MIC2155/2156

Two-Phase, Single-Output, PWM

Synchronous Buck Control IC

MLF and MicroLead Frame are registered trademarks of Amkor Technologies

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

November 2009

M9999-111209-B

General Description

The MIC2155 and MIC2156 are a family of two-phase,

single-output synchronous buck control ICs featuring small

size, high efficiency, and a high level of flexibility. The ICs

implement a 500kHz (MIC2155) and 300kHz (MIC2156)

voltage mode PWM control, with the outputs switching

180

° out of phase. The result of the out-of-phase operation

is 1MHz (or 600kHz) input ripple with ripple current

cancellation,

minimizing

the

required

input

filter

capacitance. A 1% output voltage tolerance allows the

maximum level of system performance. Internal drivers

with adaptive gate drive allow the highest efficiency with

the minimum external components.

Two independent enable pins and a power good output

are provided, allowing a high level of control and

sequencing capability.

The MIC215x family has a junction operating range from

-40

°C to +125°C.

Data sheets and support documentation can be found on

Micrel’s web site at www.micrel.com.

Features

• Synchronous buck control ICs with outputs switching

180

° out-of-phase

• Remote sensing with internal differential amplifier

• 4.5V to 14.5V input voltage range

• Adjustable output voltages down to 0.7V

• 1% output voltage accuracy

• Starts up into a pre-biased output

• 500kHz PWM operation (MIC2155)

• 300kHz PWM operation (MIC2156)

• Adaptive gate drive allows efficiencies over 95%

• Adjustable current limit with no sense resistor

• Senses low-side MOSFET current

• Internal drivers allow 25A per phase

• Power Good output allow simple sequencing

• Dual enables with micro-power shutdown and UVLO

• Programmable soft-start pin

• Output over-voltage protection

• Works with ceramic output capacitors

• Multi-input supply capability

• Single-output high-current capability with master/slave

current sharing

• External synchronization

• Junction temperature range of -40°C to +125°C

Applications

• Multi-output power supplies with sequencing

• DSP, FPGA, CPU and ASIC power supplies

• DSL modems

• Telecom and networking equipment

• Servers