TPA6166A2: Question of TPA6166 Measurements of Microphone Amplifier

Hi Sirs,

I got a problem with TPA6166 microphone amplifier measurement which needs BU's help:

(1) Only 250mV full scale input on SLEEVE with CTIA configuration.
(2) Lower Output LEVEL on MOUTN then our expection.


1. Test condition:

TPA6166 EVM with the following I2C initial code:

--------------------------------------------------------------------------------------
#op i2c Addr Data Comment
w 80 1e 19 #Enable Registers 3
w 80 04 08 #Interrupt Mask Register 1
w 80 05 00 #Interrupt Mask Register 2
w 80 07 bb #Left Headphone Volume Register = +2dB
w 80 08 79 #Right Headphone Volume Register = LR Tracking
w 80 09 87 #Microphone/Ground Control = +12dB, 0xc7 for +24dB
w 80 12 01 #Reserved Registers
w 80 13 45 #Reserved Registers
w 80 1a 95 #Jack Detect AC Test Settings
w 80 1e 01 #semi auto mode
w 80 1d 80 #Enable Registers 2
--------------------------------------------------------------------------------------

Inserted dummy load:

TIP to RING2 = 32ohm
RING1 to RING2 = 32ohm
SLEEVE to RING2 = 2.2kohm



TPA6166 EVM detects headsets with 0x19 = 0x81





Applied single-end input signal to SLEEVE, grounded on RING2



The full scale input voltage on RING2 becomes distorted with >250mVrms



Measurement on SLEEVE with 1Vrms input



Reduced input signal to 250mV -> Low distortion at SLEEVE



However, I got only lower output on TPA6166 EVM's MOUTN pin then our expectations. Is there something missing with my test configurations?



VIN (SLEEVE) vs VOUT (MOUTN)

CH1:Mic Gain = 12dB (0x09 = 0x87). Setup Gain = 12dB, Actual Gain = 5.6dB
CH1:Mic Gain = 24dB (0x09 = 0xc7). Setup Gain = 24dB, Actual Gain = 17.4dB



THD+N vs VIN (SLEEVE)

CH1:Mic Gain = 12dB (0x09 = 0x87). Full Scale Input Voltage = 158.5mV
CH1:Mic Gain = 24dB (0x09 = 0xc7). Full Scale Input Voltage = 100.0mV



THD+N vs VOUT (MOUTN)

CH1:Mic Gain = 12dB (0x09 = 0x87). Full Scale Input Voltage = 302.7mV
CH1:Mic Gain = 24dB (0x09 = 0xc7). Full Scale Input Voltage = 747.9mV



The headphones output function is ok. AP sends test signal to TIP and RING1, measured audio quality on HPINL and HPINR  



Thank you and Best regards,

Wayne Chen
03/15/2021