QuikEval LTC2662 - measuring output current

I'm trying to set the output channels on the LTC2662 through the QuikEval GUI, but I keep receiving fault messages, so I'm hoping I can get some help or explanation as to why this is happening.

Here's how I'm setting up my connections:

I'm using the DC2692A demo board for this. As described in the Help > Show Online webpages of QuikEval, I'm connecting V+ to 15V, V- to -15V, and GND to ground on the demo board. I have no other connections other than probes, so please do let me know if I'm missing something crucial.

When I open the QuikEval GUI, I do these things in this order:

  1. Change Span for All DACs to 100mA
  2. Enable Specify Currents in mA
  3. Change the Channel 0 value to ~5mA, then Write & Update

The immediate error I get is either the red Fault LED turning on or an OC error on the GUI (both telling me the same thing, I assume). If I return everything to default, I'm able to get the correct V+ and V- values through the Monitor Mux Channel, which leads me to think that I am missing some steps in my list above.

All I want to do is be able to see a current on my multimeter that matches the current I'm setting in the GUI, so I'd appreciate any help, or even better, a step-by-step on how to set this up and avoid the OC fault. I've read through all the datasheets, but I wouldn't put it past myself to have missed an important paragraph. 

Thanks in advance.

Parents
  • I was able to figure out what was causing my issue after getting help from an FAE, and I'm posting it here for anyone who might need it in the future. 

    Power Supply

    V+ and V- do not have to be 15V and -15V like the LTC2662 help page says. V- must be between roughly -15V and 0V, and V+ between roughly 3V and 33V. Just make sure the difference between V+ and V- is less than 33V. I ended up using 12V and 0V. 

    The board was having trouble generating the current that the GUI specified because the current supplied wasn't enough. The upper limit V+ current is somewhere above 80mA, but even setting the current limit to 80mA was enough to prevent current limiting. 

    DMM Probes

    The reason I was getting the OC (open circuit) error was because I wasn't connecting the outputs properly. To measure current from channel 0, connect the digital multimeter probes to OUT0 and GND.

    After setting all of the above up, the current on my digital multimeter finally matched the GUI settings.

    Additional Notes

    It's not advised (maybe not safe for the chip) to generate 300mA on all channels at the same time due to temperature limitations. Even a lower current on all channels may cause issues. Try not to go above 100 Celcius, if possible. I'm keeping an eye on the chip using a scanning thermometer. 

    Oh also, there's an LTC2662 FAQ page.

  • 0
    •  Analog Employees 
    •  Super User 
    on Sep 6, 2021 8:48 AM in reply to bananapeel

    Hi. Thanks for sharing this info. 

    Cheers!

    Ian

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