GND, VIN = 4.2V, TA = 25C EN = GND, VIN = 4.2V, TA = -40C to +85C Total Quiescent Current IQ Sleep (EN = VIN, SLEEP = 1, no serial interface activity) 1x mode, IOUT = 0.8mA 1.5x mode, IOUT = 0.8mA, fPUMP = 250kHz 2x mode, IOUT = 0.8mA, fPUMP = 250kHz 1.5x mode, IOUT = 0.8mA, fPUMP = 1.33MHz 2x mode, IOUT = 0.8mA, fPUMP = 1.33MHz Current Sink Off-State Leakage Current DAC Current Step Size Differential Non-Linearity Pump Frequency ILED(OFF) IDACSP DNL fPUMP VIN = 3.2V, FSEL = 0 VIN = 3.2V, FSEL = 1 Digital I/O Electrical Specifications (ASEL, EN, FL, MDIM, SDIM) Input High Threshold Input Low Threshold Input High Current Input Low Current Maximum Input Frequency (MDIM and SDIM Pins) Maximum Input Frequency (FL Pin)
(c) 2006 Semtech Corp.
4.07 100 2.92 200 0.1 1.0 12(2) 50(3) 1.00 1.4 1.8 2.3 3.5 0.1 0.4 1 250 1.33 5.2 1 3.0 1.85
V mV V mV A
A mA
VIN = VEN = VLED = 4.2V 8-bit register
A mA LS B kHz MHz
VIH VIL IIH IIL fDIM fFL
VIN = 5.5V VIN = 3V VIN = 5.5V VIN = 5.5V
1.6 0.4 10 10 0 1
V V A A kHz
50% duty cycle
3
0
1
kHz
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Electrical Characteristics (Cont.)
Parameter Symbol Conditions Min Typ Max Units
I2C Interface Bus Specifications Digital Input Voltage VB-IL VB-IH SDA Acknowledge Output Voltage Digital Input Current I/O Pin Capacitance I2C Timing Specifications Clock Frequency SCL Low Period(2) SCL High Period(2) Data Hold Time(2) Data Setup Time(2) Interface Start-up Time(2) Setup Time for Repeated Start Condition(2) Hold Time for Repeated Start Condition(2) Setup Time for Stop Condition(2) Bus Free Time Between STOP and START(2) Fault Protection Output Short Circuit Current Limit Over Temperature(4) Output Over Voltage IOUT(SC) TOTP VOVP VOUT = GND Rising threshold (hysteresis = 10C) 300 160 5.7 mA C V fSCL tLOW tHIGH tHD;DAT tSU;DAT tEN tSU;STA tHD;STA tSU;STO tBUF Bus start-up time after EN is pulled high 0.6 0.6 0.6 1.3 1.3 0.6 0 100 350 400 440 kHz s s s ns s s s s s VOL IB-IN CIN SDA and SCL SDA and SCL VIN = 3V, IB-IN(SDA) = 3mA -0.2 10 1.6 0.4 0.2 V A pF 0.4 V
Notes: (1) LED matching applies to current sinks set to the same current only. Matching is calculated as follows:
ILED -LED =
(IMAX - IMIN ) * 100% (IMAX + IMIN )
(2) Guaranteed by design. (3) The total quiescent current in Sleep Mode will increase when serial bus activity occurs, and with the clock frequency of that bus activity. (4) When the junction temperature exceeds the Over Temperature (OT) threshold, the device will enter Sleep Mode with the contents of all registers retained. The device will exit Sleep Mode and re-commence normal operation as soon as the junction temperature drops by more than the OT hysteresis.
(c) 2006 Semtech Corp.
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United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Block Diagram
C1+ 10
C113
C2+ 15
C214
VIN VIN EN SDA SCL
11 17 2 7 8 Digital Interface and Logic Control
mAhXLifeTM Fractional Charge Pump (1x, 1.5x, 2x)
9 VOUT 16 VOUT
Oscillator 1 M1 24 M2 23 M3 Current Setting DAC 22 M4 20 S1/FL3 19 S2/FL2 18 S3/FL1
MDIM 4 SDIM 3
ASEL 5 Pull high or low to set slave address FL
6
Control Override
12 GND 21 GND
(c) 2006 Semtech Corp.
