13

TAS5342A

www.ti.com

SLAS623A – NOVEMBER 2008 – REVISED NOVEMBER 2016

Product Folder Links: TAS5342A

Submit Documentation Feedback

Copyright © 2008–2016, Texas Instruments Incorporated

7.3 Feature Description

7.3.1 Mid Z Sequence Compatibility

The TAS5342A is compatable with the Mid Z sequence of the TAS5086 Modulator. The Mid Z Sequence is a

series of pulses that is generated by the modulator. This sequence causes the power stage to slowly enable its

outputs as it begins to switch.

By slowly starting the PWM switching, the impulse response created by the onset of switching is reduced. This

impulse response is the acoustic artifact that is heard in the output transducers (loudspeakers) and is commonly

termed "click" or "pop".

The low acoustic artifact noise of the TAS5342A will be further decreased when used in conjunction with the

TAS5086 modulator with the Mid Z Sequence enabled.

The Mid Z sequence is primarily used for the single-ended output configuration. It facilitates a "softer" PWM

output start after the split cap output configuration is charged.

7.3.2 Device Protection System

The TAS5342A contains advanced protection circuitry carefully designed to facilitate system integration and ease

of use, as well as to safeguard the device from permanent failure due to a wide range of fault conditions such as

short circuits, overload, overtemperature, and undervoltage. The TAS5342A responds to a fault by immediately

setting the power stage in a high-impedance (Hi-Z) state and asserting the SD pin low. In situations other than

overload and over-temperature error (OTE), the device automatically recovers when the fault condition has been

removed, i.e., the supply voltage has increased.

The device will function on errors, as shown in Table 1.

Table 1. Device Protection

BTL MODE

PBTL MODE

SE MODE

Local Error In

Turns Off

Local Error In

Turns Off

Local Error In

Turns Off

A

A + B

A

A + B + C + D

A

A + B

B

B

B

C

C + D

C

C

C + D

D

D

D

Bootstrap UVP does not shutdown according to the table, it shutsdown the respective halfbridge.

7.3.3 Use Of TAS5342A In High-Modulation-Index Capable Systems

This device requires at least 30 ns of low time on the output per 384-kHz PWM frame rate in order to keep the

bootstrap capacitors charged. As an example, if the modulation index is set to 99.2% in the TAS5508, this setting

allows PWM pulse durations down to 10 ns. This signal, which does not meet the 30-ns requirement, is sent to

the PWM_X pin and this low-state pulse time does not allow the bootstrap capacitor to stay charged. The

TAS5342A device requires limiting the TAS5508 modulation index to 97.7% to keep the bootstrap capacitor

charged under all signals and loads.

The TAS5342A contains a bootstrap capacitor under voltage protection circuit (BST_UVP) that monitors the

voltage on the bootstrap capacitors. When the voltage on the bootstrap capacitors is less than required for

proper control of the High-Side MOSFETs, the device will initiate bootstrap capacitor recharge sequences until

the bootstrap capacitors are properly charged for robust operation. This function may be activated with PWM

pulses less than 30 nS.

Therefore, TI strongly recommends using a TI PWM processor, such as TAS5518, TAS5086 or TAS5508, with

the modulation index set at 97.7% to interface with TAS5342A.