PS0021 Datasheet, PDF (10/12 Pages) Power IC Ltd. – High Efficiency PFM Step-up DC/DC Converter

PS0021
Under Voltage Lockout
When the supply becomes too low (typically below 1.8V),
the PS0021 produces an internal UVLO (Under Voltage
Lockout) signal that disables the normal PWM operation
and enables the start-up oscillator to run at a fixed
frequency. At this stage, very few circuits are operational.
When the oscillator raises the supply to above 1.9V, the
UVLO signal is disabled and the normal PWM mode takes
over the operation of the start-up oscillator. This
mechanism protects the chip from producing false logic
due to low input supply.
Enable Input
The PS0021 features an active-high CMOS input enable
pin (SHUTB) that allows on/off control of the regulator.
When SHUTB=Low, shutdown of the chip occurs and at
that time almost no quiescent current (<1µA) flows. The
output capacitor can be completely discharged through
the load or the feedback resistors for real output shut-
down. A discharge switch is internally connected between
VIN and SW. The Enable (SHUTB) input is TTL/CMOS
compatible. Connect SHUTB to VIN for normal operation.
Track Mode
In track mode Vout follows Vin. Difference between Vout
and Vin is determined by the load current and the
schottky forward voltage drop at that current.
July 2007
www.picsemi.com
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