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Page 24 of 34
IRAUDAMP10 REV
1.1
Power Supply Requirements
For convenience, the IRAUDAMP10 has all the necessary housekeeping power supplies onboard
and only requires a pair of symmetric power supplies.
House Keeping Power Supply
The internally-generated housekeeping power supplies include ±5V for analog signal processing,
and +12V supply (V
CC
) referred to the negative supply rail -B for DirectFET gate drive. The gate
driver section of the IRS2052M uses VCC to drive gates of the DirectFETs. V
CC
is referenced to –
B (negative power supply). D2x, R18x and C10x form a bootstrap floating supply for the HO gate
driver.
Bus Pumping
When the IRAUDAMP10 is running in stereo mode, the bus pumping effect takes place with low
frequency, high output. Since the energy flowing in the Class D switching stage is bi-directional,
there is a period where the Class D amplifier feeds energy back to the power supply. The majority
of the energy flowing back to the supply is from the energy stored in the inductor in the output LPF.
Usually, the power supply has no way to absorb the energy coming back from the load.
Consequently the bus voltage is pumped up, creating bus voltage fluctuations.
Following conditions make bus pumping worse:
1. Lower output frequencies (bus-pumping duration is longer per half cycle)
2. Higher power output voltage and/or lower load impedance (more energy transfers between
supplies)
3. Smaller bus capacitance (the same energy will cause a larger voltage increase)
The OVP protects IRAUDAMP10 from failure in case of excessive bus pumping. Bus voltage
detection monitors only +B supply, assuming the bus pumping on the supplies is symmetric in +B
and -B supplies.
Load Impedance
Each channel is optimized for a 4
Ω
speaker load in half bridge.
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.
