MSP430I2021: About Designing Around RST Pins

O.H

Part Number: MSP430I2021

Hi experts,

Circuit around RST using MSP430I2021 is performing unexpected operation due to the effect of noise.

Could you tell me about the following items?
1)Is there an internal circuit for the RST pin of the MSP430I2021?
(It is not a block diagram like the one in the user's guide "Figure 1-1", but rather a circuit for connecting the RST pin to the internal core.)

2)The MSP430I2021 does not have an internal pull-up/down resistor, right?

3)Is it okay to set the pull-up resistance of the following circuit to 100ohms?

Currently, the circuit shown in the figure below is constructed, but when noise is applied, the circuit is reset.

Changing the resistance to 100ohms will not be affected by noise.
(Changing the resistance to 510ohms will be affected by noise.)

Best Regards,
O.H

over 3 years ago

0 zrno soli over 3 years ago

Guru 33653 points

1nF value is recommended due to using TI FET's, but it is to small for dealing with higher noise. Maybe this can help...

0 O.H over 3 years ago in reply to zrno soli

Genius 5350 points

Hi zrno soli,

Thank you for your reply.
I will tell the customer to try increasing the capacity of the capacitor as a countermeasure.

By the way, what is TI's view on 1), 2), and 3)?
I need to answer the customer.

Best Regards,
O.H

0 Eddie LaCost over 3 years ago in reply to O.H

TI__Mastermind 38620 points

Hello O.H,

We don't have an internal circuit diagram available, other than the block diagram in figure 1-1.

I do not believe that the i20xx includes internal pull ups as it is not listed in the datasheet or users guide. Some F5xx devices have internal pull ups and there is a thread discussing this below.

https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/543252?MSP430-RESET-Circuit-issue

Per table 1-3 in the users guide, we recommend the 47k pull up. The thread below has some discussion regarding this as well. The 47k resistor can help filter out some short brownouts.

https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/328821?Pullup-resistor-on-RESET-pin

Has the customer been able to test with a larger capacitor(2.2nF)?

0 O.H over 3 years ago in reply to Eddie LaCost

Genius 5350 points

Hello Eddie,

Thank you for your support.
And I am sorry for the late reply.

I understood that there is no internal circuit diagram and no internal pull-up resistance.

Currently, we are asking our customers to try increasing the capacity of the capacitor and "4. Use recommended reset circuitry to enhance reset pin protection" of 'MSP 430 System ESD Troubleshooting Guide'.

After contacting the above method, there is no update so I will close the thread for now.

Thank you.

Best Regards,
O.H

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MSP430I2021: About Designing Around RST Pins