Tripath Technology, Inc. - Preliminary Information
(VPP). This resistor accounts for the internal VPPSENSE bias of 2.5V. Nominal
resistor value should be equal to that of RVPP1. Please refer to the Over / Under-
voltage Protection section in the Application Information for a detailed discussion of
the internal circuit operation and external component selection.
RS
Over-current sense resistor. Please refer to the section, Setting the Over-current
Threshold, in the Application Information for a discussion of how to choose the value
of RS to obtain a specific current limit trip point.
CHBR
Supply decoupling for the high current Half-bridge supply pins. These components
must be located as close to the output MOSFETs as possible to minimize output
ringing which causes power supply overshoot. By reducing overshoot, these
capacitors maximize both the TDA1400 and output MOSFET reliability. These
capacitors should have good high frequency performance including low ESR and
low ESL. In addition, the capacitor rating must be twice the maximum VPP voltage.
Panasonic EB capacitors are ideal for the bulk storage (nominally 33uF) due to their
high ripple current and high frequency design.
RG
Gate resistor, which is used to control the MOSFET rise/ fall times. This resistor
serves to dampen the parasitics at the MOSFET gates, which, in turn, minimizes
ringing and output overshoots. The typical power rating is 1/2 watt.
Gate diode, which adds additional BBM and serves to match the unequal rise and
fall times of QN and QP. An ultra-fast diode with a current rating of at least 200mA
should be used.
DG
DBIAS
Diode that keeps the gate capacitor biased at the proper voltage when the supply
voltage decreases.
CG
Gate capacitor that ac-couples the TDA1400 from the high voltage MOSFETs.
Bias resistors for the increasing supply circuits.
RISA, RISB
CISA
Bias capacitor for the increasing supply circuits.
QISP
P-channel bipolar transistor for the circuit which charges the high side gate
capacitors, CG, to VPP, in the case where the VPP supply increases in magnitude.
N-channel bipolar transistor for the circuit which charges the low side gate
capacitors, CG, to VNN, in the case where the VNN supply increases in magnitude.
Zobel capacitor, which in conjunction with RZ, terminates the output filter at high
frequencies. Use a high quality film capacitor capable of sustaining the ripple current
caused by the switching outputs.
QISN
CZ
QP
QN
RZ
P-channel power-MOSFET of the output stage.
N-channel power-MOSFET of the output stage.
Zobel resistor, which in conjunction with CZ, terminates the output filter at high
frequencies. The combination of RZ and CZ minimizes peaking of the output filter
under both no load conditions or with real world loads, including loudspeakers which
usually exhibit a rising impedance with increasing frequency. Depending on the
program material, the power rating of RZ may need to be adjusted. The typical
power rating is 2 watts.
LO
Output inductor, which in conjunction with CO, demodulates (filters) the switching
waveform into an audio signal. Forms a second order filter with a cutoff frequency
of
and a quality factor of
.
LO CO
f
= 1 (2π L
C )
O
Q = RL CO
C
O
CO
Output capacitor, which, in conjunction with LO, demodulates (filters) the switching
waveform into an audio signal. Forms a second order low-pass filter with a cutoff
frequency of
and a quality factor of
)
O
.
f
= 1 (2π L
C
Q = RL CO 2 L O C O
C
O
Use a high quality film capacitor capable of sustaining the ripple current caused by
the switching outputs.
DDS
These diodes must be connected from either the drain of the p-channel MOSFET to
the source of the n-channel MOSFET, or the source of the p-channel MOSFET to
the drain of the n-channel MOSFET This diode absorbs any high frequency
overshoots caused by the output inductor LO during high output current conditions.
In order for this diode to be effective it must be connected directly to the two
MOSFETs. An ultra-fast recovery diode that can sustain the entire supply voltage
should be used here. In most applications a 100V or greater diode must be used.
Resistor that turns QN and QP off when no signal is present.
RGS
RFLT
Pull-down resistor for the open-drain Fault circuit.
10
TDA1400 – Rev. 0.65/KLi/02.06
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