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United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Pin Configuration
S1/FL3 S2/FL2 GND M2 M3 M4
Ordering Information
Device SC614MLTRT(1) SC614DB(3)
18 S3/FL1 VIN VOUT C2+ C2C1-
P ackag e MLPQ-24(2) Demonstration Board Evaluation Board
24 M1 EN SDIM MDIM ASEL FL 1 2 3 4 5 6 7 SDA
23
22
21
20
19
SC614EVB(4)
TOP VIEW
17 16 15 14
T 8 SCL 9 VOUT 10 C1+ 11 VIN 12 GND
13
Notes: (1) Lead free product. This product is fully WEEE and RoHS compliant. (2) Only available in tape and reel packaging. A reel contains 3000 devices. (3) The demonstration board showcases the most common uses for this part, running at maximum current settings. (4) The evaluation board is user-configurable and allows the user to communicate with the part using a graphical user interface on a personal computer with a USB connection. Contact factory for availability.
MLP24: 4X4 24 LEAD
Marking Information
Top Mark
614 yyww xxxxx xxxxx
yy = two-digit year of manufacture ww = two-digit week of manufacture xxxxx = lot number
(c) 2006 Semtech Corp.
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United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Pin Descriptions
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Pin Name M1 EN SDIM MDIM ASEL FL SD A SC L VOUT C 1+ VIN GND C 1C 2C 2+ VOUT VIN S3/FL1 S2/FL2 S1/FL3 GND M4 M3 M2 THERMAL PAD Pin Function Current sink input for main backlight LED 1. Leave unconnected if not used. Enable input, active high. Dimming pin for sub backlight LEDs. High = OFF, low = ON. Dimming pin for main backlight LEDs. High = OFF, low = ON. Address select. Pin can be pulled low or high to set one bit in the device address. This allows two devices to be connected to the same bus. Control pin for flash LEDs. High = ON, low = OFF. I2C serial data (bi-directional). An external pull-up resistor is required. I2C clock input. An external pull-up resistor is required. Charge pump output. Connect to pin 16. Bucket capacitor C1 positive connection. Battery voltage input. Connect to pin 17. Ground pin. Connect directly to ground plane. Bucket capacitor C1 negative connection. Bucket capacitor C2 negative connection. Bucket capacitor C2 positive connection. Charge pump output. Decouple this pin using a 1F ceramic capacitor to pin 21. All VOUT connections should be starred to the top of this capacitor. Battery voltage input. Decouple this pin using a 2.2F ceramic capacitor to pin 21. Current sink input for sub backlight or flash. Combine with S2/FL2 and S1/FL3 for maximum flash current capability. Leave unconnected if not used. Current sink input for sub backlight or flash. Combine with S1/FL3 and S3/FL1 for maximum flash current capability. Leave unconnected if not used. Current sink input for sub backlight or flash. Combine with S2/FL2 and S3/FL1 for maximum flash current capability. Leave unconnected if not used. Ground pin. Connect directly to ground plane. Current sink input for main backlight LED 4. Leave unconnected if not used. Current sink input for main backlight LED 3. Leave unconnected if not used. Current sink input for main backlight LED 2. Leave unconnected if not used. Pad for heatsinking purposes. Connect to ground plane using multiple vias. Not connected internally.
(c) 2006 Semtech Corp.
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SC614
POWER MANAGEMENT Register Map
Address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08
0
D7
0 0 0 0 0
D6
S3/FL1EN
D5
S2/FL2EN
D4
S1/FL3EN
D3
M4EN
D2
M3EN
D1
M2EN
D0
M1EN
R eset Value
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
Description
LED On/Off control M1 current control M2 current control M3 current control M4 current control S1/FL3 current control S2/FL2 current control S3/FL1 current control Control Register
7-bit current setting, 0.4mA/bit, 0x00 = OFF, 0x50 = 32mA 7-bit current setting, 0.4mA/bit, 0x00 = OFF, 0x50 = 32mA 7-bit current setting, 0.4mA/bit, 0x00 = OFF, 0x50 = 32mA 7-bit current setting, 0.4mA/bit, 0x00 = OFF, 0x50 = 32mA 8-bit current setting, 0.4mA/bit, 0x00 = OFF, 0xFF = 102mA 8-bit current setting, 0.4mA/bit, 0x00 = OFF, 0xFF = 102mA 8-bit current setting, 0.4mA/bit, 0x00 = OFF, 0xFF = 102mA FLMODE S LE E P SWRES FS E L F L1 F L0 0
0x20
Note: all registers are readable and writable. Definition Of Terms: 0: Leave this bit as a 0. xEN: On/off control for individual current sinks. Set to 1 to enable, clear to 0 to disable. FLMODE: Flash Mode control bit. Set to 1 for Flash mode, clear to 0 for normal mode. SLEEP: Sleep Mode control bit. Set to 1 to put into low current mode (Bandgap, UVLO monitor and interface monitoring stay on, all other circuitry shut down), clear to 0 for normal mode. SWRES: Software Reset bit. Set to 1 to reset all registers (SWRES clears automatically and does not require an additional I2C write). FSEL: Frequency Select bit. Allows the choice between two different switching frequencies, set to 1 for 1.33MHz, clear to 0 for 250kHz.
