FB

SW

RTN

DRIVER

BST

SS

LM5010A

7V BIAS

REGULATOR

+

-

SGND

ISEN

C6

GND

LEVEL

SHIFT

LOGIC

Driver

Gate Drive

UVLO

START

260 ns

OFF TIMER

OVER-VOLTAGE

COMPARATOR

GND

BYPASS

SWITCH

Shutdown

Input

THERMAL

SHUTDOWN

ON TIMER

COMPLETE

START

C5

C1

RON

Input

6V-75V

C3

C4

L1

D1

C2

R2

R1

R3

RSENSE

50 m:

CURRENT LIMIT

COMPARATOR

REGULATION

COMPARATOR

2.9V

VIN

Q1

RCL

(optional)

VOUT

62.5 mV

11.5 PA

2.5V

Q2

SD

RON

COMPLETE

VCC

UVL

VIN SENSE

VCC

VIN

RON/SD

0.7V

Copyright © 2016, Texas Instruments Incorporated

9

LM5010A, LM5010A-Q1

www.ti.com

SNVS376F – OCTOBER 2005 – REVISED MAY 2016

Product Folder Links: LM5010A LM5010A-Q1

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Copyright © 2005–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM5010Ax step-down switching regulator features all the functions needed to implement a low-cost, efficient,

buck bias power converter. This high-voltage regulator contains a 75-V N-channel buck switch, is easy to

implement, and is provided in HTSSOP-14 and thermally-enhanced, WSON-10 packages. The regulator is based

on a control scheme using an ON-time inversely proportional to VIN. The control scheme requires no loop

compensation. The functional block diagram of the LM5010Ax is shown in the Functional Block Diagram.

The LM5010Ax can be applied in numerous applications to efficiently regulate down higher voltages. This

regulator is well-suited for 48-V telecom and 42-V automotive power bus ranges. Additional features include:

thermal shutdown, VCC undervoltage lockout, gate drive undervoltage lockout, maximum duty cycle limit timer,

and the valley current limit functionality.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Control Circuit Overview

The LM5010Ax employs a control scheme based on a comparator and a one-shot ON timer, with the output

voltage feedback (FB) compared to an internal reference (2.5 V). If the FB voltage is below the reference the

buck switch is turned on for a time period determined by the input voltage and a programming resistor (RON).

Following the ON-time the switch remains off for a fixed 260 ns OFF-time, or until the FB voltage falls below the

reference, whichever is longer. The buck switch then turns on for another ON-time period. Referring to the Block

Diagram, the output voltage is set by R1 and R2. The regulated output voltage is calculated with Equation 1.

VOUT = 2.5 V × (R1 + R2) / R2

(1)

The LM5010Ax requires a minimum of 25 mV of ripple voltage at the FB pin for stable fixed-frequency operation.

If the output capacitor’s ESR is insufficient, additional series resistance may be required (R3 in the Block

Diagram).