500Ω

100 kΩ

1

CS−

2

CS+

3

VDD

4

GND

13.5 V

to

15 V

+

Enable

and

Bias OK

+

Disconnect Switch

gM

+

3 V

+

8 CSO

7 LS

6 EAO

5 ADJ

Load Share

Bus Driver

+

3 V

Load Share Bus

Receiver

VBIAS

Fault

Protection

Error Amp

Adjust Amp

Current Sense

Amp

Start Up

and

Adjust

Logic

Copyright © 2016, Texas Instruments Incorporated

7

UCC29002, UCC29002-1, UCC39002

www.ti.com

SLUS495I – SEPTEMBER 2001 – REVISED MAY 2016

Product Folder Links: UCC29002 UCC39002

Submit Documentation Feedback

Copyright © 2001–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The UCC39002 is an advanced, high-performance, low-cost load-share controller that provides all the necessary

functions to parallel multiple independent power supplies and modules. The UCC39002 can easily parallel

currently available and popular synchronous buck converters, such as those designed with the TPS40050

controller.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Differential Current Sense Amplifier (CS+, CS

−, CSO)

The UCC39002 features a high-gain and high-precision amplifier to measure the voltage across a low-value

current sense resistor. Because the amplifier is fully uncommitted, the current sense gain is user programmable.

The extremely low input offset voltage of the UCC39002 current sense amplifier makes it suitable to measure

current information across a low value sense resistor. Furthermore, the input common mode range includes

sense amplifier is not unity gain stable and must have a minimum gain of three.

7.3.2 Load Share Bus Driver Amplifier (CSO)

This is a unity-gain buffer amplifier to provide separation between the load share bus voltage and the output of

the current sense amplifier. The circuit implements an ideal diode with virtually 0-V forward voltage drop by

placing the diode inside the feedback loop of the amplifier. The diode function is used to automatically establish

the role of the master module in the system. The UCC39002 which is assigned to be the master uses the load

share bus driver amplifier to copy its output current information on to the load share bus.