(c) 2006 Semtech Corp.
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SC614
POWER MANAGEMENT POWER MANAGEMENT Register Map (Cont.)
FL1,0: Control Override bits for S1/FL3, S2/FL2 and S3/FL1. Enable control is transferred to the FL pin (assuming the LEDs are first enabled) based on the following table:
FL1 0 0 1 1 FL0 0 1 0 1 FL Pin Control Status Control maintained by register bits - FL pin disabled. S3/FL1 enable controlled by the FL pin. S3/FL1, S2/FL2 enables controlled by the FL pin. S3/FL1, S2/FL2, S1/FL3 enables controlled by the FL pin.
SC614 Slave Address Following a start condition, the master must output the address of the slave it is accessing. The most significant six bits of the slave address are the device type identifier (ID). For the SC614 this is fixed at 111000[ASEL]. The next significant bit addresses a particular device. A system can have up to two SC614 devices on the same bus. The two addresses are defined by the state of the ASEL input (see Table below).
DEVICE TYPE IDENTIFIER 1 1 1 0 0 0 DEVICE ADDRESS Pin ASEL to GND = 0 Pin ASEL to VIN = 1 R/W X
(c) 2006 Semtech Corp.
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SC614
POWER MANAGEMENT State Diagrams
Start-Up
Power Off
VIN high , Lowest Power State. All internal functions powered down
EN low
Shutdown
VIN , EN high
EN
= High
Bandgap up, UVLO and serial interface monitoring active only
Sleep Mode ( SLEEP = 1 )
SLEEP = 0 Bandgap up, UVLO and serial interface monitoring active, charge pump running with VOUT = 1.5V Run Mode ( SLEEP = 0 )
When the SC614 is first enabled, it starts up in Sleep Mode, with the registers at their reset values and the charge pump off. The bandgap reference will be operating, the input voltage will be monitored for UVLO and the serial interface will be monitored for any activity. This is the lowest power state for the device where it can be communicated with. In order to activate the charge pump it is necessary to clear the Sleep bit to 0 to enter Run Mode. When in Run Mode the charge pump is activated in 1x mode with VOUT = 1.5V, and all of the optional functions of the device may be accessed.
(c) 2006 Semtech Corp.
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SC614
POWER MANAGEMENT POWER MANAGEMENT State Diagrams (Cont.)
Power Management
SLEEP = 1 from any Run Mode Sleep Mode (Register contents stored) SLEEP = 0
SWRST = 1 from any Run Mode Sleep Mode (Register contents reset) SLEEP = 0
EN low from any mode
Shutdown (EN low)
Return to previous Mode
Run Mode
There are three options for powering down the SC614 (other than writing 0x00 to each Current Control Register or the LED On/Off Control Register): Sleep Mode (SLEEP = 1) Setting this bit to 1 at any time will power down the charge pump. The register contents will be stored, the bandgap reference will remain active, and UVLO and serial interface monitoring will continue. Clearing this bit will resume operation as before. Sleep Mode from Reset (SWRES = 1) Setting SWRES to 1 will reset all registers (clearing the SWRES bit), causing the part to enter Sleep Mode but with all registers at their reset values (0x00 for registers 0x00 through 0x07, 0x20 for Control Register 0x08 (SLEEP = 1). Upon clearing the SLEEP bit, the SC614 will enter run mode and will require writing to the registers to commence driving LEDs. Shutdown (EN low) All internal functions are powered down. Pulling EN high will enter Sleep Mode with all registers reset. Device Operation With All LEDs Disabled If the SC614 is driving LEDs and then all LEDs are disabled, the device reverts to 1x mode with a nominal output voltage of 3V. This decreases the response time when the LEDs are enabled once more. Quiescent current in this mode will be 700A (nom).
(c) 2006 Semtech Corp.
