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TRF37A73: Absolute maximum input power

Part Number: TRF37A73

From the datasheet, the absolute maximum input power for this device is +10 dBm. This seems very low for most gain blocks and LNAs. Usually the number is on the order of +20 dBm. Is it possible to have this device see greater than +10 dBm for short (pulsed) periods of times with minimal degradation?

Can you expound on the failure mechanism for the stated abs max input power? Thanks!

  • Hi Sean,

    It is above the Absolute Maximum so I can neither confirm nor deny. However, the input is a 50 ohm integrated resistor in series with the base of an NPN transistor. The failure mode is likely to be this resistor popping like a fuse.

    Best regards,

    Sean
  • Sean,

    We've had experience before where other companies just listed an abs max without data to backup the value. Can you do some digging to see what justifies this number?

    Thanks!
  • Hi Sean McDevitt,

    a maximum input power of +10dBm is quite a lot for a chip which runs at a supply voltage of only 3.3V! You cannot compare this with a LNA running at 15V supply voltage...

    Kai

  • Kai, I'm not comparing this to devices running off of 15V. I'm comparing this with plenty of other devices that run off a 3.3V or 5.0V rail. Please go look through almost all of Analog's, Custom MMIC's, or MACOM's LNAs that run off of 3.3V (including much higher frequency components on far more sensitive processes). Most have an absolute maximum of 20 dBm.

    Please note that the 10 dBm limit also applies to the TRF series parts that are biased with 5.0V as well.

    Additionally, in a 50 Ohm system, 3.3V rms is ~23.3 dBm.

    Hittite (now ADI) actually used to have a good deal of their parts marked as +10 dBm ABS MAX due to a simple "boiler plate" process. Upon further investigation, they realized that the vast majority of their parts could take +20 dBm.

    I love these gain blocks. We just really want to understand how thoroughly vetted the +10 dBm ABS MAX number is. It doesn't make sense with similar parts across the industry nor does it make sense given the power output capability of the part nor with the increased supply voltage (5.0) for the other parts in the series.

    -Sean
  • Hi Sean,

    I have done some digging, and while I cannot provide exact transistor level schematics, it looks something like this, with a FET switch in series with the RB termination resistor that turns off for low power mode.

    The design goals for this part was 12-14dBm. It seems likely to me that they were unable to achieve this due to the voltage rating of that FET, and they did not want to sacrifice bandwidth in order to increase this rating. However, it is possible that this part could handle up to 14dBm. Higher than that you are likely to turn on ESD input protection diodes referenced to the rails, since this is only a 3.3V part. Please indicate whether this resolves your issue.

    Best regards,

    Sean