Tripath Technology, Inc. – Technical Information
Application Information
GENERAL DESCRIPTION
The TPS4100A is a 4-channel BTL (Bridge Tied Load) audio amplifier power stage 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 TPS4100A 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.
POWER SUPPLY REQUIREMENTS
The device is configured to operate from a single supply voltage of 10-26V. This allows the device to
operate from an automobile battery under various conditions including: battery voltage with the engine off,
alternator voltage with engine running and boosted voltage operation up to 26V using a DC-DC converter
or voltage booster. The sleep pin must be driven from a microcontroller or external 3.3V or 5.0V power
supply.
AM MODE
The TPS4100A is typically configured as a high power, high efficiency, four channel switching amplifier.
The TPS4100A also has an additional amplifier mode named “AM Mode.” By pulling the AM pin to a logic
high level, the TPS4100A is configured as a Class B amplifier as opposed to the normal, Class-T
amplifier.
AM mode significantly reduces EMI generation since the output amplifiers are now operated in linear
mode. Operating in Class B mode also reduces the TPS4100A efficiency especially at low to medium
output powers. Due to this increased power dissipation, it is recommended that the AM mode is used for
applications such as AM radio playback where the average output level is minimal and a switching
amplifier would most effect radio reception. The operating supply range is also limited to 10V-16V due to
the increased power dissipation.
A DC to DC converter that is used to step up the battery voltage for Class T operation (for instance 14.4V
ꢁ20V or above) should be disabled before entering AM Mode. This will ensure that the supply voltage in
AM Mode is limited to the battery voltage thereby minimizing the device power dissipation.
To avoid possible damage to the output stage, appropriate sequencing must be adhered to when
activating or disabling AM Mode. The TPS4100A MUST be muted (MUTEB = high) during logic changes
of the AM pin.
To change from Class-T mode to AM Mode, the following procedure must be followed.
With AM = Low and MUTEB = High ꢁ MUTEB = Low ꢁ AM = High ꢁ MUTEB = High
To change from AM Mode to Class-T mode, the following procedure must be followed.
With AM = High, MUTEB = High ꢁ MUTEB = Low ꢁ AM = Low ꢁ MUTEB = High
Thus, MUTEB is low during any transition of the AM pin.
CIRCUIT BOARD LAYOUT
When used in conjunction with a Class T controller the TPS4100A is a power (high current) amplifier that
operates at relatively high switching frequencies. Therefore, amplifier outputs switch between the supply
10
TPS4100A – KL/Rev. 1.1/11.05
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