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United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Applications Information
General Operation The SC614 contains a fractional charge pump, mode selection circuitry, serial I/O logic, serial data registers and current regulation circuitry for 7 LED outputs. All are depicted in the Block Diagram on page 5. The fractional charge pump multiplies the input voltage by 1, 1.5 or 2 times the input voltage. The charge pump switches at a fixed frequency that is bit selectable to 1.33MHz or 250kHz. The default frequency is 250kHz. The charge pump does not switch during 1x mode, saving power and improving efficiency. The mode selection circuitry automatically selects the mode as 1x, 1.5x or 2x based on circuit conditions such as LED voltage, input voltage and load current. 1x is the most efficient mode, followed by 1.5x and 2x modes. At lower input voltages a stronger mode may be needed to maintain regulation. If so, the mode will change first to 1.5x and then later to 2x. 2x mode usually operates for a much shorter run time compared to 1x mode, and 2x mode maintains the output until the battery is discharged to 3V or less. The LED requiring the highest voltage drop will determine the output voltage needed to drive all outputs with sufficient anode voltage. Comparing all cathodes and regulating VOUT for the LED with the lowest cathode voltage ensures sufficient bias for all LEDs. The LED outputs are controlled through the serial data registers, found in the Register Map on page 8. LED on/ off functions are independently controlled, so that any combination of LEDs may be switched on. Seven (7) current regulating circuits sink currents from the LEDs as set by the Current Control registers. For LCD backlighting applications current matching is crucial, and LEDs with matched forward voltage will produce the best possible matched currents. The SC614 is capable of dealing with V F mis-matches up to 0.5V. For best matching performance, however, it is recommended that the LED to LED difference, VF, be under 250mV. Designing for Lowest Possible Battery Current The battery current and efficiency of the SC614 are mostly dependent on the charge pump mode of operation. To get the best performance from the SC614 it is better to use LEDs with consistantly lower VF. Lower VF will keep the charge pump in 1x mode longer and will use less battery current, extending the run time of the battery.
(c) 2006 Semtech Corp. 12
Mode Transition Threshold Voltage and Hysteresis Mode transition threshold voltage refers to the input voltage at the point when the charge pump changes from a weaker mode (lower numerically) to a stronger mode (higher numerically). VTRANS1X is the transition from 1x to 1.5x mode, and VTRANS1.5X is the transition from 1.5x to 2x mode. Mode transition voltages VTRANS1X and VTRANS1.5X can be estimated by the following equations: VTRANS1X = VF + VILED + IOUT 1.0 VTRANS1.5X = (VF + VILED + IOUT 5.5) / 1.5 where VF is the highest forward voltage of the operating LEDs, VILED is the current sink voltage for that LED (typically VILED=150mV) and IOUT is the sum of all operating LED currents. The mode transition circuitry has hysteresis built in to prevent the device from toggling between modes when the input voltage is right at the threshold of mode change. There is 100mV of hysteresis between 1.5x and 1x modes and 200mV of hysteresis between 2x and 1.5x modes. Efficiency Power efficiency can be estimated for any particular battery voltage as follows: = [VOUT IOUT / VIN (IOUT Mode+IQ)] 100 % where: VOUT = VF+ VILED (defined in the above section). and, IQ = 1mA in 1x mode, 1.4mA in 1.5x mode and 1.8mA in 2x mode (250kHz). LED Current Accuracy The LED current is set by the Current Control registers 0x01 through 0x07. The guaranteed accuracy of any current sink is +/-8% at a current setting of 20mA, with the typical accuracy much higher at +/-1.5%. For example, if the Current Control registers are configured such that each LED current will be 20mA (0x32 written to register 0x01 through 0x07), the actual LED currents
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Applications Information (Cont.)
would be between 18.4mA and 21.6mA (+/-8%). All 7 outputs meet this requirement over the industrial temperature range. To calculate the accuracy based upon the actual measured LED current, ILED_ACC, use the following formula:
ILED _ ACC =
(I
LED (Measured )
- ILED( SET ) )
ILED(SET )
* 100%
that LED current back into regulation. When the OVP trip point is reached, the charge pump will be turned off. Any current sinks that measure close to ground will be turned off in an attempt to isolate the faulty LED. Once the output voltage drops enough the charge pump will resume operation. Over-Temperature Protection The over-temperature protection circuitry helps to prevent the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 160C the output is disabled and the device enters sleep mode. All register settings are retained. The junction temperature must drop by more than the hysteresis of 10C before the part exits sleep mode and re-commences normal operation. Over-Current and Short Circuit Protection Adaptive current limit circuitry is provided to protect the device from various levels of shorts from resistive to full shorts as well as to limit in-rush current at start-up and during mode transitions. The current limit levels adjust to the total output current set for the LEDs and thus will be higher when very high levels of currents are programmed, such as for flash operation. The current limit levels are set to ensure that the device will not current limit under normal operation. When an output short circuit occurs, the device folds back the current limit level to a nominal 300mA. If sustained current limit occurs the device may shut down due to internal heating triggering the OTP circuitry. Capacitor Selection The SC614 is designed to use low-ESR ceramic capacitors for all four external capacitors: input, output and charge pump bucket capacitors. Ideal performance is achieved when the bucket capacitors (C3 and C4 in the application circuit) are exactly equal. Note: It is
recommended that X5R or X7R capacitors are used for best performance.
