cxa2571n Sony Electronics, cxa2571n Datasheet - Page 18

• Manufacturer Part Number: cxa2571n
• Description: Rf Matrix Amplifier
• Manufacturer: Sony Electronics

Notes on Operation
[RFAC signal]
Stabilizing the RFAC signal
The RFAC system (RFSUM + EQ) is comprised entirely of non-inverted function blocks.
This is in order to support pickups with built-in RFSUM.
Therefore, if the voltage gain of each block is increased, a feedback loop is formed over the entire RFAC
system causing the RFAC signal to become unstable (oscillate).
In these cases, it is recommended to lower the EQ frequency response and the boost gain. This has a large
effect on the board (power supply, I/O signal cross talk, etc.) loop. The RFAC signal easily becomes unstable if
the VCA gain is increased, the EQ boost frequency is set to a high frequency, the EQ boost amount is
increased, etc.
The VCA gain is low in ROM mode, so the RFAC signal is stable.
The area where the RFAC signal becomes unstable is thought to vary for each set, as this is greatly affected
by the board loop as noted above.
Proposed stabilization measures
The board and other loop characteristics can be changed by adding external capacitance as noted below.
This has a particularly large effect on the stabilization when using RFSUM.
[Limiter circuit]
This IC has a limiter circuit to protect the input range of the rear-end IC (DSP) during excessive voltage output
for each signal (RFDC, FE, TE, CE).
When the limiter circuit operates, the maximum output voltage is limited to the DV
However, when limiting the excessive voltage output, the ON/OFF operation of the limiter circuit causes the
maximum output side (clipped portion of the output waveform) to oscillate slightly.
RF
SUM
ACSUM
Add capacitance of 10pF to 20pF
Example) AVcc = 5V, DVcc = 3V
0.1
EQI
– 18 –
VCA
3.0V
0V
EQ
CC
voltage or less.
AMP
CXA2571N