AME, Inc.

6

Rev.A.01

100mA Regulated Charg Pump

AME7730

The AME7730 uses charge pump voltage doubler struc-

ture to boost an input voltage to a regulated output volt-

age. Regulation is achieved by decting the charge pump

output voltage through an internal resistor divider network.

A charge pump circuit is enabled when the divided output

voltage below a preset trip point controlled by an internal

comparator.

n Detailed Description

n Short Circuit and Thermal

Protection

The AME7730 has a thermal protection and shutdown

circuit that continuously monitors the IC junction tem-

perature. If the thermal protection circuit senses the die

mal shutdown will disable the charge pump switching

system hysteresis before the charge pump can reset.

Once the over current event is removed from the output

charge pump will the become active again. The thermal

protection system will cycle on and off if an output short

circuit condition persists. This will allow the AME7730

to operate indefinitely a short circuit condition with out

damage to the device.

n Shutdown Mode

A control pin EN on the regulator can be used to place

the device into an energy-saving shutdown mode. In this

mode, the output is disconnected from the input as long

as V

quiescent current is reduced to 1

µA maximum.

n Capacitor Selection

For minimum output voltage ripple, the output capaci-

tor C

talum capacitors generally have a higher Effective Series

Resistance (ESR) and may contribute to higher output

voltage ripple. Leaded capacitors also increase ripple

due to the higher inductance of the package itself. To

achieve best operation with low input voltage and high

load current, the input and pump capacitors (C

respectively) should also be surface-mount ceramic types.

In all cases, X7R or X5R dielectric are recommended.

With ligh loads or higher input voltage, a smaller 0.1

µF

pump capacitor (C

capacitor (C

To

minimize output voltage ripple, increase the output ca-

pacitor C

n Efficiency

The efficiency of the charge pump regulator depends

on the applied input voltage, the load current, and the

internal operation mode of the device.

The approximate efficiency is given by:

Efficiency (%) = V

n Layout

Large ripple currents flow in the V

minimize both input and output ripple, keep the capaci-

tors as close as possible to the regulator using short,

direct circuit traces.

The trace lengths from the input and output capacitors

have been kept as short as possible. A star ground sys-

tem has been implemented, with GND pin as the center

of the star. No ground plane is provided in other layers as

this will provide capacitive coupling for noise spikes.