Specifications

AUDIO_IN_P_RIGHT and AUDIO_IN_N_RIGHT

Right channel audio inputs. This dual audio input can be configured to be either single-

ended or fully differential and programmed for either microphone or line input. Route

differential pairs close to each other and use a solid dedicated audio ground plane for the

audio signals.

Audio inputs are sensitive to ESD strikes and thus it is recommended to use ESD clamping

diodes at the audio input terminals. Audio signals internal to WT32 use 1.5 V supply and

thus a voltage divider has to be placed to create 1.5 V reference for the ESD clamping

diodes. A capacitor placed next to the voltage divider will short high frequency ESD strikes

to a solid ground plane and thus prevent damage to the module. The voltage divider can

be common for all audio input signals and the capacitor should be placed as close to the

diodes as possible.

Audio_In_xxx

BAT54S or equivalent

VDD

DGND

1V5

Figure 4: Recommended input implementation for audio

AUDIO_IN_P_LEFT and AUDIO_IN_N_LEFT

Left channel audio input. ESD protection and layout considerations similar to right channel

audio should be used.

AUDIO_OUT_P_RIGHT and AUDIO_OUT_N_RIGHT

Right channel audio output. The audio output lines should be routed differentially to either

the speakers or to the output amplifier, depending on whether or not a single-ended signal

is required. Use low impedance ground plane dedicated for the audio signals.

AUDIO_OUT_P_LEFT and AUDIO_OUT_N_LEFT

Left channel audio output. The same guidelines apply to this section as discussed

previously.

MIC_BIAS

Bias voltage output for a microphone. Use the same layout guidelines as discussed

previously with other audio signals.

LED0

WT32 includes a pad dedicated to driving LED indicators. This terminal may be controlled

by firmware and it can also be set by the battery charger. The terminal is an open-drain

output, so the LED must be connected from a positive supply rail to the pad in series with

a current limiting resistor.