TMS320F28379D: Questions about ADC reference power supply

Bruce(Shanghai) Liu

Part Number: TMS320F28379D
Other Parts Discussed in Thread: TMDSCNCD28379D, C2000WARE

Hello! Questions on C2000Ware\boards\controlCARDs\TMDSCNCD28379D\R1_3 \F2837x_180controlCARD_R1_3_SCH_02Oct2015.

As we know, REF5030 output current is 10mA and VREFHI per input current is 190uA .So the power output capacity is completely sufficient.

Why do we need a four-way output follower as shown in U13?

over 4 years ago

0 Devin Cottier over 4 years ago

TI__Guru 60865 points

Hi Bruce,

Sorry for the delay.

We have found that the bandwidth of the REF IC is not always sufficient for getting good ADC performance. See:

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/477506/faq-adc-reference-in-tms320f28377dzwt

To evaluate the buffer driving the VREFHI, I'd recommend the TI precision labs training series "Driving the reference input on a SAR ADC": https://training.ti.com/node/1139107

0 Bruce(Shanghai) Liu over 4 years ago in reply to Devin Cottier

TI__Intellectual 1010 points

Hi Devin,

Thanks for your reply. Through the link, I think that adding a buffer has the following two advantages: one is to reduce the output impedance of the previous circuit, and the other is to increase the circuit bandwidth (instantaneous output current capability). Is my statement correct?

0 Devin Cottier over 4 years ago in reply to Bruce(Shanghai) Liu

TI__Guru 60865 points

Hi Bruce,

That's correct. Independent buffering also isolates one ADC from causing a noise on another ADC's reference.

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TMS320F28379D: Questions about ADC reference power supply