cxa1992ar Sony Electronics, cxa1992ar Datasheet - Page 29

• Manufacturer Part Number: cxa1992ar
• Description: Rf Signal Processing Servo Amplifier
• Manufacturer: Sony Electronics

Commands
The input data to operate this IC is configured as 8-bit/12-bit data; however, below, this input data is
represented by 2-digit hexadecimal numerals in the form $XX, where X is a hexadecimal numeral between 0
and F/$XXX for 12-bit.
Commands for the CXA1992AR can be broadly divided into four groups ranging in value from $0X, $1X, $2X,
$3XX.
1. $0X (FZC at SENS1 pin (Pin 25), H (Hi-Z) at SENS2 pin (Pin 26))
These commands are related to focus servo control.
The bit configuration is as shown below.
Four focus related switches exist: FS1, FS2, FS4 and DFCT.
$00
$02
$03
By alternating the commands between $02 and $03, the focus search voltage can be constructed. (Fig. 2)
Fig. 2. Constructing the search voltage by alternating between $02 and $03. (Voltage at Pin 6)
D7
0
When FS1 = 0, Pin 8 is charged to (22µA – 11µA)
If, in addition, FS2 = 0, this voltage is no longer transferred, and the output at Pin 6 becomes 0V.
From the state described above, the only FS2 becomes 1. When this occurs, a negative signal is output
to Pin 6. This voltage level is obtained by equation 1 below.
(22µA – 11µA)
The SRCH DOWN speed can be increased by the charge up circuit.
From the state described above, FS1 becomes 1, and a current source of +22µA is split off.
Then, a CR charge/discharge circuit is formed, and the voltage at Pin 8 decreases with the time as
shown in Fig. 1 below.
This time constant is obtained with the 50k resistance and an external capacitor.
D6
0
50k
D5
0
Fig. 1. Voltage at Pin 8 when FS1 goes from 0
0V
$
resistance between Pins 6 and 7
00 02
D4
0
0V
03
FS4
50k
D3
02
– 29 –
D2
—
50k = 0.55V.
03
FS2
.... Equation 1
D1
02
00
FS1
D0
1
CXA1992AR