T8302 データシートの表示（PDF） - Taiwan Memory Technology

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T8302

PWM Control 1A Step-Down Converter

Taiwan Memory Technology 

tm TE

CH

T8302

Driving the ADJ input via open collector transistor

The recommended method of driving the ADJ pin and controlling the amplitude of the PWM

waveform is to use a small NPN switching transistor as shown below:

This scheme uses the 64kohm resistor between the ADJ pin and the internal voltage reference as a

pull-up resistor for the external transistor.

Driving the ADJ input from a microcontroller

Another possibility is to drive the device from the open drain output of a microcontroller. The

diagram below shows one method of doing this:

If the NMOS transistor within the microcontroller has high Drain / Source capacitance, this

arrangement can inject a negative spike into ADJ input of the T8302 and cause erratic operation but

the addition of a Schottky clamp diode (cathode to ADJ) to ground and inclusion of a series resistor

(10K) will prevent this. See the section on PWM dimming for more details of the various modes of

control using high frequency and low frequency PWM signals.

Shutdown mode

Taking the EN pin to a voltage below 0.8V for more than approximately 100us, will turn off the

output and supply current will fall to a low standby level of 70uA nominal.

TM Technology, Inc. reserves the right

P. 7

to change products or specifications without notice.

Publication Date:April 2014

Revision: E

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