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(R)
SP6687
4 Channel Charge Pump White LED Driver
GND C2N
10
C2P
FEATURES High Efficiency > 90% Support up to 4 White LEDs with current matching Three Charge Pump Modes: X1, X1.5, X2 Soft Start Function Short Circuit Protection Output Overvoltage Protection Thermal Shutdown Programmable LED drive capability PWM Dimming Control 1MHz Fixed Frequency Oscillator Low 1A Shutdown Current Pin Compatible with SC604
12 LED4 LED3 LED2 LED1 13 14 15 16 1
11
C1N
9 8 C1P VIN VOUT ISET 7 6 5 4
SP6687
16 Pin QFN
2
3
CTRL0
CTRL1
Pin 1 Orientation
Now Available in Lead-Free Packaging APPLICATIONS Mobile phones White LED Backlighting Camera Flash LED lighting
DESCRIPTION The SP6687 is a compact, highly efficient and highly integrated 4 channel charge pump white LED driver. It can support from 1 to 4 White LEDs and is optimized for Li-Ion battery applications. Current matching allows all 4 LEDs to maintain consistent brightness. Users can control White LEDs by three programming bits. Each channel can support up to 30mA of current. This device is available in a 4mm x 4mm, 16 pin QFN package. TYPICAL APPLICATION CIRCUIT
C1 1F 8 7 CIN 1F 2 CTRL0 3 4 5 RSET CTRL1 CTRL2 ISET GND 12 1 VIN EN C1P 9 C1N 11
C2 1F 10 C2N VOUT 6
C2P
(R)
Li-ion Battery
SP6687
CTRL2
EN
LED1 16 LED2 15 LED3 LED4 14 13
COUT 1F
Typical Application Circuit for 4-White LEDs
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
1
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.
Input Voltage.....................................................-0.3 to 6V Output Voltage..................................................-0.3 to 6V Power Dissipation, PD @ TA = 25C QFN-16L 4x4...........................................................2.5W Package Thermal Resistance QFN-16L 4x4, OJA................................................40C/W
Junction Temperature Range...............-40C to 125C Storage Temperature ......................... -65C to 150C Operating Temperature ....................... -40C to 85C ESD Susceptibility Human Body Model...............................................2kV Machine Model.....................................................200V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified: VIN = 2.85V to 5.5V, C1 = C2 =1.0F (ESR = 0.03, TA = 25C)
PARAMETER Input Supply Voltage Under Voltage Lockout Threshold Under Voltage Lockout Hysteresis
MIN 2.5 1.8
TYP
MAX 5.5
UNITS V V mV
CONDITIONS
2.2 50
2.4
VIN Rising
18.5 Current into LEDs 1, 2, 3, and 4 4.5 2 2 Quiescent Current Quiescent Current in Shutdown ILEDAccuracy (Note 1) Current Matching (Note 2) 1x mode to 1.5x mode Transition Voltage (V IN Falling) 1.5x mode to 2x mode Transition Voltage (V IN Falling) Oscillator Frequency Input Current Limit 0.8 250
20 5
21.5 5.5 20 30
mA mA mA mA mA A % % V
R SET = 24.0k R SET = 91.0k 2.7V < VIN < 5.5V 3.1V < VIN < 5.5V FOSC = 1MHz, IOUT = 0mA VIN = 4.5V, En Pin = ZeroV 2mA < ILED < 30mA 2mA < ILED < 30mA VLED = 3.5V, IOUT = 80mA ILED1 = I LED2 = ILED3 = ILED4 = 20mA VLED = 3.5V, IOUT= 80mA ILED1 = I LED2 = ILED3 = ILED4 = 20mA
3 1 2 1 3.75
4 10 7.5 5 TBD
2.65 1.0 400
2.8 1.2 650
V MHz mA
Short Circuit applied from VOUT to GND Open circuit at any LED that is programmed to be in the ON state
Output Over Voltage Protection
5.5
6
V
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
2
ELECTRICAL CHARACTERISTICS
Unless otherwise specified: VIN = 2.85V to 5.5V, C1 = C2 =1.0F (ESR = 0.03, TA = 25C)
PARAMETER Input High Threshold Input Low Threshold Input High Current Input Low Current Thermal Shutdown Threshold Thermal Shutdown Hysteresis
MIN 1.5
TYP
MAX
UNITS V
CONDITIONS Input High Logic threshold (EN, CTRL0, CTRL1, CTRL2) Input Low Logic threshold (EN, CTRL0, CTRL1, CTRL2) VIH = VIN VIL= GND
0.4 1 1 140 150 10 180
V A A C C
Note 1: ILED(ERR) =
ILED(MEA) - ILED(SET) X 100% ILED(SET)
Note 2: Current Matching refers to the difference in current from one LED to the next. (ILED Current Matching ILED(MAX) - ILED(MIN) ILED(MAX) + ILED(MIN) X 100%)
FUNCTIONAL DIAGRAM
C1P C1N C2P C2N
VIN GND
1x/1.5x/2x Charge Pump
1MHz
1MHz Oscillator
VOUT
Mode Decision
I-Setting
ISET
ISET
LED1 ISET EN Bandgap VREF LED2 LED3 LED4 CTRL0 CTRL1 CTRL2 Decoder
306mV
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
3
PIN DESCRIPTION
