Read Amplifier. XR-3470B Datasheet

XR-3470B Amplifier. Datasheet pdf. Equivalent


Exar XR-3470B
XR-3470A/3470B
Floppy Disk Read Amplifier
GENERAL DESCRIPTION
The XR-3470Al3470B is read amplifier system designed
primarily for use in a floppy disk drive system. It is de-
signed to perform the complete readback function, by
accepting the readback signal from a magnetic head
and converting it into digital output pulses. To perform
this function, the circuit contains a high-frequency am-
plifier, an active differentiator, a zero-crossing detector,
and a time domain filter.
The XR-3470Al3470B is suited for systems with data
transfer rates up to 3 megabaud. High input sensitivity
allows operation with signal levels as low as 1.4 mV pp,
which gives it the flexibility to be used for single or dou-
ble density floppy disk systems.
The XR-3470Al3470B offers improvements (over the
standard 3470) of lower peak shift and power part-to-
part input amplifier gain variations.
The XR-3470Al3470B, available in an 18 Pin DIP, is
powered by + 5 and + 12 volt power supplies.
FUNCTIONAL BLOCK DIAGRAM
r
AMPLIFIER
INPUTS
L
OFF}:
DECOUPLING
L
GROUND
r
.1TONE-SHOT
COMPONENTS
L
r
DIGITIZER
ONE-SHOT
COMPONENTS
L
l
AMPLIFIER
OUTPUTS
J
I
ACTIVE
DIFFERENTIATOR
INPUTS
-1
l
DIFFERENTIATOR
COMPONENTS
J
DATA
OUTPUT
FEATURES
Complete Floppy Disk Read Amplifier
Low Input Voltage detection
Low Peak Shift 3470A
3470B
Low Amplifier Gain Variation
High Amplifier Frequency Response
1.4 mV pp
2% Max
4% Max
100 VIV Min
130 VIV Max
10 MHz, Min.
ORDERING INFORMATION
Part Number
Package
XR-3470ACN
XR-3470ACP
XR-3470BCN
XR-3470BCP
Ceramic
Plastic
Ceramic
Plastic
Operating Temperature
O°C to + 70°C
O°C to + 70°C
O°C to + 70°C
O°C to + 70°C
APPLICATIONS
Single/Double Density Floppy Disk Read Amplifier
Magnetic Read Amplifier
ABSOLUTE MAXIMUM RATINGS
Power Supply Voltage (Pin 11)
Power Supply Voltage (Pin 18)
Input Voltage (Pins 1 and 2)
Output Voltage (Pin 10)
Operating Ambient Temperature
Storage Temperature
Operating Junction Temperature
7 V dc
16 V dc
-2V to +7 V dc
-2V to +7 V dc
O°C to + 70°C
- 65°C to + 150°C
150°C
SYSTEM DESCRIPTION
The XR-3470Al3470B contains four internal signal
blocks. Their functions are as follows: Input Amplifier -
This section receives an input directly from the mag-
netic head. It provides a nominal gain of 110 VIV, with
gain select pins to reduce gain or tailor it for ac re-
sponse. The amplifier has differential inputs and out-
puts. Active Differentiator - This circuit differentiates the
signal from the amplifier which causes a zero-crossing
for each peak of the readback signal. The time constant
and response of this section is externally set. Zero-
Crossing Detector - This function is performed by a volt-
age comparator. It produces complementary outputs
for the internal digital section. Digital Section - This sec-
tion consists of 2 one-shots and other control circuitry.
The one-shots are used to prevent false outputs, and
set the output pulse width.
4-21


XR-3470B Datasheet
Recommendation XR-3470B Datasheet
Part XR-3470B
Description Floppy Disk Read Amplifier
Feature XR-3470B; XR-3470A/3470B Floppy Disk Read Amplifier GENERAL DESCRIPTION The XR-3470Al3470B is read amplifier.
Manufacture Exar
Datasheet
Download XR-3470B Datasheet




