TDF8541THSLASHN2 datasheet(10/54 Pages) NXP

10 / 54 page

TDF8541

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Product data sheet

Rev. 3 — 13 December 2011

10 of 54

NXP Semiconductors

TDF8541

I2C-bus controlled 4

 45 W power amplifier

information, a POR occurs and the amplifier will not restart automatically. In I2C-bus

mode, pin DIAG is pulled LOW to indicate a POR has occurred. In legacy mode, the

amplifier restarts if pin STB remains HIGH.

The device prevents amplifier plops during engine start. To prevent plops on the amplifier

output caused by, for instance, a tuner regulator out of regulation, the voltage on pin STB

can be made zero when an engine start is detected. Pin STB activates the fast mute,

suppressing disturbances at the amplifier inputs.

The built-in low battery voltage mute is the default, and in legacy mode is set to 5.5 V, but

can also be set to 7.2 V via the I2C-bus. If the low battery voltage mute is set to 7.2 V, the

amplifier activates fast mute (400

s) and enters the same cycle when the low V

P mute

was set to 5.5 V: discharge of the ACGND and SVR capacitors when the mute is

completed and start-up when the supply voltage is above 8 V, when no POR has

occurred.

7.3 Power-on reset and supply voltage spikes

If in I2C-bus mode the supply voltage drops below 4.5 V, the content of the I2C-bus latches

cannot be guaranteed and POR is activated at a typical VP level of 3.1 V. All latches are

reset, the amplifier is switched off and pin DIAG is pulled LOW to indicate that a POR has

occurred; see DB2[D7]. If IB1[D0] is set, the power-on flag is reset, pin DIAG is released

and the amplifier starts. In legacy mode a supply voltage drop below 6 V switches off the

amplifier. When the supply voltage is above 6 V the amplifier restarts if pin STB is still

enabled.

7.4 Protection

7.4.1 Output protection and short-circuit protection

If a short-circuit to ground, to VP or across the load occurs on one or more amplifier

outputs, only the channel with the short will be switched off. The channel that has a

short-circuit and the type of short-circuit can be read via the I2C-bus. If pin DIAG is

enabled for load fault information (IB2[D4] = 0) pin DIAG is pulled LOW. The window

protection prevents a restart of the channel with a short to ground or VP. With a short

across the load the channel is switched on again after 15 ms to check if the short across

the load is still present. If the short-circuit conditions are still present, the channel is

Fig 6.

Engine start protection

amplifier re-start

(depends on

I2C-bus content)

t (s)

001aam687

voltage

(V)

3.5

UVP

DC output voltage

SVR voltage/DC input voltage

t(start-Vo(off))

t(start-SVRoff)

DC voltage output

not filtered to ensure

headroom

SVR clamp voltage

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