Tripath Technology, Inc. – Technical Information
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 TPS4100A 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.
The following components are important to place near either their associated TPS4100A pins. The
recommendations are ranked in order of layout importance, either for proper device operation or
performance considerations.
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The capacitors, CBR, provide high frequency bypassing of the amplifier power supplies and will
serve to reduce spikes and modulation of the power supply rails. Please note that bypassing
requires a combination of capacitors for adequate stabilization.
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The output diodes, DO, are used to minimize overshoots/undershoots on the output node.
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.
The capacitors, CS, provide high frequency bypassing of the amplifier power supplies. Please note that
bypassing requires a combination of capacitors for adequate stabilization.
PROTECTION CIRCUITS
The TPS4100A is guarded against over-current, over/under voltage, and over-temperature conditions. If
the device goes into one of the various protection states, the FAULT pin goes to a logic HIGH state
indicating a fault condition. When this occurs, all amplifier outputs are TRI-STATED and will float to VDD.
OVER-CURRENT PROTECTION
An over-current fault occurs if more than approximately 12.5 amps (typical) of current flows from any of
the amplifier output pins. This can occur if the speaker wires are shorted together, if one side of the
speaker is shorted to ground, or if an output is connected to VPP.
OVER AND UNDER VOLTAGE PROTECTION
An over-voltage fault occurs if the supply voltage is increased above 30.0 volts (typical), 27.0 volts
(minimum). This fault puts the amplifier into mute and resets automatically once the supply voltage is
reduced below the hysteresis band. The TPS4100A also has built-in load dump protection. This circuit
puts the amplifier into sleep mode if the supply voltage is increased above 30V. The TPS4100A is able to
survive power supply spikes to 60V if the duration is less than 50mS.
The TPS4100A is also equipped with under voltage protection. This circuit is activated if the supply
voltage goes below 8.1 volts (typical) and causes the output to mute. Increasing the supply voltage
above the hysteresis band (typically 9.5V) will bring the amplifier out of mute mode.
OVER-TEMPERATURE PROTECTION
An over-temperature FAULT occurs if the junction temperature of the part exceeds 160°C (typical). The
thermal hysteresis is approximately 30°C, therefore the fault will automatically clear when the junction
temperature drops below 130°C.
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TPS4100A – KL/Rev. 1.1/11.05
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
