OPERATION

PL0501

The

quiescent current linear regulator designed for space-

restricted applications. It is available with preset output

voltages ranging from 1.5V to 5.0V in 100mV increments.

It can supply loads of up to 500mA. As shown in the

Block Diagram, the

band gap core, noise bypass circuit, error amplifier, P-

channel pass transistor and an internal feedback voltage

divider. The

an external feedback network. The 1.0V band gap

reference is connected to the error amplifier’s inverting

input. The error amplifier compares this reference with

the feedback voltage and amplifies the difference. If the

feedback voltage is lower than the reference voltage, the

pass transistor gate is pulled low. This allows more

current to pass to the output and increases the output

voltage. If the feedback voltage is too high, the pass

transistor gate is pulled high, allowing less current to

pass to the output. The output voltage is fed back

through an internal resistor voltage-divider connected to

the OUT pin. An external bypass capacitor connected to

BYP (

Additional blocks include a current limiter, over

temperature protection and shutdown logic.

Internal P-Channel Pass Transistor

The

pass transistor. This provides several advantages over

similar designs using a PNP pass transistor, including

longer battery life. The P-channel MOSFET requires no

base drive, which considerably reduces the quiescent

current. PNP-based regulators waste considerable current

in dropout when the pass transistor saturates. They also

use high base-drive current under heavy loads.

July 2007

www.picsemi.com

© 2007 Power IC. All Rights Reserved.

7

The

consumes only 90

μA of quiescent current.

Output Voltage Selection

The

from 1.5V to 5.0V, in 100mV increments. The

PL0501

features a user-adjustable output through an external

feedback network (see Typical Application).

To set the output of the

equation:

Where

R2 is chosen to be less than 240K

Ω

resistors.

Current Limit

The

output current and controls the pass transistor’s gate

voltage to limit the output current under 1500mA

(typical). The output can be shorted to ground for an

indefinite amount of time without damaging the part.

The short circuit current limit is increased to

approximately 1500mA (typical) when the output voltage

is within 10% of the nominal output, thus improving the

performance of large pulsating loads. The in-regulation

current limit option provides the user to overload the

Enable Input

The

pin that allows on/off control of the regulator. The

when it goes into shutdown. The Enable input is

TTL/CMOS compatible for simple logic interfacing. When

EN is ‘H,’ the output voltage startup rising time is typically

25µs. Connect EN pin to IN pin for normal operation.

Power Good Flag

The

monitors the output voltage and signals an error

condition when the output voltage drops 10% below its

nominal value.

Under Voltage Lockout

When the input supply goes too low (typically below

2.0V), the

Voltage Lockout) signal that generates a fault signal and

shuts down the chip. This mechanism protects the chip

from producing false logic due to low input supply.