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TPA6404-Q1: AC diagnostics of TPA6404-Q1

Betty Guo
Expert 7300 points
Part Number: TPA6404-Q1

Hi,

the ch1 of TAP6424 connect the load of 6.8uF&4ohm. customer use AC diagbostic, 

set gain =1 I=10mA

read register 0x17 value is 1D, so the Impedance_CH is 29*0.059=1.711ohm.

use Channelx Impedance equlation of 9.3.6.3.3, the Channelx Impedance=1.711*2.371/(1*10)=0.4ohm. But,  With 18.75kHz signal, the actual load impedance is 4.19ohm. there have 10times gap between caluation and actural value.

is there mistake? thanks

  • 0
    TI__Mastermind 19030 points

    Hi Betty,

    Please set to gain=4, 19mA. 

    1. Load impedance detection

    a)      Set AC_DIAGS_LOOPBACK (Reg0x16<7>) =0.

    b)      Apply 0dBFS 19K signal and enable AC load diagnostics (set Reg0x15<3:0> = 1 for CH1 to CH4; Set Reg0x15<3>=1 and Reg0x15<1>=1 for PBTL12 and PBTL34).

    c)       Read back AC_IMP (Reg0x17~Reg0x1A), AC_LDG_PHASE2 (Reg0x1B and Reg0x1C) and STI (Reg0x1D and Reg0x1E).

    Regards, 

    Derek