Tripath Technology, Inc. - Technical Information
are fully operational. There is a delay of approximately 200 milliseconds between the de-
assertion of MUTE and the un-muting of the TK2150.
Sleep
When a logic high signal is supplied to SLEEP, the two channels on the TP2150 will be shutdown
and the outputs will be muted. When a logic level low is supplied to SLEEP, both channels are
fully operational.
Turn-on & Turn-off Noise
If turn-on or turn-off noise is present in a TK2150 amplifier, the cause is frequently due to other
circuitry external to the TK2150. While the TK2150 has circuitry to suppress turn-on and turn-off
transients, the combination of the power supply and other audio circuitry with the TK2150 in a
particular application may exhibit audible transients. One solution that will completely eliminate
turn-on and turn-off pops and clicks is to use a relay to connect/disconnect the amplifier from the
speakers with the appropriate timing at power on/off. The relay can also be used to protect the
speakers from a component failure (e.g. shorted output MOSFET), which is a protection
mechanism that some amplifiers have. Circuitry external to the TK2150 would need to be
implemented to detect these failures.
DC Offset
While the DC offset voltages that appear at the speaker terminals of a TK2150 amplifier are
typically small, Tripath recommends that any offsets during operation be nulled out of the
amplifier with a circuit like the one shown connected to IN1 and IN2 in the Test/Application
Circuit.
It should be noted that the DC voltage on the output of a TK2150 amplifier with no load in mute
will not be zero. This offset does not need to be nulled. The output impedance of the amplifier in
mute mode is approximately 10KΩ. This means that the DC voltage drops to essentially zero
when a typical load is connected.
HMUTE
The HMUTE pin on the TC2001 is a 5V logic output that indicates various fault conditions within
the device. These conditions include: over-current, overvoltage and undervoltage. The HMUTE
output is capable of directly driving an LED through a series 2kΩ resistor.
Over-current Protection
The TK2150 has over-current protection circuitry to protect itself and the output transistors from
short-circuit conditions. The TK2150 uses the voltage across a resistor RS (measured via
OCS1HP, OCS1HN, OCS1LP and OCS1LN of the TP2150) that is in series with each output
MOSFET to detect an over-current condition. RS and ROCR are used to set the over-current
threshold. The OCS pins must be Kelvin connected for proper operation. See “Circuit Board
Layout” in Application Information for details.
When the voltage across ROCR becomes greater than VTOC (approximately 1.0V) the TC2001 will
shut off the output stages of its amplifiers. The occurrence of an over-current condition is latched
in the TK2150 and can be cleared by toggling the MUTE input or cycling power.
Setting Over-current Threshold
RS and ROCR determine the value of the over-current threshold, ISC:
ISC = 3580 x (VTOC – IBIAS * ROCR)/(R OCR * RS)
R
OCR = (3580 x VTOC)/(ISC * RS+3580 * IBIAS
)
where:
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TK2150 – Rev. 1.0/12.02
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
