BelaSigna 200
Table 2: Non-Critical Signal
Pin Name
CAP0, CAP1
DEBUG_TX, DEBUG_RX
TWSS_SDA, TWSS_CLK
GPIO[14..0]
GPIO[15]
UART_RX, UART_TX
PCM_FRAME, PCM_CLK, PCM_OUT,
PCM_IN
I2S_INA, I2S_IND, I2S_FA, I2S_FD,
I2S_OUTA, I2S_OUTD
DCLK
LSAD[5..0]
SPI_CLK, SPI_CS, SPI_SERI,
SPI_SERO
Description
Internal charge pump - capacitor connection
Debug port
TWSS port
General-purpose I/O
General-purpose I/O
Determines voltage mode during boot. For 1.8V operation,
should be connected to DGND
General-purpose UART
Pulse code modulation port
Philips I²S compatible port
Programmable clock output
Low-speed A/D converters
Serial peripheral interface port
Connect to EEPROM
Routing Guideline
Place 100nF capacitor close to pins
Not critical
Connect to test points
Not critical
Not critical
Not critical
Not critical
Not critical
Not critical
Not critical
If used, keep away from analog
inputs/outputs
Not critical
Not critical
3.3 Audio Inputs
The audio input traces should be as short as possible. The input impedance of each audio input pad (e.g., AI0, AI1, etc.,) is high
(approximately 500kΩ); therefore a 10nF capacitor is sufficient to decouple the DC bias
. Keep audio input traces strictly away from
output traces. Microphone ground terminals should be connected to the AGND plane (if present) or share a trace with the input ground
reference voltage pin (AIR) to the star point.
Analog and digital outputs MUST be kept away from microphone inputs.
3.4 Audio Outputs
The audio output traces should be as short as possible. If the direct digital output is used, the trace length of RCVRx+ and RCVRx-
should be approximately the same to provide matched impedances. If the analog audio output is used, the ground return for the
external power amplifier should share a trace with the output ground reference voltage pin (AOR) to the star point.
The capacitor and the internal resistance form a first-order analog high pass filter whose cutoff frequency can be calculated by f
3dB
(Hz) = 1/(R C 2π), which results with
~30Hz for 10nF capacitor.
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