Current Matching The current matching percentage is a figure that represents how closely matched LEDs are that are set to the same current. For any particular LED within a group of LEDs set to the same current, the matching is the I for that LED from the average of the minimum and maximum value of the group (i.e. the center of the measured current range) expressed as a percentage of that average. Current matching is calculated as follows:
IMAX = * 100% IMAX + IMIN 2 IMIN * 100% I + IMIN MAX 2
ILED _ LED
or
Which can be reduced to:
ILED _ LED =
(IMAX - IMIN ) * 100% (IMAX + IMIN )
Protection Circuitry The SC614 also provides protection circuitry that prevents the device from operating in an unspecified state. These include Output Over-Voltage Protection (OVP), Over-Temperature Protection (OTP), Over-Current Protection (OCP) and Short-Circuit Protection (SCP). Output Over-Voltage Protection Output over-voltage protection is included to prevent the SC614 from generating an output voltage that could damage other devices connected to it such as load LEDs any bypass capacitors. When the output voltage exceeds 5.7V, the OVP circuitry disables the charge pump until the output voltage decreases to an acceptable level. Usually the only reason for the output voltage to trip OVP is if one of the LEDs goes open. If this happens the SC614 will raise the output voltage to attempt to bring
(c) 2006 Semtech Corp. 13
Thermal Resistance and Heat Management The SC614 is packaged in a thermally efficient MLPQ24 package that has a thermal pad to remove the heat from the part. It is intended to be connected using multiple vias to the ground plane, and the thermal resistance rating of 40C/W reflects this. A good layout will enable the part to operate at maximum output current ratings without tripping the OTP circuitry.
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Applications Information (Cont.)
Layout Guidelines The following layout is suggested (shown as three-layer (top, bottom and ground layer) only for clarity). C1 is the input capacitor which should be placed close to pin 17. C2 is the output capacitor which should be placed close to pin 16. The capacitors C3 and C4 are the bucket capacitors which can carry up to the full load current of 434mA pulsed for one half clock cycle (at either 250kHz or 1.33MHz depending upon selected operating frequency). Multiple vias should be used whenever it is necessary to change layers on nets connecting to CIN, VOUT, C1+, C1-, C2+ and C2-. As mentioned before, the thermal pad should connect to ground using multiple vias, with 4 vias recommended.
VBAT
U1 VIN VIN VOUT VOUT
11 17
9 16
C1 2u2
C2 1u
2 3 4
EN SDIM
M1 M2
1 24 23 22 20 19 18
MDIM
M3
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL S3/FL1
5 12 21
ASEL GND TPAD C1+ C2+ 15 C1GND C214
25
10
C3 1u
13
C4 1u
Layout Guidelines Schematic
Top Copper and Top Silkscreen
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SC614
POWER MANAGEMENT POWER MANAGEMENT Applications Information (Cont.)
Bottom Copper
Ground Layer
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SC614
POWER MANAGEMENT Application Examples
Main Backlight Plus Flash
VBAT VLOGIC
11 17 U1 VIN VIN VOUT VOUT 328mA Max Continuous 434mA Max (500ms)
MAIN BACKLIGHT
FLASH
9 16
R1 Pull-up
R2 Pull-up
C1 2u2
C2 1u
D1 LED
D2 LED
D3 LED
D4 LED
D5 LED
EN SDIM MDIM
2 3 4
EN SDIM
M1 M2
1 24 23 22 20 19 18
32mA Max 32mA Max 32mA Max 32mA Max 306mA Max.
MDIM
M3
SDA SCL FL
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL
S3/FL1
5
ASEL GND TPAD C1+ C2+ 15 C1GND C214
Note: R1 and R2 pull-up resistors are a requirement of the I2C specification
12 21
10
C3 1u
13
C4 1u
Features: * Up to 4 LED main backlight with up to 32mA per LED * PWM dimming of backlight using MDIM pin * Up to 306mA flash capability controlled by FL pin Register Settings (20mA backlight currents and 300mA flash current used as an example): 0x00: set to 0x7F to enable all 7 current sinks for use 0x01 through 0x04: set to 0x32 for 20mA per current sink 0x05 through 0x07: set to 0xFA for 100mA per current sink, 300mA total 0x08: set to 0x46 for Flash Mode enabled, 250kHz charge pump frequency, FL pin controls S1/FL3, S2/FL2 and S3/FL1
(c) 2006 Semtech Corp.
