IRAUDAMP7D Datasheet, PDF (29/43 Pages) International Rectifier – 25W-500W Scalable Output Power Class D Audio Power Amplifier Reference Design Using the IRS2092 Protected Digital Audio Driver

Input Signal and Gain Setting
A proper input signal is an analog signal ranging from 20Hz to 20kHz with up to 3 V_RMS amplitude
with a source impedance of no more than 600 Ω. Input signal with frequencies from 30kHz to
60kHz may cause LC resonance in the output LPF, causing a large reactive current flowing
through the switching stage, especially with greater than 8 Ω load impedances, and the LC
resonance can activate OCP.
The IRAUDAMP7D has an RC network called Zobel network (R30 and C13) to damp the
resonance and prevent peaking frequency response with light loading impedance. (Fig 32) The
Zobel network is not thermally rated to handle continuous supersonic frequencies above 20kHz.
These supersonic input frequencies can be filtered out by adding R2 and C2 as shown on main
schematic Fig 33 and Fig 34. This RC filter works also as an input RF filter to prevent potential
radio frequency interferences.
.
LP Filter
0V
.
0V
L1
.
C12
C13
.
Fig 32 Output Low Pass Filter and Zobel Network
Gain Setting
The ratio of resistors R8/R2 in Fig 23 sets voltage gain. The IRAUDAMP7D has no on board volume control.
To change the voltage gain, change the input resistor term R2. Changing R8 affects PWM control loop
design and may result poor audio performance.
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IRAUDAMP7D REV 2.8
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