HL7812 – Unexpected periodic current spikes in KSLEEP (Lite-Hibernate)

IoT Modules HL78
1

Hello,

I am currently working on low-power optimization with the HL7812, and I am observing unexpected behavior when using the internal sleep mode (KSLEEP).

Context

  • Modem: HL7812
  • Custom hardware with MCU

Test setup

Here is the minimal sequence i tested:

  1. Set modem to airplane mode: AT+CFUN=4

  2. Disable power saving features:
    AT+CPSMS=0
    AT+CEDRXS=0

  3. Enable sleep: AT+KSLEEP=1,1,5

  4. Release WAKEUP pin

Expected behavior

The modem should enter a stable low-power state (Lite-Hibernate) with a flat current consumption.

ppk-1
ppk-13450×1947 142 KB

Observed behavior

I tested this on several of boards:

  • 1 boards: expected behavior
  • 2 boards: periodic current spikes

ppk-2
ppk-23450×1947 205 KB

  • 2 boards: repeating patterns with a dependency on the KSLEEP delay parameter (e.g. changing from 2s to 5s modifies the pattern timing)

ppk-3(5s)
ppk-3(5s)3450×1947 181 KB

ppk-3(2s)
ppk-3(2s)3450×1947 184 KB

The issue appears only on our custom boards.

Tests performed

  • Firmware update (modem)
  • Factory reset
  • Direct control of the HL module via USB (bypassing MCU)
  • Increased delays between AT commands
  • WAKEUP signal verified at hardware level

Question

I am not looking to review the hardware design or validate the integration with the HL7812, as it has already been verified and behaves correctly in other configurations.

Has anyone experienced similar periodic current patterns or spikes when using KSLEEP / Lite-Hibernate mode on the HL7812?
If so, under which conditions or configurations did it occur?

2

you can take a look on this application note:

In table 2, it shows the wake up source is active RTC timer timeout event or UART1_DTR.

BTW, are you able to reproduce this in dev kit?