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SP4446
High Output Voltage Boost Regulator LCD Bias Regulator
VIN SHDN
FEATURES High Output Voltage: Up to 30V High Efficiency Low Quiescent Current: ~20uA Single Battery Cell Operation Programmable Output Voltage 1 Switch (150mV at 150mA) Lead Free, RoHS Compliant Package: 5 Pin SOT-23
5
4
SP4446
5 Pin SOT-23 1
SW
2
GND
3
FB
APPLICATIONS LCD Bias Tuner Pin Voltage White LED Driver High Voltage Bias Digital Cameras Cell Phone Battery Backup Handheld Computers DESCRIPTION
The SP4446 is a micro power Boost Regulator in a 5-lead SOT-23 package. It is a current limited, fixed off-time regulator configured for use in boost mode applications. The operating voltage can be less than 3Volts and is capable of generating voltages as high as 30Volts. The SP4446 is available in a Lead Free, RoHS compliant package and permits the construction of complete regulators that occupy < 0.2 square inches of board space. TYPICAL APPLICATION SCHEMATIC
VIN 2 to 7V VIN
L1 10H SW SP4446 SHDN GND C1 FB
D1
High Voltage Output
R1
C2 2.2 F
4.7F
R2
Mar28-08
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
(c) 2008 Exar Corporation
1
ABSOLUTE MAXIMUM RATINGS
VIN ....................................................................... 15V SW Voltage .............................................. -0.4 to 34V FB Voltage .......................................................... 2.5V All other pins .................................. -0.3 to VCC + 0.3V Current into FB ................................................. 1mA TJ Max ............................................................. 125C Operating Temperature Range ............ -40C to 85C Peak Output Current < 10us SW .................... 500mA Storage Temperature ...................... -65C to +150C Power Dissipation. ......................................... 200mW Lead Temperature (Soldering, 10 sec) ............ 300C 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
Specifications are at VIN = 3.3V, VSHDN = VIN, TA = 25C, denotes the specifications which apply over the full operating temperature range, unless otherwise specified. PARAMETER Input voltage Supply Current SYMBOL MIN VIN IQ 1.0 20 0.01 Reference Voltage FB Hysteresis VFB Input Bias Current Line Regulation Switch Off Time VFB HYST IFB Vo/VI TOFF 1.17 1.22 8 15 0.04 300 1200 Switch Saturation Voltage VCESAT 50 150 Switch Current Limit SHDN Bias Current SHDN High Threshold (on) SHDN Low Threshold (off) Switch Leakage Current ILIM ISHDN VIH VIL ISWLK 2 0.9 0.25 5 100 150 5 200 12 80 TYP MAX UNITS 8.0 30 1 1.27 V A A V mV nA %/V nS nS mV mV mA A V V A Switch Off, VSW = 5V VSHDN = 5V VFB = 1.22V 1.2 VIN 8V VFB > 1V VFB < 0.3V ISW = 50mA ISW = 150mA CONDITIONS Switch Current Limit = 150mA No Switching SHDN = 0.0V
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.
(c) 2008 Exar Corporation
Mar28-08
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
2
FUNCTIONAL DIAGRAM
L1 VI C1 (EXTERNAL) R1 R5 R6 X1 + Q1 3 FB (EXTERNAL) R2 R3 CLEAR X2 Q2 DISABLE SET 300ns ONE-SHOT DRIVER + R4 52.5mV 0.35 5 VIN SW 1
D1 C2
VOUT
POWER TRANSISTOR
SHDN
4
Shutdown Logic
GND 2
THEORY OF OPERATION
General Overview:
Operation can be best understood by referring to the above block diagram. 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 150mA, comparator X2 clears the latch, which turns off the driver transistor for a preset 0.3s. At the instant of shutoff, inductor current is diverted to the output through diode D1. During this 0.3s time limit, inductor current decreases while its energy charges C2.
Mar28-08
At the end of the 0.3s time period, the driver transistor is again allowed to turn on which ramps the current back up to the 150mA level. Comparator X2 clears the latch, its output turns off the driver transistor, and this allows delivery of inductor 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. The SP4446 contains circuitry to provide protection during startup and while in short-circuit conditions. When FB pin voltage is less than approximately 300mV, the switch off time is increased to about 1.2s and the current limit is reduced to about 70% of its normal value. While in this mode, the average inductor current is reduced and helps minimize power dissipation in the SP4446, the external inductor and diode.
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
(c) 2008 Exar Corporation
3
APPLICATION INFORMATION
Inductor Selection
For SP4446, the internal switch will be turned off only after the inductor current reaches the typical DC current limit (ILIM=150mA). However, there is typically a 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: V IPK = ILIM + IN(MAX) * 200nS L 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 SP4446 peak current to avoid saturating the inductor, which would result in a loss of 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.
