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SP7685
1.2A Buck/Boost Charge Pump LED Driver
FEATURES Output Current up to 1.2A Up to 94% Efficiency in Torch Mode Adjustable FLASH Mode Current Minimum External Components: No Inductors Automatic Buck/Boost Mode Switchover Wide VIN Range: 2.7V to 5.5V High Frequency Operation: 2.4 MHz 50mV Reference for low Loss Sensing IQ < 2A in Shutdown PWM Dimming Control Automatic Soft Start Limits Inrush Current Overvoltage Protection on Output Overcurrent/temperature Protection Low Ripple and EMI Ultra-low Dropout Voltage in Buck Mode 2.6 Second Timeout in Flash Mode Space Saving RoHS Compliant, Lead Free Package: 10-pin 3mm x 3mm DFN
VIN C1 C2 FLASH EN
1 2 3 4 5 10
VOUT PGND SGND FB RSET
SP7685
10 Pin DFN
9 8 7 6
APPLICATIONS White LED Torch/Flash for Cell Phones, DSCs, and Camcorders White LED Backlighting Generic Lighting/Flash/Strobe Applications General Purpose High Current Boost
DESCRIPTION The SP7685 is a current-regulated charge pump ideal for powering high brightness LEDs for camera flash applications. The charge pump can be set to regulate two current levels for FLASH and TORCH modes. The SP7685 automatically switches modes between step-up and step-down ensuring that LED current does not depend on the forward voltage. A low current sense reference voltage (50mV) allows the use of small 0603 current sensing resistors. The SP7685 is offered in 10-pin DFN package. TYPICAL APPLICATION CIRCUIT
VIN (3.0 - 4.2V)
O
CIN 10F VIN CFC 1F
VOUT COUT 10F 1A Flash 200mA Torch PWF1 WLED
C1 SP7685 PGND C2 SGND FLASH EN FB RSET RSET 80K
TORCH/FLASH ENABLE
RSENSE 0.22
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
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ABSOLUTE MAXIMUM RATINGS
VIN , VOUT ....................................................................... -0.3V to 6V Output Current Pulse (Flash) ................................. 2A Output Current Continuous (Torch) ..................... 0.4A Storage Temperature ...................... -65C to +150C Operating Temperature ..................... -40C to +85C VEN ............................................................ 0.0V to 7V 3x3 10 DFN .........................................OJA = 40.5C/W ESD Rating. ................................................ 2kV HBM 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.
ELECTRICAL CHARACTERISTICS
TA = -40C to +85C, VIN =3.6V, CIN = 10F, CFC =1.0F, COUT =10F. VSHDN = VIN, typical values at 25C. The denotes the specifications which apply over the full operating temperature range unless otherwise noted.
PARAMETER Operating Input Voltage Quiescent Current
MIN. 2.7
TYP.
MAX. 5.5
UNITS V mA
CONDITIONS
0.5 2
3
V IN = 2.7 - 5.5V FLASH = GND, 1X Mode, ILOAD = 100A FLASH = High, 2x mode
Shutdown Current Oscillator Frequency Charge Pump Equivalent Resistance (x2 mode) Charge Pump Equivalent Resistance (x1 mode) 45 FB Reference Voltage 138 FB Reference Voltage Range FB Pin Current EN, FLASH Logic Low EN, FLASH Logic High EN, FLASH Pin Current V OUT Turn-on Time Thermal Shutdown Temperature Maximum Flash ON time 1.6 170 145 2.6 1.3 100 150 2.4 4 0.4 50
2
A MHz
V IN = 5.5V, VEN = 0.0V
V FB = 0.0V, V IN= 3.6V V IN = 3.6V FLASH = GND FLASH = High, R SET = 53.6k. FLASH = High. Guaranteed by design. V FB = 0.3V V IN = 3.6V, FB within 90% of regulation
0.7 55 162 400 0.5 0.4
mV mV mV A V V
0.5 500
A s
o
C FLASH = High
3.6
s
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
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PIN DESCRIPTION
PIN PIN NAME NUMBER 1 2 VIN C1
DESCRIPTION Input Voltage for the charge pump. Decouple with 4.7F ceramic capacitor close to the pins of the IC. Positive input for the external flying capacitor. Connect a ceramic 1F capacitor close to the pins of the IC. Negative input for the external flying capacitor. Connect a ceramic 1F capacitor close to the pins of the IC. Logic input to toggle operation between FLASH and TORCH mode. In TORCH mode FB is regulated to the internal 50mV reference. In FLASH mode FB reference voltage can be adjusted by changing the resistor from RSET pin to ground. Choose the external current sense resistor (R SENSE) based on desired current in TORCH mode. This pin does not have an internal pull-up/pulldown; do not leave this pin floating. Shutdown control input. Connect to VIN for normal operation, connect