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AMS4155

PIN DESCRIPTION

Pin Number

NAME

DESCRIPTION

1

SYNC

Synchronization Input. This pin is used to synchronize the internal oscillator frequency to

an external source. Leave SYNC unconnected or connect to GND if unused.

2

BST

Bootstrap. This capacitor is needed to drive the power switch above the supply voltage. It

is connected between LX and BST pins to form a floating supply across the power switch

driver. The voltage across Cbst is about 5V and is supplied by the internal Vcc supply

when LX pin voltage is low.

3

VIN

Supply Voltage. The AMS4155 operates from a+4.75V to +23V unregulated input. Cin is

needed to prevent large voltage spikes from appearing at the input power supply.

4

LX

This connects the inductor to the internal Switch

5

GND

Ground Pin connected to PCB ground plane. This pin is also the ground for internal voltage

reference.

6

FB

Feedback. A resistor network of two resistors is used to set-up the output voltage connected

between Output to GND. The node between the two resistors is connected to Feedback pin.

7

COMP

Compensation. This node is the output of the transconductance error amplifier and the

input to the current comparator. Frequency compensation is done at this node by

connecting a series R-C to ground.

8

ENABLE

Enable. A voltage greater than 2.495V at this pin enables device operation.