UL
®
LSI/CSI
V
DD
(+V)
INDX
RBIAS
V
SS
(-V)
A
NC
LS7082N
(631) 271-0400 FAX (631) 271-0405
January 2003
PIN ASSIGNMENT - TOP VIEW
A3800
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
QUADRATURE CLOCK CONVERTER
FEATURES:
• x1, x2 and x4 mode selection
• Up to 16MHz output clock frequency
• INDEX input and output
• UP/DOWN indicator output
• 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
)
• LS7082N (DIP); LS7082N-S (SOIC ) - See Figure 1
DESCRIPTION:
The LS7082N is a CMOS quadrature clock converter. Quad-
rature clocks derived from optical or magnetic encoders, when
applied to the A and B Inputs of the LS7082, are converted to
strings of Up Clocks and Down Clocks. Pulses derived from
the Index Track of an encoder, when applied to the INDX input,
produce absolute position reference pulses which are syn-
chronized to the Up Clocks and Down Clocks. These outputs
can be interfaced directly with standard Up/Down counters for
direction and position sensing of the encoder.
INPUT/OUTPUT DESCRIPTION:
V
DD
(Pin 1)
Supply Voltage positive terminal.
INDX
(Pin 2)
Encoder Index pulses are applied to this input.
RBIAS
(Pin 3)
Input for external component connection. A resistor con-
nected between this input and V
SS
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
SS
(Pin 4
)
Supply Voltage negative terminal.
A
(Pin 5)
Quadrature Clock Input A. This input has a filter circuit to
validate input logic level and eliminate encoder dither.
x2
(Pin 8)
A low level applied to this input selects x2 mode of opera-
tion. See Table 1 for Mode Selection Truth Table and
Figure 2 for Input/Output timing relationship.
B
(Pin 9)
Quadrature Clock Input B. This input has a filter circuit
identical to input A.
7082N-012703-1
1
14
INDX
LSI
2
13
UPCK
3
12
DNCK
LS7082N
4
11
UP/DN
5
10
x4/x1
B
6
9
NC
7
FIGURE 1
8
x2
TABLE 1. MODE SELECTION TRUTH TABLE
x2 Input
0
1
1
x4/x1 Input
Don’t Care
0
1
MODE
x2
x1
x4
x4/x1
(Pin 10)
This input selects between x1 and x4 modes of operation.
See Table 1 for Mode Selection Truth Table and Figure 2
for Input/Output timing relationship.
UP/DN
(Pin 11)
The count direction at any instant is indicated at this out-
put. An UP count direction is indicated by a high, and a
DOWN count direction is indicated by a low (See Figure 2).
DNCK
(Pin 12)
This DOWN Clock output consists of low-going pulses gen-
erated when A input lags the B input (See Figure 2).
UPCK
(Pin 13)
This UP Clock output consists of low-going pulses gener-
ated when A input leads the B input (See Figure 2).
INDX
(Pin 14)
This output consists of low-going pulses generated by
clock transitions at the A input when INDX input is high and
B input is low (See Figure 2).
NOTE:
All unused input pins must be tied to V
DD
or V
SS
.
NOTE
: Vertical axis is output clock pulse width, Tow, ns
1500
1250
1000
V
DD
=10.0V
V
DD
=5V
NOTE
: Vertical axis is output clock pulse width, Tow, µs
30
V
DD
=5V
25
V
DD
=9V
20
V
DD
=9V
750
15
V
DD
=10.0V
500
10
250
5
100
200
300
400
500
2
4
6
8
10
12
Figure 4. Tow vs R
BIAS
, k
Figure 5. Tow vs R
BIAS
, M
+V
8
x2
A CLOCK
B CLOCK
ENCODER
INDEX
2
INDX
INDX
5
9
B
A
10
x4/x1
1
V
DD
UPCK
13
12
DNCK
14
14
5
4
DNCK
RESET
V
SS
RBIAS
3
V
SS
4
8
16
V
DD
+V
UPCK
LS7082N
40193
R
B
FIGURE 6. A TYPICAL APPLICATION IN x4 MODE
The information included herein is believed to be
accurate and reliable. However, LSI Computer Systems,
Inc. assumes no responsibilities for inaccuracies, nor for
any infringements of patent rights of others which may
result from its use.
7082N-012703-4
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