BelaSigna 200

Table 2: Non-Critical Signal

Pin Name

Description

Routing Guideline

CAP0, CAP1

Internal charge pump - capacitor connection

Place 100nF capacitor close to pins

DEBUG_TX, DEBUG_RX

Debug port

Not critical

Connect to test points

TWSS_SDA, TWSS_CLK

TWSS port

Not critical

GPIO[14..0]

General-purpose I/O

Not critical

GPIO[15]

General-purpose I/O

Determines voltage mode during boot. For 1.8V operation,

should be connected to DGND

Not critical

UART_RX, UART_TX

General-purpose UART

Not critical

PCM_FRAME, PCM_CLK, PCM_OUT,

PCM_IN

Pulse code modulation port

Not critical

I2S_INA, I2S_IND, I2S_FA, I2S_FD,

I2S_OUTA, I2S_OUTD

Philips I²S compatible port

Not critical

DCLK

Programmable clock output

Not critical

If used, keep away from analog

inputs/outputs

LSAD[5..0]

Low-speed A/D converters

Not critical

SPI_CLK, SPI_CS, SPI_SERI,

SPI_SERO

Serial peripheral interface port

Connect to EEPROM

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 bias1. 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.

~30Hz for 10nF capacitor.

Rev. 16 | Page 6 of 43 | www.onsemi.com