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SP6691
TM
Micro Power Boost Regulator Series White LED Driver
FEATURES Drives up to 6 LEDs @ 25mA Drives up to 8 LEDs @ 20mA High Output Voltage: Up to 30V Optimized for Single Supply, 2.7V - 4.2V Applications Operates Down to 1V High Efficiency: Greater Than 75% Low Quiescent Current: 20A Ultra Low Shutdown Current: 10nA Single Battery Cell Operation Programmable Output Voltage 1 switch (350mV at 350mA) Lead Free, RoHS Compliant Packages:
8 Pin DFN, 5 Pin TSOT or 5 Pin SOT23
NC FB NC SW
1 2 3 4 8
NC SHDN VIN GND
SP6691
8 Pin DFN
7 6 5
APPLICATIONS White LED Driver High Voltage Bias Digital Cameras Cell Phone Battery Backup Handheld Computers
DESCRIPTION The SP6691 is a micro power boost regulator that is specifically designed for powering series configuration white LED. The part utilizes fixed off time architecture and consumes only 10nA quiescent current in shutdown. Low voltage operation, down to 1V, fully utilizes maximal battery life. The SP6691 is offered in a 8 Pin DFN, 5-pin SOT-23 or 5 Pin TSOT package and enables the construction of a complete regulator occupying < 0.2 in2 board space. TYPICAL APPLICATION CIRCUIT
10H 2.7 to 4.2V L1 D1 SW
(R)
VIN SP6691 SHDN 4.7F C1 GND
C2 FB
2.2 F
Rb
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Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
VIN ....................................................................... 15V SW Voltage .............................................. -0.4 to 30V FB Voltage ......................................................... 2.5V All other pins ................................... -0.3 to VIN + 0.3V Current into FB ................................................. 1mA TJ Max ............................................................. 125C Operating Temperature Range ............ -40C to 85C Peak Output Current < 10us SW .................... 500mA Specifications are at TA = 25C, VIN = 3.3, VSHDN = VIN, temperature range, unless otherwise specified. PARAMETER Input Voltage Supply Current SYMBOL VIN IQ MIN 1.0 20 0.01 Reference Voltage FB Hysteresis VFB Input Bias Current Line Regulation Switch Off Time Switch Saturation Voltage Switch Current Limit SHDN Bias Current SHDN High Threshold (on) SHDN Low Threshold (off) Switch Leakage Current VFB HYST IFB Vo/ VI TOFF VCESAT ILIM ISHDN VIH VIL ISWLK 0.01 0.9 0.25 5 325 1.17 1.22 8 15 0.1 250 170 450 5 450 575 12 80 0.3 Storage Temperature ...................... -65C to +150C Power Dissipation. ......................................... 200mW 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.
denotes the specifications which apply over the full operating TYP MAX 13.5 30 1 1.27 UNITS V A A V mV nA %/V nS mV mA A V V A Switch Off, VSW = 5V VSHDN = 3.3V ISW = 325mA VFB = 1.22V 1.2 VIN 13.5V No Switching SHDN = 0V (off) CONDITIONS
ELECTRICAL CHARACTERISTICS
PIN DESCRIPTION
PIN NUMBER 1 2 3 3 5 6 7 8 PIN NAME NC FB NC SW GND VIN SHDN NC 8 PIN DFN DESCRIPTION No connect. Feedback. No connect. Switch input to the internal power switch Ground Input Voltage. Bypass this pin with a capacitor as close to the device as possible. Shutdown. Pull high (on) to enable. Pull low (off) for shutdown. No connect.
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
2
PIN DESCRIPTION
PIN NUMBER 1 2 3 4 5 PIN NAME SW GND FB SHDN VIN DESCRIPTION Switch input to the internal power switch. Ground Feedback Shutdown. Pull high (on) to enable. Pull low (off) for shutdown. Input Voltage. Bypass this pin with a capacitor as close to the device as possible.