PIN # 1 2 3 4 5 6 7 8 9 10 11 12 13 to 16 Exposed Pa d
PIN NAME EN CTRL0 CTRL1 CTRL2 ISET VOUT VIN C1P C1N C2N C2P GND LED1 to 4 GND Chip Enable (Active High)
DESCRIPTION
Output Control Bit 0 (See table 1) Output Control Bit 1 (See table 1) Output Control Bit 2 (See table 1) LED current is set by the value of the resistor RSET connected from the ISET pin to ground. Do not short the ISET pin. Voltage for ISET is typically 1.1V. Output Voltage Source for connection to the LED anodes. Power Input Voltage Positive Terminal of Bucket Capacitor 1 Negative Terminal of Bucket Capacitor 1 Negative Terminal of Bucket Capacitor 2 Positive Terminal of Bucket Capacitor 2 Ground Current Sink for LED. (If not in use, pin may be left open, grounded, or connected to VIN) Exposed pad should be soldered to PCB board and connected to GND
GND
C2N
10
C2P
12 LED4 LED3 LED2 LED1 13 14
11
C1N
9 8 7 C1P VIN VOUT ISET 6 5 4
GND 15 16 1 2 3
CTRL1
CTRL0
Pin 1 Orientation
TOP VIEW
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
CTRL2
EN
(c) Copyright 2005 Sipex Corporation
4
THEORY OF OPERATION
The SP6687 is a high efficiency charge pump white LED driver. It provides 4 channels of low drop-out voltage current source to regulate the current for 4 white LEDs. For high efficiency, the SP6687 implements 3 modes of charge pump: x1/x1.5/x2 modes. An external RSET is used to set the current level of the White LEDs. SP6687 has an input current regulation circuit to reduce the input ripple. Soft Start The SP6687 includes a soft start circuit to limit the inrush current at power on and mode switching. The soft start circuit holds the input current level long enough for output capacitor COUT to reach a desired voltage level. When the soft start turns off, the SP6687 will not sink current spiking from VIN. Mode Decision The SP6687 uses a smart mode decision method to select the working mode for maximum efficiency. The mode decision circuit senses the output and LED voltage for up/down selection. Dimming Control CTRL0, CTRL1 and CTRL2 are used to control the on/off of correlated White LEDs. When an external PWM signal is connected to the control pin, the brightness of the white LEDs is adjusted by the duty cycle. LED Current Setting The current flowing through White LEDs connected to the SP6687 can be set by RSET. Every current that flows through each respective White LED is 440 times greater than the current of RSET. The white LED current can be estimated by following equation: where VISET =1.1V, and RSET is the resistance connected from ISET to GND. ILED =440x V ( RISET )
SET
Thermal Shutdown The SP6687 provides a high current capability to drive 4 white LEDs. A thermal shutdown circuit is needed to protect the chip from thermal damage. When the chip reaches the shutdown temperature of 150C, the thermal shutdown circuit turns off the chip to prevent thermal accumulation in the chip. Overvoltage Protection SP6687 regulates the output voltage by controlling the input current. When the output voltage reaches the designated level, SP6687 reduces the input current. Subsequently, the output voltage regulation also serves as an overvoltage protection circuit. Short Circuit Protection A current limiting circuit is also included in the SP6687 for short circuit protection. Whenever the output sources a dangerously high current, the current limiting circuit takes over the output regulation circuit and reduces the output current to an acceptable level.
APPLICATION INFORMATION
C2 1F 11 C2P
(R)
C1 1F 8 C1P 9 C1N
7 CIN 1F 1
VIN EN
10 C2N VOUT 6
Li-ion Battery
2 CTRL0 3 CTRL1 4 CTRL2 5 RSET ISET
SP6687
COUT LED1 16 LED2 15 LED3 14 1F
LED4 13 GND 12
Typical Application Circuit For 3-White LEDs
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
5
APPLICATION INFORMATION
C1 1F 8 7 VIN C1P 9 C1N 11 C2P
(R)
C2 1F 10 C2N VOUT 6
Li-ion Battery
CIN 1F
1
EN
SP6687
LED1 16 LED2 LED3 GND 12 15 14
COUT 1F
2 CTRL0 3 CTRL1
4 CTRL2 5 RSET ISET
LED4 13
Typical Application Circuit for 2-White LEDs
Control Inputs CTRL2 0 0 0 0 1 1 1 1 CTRL1 0 0 1 1 0 0 1 1 CTRL0 0 1 0 1 0 1 0 1 LED4 OFF OFF OFF ON OFF OFF ON OFF
Output Status LED3 OFF OFF ON OFF OFF ON ON OFF LED2 OFF ON OFF OFF ON ON ON OFF LED1 ON OFF OFF OFF ON ON ON OFF
Table 1. Typical application circuit for PWM dimming using a DC voltage into ISET.
