Clipped sine TCXO clock for STM32G031G8U6
The STM32G031G8U6 in a UFQFPN28 package does not have PF0 / PF1 pins for HSE OSC_IN / OSC_OUT. It does however have OSC_IN on PC14. This is intended for an external CMOS oscillator in bypass mode.
I’m currently in the schematic design stage. My board clock is a clipped-sine TCXO used for other purposes. In some modes, I’d like to use it to clock the STM32. I’m very constrained on cost, power, and board space. The clipped-sine doesn't meet the voltage level requirements for a bypass-mode clock.
Is it possible to configure HSE as if it were a crystal, but instead supply a clipped-sine 0.8 Vpp clock from the TCXO to PC14 OSC_IN? Does the die used in UFQFPN28 even have the HSE oscillator circuit that exists in the 48 pin package?
I would set RCC_CR[HSEBYP] = 0 and RCC_CR[HSEON] = 1. I don’t see any register controlling the OSC_IN alternate function on PC14. STM32CubeIDE doesn't allow this configuration, unsurprisingly, but I would configure the registers directly.
I know others have successfully used clipped-sine injection with the HSE configured for crystal on other MCU families (presumably using the PF0 OSC_IN pin on packages where the HSE was fully supported). Not sure if it will work on the 28-pin package that doesn't support HSE as a crystal oscillator. Any thoughts?