LM5111

INB

INA

0.1 µF

1.0 µF

N/C

INA

2

VEE

3

INB

4

7

6

5

8

N/C

OUTA

VCC

OUTB

1

Copyright © 2016, Texas Instruments Incorporated

11

LM5111

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SNVS300H – JULY 2004 – REVISED SEPTEMBER 2016

Product Folder Links: LM5111

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Copyright © 2004–2016, Texas Instruments Incorporated

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

High-frequency power supplies often require high-speed, high-current drivers such as the LM5111 family. A

leading application is the need to provide a high-power buffer stage between the PWM output of the control IC

and the gates of the primary power MOSFET or IGBT switching devices. In other cases, the driver IC is used to

drive the power-device gates through a drive transformer. Synchronous rectification supplies are also needed to

simultaneously drive multiple devices which presents an extremely large load to the control circuitry.

Driver ICs are used when use of the primary PWM regulator IC to directly drive the switching devices for one or

more reasons is not feasible. The PWMIC does not have the brute drive capability required for the intended

switching MOSFET, limiting the switching performance in the application. In other cases, there may be a desire

to minimize the effect of high-frequency switching noise by placing the high current driver physically close to the

load. Also, newer ICs that target the highest operating frequencies do not incorporate onboard gate drivers at all.

Their PWM outputs are only intended to drive the high impedance input to a driver such as the UCCx732x.

Finally, the control IC is under thermal stress due to power dissipation, and an external driver helps by moving

the heat from the controller to an external package.

9.2 Typical Application

Figure 12. LM5111 Driving Two Independent MOSFETs

9.2.1 Design Requirements

To select the proper device from the LM5111 family, TI recommends first checking the appropriate logic for the

outputs. LM5111 has dual inverting outputs; dual noninverting outputs; inverting channel A and noninverting

channel B. Refer to operating modes to select which driver from the family is required in a given application.

Moreover, some design considerations must be evaluated first in order to make the most appropriate selection.

Among these considerations are VCC and power dissipation.