APW7104 データシートの表示（PDF） - Anpec Electronics

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APW7104

1.5MHz, 1A Synchronous Buck Regulator

Anpec Electronics 

APW7104

Function Description (Cont.)

Dropout Operation (Cont.)

An important detail to remember is that on resistance of

P-FET switch will increase at low input supply voltage.

Therefore, the user should calculate the power dissipa-

tion when the APW7104 is used at 100% duty cycle with

low input voltage.

Over-Temperature Protection (OTP)

The over-temperature circuit limits the junction tempera-

ture of the APW7104. When the junction temperature ex-

ceeds 150oC, a thermal sensor turns off the both power

MOSFETs, allowing the devices to cool. The thermal sen-

sor allows the converters to start a soft-start process and

regulate the output voltage again after the junction tem-

perature cools by 30oC. The OTP is designed with a 30oC

hysteresis to lower the average Junction Temperature

(T ) during continuous thermal overload conditions, in-

J

creasing the lifetime of the device.

Short-Circuit Protection

When the output is shortened to the ground, the frequency

of the oscillator is reduced to about 210kHz, 1/7 of the

nominal frequency. This frequency foldback ensures that

the inductor current has more time to decay, thereby pre-

venting runaway. The oscillator’s frequency will progres-

sively increase to 1.5MHz when VFB or VOUT rises above

0V.

Copyright © ANPEC Electronics Corp.

9

Rev. A.6 - Mar., 2012

www.anpec.com.tw

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