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I'm evaluating the STM6600 on/off controller. My application has a 2-series LiPo battery with a voltage range of 6 to 8.4V, so I need to put a voltage divider before VCC as described in AN3271 (Chapter 12). The calculations for the divider provided in that document tell me I should use 26K and 34K resistors to get the recommended 100uA current through the divider.. However, when I use these values and press the power button, EN doesn't go high (I use an EN active high STM6600), instead VCC goes down from 3.4V to about 2.8V. When I use resistor values 10 times as low (2.6K / 3.4K) it works fine, but this means the standby time of my application becomes ten times as low. What can be the cause of this? I am evaluating on a breadboard with the STM6600 on a DFN to DIP breakout.

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Turned out that the tolerance on the input voltage was too tight, causing an undervoltage detection. Replacing the 26K with a 17K solved the problem. The reason that it worked with 2K6 + 3K4 is that the accuracy is better with lower value divider resistors.

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