TAS2780 datasheet(20/96 Pages) TI

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Figure 8-4. Low Voltage Signaling

The LVS fixed thresholds, when CDS_MODE[1:0]=11 (PWR_MODE2 from Section 11.1), can be set using

should be set with register bits LVS_FTH[4:0].

Below equations show the maximum level of the input signal in order to keep LVS below threshold (Class D

switching on VBAT1S).

For absolute threshold: .

Input (dBFS) < LVS_FTH + (21 dBV - ChannelGain [dBV]) (1)

For relative threshold: .

Input (dBFS) < 20log[(VBAT1S*CD_EFF - LVS_RTH)/16] + (21 dBV - ChannelGain [dBV]) - 1.5dB (2)

Where:

* ChannelGain = AMP_LEVEL + DVC_LVL + SAFE_MODE (if enabled, it is -18dB).

* CD_EFF is set by registers 48h-4Bh from page 0x04 and LVH_RTH is set by bits [3:0] of register 6Ah from

page 0x00.

* 1.5dB is an inflection factor, already included for absolute threshold.

BOP, Limiter, Thermal Foldback and Thermal Gradient Gain Attenuation should not be taken into account for

calculating LV_EN threshold.

8.4.2.6 Y-Bridge

The TAS2780 Class-D output uses a Y-Bridge configuration to improve efficiency during playback. The LVS

(Section 8.4.2.5) is internally used to select between the PVDD and VBAT1S supplies. This feature is enabled by

setting CDS_MODE[1:0] bits to 2'b00 when both PVDD and VBAT1S are supplied to the device. If not configured

to Y-bridge mode the device will use only the selected supply for class-D output even if clipping would otherwise

occur. The device can operate using only PVDD to supply class-D output. In this configuration the VBAT1S

can be provided from external supply (register bit VBAT1S=0) or generated by an internal LDO (register bit

VBAT1S=1). In this case CDS_MODE[1:0] bits should be set to 2'b10. The TAS2780 Y-Bridge with Low Power

on VBAT1S can be used to switch to the VBAT1S rail only at very low power when close to idle. This will

reduce the class-D output swing when near idle and limit the current requirements of the VBAT1S supply. Set the

CDS_MODE[1:0] register to 2'b11 for this mode.

See Section 11.1 for details on programming the power mode of operation.

TAS2780

SLOSE75 – NOVEMBER 2021

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TAS2780 Datasheet(PDF) 20 Page - Texas Instruments