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(R)
Preliminary
SP6685
Charge Pump LED Driver For Camera Flash
FEATURES VIN 1 10 VOUT High Output Current Charge Pump: 700mA C1 2 9 PGND Adjustable FLASH mode SP6685 x1 and x2 Automatic Modes for High Efficiency 8 SGND C2 3 10 Pin DFN Minimum External Components: No Inductors 7 FB FLASH 4 High Frequency Operation: 2.4 MHz 6 RSET EN 5 Low 50mV reference for low loss sensing 1 A shutdown current Now Available in Lead Free Packaging PWM Dimming Control Over voltage protection on output APPLICATIONS Over current protection LED Torch/Flash for Cell Over temperature protection Phones, DSCs, and Camcorders Space Saving 10-pin 3mm x 3mm DFN Generic Lighting/Flash/Strobe Package Applications DESCRIPTION The SP6685 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 SP6685 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 SP6685 is offered in 10-pin DFN package. TYPICAL APPLICATION CIRCUIT
VIN (2.7 - 4.3V) VIN CFC 1F C1 C2 FLASH EN
(R)
CIN 4.7F
VOUT COUT 1F D1 1W LED
SP6685 PGND SGND FB RSET
TORCH/FLASH ENABLE
VREF = 50 - 150mV RSET 88.7K RSENSE 0.22
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
VIN - VOUT ....................................................................... -0.3V to 6V Output Current Pulse (Flash) ................................. 1A Output Current Continuous (Torch) ..................... 0.4A Storage Temperature ...................... -65C to +150C Operating Temperature ..................... -40C to +85C EN ................................................................ 0V to 7V ESD. ........................................................... 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 =3.6, CIN = 4.7F, CFC = COUT = 1.0F. VSHDN = VIN, typical values at 25C. The denotes the specifications which apply over the full operating range unless otherwise noted.
PARAMETER Operating Input Voltage Quiescent Current MIN. 2. 7 0. 5 2 Shutdown Current Oscillator Frequency Charge Pump Equivalent Resistance (x2 mode) Charge Pump Equivalent Resistance (x1 mode) FB Reference Voltage FB Reference Voltage FB Pin Current EN, FLASH Logic Low EN, FLASH Logic High EN, FLASH Pin Current VOUT Turn-on Time Thermal Shutdown Temperature Thermal Hysteresis 250 145 10 1.3 0.5 500 142 45 2.4 5 0.6 150 50 0.8 158 55 0. 5 0.4 1 A MHz mV mV A V V A s C C VIN = 3.6V, FB within 90% of regulation VFB = 0V, VIN= 3.6V VIN= 3.6V FLASH = VIN RSET = 100K FLASH = GND VFB = 1V TYP. MAX. 4.3 2 UNITS V mA VIN = 2.7 - 4.3V FLASH = 0V, Iload = 100A FLASH = VIN, 2x mode VIN = 4.3V, VEN = 0V CONDITIONS
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
2
PIN DESCRIPTION
PIN NUMBER 1 2 3 4 PIN NAME VIN C1 C2 FLASH DESCRIPTION Input Voltage for the charge pump. Decouple with 1F ceramic capacitor close to the pins of the IC. Positive input for the external fly capacitor. Connect a ceramic 1F capacitor close to the pins of the IC. Negative input for the external fly 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 (RSENSE) based on desired current in TORCH mode. The FLASH mode should be limited to 200ms to avoid overheating the charge pump. Shutdown control input. Connect to VIN for normal operation, connect to ground for shutdown. 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 = (1.26V/ RSET)*11.2K. 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. Fly capacitor current returns through this pin. Charge Pump Output Voltage. Decouple with an external capacitor. At least 1uF is recommended. Higher capacitor values reduce output ripple.
5 6
EN RSET
7 8 9 10
FB SGND PGND VOUT
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
3
TYPICAL PERFORMANCE CHARACTERISTICS
300
Torch Mode 200mA Iout
900 800 700
Flash Mode 700mA Iout
200
Iout (mA)
600
Iout (mA)
Vf = 3.0V
100
500 400 300 200 100
Vf = 3.3V Vf = 3.6V Vf = 3.9V
Vf = 3.3V Vf = 3.6V Vf = 3.9V Vf = 4.2V
0 3.0 3.2 3.4 3.6 Vin (V) 3.8 4.0 4.2
0 3.0 3.2 3.4 3.6 Vin (V) 3.8 4.0 4.2
Figure 1. Torch Mode Output Current
Figure 2. Flash Mode Output Current
100 90
Efficiency (%)
Torch Mode 200mA Efficiency
100 90
Flash Mode 700mA Efficiency
70 60 50 40 3.0 3.2 3.4
Vf = 3.0V Vf = 3.3V Vf = 3.6V Vf = 3.9V
Efficiency (%)
80
80 70 60 50 40
Vf = 3.3V Vf = 3.6V Vf = 3.9V Vf = 4.2V
3.6 Vin (V)
3.8
4.0
4.2
3.0
3.2
3.4
3.6 Vin (V)
3.8
4.0
4.2
Figure 3. Torch Mode Efficiency
Figure 4. Flash Mode Efficiency
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
4
TYPICAL PERFORMANCE CHARACTERISTICS
Ch1 = EN
Ch1 = EN
Ch2 = VOUT Ch4 = lin (0.5A/div)
Ch2 = VOUT
Ch4 = lin (0.5A/div)
Figure 5. Startup 200mA Torch, VIN = 3.6V, VOUT = 3.2V
Figure 6. Startup 700mA Flash, VIN = 3.6V, VOUT = 3.6V
Ch1 = VIN (AC) Ch1 = VIN (AC) 50mA/div 50mA/div
Ch2 = VOUT (AC) 50mA/div
Ch2 = VOUT (AC) 50mA/div
Figure 7. Ripple 200mA Torch, VIN = 3.6V, VOUT = 3.2V.
