ACE727Z

18V, 3A, High Efficiency Synchronous Step-Down Converter

VER 1.1

6

Functional Description

The ACE727Z is a synchronous buck regulator ICs that integrates the PWM control, top and bottom

switches on the same die to minimize the switching transition loss and conduction l

The ACE727Z is a wide input range, high efficiency, DC-to-DC step-down switching regulator, capable of

delivering up to 3A of output current, integrated with a 155mΩ high side and 88mΩ low side MOSFET. It

uses 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 MOSFET 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 MOSFET, power is lost due to

the finite Rdson of the MOSFET and parasitic capacitances. At light load, this loss is prominent and

efficiency is therefore very low. ACE727Z employs a proprietary control scheme that improves efficiency

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

range of high efficiency operation.

Enable

EN is a digital control pin that turns the ACE727Z on and off. Drive EN High to turn on the regulator, drive

it Low to turn it off. An internal 1MΩ resistor from EN pin to GND allows EN to float to shut down the chip.

Connecting the EN pin through a pull up resistor or shorted EN to IN will automatically turn on the chip

whenever plug in IN.

Over Current Protection and Hiccup

ACE727Zhas a cycle-by-cycle over current limit for when the inductor current peak value is over the set

current limit threshold. When the output voltage drop until FB falls below UV threshold (0.2V), the

ACE727Z will enter hiccup mode. It will turn off the chip immediately for 6mS. After that, it will try to

re-starts as normal for 2mS. After 2mS, if FB is still below UV threshold, then the chip enters hiccup mode

again. If FB is higher than UV threshold, it will enter the normal mode.

Over-Temperature Protection

Thermal protection disables the output when the junction temperature rises to approximately 150°C,

allowing the device to cool down. When the junction temperature cools to approximately 110°C, the output

circuitry is again enabled. Depending on power dissipation, thermal resistance, and ambient temperature,

the thermal protection circuit may cycle on and off. This cycling limits regulator dissipation, protecting the

device from damage as a result of overheating.