MIC2177

2.5A Synchronous Buck Regulator

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (

April 2008

M9999-042108

General Description

The Micrel MIC2177 is a 200kHz synchronous buck (step-

down) switching regulator designed for high-efficiency,

battery-powered applications.

The MIC2177 operates from a 4.5V to 16.5V input and

features internal power MOSFETs that can supply up to 2.5A

output current. It can operate with a maximum duty cycle of

100% for use in low-dropout conditions. It also features a

shutdown mode that reduces quiescent current to less than

5µA.

The MIC2177 achieves high efficiency over a wide output

current range by switching between PWM and skip mode.

Operating mode is automatically selected according to output

conditions. Switching frequency is preset to 200kHz and can

be synchronized to an external clock signal of up to 300kHz.

The MIC2177 uses current-mode control with internal current

sensing. Current-mode control provides superior line

regulation and makes the regulator control loop easy to

compensate. The output is protected with pulse-by-pulse

current limiting and thermal shutdown. Undervoltage lockout

turns the output off when the input voltage is less than 4.5V.

The MIC2177 is packaged in a 20-pin wide power SO

package with an operating temperature range of –40°C to

+85°C.

See the MIC2178 for externally selected PWM or skip-mode

operation.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• 4.5V to 16.5V input voltage range

• Dual-mode operation for high efficiency (up to 96%)

–

PWM mode for > 200mA load current

–

Skip mode for < 200mA load current

• 100mΩ internal power MOSFETs at 12V input

• 200kHz preset switching frequency

• Low quiescent current

–

1.0mA in PWM mode

–

500µA in skip mode

–

< 5µA in shutdown mode

• 100% duty cycle for low dropout operation

• Current-mode control

–

Simplified loop compensation

–

Superior line regulation

• Current limit

• Thermal shutdown

• Undervoltage lockout

Applications

• High-efficiency, battery-powered supplies

• Buck (step-down) dc-to-dc converters

• Cellular telephones

• Laptop computers

• Hand-held instruments

• Battery Charger

_________________________________________________________________________________________________________

Typical Application

BIAS

SGND

EN

COMP

PGND

FB

OUT

VIN

C2

100µF

10V

5V/1A

L1, 50µH

6.8nF

C3

R1

0.01µF

10k

MIC

2177-5.0

AUTO

SYNC

R1

10k

5.4V to 18V

C1

22µF

35V

U1

20

18

11

13

14–17

19

12

4–7

3,8

1,2,9

D1

MBRS130L

SW

10

ENABLE

SHUTDOWN

2.2

nF

70

75

80

85

90

95

100

10

100

1000 2500

OUTPUT CURRENT (mA)

5V Output

Efficiency

V

SKIP

PWM