TMS320F280040C-Q1: Pin35 GPIO control ISSUE

CHO SR

Expert 2915 points

Part Number: TMS320F280040C-Q1
Other Parts Discussed in Thread: LM5160

Hi,

The customer is using a 35 pin GPIO to control the STB on CAN.

When the MCU STB signal is output to Low, the STB signal remains low and the LM5160 is off.

However, after 200us, the STB signal changes back to High, causing the LM5160 to turn ON.

LM5160 test.pptx

As a result of further verification, the XRSn pin becomes low and the STB changes to high.

Is there any way to keep the STB low?

1. Yellow - nSTB(35 pin)

2. Green - LDO Vin 4.5V

3. Purple - MCU VCC3.3V

4. Blue - MCU XRSn

over 2 years ago

0 Vivek Singh over 2 years ago

TI__Guru** 109065 points

Hi,

On reset, GPIO pins are tri-stated hence you are seeing this behavior. If you need to drive pins low during reset, you need to have pull-down on the board.

Regards,

Vivek Singh

0 CHO SR over 2 years ago in reply to Vivek Singh

Expert 2915 points

Hi Vivek,

Thank you for your support.

The customer added 10Kohm pulldown resistance to the STB GPIO signal.

However, STB GPIO has a high output setting, but it is not GPIO control due to pulldown.

0 Vivek Singh over 2 years ago in reply to CHO SR

TI__Guru** 109065 points

Cho,

10K is weak pull so I am surprised that active driver is not able to overcome it. In such case you can try increasing the resistance value further.

Regards,

Vivek Singh

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F280040C-Q1: Pin35 GPIO control ISSUE