L96 doesn't full on after Vcc power restart

Hello. I have a working device used L96 (5.1.8) as GNSS. Vcc and V_Bckp pins are both connected to 3v3 LDO with EN.

Question 1:
How long I should wait after power on before sending first PMKT configuration command via UART?

After 3v3 on by EN of LDO I send $PMTK225,4*2F to enter into backup mode. The GNSS successfully eneres to backup. Than I disable 3v3 power on Vcc and V_bckp pins by pulling down (low level) EN of LDO for 700 ms and than recover the power (EN to high level). I saw (on oscilloscope) that the voltage falls to 0v, waits 700 ms and rises up 3v3 again. After that L96 doesn’t send to my MCU any data via UART. At that state (power on) I tried to send 100-200-500-800-1000 ms high level impulses on FORCE_ON pin, but the GNSS did not start sending any data on UART.

If I power off L96 for more than about 1.5 sec everything is ok: the module starts sending UART data as described in manuals.

Question 2: Is here minimum timeout between power loss and power recover?

I have never seen description about that behaviour.
Please, advise me.

Hi Ildar Belkin,

  1. I suggest you to power up VBCKP no later than VCC.

  2. There is no minimum timeout between power down and power on. I would like to suggest you follow this sequence.

Best regards.