8 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, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

The SN6501 is a transformer driver designed for low-cost, small form-factor, isolated DC-DC converters utilizing

the push-pull topology. The device includes an oscillator that feeds a gate-drive circuit. The gate-drive,

comprising a frequency divider and a break-before-make (BBM) logic, provides two complementary output

signals which alternately turn the two output transistors on and off.

Vcc

GND

GND

D2

SN6501

D1

S

S

G2

G1

fOSC

Freq.

Divider

OSC

BBM

Logic

Q1

Q2

Q1 on

Q2 on

Q2 off

tBBM

Q1 off

Figure 8-1. SN6501 Block Diagram And Output Timing With Break-Before-Make Action

The output frequency of the oscillator is divided down by an asynchronous divider that provides two

complementary output signals, S and S, with a 50% duty cycle. A subsequent break-before-make logic inserts a

dead-time between the high-pulses of the two signals. The resulting output signals, G1 and G2, present the gate-

drive signals for the output transistors Q1 and Q2. As shown in Figure 8-2, before either one of the gates can

assume logic high, there must be a short time period during which both signals are low and both transistors are

high-impedance. This short period, known as break-before-make time, is required to avoid shorting out both

ends of the primary.

f

OSC

S

S

G

1

G

2

Q

1

Q

2

Figure 8-2. Detailed Output Signal Waveforms

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SN6501

SLLSEA0I – FEBRUARY 2012 – REVISED JANUARY 2021

Copyright © 2021 Texas Instruments Incorporated

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Product Folder Links: SN6501