ACE732E

6V/3.5A, Fast Response, Step-Down Converter

VER 1.2

6

FUNCTIONAL DECRIPTIONS

ACE732E belongs to a new breed of high frequency synchronous Step-Down converter that combines the

advantages of voltage mode control and Constant On time control. Its adaptive Constant-On-Time control

dynamically changes switch on time to achieve a constant switching frequency. It does not have the

minimum on-time constrain normally a fixed-frequency current

mode Step-down requires, allowing it to go

down to very low duty ratios without affecting loop stability. The voltage mode nature of ACE732E also

provides a more superior load transient response as well as a seamless transition from PFM to PWM modes.

It can also operate up to 100% duty. It has a cycle by cycle current limit and a hiccup mode that protects

against dead-short condition. It includes soft-start, UVLO and thermal shutdown protection.

Adaptive Constant On-Time Control

ACE732E uses an adaptive Constant-On-Time control scheme that the ON time is dynamically adjusted

according to VIN and VOUT so to achieve a nearly constant switching frequency.

This control scheme

provides simpler compensation and superior transient response over traditional constant frequency current

mode control, while still maintaining the advantage of switching at a constant frequency at about 1.5MHz. It

also provides a seamless transition from PFM to PWM that normally a constant frequency current mode

control scheme is hard to achieve. Further mode, because it is a COT control scheme, the system can

achieve high step-down ratio at ease, because lower constrain on the minimum on- time requirement

existing in constant frequency scheme.

100% Duty operation

ACE732E can operate at 100% duty cycle under dropout condition for high efficiency purpose.

Current Limit and Short-Circuit protection

ACE732E employs a cycle-by-cycle peak current limit and it also has a hiccup mode that protects the circuit

during dead-short condition. When the dead-short condition is removed, the IC goes back to normal

operation.

Soft-start

ACE732E has an internal soft-start circuitry to reduce supply inrush current during startup conditions.

When the device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a