16
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Application Examples (Cont.)
Main Backlight Plus Sub-Backlight
MAIN BACKLIGHT
U1 VIN VIN VOUT VOUT 328mA Max Continuous 434mA Max (500ms)
VBAT VLOGIC
11 17
SUB BACKLIGHT
9 16
R1 Pull-up
R2 Pull-up
C1 2u2
C2 1u
D1 LED
D2 LED
D3 LED
D4 LED
D5 LED
D6 LED
D7 LED
EN SDIM MDIM
2 3 4
EN SDIM MDIM
M1 M2 M3
1 24 23 22 20 19 18
32mA Max 32mA Max 32mA Max 32mA Max 102mA Max 102mA Max 102mA Max
SDA SCL FL
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL
S3/FL1
5
ASEL GND TPAD C1+ C2+ 15 C1GND C214
Note: R1 and R2 pull-up resistors are a requirement of the I2C specification
12 21
10
C3 1u
13
C4 1u
Features: * Up to 4 LED main backlight with up to 32mA per LED * PWM dimming of main backlight using MDIM pin * Up to 3 LED sub-backlight with up to 32mA per LED * PWM dimming of sub-backlight using SDIM pin Register Settings (20mA backlight currents used as an example): 0x00: set to 0x7F to enable all 7 current sinks for use (or as needed if less) 0x01 through 0x07: set to 0x32 for 20mA per current sink 0x08: set to 0x00 for Flash Mode disabled (FL pin inactive) and 250kHz charge pump frequency
(c) 2006 Semtech Corp.
17
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Application Examples (Cont.)
Main Backlight Plus Sub-Backlight Plus Flash
MAIN BACKLIGHT
U1 VIN VIN VOUT VOUT 328mA Max Continuous 434mA Max (500ms)
VBAT VLOGIC
11 17
SUB BACKLIGHT
FLASH
9 16
R1 Pull-up
R2 Pull-up
C1 2u2
C2 1u
D1 LED
D2 LED
D3 LED
D4 LED
D5 LED
D6 LED
D7 LED
EN SDIM MDIM
2 3 4
EN M1 SDIM MDIM M3 M2
1 24 23 22 20 19 18
102mA Max 102mA Max 102mA Max 102mA Max 102mA Max 102mA Max 102mA Max R3 Balance R4 Balance
SDA SCL FL
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL
S3/FL1
5
ASEL GND TPAD C1+ C2+ 15 C1GND C214
Note: R1 and R2 pull-up resistors are a requirement of the I2C specification
12 21
10
C3 1u
13
C4 1u
Features: * Up to 4 LED main backlight with up to 32mA per LED * PWM dimming of main backlight using MDIM pin * Up to 2 LED sub-backlight with up to 32mA per LED using resistor current balancing * PWM dimming of sub-backlight using SDIM pin * Up to 204mA flash capability controlled by FL pin Register Settings (20mA backlight currents and 200mA flash current used as an example): 0x00: set to 0x7F to enable all 7 current sinks for use 0x01 through 0x04: set to 0x32 for 20mA per current sink 0x05: set to 0x64 for 40mA for this current sink (20mA per LED) 0x06 and 0x07: set to 0xFA for 100mA per current sink, 200mA total 0x08: set to 0x44 for Flash Mode enabled, 250kHz charge pump frequency, FL pin controls S2/FL2 and S3/FL1
(c) 2006 Semtech Corp.
18
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Application Examples (Cont.)
Main Backlight Plus RGB Indicator
MAIN BACKLIGHT
U1 VIN VIN VOUT VOUT 328mA Max Continuous 434mA Max (500ms)
VBAT VLOGIC
11 17
RGB INDICATOR
9 16
D5 RGB_LED
R1 Pull-up
R2 Pull-up
C1 2u2
C2 1u
D1 LED
D2 LED
D3 LED
D4 LED
EN SDIM MDIM
2 3 4
EN SDIM MDIM
M1 M2 M3
1 24 23 22 20 19 18
102mA Max 102mA Max 102mA Max 102mA Max 102mA Max 102mA Max 102mA Max
SDA SCL FL
7 8
SDA SCL
SC614
M4 S1/FL3 S2/FL2
6
FL
S3/FL1
5
ASEL GND TPAD C1+ C2+ 15 C1GND C214
Note: R1 and R2 pull-up resistors are a requirement of the I2C specification
12 21
10
C3 1u
13
C4 1u
Features: * Up to 4 LED main backlight with up to 32mA per LED * PWM dimming of backlight using MDIM pin * 3 current sinks for RGB with up to 32mA per LED * Dimming and color rotation of RGB over I2C interface Register Settings (20mA backlight currents and as required on the fly RGB current used as an example): 0x00: set to 0x7F to enable all 7 current sinks for use 0x01 through 0x04: set to 0x32 for 20mA per current sink 0x05 through 0x07: set to as required on the fly for each color 0x08: set to 0x00 for Flash Mode disabled (FL pin inactive) and 250kHz charge pump frequency
(c) 2006 Semtech Corp.
