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I am using this LNA in my design and I have an issue with how the devices is being powered.

The turn off/turn On procedure is as following: Apply drain voltage first (5 V) THEN apply gate voltage (3 V)

Turn off procedure is the complete opposite, turn off gate voltage and THEN turn off drain voltage.

Doing it in the wrong order will burn the LNA unfortunately even if there is a microsecond delay between the start up sequence.

Both supplies 5 V and 3 V are coming from separate LDO's.

What options do I have in order to make sure that when I turn on the PCB this procedure will be applied, and vice versa when I disconnect the PCB from main supply.

Simplicity is the biggest factor for me. Is there a single device/IC that can do this in the correct order? Most sequencing devices I have seen like LM3880 would have work if it had dual in dual out. But there is only one supply input on such a device and the LNA requires two different voltage supplies

The design does not have any microcontroller and therefore cannot have any enable pins/switching devices, etc.

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    \$\begingroup\$ Did you read the application note on single supply configuration? qorvo.com/products/d/da007363 \$\endgroup\$
    – Jack Creasey
    Commented Sep 27, 2021 at 15:19
  • \$\begingroup\$ I didn't see any mention of power sequence in the data sheet. \$\endgroup\$
    – Andy aka
    Commented Sep 27, 2021 at 15:20
  • \$\begingroup\$ The likely danger is having a DC path to the +5V supply through an inductor, so that dangerously-high current can flow. Perhaps a current-limited +5V supply could mitigate the danger of supply sequencing. \$\endgroup\$
    – glen_geek
    Commented Sep 27, 2021 at 16:05
  • \$\begingroup\$ there are power sequencing chips built exactly for this purpose. look on the usual suspects sites (TI, analog, infineon…) \$\endgroup\$
    – Lorenzo Marcantonio
    Commented Oct 5, 2021 at 6:31

1 Answer 1

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The easiest, and common approach is to put a series R, shunt C between the 5V LDO output and the enable pin of the 3V LDO to provide a turn on delay. This means you need to select a 3V LDO with an enable pin.

Test thoroughly before hooking your LNA up!

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  • \$\begingroup\$ Thought of this as well, however there are many other circuitry connected to the LDO supplies, so having it not being on directly on startup is unfortunately not an option \$\endgroup\$
    – Breakwin
    Commented Sep 27, 2021 at 15:31

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