Hi, we are using the STM6600CS25DM6F in one of our new products. It is powered by the output of a battery charger. This charger can draw up to 500mA from a USB port. If the system requires more current, the charger switches to the supplement mode, where the additional current is drawn from the battery. While switching back and forth between those two operating modes, the output at the charger toggles between 4.2V and the actual battery voltage (this is normal behavior). As a result the VCC input of the STM6600CS25DM6F "sees" voltage differences of up to ca. 800mV. The problem is, that the STM6600CS25DM6F cannot handle these sudden voltage changes. As a result it resets the enable output (EN) and consequently the system crashes. In the attached image one can see this behavior. Yellow trace: Voltage at VCC - one can clearly see the voltage drop of approx. 600mV. Red trace: EN signal - shortly after the voltage drop of VCC the signal drops to 0 (the exponential decay is caused by an RC filter). Blue trace: PSHOLD signal.
Here are my questions:
- is this behavior know?
- How can I make sure that the STM6600CS25DM6F does not crash when its input voltage drops or is not stable?
- Shall we connect the VCC input directly with the battery instead of the output of the charger? However, even if we would do so, the battery voltage can as well drop by several hundreds of millivolts, if e.g. large currents are drawn from the battery.
Thanks for your support
Felix