Figure 8. Ripple 700mA Flash, VIN = 3.6V, VOUT = 3.6V.
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
5
FUNCTIONAL DIAGRAM
RSET BLOCK RSET 6 RSET
1.26V V= RSET
CLK RSET REF BG REF + - 1.25V
RESISTOR TAPS
+ -
MUX 2x1 50mV 0 s
1
FB REF + FB 7 SGN 8 FB COM P
COUNTER 32 COUNT
FB COMP
CLR
{ }x11.
SET DOMIANT S 0 R
2kohms
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 SP6685 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 SP6685 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 SP6685 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 200sec, and then SP6685 goes through a soft-start mode designed to reduce inrush current. The SP6685 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 SP6685 auto detects a dropout condition, which is when the FB pin is below the
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
6
THEORY OF OPERATION regulation point for more than 32 cycles of the internal clock, the SP6685 automatically switches to the 2X mode. The SP6685 remains in the 2X mode until one of four things happens: the enable pin EN has been toggled, the Flash pin has changed from high to low, VIN is cycled or 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 SP6685, which is internally limited to about 4.3V. In the 2X mode, as in the 1X mode, the output current is regulated by the voltage at the FB pin. In the Torch mode, (Flash = GND) the Flash pin is set to logic low and the SP6685 FB pin regulates to 50mV output: VFB = 50mV (Torch Mode) OVERTEMPERATURE PROTECTION When the temperature of the SP6685 rises above 145 degrees Celsius, the over temperature protection 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 SP6685 has over voltage protection. If the output voltage rises above the 4.3V 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 4.3V, the device resumes normal operation OVERCURRENT PROTECTION The over current protection circuitry monitors the average current out of the VOUT = 50mV (Torch Mode) pin. If the average output current exceeds approximately 1Amp, then the over current protection circuitry shuts off the output switches to protect the chip. 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 = (1.26V/ RSET)*11.2K (Flash Mode) Where 1.26V is the internal bandgap reference voltage and 11.2K is an internal resistance used to scale the RSET current. Typical values of RSET are 100K to 500K for a range of VFB = 150mV to 30mV in Flash mode. The output current is then set in either Flash or Torch mode by the equation: IOUT = VFB / RSENSE
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
7
COMPONENT SELECTION The SP6685 charge pump circuit requires 3 capacitors: input, output and fly capacitor, and a 1 F value is typically recommended. For the input capacitor, a larger value of 2.2 F or 4.7 F will help reduce input voltage ripple for applications sensitive to ripple on the battery voltage. All the capacitors should be ceramic to obtain low ESR, which improves bypassing on the input and output and improves output voltage drive by reducing output resistance. X5R or X7R Ceramic capacitors are recommended for most applications. A selection of recommended capacitors is included in Table 1. 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 SP6685. The fly capacitor should be located as close as possible to the C1 and C2 pins as possible. 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 Next, the RSET resistor can be selected for Flash mode using the following equation: RSET = (1.26V/ VFB)*11.2K (Flash Mode) For an example of 200mA Torch mode and 600mA Flash mode, the values RSENSE = 0.25, VFBREF = 150mV (Flash Mode), and RSET = 88.7K are calculated. The power obtained in the Flash mode would be: PFLASH = VFB *IOUT = 150mV*600mA = 90mW. The typical 0603 surface mount resistor is rated 1/10 watt continuous power and 1/5 watt pulsed power, more than enough for this application. For other applications, the PFLASH can be calculated from the resistor size selected. The RSENSE resistor is recommended to be size 0603 for most applications.
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)
Part Reference Part Number Value Size Manufacturers/ Website U1 SP6685ER 3x3mm DFN - 10 pin Sipex/www.sipex.cpm CIN GRM188R0J475KE19 4.7uF/6.3V 0603/X5R/0.9mm ht Murata/www.murata.com COUT, CF GRM155R60J105KE19B 1uF/6.3V 0402/X5R/0.5mm ht Murata/www.murata.com RSET 88.7K 0402 any RSENSE 0.22ohms 0603 any
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
8
PACKAGE: 10 PIN DFN
D D/2 A3
E/2
E
A1
Top View
A
Side View
D2
3x3 10 Pin DFN JEDEC MO-229 (VEED-5) VARIATION MIN NOM MAX SYMBOL A 0.8 0.9 1 A1 0 0.02 0.05 A2 0.55 0.65 0.8 0.20 REF A3 b 0.18 0.25 0.3 2.00 BSC D D2 2.2 2.7 0.5 PITCH e 3.00 BSC E E2 1.4 1.75 K 0.2 L 0.3 0.4 0.5 Note: Dimensions in (mm)
1
2
E2
K L e b
Bottom View
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
(c) Copyright 2004 Sipex Corporation
9
ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP6685ER .................................................. -40C to +85C ........................................................... 10 Pin DFN SP6685ER/TR ............................................ -40C to +85C .......................................................... 10 Pin DFN Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6685ER/TR = standard; SP6685ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 3,000 for DFN.
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Corporation
ANALOG EXCELLENCE
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: 12/15/04 SP6685 Charge Pump LED Driver for Camera Flash (c) Copyright 2004 Sipex Corporation
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