ACE712E

5V/2A Output, 1MHz Synchronous Step-Up Converter with DCP emulator

VER 1.1

6

APPLICATION INFORMATION

Loop Operation

The ACE712E is a wide input range, high-efficiency, DC/DC step up switching regulator, integrated with a

70mΩ Low Side Main MOSFET and 40mΩ synchronous 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.

The output voltage is fixed to be 5V by internal resistor as an available USB host ports power source. The

peak current of the NMOS switch is also sensed to limit the maximum current flowing through the switch

and the inductor. The typical peak current limit is set to 5A. An internal temperature sensor prevents the

device from getting overheated in case of excessive power dissipation.

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. ACE712E employs a proprietary control scheme that improves

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

extending the range of high efficiency operation.

Short-Circuit Protection

Unlike most step-up converters, the ACE712E allows for short circuits on the output. In the event of a

short circuit, the device first turns off the NMOS when

the sensed current reaches the current limit. After

VOUT drops

below VIN the device then enters a linear charge period with the current limited same as

with the start-up period. In addition, the thermal shutdown circuits disable switching if the die temperature

rises above 150°C.

The ACE712E will continue to supply the output voltage even when the input voltage exceeds the output

voltage. Since the PMOS no longer acts as a low-impedance switch in this mode, power dissipation

increases

within the IC to cause a sharp drop in efficiency. Limit the maximum output current to maintain

an acceptable junction temperature.

USB Dedicated Charging Port (DCP) Emulator

The D+/D- is a dedicated charging port emulator, used for the charging of most popular mobile phones

and tablet PCs. An auto-detect feature monitors USB data line voltage, and automatically provides the

correct electrical signatures on the data lines (D+ and D-) to charge compliant

devices.

A DCP only

provides

power

and does not provide data connection to an upstream port. A DCP is identified by the

electrical characteristics of its data line. It integrate an auto-detect feature to support divider mode and

Samsung mode.