MANUF. PART NUMBER DCR () 0.44 0.71 Current Rating (mA) 300 250
inherently low ESR, which will help produce low peak to peak output ripple, and reduce high frequency spikes. For the typical application, a 4.7F input capacitor and a 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 SP4446 as possible for layout. For use as a voltage source, to reduce the output ripple, a small feedforward capacitor (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.
MANUF. MURATA 770-436-1300 MURATA 770-436-1300 TDK 847-803-6100 TDK 847-803-6100 PART NUMBER GRM32RR71E 225KC01B GRM31CR61A 475KA01B C3225X7R1E 225M C3216X5R1A 475K CAP/ VOLTAGE 2.2F/25V 4.7F/10V 2.2F/25V 4.7F/10V SIZE/ TYPE 1210/X5R 1206/X5R 1206/X7R 1206/X5R
Table 2. Suggested Low ESR Capacitor
MURATA 770-436-1300 MURATA 770-436-1300 TDK 847-803-6100 TDK 847-803-6100
LQH32CN100K21 (10H) LQH32CN220K21 (22H)
Output Voltage Program
NLFC453232T-100K (10H) 0.273 NLC453232T-100K (22H) 0.9
250 370
In order for the SP4446 to be programmed as a voltage source, the SP4446 requires 2 feedback resistors R1 & R2 to control the output voltage, as shown in Figure 1.
VIN D1
Table 1. Suggested Low ESR inductors
L1
Diode Selection
VOUT
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.
Capacitor Selection
C2 C1 U1
5 VI N 4 1 SW
R1
SP4446
SHDN G ND FB
3
1.22V
R2
2
Ceramic capacitors are recommended for their
Figure 1. Using SP4446 as Voltage Source
Mar28-08 SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator (c) 2008 Exar Corporation
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APPLICATION INFORMATION: Continued The formula and table for the resistor selection are shown below: VOUT 1.22 - 1 ) * R2 Two Resistors (R1=1M, R2=42.2K) are used to program the output voltage to be 30V. When input voltage is 3.3V or 5V, it can supply a maximum current of 3mA and 5mA to the load.
Load Disconnect in Shutdown
R1 =(
VOUT (V) 12 15 18 20 30
R1 () 1M 1M 1M 1M 1M
R2 () 113K 88.7K 73.2K 64.9K 42.2K
VIN
When SP4446 is shut down, the load is still connected to the input. In applications that require output isolation during shutdown, an external PNP transistor (for example MMBT2907A) can be added as shown in Figure 3.
R3 154K
L1 10uH C1 4.7uF U1
5 VIN 4
DS
Q1 MMBT2907A R1 1M C2 47pF
VOUT 20V
C3 2.2uF
1 SW 3
Table 3. Divider Resistor Selection
SHDN_N
SP4446
SHDN GND FB
1.22V
R2 64.9K
Layout Considerations
2
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 ripple. 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.
PIN Diode Driver
Fig. 3. Load Disconnect in Shutdown
When the SP4446 is active, the voltage set at the emitter of the transistor exceeds the input voltage, forcing the transistor into the saturation region. When the SP4446 is shut down, the input voltage exceeds the emitter voltage, thus the transistor becomes inactive and provides highimpedance isolation between the input and load. Efficiency will be slightly sacrificed because of the saturation voltage and base current of the PNP transistor.
The SP4446 can be used as PIN diode driver as shown in Figure. 2.