19
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Using the I2C Serial Port
The I2C General Specification The SC614 is a read-write slave-mode I2C device and complies with the Philips I2C standard Version 2.1 dated January 2000. The SC614 has nine user-accessible internal 8-bit registers. The I2C interface has been designed for program flexibility, in that once the slave address has been sent to the SC614 enabling it to be a slave transmitter/receiver any register can be written or, read from independently of each other. While there is no auto increment/decrement capability in the SC614 I2C logic, a tight software loop can be designed to randomly access the next register independent of which register you begin accessing. The start and stop commands frame the datapacket and the repeat start condition is allowed if necessary. SC614 Limitations to the I2C specifications Seven bit addressing is used and ten bit addressing is not allowed. Any general call address will be ignored by the SC614. The SC614 is not CBUS compatible. Finally, the SC614 can operate in standard mode (100kbit/s) or fast mode (400kbit/s).
Supported Formats
Direct Format - Write: The simplest format for an I2C write is the direct format write. After the master sends a start condition, the slave address is sent followed by an eighth bit indicating a write. The SC614 then acknowledges that it is being addressed, and the master responds with an 8-bit data byte consisting of the target register address. The slave acknowledges and the master sends the appropriate 8-bit data byte. Once again the slave acknowledges and the master terminates the transfer with a stop condition.
S Slave Address W A Register Address A Data A P
S: W: A: P:
Start Condition Write = 0 Acknowledge (SDA low) Stop Condition
Slave Address: Register Address: Data:
7 bit 8 bit 8 bit
Shaded represents transmission from master to slave and unshaded represents transmission from slave to master.
Combined Format (Read/Write): After a start condition, the slave address is sent followed by an eighth bit indicating a write. The SC614 then acknowledges that it is being addressed, and the master responds with an 8 bit data byte consisting of the target register address. The slave acknowledges once more and the master sends the repeated start condition. Once again, the slave address is sent, followed by an eighth bit indicating a read or write. The slave responds with an acknowledge. If the command was a write, the master sends the appropriate 8-bit data byte. Once again the slave acknowledges and the master terminates the transfer with a stop condition. If the command was a read, the slave sends the appropriate 8-bit data byte, to which the master sends a not acknowledge and then terminates the transfer with a stop condition.
S Slave Address W A Register Address A Sr Slave Address R/W A Data(1) A/N(1) P
S: W: A: Sr: R:
Start Condition Write = 0 Acknowledge (SDA low) Repeated Start Condition Read = 1
N: Not Acknowledge(SDA high)(1) P: Stop Condition Slave Address: 7 bit Register Address: 8 bit Data: 8 bit
Shaded represents transmission from master to slave and unshaded represents transmission from slave to master. (1) Not shaded because transfer direction depends upon R/W bit. (c) 2006 Semtech Corp. 20 United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Using the I2C Serial Port (Cont.)
Stop Separated Reads: A further form of read is available which is, in effect, an extension of the combined format read. This format allows a master to set up the register address pointer for a read, and return to that slave some time later to read the data. After a start condition, the slave address is sent, followed by a write. The SC614 then acknowledges that it is being addressed, and the master responds with the 8-bit target register address. The master then sends a stop or repeated start condition, and may address another slave. Some time later the master sends a start or repeated start condition, and a valid slave address is sent, followed by a read. The SC614 then acknowledges and returns the data at the register address location that had previously been set up.
S Slave Address W A
Register Address
A
P
(Master Addresses S/Sr Slave Address R Other Slaves)
A
Data
N
P
S: Start Condition Slave Address: 7 bit W: Write = 0 Register Address: 8 bit A: Acknowledge (SDA low) Data: 8 bit P: Stop Condition Sr: Repeated Start R: Read = 0 Shaded represents transmission from master to slave and unshaded represents transmission from slave to master.
