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WS7107CPL Schematic ( PDF Datasheet ) - Wing Shing Computer Components

Teilenummer WS7107CPL
Beschreibung 3 Digit LCD/LED Display A/D Converters
Hersteller Wing Shing Computer Components
Logo Wing Shing Computer Components Logo 




Gesamt 14 Seiten
WS7107CPL Datasheet, Funktion
3 1/2Digit LCD/LED Display A/D
Converters
WS7106 / WS7107
Features
Guaranteed Zero Reading for 0V Input on All Scales
True Polarity at Zero for Precise Null Detection
• True Differential Input and Reference, Direct Display
Drive- LCD WS7106, LED WS7107
• On Chip Clock and Reference
• Low Noise - Less Than 15µVP-P
• No Additional Active Circuits Required
• Low Power Dissipation - Typically Less Than 10mW
Ordering Information
Description
The WS7106 and WS7107 are high performance, low
power, 31/2 digit A/D converters. Included are seven seg-
ment decoders, display drivers, a reference, and a clock.
The WS7106 is designed to interface with a liquid crystal dis-
play (LCD) and includes a multiplexed backplane drive; the
WS 7107 will directly drive an instrument size light emitting
diode (LED) display.
The WS7106 and WS 7107 bring together a combination of
high accuracy, versatility, and true economy.True differential
inputs and reference are useful in all systems, but give the
desiger an uncommon advantage when measuring load
cells, strain gauges and other bridge type transducers.
Finally, the true economy of single power supply operation
(WS7106), enables a high performance panel meter to built
with the addition of only 10 passive compoents and a disply.
PART NO.
WS7106CPL
WS7107CPL
TEMP.
RANGE (oC)
0 to 70
0 to70
PACKAGE
40Ld PDIP
40Ld PDIP
PKG. NO.
E40.6
E40.6
Pinouts
WS7106CPL (PDIP)
WS7107CPL (PDIP)
V+
D1
C1
B1
(1’ s) A1
F1
G1
E1
D2
C2
B2
(10’ s)
A2
F2
E2
D3
B3
(100’ s)
F3
E3
(1000) AB4
(MINUS) POL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40 OSC 1
39 OSC 2
38 OSC 3
37 TEST
36 REF HI
35 REF LO
34 CREF+
33 CREF-
32 COMMON
31 IN HI
30 IN LO
29 A-Z
28 BUFF
27 INT
26 V-
25 G2 (10’ s)
24 C3
23 A3 (100’ s)
22 G3
21 BP/GND
Wing Shing Computer Components Co., (H.K.)Ltd.
Homepage: http://www.wingshing.com
Tel:(852)2341 9276 Fax:(852)2797 8153






WS7107CPL Datasheet, Funktion
Differential Reference
The reference voltage can be generated anywhere within the
power supply voltage of the converter. The main source of com-
mon mode error is a roll-over voltage caused by the reference
capacitor losing or gaining charge to stray capacity on its
nodes. If there is a large common mode voltage, the reference
capacitor can gain charge (increase voltage) when called up to
de-integrate a positive signal but lose charge (decrease volt-
age) when called up to de-integrate a negative input signal.
This difference in reference for positive or negative input voltage
will give a roll-over error. However, by selecting the reference
capacitor such that it is large enough in comparison to the stray
capacitance, this error can be held to less than 0.5 count worst
case. (See Component Value Selection.)
Analog COMMON
This pin is included primarily to set the common mode
voltage for battery operation (WS7106) or for any system
where the input signals are floating with respect to the power
supply. The COMMON pin sets a voltage that is approxi-
mately 2.8V more negative than the positive supply. This is
selected to give a minimum end-of-life battery voltage of
about 6V. However, analog COMMON has some of the
attributes of a reference voltage. When the total supply
voltage is large enough to cause the zener to regulate (>7V),
the COMMON voltage will have a low voltage coefficient
(0.001%/V), low output impedance (15), and a
temperature coefficient typically less than 80ppm/oC.
The limitations of the on chip reference should also be
recognized, however. With the WS7107, the internal heating
which results from the LED drivers can cause some
degradation in performance. Due to their higher thermal resis-
tance, plastic parts are poorer in this respect than ceramic.
The combination of reference Temperature Coefficient (TC),
internal chip dissipation, and package thermal resistance can
increase noise near full scale from 25µV to 80µVP-P. Also the
linearity in going from a high dissipation count such as 1000
(20 segments on) to a low dissipation count such as 1111(8
segments on) can suffer by a count or more. Devices with a
positive TC reference may require several counts to pull out of
an over-range condition. This is because over-range is a low
dissipation mode, with the three least significant digits
blanked. Similarly, units with a negative TC may cycle
between over-range and a non-over-range count as the die
alternately heats and cools. All these problems are of course
eliminated if an external reference is used.
The WS7106, with its negligible dissipation, suffers from
none of these problems. In either case, an external
reference can easily be added, as shown in Figure 4.
Analog COMMON is also used as the input low return during
auto-zero and de-integrate. If IN LO is different from analog
COMMON, a common mode voltage exists in the system
and is taken care of by the excellent CMRR of the converter.
However, in some applications IN LO will be set at a fixed
known voltage (power supply common for instance). In this
application, analog COMMON should be tied to the same
point, thus removing the common mode voltage from the
converter. The same holds true for the reference voltage. If
reference can be conveniently tied to analog COMMON, it
WS7106 / WS7107
should be since this removes the common mode voltage
from the reference system.
Within the lC, analog COMMON is tied to an N-Channel FET
that can sink approximately 30mA of current to hold the
voltage 2.8V below the positive supply (when a load is trying
to pull the common line positive). However, there is only
10µA of source current, so COMMON may easily be tied to a
more negative voltage thus overriding the internal reference.
V+
V
REF HI
REF LO
WS7106
WS7107
6.8V
ZENER
IZ
V-
FIGURE 4A.
V+
V
WS7106
WS7107
REF HI
20k
REF LO
COMMON
6.8k
ICL8069
1.2V
REFERENCE
FIGURE 4B.
FIGURE 4. USING AN EXTERNAL REFERENCE
TEST
The TEST pin serves two functions. On the WS7106 it is
coupled to the internally generated digital supply through a
500resistor. Thus it can be used as the negative supply for
externally generated segment drivers such as decimal points
or any other presentation the user may want to include on
the LCD display. Figures 5 and 6 show such an application.
No more than a 1mA load should be applied.
V+ 1M
WS7106
TO LCD
DECIMAL
POINT
BP
TEST
21
37
TO LCD
BACKPLANE
FIGURE 5. SIMPLE INVERTER FOR FIXED DECIMAL POINT
6

