LSI/CSI
UL
®
LS7083/7084
(631) 271-0400 FAX (631) 271-0405
January 2003
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747
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
DESCRIPTION:
The LS7083 and LS7084 are CMOS quadrature clock con-
verters. Quadrature clocks derived from optical or magnetic
encoders, when applied to the A and B inputs of the LS7083/
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 encoder.
INPUT/OUTPUT DESCRIPTION:
RBIAS
(Pin 1)
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
DD
(Pin 2)
Supply Voltage positive terminal.
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.)
7083/84-012703-1
PIN ASSIGNMENT - TOP VIEW
LSI
LS7083
LSI
LS7084
FIGURE 1
RBIAS
1
8
7
6
UPCK
V
DD(+V)
2
V
SS(-V)
3
A 4
DNCK
x4/x1
5
B
RBIAS
V
DD(+V)
1
2
8
7
6
CLK
UP/DN
x4/x1
V
SS(-V)
3
A
4
5
B
LS7083 - DNCK
(Pin 7)
In LS7083, this is the DOWN Clock Output. This output con-
sists 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 input 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 in-
put.
LS7084 - 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 re-
quires that the counter interfacing with LS7084 counts on the
rising edge of the CLK pulses.
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