WS7106 Datasheet, PDF (8/14 Pages) Wing Shing Computer Components – 3 1/2 Digit LCD/LED Display A/D Converters

WS7106 / WS7107
a
a
a
a
fb
f bf b
gc
g
g
b
ec
ec ec
d
d
d
7
SEGMENT
DECODE
7
SEGMENT
DECODE
7
SEGMENT
DECODE
TYPICAL SEGMENT OUTPUT
V+
0.5mA
8mA
TO
SEGMENT
DIGITAL GROUND
LATCH
1000’s
100’s
10’s
1’s
COUNTER COUNTER COUNTER COUNTER
TO SWITCH DRIVERS
FROM COMPARATOR OUTPUT
V+
CLOCK
†
÷4
LOGIC CONTROL
† THREE INVERTERS
ONE INVERTER SHOWN FOR CLARITY
40
39
38
OSC 1
OSC 2
OSC 3
1
37
500Ω
27
V+
TEST
DIGITAL
GROUND
FIGURE 8. WS 7107 DIGITAL SECTION
System Timing
Figure 9 shows the clocking arrangement used in the
WS7106 and WS7107 . Two basic clocking arrangements
can be used:
1. Figure 9A. An external oscillator connected to pin 40.
2. Figure 9B. An R-C oscillator using all three pins.
The oscillator frequency is divided by four before it clocks the
decade counters. It is then further divided to form the three
convert-cycle phases. These are signal integrate (1000
counts), reference de-integrate (0 to 2000 counts) and
auto-zero (1000 to 3000 counts). For signals less than full
scale, auto-zero gets the unused portion of reference
de-integrate. This makes a complete measure cycle of 4,000
counts (16,000 clock pulses) independent of input voltage.
For three readings/second, an oscillator frequency of 48kHz
would be used.
To achieve maximum rejection of 60Hz pickup, the signal
integrate cycle should be a multiple of 60Hz. Oscillator
frequencies of 240kHz, 120kHz, 80kHz, 60kHz, 48kHz,
40kHz, 33¹/₃kHz, etc. should
tion, Oscillator frequencies of
be selected. For 50Hz rejec-
200kHz, 100kHz, 66²/₃kHz,
50kHz, 40kHz, etc. would be suitable. Note that 40kHz (2.5
readings/second) will reject both 50Hz and 60Hz (also
400Hz and 440Hz).
INTERNAL TO PART
÷4
CLOCK
40
39
38
GND WS7107
TEST WS7106
FIGURE 9A.
INTERNAL TO PART
÷4
CLOCK
40
39
38
R
C
RC OSCILLATOR
FIGURE 9B.
FIGURE 9. CLOCK CIRCUITS
8