SGTL5000 MIC BIAS pin

[sylvainbouriot]

Hello, I'm using SGTL5000 codec (QFN20) with micro input.

I have a question about typical application schematic (figure 20 in datasheet).

How must I connect MIC BIAS pin if I use the internal bias resistor?

Internal bias resistor is connected between internal MIC bias voltage and MIC_BIAS pin (pin 11 on 20QFN package). Am I right?

Best Regards.

[xiangjun_rong]

Hi, Sylvain,

I think the MIC_BIAS pin connection circuit is correct. Based on UM of SGTL5000, if you do not use internal resistor to set up the mic bias, you can use the circuit to set up the bias voltage for the MIC.

Pls refer to the section Table 29. CHIP_MIC_CTRL 0x002 in the UM of SGTL5000 which I attached here.

BR

XiangJun rong

[sylvainbouriot]

HI,

In fact, I want to use only internal resistor to setup mic bias (not the external resistor R1 on the typical application schematic (figure 20 in datasheet)).

How must I connect MIC BIAS pin (pin 11 on QFN20) if I use only the internal bias resistor?

Best Regards.

Sylvain

[xiangjun_rong]

Hi, Sylvain,

Regarding the MIC_BIAS pin connection, as you know that the MIC_BIAS is an output pin, the output impedance can be set via firmware, so I think the circuit(connecting a  parallel 1uF capacitor and a serial resistor to the Mic-phone pin) is required. If it is okay to use internal resistor via firmware, you can use a zero resistor for the R1.

Hope it can help you

BR

Xiangjun rong