FB

SW

RTN

ON TIMER

DRIVER

BST

LEVEL

SHIFT

SD /

2.5V

THERMAL

SHUTDOWN

0.725A

BUCK

SWITCH

CURRENT

SENSE

COMPLETE

START

COMPLETE

START

Ron

100 P

L1

C2

15 P

R3

3.01k

R4

1k

R2

100k

R1

200k

C4

0.01P

C3

0.1 P

12 -75V

10V

LM5007

UVLO

FB

R6

1

UVLO

REGULATION

COMPARATOR

OVER-VOLTAGE

COMPARATOR

2.875V

SD

SD

COMPLETE

START

300nS MIN OFF

TIMER

C1

1 P

8

6

5

3

4

1

2

7

7V SERIES

REGULATOR

CURRENT LIMIT

OFF TIMER

SHUTDOWN

C5

0.1 P,

100V

D1

Q

CLR

Q

SET

S

R

+

-

+

-

+

-

LM5007

SNVS252F – SEPTEMBER 2003 – REVISED MARCH 2013

www.ti.com

Typical Application Circuit and Block Diagram

Pin Functions

Table 1. Pin Descriptions

Pin

Name

Description

Application Information

1

SW

Switching Node

Power switching node. Connect to the LC output filter.

2

BST

Boost Boot–strap capacitor input

An external capacitor is required between the BST and the SW

pins. A 0.01uF ceramic capacitor is recommended. An internal

diode between Vcc and BST completes the Buck gate drive bias

network.

3

Current Limit OFF time programming pin

A resistor between this pin and RTN determines the variation of

off time, along with the FB pin voltage, per cycle while in current

limit. The off time is preset to 17uS if FB =0V and decreases as

the FB pin voltage increases.

4

RTN

Circuit Ground

5

FB

Feedback Signal from Regulated Output

This pin is connected to the inverting input of the internal

regulation comparator. The regulation threshold is 2.5V.

6

On time set pin

A resistor between this pin and Vin sets the switch on time as a

function of Vin. The minimum recommended on time is 300ns at

the maximum input voltage.

7

Vcc

Output from the internal high voltage bias

If an auxiliary voltage is available to raise the voltage on this pin,

above the regulation set point (7V), the internal series pass

regulator will shutdown, reducing the IC power dissipation. Do

not exceed 14V. This output provides gate drive power for the

internal Buck switch. An internal diode is provided between this

pin and the BST pin. A local 0.1uF decoupling capacitor is

recommended. Series pass regulator is current limited to 10mA.

8

Vin

Input supply voltage

Recommended operating range: 9V to 75V.

-

EP

Exposed PAD, underside of the WSON

Internally bonded to the die substrate. Connect to GND potential

package option

for low thermal impedance.

2

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