to ground for shutdown. This pin does not have an internal pull-up/pull-down; do not leave this pin floating. Connect a resistor from this pin to ground. When in FLASH mode (FLASH = High) this resistor sets the current regulation point according to the following: VFB = RSET*14uA/5 (Flash Mode) Feedback input for the current control loop. Connect directly to the current sense resistor. Internal ground pin. Control circuitry returns current to this pin. Power ground pin. Flying capacitor current returns through this pin. Charge Pump Output Voltage. Decouple with an external capacitor. At least 1F is recommended. Higher capacitor values reduce output ripple
3
C2
4
FLASH
5
EN
6
RSET
7 8 9 10
FB SGND PGND VOUT
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
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FUNCTIONAL DIAGRAM
RSET BLOCK RSET 6 RSET
RSET REF=
CLK RSET REF BG REF + - 1.26V
RESISTOR TAPS
+ -
MUX 2x1 50mV 0 s
1
FB REF + FB 7 SGND 8 FB COM P
COUNTER 32 COUNT
FB COMP
CLR
SET DOMINANT S 0 R
{}
RSET 5
x 14A
ONE SHOT
FLASH 4 FLASH=1, S=1, RSET REF FLASH=0, S=0, 50mV
EN 5 VIN 1 MODE SWITCH 0 =1X 1=2X
135C ON 145C OFF
THERMAL FAULT OVER TEMP COMP
CHARGE PUMP SWITCHES
C1 C2 VOUT
2.4MHZ CLK
CLK
PGND
THEORY OF OPERATION The SP7685 is a charge pump regulator designed for converting a Li-Ion battery voltage of 2.7V to 4.2V to drive a white LED used in digital still camera Flash and Torch applications. The SP7685 has two modes of operation which are pin-selectable for either Flash or Torch. Flash mode is usually used with a pulse of about 200 to 300 milliseconds to generate a high intensity Flash. Torch can be used continuously at a lower output current than Flash and is often used for several seconds in a digital still camera "movie" mode. The SP7685 also has two modes of operation to control the output current: the 1X mode and 2X mode. Operation begins after the enable pin EN receives a logic high, the bandgap reference wakes up after 200s, and then SP7685 goes through a soft-start mode designed to reduce inrush current. The SP7685 starts in the 1X mode, which acts like a linear regulator to control the output current by continuously monitoring the feedback pin FB. In 1X mode, if the SP7685 auto detects a dropout condition, which is when the FB pin is below the regulation point for more than 32 cycles of the internal clock, the SP7685 automatically switches to the 2X mode. The SP7685 remains in the 2X mode until one of four things happens: 1) the enable pin EN has been toggled, 2) the Flash pin has changed from high to low, 3) VIN is cycled or, 4) a thermal fault occurs. The 2X mode is the charge pump mode where the output can be pumped as high as two times the input voltage, provided the output does not exceed the maximum voltage for the SP7685, which is internally limited to about 5.5V. In the 2X mode, as in the 1X mode, the output current is regulated by the voltage at the FB pin.
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
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THEORY OF OPERATION In the Torch mode, (Flash = GND) the Flash pin is set to logic low and the SP7685 FB pin regulates to 50mV output: VFB = 50mV (Torch Mode) When in Flash mode, (Flash = VIN), the FB regulation voltage is set by the resistor RSET connected between the RSET pin and SGND and the equation: VFB = RSET * 14A / 5 (Flash Mode) Where 14A is an internal regulated current and 5 is an internal factor used to scale the VSET voltage to the VFB voltage. Typical values of RSET are 140K to 35K for a range of VFB = 400mV to 100mV in Flash mode. tion circuitry turns off the output switches to prevent damage to the device. If the temperature drops back down below 135 degrees Celsius, the part automatically recovers and executes a soft start cycle. OVERVOLTAGE PROTECTION The SP7685 has over voltage protection. If the output voltage rises above the 5.5V threshold, the over voltage protection shuts off all of the output switches to prevent the output voltage from rising further. When the output decreases below 5.5V, the device resumes normal operation.
OVERCURRENT PROTECTION The over current protection circuitry monitors the average current out of the VOUT pin. If the average output current exceeds approximately 1.6 Amps, then the overcurrent protection circuitry shuts off the output switches to protect the chip.
