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VCA822: VCA822 Over-heating

Philp Thomas
Prodigy 10 points
Part Number: VCA822

Hi,


I'm implementing a Voltage Controlled Amp using a VCA822. I have got two ICs, each time I connect and power them up to +/- 5V and GND  the ICs over-heat to the point I am afraid they will be destroyed. There is no mention of any configuration in the datasheet that would cause this. Is there something I am missing? This also happens when I configure the IC into the basic test circuit in Fig 77 in the data sheet. I'm driving the Rg with a 10K pot and injecting a 8KHz signal from a generator into Vin.


Regards

Phil Thomas

  • 0
    TI__Mastermind 22825 points

    Hi Phil,

    Some suggestions / comments:

    1. Is there any indication of instability / oscillation that could cause the supply current to increase and the device to get hot? You could bring a high impedance scope probe close to the device and see if you pick up any hints of oscillation.

    2. Have you made sure your 1k feedback resistor leads are as short as possible?

    3. Are you terminating the input(s) with some low resistance (e.g. 20ohm shown in Figure 77) close to the pins?

    4. Are you driving a heavy load at the output (Page 37 calculation shows a high junction temperature with a heavy load connected).

    5. The gain control pin (VG, pin 2) has a very high bandwidth (200MHz typical). If you are driving this pin with a DC voltage, make sure you decouple this pin to ground using a cap close to the pin.

    6. Change up the Vref pin resistor (20ohm) to a lower value to see if the power dissipation issue / possible instability is affected?

    7. Make sure you have close / multiple decoupling caps next to the +/-5V pins to ground and that you're using a good ground plane on your board.

    Regards,

    Hooman