T E C H N I C A L I N F O R M A T I O N
Amplifier Gain
The gain of the TA2020-020 is set by the ratio of two external resistors, RI and RF, and is given by
the following formula:
V
V
R
F
O
= 12
R
I
I
where VI is the input signal level and VO is the differential output signal level across the speaker.
20 watts of RMS output power results from an 8.944 V RMS signal across a four-ohm speaker load.
If RF = RI, then 20 Watts will be achieved with 0.745 V RMS of input signal.
8.944VRMS = (RL ∗PO ) = (4Ω ∗ 20W)
Protection Circuits
The TA2020-020 is guarded against over-temperature and over-current conditions. When the
device goes into an over-temperature or over-current state, the FAULT pin goes to a logic HIGH
state indicating a fault condition. When this occurs, the amplifier is muted, all outputs are TRI-
STATED, and will float to 1/2 of VDD.
Over-temperature Protection
An over-temperature fault occurs if the junction temperature of the part exceeds approximately
155°C. The thermal hysteresis of the part is approximately 45°C, therefore the fault will
automatically clear when the junction temperature drops below 110°C.
Over-current Protection
An over-current fault occurs if more than approximately 7 amps of current flows from any of the
amplifier output pins. This can occur if the speaker wires are shorted together or if one side of the
speaker is shorted to ground. An over-current fault sets an internal latch that can only be cleared if
the MUTE pin is toggled or if the part is powered down. Alternately, if the MUTE pin is connected to
the FAULT pin, the HIGH output of the FAULT pin will toggle the MUTE pin and automatically reset
the fault condition.
Overload
The OVERLOADB pin is a 5V logic output. When low, it indicates that the level of the input signal
has overloaded the amplifier resulting in increased distortion at the output. The OVERLOADB
signal can be used to control a distortion indicator light or LED through a simple buffer circuit.
Sleep Pin
The SLEEP pin is a 5V logic input that when pulled high (>3.5V) puts the part into a low quiescent
current mode. This pin is internally clamped by a zener diode to approximately 6V thus allowing the
TA2020-020, Rev. 4.0, 09.00
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TRIPATH [ TRIPATH TECHNOLOGY INC. ]
