TMS320F280049C: F280049 chip level questions

Rayna Wang

Hi Expert,

I'd like to confirm the below chip level questions with you. Hope could get your help. Thanks!

1. For the application, F280049 just have two type, Q is for automotive and S is for others. Is that right?

My customer is used for PV inverter, they'd like to know if using S level is OK, and what's the difference about these two types.

2. Just double checked, that if customer could put a capacitor between PGA1_OF and PGA1_GND pins to filter the signal?

I have searched the TRM, the content in Filtered Acquisition Window seems supporting for this function.

Thanks!

Best Regards

Rayna

over 6 years ago

0 MatthewPate over 6 years ago

TI__Guru* 86080 points

Rayna,

Customer can use S device for PV inverter; Q grade has extra qualification for automotive Q100 standard. This is not needed outside the automobile.

For the PGA filter you are correct on the use of a cap for filtering and why we brought out this pin on the device. Please see section 14.9.2 in the TRM http://www.ti.com/lit/sprui33

Best,

Matthew

0 Rayna Wang over 6 years ago in reply to MatthewPate

TI__Expert 3680 points

Hi Matthew,

I got it. Thanks for your clarification!

Best Regards

Rayna

0 Rayna Wang over 6 years ago in reply to MatthewPate

TI__Expert 3680 points

Hi Matthew,

There's another question about PGA module.

As the gain of PGA is 3/6/12/24, however could the gain be "1" to let output voltage follow the input voltage by floating the PGA_GND?

Or it could connect the PGA_GND & PGA_OF pins together to make the gain is 1:1, could it?

Thanks!

Best Regards

Rayna

0 tlee over 6 years ago in reply to Rayna Wang

TI__Guru 62975 points

Rayna,

No, the PGA does not support Gain=1. In order to compensate for this, the smaller packages use hard-wired signal muxing to provide an alternate path to non-PGA ADC channels.

For example, if we look at the analog resource table from the datasheet, you can see that on the 64-pin device, pin 12 provides access to both PGA1_IN and C0. If Gain=1 is desired, use the C0 channel.

-Tommy

0 Rayna Wang over 6 years ago in reply to tlee

TI__Expert 3680 points

Hi Tommy,

Customer requires for high impedance function, which ADC could not achieved.

As your suggestion, PGA could not use for the application that should achieve 1:1 & high impedance, could it?

Thanks!

Best Regards

Rayna

0 tlee over 6 years ago in reply to Rayna Wang

TI__Guru 62975 points

Rayna,

Correct, the PGA should not be used for Gain=1 applications.

The ideal signal conditioning for the ADC is low-impedance and high-bandwidth. However, high-impedance is a relative term. Have you reviewed the ACQPS approximation equations from the F28004x TRM?

We have also added a section in the F2806x TRM for ADC signal conditioning for low-bandwidth signals. The equations will apply to F28004x as well.

-Tommy

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TMS320F280049C: F280049 chip level questions