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ADS1258 channel data problem

Xu Linfeng
Prodigy 90 points
Other Parts Discussed in Thread: ADS1258

Hi.

I'm using ADS1258 in auto-scan mode. The reference voltage is +2.5V. A problem have occured in my test. The input of channel 1 is +1V, and that of channel 2 is +235mV. The channel data of channel 1 is accurate +1V (about 0x3003b2). But the channel data of channel 2 is negative, -235mv (about 0xF4B351).

The chip was replaced by another ADS1258, the all channel data is OK.

Recently, I met the same problem again in another board. The channel data of one channel is adverse to the input. Why does this problem occur? And how to avoid it.

  • TI__Mastermind 43915 points

    Hi Xu,

    Off hand the only two things I can think of is either the MUXout/ADCin pins for the positive and negative terminals were routed incorrectly or the MUXSCH was set incorrectly. However, if you are saying you did not change anything in the hardware or software but simply replace a part, then it may be something part related. What are you writing to your registers to configure the ADC prior to converting channel 2? Are you enabling CHOP? What exactly are you writing to the MUXSCH register? Also, if using the ADS1258 in single ended mode, make sure Vcom is tied to ground.

    Regards,

    Tony Calabria

  • in reply to Tony Calabria
    Prodigy 90 points

    Hi Tony,

    Before coverting all channels, I only write CONFIG0 and CONFIG1 registers. The other registers are remained default values. I doesn't change MUXSCH register value. So I use single ended mode and auto-scan mode, and Vcom is tied to ground. CONFIG0 register is set to 0x0E, and CONFIG1 register is set to 0x80. So I enabled CHOP.

  • in reply to Xu Linfeng
    TI__Guru**** 181421 points

    Hi Xu,

    Did you find the problem in your channel data from the ADS1258?

  • in reply to Tom Hendrick
    Prodigy 90 points

    Hi Tom,

    I still don't know how the problem happened. Perhaps the pins are damaged by overvoltage or overheating. I don't know.