Tps62291 Enable pin

Hardware
1

Is the tps62291 enable pin exposed on the e-series to effectively turn off the device and modem?

2

It’s not exposed.

And actually that wouldn’t turn off the modem. The TPS62291 is the 3.3V regulator and the EN pin is tied to VSYS so it is always on.

The modem is connected to VSYS directly, not to 3V3.

On the Boron the EN pin controls a load switch that disconnects both the modem and the 3.3V regulator from VSYS, but that does not exist on Gen 2 devices.

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3

@rickkas7

any word on that “boron proper power down” application note? I think a bunch of us are very curious :wink:

4

It’s in progress. I’m waiting for a revision to the hardware example to come back from fabrication.

While the TPL5010 example is just a straightforward watchdog that’s widely implemented, the AB1805 is much more interesting.

The AB1805 has a bunch of useful features:

  • Programmable watchdog. Also neat because you can adjust the period in software over I2C, for example before doing a software upgrade.
  • Real-time clock. Can both keep time when the Gen 3 device is in HIBERNATE sleep mode, and also do wake interrupts (one-shot and periodic). Only requires a 32 kHz crystal, no capacitors.
  • RTC can be powered by Li+, a coin cell, or a supercap.
  • Deep reset using the EN pin, only requires an N-channel MOSFET and a pull resistor.
  • The AB1805 can also take RST and EN low at the same time, to assure that the MCU resets even if you have current leakage into the MCU.
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