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Page 19 of 34
IRAUDAMP10 REV
1.1
Self-Oscillating Frequency
Self-oscillating frequency is determined by the total delay time along the control loop of the
system; the propagation delay of the IRS2052M, the DirectFETs switching speed, the time-
constant of front-end integrator (R2x, R3x, R4x, Vr1x, C2x, C3x ). Variations in +B and –B supply
voltages also affect the self-oscillating frequency.
The self-oscillating frequency changes with the duty ratio. The frequency is highest at idling. It
drops as duty cycle varies away from 50%.
Adjustments of Self-Oscillating Frequency
Use VR1x to set different self-oscillating frequencies. The PWM switching frequency in this type of
self-oscillating switching scheme greatly impacts the audio performance, both in absolute
frequency and frequency relative to the other channels. In absolute terms, at higher frequencies,
distortion due to switching-time becomes significant, while at lower frequencies, the bandwidth of
the amplifier suffers. In relative terms, interference between channels is most significant if the
relative frequency difference is within the audible range.
Normally, when adjusting the self-oscillating frequency of the different channels, it is suggested to
either match the frequencies accurately, or have them separated by at least 25kHz. Under the
normal operating condition with no audio input signal, the switching-frequency is set around
500kHz in the IRAUDAMP10
.
Internal Clock Oscillator
The IRS2052M integrates two clock oscillators and synchronization networks for each PWM
channel. To prevent AM radio reception interference, two PWM frequencies are selectable via XSL
pin. As shown in Table 2, when XSL is bias to VAA, X1A and X1B are active. When XSL is GND
X2A and X2B are active. When XSL is VSS, both clock oscillators are disabled.
XSL pin
X1A/B
X2A/B
VAA
Activated Disabled
GND
Disabled Activated
VSS
Disabled Disabled
CKO outputs internal clock with VAA/VSS amplitude. The CKO can distribute clock signal to
multiple IRS2052 devices to synchronize PWM switching timing.
