MSP430FR6047: Query Regarding EVM's Termination Resistor & its significance.

HARSH PALIWAL

Part Number: MSP430FR6047

Tool/software:

Hi,

1.In the above-mentioned Controller EVM two 200-ohm Termination resistors are being used is there any significance of those resistors?

2.Can i Change Resistor as per my need or it is fixed/advised to use 200-ohm resistor for my design please support with evidence or what could go wrong if i change those values.

3.When i tried to probe my ultrasonic sensor which is connected on J8 header of EVM i could see difference in Peak amplitude on Digital Oscilloscope & USS Software just the double value peak voltage i could see in USS Software.

4. USS waveform on DSO terminates with ringing waveform any particular for the same, these ringing waveforms increases with decrease in termination resistor values.

7 months ago

0 Cash Hao11 7 months ago

TI__Mastermind 45635 points

Hi,

1. Limit current.

2. You can change the value on your own design. But it is not recommended to directly remove them.

3. It might caused by the ADC sampling rate is not high enough. But we do not recommend to use a higher ADC sampling rate. Around 4x of the signal frequency is recommend and enough for a typical meter design

4. A higher resistor value helps the ringing decline faster.

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

Hi,
Can you please ellaborate of point number 3.
ADC Sampling rate is set high,still there is mismatch in waveform on Digital Storage Oscillscope & USS software.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

Hi,

How much ADC sampling rate you are setting in your test? Can you share the ADC capture figure and the captures on oscillscope here?

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

0 HARSH PALIWAL 7 months ago in reply to HARSH PALIWAL

Prodigy 180 points

Peak-Peak voltage in DSO doesn't matches with USS software...
Any way to match them so change in my testing setup is needed.

0 HARSH PALIWAL 7 months ago in reply to HARSH PALIWAL

Prodigy 180 points

ADC Sampling rate is 200kHz

0 HARSH PALIWAL 7 months ago in reply to HARSH PALIWAL

Prodigy 180 points

Peak-Peak observed in DSO is 468mV whereas on USS Software just the peak reaches 810mV.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

Hi,

810 is the ADC code( a 12bit ADC, it codes from -2048 to 2047). It is not mean 810mV.

The ADC reference voltage is 755mV. You also need to check the PGA gain setting as well.

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

Hi,
For the Same controller ADC reference voltage was mentioned as

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/1461035/msp430fr6047-mcu018/5607393#5607393

& Can you please clarify how you have calculated 755mV value & relation between PGA Gain setting and internal reference adc voltage.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

The SDHS reference voltage is 755mV. It is not 1.6V from the USS LDO.

Please refer to this example code for more information. https://dev.ti.com/tirex/explore/node?node=A__AI..jj6bIQJU-xFAUGv7IA__msp430ware__IOGqZri__LATEST

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

Hi,
Can you provide me default configuration setting to get desired voltage level.

0 HARSH PALIWAL 7 months ago in reply to HARSH PALIWAL

Prodigy 180 points

Datasheet mention's 1.6V please clarify this too.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

Hi,

In the datasheet, 1.6V is the supply voltage to SDHS. It does not mention reference voltage in the datasheet. And I am telling you, the reference voltage of SDHS is 755mV. There is no doubt on this.

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

Hi,
Thankyou for info.
I have one more Query why do we see decrease in amplitude as we decrease resistance value (change from 200 ohm till 50 ohm).
Please elloborate on the same.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

Hi,

The resister should be in parallel with the transducer. So, the lower the resistance the less current goes into the transducer.

Best regards,

Cash Hao

0 HARSH PALIWAL 7 months ago in reply to Cash Hao11

Prodigy 180 points

hi i didnt get the part as in how R16(200 ohm) comes in parallel with USS sensor so as to reduce current through it?
Please ellaborate on the same.

0 Cash Hao11 7 months ago in reply to HARSH PALIWAL

TI__Mastermind 45635 points

Hi,

I know it is hard to understand it. However, I also do not have the correct document to describes it. But a parallel equivalent model can explain the test result here. So, we can treat it as a parallel here.

Best regards,

Cash Hao

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MSP430FR6047: Query Regarding EVM's Termination Resistor & its significance.