SIP12502DMP-20-E3 Просмотр технического описания (PDF) - Vishay Semiconductors
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SIP12502DMP-20-E3 Datasheet PDF : 11 Pages
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Product is End of Life 3/2014
FUNCTIONAL BLOCK DIAGRAM
SiP12502
Vishay Siliconix
DETAILED OPERATION
SiP12502 is a 300 kHz boost converter IC, packaged in 6-pin
MLP33 PowerPAKTM package. With start-up from input
voltages as low as 0.65 V, this device features fixed
frequency voltage mode PWM control with internal frequency
compensation. With its low rDS(on) internal power MOSFET,
this device maintains high efficiency over a wide range of
load currents. Under light load conditions, it switches to PFM
mode to maintain high efficiency. A power good signal is
available to monitor the output voltage.
Low Voltage Start-Up
SiP12502 is designed to start-up at input voltage of typically
0.65 V. At start-up, VOUT is lower than VIN due to the voltage
drop of the Schottky diode. Therefore, the device uses VIN as
the power source for its control logic and internal gate drive,
until VOUT exceeds VIN. During the start-up interval, the
boost switch’s conduction interval during each cycle is
determined by the time taken for the inductor current to reach
internal current limit, followed by a fixed off time before the
switch is allowed to turn on again. Once VOUT exceeds VIN,
the device uses VOUT as the IC’s power source. When VOUT
exceeds 1.89 V, the device engages its built-in soft-start
circuitry.
Soft-Start
During soft-start, the loop compensation guarantees the slow
increase of output voltage, so that no large voltage overshoot
or inrush current transients occur when the soft-start period
ends.
PWM operation
After the soft-start interval is over, the device works in PWM
operation with a fixed frequency of 300 kHz, with automatic
switch-over to PFM operation during light load conditions.
PFM Operation
When operating into light loads, the SiP12502 automatically
switches to PFM operation. This reduces gate charge losses
in the boost switch, hence raising converter efficiency.
Over Voltage Protection
If the output voltage is above 10 % of the regulation voltage,
the device will turn off the internal power MOSFET and wait
until the output voltage falls below the regulation voltage,
then the PWM operation is enabled again.
Thermal Shutdown Protection
If the internal device temperature rises above 160 °C, the
device will turn off the internal power MOSFET. Once the die
temperature falls below 140 °C, the device performs a new
soft-start cycle, the converter resumes normal operation.
Antiringing Control
The antiringing control circuitry prevents high frequency
ringing at the LX pin as the inductor current goes to zero by
damping the resonant circuit formed by L and CLX
(capacitance on LX pin). When the IC is shutdown, this
antiringing switch is also turned on.
Document Number: 73578
S09-1456-Rev. B, 03-Aug-09
www.vishay.com
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