TDA8928ST datasheet(6/23 Pages) PHILIPS

6 / 23 page

2004 May 05

Philips Semiconductors

Preliminary speciﬁcation

Power stage 2 x 10 or 1 x 20 W class-D

audio ampliﬁer

TDA8928J

FUNCTIONAL DESCRIPTION

The TDA8928J is a two-channel audio power amplifier

system using class-D technology.

The power stage TDA8928J is used for driving the

loudspeaker load. It performs a level shift from the

low-power digital PWM signal, at logic levels, to a

high-power PWM signal that switches between the main

supply lines. A 2nd-order low-pass filter converts the PWM

signal into an analog audio signal across the loudspeaker.

8.1

Power stage

The power stage contains high-power DMOS switches,

drivers, timing and handshaking between the power

switches and some control logic (see Fig.1).

The following functions are available:

• Switch (pins SW1 and SW2): digital inputs; switching

from VSS to VSS + 12 V and driving the power DMOS

switches

• Release (pins REL1 and REL2): digital outputs;

switching from VSS to VSS + 12 V; follow pin SW1 and

SW2 with a small delay. Note: for self oscillating

applications this pin is not used

• Power-up (pin POWERUP): must be connected to a

continuous supply voltage of at least VSS + 5 V with

respect to VSS

• Enable (pins EN1 and EN2): digital inputs; at a level of

VSS the power DMOS switches are open and the PWM

outputs are floating; at a level of VSS + 12 V the power

stage is operational

• Diagnostics (pin DIAG): digital open-drain output; pulled

down to VSS if the maximum temperature or maximum

current is exceeded.

8.2

Protection

Temperature and short-circuit protection sensors are

included in the TDA8928J. The diagnostic output is pulled

down to VSS in the event that the maximum current or

maximum temperature is exceeded. The system shuts

itself down when pin DIAG is connected to pins EN1 and

EN2.

8.2.1

MAXIMUM TEMPERATURE

Pin DIAG becomes LOW if the junction temperature (Tj)

exceeds 150

°C. Pin DIAG becomes HIGH again if Tj is

dropped to approximately 130

°C, so there is a hysteresis

of approximately 20

°C.

8.2.2

MAXIMUM CURRENT

When the loudspeaker terminals are short-circuited this

will be detected by the current protection. Pin DIAG

becomes LOW if the output current exceeds the maximum

output current of 2 A. Pin DIAG becomes HIGH again if the

output current drops below 2 A. The output current is

limited at the maximum current detection level when pin

DIAG is connected to pins EN1 and EN2.

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