TDF8541THSLASHN2 datasheet(17/54 Pages) NXP

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TDF8541

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Product data sheet

Rev. 3 — 13 December 2011

17 of 54

NXP Semiconductors

TDF8541

I2C-bus controlled 4

 45 W power amplifier

[1]

DBx[D3] indicates a shorted load; DBx[D1] indicates a short to VP; DBx[D0] indicates a short to ground.

When set, D4, D5 have no meaning.

If during the start-up diagnostics an engine start occurs, the generated offset to measure

the DC load is reduced and the start-up diagnostics cannot be performed correctly. In this

case the invalid combination DBx[D4:D5] = 11 is set.

The start-up diagnostics information in the I2C-bus bits is combined with the AC load

detection allowing the start-up diagnostics information to be read when IB4[D4] = 0. If

IB4[D4] = 1, the stored start-up diagnostics information bits cannot be read but they will

not lose their value.

Remark: the shorted load, and short to VP or ground information from the start-up

diagnostics is cleared after an I2C-bus read. This indicates the real situation: when the

short is removed, the bits are cleared. The DBx[D5] and DBx[D4] information, generated

at start-up, is refreshed after a new start-up diagnostics cycle.

7.5.2 DC offset detection

The offset detection can be performed with no input signal (for instance when the DSP is

muted after a start-up) or with an input signal. If in I2C-bus mode an I2C-bus read of the

output offset is performed, the I2C-bus DBx[D2] latches are set. If the amplifier BTL output

voltage is within a window with a threshold of 1.3 V (typical), the DBx[D2] latches are reset

and their setting is disabled. If for example, after 1 s another I2C-bus read is performed

and the offset bits are still set, the output did not cross the offset threshold during the last

1 second; see Figure 13. This can mean either a frequency below 1 Hz was applied (1 s

I2C-bus read interval) or an output offset of more than 1.3 V is present.

Table 5.

Start-up diagnostics I2C-bus bits

DC load bits[1]

Meaning

DBx[D5]

DBx[D4]

normal load

line driver mode

open load

invalid: overvoltage or

undervoltage (VP <10V) has

occurred, or start-up

diagnostics not completed, or

channel has short to VP;

indicated in second stage

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