SLAU874 October 2022 TPA3223
The TPA3223EVM allows for three oscillator frequency options by external configuration of the FREQ_ADJ pin. The frequency adjust can be used to reduce interference problems while using a radio receiver tuned within the AM band. These values must be chosen so that the nominal and the lower value switching frequencies together results in the fewest cases of interference throughout the AM band. The oscillator frequency can be selected by the value of the FREQ_ADJ resistor connected to GND in Primary mode according to Table 3-12.
FREQ_ADJ (J16) Mode | Resistor Selected to GND or Pullup |
---|---|
Primary MODE | 10 kΩ |
Primary MODE AM1 | 30 kΩ |
Primary MODE AM2 | 49.9 kΩ |
Peripheral MODE | Pullup to 5 V |
Selecting Peripheral Mode configures the OSC_I/O pins as inputs to be synchronized from an external differential clock. In a Primary or Peripheral system, interchannel delay is automatically set up between the switching phases of the audio channels, which can be illustrated by no idle channels switching at the same time. The audio output will not be influenced, but the switch timing is changed to minimize noise coupling between audio channels through the power supply. This configuration will optimize audio performance and result in better operating conditions for the power supply. The inter-channel delay will be set up for a peripheral device depending on the polarity of the OSC_I/O connection such that peripheral mode 1 (secondary) is selected by connecting the OSC_I/O of the Primary device with the OSC_I/O of the peripheral device with the same polarity (+ to + and – to –), while peripheral mode 2 (tertiary) is selected by connecting the OSC_I/Os with the inverse polarity (+ to – and – to +).