TC820CLW データシートの表示（PDF） - TelCom Semiconductor Inc => Microchip
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TC820CLW
TelCom Semiconductor Inc => Microchip
TC820CLW Datasheet PDF : 22 Pages
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TC820
3-3/4 A/D CONVERTER WITH
FREQUENCY COUNTER
AND LOGIC PROBE
LOGIC HIGH
LOGIC LOW
OVERRANGE PKHOLD
LOW BATT
VDD
NC
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17
22kΩ
S1a
VDD
VIN
S1b
GND
FREQ S1c
VDD
S1d
LOGIC
S1e
DGND
TO
SWITCH
S1a
24
TO SWITCH
S2
18
100kΩ
33
0.01µF
32
16
CHANGE
RANGE
COM
VDD
19
20
21
DP3
S2
DP2
DP1
NO DP
FREQ/
VOLTS
LOGIC
VI+N
VI–N
DGND
TC820
VR+ EF
VR– EF
COM
VDD
VSS
RANGE/FREQ
BUZ OUT
DP0/LO
BUZ IN
DP1/HI
OSC1
PK HOLD
OSC2 OSC3 VBUFF CAZ VINT CR+EF CR– EF
37
38 39 34
35
36 28 29
470
40kHz kΩ
100
kΩ
0.47
µF
0.2 0.1
µF µF
NC
22M Ω
30
2kΩ
VREF = 200mV
31
27
40
+
9V
26 –
DGND
+
1µF
22
PIEZO
BUZZER
DGND
23
25
VDD
VDD
VDD
NOTE:
Pin numbers are for
40-pin package.
Figure 1. Typical Operating Circuit
GENERAL THEORY OF OPERATION
Dual-Slope Conversion Principles
The TC820 analog-to-digital converter operates on the
principle of dual-slope integration. An understanding of the
dual-slope conversion technique will aid the user in follow-
ing the detailed TC820 theory of operation following this
section. A conventional dual-slope converter measurement
cycle has two distinct phases:
(1) Input Signal Integration
(2) Reference Voltage Integration (Deintegration)
Referring to Figure 2, the unknown input signal to be
converted is integrated from zero for a fixed time period
(t INT), measured by counting clock pulses. A constant
reference voltage of the opposite polarity is then integrated
until the integrator output voltage returns to zero. The
reference integration (deintegration) time (TDEINT) is then
directly proportional to the unknown input voltage (VIN).
In a simple dual-slope converter, a complete conver-
sion requires the integrator output to "ramp-up" from zero
and "ramp-down" back to zero. A simple mathematical
equation relates the input signal, reference voltage, and
integration time:
3-156
ANALOG
INPUT
SIGNAL
C
INTEGRATOR
R
–
–COMPARATOR
+
+
REF
VOLTAGE
SWITCH
DRIVER
PHASE
CONTROL
CONTROL
LOGIC
POLARITY CONTROL
CLOCK
DISPLAY
COUNTER
VIN = VFULL SCALE
VIN = 1.2 VFULL SCALE
FIXED
SIGNAL
INTEGRATE
TIME
VARIABLE
REFERENCE
INTEGRATE
TIME
Figure 2. Basic Dual-Slope Converter
TELCOM SEMICONDUCTOR, INC.
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