TDF8541THSLASHN2 datasheet(13/54 Pages) NXP

13 / 54 page

TDF8541

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Product data sheet

Rev. 3 — 13 December 2011

13 of 54

NXP Semiconductors

TDF8541

I2C-bus controlled 4

 45 W power amplifier

7.4.5 Thermal pre-warning and thermal protection

If the average junction temperature reaches one of the adjustable levels set via the

I2C-bus, selected with IB3[D4], pre-warning is activated resulting in pin DIAG LOW (if

selected) and can be read via the I2C-bus. The default setting for the thermal pre-warning

is IB3[D4] = 0 setting the warning level at Tj(AV)(pwarn) = 160 C. In legacy mode the

thermal pre-warning is also set at Tj(AV)(pwarn) = 160 C.

If the temperature increases further, the temperature-controlled gain reduction is activated

for all four channels to reduce the output power; see Figure 9. If this does not reduce the

average junction temperature, all four channels are switched off at the absolute maximum

temperature Toff.

7.5 Diagnostics

Diagnostic information can be read via the I2C-bus, but can also be made available at pin

DIAG or pin STB. Pin DIAG indicates information such as POR occurred, low battery, and

high battery; the output load fault information is selectable via the I2C-bus. This

information is seen at pin DIAG as a logical OR. In case of a failure, pin DIAG remains

LOW and the microcontroller can read the failure information via the I2C-bus; pin DIAG

can be used as a microcontroller interrupt to minimize I2C-bus traffic. When the failure is

removed, pin DIAG is released.

To enable full control over the clipping information, pin STB can be programmed as a

second-clip detection pin. The clip detection level can be selected for all channels at once.

The clip information can be selected to be available separately at pin DIAG or at pin STB

for each channel. It is possible, for instance, to distinguish between clipping of the front

and the rear channels.

The diagnostic information available at either of the two diagnostic pins DIAG and STB is

shown in Table 4.

Fig 9.

Temperature controlled amplifier gain

001aam696

(dB)

Tj (°C)

140

190

180

160

170

150

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