FUNCTIONAL DIAGRAM
5 VIN SW 1
R1
R2 + X1 DISABLE SET 250ns ONE-SHOT R3 CLEAR X2 DRIVER + R4 GND POWER TRANSISTOR
Q1 FB 3
Q2
SHDN 4
Shutdown Logic
2
THEORY OF OPERATION Operation can be best understood by referring to the functional diagram above and the typical application circuit in the front page. Q1 and Q2 along with R3 and R4 form a band gap reference. The input to this circuit completes a feedback path from the high voltage output through a voltage divider, and is used as the regulation control input. When the voltage at the FB pin is slightly above 1.22V, comparator X1 disables most of the internal circuitry. Current is then provided by capacitor C2, which slowly discharges until the voltage at the FB pin drops below the lower hysteresis point of X1, about 6mV. X1 then enables the internal circuitry, turns on chip power, and the current in the inductor begins to ramp up. When the current through the driver transistor reaches about
Jun26-07 Rev D
450mA, comparator X2 clears the latch, which turns off the driver transistor for a preset 250nS. At the instant of shutoff, inductor current is diverted to the output through diode D1. During this 250nS time limit, inductor current decreases while its energy charges C2. At the end of the 250ns time period, driver transistor is again allowed to turn on which ramps the current back up to the 450mA level. Comparator X2 clears the latch, it's output turns off the driver transistor, and this allows delivery of L1's stored kinetic energy to C2. This switching action continues until the output capacitor voltage is charged to the point where FB is at band gap (1.22V). When this condition is reached, X1 turns off the internal circuitry and the cycle repeats.
(c) 2007 Sipex Corporation
Micro Power Boost Regulator Series White LED Driver
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
90 80 70 60 50 0 20 40
Vout = 12V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3 3V
13.0 12.5
Vout (V)
Vout = 12V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3 3V
Efficiency (%)
12.0 11.5 11.0 0 20 40 60 80 100 120 140 160 Iout (mA)
60
80 Iout (mA)
100
120
140
160
Figure 1. 12V Output Efficiency
Figure 2. 12V Output Load Regulation
90
Vout = 15V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3.3V Vi
16.0
Vout = 15V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3.3V Vin = 2.7V
Efficiency (%)
80
15.5
70
Vout (V)
15.0
60
14.5
50 0 20 40 60 80 100 120
14.0 0 20 40 60 80 100 120
Iout (mA)
Iout (mA)
Figure 3. 15V Output Efficiency
Figure 4. 15V Output Load Regulation
90 80 70 60 50 0 20
Vout = 18V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3 3V
19.0 18.5
Vout (V)
Vout = 18V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3 3V
Efficiency (%)
18.0 17.5 17.0
40 60 Iout (mA)
80
100
0
20
40 60 Iout (mA)
80
100
Figure 5. 18V Output Efficiency
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Figure 6. 18V Output Load Regulation
Micro Power Boost Regulator Series White LED Driver (c) 2007 Sipex Corporation
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
90
Vout = 21V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3 3V
22.0
Vout = 21V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3 3V
Efficiency (%)
80
21.5
Vout (V)
70
21.0
60
20.5
50 0 10 20 30 40 Iout (mA) 50 60 70
20.0 0 10 20 30 40 Iout (mA) 50 60 70
Figure 7. 21V Output Efficiency
Figure 8. 21V Output Load Regulation
90
Efficiency (%)
Vout = 24V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3 3V
25.0
Vout = 24V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3 3V
80 70 60 50 0 10 20 30 Iout (mA) 40 50 60
24.5
Vout (V)
24.0
23.5 23.0 0 10 20 30 Iout (mA) 40 50 60
Figure 9. 24V Output Efficiency
Figure 10. 24V Output Load Regulation
90 80
Efficiency (%)
Vout = 30V Efficiency
Vin = 5.0V Vin = 4.2V Vin = 3 3V
31.0 30.5
Vout (V)
Vout = 30V Load Regulation
Vin = 5.0V Vin = 4.2V Vin = 3 3V
70 60 50 40 0 5 10 15 Iout (mA) 20 25 30
30.0 29.5 29.0 0 5 10 15 Iout (mA) 20 25 30
Figure 11. 30V Output Efficiency
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Figure 12. 30V Output Load Regulation
