We are currently upgrading some of our legacy products that use the Colibri VF50 to the Verdin AM62.
During our testing, we encountered a behavior that we would like to clarify.
Our devices are battery-powered and designed to provide a regulated 5V output. However, as the battery discharges, the output voltage begins to drop below 5V. Under these conditions, we observe the following:
The SOM continues to operate normally
The onboard Wi-Fi module (used in AP mode) starts to behave erratically
After some time, the Wi-Fi SSID disappears completely from the network list
Despite this, the SOM itself appears to keep running without interruption
We have not yet precisely measured the voltage thresholds at which this occurs, but we have observed consistent behavior across multiple low-battery scenarios.
Our questions are:
Does the Verdin family include a brownout reset (BOR) or similar protection mechanism that forces the system into reset when the supply voltage drops below a certain level?
If such a feature exists, is the threshold configurable?
If not, what is the minimum operating voltage of the AM62 across its full temperature range?
If the minimum voltage requirements differ between the SOM and the Wi-Fi module, what is the minimum required voltage specifically for the Wi-Fi module?
Your observation about Wi-Fi dropping before the SoM itself fails is consistent with a known issue documented in the Verdin AM62 Errata. The MAYA-W1 Wi-Fi module has stricter voltage requirements than the main SoM (2):
MAYA-W1 Wi-Fi module maximum input voltage: 4.2V (absolute maximum rating) (2)
Issue affects: Verdin AM62 V1.0 and V1.1 modules with Wi-Fi/Bluetooth (2)
The errata specifically states: “The MAYA-W1 Wi-Fi module can experience reduced reliability and possible damage to internal components if the Verdin AM62 V1.1 VCC is powered with 4.2V or higher” (2).
Brownout Protection
The documentation indicates that the SoM uses a TPS65219 PMIC with switched and linear converters (1). However, the specific brownout reset (BOR) thresholds and configurability are not detailed in the available documentation.
Power Management Features
The Verdin AM62 includes several power management signals (1):
CTRL_FORCE_OFF_MOCI#: Output for forcing the turning-off of the main power rail (1)
CTRL_PWR_EN_MOCI: Enable signal for carrier board peripherals power rails (1)
CTRL_SLEEP_MOCI#: Enable signal for power rails that need to be turned off during sleep mode (1)
Recommendations
For V1.1 modules: Ensure your regulated output doesn’t drop below 4.2V to maintain Wi-Fi reliability (2)
Consider upgrading: Verdin AM62 V1.2 modules power the MAYA-W1 from a regulated 3.3V rail and are not affected by this voltage limitation (2)
Monitor voltage levels: Implement voltage monitoring in your battery management system to prevent operation below safe thresholds
The behavior you’re observing—Wi-Fi dropping while the SoM continues operating—aligns with the documented voltage sensitivity of the Wi-Fi module compared to the main processor.
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Which version of Verdin AM62 and what carrier board do you have?
The Verdin family does not include a brownout reset, however, if you really need to implement it, you could do so by measuring the VCC rail and asserting the CTRL_RESET_MICO signal when the VCC drops below a certain level.
The Verdin module is specified to operate from VCC = 3.135 V to 5.5 V. This is the guaranteed operating range for the module input supply. You can see this on the Verdin AM62 datasheet under recommended operating conditions: VCC min. 3.135 V, typ. 3.3 V or 5 V, max. 5.5 V. Once VCC drops below 3.135 V, the module is outside its specified operating range. Behavior below this voltage is not guaranteed. It is possible that some parts of the system continue operating while others become unstable first.
For the Wi-Fi/BT part specifically, the Verdin AM62 WB variant uses an on-module **u-blox MAYA-W160-00B** Wi-Fi/Bluetooth module. The minimum operating voltage for this module is 2.8V.
So if your battery-supplied voltage drops below this voltage, the wifi module could shut down. However, this is a tricky situation because under 3.135V, I would expect the SoM to shut down. Could you please measure the voltage and let us know at what voltage level this behavior happens?
@rudhi.tx, are you sure this is the case? I hope Verdin and others include at least CPU internal brownout reset. Without it, big chances are, erratic CPU behavior below VCC min threshold may lead to erratic data write to flash storage. I believe it is very serious issue.
Since you asked this question, I checked with our hardware team to understand how we implement this minimum voltage threshold for the SoC. As you see in the datasheet, the minimum operating voltage is 3.135V for the SoC. Our hardware team did some theoretical calculations on different losses, and thereby, a theoretical calculation for the minimum input voltage. From these calculations, the typical threshold on the SoC is set to 2.91V, and the worst case threshold to 3.127V. See the image below:
As I mentioned earlier, this calculation is based on some theoretical values for the static losses, path resistance values for the 3.3V buck converter, SODIMM, and traces.
@Fide, could you measure both the VCC (input voltage) and also the input voltage to the WiFi module? It can be measured on TP25:
