Power Amplifier TDA7850: Specification, Application, and Instruction

General Description

TDA7850 is a kind of power amplifier based on a breakthrough MOSFET technology, which is designed for high-power car radio. It is available in Flexiwatt 25 package. The P-Channel and the N-Channel output structure is fully complementary, which allows a rail to rail output voltage swing. Meanwhile, the TDA7850 supports high output current and minimal saturation losses. Therefore, new power references are set for car radio to make it characterized by unparalleled distortion performances.

TDA7850 features high output power, excellent 2Ω driving capability, low output noise, Hi-Fi class distortion, and MOSFET output power stage.  It is equipped with few external components, thus there is no external compensation, no bootstrap capacitors, and its features an internally fixed gain of 26 dB.

TDA7850 is widely used for high-power car audio to improve output power and sound quality.

Specification

Operating temperature: -55°C~150°C TJ

Max Power dissipation: 80W

Technology: MOS

Voltage – supply: 8V~18V

Supply voltage-max (Vsup): 18V

Power supplies: 13.2V

Power dissipation: 80W

Supply current-max: 280mA

Output power: 50W

Bandwidth: 20 kHz

Voltage gain: 26dB

Max output power: 85W

Harmonic distortion: 10%

Block Diagram

TDA7850 block diagram

CAD Model

Symbol

TDA7850 symbol

Footprint

TDA7850 footprint

3D Model

TDA7850 3d model

Instruction

Where to Use

Ensure that the audio amplifier works normally when the car engine starts/stops

In today’s era of more and more enjoyment, car drivers have higher and higher requirements for car audio. The world’s automotive trendsetters, BMW and Mercedes-Benz, have recently put forward new requirements to OEM manufacturers in terms of automotive entertainment systems, that is, the audio output of the car can still work normally when the car is started/stopped.

The effect on the audio output when the car starts/stops

To reduce carbon dioxide emissions, cars usually stop their engines when they encounter a traffic light or a traffic accident. When the engine stops, the high load will be directly added to the car’s battery, and at this time the battery voltage has a rapid drop. When the car engine starts, the car will define its work according to its state (such as battery Undervoltage, motor temperature, air conditioning, clutching, gearing, etc.). In both cases, the power supply of the car’s entertainment system comes from the car battery. Figure 1 shows the performance process of the car battery in the above behavior of the car. The 0-t1 time is defined as the normal working state of the car, the engine is operating normally and the battery is charged, and the voltage is maintained at 14.4V. At this time, the car audio amplifier is working at 14.4V. At t1, the engine stops and the battery begins to have a rapid discharge process. Eventually, the battery voltage drops to approximately U2. At t2, the engine starts to start. At this time, the battery has a short-circuit process of several milliseconds. During this process, the battery voltage will quickly drop to about 6V. Usually, 6V is the worst case. The time after time t3 is the change of the battery after the engine is started and running.

the performance process of the car battery

Usually, when the car audio power amplifier is stopped and started in the past, the car audio amplifier will enter the mute state, that is, there is no sound output. The root cause is when the car engine is stopped and started, the capacitors that establish the static operating point of the peripheral circuit all have a rapid discharge behavior, and the rapid discharge causes the circuit to no longer work normally. The current car audio amplifiers on the market will enter the mute state during rapid battery discharge and low voltage, which is determined by the circuit structure of the amplifier.

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