Control

Logic

Over

temp

OSC

RAMP

INT

SS

VREF

+

-

AVIN

EN

ILIM

SS/TRK

FB

COMP

AGND

PGND

PGOOD

SW

PVIN

PWM

comparator

UVLO

Precision

enable

UVP

SD

Ilimit low

Ilimit high

Zero-cross

Driver

OVP

Powerbad

PWM

0.68V

0.54V

CURRENT

LIMIT

AVIN

AVIN

PVIN

PVIN

OR

OR

OR

+

-

+

-

+

-

+

-

+

-

EA

+

-

+

-

Driver

2.7V

1.35V

0.6V

LM21215

SNVS625E – FEBRUARY 2011 – REVISED MARCH 2013

www.ti.com

Block Diagram

Operation Description

GENERAL

The LM21215 switching regulator features all of the functions necessary to implement an efficient low voltage

buck regulator using a minimum number of external components. This easy to use regulator features two

integrated switches and is capable of supplying up to 15A of continuous output current. The regulator utilizes

voltage mode control with trailing edge modulation to optimize stability and transient response over the entire

output voltage range. The device can operate at high switching frequency allowing use of a small inductor while

still achieving high efficiency. The precision internal voltage reference allows the output to be set as low as 0.6V.

Fault protection features include: current limiting, thermal shutdown, over voltage protection, and shutdown

capability. The device is available in the HTSSOP-20 package featuring an exposed pad to aid thermal

dissipation. The LM21215 can be used in numerous applications to efficiently step-down from a 5V or 3.3V bus.

PRECISION ENABLE

The enable (EN) pin allows the output of the device to be enabled or disabled with an external control signal.

This pin is a precision analog input that enables the device when the voltage exceeds 1.35V (typical). The EN pin

has 110 mV of hysteresis and will disable the output when the enable voltage falls below 1.24V (typical). If the

EN pin is not used, it can be left open, and will be pulled high by an internal 2 µA current source. Since the

enable pin has a precise turn-on threshold it can be used along with an external resistor divider network from VIN

to configure the device to turn-on at a precise input voltage.

10

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