TA3020 Ver la hoja de datos (PDF) - Unspecified
Número de pieza
componentes Descripción
Fabricante
TA3020 Datasheet PDF : 27 Pages
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Tripath Technology, Inc. - Technical Information
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 TA3020 would need to be
implemented to detect these failures.
DC Offset
While the DC offset voltages that appear at the speaker terminals of a TA3020 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 TA3020 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 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 TA3020 has over-current protection circuitry to protect itself and the output transistors from short-circuit
conditions. The TA3020 uses the voltage across a resistor RS (measured via OCS1HP, OCS1HN, OCS1LP
and OCS1LN) 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 TA3020 will shut off the
output stages of its amplifiers. The occurrence of an over-current condition is latched in the TA3020 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)
ROCR = (3580 x VTOC)/(ISC * RS+3580 * IBIAS)
where:
RS and ROCR are in Ω
VTOC = Over-current sense threshold voltage (See Electrical Characteristics Table)
= 0.97V typically
IBIAS = 20uA
For example, to set an ISC of 30A, ROCR = 9.63KΩ and RS will be 10mΩ.
As high-wattage resistors are usually only available in a few low-resistance values (10mΩ, 25mΩ and 50mΩ),
ROCR can be used to adjust for a particular over-current threshold using one of these values for RS.
It should be noted that the addition of the bulk CHBR capacitor shown in the Application / Test Diagram will
increase the ISC level. Thus, it will be larger than the theoretical value shown above. Once the designer has
settled on a layout and specific CHBR value, the system ISC trip point can be adjusted by increasing the ROCR
value. The ROCR should be increased to a level that allows expected range of loads to be driven well into
clipping without current limiting while still protecting the output MOSFETs in case of a short circuit condition.
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TA3020 – KL Rev. 3.0/09.03
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