MIC37301 View Datasheet(PDF) - Micrel

Part Name

Description

Manufacturer

MIC37301

3.0A, Low-Voltage µCap LDO Regulator

Micrel 

Micrel, Inc.

Transient Response and 3.3V to 2.5V, 2.5V to 1.8V

or 1.65V, or 2.5V to 1.5V Conversions

The MIC37300/01/02/03 has excellent transient

response to variations in input voltage and load

current. The device has been designed to respond

quickly to load current variations and input voltage

variations. Large output capacitors are not required to

obtain this performance. A standard 47µF output

capacitor, preferably tantalum, is all that is required.

Larger values help to improve performance even

further.

By virtue of its low-dropout voltage, this device does

not saturate into dropout as readily as similar NPN-

based designs. When converting from 3.3V to 2.5V,

2.5V to 1.8V or 1.65V, or 2.5V to 1.5V, the NPN-

based regulators are already operating in dropout,

with typical dropout requirements of 1.2V or greater.

To convert down to 2.5V without operating in dropout,

NPN-based regulators require an input voltage of 3.7V

at the very least. The MIC37300/01/02/03 regulator

will provide excellent performance with an input as low

as 3.0V or 2.25V, respectively. This gives the PNP-

based regulators a distinct advantage over older,

NPN-based linear regulators.

Minimum Load Current

The MIC37300/01/02/03 regulator is specified

between finite loads. If the output current is too small,

leakage currents dominate and the output voltage

rises. A 10mA minimum load current is necessary for

proper operation.

Error Flag

The MIC37301 and MIC37303 feature an error flag

circuit that monitors the output voltage and signals an

error condition when the voltage is 5% below the

nominal output voltage. The error flag is an open-

collector output that can sink 10mA during a fault

condition.

Low output voltage can be caused by a number of

problems, including an overcurrent fault (device in

current limit) or low input voltage. The flag is

inoperative during overtemperature shutdown.

MIC37300/01/02/03

Enable Input

The MIC37301/02/03 also features an enable input for

on/off control of the device. Its shutdown state draws

“zero” current (only microamperes of leakage). The

enable input is TTL/CMOS compatible for simple logic

interface, but can be connected up to VIN. When

enabled, it draws approximately 15µA.

Adjustable Regulator Design

VIN

ENABLE

SHUTDOWN

MIC37302

IN OUT

R1

EN ADJ

GND

R2

VOUT

COUT

VOUT = 1.240V ⎛⎝⎜1+ RR21⎞⎠⎟

Figure 1. Adjustable Regulator with Resistors

The MIC37302 and MIC37303 allow programming the

output voltage any-where between 1.24V and the

5.5V maximum operating rating of the family. Two

resistors are used. Resistors can be quite large, up to

1MΩ, because of the very high input impedance and

low bias current of the sense comparator. The resistor

values are calculated by:

R1 =

R2⎜⎜⎝⎛

VOUT

1.240

− 1⎟⎟⎠⎞

Where VOUT is the desired output voltage. Figure 1

shows component definition. Applications with widely

varying load currents may scale the resistors to draw

the minimum load current required for proper

operation (see above).

October 2009

10

M9999-102909

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