Verdin Development Board Errata
Toradex AG lEbenaustrasse 10 l 6048 Horw l Switzerland l +41 41 500 48 00 l
Page 16 | 19
`
Errata #10:
HAR-8426 – Signal distortion on the audio codec's "Line In" input
Affected Version:
Verdin Development Board V1.0B
Fixed in:
Verdin Development Board V1.1A
10.1
Customer impact
The audio signals from the "Line In" input (connector X21) are distorted and the amplitudes of the
signals are smaller than intended. There is crosstalk from the "Line In" input (connector X21) to the
"Mic In" input (connector X22).
10.2
Description
The 10k pull-down resistors R135 and R138 connected to the pins 26 and 24 of the audio codec
(IC28) affect the functionality of the device’s internal multiplexers and signal amplifiers. The analog
input pins of the audio codec shift the input DC offset to their internal virtual ground VMID. The
external pull-down resistors are affecting this DC offset, causing the opening of the internal
multiplexer’s analog signal switches and the saturation of the amplifier's outputs. This leads to the
distortion of the "Line In" signals (only the positive polarity parts of the input signals are recorded)
and crosstalk from the "Line In" input to the "Mic In” input.
10.3
Workaround
Remove the pull-down resistors R135 and R138 from the carrier board. This makes the audio
codec’s "Line In" and "Mic In” inputs work properly.
Figure 5. Location of R135 and R138 (top side)
