TCA2002 Datasheet, PDF (10/18 Pages) Tripath Technology Inc. – STEREO CLASS-T™ AUDIO CONTROLLER USING DIGITAL POWER PROCESSING (DPP™) TECHNOLOGY

Tripath Technology, Inc. - Technical Information
Input Capacitor Selection
C_I can be calculated once a value for R_I has been determined. C_I and R_I determine the input low
frequency pole. Typically this pole is set below 10Hz. C_I is calculated according to:
CI= ¹
2π fP R I
where:
RI = Input resistor value in ohms.
fP = Input low frequency pole (typically 10Hz or below)
Modulator Feedback Design
The modulator feedback converts the high-voltage output-switching signal to voltage levels that the
TCA2002 can process. The optimum gain of the modulator is determined from the maximum
allowable feedback level for the modulator and maximum supply voltage for the power stage.
Depending on the maximum supply voltage, the feedback ratio will need to be adjusted for proper
operation and to maximize performance. The values of R_FBA, R_FBB and R_FBC (see explanation below)
define the gain of the modulator. In addition, the amplifier architecture affects the value of the
feedback resistor values. Once these values are chosen, based on the maximum supply voltage, the
gain of the modulator will be fixed even as the supply voltage changes. Thus, an amplifier based on
TCA2002 has inherent PSRR unlike many other commercially available switching amplifiers.
For the best signal-to-noise ratio and lowest distortion, the maximum differential modulator feedback
voltage should be approximately 4Vpp. This will keep the gain of the modulator as low as possible
and still allow headroom so that the feedback signal does not clip the modulator feedback stage.
Modulator Feedback Design
For SPLIT-SUPPLY, SINGLE ENDED operation:
TCA2002
FET Driver
VPP
MOSFETS
Y1
HIN
HS OUT
HS GATE
HB OUT
Y1B
LIN
LS OUT
LS GATE
FBKP1 FBKN1
V5
R _{FBA RFBC}
V5
R _FBB
R _{FBA RFBC}
R _FBB
VNN
Figure 3: Split Supply, Single Ended Circuit (One Channel)
Figure 3 shows the basic split supply, single ended amplifier using a TCA2002. The MOSFET output
stage operates from two power supplies, VPP and VNN, that are equal magnitude, but opposite
polarity (for instance +/-60VDC). One terminal of the load is driven by the half-bridge MOSFET
output stage. The other load terminal is ground referenced. Differential feedback is taken from the
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TCA2002 – KLi/0.95/04.06