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
6
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 9: SP6687 Efficiency vs. Input voltage at ILED = 60mA, VF = 3.3V (falling voltage)
Figure 10: SP6687 Efficiency vs. Input voltage at ILED = 60mA, VF = 3.6V (falling voltage)
Figure 11: SP6687 Efficiency vs. Input voltage at ILED = 80mA, VF = 3.3V (falling voltage)
Figure 12: SP6687 Efficiency vs. Input voltage at ILED = 80mA, VF = 3.6V (falling voltage)
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
7
APPLICATION INFORMATION
Selecting Capacitors To get better performance from the SP6687, the selection of appropriate capacitors is very important. These capacitors determine some parameters such as input and output ripple, power efficiency, maximum supply current by the charge pump and startup time. To reduce the input and output ripple effectively, low ESR ceramic capacitors are recommended. To reduce output ripple, increasing the output capacitance COUT is generally necessary. However, this will increase the startup time of the output voltage. For LED driver applications, the input voltage ripple is more important than output ripple. Input ripple is controlled by the input capacitor CIN -- increasing the value of input capacitance can further reduce the ripple. Practically, the input voltage ripple depends on the impedance of the power supply. If a single input capacitor CIN cannot satisfy the requirement of the application, it is necessary to add a low-pass filter. Figure 1 shows a CR-C filter used on the SP6687. The input ripple can be reduced to less than 30mVp-p when driving 80mA of output current.
(R)
Figure 2 shows the typical value of RSET versus average LED current and Table 2 shows the values of RSET for a fixed LED current.
Typical Curve for RSET vs. Avg. LED Current
300 250
RSET Value (k_)
200 150 100 50 0 0 5 10 15 20 25 30 LED Current (mA)
Figure 2. The typical curve of RSET vs. LEDs average current.
ILED (mA) 5
RSET (k ) 91.0 47.9 32.7 24.0 19.6 16.4
Nearest Standard Value for RSET (k ) 91.0 47.5 32.4 24.0 19.6 16.5
V IN 2.2F
1.0
V IN
SP6687
10 15 20
2.2F
Figure 1. C-R-C filter used to reduce input ripple. The flying capacitors C1 and C2 determine the supply current capability of the charge pump and influence the overall efficiency of the system. Lower values will improve efficiency, but will limit the current to the LEDs at low input voltages. For 4 X 20mA load over the entire input range of 2.7 to 5.5V, a capacitor of 1F is optimal. Setting the LED Current The SP6687 can be set to a fixed LED current by a resistor RSET connected from ISET to GND. RSET establishes the reference current and mirrors the current into LED1, LED2, LED3, and LED4. The current into each LED is about 440 times the current that flows through RSET. The approximate setting formula is given as follows: ILED= 484(V) RSET()
25 30
Table 2. RSET Value Selection
If maximum accuracy is required, a precision resistor is needed. The following equation shows how to calculate the error: ILED(ERR) = ILED(MEAS) - ILED(SET) X 100% ILED(SET) Where ILED(MEAS) is practical measured LED current and ILED(SET) is the LED current which is determined by RSET.
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
8
APPLICATION INFORMATION
LED Current Setting with NMOS LED current setting control can also be achieved by using an external NMOS transistor to change the equivalent resistor of the ISET pin. Figure 3 illustrates this application circuit which has 3 bit signals and can set 8 different levels of LED current. Table 3 shows the relation between the equivalent resistor of the ISET pin and the respective control signal. LED Dimming Control Methods The SP6687 uses two methods to achieve LED dimming control. These methods are detailed below. PWM Dimming The first dimming method utilizes a PWM control signal into CTRL0, CTRL1, and CTRL2. Table 1 shows the relation between CTRLx and the 4 LED current states. For example, when CTRL1 and CTRL2 are at logic high and CTRL0 receives a PWM signal then 4 LEDs will be dimmed simultaneously. The average LED current can be derived by using a known PWM signal value. When the PWM signal logic is low the current can be set at a fixed value with the RSET resistor. The following equation will give the approximate value of the LED current: TOFF X ILED(ON) ILED(AVG) = TPWM Where TPWM is the period of the PWM dimming signal. TOFF is the time of the PWM signal at low. ILED(ON) is LED ON state current.
