cxa1992br Sony Electronics, cxa1992br Datasheet - Page 17

• Manufacturer Part Number: cxa1992br
• Description: Rf Signal Processing Servo Amplifier
• Manufacturer: Sony Electronics

Focus Error Amplifier
The focus error amplifier calculates the difference between output VA and VB of the RF I-V amplifier, and
output current-voltage converted voltage of the photo diode (A + C – B – D).
The FEO output voltage:
The focus error amplifier has a built-in bias adjustment circuit to enable software-based automatic adjustment.
The focus bias adjustment is performed by turning the focus bias adjustment switches (IFB1 to IFB6) ON and
OFF.
The 6-bit focus bias adjustment switches are controlled with commands.
IFB1 to IFB6 are all ON after a reset.
The voltage is varied by approximately 25mV per step.
FE_BIAS
B + D
A + C
PD2
PD1
39
38
40
V
FEO
VC
VC
=
= 315.4k (iPD2 – iPD1)
=
V
V
1
EE
CC
58k
58k
174k
174k
R3
R2
32k
32k
2
PD2 IV AMP
PD1 IV AMP
4
RESET : IFB1 to IFB6 ON
8
VB
VA
RF
RF
(VA – VB)
{(–58k
25mV/STEP
16
V2
V1
32
32k
32k
R5
R4
R1
4k
iPD1) – (–58k
VC
174k
FE AMP
R6
174k
R7
VC
VC
20mV
–20mV
– 17 –
iPD2)}
VH
VL
FOCUS
PHASE
COMPENSATION
VIN
VIN > VH L
VIN < VH H
VIN > VL H
VIN < VL L
FOH
FOL
SENS
SELECTOR
100k
R8
VC
25
26
2
7
1
6
FE_M
SENS1
SENS2
FEO
FEI
FE_O
10k
R9
GND
100k
R10
10k
R11
CXA1992BR
GND
2200p
DRIVER
C1