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UCC23313: UCC23313 driver input diode configuration

Rakeshkumar Yadav
Prodigy 50 points
Part Number: UCC23313
Other Parts Discussed in Thread: UCC23525

Tool/software:

Hi,

We are replacing HL11L1 and TSC428 circuit with UCC23313BDWRY, As they have used R and RC (R736, R727 and R737) to drive opto-coupler (H11L1) as shown below.

Is this RC circuit is needed for UCC23313 as well to fast turn ON and turn OFF? Switching frequency is 1.2KHz.

I want to understand how it will affect the opto-coupler rise and fall time. 

  • 0
    TI__Genius 17486 points

    Hi Rakeshkumar,

    The rise time of the output will not be affected by the input drive of the UCC23313. The input die sends the same signal to the output side for a low input current as for a high input current; then the predriver on the output side will send the same drive strength to the main output stage.

    You only need ~10mA of input current for the UCCC23313, so the buffer stage is not necessary for this opto-emulator. If the input voltage signal is 5V, you should use around 300 ohms in series to drive the input.

    An updated version of the UCC23313 is the UCC23525. You can try this device if your customer would benefit from a faster rise time.

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    Prodigy 50 points

    Hi Sean,

    Thank you for your answer.

    I have one more query regrading power dissipation of UCC23313.

    In datasheet it is mentioned power dissipation of input side diode is 10mW and also they have mentioned 40mW and 55mW in Note, please let us know which parameter need to considered for design, our operating temperature range is from -40°C to 85°C.

  • 0 in reply to Rakeshkumar Yadav
    TI__Genius 17486 points

    Hi Rakeshkumar,

    This device can safely handle a 16mA continuous input current across the operating temperature range. That is an input power of about 16mA*2.1V=33.6mW, so I trust the 40mW power dissipation value is a safe operating power for just the input side.

    However, it seems like the writer of the datasheet was trying to limit the total PD overall below 750mW, which is a package thermal rating. The 180nF load is a high output load, so there is less thermal budget for power dissipation on the input side. If you do have 40mW of power dissipation on the input die, you should try to limit the output power to below 710mW.

    Best regards,

    Sean