ACE736E

42V Input Standoff Voltage, 0.4A Step-Down Converter

VER 1.1

4

Electrical Characteristics

Parameter

Conditions

Min

Typ

Max

Unit

Input Standoff Voltage

42

V

Input Voltage Range

4

38

V

Input UVLO

Rising, Hysteresis=140mV

3.80

V

Input OVP

Rising, Hysteresis=1.3V

38

V

Input Supply Current

0.6

mA

Input Shutdown Current

6

μA

FB Feedback Voltage

0.78

0.80

0.82

V

FB Input Current

0.01

μA

Switching Frequency

75

KHz

Maximum Duty Cycle

90

%

Fold-Back Frequency

95

KHz

High side Switch On Resistance

550

mΩ

High side Switch Current Limit

0.7

A

SW Leakage Current

10

μA

EN Input Current

1

5

μA

EN Input Low Voltage

Rising, Hysteresis=100mV

0.8

1.1

1.4

V

Thermal Shutdown

Hysteresis=40℃

150

℃

Functional Descriptions

Loop Operation

The ACE736E is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of

delivering up to 0.4A of output current, integrated with a 550mΩ high side MOSFET. It uses a PWM

current-mode control scheme. An error amplifier integrates error between the FB signal and the internal

reference voltage. The output of the integrator is then compared to the sum of a current-sense signal and

the slope compensation ramp. This operation generates a PWM signal that modulates the duty cycle of

the power MOSFETs to achieve regulation for output voltage.

Light Load Operation

Traditionally, a fixed constant frequency PWM DC-DC regulator always switches even when the output

load is small. When energy is shuffling back and forth through the power MOSFETs, power is lost due to

the finite RDSONs of the MOSFETs and parasitic capacitances. At light load, this loss is prominent and

efficiency is therefore very low. ACE735E employs a proprietary control scheme that improves efficiency

in this situation by enabling the device into a power save mode during light load,thereby extending the

range of high efficiency operation.