UL
®
LSI/CSI
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
RBIAS
V
DD
(+V )
V
SS
(-V)
A
1
2
3
4
LS7083
LS7084
(631) 271-0400 FAX (631) 271-0405
January 2009
A3800
QUADRATURE CLOCK CONVERTER
FEATURES:
• x1 and x4 mode selection
• Up to 16MHz output clock frequency
• Programmable output clock pulse width
• On-chip filtering of inputs for optical or
magnetic encoder applications.
• TTL and CMOS compatible I/Os
• +4.5V to +10V operation (V
DD
- V
SS
)
• LS7083, LS7084 (DIP);
LS7083-S, LS7084-S (SOIC) -
See Figure 1
Applications:
• Interface incremental encoders to Up / Down Counters
(See Figure 6A and Figure 6B)
• Interface rotary encoders to Digital Potentiometers
(See Figure 7)
DESCRIPTION
The
LS7083
and
LS7084
are CMOS quadrature clock convert-
ers. Quadrature clocks derived from optical or magnetic encod-
ers, when applied to the A and B inputs of the
LS7083
or
LS7084,
are converted to strings of Up Clocks and Down Clocks
(LS7083) or to a Clock and an Up/Down direction control
(LS7084). These outputs can be interfaced directly with standard
Up/Down counters for direction and position sensing of the en-
INPUT/OUTPUT DESCRIPTION:
PIN ASSIGNMENT - TOP VIEW
LSI
LS7083
LSI
8
7
6
5
UPCK
DNCK
x4/x1
B
ue
RBIAS
1
V
DD
(+V)
V
SS
(-V)
A
2
3
4
d
tin
LS7084
8
7
6
5
CLK
UP/DN
x4/x1
B
co
n
is
RBIAS
(Pin 1)
Input for external component connection. A resistor connected
between this input and VSS adjusts the output clock pulse width
(Tow). For proper operation, the output clock pulse width must be
less than or equal to the A, B pulse separation (T
OW
≤
T
PS
).
V
DD
(Pin 2)
Supply Voltage positive terminal.
FIGURE 1
LS7083 - DNCK
(Pin 7)
In LS7083, this is the DOWN Clock Output. This output consists of
low-going pulses generated when A input lags the B input.
LS7084 - UP/DN
(Pin 7)
In LS7084, this is the count direction indication output. When A in-
put leads the B input, the UP/DN output goes high indicating that
the count direction is UP. When A input lags the B input, UP/DN
output goes low, indicating that the count direction is DOWN.
LS7083 - UPCK
(Pin 8)
In LS7083, this is the UP Clock output. This output consists of low-
going pulses generated when A input leads the B input.
LS7084N - CLK
(Pin 8)
In LS7084, this is the combined UP Clock and DOWN Clock output.
The count direction at any instant is indicated by the UP/DN output
(Pin 7).
NOTE:
For the
LS7084,
the timing of CLK and UP/DN requires that
the counter interfacing with
LS7084
counts on the rising edge of the
CLK pulses.
V
SS
(Pin 3)
Supply Voltage negative terminal.
A
(Pin 4)
Quadrature Clock Input A. This input has a filter circuit to validate
input logic level and eliminate encoder dither.
B
(Pin 5)
Quadrature Clock Input B. This input has a filter circuit identical
to input A.
x4/x1
(Pin 6)
This input selects between x1 and x4 modes of operation. A high-
level selects x4 mode and a low-level selects the x1 mode. In x4
mode, an output pulse is generated for every transition at either
A or B input. In x1 mode, an output pulse is generated in one
combined A/B input cycle. (See Figure 2.)
7083/84-011309-1
D
1500
1250
1000
OUTPUT CLOCK PULSE WIDTH, Tow, ns
V
DD
= 5V
30
V
DD
= 5V
25
OUTPUT CLOCK PULSE WIDTH, Tow, µs
V
DD
= 9V
V
DD
= 10V
20
V
DD
= 9V
750
15
V
DD
= 10V
500
10
250
5
100
200
300
400
500
2
4
6
8
10
12
Figure 4. Tow vs RBIAS, k
MODE SELECT
+V
6
2
V
DD
UPCK
LS7083
DNCK
V
SS
3
8
5
+V
16
V
DD
CK-UP
40193
7
4
CK-DN
Figure 5. Tow vs RBIAS, M
d
R
6
x4/x1
4
A
5 B
+V
2
V
DD
CLK
+V
16
V
DD
x4/x1
ENCODER
A CLOCK
B CLOCK
1
R
B
4
5
A
B
ue
A CLOCK
B CLOCK
8
7
15
10
CK
4516
UP/DN
tin
ENCODER
LS7084
UP/DN
V
SS
3
1
R
B
co
n
RBIAS
RBIAS
V
SS
V
SS
8
8
FIGURE 6A. TYPICAL APPLICATION FOR LS7083 IN x4 MODE
FIGURE 6B*. TYPICAL APPLICATION FOR LS7084 WITH X4/X1 MODE SELETION
*See NOTE at bottom right of Page 1
D
is
+5V
A1
10k
10k
1M
1
RBIAS
CLK
U/D
X4/X1
B
8
7
6
5
1 CLK
2
3
4
U/D
A1
DIGITAL
POTENTIOMETER
V
DD
CS
B1
W1
AD5220
8
7
6
5
B1
W1
ROTARY
ENCODER
B
2
3
V
DD
V
SS
A
GND
10k
4 A
LS7084
0.01uF
GND
10k
0.01uF
Part Number:
RE11CT-V1Y12-EF2CS
FIGURE 7. Rotary Encoder Control of Digital Potentiometer
7083/84-011209-4
Embedded System
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