PCM1690: Design review for DAC Output LPF and Differential to Single End Buffer

Jude Ma

Part Number: PCM1690

Dear TI Engineer,

We are using PCM1690 and applicate the DAC output LPF and differential to single end buffer from the datasheet page 35 (as below).

Taking the above as reference, and considering the OPAMP in our project circuit is single power supply 5V, so the circuit and my questions as below.

Question 1: is the reference voltage (BIAS_G1) connection correct? or the BIAS_G1 net after R9G1 (4.7K) should connect with the node of R1G1 (7.5k) and R11G1 (560R)?
Question 2: it seems that a feedback capacitor 680pF should be added between OPAMP noninverting input and ground, right?
Question 3: is there any other comments on the circuit?

Thanks in advance.

Best regards,

Jude Ma

over 2 years ago

0 Arash Loloee over 2 years ago

TI__Mastermind 25980 points

Hello Jude,

The original schematic does 2 things, Diff to single ended operation and also it acts as an active lowpass filter. It seems the connection you have is not correct.

Please follow the schematic connections shown in data sheet.

You can always simulate you circuit in TINA_TI that is downloadable from ti.com. You can also download the opamps models or built in models in TINA and do a sanity check whenever you are not sure about your connection.

Download TINA- TI

https://www.ti.com/tool/TINA-TI?keyMatch=TINA%20TI

Tina model for opamp

https://www.ti.com/product/OPA2134?keyMatch=OPA2134

Regards,

Arash