NXPTDF8554JI2C bus control 4x45W audio power amplifier scheme

NXP’s TDF8554J is an I2C bus-controlled 4x45W audio power amplifier that integrates multiple voltage regulators and two power switches. The amplifier uses a SOI-based BCD process with complementary DMOS output stages for large output signals and perfect Sound quality. The device operates from a voltage as low as 6V, I2C bus mode (3.3V and 5V compatible), can drive 2 or 4 ohm loads, speaker fault detection, programmable gain (26 dB and 16 dB), mainly used in automotive Audio System. This article introduces the TDF8554J main features and advantages, block diagram, ground loss and VP loss measurement circuit diagram, as well as measurement and application circuit diagram and PCB component layout.

The TDF8554J is one of a new generation of complementary quad Bridge-Tied Load (BTL) audio power amplifiers with full I2C-bus controlled diagnostics, multiple voltage regulator and two power switches intended for automotive applications.

The TDF8554J can operate at a battery voltage as low as 6 V making this amplifier suitable for stop/start-car operation. The amplifier uses a complementary DMOS output stage in a Silicon-On-Insulator (SOI)-based BCD process. The DMOS output stage ensures a high power output signal with perfect sound quality. The SOI-based BCD process ensures a robust amplifier, where latch-up cannot occur, with good separation between the four independent channels with every component isolated and without substrate currents.

The multiple voltage regulator comprises four programmable voltage regulators, one standby regulator and two power switches.

The TDF8554J is soft- and hardware downwards-compatible with its predecessor TDA8589XJ.

The TDF8554J includes features, such as selectable undervoltage for stop/start-cars which can be selected with additional I2C-bus instruction bytes. If these additional bytes are not sent, the TDF8554J has the same functionality as its predecessor IPAS TDA8589XJ.

TDF8554J main features and advantages:

 Amplifier

 Stop/start-car prepared: keeps operating without audible disturbance during engine start at a battery voltage as low as 6 V

 I2C-bus mode (3.3 V and 5 V compliant)

Can drive 2ohm or 4ohm loads

 Speaker fault detection

 Start-up diagnostics with load detection: open, short, present; filtered for door-slam and chatter relays

 AC load (tweeter) detection with low and high current mode

 Gain select after start-up without audible disturbance

 Programmable gain (26 dB and 16 dB), independently programmable for the front and rear channels

 Line driver mode (16 dB and mid-tap voltage 0.25VP for stop/start-cars)

 Programmable clip detection: 2 %, 5 % or 10 %

 Programmable thermal pre-warning

 If the temperature protection of the regulator is activated, the amplifier is muted before the regulator is switched off

 Loss of ground and open VP safe (with 150 m series impedance and a maximum supply decoupling capacitor of 2200 F)

 All amplifier outputs short-circuit proof to ground, supply voltage and across the load (channel independent)

 All pins short-circuit proof to ground

 Temperature-controlled gain reduction to prevent audio holes at high junction Temperatures

 Programmable low battery voltage detection to enable 7.5 V or 6 V minimum battery voltage operation

 Overvoltage protection (load-dump safe up to VP = 50 V) and overvoltage pre-warning at 16 V

 Offset detection

 Multiple regulators

 Good stability for any regulator with almost any output capacitor

 Five voltage regulators (microcontroller, Display, audio processor, mechanical digital and mechanical drive)

 I2C-bus controlled

 Selectable output voltages for regulators 1, 4 and 5

 Low dropout voltage PNP output stages

 High supply voltage ripple rejection

 Low noise for all regulators

 Two power switches (antenna switch and amplifier switch)

 Standby regulator (microcontroller supply) operational during load dump and thermal shut-down

 Low standby quiescent current (only regulator 2 operational)

 Backup functionality for regulator 2

 Protection

 If connection to the battery voltage is reversed, all regulator voltages will be zero

 Able to withstand output voltages up to 18 V if supply line is short-circuited

 Thermal protection to avoid thermal breakdown

 Load-dump protection

 Regulator outputs protected from DC short-circuit to ground or to supply voltage

 All regulators protected by foldback current limiting

 Power switches protected from loss-of-ground

Figure 1. TDF8554J block diagram

Figure 2. TDF8554J ground loss measurement circuit diagram

Figure 2. TDF8554J VP Loss Measurement Circuit Diagram

Figure 4. TDF8554J Measurement and Application Circuit Diagram