cxa1720q Sony Electronics, cxa1720q Datasheet - Page 14

• Manufacturer Part Number: cxa1720q
• Description: Read/write Amplifier With Built-in Filters For Fdds
• Manufacturer: Sony Electronics

Description of Operation
(1) Read system
Pre-amplifier
Filters
Pin 8
H
H
L
L
Pre-amplifier output
The pre-amplifier amplifies input signals. The voltage gain can be switched between 40 dB and 46 dB,
using Pin 20.
The filters differentiate the signals amplified by the pre-amplifier. The high-band noise components are
attenuated by the low-pass filter. The filters can be switched among four modes, depending on the
settings of Pins 8 and 9. In 1M/outer track mode, the peak frequency f
f
(1.00).
The filters are explained below.
1) Active filter block
Filter Characteristics
The formula for the peak frequency f
The relationship between f01 and f0 in the four modes is as follows:
Note that these filters can be customized.
Customization is explained on pages 17 and 18.
O
for the other three modes is switched by the internal settings of the IC, with f
f
1M/outer track: f
1M/inner track: f
2M/outer track: f
2M/inner track: f
01
= 527/R
Pin 9
H
H
L
L
F
+ 5.8 (kHz)
02
04
01
03
= 1.07
= 2.03
= 1.0
= 1.88
LPF characteristics
1M/outer track mode: Butterworth
1M/inner track mode: Butterworth
2M/outer track mode: Butterworth
2M/inner track mode: Chebyshev 1 dB ripple
f
Q=0.577
OB
Secondary
BPF
=1.2Xf
f
01
CL
f
f
f
R
f
01
01
01
01
Pre-amplifier output
F
: peak frequency in 1M/outer track mode
: filter setting resistance (k )
01
19
for 1M/outer track mode is shown below:
Tertiary
f
Q; variable
CL
LPF
; variable
Table 1
—14—
f
CH
Primary
=5KHz
HPF
Gain; 8.0dB
Amp.
O1
is set by external resistor R
17
16
O1
used as a reference
Filter output A
Filter output B
f
O
1.00
1.07
1.88
2.03
ratio
CXA1720Q
F
.