TA0104A Tripath Technology Inc., TA0104A Datasheet - Page 8

• Manufacturer Part Number: TA0104A
• Manufacturer: Tripath Technology Inc.

T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
TA0104A Amplifier Operation
Figure 1 is a simplified diagram of one channel (Channel 1) of a TA0104A amplifier to assist in
understanding its operation.
The audio input signal (IN1) is fed to the processor internal to the TA0104A, where a modulation
pattern is generated. This pattern is spread spectrum and varies between approximately 200kHz and
1.5MHz. Complementary copies of the switching pattern are level-shifted by the MOSFET drivers and
output from the TA0104A where they drive the gates (HO1 and LO1) of external power MOSFETs that
are connected as a half bridge. The output of the half bridge is a power-amplified version of the
switching pattern that switches between V
and V
. This signal is then low-pass filtered to
SPOS
SNEG
obtain amplified audio.
The processor portion of the TA0104A is operated from a 5-volt supply (between V5 and AGND). In
the generation of the complementary modulation pattern for the output MOSFETs, the processor
inserts a “break-before-make” dead time between when it turns one transistor off and it turns the
other one on in order to minimize shoot-through currents in the MOSFETs. The dead time can be
programmed by setting the break-before-make control bits, BBM0 and BBM1. Feedback information
from the output of the half-bridge is supplied to the processor via FDBKN1. Additional feedback
information to account for ground bounce is supplied via GNDKELVIN1.
The MOSFET drivers in the TA0104A are operated from voltages obtained from VN12 and LO1COM
for the low-side driver, and V
(generated internal to the TA0104A) and HO1COM for the high-
BOOT
side. Only N-Channel MOSFETs are required for both the top and bottom of the half bridge. VN12
must be a stable 12V above V
. The gate resistors, R
, are used to control MOSFET slew rate
SNEG
G
and thereby minimize voltage overshoots.
Over- and Under-Voltage Protection
The TA0104A senses the power rails through V
and V
for over- and under-voltage conditions.
SPOS
SNEG
The over- and under-voltage limits are Vo and Vu respectively as specified in the Electrical
Characteristics table. If the supply voltage exceeds Vo or drops below Vu, the TA0104A shuts off the
output stages of the amplifiers and asserts a logic level high on HMUTE. The removal of the over-
voltage or under-voltage condition returns the TA0104A to normal operation and returns HMUTE to a
logic level low. Please note that the limits specified in the Electrical Characteristics table are at 25qC
and these limits may change over temperature.
Over-current Protection
The TA0104A has over-current protection circuitry to protect itself and the output transistors from
short-circuit conditions.
The TA0104A uses the voltage across a resistor, R
(measured via
S
OCS1H+, OCS1H-, OCS1L+ and OCS1L-), that is in series with each output MOSFET to detect an
over-current condition. R
and R
are used to set the over-current threshold. The OCS pins must
S
OCR
be Kelvin connected for proper operation. See “Circuit Board Layout” in Application Information for
details.
An over-current condition will cause the TA0104A to shut off the output stages of the
amplifiers and supply a logic level high on HMUTE. The occurrence of an over-current condition is
latched in the TA0104A and can be cleared by toggling the MUTE input or cycling power.
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TA104A – Rev. 3.1/06.00