Murata LQH32CN100K21
VIN 3.3V or 5V
L1 10uH 0.3A
DS
30V VOUT
MBR0530 C2 47pF R1 1M
1 SW
3 to 5 mA
C1 4.7uF
U1
5 VIN 4
C3 2.2uF
FB 3
SP4446
SHDN GND 2
1.22V R2 42.2K
Fig. 2. Pin Diode Driver
Aug15-07 SP4446 High Output Voltage Boost Regualtor, LCD Bias Regulator (c) 2007 Sipex Corporation
5
PERFORMANCE CHARACTERISTICS
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
Vin=3.3V;Vout =12V Efficiency
85
85
Vin=5.0V;Vout =12V Efficiency
80
80
75
75
70
Efficiency (%)
70
Efficiency (%)
65
65
60
60
55
10 uH 22 uH
55
10 uH 22 uH
50 0 3 6 9 Iout (mA) 12 15 18
50 0 5 10 15 20 25 30
Iout (mA)
Figure 4. 12V Output Efficiency (VIN=3.3V)
Figure 5. 12V Output Efficiency (VIN=5V)
Vin=3.3V;Vout =15V Efficiency
80 80
Vin=5.0V;Vout =15V Efficiency
75
75
70
70
Efficiency (%)
65
Efficiency (%)
65
60
60
55
10 uH 22 uH
55
10 uH 22 uH
50 0 2 4 6 Iout (mA) 8 10 12
50 0 3 6 9 Iout (mA) 12 15 18
Figure 6. 15V Output Efficiency (VIN=3.3V)
Vin=3.3V; Vout = 18V Efficiency
80 75 70
Figure 7. 15V Output Efficiency (VIN=5V)
Vin=5.0V; Vout = 18V Efficiency
80 75 70 65
Efficiency (%)
60
Efficiency (%)
65
60 55 50
55 50
10 uH
45 40 0.0 1.0 2.0 3.0 4.0 Iout (mA) 5.0 6.0 7.0 8.0
10 uH
45
22 uH
22 uH
40 0.0 2.0 4.0 6.0 8.0 Iout (mA) 10.0 12.0 14.0
Figure 8. 18V Output Efficiency (VIN=3.3V)
Mar28-08
Figure 9. 18V Output Efficiency (VIN=5V)
(c) 2008 Exar Corporation
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
6
PERFORMANCE CHARACTERISTICS
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
Vin=3.3V;Vout = 20V Efficiency
75 70 65
65 75
Vin=5V;Vout = 20V Efficiency
70
60
Efficiency (%)
55 50 45 40
Efficiency (%)
60
55
50
45
10 uH
35 30 0 1 2 3 4 5 6 7 Iout (mA)
40
10 uH 22 uH
22 uH
35 0 2 4 6 Iout (mA) 8
10
12
Figure 10. 20V Output Efficiency (VIN=3.3V)
12
10uH
Figure 11. 20V Output Efficiency (VIN=5V)
6 10uH 5 22uH
Maximum Output Current (mA)
10
22uH
Maximum Output Current (mA)
8
4
6
3
4
2
2
1
0 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1
0 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1
Input Voltage (V)
Input Voltage (V)
Figure 12. Maximum Output Current vs. V IN (V OUT=20V)
30
Figure 13. Maximum Output Current vs. VIN (VOUT=30V)
10
25
8
Quiescent Current (uA)
20
Shutdown Pin Current (uA)
Tamb=-40C Tamb=25C Tamb=85C
6
15
4
10
2
5
0 1 2 3 4 5 6 7 8
0 1 2 3 4 5 6 7 8
Input Voltage (V)
Input Voltage (V)
Figure 14. Quiescent Current IQ vs. VIN
Mar28-08
Figure 15. Shutdown Pin Current vs. VIN
(c) 2008 Exar Corporation
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
7
PERFORMANCE CHARACTERISTICS
Refer to the typical application circuit, TAMB = 25C, unless otherwise specified.
250
1.25
1.24
200
1.23
Ipk Current Limit (mA)
150
Feedback Voltage (V)
1.22
100
1.21
1.20
50
1.19
0 1 2 3 4 5 6 7 8
1.18 -40
-15
10
35
60
85
Input Voltage (V)
Temperature (C)
Figure 16. IPK Current Limit vs. VIN
60
Figure 17. Feedback Voltage vs. Temperature
50
Switch Saturation Voltage (mV)
40
VIN
30
20
VOUT
10
0 -40
IIN (100mA/DIV)
-15 10 35 60 85
Temperature (C)
Figure 18. Switch Saturation Voltage VCESAT vs. Temperature (ISW=50mA)
Figure 19. Startup Waveform (VIN=3.3V, VOUT=20V, IOUT=2mA)
VSW
IOUT (5mA/DIV)
VOUT (AC)
IL (0.1A/DIV)
VOUT (AC)
VSW
Figure 20. Typical Switching Waveforms (VIN=3.3V, VOUT=20V, IOUT=5mA)
Mar28-08
Figure 21. Load Step Transient (VIN=3.3V, VOUT=20V, 1O=100A5mA)
(c) 2008 Exar Corporation
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
8
PACKAGE: 5 PIN SOT-23
Mar28-08
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
(c) 2008 Exar Corporation
9
ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP4446EK-L .................................................. -40C to +85C ...................................Lead Free 5 Pin SOT-23 SP4446EK-L/TR ............................................ -40C to +85C ...................................Lead Free 5 Pin SOT-23 -G: "Green"/Halogen free package. Substitute "-L" by "-G" in the ordering part number. /TR = Tape and Reel Pack quantity is 2,500 for SOT-23.
Exar Corporation Headquarters and Sales Office 248720 Kato Rd,33 South Hillview Drive M Fremont, CA 94538 TEL: (510) 668-7000 FAX: (510) 668-7001
Exar 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.
Mar28-08
SP4446 High Output Voltage Boost Regulator, LCD Bias Regulator
(c) 2008 Exar Corporation
10

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