The output current is then set in either Flash or Torch mode by the equation: IOUT = VFB / RSENSE FLASH TIMEOUT PROTECTION
BRIGHTNESS CONTROL USING PWM Due to the high currents typically available in Flash mode, it is necessary to protect the white LED from damage if left on too long. The SP7685 has a timeout in Flash mode of approximately 2.6 seconds after which it will shut down operation. Operation will not begin again in Flash mode until the Enable pin or Flash pin have been set Low and then High again. Dimming control can be achieved by applying a PWM control signal to the EN pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. While the operating frequency range of the PWM control is from 60Hz to 700Hz, the recommended maximum brightness frequency range of the PWM signal is from 60Hz to 200Hz. A repetition rate of at least 60Hz is required to prevent flicker.
OVERTEMPERATURE PROTECTION When the temperature of the SP7685 rises above 145C, the overtemperature protec-
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
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APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
300
Output Current (mA)
SP7685 Torch Output Current
Output Current (mA)
900 850 800 750 700 650 600 550 500 450 400
SP7685 700mA Flash output Current
250 200 150 -40C 100 50 0 3.0 25C 85C
-40C 25C 85C
3.2
3.4
3.6
3.8
4.0
4.2
Input Voltage (V)
3.0
3.2
3.4
3.6
3.8
4.0
4.2
Input Voltage (V)
1100 1000 900 800 700 600 500 400 300 200 100 0 3.0 3.2
SP7685 Output Current
100 90 80 70 60 50 40 30 20 10 0 3.0 3.2
SP7685 Output Efficiency
Output Current (mA)
1000mA,Vf=3.31V PWF1 700mA,Vf=3.24V PWF1 700mA,Vf=3.92V AOT 200mA,Torch Mode
Efficiency (%)
1000mA,Vf=3.31V PWF1 700mA,Vf=3.18V PWF1 700mA,Vf=3.92V AOT 200mA,Torch
3.4
3.6
3.8
4.0
4.2
3.4
3.6
3.8
4.0
4.2
Input Voltage (V)
Input Voltage (V)
SP7685 VFB vs RSET
450 400 350 300
VFB (mV)
250 200 150 100 50 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Measured Calculated
RSET (K)
Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver (c) 2006 Sipex Corporation
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APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
EN VOUT
EN VOUT
VFB IOUT 1A/div
VFB IOUT 1A/div
Torch in 1X to Flash in 1X Mode, V IN=4.2V
Torch in 1X to Flash in 2X Mode, V IN=3.6V
EN VOUT
EN VOU VFB
VFB IIN 1A/div
IIN 1A/div
Start Up 200mA Torch VIN=3.6V, VOUT=3.1V
Start Up 1000mA Flash VIN=3.6V, VOUT=3.8V
EN VOU VFB IIN 1A/div
EN
VOUT
VFB
Start Up 700mA Flash V IN=3.6V, VOUT=3.6V
Date: 6/20/06 Rev T
Flash Mode TimeOut Circuit at 2.6sec. VIN=4.2V, IOUT=1A
SP7685, 1.2A Buck/BoostCharge Pump LED Driver (c) 2006 Sipex Corporation
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APPLICATION INFORMATION
VIN =3.6V, Typical Application Circuit, TA = 25C unless otherwise noted.
Input Ripple
Input Ripple
Output Ripple
Output Ripple
Ripple 1X Torch 200mA, V IN=4.2V
Ripple 2X Torch 200mA, V IN=3.0V
Input Ripple
Input Ripple
Output Ripple
Output Ripple
Ripple 1X Flash 700mA, V IN=4.2V
Ripple 2X Flash 700mA, V IN=3.6V
Input Ripple
Input Ripple
Output Ripple
Output Ripple
Ripple 1X Flash 1000mA, V IN=4.2V
Date: 6/20/06 Rev T
Ripple 2X Flash 1000mA, V IN=3.6V
(c) 2006 Sipex Corporation
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
8
COMPONENT SELECTION The SP7685 charge pump circuit requires three capacitors: 10F input, 10F output and 1F fly capacitor are typically recommended. For the input capacitor, a value of 10F will help reduce input voltage ripple for applications sensitive to ripple on the battery voltage. All the capacitors should be surface mount ceramic for low lead inductance necessary at the 2.4MHz switching frequency of the SP7685 and to obtain low ESR, which improves bypassing on the input and output and improves output voltage drive by reducing output resistance. Ceramic capacitors with X5R or X7R temperature grade are recommended for most applications. A selection of recommended capacitors is included in Table 1 below.
Manufacturer's Website TDK: www.tdk.com TDK: www.tdk.com TDK: www.tdk.com Murata: www.murata.com Murata: www.murata.com Murata: www.murata.com Part Number C1005X5R0J105M C1608X5R0J475K C2012X5R0J106M GRM155R60J105KE19B GRM188R60J475KE19 GRM21BR60J106KE19L
RESISTOR SELECTION The sense resistor RSENSE is determined by the value needed in the Torch mode for the desired output current by the equation: RSENSE = VFB/ IOUT where VFB = 50mV (Torch Mode) Once the RSENSE resistor has been selected for Torch mode, the VFB voltage can be selected for Flash mode using the following equation: VFB = IOUT * RSENSE (Flash Mode) where IOUT is for Flash Mode.
