TAS6424E-Q1: Sub: Short to load channel fault not detected while preforming the DC diag with tas642x amp

Puneet,

To debug the issue, you can set the threshold to a higher value.  This must be shorted before the load diagnostics is run.

Regards,
Gregg Scott

Hi Gregg,
thanks for your reply.

1.We tested different threshold value S2L for register(address:0x0A and 0x0B). Currently diffault value set but we tested with 0.5 and 1.5 ohm but same result are getting.
2. Same DC diag cycle all the three(S2G,S2P and OL) fault is detected correctly but S2L is not detected.
3. We are following below DC diag configuration.

(In DTHE project we are using 2 AMP with I2C address of 0xD4 and 0xD6)

A. Set all the channel in Hi-Z mode.
     w 0xD4 0x0F 0x55 # set all the channel in HI-Z mode.
     w 0xD6 0x0F 0x55 # set all the channel in HI-Z mode/

B. Set the channel in DC- Diag state
    w 0xD4 0x0F 0xFF # set all the channel in DC diag mode
    w 0xD6 0x0F 0xFF # set all the channel in DC diag mode/

C. Read the register DC completed and channel should be in Hi-z mode.
     r 0xD4 0x0F # Read the register for channels should be Hi-z mode
     r 0xD6 0x0F # Read the register for channels should be Hi-z mode

D. Read Faults for S2L, OL, S2Batt, S2GND.
     r 0xD4 0x0C
     r 0xD4 0x0D
     r 0xD6 0x0C
     r 0xD6 0x0D

one more question, what I should consider if impedance value fall in-between short to load(1ohm to 2 ohm) and actual load impedance(my speaker impedance is of 4 ohm)? Means if impedance is 3 ohm what I should consider it.?

Puneet,

Are you shorting the load after step A and before Step B?  I wanted you to test the SL with a higher value to see if it will trip.  You can go as high at 5 ohms.  It should sense your 4 ohms speaker as a short.  First, we determine that the SL will trip.  If it trips, then why doesn't work at lower values.  If it doesn't trip, then we need to understand the test methodology.

The SL threshold is the value where a short is detected.  Any resistance below the threshold will trip the SL DC diagnostics.

Regards,
Gregg Scott

Hi Gregg,

Are you shorting the load after step A and before Step B? In step B also shorted(Keeping long shorted).
 We observed shorted fault detected but not always, And issue observed on subwoofer channels where configured in line drive mode.

Please its little bit urgent. Let me know if we have to do any changes for configuration side.

Regards,
 Puneet

Hi Puneet

 Your testing method should be no problem. Perhaps the problem related with your system level set up.

Puneet Sahu said:

And issue observed on subwoofer channels where configured in line drive mode.

Is the problem only happened on this channel? If testing with some resistor load, the problem would be gone?

If so, maybe I could quickly check your schematic, and the line driver connection. Please kindly share it, and mark on it, which position do you short the load? 

Hi Shadow,

Is the problem only happened on this channel? -->Issue observed on other channel also but Subwoofer channel issue is very frequent.
If testing with some resistor load, the problem would be gone? Problem observed with register load.




-------->>>>below point we short the load.
SUBW_LINE_OUT+
SUBW_LINE_OUT-

Regards,
Puneet

Hi Puneet

Seems everything is fine. Only one possibility, is your short to ground position, have too much resistance to the silicon GND. Could check if your PCB cut the ground into several different region, and only have week connection between them. 

Could use multimeter to test directly, after you create short to ground, from silicon GND pin to the OUT pin, how much resistance would be.

Hi Shadow,

I checked short to load scenario and its impedance is 0.5 ohm to 0.7 ohm getting in multiple power cycle.

Regards,
Puneet

Hi Puneet

I use EVM checked your using condition.

I tested with a 0.7ohm load directly, together with cable and connector, the total resistance may more close to 1ohm.

By using default 1ohm SL threshold, indeed would similar with your side results, SL would sometimes report, but sometimes not.

And increase threshold to 1.5ohm in register 0xA and 0xB, I tried several times, all would correctly report SL.

Hi Shadow,

I have checked with 1.5ohm in register 0xA and 0xB but still same issue observed.
I checked shorted load value through multimeter and its indicated 0.6 ohm.

Regards,
Puneet.