R262 datasheet(11/28 Pages) ONSEMI

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BelaSigna R262

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Table 5. NON−CRITICAL SIGNALS

Pin Name

Description

Connection Guidelines

CAP0, CAP1

Internal charge pump −

capacitor connection

Place 100 nF capacitor very close to pins

I2C_SDA, I2C_SCL

I2C port

Keep as short as possible. Place pull−up resistors (10 kW) to VDDO

SWAP_CHAN

Control GPIO

Not critical when used as GPIO

CLOCK_SEL,

BOOT_SEL,

CHAN_SEL and

ALPHA_SEL

Low−speed A/D converters

(Multiplexed with SPI port)

Not critical when used as LSAD

Place resistive divider for hardware configuration of BelaSigna R262

SPI_CLK, SPI_CS,

SPI_SERO,

SPI_SERI

Serial peripheral interface port

(Multiplexed with LSAD and

GPIOs)

Keep away from analog input lines when used as SPI signals

NRESET

Reset

Not critical

Leave unconnected if unused

DEBUG_RX,

DEBUG_TX

Debug Port

Not critical

If possible, connect to test points, otherwise connect DEBUG_RX to VDDO

and leave DEBUG_TX floating

RESERVED

Reserved pin

Leave unconnected or connect to VSSA if PCB routing constraints force it

VBATRCVR

Output driver power supply

If the output driver is being used:

− Place a separate 4.7 mF (min. 2.2 mF) decoupling capacitor close to pin

− Connect positive terminal of capacitor to VBAT & VBATRCVR

− Connect negative terminal of capacitor to VSSRCVR

If the analog outputs or the DMIC output are being used:

− Separate decoupling capacitor on VBATRCVR is not required

− Connect VBATRCVR to VDDA (which has its own decoupling capacitor)

Audio Inputs

The audio input traces should be as short as possible. The

input impedance of each audio input pad (e.g., MIC0, AI1,

MIC2, AI3) is high (approximately 500 k

W with

preamplifiers enabled); therefore a 10 nF capacitor is

sufficient to decouple the DC bias. This capacitor and the

internal resistance form a first−order analog high pass filter

whose cut−off frequency can be calculated by

f3dB (Hz) = 1/(R x C x 2π), which results in ~30 Hz for a

10 nF capacitor. This 10 nF capacitor value applies when the

preamplifier is being used, in other words, when a non−unity

gain is applied to the signals; for MIC0 and MIC2, the

preamplifier is enabled by the ROM−based application.

When the preamplifier is bypassed, the impedance is

reduced; hence, the cut−off frequency of the resulting

high−pass filter could be too high. In such a case, the use of

a 30−40 nF serial capacitor is recommended. In cases where

line−level analog inputs without DC bias are used, the

capacitor may be omitted for transparent bass response.

ON Semiconductor recommends the use of NPO/COG

dielectric for SMT capacitors, as they have demonstrated

better performance compared to other capacitors with X7R

dielectric.

Microphone Power Supply

BelaSigna R262 provides a microphone power supply

(VMIC) and ground (VSSA). In case VMIC cannot be used

because of PCB routing constraints, the power supplies

VREG (1.0 V) or VDDA (2.0 V) can alternatively be used.

Keep audio input traces strictly away from output traces.

Audio outputs must be kept away from microphone inputs

to avoid cross−coupling.

Audio Outputs

The audio output traces should be as short as possible. The

trace length of the two signals should be approximately the

same to provide matched impedances.

Recommendation for Unused Pins

Table 6 shows the connection details for each pin when

they are not used.

Table 6. UNUSED PIN RECOMMENDATIONS

Signal Name

Connection Guidelines

A_OUT0

Do not connect

A_OUT1

Do not connect

AI3/VMIC/LOUT0

Do not connect

AI1/LOUT1

Connect to VSSA

DMIC_OUT

Do not connect

SWAP_CHAN

Do not connect

NRESET

Do not connect

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