TAS2780 datasheet(28/97 Pages) TI

28 / 97 page

8.4.5 Post Filter Feed-Back (PFFB)

The device supports post-filter feedback by closing the amplifier feedback loop after the external filter. The

feedback is applied using the VSNS_N and VSNS_P terminals of the device. This feature can be disabled using

the PFFB_EN register bit, for instance if an external filter that violates the amplifier loop stability is implemented.

When PFFB is disabled, the feedback will be internally routed from the OUT_N and OUT_P pins of the device.

In the PFFB mode of operation the following conditions have to be met by the external filter: f0>10MHz and

f0/Q>2.5MHz (f0 and Q are the cutoff frequency and the quality factor of the external filter).

8.4.6 Load Diagnostics

The TAS2780 can check the speaker terminal for open or short. This can be used to verify the continuity of the

speaker or the traces to the speaker. The entire operation is performed by the TAS2780 and result is reported

using the IRQZ pin or by reading over I2C bus on completion. The load diagnostics can be performed using

external audio clock (register bit LDG_CLK=0) or the internal oscillator (LDG_CLK=1).

The speaker open (upper - UT) and short (lower - LT) thresholds are configured using the LDG_RES_UT[31:0]

and LDG_RES_LT[31:0] register bits. The diagnostic is run by selecting one of the load diagnostic modes

set by MODE[2:0] register bits. The load diagnostic can be run before transitioning to active mode or stand-

alone returning to software shutdown when complete. When the load diagnostics is run it will play a 22

kHz at -35 dBFS for 100 ms and measure the resistance of the speaker trace. The result is averaged over

the time specified by the LDG_AVG[1:0] register bits. The measured speaker impedance can be read from

LDS_RES_VAL[31:0] register bits.

8.4.7 Thermal Foldback

The TAS2780 monitors the die temperature and can automatically limit the audio signal when the die

temperature reaches a set threshold. It is recommended to use the thermal fold-back registers to configure

this protection mechanism as the internal DSP will perform the necessary calculation for each register.

Thermal fold-back can be disabled using TFB_EN register bit. If the die temperature reaches the value set by

TF_TEMP_TH[31:0] register bits this feature will begin to attenuate the audio signal to prevent the device from

shutting down due to over-temperature. It will attenuate the audio signal by a value set in TF_LIMS[31:0] register

bits over a range of temperature set by TF_TEMP_TH[31:0] register bits. The thermal fold-back attack is at

a fixed rate of 0.25dB/ms. A maximum attenuation can be specified using register bits TF_MAX_ATTN[31:0].

However, if the device continues to heat up, eventually the over-temperature will be triggered. The attenuation

will be held for a number of samples set by register bits TF_HOLD_CNT[31:0], before the attenuation will begin

releasing.

8.4.8 Over Power Protection

The TAS2780 monitors the temperature of the internal power FETs. If the maximum continue power is high and

power FETs temperature goes above a threshold, an internal protection circuit will trigger a thermal fold-back

and, if temperature still increases, shutdown the device.

The protection mechanism is based on two thresholds TH1 and TH2. The TH1 threshold is set at a temperature

1160C higher than the temperature measured by the internal bandgap but not less than 2500C. The TH1

threshold triggers a thermal foldback.

The TH2 threshold is 400 C above TH1 and triggers thermal shutdown.

The two detection mechanisms can be disabled by setting bits TG_TH2 and TG_TH1 of register 0x47, page

0x01 to low.

8.4.9 Low Battery Protection

For VBAT1S supply below 3.4 V the power FETs can go into saturation at higher load currents which could result

in device damage due to the FETs connected to PVDD going into thermal runaway.

TAS2780

SLOSE75A – FEBRUARY 2022 – REVISED JUNE 2022

www.ti.com

Submit Document Feedback

Product Folder Links: TAS2780

TAS2780 Datasheet(PDF) 28 Page - Texas Instruments

TAS2780 Datasheet(HTML) 28 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97

Datasheet Download

Link URL