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Part: SP4446
Category:
Power Management
-> Regulators
-> Boost Regulators
Description: Iout = 75mA ;; Vin Min. = 1V ;; Vin Max. = 8V ;; Fixed Outputs = N/a ;; Output Range = up to 30V ;; Iq = 20µA ;; Efficiency = 75% ;; Package = 5 Pin SOT-23
Company: Sipex Corporation
Datasheet: Download SP4446 datasheet File size : 77 kB
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Datasheet text preview:
®
PRELIMINARY
SP4446
High Output Voltage Boost Regulator LCD Bias Regulator
FEATURES High Output Voltage: Up to 30V High Efficiency Low Quiescent Current: ~20uA Miniature Package: (5-lead SOT-23) Single Battery Cell Operation Programmable Output Voltage 1 Switch (150mV at 150mA) 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 Regualtor 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 3V and is capable of generating voltages as high as 30 Volts. The SP4446 is to be supplied in a SOT-23-5 and permits the construction of complete regulators that occupy < 0.2 square inches of board space. TYPICAL APPLICATION SCHEMATIC
VIN 2 to 7V VIN SP4446 SHDN GND C1 4.7µF R2 FB 2.2 µF L1 10µH SW R1 C2 D1 High Voltage Output
VIN SHDN
5
4
SP4446
5 Pin SOT-23 1
SW
2
GND
3
FB
Rev. 7/14/03
SP4446 High Output Voltage Boost Regualtor, LCD Bias Regulator
© Copyright 2003 Sipex 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 .... 125°C Operating Temperature Range ... -40°C to 85°C Peak Output Current < 10us SW ........... 500mA Storage Temperature .... -65°C to +150°C Power Dissipation. ........ 200mW Lead Temperature (Soldering, 10 sec) ... 300°C 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 = 25°C, denotes the specifications which apply over the full operating temperature range, unless otherwise specified. PARAMETER Input voltage Supply Current SYMBOL MIN V IN IQ 1.0 20 0.01 Reference Voltage FB Hysteresis VFB Input Bias Current Line Regulation Switch Off Time VFB HYST IFB Vo/VI T OFF 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 V IH VIL ISWLK 2 0.9 0.25 5 100 150 5 200 12 100 80 TYP MAX UNITS 8.0 30 1 1.27 V µA µA V mV nA %/V nS nS mV mV mA µA V V µA 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 = 0V
PIN DESCRIPTION
PIN NUMBER 1 2 3 4 5 PIN NAME SW GND FB SHDN VI N 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.
© Copyright 2003 Sipex Corporation
Rev. 7/14/03
SP4446 High Output Voltage Boost Regualtor, 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 0.3µs. At the instant of shutoff, inductor current is diverted to the output through diode D1. During this 0.3µs time limit, inductor current decreases while its energy charges C2.
Rev. 7/14/03
At the end of the 0.3µs time period, driver transistor is again allowed to turn on which ramps the current back up to the 150mA 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. The SP4446 contains circuitry to provide protection during start-up and while in short-circuit conditions. When FB pin voltage is less than approximately 300mV, the switch off time is increased to about 1.2µs 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 Regualtor, LCD Bias Regulator
© Copyright 2003 Sipex Corporation
3
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