TAS5342LDDVR datasheet(21/29 Pages) TI

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Mid Z Sequence Compatability

DEVICE PROTECTION SYSTEM

ERROR REPORTING

Use of TAS5342L in High-Modulation-Index

TAS5342L

SLAS558 – 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 TAS5342L is being used with TI PWM

To reduce external component count, an internal

modulators

such

the

TAS5518,

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 TAS5342L is compatable with the Mid Z

sequence of the TAS5086 Modulator. The Mid Z

The TAS5342L contains advanced protection circuitry

Sequence is a series of pulses that is generated by

carefully designed to facilitate system integration and

the modulator. This sequence causes the power

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

stage to slowly enable its outputs as it begins to

permanent failure due to a wide range of fault

switch.

conditions

such

short

circuits,

overload,

overtemperature, and undervoltage. The TAS5342L

By slowly starting the PWM switching, the impulse

responds to a fault by immediately setting the power

response created by the onset of switching is

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

reduced. This impulse response is the acoustic

the SD pin low. In situations other than overload and

artifact that is heard in the output transducers

over-temperature

error

(OTE),

the

device

(loudspeakers) and is commonly termed "click" or

automatically recovers when the fault condition has

"pop".

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

The low acoustic artifact noise of the TAS5342L will

The device will function on errors, as shown in the

be further decreased when used in conjunction with

following table.

the TAS5086 modulator with the Mid Z Sequence

BTL MODE

PBTL MODE

SE MODE

enabled.

Local

The Mid Z sequence is primarily used for the

Error

Turns Off

Error

Turns Off

Error

Turns Off

single-ended output configuration. It facilitates a

"softer" PWM output start after the split cap output

A + B

configuration is charged.

A + B + C

+ D

C + D

The

and

OTW

pins

are

both

active-low,

open-drain

outputs.

Their

function

for

Bootstrap UVP does not shutdown according to the

protection-mode signaling to a PWM controller or

table, it shutsdown the respective halfbridge.

other system-control device.

Any fault resulting in device shutdown is signaled by

Capable Systems

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

the device junction temperature exceeds 125

°C (see

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

the following table).

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

the bootstrap capacitors charged. As an example, if

OTW

DESCRIPTION

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

Overtemperature (OTE) or overload (OLP) or

this setting allows PWM pulse durations down to 10

undervoltage (UVP)

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

Overload (OLP) or undervoltage (UVP)

requirement, is sent to the PWM_X pin and this

Junction temperature higher than 125

°C

low-state pulse time does not allow the bootstrap

(overtemperature warning)

capacitor to stay charged. The TAS5342L device

Junction temperature lower than 125

°C and no

requires limiting the TAS5508 modulation index to

OLP or UVP faults (normal operation)

97.7% to keep the bootstrap capacitor charged under

all signals and loads.

Note that asserting either RESET_AB or RESET_CD

low forces the SD signal high, independent of faults

The TAS5342L contains a bootstrap capacitor under

being present. TI recommends monitoring the OTW

voltage protection circuit (BST_UVP) that monitors

the voltage on the bootstrap capacitors. When the

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TAS5342LDDVR Datasheet(PDF) 21 Page - Texas Instruments

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