Tri p ath Techn o l o g y, I n c. - Techn i cal I n fo rmati o n

13

TAA4100A – KL/ Rev. 1.0/11.05

Application Information

GENERAL DESCRIPTION

The TAA4100A is a 4-channel BTL (Bridge Tied Load) output audio amplifier that operates on a single

supply voltage ranging from 10-26V. The device is targeted specifically to meet the demands of OEM and

aftermarket automobile in-dash head units. With a single supply voltage of 25V, the device delivers four

100 Watt (saturated square wave) channels into 4 ohm. Since the TAA4100A is a switching amplifier, the

average dissipation at low to medium output power is far superior to best in class AB amplifiers

specifically designed for in-dash head units.

TAA4100A BASIC AMPLIFIER OPERATION

The TAA4100A has three major operational blocks: the signal processor, the MOSFET driver and the

power MOSFETs. The signal processor is a 5V CMOS block that amplifies the audio input signal and

converts the signal to a high frequency switching pattern. This switching pattern is spread spectrum in

nature and has a typical idle switching frequency of about 650kHz.

The MOSFET driver level shifts the processor’s 5V switching pattern to the VPP power supply voltage

and drives the power MOSFETs. The MOSFETs are N-channel devices configured as a full bridge to

supply audio power to the load. The outputs of the power MOSFETs must be low pass filtered to remove

the high frequency switching pattern leaving only the amplified audio signal.

CIRCUIT BOARD LAYOUT

The TAA4100A is a power (high current) amplifier that operates at relatively high switching frequencies.

Therefore, amplifier outputs switch between the supply voltage and ground at high speeds while driving

high currents. This high-frequency digital signal is passed through an LC low-pass filter to recover the

amplified audio signal. Since the amplifier must drive the inductive LC output filter and speaker loads, the

amplifier outputs can be pulled above the supply voltage and below ground by the energy in the output

inductance. To avoid subjecting the TAA4100A to potentially damaging voltage stress, it is critical to have

a good printed circuit board layout. It is recommended that Tripath’s layout and application circuit be used

for all applications and only be deviated from after careful analysis of the effects of any changes. Please

refer to the TAA4100A evaluation board document, EB-TAA4100A, available on the Tripath website, at

www.tripath.com.

The following components are important to place near either their associated TAA4100A pins. The

recommendations are ranked in order of layout importance, either for proper device operation or

performance considerations.

-

serve to reduce spikes and modulation of the power supply rails. Please note that bypassing

requires a combination of capacitors for adequate stabilization.

-

Improper routing of these diodes will render them useless due to PCB trace inductance. Thus,

these components must be located very close to the output pins with the “other side of the

diode” routed directly to the appropriate VPP or PGND pin.

-

note that bypassing requires a combination of capacitors for adequate stabilization.

TAA4100A GROUNDING

Proper grounding techniques are required to maximize TAA4100A functionality and performance.

Parametric parameters such as THD+N, Noise Floor and Crosstalk can be adversely affected if proper