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ADS8638: MUX and Supply voltages at 0-10v working scenario

JITHU T P
Prodigy 140 points
Part Number: ADS8638
Other Parts Discussed in Thread: ADS8668

Hi,

I am using ADS8638, 8 channel ADC for inputs of 0-10V. I am giving 3.3V as supply (DVDD & AVDD) and 10V for HVDD. Is it necessary to give HVSS mux voltage as -10V? Can I give 0V? How is 0-10V mode selected?

  • 0
    TI__Mastermind 39155 points

    Hi JITHU T P,

    Based on the data sheet, the maximum HVSS voltage is 0V and the 10V<HVDD-HVSS<30V is required, however all the specifications in the ADS8638 data sheet were characterized with HVDD=10V and HVSS=-10V or HVDD=10V~15V and HVSS=-10V~-15V for min/max at full temperature. The input range is selected in four range selection configuration registers. See the register map in the table 11 of ADS8638 data sheet.

    Can you please check if ADS8668 meets your requirement? This is the new generation device which is a 12-bit, 8-CH input SAR ADC to support direct 9 bipolar or unipolar input ranges including 0~10.24V range, but only requires a single 5V power supply for AVDD. ADS8668 has an integrated analog front-end (AFE) with 1Mohm high input impedance while an external amplifier on each channel for driving the ADC is not needed. Also, ADS8668 is one of ADC in the ADS8688 ADC family which offers a flexibility to upgrade to 14/16/18-bit resolution without any hardware pcb layout change because they are all pin-pin compatible.

    Thanks&regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 140 points

    Hi Dale,

    Thank you for the reply and suggestions.

    As of now, I don't have a 5v power supply in my system. I have 3.3V and 10V supply lines. 

    Since I using a 0-10v range configuration, is it ok if I ground HVSS(=0)?

    ie, if the configuration of power supply is HVDD = 10V, HVSS = 0V, AVDD = 3.3V, DVDD = 3.3V, and VREF = 2.5V(internal), will it work without any issue?

  • +1 in reply to JITHU T P
    TI__Mastermind 39155 points

    Hi JITHU T P,

    I apologized for missing your post. The 10V HVDD and 0V HVSS meet the power supply requirements in the datasheet, however the performance was not characterized and guaranteed, and also the HVDD/HVSS are used for internal multiplexer and it may need a headroom which we did not verify. I would suggest to use the new generation ADS8668 which only requires a LDO to generate a single 5V without the requirement of driving amplifiers. 

    Regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 140 points

    thank you dale. I had a look into ADS8668 and it fits well with my application but its cost is almost twice that of ADS8638. Is there any other option?

  • 0 in reply to JITHU T P
    TI__Mastermind 39155 points

    Hi JITHU T P,

    I suggest you to contact TI's local office in your region regarding the price. There is no other good option for your requirement.

    Regards,

    Dale