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UCC5880-Q1:UCC5880-Q1 PWM Voltage drop problem

Dongho Won
Prodigy 105 points

Part Number: UCC5880-Q1

Tool/software:

Hello.
I am testing a gate driver circuit using the UCC5880-Q1 and have encountered an issue.

Problem: When a 5V supply (VCC1) is applied to the UCC5880-Q1, the PWM signal voltage drops when transmitted.
The input PWM voltage to the gate driver stage is 5V, but after the drop, it falls below 3V.
(Note: No voltage drop occurs when VCC1 is not applied.)

Currently, I am using TI's ti28377s DSP, and the PWM signal path is as follows:
MCU → Darlington Transistor (KID65004AF) → UCC5880-Q1

The UCC5880-Q1 pin configurations are as follows:

GD0: Connected to DSP via a 100Ω series resistor
GD1: Connected to VCC1 (5V) via a 100Ω series resistor
GD2: Connected to VCC1 (5V) via a 100Ω series resistor
ASC_EN_PRI, ASC_PRI: Connected to GND
INN, INP: Each has a 100Ω resistor + 100pF capacitor in parallel (RC filter)
SCLK: Connected to GND1
NCS: Connected to VCC1
SDI: Connected to GND1
SDO: Open (No connection)
Please review. Let me know if you have any questions!"

  • 0
    TI__Intellectual 760 points

    Hi Dongho,

    Do you mean once you connect VCC1, the INP (not PWM) voltage will be drop to below 3V? It sounds like once the device power-up, the current from either KID65004AF or MCU is not enough to support a constant 5V on INP. Typically, the INP should be 5V before and after power up the VCC1. Couples of things that we can check:

    1. INP has a typical 70kohm pull-down resistance while INN has a typical 70kohm pull-up resistance.

    2. Would you please share a capture of schematics of the gate driver here? Or please let me know you would like to share through TI private chat that I can help on it.

    3. Would you please measure waveforms on VCC1, INP, INN and share with me?

    Regards,

    Luowei

  • 0 in reply to Luowei Wen
    Prodigy 105 points

    thanks your comment, but how can i use private? as you know, let me know how to use private chat

  • 0 in reply to Dongho Won
    TI__Intellectual 760 points

    Hi Dongho,

    I saw and accepted your private connection and we can use the private chat now to share the waveform or schematics if needed.

    Regards,

    Luowei