VIN
(R)
SP6687
R1 ISET S1 R4 R2 S2
R3 S3
Figure 3. Typical application circuit for setting LED current using an NMOS transistor to set RSET
S1 0 0 0 0 1 1 1 1 S2 0 0 1 1 0 0 1 1 S3 0 1 0 1 0 1 0 1 Equivalent Resister of ISET pin (RSET) RSET=R4 RSET=R3//R4 RSET=R2//R4 RSET=R2//R3//R4 RSET=R1//R4 RSET=R1//R3//R4 RSET=R1//R2//R4 RSET=R1//R2//R3//R4
(R)
(R)
SP6687 CTRL2 CTRL1 CTRL0 EN PWM
LED LED ON OFF
Figure 4. Typical application circuit for PWM dimming when driving 4 LEDs.
VIN
Table 3. Control signal and equivalent resistor of the ISET pin.
SP6687 CTRL2 CTRL1 CTRL0 EN PWM LED LED ON OFF
Figure 5. Typical application circuit for PWM dimming when driving 3 LEDs.
Date: 11/15/05 SP6687 4Channel Charge Pump White LED Driver (c) Copyright 2005 Sipex Corporation
9
APPLICATION INFORMATION
VIN
(R)
Dimming using a DC voltage added to ISET
SP6687 CTRL2 CTRL1 CTRL0 EN PWM LED LED ON OFF
Using an analog input voltage VADJ via a resistor RADJ that connects to the ISET pin is another method for dimming control of LEDs. Figure 7 shows the application circuit. For this application the LED current can be derived from the following equation: ILED = 440 X [1.1 x (1/RSET + 1/RADJ) - VADJ/RADJ]
Figure 6. Typical application circuit for PWM dimming when driving 2 LEDs. Due to the 100s delay time between mode transfers, the duty cycle of the dimming frequency should not exceed the maximum duty cycle on the CTRLx pins. For best performance it is recommended to keep the dimming frequency between 200Hz and 1kHz. When the duty cycle is exceeded, the SP6687 cannot transfer modes properly. The following equation shows the relation between maximum duty of the CTRLx pins and the PWM dimming frequency: DMAX =(1-100 x10 -6 x FD) Where DMAX is the Maximum Duty of CTRLX and FD is the PWM Dimming Frequency.
VADJ
RADJ
(R)
RSET SP6687 ISET CTRL2 CTRL1 CTRL0 EN
VIN
Figure 7. Typical application circuit for PWM dimming using a DC voltage into ISET.
Dimming Frequency (Hz) 1K 900 800 700 600 500 400 300 200
CTRLX Maximum Duty 0.90 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98
ILED Minimum Duty 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02
VADJ
2.5V 1.6V 0.8V 0V 20mA
13mA ILED 0mA 6.5mA
Figure 8. SP6687 dimming control application using a DC voltage into ISET.
Table 4. Dimming frequency relative to Min/Max duty.
Figure 8 shows the relation between VADJ and ILED of a typical application example, with VADJ from 0 to 2.5V, RSET = 43k and RADJ = 55k.
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
10
PACKAGE: 16 PIN QFN
D
K
13 14
D2
15 16
INDEX AREA (D/2 x E/2)
Pin1 Designator to be within this INDEX AREA (D/2 x E/2)
1
E
2
E2
3
4
K e b
TOP VIEW
L
BOTTOM VIEW
O
A A3 Seating Plane A1
SIDE VIEW
4x4 16 Pin QFN
SYMBOL
JEDEC MO-220
Variation VGGC-4
Millimeters Controlling Dimension MIN 0.80 0.00 0.20 0 0.25 2.20 2.20 0.45 NOM 0.90 0.02 0.20 REF 0.30 4.00 BSC 2.40 4.00 BSC 2.40 0.65 BSC 0.55 MAX 1.00 0.05 14 0.35 2.60 2.60 0.65
A A1 A3 K o b D D2 E E2 e L
Inches Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 0.031 0.035 0.039 0.000 0.001 0.002 0.008 REF 0.008 0 14 0.010 0.012 0.014 0.157 BSC 0.087 0.094 0.102 0.157 BSC 0.087 0.094 0.102 0.026 BSC 0.018 0.022 0.026 JL Oct31-05/Rev A
SIPEX Pkg Signoff Date/Rev:
Date: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
11
ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP6687ER1-L/TR ....................................... -40C to +85C ........................................ 16 Pin 4mmx4mm QFN
Available in lead-free packaging only.
-L = lead-free /TR = Tape and Reel Pack quantity is 3,000 for QFN.
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: 11/15/05
SP6687 4Channel Charge Pump White LED Driver
(c) Copyright 2005 Sipex Corporation
12

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