Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Op-amp Multi-purpose TSSOP 8

ShortDetected

OpenDetectedNormalLoadDetected

ShortDetection

Range

OpenDetection

Range

0.5

300

1.5

1300

1(Typ) 800(Typ)

(IncludingWires)

Load

M0067-01

TAS5414A, TAS5424A

SLOS535C –MAY 2009– REVISED APRIL 2011

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Figure 14. Open and Shorted Load Detection

2. Tweeter Detection— Tweeter detection is an alternate operating mode that is used to determine the proper

connection of a frequency dependent load (such as a speaker with a crossover). Tweeter detection is

invoked via I

C, and all four channels should be tested individually. 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 is dependent 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 TAS5414A and

TAS5424A) must generate a signal to which the load will respond. 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 not properly

connected. 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, can be found in the Electrical Characteristics

section of the datasheet. The tweeter detection results are reported on the CLIP_OTW pin during the

application of the test signal. When tweeter detection is activated (indicating that the tested load is present),

pulses on the CLIP_OTW pin begin to toggle. The pulses on the CLIP_OTW pins will report low whenever

the current detection threshold is exceeded, and the pin will remain low until the threshold is no longer

exceeded. The minimum low-pulse period that can be expected is equal to one period of the switching

frequency. Having an input signal that increases the amount of time that the detector is activated (e. g.

increasing the amplitude of the input signal) will increase the amount of time for which the pin reports low.

NOTE: Because tweeter detection is an alternate operating mode, the channels to be tested must be placed

in Play mode (via register 0x0C) after tweeter detection has been activated in order to commence the

detection process. Additionally, the CLIP_OTW pin must be set up 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 when the average current limit (I

LIM

) threshold is exceeded. The overall effect on the

audio in the case of a current overload is quite similar to a voltage-clipping event, where power is temporarily

limited at the peaks of the musical signal and normal operation continues without disruption when the

overload is removed. The TAS5414A and TAS5424A 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, a

peak-current detector is used, 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 are shut down in such a scenario.