(c) 2007 Sipex Corporation
Micro Power Boost Regulator Series White LED Driver
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
25
Shutdown Pin Current (uA)
10 8 6 4 2 0
Quiescent Current (uA)
20 15 10 5 0 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 Input Voltage (V) Tamb=-25C Tamb=25C Tamb=85C
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
Input Voltage (V)
Figure 13. Quiescent Current IQ vs. VIN
Figure 14. Shutdown Pin Current vs. VIN
600
Switch Saturation Voltage (mV)
400 350 300 250 200 150 100 50 0 -30 -10 10 30
Temperature (C)
500
Current Limit (mA)
400 300 200 100 0 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 Input Voltage (V)
50
70
90
Figure 15. IPK Current Limit vs. VIN
1.25
Feedback Voltage (V)
Figure 16. Switch Saturation Voltage VCESAT vs. Temperature (ISW = 450mA)
20 16
Iout/Idc (%)
1.24 1.23 1.22 1.21 1.20 -30
12 8 4
-10
10
30
Temperature (C)
50
70
90
0 0 20 40 60 80 100 PWM Duty Cycle (%)
Figure 17. Feedback Voltage vs. Temperature
Figure 18. Average IO vs. SHDN Duty Cycle (VIN=3.3V, Standard 4x20mA WLED Evaluation Board, PWM Frequency 100Hz
(c) 2007 Sipex Corporation
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
6
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
EN
VSW
VOUT IIN (0.5A/Div)
VOUT (AC)
IL (0.5A/Div)
Figure 19. Startup Waveform (VIN=3.3V, VOUT=15V, IOUT=20mA)
Figure 20. Typical Switching Waveforms (VIN=3V, VOUT=15V, IOUT=20mA)
IOUT (100mA/Div) VOUT (AC)
IL (0.5A/Div)
Figure 21. Load Step Transient (VIN=3V, VOUT=21V, 1 15mA Load Step
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
7
APPLICATION INFORMATION
Inductor Selection Capacitor Selection
For SP6691, the internal switch will be turned off only after the inductor current reaches the typical dc current limit (ILIM=450mA). However, there is typically propagation delay of 200nS between the time when the current limit is reached and when the switch is actually turned off. During this 200nS delay, the peak inductor current will increase, exceeding the current limit by a small amount. The peak inductor current can be estimated by: IPK = ILIM + VIN(MAX) L * 200nS
Ceramic capacitors are recommended for their inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. For the typical application, 4.7F input capacitor and 2.2F output capacitor are sufficient. The input and output ripple could be further reduced by increasing the value of the input and output capacitors. Place all the capacitors as close to the SP6691 as possible for layout. For use as a voltage source, to reduce the output ripple, a small feedforward (47pF) across the top feedback resistor can be used to provide sufficient overdrive for the error comparator, thus reduce the output ripple. Refer to Table 2 for some suggested low ESR capacitors. Table 2. Suggested Low ESR Capacitor
MANUF. PART NUMBER GRM32RR71E 225KC01B GRM31CR61A 475KA01B C3225X7R1E 225M C3216X5R1A 475K CAP SIZE /VOLTAGE /TYPE 2.2F /25V 4.7F /10V 2.2F /25V 4.7F /10V 1210 /X5R 1206 /X5R 1210 /X7R 1206 /X5R
The larger the input voltage and the lower the inductor value, the greater the peak current. In selecting an inductor, the saturation current specified for the inductor needs to be greater than the SP6691 peak current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. Choosing an inductor with low DCR decreases power losses and increase efficiency. Refer to Table 1 for some suggested low ESR inductors. Table 1. Suggested Low ESR inductor
MANUF. PART NUMBER DCR () 0.3 0.55 Current Rating (mA) 450 500
MURATA 770-436-1300 MURATA 770-436-1300
TDK 847-803-6100 TDK 847-803-6100
MURATA 770-436-1300 TDK 847-803-6100
LQH32CN100K11 (10H) NLC453232T-100K (10H)
LED Current Program
Diode Selection
A schottky diode with a low forward drop and fast switching speed is ideally used here to achieve high efficiency. In selecting a Schottky diode, the current rating of the schottky diode should be larger than the peak inductor current. Moreover, the reverse breakdown voltage of the schottky diode should be larger than the output voltage.
In the white LEDs application, the SP6691 is generally programmed as a current source. The bias resistor Rb, as shown in the typical application circuit is used to set the operating current of the white LED using the equation: Rb = VFB IF
where VFB is the feedback pin voltage (1.22V), I F is the operating current of the White LEDs. In order to achieve accurate LED current, 1%
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
APPLICATION INFORMATION: Continued precision resistors are recommended. Table 3 below shows the Rb selection for different white LED currents. For example, to set the operating current to be 20mA, Rb is selected as 60.4 , as shown in the schematic. Table 3. Bias Resistor Selection IF (mA) 5 10 12 15 20
Output Voltage Program
Table 4. Divider Resistor Selection VOUT (V) 12 15 18 21 30
Brightness Control
R1 ( ) 1M 1M 1M 1M 1M
R2 ( ) 113K 88.7K 73.2K 61.9K 42.2K
Rb ( ) 243 121 102 80.6 60.4
The SP6691 can be programmed as either a voltage source or a current source. To program the SP6691 as voltage source, the SP6691 requires 2 feedback resistors R1 & R2 to control the output voltage. As shown in Figure 22.
VIN
L1
D1
Dimming control can be achieved by applying a PWM control signal to the SHDN pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of the PWM signal. A 0% duty cycle corresponds to zero LED current and a 100% duty cycle corresponds to full load current. 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. The magnitude of the PWM signal should be higher than the minimum SHDN voltage high.
Open Circuit Protection
VOUT
C2 C1
5 VI N 4
R1
U1
1 SW 3
SP6691
SHDN G ND 2 FB
1.22V
R2
Figure 22. Using SP6691 as Voltage Source
When any white LED inside the white LED module fails or the LED module is disconnected from the circuit, the output and the feedback control will be open, thus resulting in a high output voltage, which may cause the SW pin voltage to exceed it maximum rating. In this case, a zener diode can be used at the output to limit the voltage on the SW pin and protect the part. The zener voltage should be larger than the maximum forward voltage of the White LED module.
The formula and table for the resistor selection are shown below: R1 =( VOUT 1.22 - 1 ) * R2
Micro Power Boost Regulator Series White LED Driver (c) 2007 Sipex Corporation
Jun26-07 Rev D
APPLICATION INFORMATION
Layout Consideration
Both the input capacitor and the output capacitor should be placed as close as possible to the IC. This can reduce the copper trace resistance which directly effects the input and output ripples. The feedback resistor network should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the feedback resistor network should connect directly to the GND pin or to an analog ground plane that is tied directly to the GND pin. The inductor and the schottky diode should be placed as close as possible to the switch pin to minimize the noise coupling to the other circuits, especially the feedback network.
