L

R1

R2

D

1

D2

BOOST

Output

Control

Logic

Current

Limit

Thermal

Shutdown

Under

Voltage

Lockout

Corrective Ramp

Reset

Pulse

PWM

Comparator

Current-Sense Amplifier

RSENSE

+

+

Internal

Regulator

and

Enable

Circuit

Oscillator

Driver

0.3:

Switch

Internal

Compensation

SW

EN

FB

GND

Error Amplifier

-

+

VREF

1.25V

COUT

ON

OFF

VBOOST

VSW

+

-

CBOOST

VOUT

CIN

VIN

VIN

ISENSE

+

-

+

-

1.375V

OVP

Comparator

Error

Signal

-

+

IL

LM2736

www.ti.com

SNVS316H – SEPTEMBER 2004 – REVISED DECEMBER 2014

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Output Overvoltage Protection

The overvoltage comparator compares the FB pin voltage to a voltage that is 10% higher than the internal

reference Vref. Once the FB pin voltage goes 10% above the internal reference, the internal NMOS control

switch is turned off, which allows the output voltage to decrease toward regulation.

7.3.2 Undervoltage Lockout

Undervoltage lockout (UVLO) prevents the LM2736 device from operating until the input voltage exceeds 2.74 V

(typ).

The UVLO threshold has approximately 440mV of hysteresis, so the part will operate until VIN drops below 2.3 V

(typ). Hysteresis prevents the part from turning off during power up if VIN is non-monotonic.

7.3.3 Current Limit

The LM2736 device uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle,

a current limit comparator detects if the output switch current exceeds 1.5 A (typ), and turns off the switch until

the next switching cycle begins.

7.3.4 Thermal Shutdown

Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature

exceeds 165°C. After thermal shutdown occurs, the output switch doesn’t turn on until the junction temperature

drops to approximately 150°C.

Copyright © 2004–2014, Texas Instruments Incorporated

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Product Folder Links: LM2736