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LM3242: Performance below -30C

Sara Caron1
Prodigy 115 points
Part Number: LM3242
Other Parts Discussed in Thread: TPS62864, TPS62800

I have to turn on the system at -40C and operate within 1 minute without external heating. Since the part is operational temperature of -30C min does the output gain go higher than set by VCON at -30C and by how much? Chances are that it will be -30C by heating of the components near it but I would like to know how it varies at cold.I am desiring Vout 0.4V +/-50mV over the temp range -40 to +60C and like to ensure that it will start up at cold.

  • 0
    TI__Guru*** 142910 points

    Hi Sara,

    This device is only specified to operate down to -30C, so we cannot say what it may or may not do at -40 C.

    Do you just need a converter which delivers 0.4Vout?  Or do you need to adjust that voltage during operation?  Do you need an RFPA type of device, with the VCON function?  

    We have the TPS628680A, for example, which uses I2C to adjust the output voltage within that very low range.  Or, the TPS628610 can go down to 0.4V with I2C.

    Thanks,

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 115 points

    I need a converter which delivers 0.4V @ 125mA continuous, 130 mA Inrush. Vin =4V. High Efficiency as possible. And I need 30 pieces ASAP. I do not have I2C available. The LM3242 is available in distribution. I would prefer not to use the LM3242 but it seems I have no other option at this time. I worked with TI apps chat session trying to find a part to use that was available  and it came down to this part.

  • 0 in reply to Sara Caron1
    TI__Guru*** 142910 points

    Thanks for explaining the history and that you need a fixed 0.4Vout converter and don't need to adjust the voltage during operation.  Most of these RFPA devices assume that you will adjust the voltage.

    You can use the TPS628680A/1A without I2C to output a fixed 0.4V voltage.  See table 8-1 in the D/S for the appropriate resistor value.  The TPS62864/6 is a similar device.

    The TPS62800/6 can also output 0.4V.

    All these devices are rated down to -40C.  Unfortunately, TI.com is not showing any stock for them today.

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 115 points

    I bought 2 LM3242 evaluation boards to test at the low end of the temperature. Thanks for your support.

  • 0 in reply to Sara Caron1
    TI__Guru*** 142910 points

    You're welcome!