TAS5630B failures

Tom Kritzer

Other Parts Discussed in Thread: TAS5630B

We are running the TAS5630B in a BTL configuration with BD modulation. The circuitry is the same as the reference circuit in the data sheet except the output inductors are 10 uH (instead of 7 uH) and the output capacitors are 0.680 uF (instead of (0.470 uF). It is designed to operate into a 6 Ohm load with a Q=0.70. The supply voltage is 26-37 VDC and the housekeeping supply is 11.7 VDC. Both are well filtered.

We have observed a number of chip failures, where the "ready" line never goes high and it appears that one or more of the output FETs are blown. The circuit has often worked for some period of time (minutes to hours) before the spontaneous failure. The output power has always been quite low (10 Watts/channel or less) and at times with no input signal at all.

We configure the amplifier as a constant voltage amplifier with an autotransformer to step up the voltage from 25 V to 70 V. A high impedance speaker is connected to the autotransformer output. Has anyone observed such failures? Are any circuit topology or component value changes needed to accommodate the autotransformer?

over 11 years ago

0 Matthew Beardsworth over 11 years ago

TI__Genius 9175 points

Hi,

I have asked that a colleague works with you to resolve this issue.

Regards,

Matt

0 user5276421 over 10 years ago

TI__Mastermind 37045 points

Hi, Tom,

Can you share your schematic? I will add you as friend so that you can send it privately. Thanks.

Do you seen any voltage spikes on the PVDD, and output pins. Below is a apps note on spike voltage measurements.

http://www.ti.com/lit/an/slea025a/slea025a.pdf

reg,

Paul.

0 user5276421 over 10 years ago

TI__Mastermind 37045 points

Hi Tom,

The schematics looks ok to me. I did not see anything unusual.

Regarding the chip failures, did those failed IC ever worked and just died after some time of normal operation? Or they never started up at initial power on?

Is the audio source muted before the READY signal goes H?

I can review the layout if you send it to me email. Thanks.

reg,

Paul.

0 Tom Kritzer over 10 years ago

Prodigy 45 points

Paul,

We do not ground the top of the TAS5639B to circuit ground. How critical is this? From my forum reading, this seems to help with pops and clicks, and that's about all. Could we get sufficient charge build-up or whatever to damage the chip?

Tom Kritzer
VP Engineering
Stewart Audio

650.396.2144 direct

650.968.4400 main

From: Tom Kritzer <tkritzer@stewartaudio.com>
To: "AudioAmpsForum@mail.e2e.ti.com" <AudioAmpsForum@mail.e2e.ti.com>
Cc: John Zasio <zasio@pacbell.net>
Sent: Tuesday, October 7, 2014 9:17 AM
Subject: Re: [Audio Amplifiers Forum] TAS5630B failures

Hi Paul,

One failure occurred at turn-on, however there was a short on the PCB, so I discount that one. All other failures occurred after the chip had been operating normally (for at least a while). None of the failures had more that 10 hours on them; most on the order of an hour.

The amplifier chip is held in reset until the "ready" pin goes high. During this time the DSP chip (which delivers the audio) is disabled and "muting transistors" are shorted to ground. (There is a blocking capacitor following the transistors, so the amplifier input pins are allowed to float.) We never have audio applied when the amplifier chip is enabled.

The full sequence is:

- Power Applied

- TAS5630B reset is held low by 10k pull-down

100ms Delay to allow power to stabilize

Approximately 700ms of memory reading and processing

Mute transistors pulled high to cut off audio to TAS5630B

TAS5630B reset pin brought low by MCU

TAS5630B mode pins set by MCU

50ms of delay

TAS5630B reset pin pulled HIGH

MCU waits until TAS5630B's ready pin is HIGH

Delay 50ms

200ms - DSP is brought out of reset and configured

Mute transistors are pulled low to allow audio to pass to TAS5630B

The gerber files for our layout are attached. To help you get oriented, the TAS3630B is located in the upper left side. The 36VDC input connector is at the lower left. Just above the input connector is a 36V --> 12V switching regulator (U17). In the lower right is a 12V --> 5V switching regulator (16). The 5V --> 3.3V and 5V --> 1.8V regulators (U23 and U24) are in the middle of the board to the right, just below the DSP chip (U6).

Best regards,

Tom Kritzer
VP Engineering
Stewart Audio

650.396.2144 direct

650.968.4400 main

[collapse] From: Paul C. Chen <bounce-11868@mail.e2e.ti.com>
To: AudioAmpsForum@mail.e2e.ti.com
Sent: Tuesday, October 7, 2014 8:21 AM
Subject: RE: [Audio Amplifiers Forum] TAS5630B failures

Hi Tom,

The schematics looks ok to me. I did not see anything unusual.

Regarding the chip failures, did those failed IC ever worked and just died after some time of normal operation? Or they never started up at initial power on?

Is the audio source muted before the READY signal goes H?

I can review the layout if you send it to me email. Thanks.

reg,

Paul.

[/collapse]

0 user5276421 over 10 years ago in reply to Tom Kritzer

TI__Mastermind 37045 points

Tom,

1581.Ceramique-ThermCompnd-apps-120507.docx

Thanks for the detail power sequence description. Did the part go through any reliability or short testing before failure? Any pins or ESD diodes damaged after it failed?

Yes, It is important to have the heat sink grounded (see 2nd paragraph of the attached doc). What type of thermal interface material do you use? It is conductive or non-conductive?

Did you send the layout file to my email or e2e PM? I did not find it.....

Maybe via email is easier.

Thanks.

reg,

Paul.

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TAS5630B failures