(c) 2006 Semtech Corp.
21
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Typical Characteristics
Battery Current (Sub-only)
100
Battery Current (Main and Sub)
250
90
LED 5-7 = 20mA
200
LED VF = 3.276V 80
LED 1-7 = 20mA LED VF = 3.340V
IBAT(mA)
60
IBAT(mA)
100 50 0
3.0 3.2 3.4 3.6 3.8 4.0 4.2
70
150
50
40
30
3.0
3.2
3.4
3.6
3.8
4.0
4.2
VBAT(V)
VBAT(V)
Power Efficiency (Sub-only)
100 Conversion Efficiency LED 5-7 = 20mA 90 LED VF = 3.276V
90 100
Power Efficiency (Main and Sub)
Conversion Efficiency LED 1-7 = 20mA LED VF = 3.340V Utilized Power Efficiency
% Efficiency
80
Utilized Power Efficiency
80
70
% Efficiency
70
60
60
50
50
40
40
30 3.0 3.2 3.4 3.6 3.8 4.0 4.2
30 3.0 3.2 3.4 3.6 3.8 4.0 4.2
VBAT(V)
VBAT(V)
Typical LED Matching (Main and Sub)
3.5
Typical LED Accuracy (Main and Sub)
6.0
2.5
4.0
LED 1-7 = 20mA
1.5
Max 2.0 Min Min 0.0
LED Matching (%)
0.5
-0.5
LED Accuracy %
3.0 3.2 3.4 3.6 3.8 4.0 4.2
-2.0
-1.5
-2.5
-4.0
-3.5
-6.0 3.0 3.2 3.4 3.6 3.8 4.0 4.2
VBAT(V)
VBAT(V)
(c) 2006 Semtech Corp.
22
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Typical Characteristics (Cont.)
Battery Current (Main and Flash)
900
Battery Current (Main only)
140
800
LED 1-4 = 20mA
LED 1-4 = 20mA 120 LED VF = 3.23V
LED 5-7 = 100mA 700 LED VF = 3.388V
IBAT(mA)
600
IBAT(mA)
100
80
500
60
400
300 3.0 3.2 3.4 3.6 3.8 4.0 4.2
40 3.0 3.2 3.4 3.6 3.8 4.0 4.2
VBAT(V)
VBAT(V)
Power Efficiency (Main and Flash)
100 LED 1-4 = 20mA
90 100
Power Efficiency (Main only)
Utilized Power Efficiency
90
LED 5-7 = 100mA
% Efficiency
80
LED VF = 3.388V
80
Conversion Efficiency
70
% Efficiency
70
60
Conversion Efficiency
60
LED 1-4 = 20mA LED VF = 3.23V
50 Utilized Power Efficiency 40
50
40
30 3.0 3.2 3.4 3.6 3.8 4.0 4.2
30 3.0 3.2 3.4 3.6 3.8 4.0 4.2
VBAT(V)
VBAT(V)
(c) 2006 Semtech Corp.
23
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT Outline Drawing MLPQ-24 4 x 4
A
D
B
DIM
A A1 A2 b D D1 E E1 e L N aaa bbb
PIN 1 INDICATOR (LASER MARK)
E
A2 A aaa C A1 D1 LxN E/2 E1 2 1 N e C SEATING PLANE
.031 .035 .040 .000 .001 .002 - (.008) .007 .010 .012 .151 .157 .163 .100 .106 .110 .151 .157 .163 .100 .106 .110 .020 BSC .011 .016 .020 24 .004 .004
DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX
0.80 0.90 1.00 0.00 0.02 0.05 - (0.20) 0.18 0.25 0.30 3.85 4.00 4.15 2.55 2.70 2.80 3.85 4.00 4.15 2.55 2.70 2.80 0.50 BSC 0.30 0.40 0.50 24 0.10 0.10
bxN bbb CAB
NOTES:
D/2
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
(c) 2006 Semtech Corp.
24
United States Patent No. 6,504,422 www.semtech.com
SC614
POWER MANAGEMENT POWER MANAGEMENT Land Pattern MLPQ-24 4 x 4
K
(C)
H
G
Z
DIM C G H K P X Y Z
DIMENSIONS INCHES MILLIMETERS (.155) (3.95) 3.10 .122 .106 2.70 .106 2.70 .021 0.50 .010 0.25 .033 0.85 .189 4.80
X P
NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Contact Information
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 FAX (805)498-3804 Visit us at: www.semtech.com
(c) 2006 Semtech Corp. 25 United States Patent No. 6,504,422 www.semtech.com

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