TPA3251: Unused channel and input level offset

Prodigy 20 points

Replies: 1

Views: 9

Part Number: TPA3251


Q1) How should I treat an unused channel? Should the inputs be connected via a small capacitor (e.g. 0.1 uF) to ground? And the outputs connected to BST via a 33 nF capacitor (but NO other connection)?

Q2) When measuring the DC voltage on INPUT_x (pins 5, 6, 16 and 17) of TI eval board I am measuring ~ 6VDC but on my prototype board, I am measuring 3.9 VDC. Is this normal? VDD on my proto is at 12VDC.(and internally generated AVDD and DVDD are fine). Note that the output is centered at PVDD/2 (i.e. 17.5 VDC) as expected but wondering whether this may have an impact on distortion when I will apply an high amplitude signal.

Thank you in advance for your help!


1 Reply

  • Hi Louis,

    Q1) I would recommend using a 10uF input capacitor cap to ground. And yes the system requires outputs connected to BST via a 33nF capacitor. You won't need any other connections on the unused channels. 

    Q2) This is strange. The input bias point in our devices should be about 3.9 V if I'm remembering correctly. That way you are able to get the full voltage signal through without any clipping! Did you have any issues playing audio through the EVM? Was the EVM and your prototype setup in the same configurations? 


    Robert Clifton