f

OSC

S

S

G

1

G

2

Q

1

Q

2

Vcc

GND

GND

D2

SN6501

D1

S

S

Freq.

Divider

OSC

BBM

Logic

SN6501

www.ti.com

SLLSEA0E – FEBRUARY 2012 – REVISED JANUARY 2013

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.

Figure 45. 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

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.

Figure 46. Detailed Output Signal Waveforms

PUSH-PULL CONVERTER

Push-pull converters require transformers with center-taps to transfer power from the primary to the secondary

(see Figure 47).

Copyright © 2012–2013, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links :SN6501