LM5102

PUSH

PULL

33 - 76V

HI

VIN

LM5041

VCC

HD

LD

COMP

VDD

HB

LO

VSS

RT1

LI

RT2

HO

HS

+

+

LM5100

HI

VDD

HB

LO

LI

HO

HS

FEED

BACK

VOUT

L1

T1

T1

LM5041

www.ti.com

SNVS248D – AUGUST 2003 – REVISED MARCH 2013

Soft-start and Shutdown

The soft-start feature allows the power converter to gradually reach the initial steady state operating point,

thereby reducing start-up stresses and surges. At power on, a 10uA current is sourced out of the soft-start pin

(SS) to charge an external capacitor. The capacitor voltage will ramp up slowly and will limit the maximum duty

cycle of the buck stage. In the event of a fault as indicated by VCC Under-voltage, line Under-voltage or second

level current limit, the output drivers are disabled and the soft-start capacitor is discharged to ground. When the

fault condition is no longer present, a soft-start sequence will begin again and buck stage duty cycle will

gradually increase as the soft-start capacitor is charged. The SS pin also serves as an enable input. The

controller will enter a low power state if the SS pin is forced below the 0.45V threshold.

Thermal Protection

Internal Thermal Shutdown circuitry is provided to protect the integrated circuit in the event that the maximum

junction temperature is exceeded. When activated, typically at 165 degrees Celsius, the controller is forced into a

low-power standby state, disabling the output drivers and the bias regulator. This feature is provided to prevent

catastrophic failures from accidental device overheating.

Typical Application

Figure 13. Simplified Cascaded Half-Bridge

Copyright © 2003–2013, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links: LM5041