ACE710C

1A Synchronous PWM Boost converter

VER 1.1

6

Detailed description

ACE710C is a low input voltage start up, current mode DC-

DC step up converter. It’s operation can be

best understood by referring to the block diagram. Upon starting up, the low voltage startup circuitry

drives SW with on-off cycles, transferring energy from input to OUT by storing energy in the inductor

during on-time and releasing it to the output during off-time. When OUT is high enough, the startup circuit

turns off and the main controller takes over. The main control loop consists of a reference, a GM error

amplifier, a PWM controller, a current sense amplifier, an oscillator, a PWM logic control, and it is power

stage including its driver. The main control loop is a classic current mode control loop. The GM stage

integrates the error between FB and REF, and its output is used to compare with a triangular wave which

the summing result of the current sense amplifier output and a slope compensation voltage. The output of

the comparator is used to drive the power stage to reach regulation.

APPLICATION INFORMATION

Inductor selection

With switching frequency up to 1MHz, small surface mount inductors can be used with values from

2.2uH to 4.7uH.For a given chosen inductor value and application conditions make sure the peak inductor

current does not exceed the maximum current rating of the selected vendor's inductor.

Input and output capacitor selection

The ACE710C's bootstrap architecture allows the use of very small input capacitor. For applications that

only need to drive small output load current, the input capacitor is optional, because once output is started

up, the IC's is powered by OUT, a quiet power supply.

The output capacitor is used to stabilize the loop and provide ac current to the load. A low ESR ceramic

cap with values from 2.2uF to 22uF can be used.

Smaller

value

capacitors

are

generally cheaper

with

small

footprints,

while

larger capacitor

provides

lower

ripples

and

better transient load

responses. Also, when extreme low startup voltage is needed, larger output capacitors are needed for the

part to startup under heavy load condition.