ACE726C

500KHz, 18V, 2A Synchronous Step-Down Converter

VER 1.1

7

Detailed Description

Internal Regulator

The ACE726C is a current mode step down DC/DC converter that provides excellent transient response

with no extra external compensation components. This device contains an internal, low resistance, high

voltage power MOSFET, and operates at a high 500K operating frequency to ensure a compact, high

efficiency design with excellent AC and DC performance.

Error Amplifier

proportional to the difference between the two. This output current is then used to charge or discharge the

internal compensation network to form the COMP voltage, which is used to control the power MOSFET

current. The optimized internal compensation network minimizes the external component counts and

simplifies the control loop design.

Internal Soft-Start

The soft-start is important for many applications because it eliminates power-up initialization problems.

The controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing

start-up transient events to the input power bus.

Over-Current-Protection and Hiccup

The ACE726C has a cycle-by-cycle over-current limit for when the inductor current peak value exceeds

the set current-limit threshold. First, when the output voltage drops until FB falls below the Under-Voltage

(UV) threshold (typically 140mV) to trigger a UV event, the ACE726C enters hiccup mode to periodically

restart the part. This protection mode is especially useful when the output is dead-shorted to ground. This

greatly reduces the average short-circuit current to alleviate thermal issues and to protect the regulator. The

ACE726C exits hiccup mode once the overcurrent condition is removed.

Startup and Shutdown

IfbothVIN andEN arehigherthantheir appropriate thresholds, the chip starts. The reference block

starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The

regulator provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low,

VIN low and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any

fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is

not subject to this shutdown command.