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OPA564: Over current flag permantently activated, even at no load

Stefan_S
Prodigy 10 points
Part Number: OPA564


Support Path: /Product/Development and troubleshooting/

Hi,

 

We are using the OPA564 as power amplifier for driving inductive sensors in a massive multi-channel application. The complete system includes ~200 amplifier channels. The amplifiers are actively cooled (air) and thermally monitored, the average die temperature is below 85°C with short time maximas of up to 110°C. The amplifier supply is bipolar (+-11.6V), the configuration is inverting, input and output protection diodes according to datasheet, and we drive an inductive load at 280mApp at 70kHz, with the current limit set to 580mA (Rset=36kOhm).

 

Recently some a slowly growing number of single amplifiers began setting the overcurrent-flag. Analysis of the affected modules shows, the current flag is set if the amplifier is enabled, even if no load is attached. Nevertheless the amplifier channel itself operates as expected, the output signal with and without load is completely ok (voltage and current waveforms checked). The rate of these false alarm is higher at rising board and amplifier temperatures.

 

Therefore I have two questions:

Q1: What is the reason for this behavior, what causes the OC-flag to be activated, even at no output current?

Q2: Apart from above topic, we observe that all amplifiers in general set the overcurrent flag, if the amplifier if the amplifier is disabled via the EN-pin. Is this intended?

 

Thanks, Stefan

  • 0
    TI__Guru* 93105 points

    Hello Stephan,

    When the OPA564 devices begin to set the over-current flag is are they actually going into current limit as well? Do you know if the amplifiers are going into thermal shutdown when that happens?

    Can you share the schematic of your OPA564 application circuit? If so, please provide the details of the input signal, output signal and the output load. Also, have you observed the OPA564 output with a DSO, with and without the inductive load connected? Is there any evidence of oscillation with the DSO?

    Q1: What is the reason for this behavior, what causes the OC-flag to be activated, even at no output current? - That will have to be determined

    Q2: Apart from above topic, we observe that all amplifiers in general set the overcurrent flag, if the amplifier if the amplifier is disabled via the EN-pin. Is this intended? - That is an interesting observation. It surely has to do with the way the enable/disable and flag circuit designs interact internally.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0
    TI__Guru* 93105 points

    This inquiry is now being handled directly with the customer. It is being closed on the E2E.

    Regards, Thomas

    Precision Amplifiers Applications Engineering