Exar XR-3470B
XR·3470A/3470B
ELECTRICAL CHARACTERISTICS
Test Conditions: TA = aoc to 7aoC; VCC1 = 4.75V to 5.25V; VCC2 = 1av to 14V; unless otherwise specified.
SYMBOL
PARAMETERS
GAIN AMPLIFIER SECTION
AVD
liB
VICM
VID
VOD
10
lOS
RI
RO
BW
Differential Voltage Gain
Input Bias Current
Input Common Mode Range
Linear Operation
Differential Input Voltage Linear
Operation
Output Voltage Swing Differential
Output Source Current, Toggled
Output Sink Current
Small Signal Input Resistance
Small Signal Output Resistance
Single-Ended
Bandwidth, - 3 dB
CMRR
Common Mode Rejection Ratio
MIN
100
-
-0.1
-
3.0
-
2.8
100
-
10.0
50
PSSR1
VCC1 Supply Rejection Ratio
PSSR2
VCC2 Supply Rejection Ratio
VDO
VCO
Differential Output Offset
Common Mode Output Offset
en Differential Noise Voltage
Referred to Input
ACTIVE DIFFERENTIATOR SECTION
10D Differentiator Output Sink Current
PS Peak Shift 3470A
3470B
50
60
-
-
-
1.0
-
-
RID
ROD
Differentiator Input Resistance
Differential
Differentiator Output Resistance
Differential
DIGITAL SECTION
-
-
VOH
Output Voltage High Logic Level
2.7
VOL
Output Voltage Low Logic Level
-
tTLH
tTHL
t1A,B
Et1
t2
Et2
ICC1
ICC2
Output Rise Time
Output Fall Time
Timing Range Mono #1
Timing Accuracy Mono #1
Timing Range Mono #2
Timing Accuracy Mono #2
VCC1, Power Supply Current
VCC2, Power Supply Current
-
-
500
85
150
85
-
-
1. Accuracy guaranteed for R1 and C1 in range
1.5 kO < R1 < 10 kO
150 pF < C1 < 680 pF
TYP MAX UNIT
CONOITIONS
110 130
VN f = 200 kHz, VID = 5 mV (RMS)
-10 -25
/LA
- 1.5 V 5% max THD
- 25 mVpp 5% max THD
4.0 -
V pp
8.0 -
rnA
4-
rnA Pins 16 and 17
250 -
kO TA = 25°C
15 -
0 TA = 25°C, VCC1 = 5V
VCC2 = 12V
-
-
MHz
TA = 25°C, VCC1 = 5V
VID = 2 mV (RMS), VCC2 = 12V
--
dB TA = 25°C, f = 100 kHz
AVD = 40 dB, VCC1 = 5V
VIN = 200 mV pp, VCC2 = 12V
--
dB TA = 25°C, AVD = 40 dB
--
4.75 < VCC1 < 5.25, VCC2 = 12V
dB TA = 25°C, AVD = 40 dB
10 < VCC2 < 14V, VCC1 = 5V
- 0.4 V TA = 25°C, VID = VIN = OV
3.0 -
V VID = VIN = OV
Differential and Common Mode
15 -
/LV BW = 10 Hz to 1.0 MHz
(RMS) TA = 25°C
1.4 -
- 2.0
- 4.0
30 -
40 -
rnA Pins 12 and 13, VOD = VCC1
% f = 250 kHz, VID = 1V pp
% ICAP = 500/LA
VCC1 = 5V, VCC2 = 12V
See Figure 2
kO TA = 25°C
0 TA = 25°C
--
V Pin 10, VCC1 = 4.75V
10H = - 0.4 rnA, VCC2 = 12V
- 0.5 V Pin 10, VCC1 = 4.75V
10L = 8.0 rnA, VCC2 = 12V
- 20 ns Pin 10
- 25 ns Pin 10
4000 ns t1A,t1B
- 115 % R1 = 6.4 kO, C1 = 200 pF (Note 1)
-
1000
ns
- 115 % R2 = 1.6 kG, C2 = 200 pF (Note 2)
25 40
rnA
3 10 rnA
2. Accuracy guaranteed for R2 and C2 in range
1.5 kO < R2 < 10 kO
100 pF < C2 < 800 pF
4-22



Exar XR-3470B
PS = V2 (tPS1 - tPS2 ) at Pin 10
tPS1 + tPS2
ICAP = current into Pin 12
Figure 2.
XR·3470A/3470B
42 K
3.6 K
13 K
13 K
1K 1K
14
15
tVCCI
Figure 3. Active Differentiator and Zero Crossing Detector
R/W
HEAD
DIGITAL
PULSE OUT
COMP
'RpS IS USED TO ADJUST FOR MINIMUM PEAK SHIFT.
V+ V+
Figure 4. Generalized Circuit Connection for Floppy DIsk Read System
4-23







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