EC49121

600mA LDO with Fast Enable

And Fast Discharge Function

Page 9 of 13

Detail Description

The EC49121 is a low-dropout linear regulator. The device provides preset 1.8V, 2.5V and 3.3V output

voltages for output current up to 600mA. Adjustable output voltage and other mask options for special output

voltages are also available. As illustrated in function block diagram, it consists of a 1.175V band gap (Fixed voltage

type is 0.95V) reference, an error amplifier, a P-channel pass transistor and an internal feedback voltage divider.

The band gap reference for fixed voltage types is connected to the error amplifier, which compares this

reference with the feedback voltage and amplifies the voltage difference. If the feedback voltage is lower than the

reference voltage, the pass-transistor gate is pulled lower, which allows more current to pass to the output pin and

increases the output voltage. If the feedback voltage is too high, the pass transistor gate is pulled up to decrease

the output voltage.

The output voltage is feed back through an internal resistive divider (or external resistive divider for

adjustable output voltage type) connected to OUT pin. Additional blocks include an output current limiter, thermal

sensor, and shutdown logic.

Internal P-Channel Pass Transistor

The EC49121 features a P-channel MOSFET pass transistor. Unlike similar designs using PNP pass

transistors, P-channel MOSFET require no base drive, which reduces quiescent current. PNP based regulators

also waste considerable current in dropout when the pass transistor saturates, and use high base-drive currents

under large loads. The EC49121 does not suffer from these problems and consumes only 60μA (Typ.) of current

consumption under heavy loads as well as in dropout conditions.

Enable Function

EN pin starts and stops the regulator. When the EN pin is switched to the power off level, the operation of all

Fast Discharge Function

The EC49121 fixed type has fast discharge Function on EN pin disable. When user turns off the device, its

internal pull low resistor will discharge output capacitor charge. It’ll avoid other device to arise wrong motions.

Simplified Application Circuit