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Generic Node Sensor Edition
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Voltage supervisor behavior at low Vin #123

Closed azerimaker closed 3 years ago

azerimaker commented 3 years ago

Summary:

After testing with different battery types and the bench supply the voltage supervisor IC sometimes behaves erratically, resulting in disabling the buck-boost converter and going into oscillation mode. This maybe due to the location of its sense (Vin) line, which is right after the decoupling caps.

Current problem:

It sometimes causes unwanted latching and oscillations around 2.4V input levels.

How do you propose to implement this?

First method I tried was to remove the sense line and tap it directly from the output pin of the fuse. This improved the stability little bit, but the result still was not satisfactory. In the next revision we might consider replacing it with the 1.67V variant (TPS3839G18).

Proposition Considering the added cost, introduced instability in certain Vin ranges of a voltage supervisor IC we might offer this functionality as optional with a jumper resistor added across it. Moreover the main buck-boost converter already has a built-in Undervoltage Lockout (UVLO) Circuit which disables the device at around 1.5V input.

UVLO

azerimaker commented 3 years ago

In the next revision (v1.1b) we have replaced the voltage supervisor with the 1.67V variant (TPS3839G18). I'll reopen this issue if this behavior persists.