CXA2542AQ
Focus Error Amplifier
R3
58k
R7
174k
RF
RF
R5
32k
V2
V1
VB
PD2 37
B + D
FEO
FEI
48
1
PD2 IV AMP
R2
R10
10k
FE AMP
VC
VC
58k
R4
32k
VA
PD1 IV AMP
36
PD1
A + C
R9
10k
C1
2200p
R6
GND GND
174k
VCC
R1
16k
FE_M
FE_O
6
5
R11
100k
R8
100k
×1 ×2 ×4 ×8 ×16 ×32
FOCUS
PHASE
COMPENSATION
DRIVER
VC
VIN > VH L
VIN < VH H
×32
VC
25mV/STEP
RESET : IFB1 to IFB6 ON
VH
FOH
SENS1
SENS2
23
24
VEE
20mV
SENS
SELECTOR
VIN
VC
FOL
VL
VIN > VL H
VIN < VL L
–20mV
VC
The focus error amplifier calculates the difference between outputs VA and VB of the RF I-V amplifier, and
outputs current-voltage converted voltage of the photodiode (A + C – B – D).
The FEO output voltage:
174kΩ
32kΩ
VFEO =
(VA – VB)
174kΩ
32kΩ
=
{(–58kΩ × iPD1) – (–58kΩ × iPD2)}
= 315.4kΩ (iPD2 – iPD1)
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.
– 17 –
SONY [ SONY CORPORATION ]
