TAS5414CTPHDRQ1 Datasheet, PDF (16/39 Pages) Texas Instruments – FOUR-CHANNEL AUTOMOTIVE DIGITAL AMPLIFIERS

TAS5414C-Q1
TAS5424C-Q1
SLOS795C – SEPTEMBER 2013 – REVISED JULY 2013
www.ti.com
Figure 14. Open- and Shorted-Load Detection
2. Tweeter Detection—Tweeter detection is an alternate operating mode used to determine the proper
connection of a frequency-dependent load (such as a speaker with a crossover). Invoking of weeter detection
is via I²C, with individual testing of all four channels recommended. Tweeter detection uses the average
cycle-by-cycle current limit circuit (see CBC section) to measure the current delivered to the load. The proper
implementation of this diagnostic function depends on the amplitude of a user-supplied test signal and on the
impedance-versus-frequency curve of the acoustic load. The system (external to the TAS5414C-Q1 and
TAS5424C-Q1) must generate a signal to which the load responds. The frequency and amplitude of this
signal must be calibrated by the user to result in a current draw that is greater than the tweeter detection
threshold when the load under test is present, and less than the detection threshold if the load is
unconnected. The current level for the tweeter detection threshold, as well as the maximum current that can
safely be delivered to a load when in tweeter-detection mode, is in the Electrical Characteristics section of
the data sheet. Reporting of the tweeter-detection results is on the CLIP_OTW pin during the application of
the test signal. With tweeter detection activated (indicating that the tested load is present), pulses on the
CLIP_OTW pin begin to toggle. The pulses on the CLIP_OTW pins report low whenever the current exceeds
the detection threshold, and the pin remains low until the current no longer exceeds the threshold. The
minimum low-pulse period that one can expect is equal to one period of the switching frequency. Having an
input signal that increases the duration of detector activation (for example, increasing the amplitude of the
input signal) increases the amount of time for which the pin reports low.
NOTE: Because tweeter detection is an alternate operating mode, place the channels to be tested in Play
mode (via register 0x0C) after tweeter detection has been activated in order to commence the detection
process. Additionally, set up the CLIP_OTW pin via register 0x0A to report the results of tweeter detection.
Protection and Monitoring
1. Cycle-By-Cycle Current Limit (CBC)—The CBC current-limiting circuit terminates each PWM pulse to limit
the output current flow to the average current limit (I_LIM) threshold. The overall effect on the audio in the case
of a current overload is quite similar to a voltage-clipping event, temporarily limiting power at the peaks of the
musical signal and normal operation continues without disruption on removal of the overload. The
TAS5414C-Q1 and TAS5424C-Q1 do not prematurely shut down in this condition. All four channels continue
in play mode and pass signal.
2. Overcurrent Shutdown (OCSD)—Under severe short-circuit events, such as a short to PVDD or ground,
the device uses a peak-current detector, and the affected channel shuts down in 200 μs to 390 μs if the
conditions are severe enough. The shutdown speed depends on a number of factors, such as the impedance
of the short circuit, supply voltage, and switching frequency. Only the shorted channels shut down in such a
scenario. The user may restart the affected channel via I²C. An OCSD event activates the fault pin, and the
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