AP5100

1.2A STEP-DOWN CONVERTER with 1.4MHz SWITCHING

FREQUENCY

AP5100

Document number: DS32130 Rev. 3 - 2

3 of 12

www.diodes.com

April 2012

© Diodes Incorporated

Pin Descriptions

Pin Name

Pin #

Description

BST

1

Bootstrap. To form a boost circuit, a capacitor is connected between SW and BST pins to form a

floating supply across the power switch driver. This capacitor is needed to drive the power switch’s

gate above the supply voltage. Typical values for CBST range from 0.1µF to 1µF.

GND

2

Ground. This pin is the voltage reference for the regulated output voltage. All control circuits are

referenced to this pin. For this reason care must be taken in its layout.

FB

3

Feedback. To set the output voltage, connect this pin to the output resistor divider or directly to

VOUT. To prevent current limit run away during a current limit condition, the frequency foldback

comparator lowers the oscillator frequency when the FB voltage is below 400mV.

EN

4

On/Off Control Input. Do not leave this pin floating. To turn the device ON, pull EN above 1.2V and

to turn it off pull below 0.4V.

If enable/disable is not used, connect a 100k

Ω resistor between EN to VIN.

IN

5

Supply Voltage. The AP5100 operates from a +4.75V to +24V unregulated input. A decoupling

capacitor C1 is required to prevent large voltage spikes from appearing at the input. Place this

capacitor near the IC.

SW

6

Switch Output. This is the reference for the floating top gate driver.

Functional Block Diagram

Σ

Figure 5. Functional Block Diagram