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Original question:

INA700: INA700 power sequence application

INA700: input voltage range

Noriyuki Takahashi
Genius 11710 points

Part Number: INA700
Other Parts Discussed in Thread: INA701

Tool/software:

Hi team 

Q1. What is the input voltage range of the device?

Customer is considering to use the device to monitor the condition below.

Current: 1A

Voltage: 24V


In case of 1A, the input voltage can be 2mΩ x 1A = 2mV.

In caes of 24V, the input voltage can be 24V. 

Q2. The difference between current measurement and voltage measurement can be 24V/2mV = 12000. So they are not sure how the 16-bit ADC can handle with the such a big diffrence. I think their assumption is something wrong, but could you clearfy this?

Regards,

Noriyuki Takahashi

Regards,

Noriyuki Takahashi

  • 0
    TI__Genius 9180 points

    Hi Noriyuki-san,

    The INA700 can measure full-scale currents up to +/- 15.728 A over a common-mode voltage range of -0.3V to 40V. 

    Noriyuki Takahashi said:
    Q2. The difference between current measurement and voltage measurement can be 24V/2mV = 12000. So they are not sure how the 16-bit ADC can handle with the such a big diffrence. I think their assumption is something wrong, but could you clearfy this?

    In this calculation, they've missed out the load resistance, which is significantly larger than the shunt resistor in the INA device, so current will not be 12000 A.

    For example, lets assume the load resistance is 1k, then Isense = 24V/(1k + 2m) = 23.9 mA.

    For the customer to decide if the INA700 fits their requirements, I'd recommend they check if the system's max current and bus voltage are within specified range.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    TI__Genius 11710 points

    Hi Mallika,

    According to the figure in the datasheet as below, it seems the device can meaure Vbus. In thier case, the Vbus is 24V. 

    And the datasheet mentions the bus voltage is measured with respect to device ground. 

    So again, their question is, is the ADC accurate enough to monitor from 1mV to 24V?

    Here is their condition.

    In case of 1A, the input voltage can be 2mΩ x 1A = 2mV.

    In caes of 24V, the input voltage can be 24V. 

    Regards,

    Noriyuki Takahashi

  • 0 in reply to Noriyuki Takahashi
    TI__Genius 9180 points

    Hi Noriyuki-san,

    Apologies for the misunderstanding, the bus voltage measurement gets scaled down to the same range as the shunt voltage in the front end before it goes to the ADC. 

    As a side note, if you intend to measure small currents such as 1A, the INA701 may be a better fit for your system. The INA701 will be released to market soon.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    TI__Genius 11710 points

    Hi Maillika

    Thanks.

    Mallika Senthil said:
    the bus voltage measurement gets scaled down to the same range as the shunt voltage in the front end before it goes to the ADC. 

    It seems that the resistive divider scaled the Vbus down, but I can't find any description related to the resistive divider in the datasheet. Could you please give more information so that they can calucate it quantitatively?

    Regards,

    Noriyuki Takahashi

  • 0 in reply to Noriyuki Takahashi
    TI__Genius 9180 points

    Hi Noriyuki-san,

    Unfortunately that is IP property of TI and can't be shared on a public platform. All necessary relevant specifications can be found in the datasheet.

    Best,
    Mallika Senthil