TDA2075A Datasheet, PDF (21/24 Pages) Tripath Technology Inc. – STEREO CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DIGITAL POWER PROCESSINGTM TECHNOLOGY

Tripath Technology, Inc. - Technical Information
each time the MOSFET is switched. If R_G is too small, excessive heat can be generated in the driver.
Large gate resistors lead to slower MOSFET switching edges which require a larger break-before-make
(BBM) delay.
Break-Before-Make (BBM) Timing Control
The complementary half-bridge power MOSFETs require a deadtime between when one transistor is
turned off and the other is turned on (break-before-make) in order to minimize shoot through currents.
The TDA2075A has an analog input pin that controls the break-before-make timing of the output
transistors. Connecting R_BBM from the BBMSET pin (pin 7) to analog ground creates a current that
defines the BBM setting by the following equation.
BBM (nsec) = 2 X R_BBM + 7
where R_BBM is in kΩ’s and 5kΩ < R_BBM* < 100kΩ
* An R_BBM of 0Ω will yield a BBM setting of 0nsec.
There is tradeoff involved in making this setting. As the delay is reduced, distortion levels improve but
shoot-through and power dissipation increase. All typical curves and performance information were done
with using a R_BBM. The actual amount of BBM required is dependent upon other component values and
circuit board layout, the value selected should be verified in the actual application circuit/board. It should
also be verified under maximum temperature and power conditions since shoot-through in the output
MOSFETs can increase under these conditions, possibly requiring a higher BBM setting than at room
temperature.
Recommended MOSFETs
The following devices are capable of achieving full performance, both in terms of distortion and efficiency,
for the specified load impedance and voltage range. Additional devices will be added as subsequent
characterization is completed.
Device Information – Recommended MOSFETs
Part Number
FQP13N10
FQP12P10
Manufacturer
Fairchild Semiconductor
Fairchild Semiconductor
BV_DSS (V)
100
-100
I_D (A)
12.8
-11.5
Q_g (nC)
12
21
R_DS(on) (Ω)
0.142
0.240
Package
TO220
TO220
Output Filter Design
One advantage of Tripath amplifiers over PWM solutions is the ability to use higher-cutoff-frequency
filters. This means load-dependent peaking/droop in the 20kHz audio band potentially caused by the filter
can be made negligible. This is especially important for applications where the user may select a 6-Ohm
or 8-Ohm speaker. Furthermore, speakers are not purely resistive loads and the impedance they present
changes over frequency and from speaker model to speaker model.
Tripath recommends designing the filter as a 2nd order LC filter. Tripath has obtained good results with
L_F = 11uH and C_F = 0.22uF.
The core material of the output filter inductor has an effect on the distortion levels produced by a
TDA2075A amplifier. Tripath recommends low-mu type-2 iron powder cores because of their low loss
and high linearity (available from Micrometals, www.micrometals.com). Please refer to the RB-
TDA2075A for the specific core used.
Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load operation of a
TDA2075A amplifier can create significant peaking in the LC filter, which produces strong resonant
currents that can overheat the output MOSFETs and/or other components. The RC dampens the
peaking and prevents problems. Tripath has obtained good results with R_Z = 20Ω and C_Z = 0.22uF.
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TDA2075A – Rev. 0.9/KLi/10.05