TDF8553J 데이터 시트보기 (PDF) - NXP Semiconductors.

부품명

상세내역

일치하는 목록

TDF8553J

I2C-bus controlled 4 X 50 Watt power amplifier and multiple voltage regulator

NXP Semiconductors. 

NXP Semiconductors

TDF8553J

4 × 50 Watt power amplifier and multiple voltage regulator

8.5.6 Input and AC ground capacitor values

The negative inputs to all four amplifier channels are combined at pin ACGND. To obtain

the best performance of 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.

8.5.7 Load detection

8.5.7.1 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.

8.5.7.2 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 is set. 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.

TDF8553J_1

Objective data sheet

Rev. 01 — 3 December 2008

© NXP B.V. 2008. All rights reserved.

10 of 47

Share Link: