TAS5342DDVRG4 datasheet(21/29 Pages) TI

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Mid Z Sequence Compatability

DEVICE PROTECTION SYSTEM

ERROR REPORTING

Use of TAS5342 in High-Modulation-Index

TAS5342

SLAS557B–SEPTEMBER 2007–REVISED OCTOBER 2007

Characteristics

section of this data sheet). Although

signal using the system microcontroller and

not specifically required, it is a good practice to hold

responding to an overtemperature warning signal by,

RESET_AB and RESET_CD low during power down,

e.g., turning down the volume to prevent further

thus preventing audible artifacts including pops or

heating of the device resulting in device shutdown

clicks.

(OTE).

When the TAS5342 is being used with TI PWM

To reduce external component count, an internal

modulators such as the TAS5518, no special

pullup resistor to 3.3 V is provided on both SD and

attention to the state of RESET_AB and RESET_CD

OTW outputs. Level compliance for 5-V logic can be

is required, provided that the chipset is configured as

obtained by adding external pullup resistors to 5 V

recommended.

(see the Electrical Characteristics section of this data

sheet for further specifications).

The TAS5342 is compatable with the Mid Z sequence

of the TAS5086 Modulator. The Mid Z Sequence is a

The TAS5342 contains advanced protection circuitry

series of pulses that is generated by the modulator.

carefully designed to facilitate system integration and

This sequence causes the power stage to slowly

ease of use, as well as to safeguard the device from

enable its outputs as it begins to switch.

permanent failure due to a wide range of fault

conditions such as short circuits, overload,

By slowly starting the PWM switching, the impulse

overtemperature, and undervoltage. The TAS5342

response created by the onset of switching is

responds to a fault by immediately setting the power

reduced. This impulse response is the acoustic

stage in a high-impedance (Hi-Z) state and asserting

artifact that is heard in the output transducers

the SD pin low. In situations other than overload and

(loudspeakers) and is commonly termed "click" or

over-temperature

error

(OTE),

the

device

"pop".

automatically recovers when the fault condition has

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

The low acoustic artifact noise of the TAS5342 will be

further decreased when used in conjunction with the

The device will function on errors, as shown in the

TAS5086 modulator with the Mid Z Sequence

following table.

enabled.

BTL MODE

PBTL MODE

SE MODE

The Mid Z sequence is primarily used for the

Local

single-ended output configuration. It facilitates a

Error

Turns Off

Error

Turns Off

Error

Turns Off

"softer" PWM output start after the split cap output

configuration is charged.

A + B

A + B + C

+ D

C + D

The SD and OTW pins are both active-low,

open-drain

outputs.

Their

function

for

protection-mode signaling to a PWM controller or

Bootstrap UVP does not shutdown according to the

other system-control device.

table, it shutsdown the respective halfbridge.

Any fault resulting in device shutdown is signaled by

the SD pin going low. Likewise, OTW goes low when

Capable Systems

the device junction temperature exceeds 125°C (see

the following table).

This device requires at least 30 ns of low time on the

output per 384-kHz PWM frame rate in order to keep

OTW

DESCRIPTION

the bootstrap capacitors charged. As an example, if

Overtemperature (OTE) or overload (OLP) or

the modulation index is set to 99.2% in the TAS5508,

undervoltage (UVP)

this setting allows PWM pulse durations down to 10

Overload (OLP) or undervoltage (UVP)

ns. This signal, which does not meet the 30-ns

Junction temperature higher than 125°C

requirement, is sent to the PWM_X pin and this

(overtemperature warning)

low-state pulse time does not allow the bootstrap

Junction temperature lower than 125°C and no

capacitor to stay charged. The TAS5342 device

OLP or UVP faults (normal operation)

requires limiting the TAS5508 modulation index to

97.7% to keep the bootstrap capacitor charged under

Note that asserting either RESET_AB or RESET_CD

all signals and loads.

low forces the SD signal high, independent of faults

being present. TI recommends monitoring the OTW

The TAS5342 contains a bootstrap capacitor under

voltage protection circuit (BST_UVP) that monitors

the voltage on the bootstrap capacitors. When the

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