ACE705

High efficiency, Low supply current, step-up DC/DC Controller

VER 1.4

5

Typical Application

(1) Application with external NMOSFET

Vin

D 1N5817

Vout

L

27uH

EXT

OUT

Cin

ACE705

47uF

Cout

Rload

CE

GND

Cp

100uF Tan

OFF

ON

1nF

Figure 1

(2) Application with external NPN transistor

ACE705

Figure 2

be smaller. )

Detailed Description

The ACE705 series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up DC-DC

controller. Only four external components are necessary: an inductor, a schottky diode, an output filter

capacitor and a NMOSFET or a NPN transistor. The step-up DC-DC converter, constructed by ACE705,

can be adjusted from 2.5V to 6.0V, 0.1V step. By using the depletion technics, the quiescent current

drawn from power source is lower than 8uA. The high efficiency device consists of resistors for output

voltage detection and trimming, a start-up voltage circuit, an oscillator, a reference circuit, a PFM control

circuit, a switch protection circuit and a driver transistor.

ACE705 integrates PFM control system. This system controls fixed power switch on duty cycle

frequency to stabilize output voltage by calculating results of other blocks which sense input voltage,

output voltage, output current and load conditions. In PFM modulation system, the frequency and pulse

width is fixed. The duty cycle is adjusted by skipping pulses, so that switch on-time is changed based on

the conditions such as input voltage, output current and load. The oscillate block inside ACE705 provides

fixed frequency and pulse width wave.