FDA903D datasheet(37/82 Pages) STMICROELECTRONICS

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FDA903D

Diagnostic

At the end of the diagnostic cycle the "Start Diag DC" instruction bit is reset to '0' by the

device itself, and the "open load" or "short load" messages respectively will be displayed on

I2C data bits.

If "Start Diag DC" bit is set to '1' while the channel is not in "MUTE" state, (for example:

"PLAY" state or "Eco-mode" state), the channel will perform the diagnostic as soon as it

enters in "MUTE" state.

If the amplifier channel is in "Eco-mode" and I2C instructions for PWM ON + DIAG DC +

PLAY are given at the same time the channel will perform the following sequence

automatically:

turn on power stage

perform DC diagnostic

enter PLAY mode

DC diagnostic must be performed only with PWM "In phase" modulation, in order to avoid

pop noise. "Out phase" modulation, if desired, must be selected after DC diagnostic

execution.

11.1.2

Relation with short circuit protection activation

After a short circuit protection intervention amplifier is set automatically in a protected status

during which "Short to Vcc/Gnd" diagnostic is performed.

At the end of "Short to Vcc/Gnd" diagnostic, if no shorts to Vcc/Gnd are present on the

outputs, the amplifier will run DC diagnostic only if the corresponding "Start Diag DC" bit is

set to "1". Otherwise the amplifier will go back to the state preceding the short circuit

protection intervention without performing diagnostic cycles.

After the diagnostic completion "Start Diag DC" bit is set back to "0" by the amplifier.

11.1.3

Load range

The thresholds for short load detection and open load detection can be configured through

IB10[7,6]. Including the tolerance, the impedance values to be considered are reported in

Figure 46.

Figure 46. Load range detection configured properly setting IB5 d7-d6

The DC diagnostic pulse has a configurable time duration: for detailed timings definition,

please refer to the DC Diagnostic user manual.

The DC diagnostic result is provided on I2C register DB2.

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