LS7083 & LS7084
Encoder to Counter Interface Chips
Description:
These devices allow incremental shaft encoders to drive standard up/down
counters. Connect the encoder quadrature outputs to the A and B inputs. The
LS7083
outputs can connect directly to the up and down clock inputs of
counters such as 74193 or 40193. The
LS7084
outputs can connect directly
to the Clock and Up/Dn inputs of counters such as 4516 or 74169.
Rbias
5 Ch. B
Channel
4 +5v
4
B +5V
3 Ch. A
Channel
A
2
Ground
1 Gnd
1
2
3
4
Optical Encoder
+5V
Gnd
A in
LS7083
8
7
6
5
UpClk out
5
4
DnClk out
Cascadable
X4/X1 input
Up/Dn
+5V
Counter
B in
74193
type
Features:
脴
脴
脴
脴
脴
脴
脴
Top View
X4 or X1 resolution multiplication.
TTL and CMOS compatible.
Low power (micro-amps).
8-pin DIP or SOIC package.
No external clocks required.
Drive standard Up/Dn counters.
Monolithic CMOS.
Rbias
5 Ch. B
Channel
4 +5v
B +5V
Channel
3 Ch. A
A
2
1 Ground
1 Gnd
1
2
3
4
Optical Encoder
+5V
Gnd
A in
LS7084
8
7
6
5
Clock out
15
4516
Up/Dn out
10
type
Cascadable
X4/X1 input
Up/Dn
+5V
Counter
B in
Example Circuit
Pin Descriptions:
Pin 1 (Rbias input):
Connect a 0.1 碌F bypass capacitor and resistor to ground for the internal current mirror which feeds the two internal 2-axis one-shots. The resistor value
sets the width of the low-true clock outputs. A typical value is 300kOhm which sets the output pulse width to 1碌s and max A,B frequency to 250kHz. Minimum
resistor value is 50kOhm. See the Rbias table (next page) for other values. The chip's current consumption is inversely proportional to this resistance. Typical
current is 40碌A(chǔ) @ 100KOhm and 6碌A(chǔ) @ 2MegOhm.
Pins 4 & 5 (A & B inputs):
Connect to the A and B quadrature outputs of the encoder. Both inputs have debounce filters. Minimum pulse width is set at 160ns. There is no maximum limit.
Input current is less than 1 碌A(chǔ). The A and B inputs can be swapped to reverse the direction of the external counters.
Pin 6 (X4/X1 input):
A high level applied to this input selects X4 mode, a low level selects the X1 mode. Input current is less than 1碌A(chǔ). Do not let this input float. In X4 mode, a clock
pulse is generated for every transition of the A or B input. Note that there are 4 transitions per cycle of quadrature code. Thus, a 500 cycle/rev encoder will
produce 2000 counts/rev in X4 mode. In X1 mode, only one clock is generated per quadrature cycle.
LS7083 pin 7 (Down Clock output):
Normally high, low-true. The low level pulse width is set by pin 1. Down counts are enabled only when B leads A (clockwise rotation). In X4 mode, one pulse
is generated for each A/B state change. In X1 mode, one pulse is generated per quadrature cycle.
LS7084 pin 7 (Up/Down Clock output):
This output steers the external counter up or down. High = Up (A leads B), Low = Down (B leads A).
LS7083 pin 8 (Up Clock output):
Normally high, low-true. The low level pulse width is set by pin 1. Up counts are enabled only when A leads B (counter-clockwise rotation). In X4 mode, one
pulse is generated for each A/B state change. In X1 mode, one pulse is generated per quadrature cycle.
LS7084 pin 8 (Clock output):
Normally high, low-true. The low level pulse width is set by pin 1. In X4 mode, one pulse is generated for each A/B state change regardless of count direction.
In X1 mode, one pulse is generated per quadrature cycle. The external counter should count on the rising (high-going) edge of this output.
Surface Mount Package:
The 8-pin SOIC package has the same pin-out as the DIP version shown above.
Absolute Maximum Ratings:
Parameter
Operating temperature
Storage temperature
Voltage at any input
Supply voltage (Vcc)
Resistor
100kOhm
300kOhm
500kOhm
2MegOhm
10MegOhm
Min.
0
-65
-.5
Max.
70
150
VCC+.5
10.5
Units
擄C
擄C
Volts
Volts
DC Electrical Characteristics for 5V Operation:
Units
Notes
Volts
碌A(chǔ)
A,B = 0Hz
Rbias=300k
X4/X1 logic low
1.4
Volts
X4/X1 logic high
3.7
Volts
A,B logic low
0.6
Volts
A,B logic high
3.3
Volts
Low output current
1.75
mA
Vout = 0.4V
High output current
1.0
mA
Vout = 4.75V
脴
Use standard CMOS levels when operating with higher supply
voltages up to 10.5 Volts.
Parameter
Supply voltage
Supply current
Min.
4.75
-
Max.
10.5
8.0
RBias Resistor Value vs. Timing:
Pulse Width
400ns
1碌s
1.4碌s
5碌s
25碌s
Max A,B Freq
625kHz
250kHz
180kHz
50kHz
10kHz
phone: 360.260.2468
l
sales: 800.736.0194
l
fax: 360.260.2469
email: sales@usdigital.com
l
website: www.usdigital.com
11100 ne 34th circle
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vancouver, washington 98682 USA
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