International Rectifier IRAUDAMP4, Руководство пользователя

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RD-0617
Figure 3. Power Supply Rejection Ratio (PSRR) for Negative (-B) and Positive (+B) Supplies
Bus Pumping
Since the IRAUDAMP4 is a half-bridge configuration, bus pumping does occur. Under
normal operation during the first half of the cycle, energy flows from one supply through
the load and into the other supply, thus causing a voltage imbalance by pumping up the
bus voltage of the receiving power supply. In the second half of the cycle, this condition
is reversed, resulting in bus pumping of the other supply.
These conditions worsen bus pumping:
–
Lower frequencies (bus-pumping duration is longer per half cycle)
– Higher power output voltage and/or lower load impedance (more energy
transfers between supplies)
– Smaller bus capacitors (the same energy will cause a larger voltage increase)
The IRAUDAMP4 has protection features that will shutdown the switching operation if
the bus voltage becomes too high (>40 V) or too low (<20 V). One of the easiest
countermeasures is to drive both of the channels out of phase so that one channel
consumes the energy flow from the other and does not return it to the power supply. Bus
voltage detection is only done on the –B supply as the effect of the bus pumping on the
supplies is assumed to be symmetrical in amplitude (although opposite in phase).
Input
A proper input signal is an analog signal below 20 kHz, up to ±3.5 V peak, having a
source impedance of less than 600
Ω . A 30 kHz to 60 kHz input signal can cause LC
resonance in the output LPF, resulting in an abnormally large amount of reactive current
flowing through the switching stage (especially at 8
Ω or higher impedance towards open
load), causing OCP activation. The IRAUDAMP4 has an RC network, or Zobel network,
to damp the resonance and protect the board in such event, but is not thermally rated to
handle continuous supersonic frequencies.
These supersonic input frequencies
therefore should be avoided.
Separate mono RCA connectors provide input to each of
the two channels. Although both channels share a common ground, it is necessary to
connect each channel separately to limit noise and crosstalk between channels.
-90
+0
-80
-70
-60
-50
-40
-30
-20
-10
d
B
20 40k 50 100 200 500 1k 2k 5k 10k 20k
Hz
+B
-B