Power Efficiency
VIN
2.7-4.2V
Murata LQH32CN100K11 L1 10uH 0.45A
DS
MBR0530
C1 4.7uF
C2 2.2uF
5 V 4
R1 150Kohm
U1 SP6691
IN
1 SW 3 D1
WLED MODULE
0.7V
DIODE
SHDN GND 2
FB
1.22V
Rb 34.8ohm
Figure 23. Improve Efficiency with Diode in Feedback Loop
For the typical application circuit, the output efficiency of the circuit is expressed by = VOUT * IOUT VIN * IIN
To further improve the efficiency and reduce the effects of the ambient temperature on the diode D1 used in method 1, an op amp circuit can be used as shown in Figure 24. The gain of the op amp circuit can be calculated by: Av = R1 + R 2 R1
Where VIN , IIN, VOUT, IOUT are the input and output voltage and current respectively. While the white LED efficiency is expressed by = (VOUT - 1.22) * IOUT VIN * IIN
If the voltage across the bias resistor is set to be 0.1V the current through R1 and R2 to be around 100A, R1 and R2 can be selected as 1K and 11.2K respectively. LMV341 can be used because of its small supply current, offset voltage and minimum supply voltage. By using this method, the efficiency can be increased around 7%.
Vbattery
This equation indicates that the white LED efficiency will be much smaller than the output efficiency of the circuit when VOUT is not very large, compared to the feedback voltage (1.22V). The other power is consumed by the bias resistor. To reduce this power loss, two circuits can be used, as shown in Figure 23 and Figure 24. In Figure 23, a general-purpose diode (for example, 1N4148) is used to bring the voltage across the bias resistor to be around 0.7V. R1 is used to create a loop that provides around 100A operating current for the diode. 3% efficiency improvement can be achieved by using this method.
Jun26-07 Rev D
2.7-4.2V
Murata LQH32CN100K11 L1 10uH 0.45A
DS
MBR0530
Vbattery
C1 4.7uF
5 V 4
U1 SP6691
IN
1 SW 3
C2 2.2uF 5
4
OUT
WLED MODULE
6
+ LMV341 1
0.1V
3
SHDN GND 2
FB
1.22V
R2
2
-
Rb 11.2K R1 1K 5.1
Figure 24. Improve Efficiency with Op Amp in Feedback Loop
(c) 2007 Sipex Corporation
Micro Power Boost Regulator Series White LED Driver
0
PACKAGE: PINOUTS
VIN SHDN
VIN
5
4
SHDN
5
4
SP6691
5 Pin SOT-23
SW
SP6691
5 Pin TSOT
3
SW
1
GND
2
FB
1
GND
2
FB
3
NC FB NC SW
1 2 3 4
8
NC SHDN VIN GND
SP6691
8 Pin DFN
7 6 5
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
Package: 8 Pin DFn
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
2
Package: 5 Pin SOT-23
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
Package: 5 Pin TSOT
Jun26-07 Rev D
Micro Power Boost Regulator Series White LED Driver
(c) 2007 Sipex Corporation
ORDERING INFORMATION
Part Number Temperature Range Package Type SP6691EK1 .......................................................... -40C to +85C ............................. 5 Pin TSOT SP6691EK1/TR ..................................................... -40C to +85C ............................ 5 Pin TSOT SP6691EK ............................................................ -40C to +85C .......................... 5 Pin SOT-23 SP6691EK/TR ....................................................... -40C to +85C ......................... 5 Pin SOT-23 SP6691ER ............................................................ -40C to +85C ............................... 8 Pin DFN SP6691ER/TR ...................................................... -40C to +85C .............................. 8 Pin DFN
Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6691ER/TR = standard; SP6691ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for TSOT or SOT-23 and 3,000 for DFN.
For further assistance: Email: WWW Support page: Sipex Application Notes: Sipexsupport@sipex.com http://www.sipex.com/content.aspx?p=support http://www.sipex.com/applicationNotes.aspx
Solved by
Sipex corporation
TM
Headquarters and Sales Office 2 South Hillview Drive Milpitas, CA 0 TEL: (0) -700 FAX: (0) -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. Jun26-07 Rev D Micro Power Boost Regulator Series White LED Driver (c) 2007 Sipex Corporation

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