Problem with working on 2.5V

[Artem Dmitriev]

Posted on March 01, 2018 at 11:10

Hello!

On the PCB from LDO(

MCP1700T-3302E

) 3.3V are supplied 2 chips:

GPS

:

SIM

68

M,

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?

Note: this post was migrated and contained many threaded conversations, some content may be missing.

[Dvorak.Peter]

Posted on March 06, 2018 at 13:36

Replacing your GPS power switch with the following device will reduce your power supply disturbance and solve all your problems

The TI TPS2051B power-distribution switches are 

intended for applications where heavy capacitiveloads and short circuits are likely to be encountered.These devices incorporates 70-mΩ N-channelMOSFET power switches for power-distributionsystems that require multiple power switches in asingle package. Each switch is controlled by a logicenable input. Gate drive is provided by an internalcharge pump designed to control the power-switchrise times and fall times to minimize current surgesduring switching. The charge pump requires noexternal components and allows operation fromsupplies as low as 2.7 V.