AP2953AS8PR datasheet(4/9 Pages) CHIPOWN

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AP2953A

Chipown

8/F, ChuangYuan Building

No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718

http://www.chipown.com.cn

V2.0

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Functional Description

The AP2953A is a synchronous rectified, current-mode,

step-down regulator. It regulates input voltages from 4.75V

to 18V down to an output voltage as low as 0.925V, and

supplies up to 3A of load current.

The AP2953A uses current-mode control to regulate the

output voltage. The output voltage is measured at FB through

a resistive voltage divider and amplified through the internal

transconductance error amplifier. The voltage at the COMP

pin is compared to the switch current measured internally to

control the output voltage.

The converter uses internal N-Channel MOSFET switches to

step-down the input voltage to the regulated output voltage. Since

the high side MOSFET requires a gate voltage greater than the

input voltage, a boost capacitor connected between SW and BS is

needed to drive the high side gate. The boost capacitor is charged

from the internal 5V rail when SW is low.

When the AP2953A FB pin exceeds 20% of the nominal

regulation voltage of 0.925V, the over voltage comparator is

tripped and the COMP pin and the SS pin are discharged to GND,

forcing the high-side switch off.

Figure 3 –Functional Block Diagram

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