ACE527H

Low Noise, High PSRR LDORegulator

VER 1.3

6

Operation Principles

The ACE527H low dropout regulator (LDO) operates with a very low input voltage (>2.2V). The ACE527H

can operate at low input voltage due to low voltage circuit design techniques and a PMOS pass element

that exhibits low dropout. The dropout voltage is typically 420mV at 600mA output current.

Chip Enable

Typical quiescent current is only 65uA. A logic low on the enable input, CE, shuts down the output and

reduces the supply current to less than 1uA. The CE pin is internally pulled down by a 1uA current source

and may be tied to VIN in applications where the shutdown feature is not used.

Output Discharging Resistor

An internal

100Ω MOSFET is connected to VOUT pin and discharges the output voltage to ground when

the chip is disabled or thermal protection is triggered.

Soft Start

The ACE527H features adjustable soft start where SS pin is available. A 8uA current source charges the

soft start capacitor CSS and clamps output voltage ramping up speed. The soft start time is calculated as:

A 1nF yields 100ns soft start time. The soft start time is fixed as 100us where SS pin is not available

Output Voltage Programming

The output voltage of the ACE527H adjustable regulator is programmed using an external resistive

divider as shown in the typical application circuit. The output voltage is calculated as:

Where V

Resistors R1 and R2 should be chosen for approximately 10uA divider current. Lower value resistors can be

used but offer no inherent advantage and waste more power. Higher values should be avoided as leakage

currents at FB increase the output voltage error.