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LMP7721 specifications at cold temperatures(-20C)

user4752936
Prodigy 90 points
Other Parts Discussed in Thread: LMP7721

Hi,

We are investigating to use a bare die version of LMP7721 at cold temperatures.

Some key parameters at cold temperatures are missing from the specification.

So could I get the following parameters/curves at -20C?

- PSRR

- CMRR

- En (input-referred voltage noise). I am interesting noise at frequencies 0 to 200Hz 

- In (input referred current noise, 0 to 200Hz)

- Ibias

-Mika-

  • 0
    TI__Guru 60786 points

    Hello Mika,

    The datasheet specifies the limits for both PSRR and CMRR over temperature. We do not have specific data or limits *at* -20°C. Noise was only done at room temp.

    The Ibias was done in the SOIC package.

    The bias current will follow the 2x every 10°C, so the current will decrease by half every 10°C going cold. The LMP7721 uses a bootstrapped ESD structure to reduce the input leakage currents. This reduces the magnitude of the leakage, but the reduced magnitude still follows the same 2x per 10°slope.

    However, you usually hit a "flatland" just before room temp where the package and other internal leakages dominate the decreasing input stage leakages. Since you are using die form, you can probably remove about 1fA for the package leakage.

    Looking back at the char data, the typical bias current was 3fA at 25°C, and 1fA at -40°C, so it is well into the flattened region. You can use the 25°C min/max number for -20°C

    Regards,

  • 0 in reply to Paul Grohe
    Prodigy 90 points

    Hi,

    Could you ask from your design team how those parameters are behaving at cold temp? (they should know it). It doesn't be exact value at -20C but some good estimation.

    PSRR and CMRR are typically better at cold temp but it is impossible know according your specification.

    Also En is very important for us( it will be amplified in our design) if we don't know the benefits of the cold temp usage then we will not use your part.

    -Mika-