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PDM Output Pre-Amplifier for Electret Microphones

Sadanori Kato
Guru 36540 points
Other Parts Discussed in Thread: TLV320AIC3262

Hi,

Do you have PDM output pre-amps for electret microphones such as LMV1022, LMV1023, LMV1024 and LMV1026(EOL) ?

Best regards,
Kato

  • 0
    TI__Guru** 110745 points

    HI Kato-san,

    Unfortunately there are not replacement parts for these obsoleted devices.
    You could consider using something like TLV320AIC3262 which supports PDM mic.

    Best regards,
    -Ivan Salazar
    Texas Instruments

  • 0 in reply to Ivan Salazar
    Guru 36540 points

    Ivan-san,

    Thank you for your reply.

    Could TLV320AIC3262 convert the analog input signal to the digital mic data format and output it althought TLV320AIC3262 has the digital mic interface ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Guru** 110745 points

    Hi Kato-san,

    Sorry for the confusion.
    Most of our devices support digital mic, like TLV320AIC3262.
    But you need an analog mic to digital PDM output, I think there is only one device that should be able to do this, the TLV320AIC36.

    Best regards,
    -Ivan Salazar
    Texas Instruments

  • 0 in reply to Ivan Salazar
    Guru 36540 points

    Hi Ivan-san,

    Thank you for your information.
    Could you please explain more information ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Guru** 110745 points

    Hi Kato-san,

    The PDM outs of AIC36 are called DSD in the spec. From system level point of view, this feature is similar to the DIG MIC feature....only difference is that clock and data will both be outputs from the AIC36. The DSD_CLK rate can be programmed to different values, mostly the limiting factor would be the PDM receiver. For DSD, the rate is typically 64*FS, single bit.

    Best regards,
    -Ivan Salazar
    Texas Instruments

  • 0 in reply to Ivan Salazar
    Guru 36540 points

    Hi Ivan-san,

    Thank you for your reply.
    Could you please tell me the registers that I should set to be concrete although I understood that TLV320AIC36 is able to converter the analog signal to PDM output(DSD output) ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Guru** 110745 points

    Hi Kato-san,

    Page 0 Register 124 and Register 125 are control registers for DSD_CLK and DSD_DATA.

    Best regards,
    -Ivan Salazar
    Texas Instruments

    Fullscreen AIC36_DSD.txt Download 
    ###############################################
# Stereo DSD Playback
# ---------------------------------------------
###############################################



###############################################
# Software Reset
###############################################
#
# Select Page 0
w 30 00 00
#
# Assert software reset
w 30 01 01
#
# Release software reset
w 30 01 00
#
###############################################



###############################################
# Power Management Unit Configuration
###############################################
#
# Select Page 2
w 30 00 02
#
# Charge pump uses MCLK, enabled
w 30 71 01
#
# Power for ADC_VDD, DAC_VSS and DAC_VDD LDOs
# 07 -> Power down all
# 00 -> Power up all
w 30 74 00
#
# Current limit for ADC_VDD, DAC_VSS and
# DAC_VDD LDOs
# 07 -> current limit all
# 00 -> do not current limit all
w 30 76 00
#
# DAC_VDD LDO =  1.65 V
# DAC_VSS LDO = -1.65 V
w 30 78 22
#
###############################################



###############################################
# Clock Settings
# ---------------------------------------------
# The codec receives: MCLK = 11.2896 MHz,
# BLCK = 2.8224 MHz, WCLK = 44.1 kHz
###############################################
#
# Select Page 0
w 30 00 00
#
# PLL_clkin = MCLK, codec_clkin = PLL_CLK,
# PLL on, P=1, R=1, J=8, D=0000
w 30 04 08 91 08 00 00
#
# DOSR = 128
w 30 0d 00 80
#
# AOSR = 128
w 30 14 80
#
# NDAC = 2, MDAC = 8, powered on
w 30 0b 82 88
#
# NADC = 2, MADC = 8, powered on
w 30 12 82 88
#
###############################################



###############################################
# Signal Processing Settings
###############################################
#
# Select Page 0
w 30 00 00
#
# PRB_P2 selected for 6 biquads
# PRB_R2 selected for 5 biquads
w 30 3C 02 02
#
# Select Page 8, Enable Adaptive filtering for DAC
w 30 00 08 04
#
###############################################



###############################################
# Playback Configuration
###############################################
#
# Modulator startup sequence
w 30 00 fd
w 30 0d 0d
w 30 04 20
w 30 0d 00
#
# Select Page 0
w 30 00 00
#
# DAC Analog FIR taps (0,3,5,7,9,c)
w 30 72 30
w 30 73 75
w 30 74 c9
#
# DAC channel enabled, L/R I2S -> L/R data
w 30 3F D4
#
# Unmute L/R DAC channels
w 30 40 00
#
# Configure DSD_CLK / DSD_DATA
w 30 7C 3c 3c
#
# Select Page 1
w 30 00 01
#
# Enable LDAC and RDAC bitstream mode
w 30 03 80 80
#
# Select Page 2
w 30 00 02
#
# Power up LDAC, RDAC
w 30 25 c0
#
###############################################

  • 0 in reply to Ivan Salazar
    Guru 36540 points

    Hi Ivan-san,

    Thank you for your information.
    The comment of "Stereo DSD Playback" in this script which you would send to me is mentioned.
    So, is this script supported the stereo recording with PDM format ?
    Could you please give me your advice since I am a little confused ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Guru** 110745 points
    HI Kato-san,

    The script is a configuration for I2S to DSD.
    For the microphone input to DSD (PDM) output the ADC path must be set up. Then the loopback must be used to route the ADC output to the DAC input; the loopback is configured through Page 0/Register 27/D4. The configuration for the DAC could be the same as the script: unmute the DAC channels, configure DSD_CLK/DSD_DATA, enable bitstream mode and power up the DAC channels.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Guru 36540 points

    Hi Ivan-san,

    Thank you for your quick response.
    Could you please share the script which is added the configuration for the microphone input to DSD output to me if possible ?

    Best regards,
    Kato