UC1875: IC not working

prashant surana

Part Number: UC1875

Hi TI

I am using UC1875 PWM IC for full bridge converter. I am not getting pulses and Vref is coming 5.9V ( it should be 5V). I am getting good slope as per datasheet. I have tried multiple ICs but everytime I get 5.9V Vref.

When I connect Vref to Non inverting terminal of IC (EA+ pin 4) through potential divider circuit, I get zero voltage at EA+ pin.

I just want to know is there a problem in IC because multiple ICs are showing same response?

I have attached Schematic. EA- pin is grounded.

With Regards

Prashant Surana

over 6 years ago

0 Wade Vonbergen over 6 years ago

TI__Guru 62930 points

Prashant,
The engineer supporting this device is out for Holidays. They will return January 2nd, and can respond to your query.
Thanks,
Wade

0 Daniel Hartung over 6 years ago

TI__Mastermind 26305 points

Hey Prashant,

Are you running the IC is Current mode control or Voltage mode control?

The RAMP pin is suggested to be connected to a current sense resistor configuration in current mode and a capacitor for voltage mode configuration.

Thanks,

Daniel

0 Daniel Hartung over 5 years ago in reply to Daniel Hartung

TI__Mastermind 26305 points

Hey Prashant,

Did the issue work itself out?

Thanks,
Daniel

0 prashant surana over 5 years ago in reply to Daniel Hartung

Prodigy 20 points

Hi Daniel

I am running IC in voltage mode control. Ramp pin is connected to a capacitor as shown in schematic. Still the problem persists. I am not getting any of the four output. But I am seeing good ramp at ramp pin. I think I have drawn high currents from outputs which may have damaged output pins.
If I shorts output pins to ground, will it damage the IC or temporary shut it down?

With Regards
Prashant Surana

0 Daniel Hartung over 5 years ago in reply to prashant surana

TI__Mastermind 26305 points

Hey Prashant,

Shorting the output pins will damage the device as the output pins are not current limited.

The pins have an absolute maximum rating of 0.5 ADC and 3 A pulse.

If you wish to disable the device a safer way is pulling the C/S+ pin up.

Thanks,

Daniel

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UC1875: IC not working