On the PCB from LDO(MCP1700T-3302E) 3.3V are supplied 2 chips:
GPS: SIM68M, STM32L475RET6.
GPS power supply is controlled by STM. When STM turn on GPS module voltage temporarily drops to 2,5V.
At this time MCU works incorrectly if frequency is 80MHz (hang or HardFault handler are called). If frequency 40Mhz all fine.
What could be the problem?