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AAT3110

MicroPower™ Regulated Charge Pump

Analog Technology Inc 

AAT3110

MicroPower™ Regulated Charge Pump

Applications Information

and low frequency components of the charge pump

output ripple response. If a higher value tantalum

capacitor is used for COUT to reduce low frequency

ripple elements, a small 1µF low ESR ceramic

capacitor should be added in parallel to the tantalum

capacitor (see Figure 1). The reason for this is tan-

talum capacitors typically have higher ESR than

equivalent value ceramic capacitors and are less

able to reduce high frequency components of the

output ripple. The only disadvantage to using large

values for the COUT capacitor is the AAT3110 device

turn-on time and in-rush current may be increased.

If additional ripple reduction is desired, an R/C filter

can be added to the charge pump output in addi-

tion to the COUT capacitor (see Figure 2). An R/C

filter will reduce output ripple by primarily attenuat-

ing high frequency components of the output ripple

waveform. The low frequency break point for the

R/C filter will significantly depend on the capacitor

value selected.

Layout Considerations

High charge pump switching frequencies and large

peak transient currents mandate careful printed cir-

cuit board layout. As a general rule for charge

pump boost converters, all external capacitors

should be located as close as possible to the

device package with minimum length trace con-

nections. Maximize the ground plane around the

AAT3110 charge pump and make sure all external

capacitors are connected to the immediate ground

plane. A local component side ground plane is rec-

ommended. If this is not possible due the layout

design limitations, assure good ground connec-

tions by the use of large or multiple pcb via's.

Refer to the following AAT3110 evaluation board for

an example of good charge pump layout design

(Figures 3 through 5).

VOUT

(5V)

COUT2

1µF

COUT1

+

22µF

VOUT

C+

AAT3110

GND

VIN

ON/OFF

SHDN C-

Figure 1: Application using tantalum capacitor

VOUT

(5V)

CFILTER

33µF

RFILTER

1.5 ohms

COUT

10µF

VOUT

C+

AAT3110

GND

VIN

ON/OFF

SHDN C-

Figure 2: Application with output ripple reduction filter

CFLY

1µF

+ CIN

10µF

VIN

(2.7V to 5V)

CFLY

1µF

VIN

CIN (2.7V to 5V)

10µF

14

3110.2001.9.0.92

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