TAS5152 datasheet(21/26 Pages) TI

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TAS5152

SLES127A − FEBRUARY 2005 − REVISED NOVEMBER 2005

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ERROR REPORTING

The SD and OTW pins are both active-low, open-drain

outputs. Their function is for protection-mode signaling to

a PWM controller or other system-control device.

Any fault resulting in device shutdown is signaled by the

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

device junction temperature exceeds 125

°C (see the

following table).

OTW

DESCRIPTION

Overtemperature (OTE) or overload (OLP) or

undervoltage (UVP)

Overload (OLP) or undervoltage (UVP)

Junction temperature higher than 125

°C

(overtemperature warning)

Junction temperature lower than 125

°C and no

OLP or UVP faults (normal operation)

Note that asserting either RESET_AB or RESET_CD low

forces the SD signal high, independent of faults being

present. TI recommends monitoring the OTW signal using

the system microcontroller and responding to an

overtemperature warning signal by, e.g., turning down the

volume to prevent further heating of the device resulting in

device shutdown (OTE).

To reduce external component count, an internal pullup

resistor to 3.3 V is provided on both SD and OTW outputs.

Level compliance for 5-V logic can be obtained by adding

external pullup resistors to 5 V (see the Electrical

Characteristics section of this data sheet for further

specifications).

DEVICE PROTECTION SYSTEM

TAS5152 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 TAS5152 responds to a fault by immediately setting

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

asserting the SD pin low. In situations other than overload,

the device automatically recovers when the fault condition

has been removed, i.e., the junction temperature has

dropped or the voltage supply has increased. For highest

possible reliability, recovering from an overload fault

requires external reset of the device (see the Device Reset

section of this data sheet) no sooner than 1 second after

the shutdown.

Use of TAS5152 in High-Modulation-Index

Capable Systems

This device requires at least 50 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 20 ns. This

signal, which does not meet the 50-ns requirement, is sent

to the PWM_x pin and this low-state pulse time does not

allow the bootstrap capacitor to stay charged. In this

situation, the low voltage across the bootstrap capacitor

can cause a failure of the high-side MOSFET transistor,

especially when driving a low-impedance load. The

TAS5152 device requires limiting the TAS5508 modulation

index to 96.1% to keep the bootstrap capacitor charged

under all signals and loads.

Therefore, TI strongly recommends using a TI PWM

processor, such as TAS5508 or TAS5086, with the

modulation index set at 96.1% to interface with TAS5152.

Overcurrent (OC) Protection With Current

Limiting and Overload Detection

The device has independent, fast-reacting current

detectors with programmable trip threshold (OC threshold)

on all high-side and low-side power-stage FETs. See the

following table for OC-adjust resistor values. The detector

outputs are closely monitored by two protection systems.

The first protection system controls the power stage in

order to prevent the output current from further increasing,

i.e., it performs a current-limiting function rather than

prematurely shutting down during combinations of

high-level music transients and extreme speaker load

impedance drops. If the high-current situation persists,

i.e., the power stage is being overloaded, a second

protection system triggers a latching shutdown, resulting

in the power stage being set in the high-impedance (Hi-Z)

state. Current limiting and overload protection are

independent for the half-bridges A and B and, respectively,

C and D. That is, if the bridge-tied load between

half-bridges A and B causes an overload fault, only

half-bridges A and B are shut down.

D For the lowest-cost bill of materials in terms

of component selection, the OC threshold

measure should be limited, considering the

power output requirement and minimum

load impedance. Higher-impedance loads

require a lower OC threshold.

D The demodulation-filter inductor must retain

at least 3

µH of inductance at twice the OC

threshold setting.

TAS5152 Datasheet(PDF) 21 Page - Texas Instruments

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