Datenblatt-Suchmaschine für elektronische Bauteile |
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TDA8588BJ Datenblatt(PDF) 9 Page - NXP Semiconductors |
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TDA8588BJ Datenblatt(HTML) 9 Page - NXP Semiconductors |
9 / 54 page 2004 Feb 24 9 Philips Semiconductors Product specification I2C-bus controlled 4 × 50 Watt power amplifier and multiple voltage regulator TDA8588J; TDA8588xJ compared with a reference voltage. If the output voltage of a channel is greater than the reference voltage, bit D2 of the associated data byte is set and read by the microcontroller during a read instruction. Note that the value of this bit is only meaningful when there is no input signal and the amplifier is not muted. Offset detection is always enabled. Speaker protection If one side of a speaker is connected to ground, a missing current protection is implemented to prevent damage to the speaker. A fault condition is detected in a channel when there is a mismatch between the power current in the high side and the power current in the low side; during a fault condition the channel will be switched off. The load status of each channel can be read via the I2C-bus: short to ground (one side of the speaker connected to ground), short to VP (one side of the speaker connected to VP), and shorted load. Line driver mode An amplifier can be used as a line driver by switching it to low gain mode. In normal mode, the gain between single-ended input and differential output (across the load) is 26 dB. In low gain mode the gain between single-ended input and differential output is 20 dB. Input and AC ground capacitor values The negative inputs to all four amplifier channels are combined at pin ACGND. To obtain the best performance for supply voltage ripple rejection and unwanted audible noise, the value of the capacitor connected to pin ACGND must be as close as possible to 4 times the value of the input capacitor connected to the positive input of each channel. Load detection DC-LOAD DETECTION When DC-load detection is enabled, during the start-up cycle, a DC-offset is applied slowly to the amplifier outputs, and the output currents are measured. If the output current of an amplifier rises above a certain level, it is assumed that there is a load of less than 6 Ω and bit D5 is reset in the associated data byte register to indicate that a load is detected. Because the offset is measured during the amplifier start-up cycle, detection is inaudible and can be performed every time the amplifier is switched on. AC-LOAD DETECTION AC-load detection can be used to detect that AC-coupled speakers are connected correctly during assembly. This requires at least 3 periods of a 19 kHz sine wave to be applied to the amplifier inputs. The amplifier produces a peak output voltage which also generates a peak output current through the AC-coupled speaker. The 19 kHz sine wave is also audible during the test. If the amplifier detects three current peaks that are greater than 550 mA, the AC-load detection bit D1 of instruction byte IB1 is set to logic 1. Three current peaks are counted to avoid false AC-load detection which can occur if the input signal is switched on and off. The peak current counter can be reset by setting bit D1 of instruction byte IB1 to logic 0. To guarantee AC-load detection, an amplifier current of more than 550 mA is required. AC-load detection will never occur with a current of less than 150 mA. Figure 3 shows which AC loads are detected at different output voltages. For example, if a load is detected at an output voltage of 2.5 V peak, the load is less than 4 Ω. If no load is detected, the output impedance is more than 14 Ω. LOAD DETECTION PROCEDURE 1. At start-up, enable the AC- or DC-load detection by setting D1 of instruction byte 1 to logic 1. mrc331 10 102 Zo(load) ( Ω) 1 Vo(peak) (V) 010 7.5 2.5 5 (2) (1) no load present load present undefined Fig.3 Tolerance of AC-load detection as a function of output voltage. (1) IO(peak) = < 150 mA. (2) IO(peak) = > 550 mA. |
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Ähnliche Beschreibung - TDA8588BJ |
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