LM5045

SNVS699G – FEBRUARY 2011 – REVISED MARCH 2013

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PIN DESCRIPTIONS (continued)

HTSSOP

WQFN

Name

Description

Application Information

Pin

Pin

15

11

SSOFF

Soft-Stop Disable

When SS OFF pin is connected to the AGND, the LM5045 soft-

stops in the event of a VIN UVLO and Hiccup mode current limit

condition. If the SSOFF pin is connected to REF pin, the controller

hard-stops on any fault condition. Refer Table 1 for more details.

19

15

SR2

Synchronous Rectifier Driver

Control output for synchronous rectifier gate. Capable of peak

sourcing 100mA and sinking 400mA.

21

17

VCC

Output of Start-Up Regulator

The output voltage of the start-up regulator is initially regulated to

9.5V. Once the secondary side soft-start (SSSR pin) reaches 1V,

the VCC output is reduced to 7.7V. If an auxiliary winding raises the

voltage on this pin above the regulation set-point, the internal start-

up regulator will shutdown, thus reducing the IC power dissipation.

22

18

PGND

Power Ground

Connect directly to Analog Ground

23, 20

19, 16

LO1, LO2

Low Side Output Driver

Alternating output of the PWM gate driver. Capable of 1.5A peak

source and 2A peak sink current.

24

20

SR1

Synchronous Rectifier Driver

Control output for synchronous rectifier gate. Capable of peak

sourcing 100mA and sinking 400mA.

25, 18

21, 14

BST1,2

Gate Drive Bootstrap

Bootstrap capacitors connected between BST1,2 and SW1,2

provide bias supply for the high side HO1,2 gate drivers. External

diodes are required between VCC and BST1,2 to charge the

bootstrap capacitors when SW1,2 are low.

26, 17

22, 13

HO1,2

High Side Output Driver

High side PWM outputs capable of driving the upper MOSFET of

the bridge with 1.5A peak source and 2A peak sink current.

27, 16

23, 12

HS1,2

Switch Node

Common connection of the high side FET source, low side FET

drain and transformer primary winding.

28

24

VIN

Input Power Source

Input to the Start-up Regulator. Operating input range is 14V to

100V. For power sources outside of this range, the LM5045 can be

biased directly at VCC by an external regulator.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

4

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