Capacitance/ Voltage 1uF/6.3V 4.7uF/6.3V 10uF/6.3V 1uF/6.3V 4.7uF/6.3V 10uF/6.3V
CapacitorSize/ Type/Thickness 0402/X5R/0.5mm 0603/X5R/0.9mm 0805/X5R/1.35mm 0402/X5R/0.55mm 0603/X5R/0.9mm 0805/X5R/1.35mm
ESR @100kHz 0.03 0.02 0.02 0.03 0.02 0.02
Table 1: Recommended Capacitors
The input and output capacitors should be located as close to the VIN and VOUT pins as possible to obtain best bypassing, and the returns should be connected directly to the PGND pin or to the thermal pad ground located under the SP7685. The fly capacitor should be located as close to the C1 and C2 pins as possible. See typical circuit layout at the end of this section for details on the recommended layout. To obtain low output ripple, a value of 10F is recommended for COUT. For output currents of 500mA to 1.2A, the recommended CFC fly capacitor value of 1F should be used. Output currents in Flash of 100mA to 400mA can use a 0.47F CFC but a minimum 4.7F COUT is still needed.
Date: 6/20/06 Rev T
Next, the RSET resistor can be selected for Flash mode using the following equation: RSET =
(14uA )* 5
VFB
(Flash Mode)
For an example of 200mA Torch mode and 700mA Flash mode, the values RSENSE = 0.22, VFB = 155mV (Flash Mode), and RSET =56K are calculated. The power obtained in the Flash mode would be: PFLASH = VFB *IOUT = 155mV*700mA = 109mW. The typical 0603 surface mount resistor is rated 1/10 Watt continuous power and 1/5
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
9
COMPONENT SELECTION Watt pulsed power, more than enough for this application. For other applications, the PFLASH power can be calculated and resistor size selected. The RSENSE resistor is recomPart Reference RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSET RSENSE RSENSE RSENSE RSENSE RSENSE RSENSE RSENSE Value 33k 39k 43k 47k 56k 62k 68k 82k 100k 110k 120k 150k 0.22 0.27 0.33 0.39 0.47 0.56 0.68 Tolerance 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 5% 105% 205%
mended to be size 0603 for most applications. The range of typical resistor values and sizes are shown here in Table 2.
Size 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0402 0603 0603 0603 0603 0603 0604 0605
Manufacturers any any any any any any any any any any any any Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay Panasonic or Vishay
Table 2: Resistor values and sizes
EVALUATION BOARD CIRCUIT LAYOUT
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
(c) 2006 Sipex Corporation
10
PACKAGE: 10 PIN DFN
D D/2 o E/2
A
E
(A3) A1
Seating Plane
SIDE VIEW
Pin1 Designator to be within this INDEX AREA (D/2 x E/2)
TOP VIEW
D2 D2/2
1 2 3 4 5
INDEX AREA (D/2 x E/2)
E2/2 E2
L
10 9 8 7 6
K e b
BOTTOM VIEW
3x3 10 Pin DFN SYMBOL
JEDEC MO-229
VARIATION VEED-5 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 0.032 0.036 0.039 0.000 0.001 0.002 0.008 REF 0.008 0 14 0.008 0.010 0.012 0.119 BSC 0.087 0.106 0.119 BSC 0.056 0.069 0.020 BSC 0.012 0.016 0.020 JL Aug09-05 / RevA
(c) 2006 Sipex Corporation
Dimensions in Millimeters: Controlling Dimension MIN 0.80 0.00 MAX 1.00 0.05 14 0.30 2.70 1.75 0.50
A A1 A3 K o
NOM 0.90 0.02 0.20 REF 0.20 0 b 0.18 0.25 D 3.00 BSC D2 2.20 E 3.00 BSC E2 1.40 e 0.50 BSC L 0.30 0.40 SIPEX Pkg Signoff Date/Rev:
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
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ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP7685ER-L ............................................... -40C to +85C ....................................... (Lead Free) 10 Pin DFN SP7685ER-L/TR ........................................ -40C to +85C ....................................... (Lead Free) 10 Pin DFN
/TR = Tape and Reel Pack quantity is 3,000 for DFN.
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Date: 6/20/06 Rev T SP7685, 1.2A Buck/BoostCharge Pump LED Driver (c) 2006 Sipex Corporation
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