TMS570LS3137: MCU nTRST Pin draws too much current from the system

Eyup SAYIN

Part Number: TMS570LS3137

Hi,

The nTRST connection diagram included in the Hercules development kit is shown in Image-1.

Based on this connection, a connection is made from the 3V3 voltage supply to the MCU nTRST pin through the 4K7 resistor (Image-2). The software load could not be done while there was no change in the current drawn by the MCU.

Then, a direct connection was established with the MCU nTRST pin from the 3V3 voltage supply (Image-3). When current measurement is made between nTRST and 3V3, it is seen that it draws 120mA current. Software loaded successfully despite high current draw.

There is no current value information about the nTRST pin in the MCU datasheet. My question is, what effect does the 120mA seen between the MCU nTRST and the 3V3 voltage source have on MCU health? How can I solve this high current draw problem?

Thanks in advance.

over 4 years ago

+1 QJ Wang over 4 years ago

TI__Guru**** 197036 points

Hi Eyup,

The nTRST should be pulled down through a resistor.

+1 Chester Gillon over 4 years ago

Guru 92251 points

Eyup SAYIN said:
When current measurement is made between nTRST and 3V3, it is seen that it draws 120mA curren

nTRST is an input pin with a fixed fixed 100 µA pulldown. Therefore, as per the following expect the maximum input current to be 195 µA:

If nTRST is drawing 120mA think there is a hardware problem.

Are all the supply voltages within tolerance?

Not sure if something is shorted inside the device, e.g. due to overvoltage / ESD, or if nTRST is trying to power the device through the input clamp diodes.

0 Eyup SAYIN over 4 years ago in reply to QJ Wang

Prodigy 135 points

Hi QJ Wang,

Thank you for your support. I added a resistor as pulldown and now I can install software.

0 Eyup SAYIN over 4 years ago in reply to Chester Gillon

Prodigy 135 points

Hi Chester,

Thank you for your support. I added a resistor as pulldown and now I can install software. Also, when I took your suggestion into account and examined the PCB again, I detected a short circuit on the MCU output pins. The reason for the 120mA excess current seen was revealed. Thanks again.

Arm-based microcontrollers

Arm-based microcontrollers forum

TMS570LS3137: MCU nTRST Pin draws too much current from the system