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WS7107CPL pdf, datenblatt
Typical Applications (Continued)
OSC 1 40
OSC 2 39
OSC 3 38
TEST 37
REF HI 36
REF LO 35
CREF 34
CREF 33
COMMON 32
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V - 26
G2 25
C3 24
A3 23
G3 22
GND 21
TO PIN 1
100k
100pF
0.1µF
0.47µF
47k
0.22µF
TO DISPLAY
V+
The resistor values within the bridge are determined by the desired
sensitivity.
FIGURE 17. WS 7107 MEASUREING RATIOMETRIC VALUES OF
QUAD LOAD CELL
V+
O /RANGE
U /RANGE
TO LOGIC
VCC
1 V+
2 D1
3 C1
4 B1
5 A1
6 F1
7 G1
8 E1
9 D2
10 C2
11 B2
12 A2
13 F2
14 E2
15 D3
16 B3
17 F3
18 E3
19 AB4
20 POL
OSC 1 40
OSC 2 39
OSC 3 38
TEST 37
REF HI 36
REF LO 35 TO
CREF
34
LOGIC
GND
CREF 33
COMMON 32
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V- 26 V-
G2 25
C3 24
A3 23
G3 22
BP 21
CD4023 OR
74C10
CD4077
FIGURE 19. CIRCUIT FOR DEVELOPING UNDERRANGE AND
OVERRANGE SIGNAL FROM WS7106 OUTPUTS
WS7106 / WS7107
OSC 1 40
OSC 2 39
TO PIN 1
100k
OSC 3 38
TEST 37
REF HI 36
100pF
SCALE
FACTOR
ADJUST
REF LO 35
CREF
34
0.1µF
CREF 33
COMMON 32
100k1M
100k220k
22k
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V - 26
0.01µF
ZERO
ADJUST
0.47µF
47k
SILICON NPN
MPS 3704 OR
SIMILAR
9V
0.22µF
G2 25
C3 24
A3 23
TO DISPLAY
G3 22
BP 21
TO BACKPLANE
A silicon diode-connected transistor has a temperature coefficient of
about -2mV/oC. Calibration is achieved by placing the sensing
transistor in ice water and adjusting the zeroing potentiometer for a
000.0 reading. The sensor should then be placed in boiling water
and the scale-factor potentiometer adjusted for a 100.0 reading.
FIGURE 18. WS 7106 USED AS A DIGITAL CENTIGRADE
THERMOMETER
+5V
TO LOGIC
VCC
12k
The LM339 is required to
ensure logic compatibility
with heavy display loading.
+-
O /RANGE
U /RANGE
CD4023 OR
74C10
+-
+-
-
+
1 V+
2 D1
3 C1
4 B1
5 A1
6 F1
7 G1
8 E1
9 D2
10 C2
11 B2
12 A2
13 F2
14 E2
15 D3
16 B3
17 F3
18 E3
19 AB4
20 POL
33k
OSC 1 40
OSC 2 39
OSC 3 38
TEST 37
REF HI 36
REF LO 35
CREF 34
CREF 33
COMMON 32
IN HI 31
IN LO 30
A-Z 29
BUFF 28
INT 27
V- 26
G2 25
C3 24
A3 23
G3 22
BP 21
V-
FIGURE 20. CIRCUIT FOR DEVELOPING UNDERRANGE AND
OVERRANGE SIGNALS FROM WS7107 OUTPUT
12

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