LM27212MTD NSC [National Semiconductor], LM27212MTD Datasheet

LM27212MTD

Manufacturer Part Number

LM27212MTD

Description

Two-Phase Current-Mode Hysteretic Buck Controller

Manufacturer

NSC [National Semiconductor]

Datasheets

1.LM27212.pdf (23 pages)

2.LM27212MTD.pdf (23 pages)

3.LM27212MTD.pdf (23 pages)

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LM27212

Two-Phase Current-Mode Hysteretic Buck Controller

General Description

The LM27212 is a two-phase synchronous buck regulator

controller that is designed to support high-current loads such

as microprocessors.

The IC employs a two-phase current-mode hysteretic control

mechanism. During normal operation, the two switching

channels operate 180˚ out of phase, helping reduce the

number of input capacitors.

Inductor currents are sensed through low value sense resis-

tors. Current sharing between the two channels is automati-

cally guaranteed by multiplexing the feedback comparator.

The regulator input voltage range supported by the LM27212

is 5V to 30V. The output voltage is programmed through six

voltage identification pins and ranges from 0.700V to 1.708V

in 64 steps.

The IC provides accurate load-line characteristic. The regu-

lator can be programmed to lower its output voltage linearly

with increasing load current, so that the power generated by

the load can be significantly reduced.

Since the error in the output voltage directly sets the inductor

currents, the dynamic response to a large and fast load

transient is close to a square wave. This is optimal for

meeting CPU supply voltage specifications.

Due to the intrinsic input voltage feed forward characteristic

of a peak current-mode controller, the IC has a superior line

transient response.

The IC provides a cycle-by-cycle peak current limit, over-

voltage protection, and a power good signal.

The LM27212 fully supports the Stop CPU mode and Sleep

mode required by some mobile CPUs. In the Sleep mode,

the IC enters single-phase power-saving operation which

significantly enhances the light load efficiency.

Typical Application

DS201520

The LM27212 also has a soft start pin for the external

adjustment of soft start speed.

The LM27212 combined with the LM27222 series of MOS-

FET drivers, provides a layout-friendly, thermally optimized

and noise-immune power solution for the mobile platform.

Features

n 5V to 30V input range

n Two channels operating 180˚ out of phase

n Ideal load and line transient responses

n Dynamic output voltage swing supported

n Excellent inductor current sharing

n High efficiency Sleep mode

n Soft start and soft shutdown

n Cycle-by-cycle current limit

n Adjustable over-voltage protection

n Accurate load-line supported

n On/off pin and power good signal

n TSSOP package or tiny LLP package

Applications

n Power Supply For Mobile CPUs

n Low Output Voltage Buck Regulators Up To 50A

1% reference over temperature

20152031

www.national.com

March 2006

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