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Электронный компонент: TC811

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3-137
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
TC811
TC811CPL
THOUSANDS
HUNDREDS
TENS
UNITS
4
39
OSC
V
TEST
TO SWITCH DRIVERS
FROM COMPARATOR OUTPUT
CLOCK
7 SEGMENT
DECODE
40
2
OSC1
CONTROL LOGIC
26
500
DATA LATCH
+
BUFF
CREF
RINT
V
+
CAZ
VINT
28
29
27
34
36
35
10
A
31
ZI & A/Z
INT
AZ & DE (
)
32
INT
26
INTEGRATOR
TO
DIGITAL
SECTION
DE (+)
DE
()
DE
(+)
DE ()
ANALOG
COMMON
C REF
+
V IN
+
V IN
V
CINT
VREF
+
VREF
ZI &
A/Z
CREF
+
33
+
LCD SEGMENT DRIVERS
200
BACKPLANE
fOSC
V
VTH
= 1V
V
+
INTERNAL DIGITAL GOUND
LOW
TEMPCO
VREF
COMPARATOR
A/Z
ZI
V+ 3.0V
38
470k
10pF
7 SEGMENT
DECODE
7 SEGMENT
DECODE
21
TYPICAL SEGMENT OUTPUT
INTERNAL DIGITAL GROUND
SEGMENT
OUTPUT
V
+
0.5mA
2mA
6.2V
LCD DISPLAY
+
38
20pF
V
+
V
+
22M
HLDR
70k
A/Z
30
kH
1
FUNCTIONAL BLOCK DIAGRAM
ORDERING INFORMATION
Temp.
Max V
REF
Part No.
Package
Range
Tempco
TC811CKW 44-PQFP
0
C to +70
C 75 ppm/
C
TC811CPL
40-Pin Plastic DIP 0
C to +70
C 75 ppm/
C
3-1/2 DIGIT A/D CONVERTER WITH HOLD AND DIFFERENTIAL
REFERENCE INPUTS
FEATURES
s
Differential Reference Input
s
Display Hold Function
s
Fast Over-Range Recovery, Guaranteed Next
Reading Accuracy
s
Low Temperature Drift Internal
Reference ....................................... 35ppm/
C (Typ)
s
Guaranteed Zero Reading With Zero Input
s
Low Noise ..................................................... 15
V
p-p
s
High Resolution (0.05%) and Wide Dynamic
Range (72 dB)
s
High Impedance Differential Input
s
Low Input Leakage Current ....................... 1pA Typ
10pA Max
s
Direct LCD Drive No External Components
s
Precision Null Detection with True Polarity at Zero
s
Crystal Clock Oscillator
s
Available in DIP, Compact Flat Package or PLCC
s
Convenient 9V Battery Operation with
Low Power Dissipation (600
A Typical, 1mW
Maximum)
TYPICAL APPLICATIONS
s
Thermometry
s
Digital Meters
-- Voltage/Current/Power
-- pH Measurement
-- Capacitance/Inductance
-- Fluid Flow Rate/Viscosity
-- Humidity
-- Position
s
Panel Meters
s
LVDT Indicators
s
Portable Instrumentation
s
Digital Scales
s
Process Monitors
s
Gaussometers
s
Photometers
TC811-7 11/5/96
3-138
TELCOM SEMICONDUCTOR, INC.
GENERAL DESCRIPTION
The TC811 is a low power, 3-1/2 digit, LCD display
analog-to-digital converter. This device incorporates both a
display hold feature and differential reference inputs. A
crystal oscillator, which only requires two pins, permits
added features while retaining a 40-pin package. An addi-
tional feature is an "Integrator Output Zero" phase which
guarantees rapid input overrange recovery.
The TC811 display hold (HLDR) function can be used to
"freeze" the LCD display. The displayed reading will remain
indefinitely as long as HLDR is held high. Conversions
continue but the output data display latches are not updated.
The TC811 also includes a differential reference for easy
ratiometric measurements. Circuits which use the
7106/26/36 can easily be upgraded to include the hold
function with the TC811.
The TC811 has an improved internal zener reference
voltage circuit which maintains the Analog Common tem-
perature drift to 35ppm/
C (typical) and 75ppm/
C (maxi-
mum). This represents an improvement of two to four times
over similar 3-1/2 digit converters, eliminating the need for
a costly, space consuming external reference source.
The TC811 limits linearity error to less than one count on
both the 200mV and the 2.00V full-scale ranges. Rollover
error--the difference in readings for equal magnitude but
opposite polarity input signals--is below
1 count. High
impedance differential inputs offer 1pA leakage currents
and a 10
12
input impedance. The 15
V
p-p
noise perfor-
mance guarantees a "rock solid" reading. The Auto Zero
cycle guarantees a zero display readout for a zero volt input.
The single chip CMOS TC811 incorporates all the active
devices for a 3-1/2 digit analog to digital converter to directly
drive an LCD display. Onboard oscillator, precision voltage
reference and display segment and backplane drivers sim-
plify system integration, reduce board space requirements
and lower total cost. A low cost, high resolution (0.05%)
indicating meter requires only a TC811, an LCD display, five
resistors, six capacitors, a crystal, and a 9V battery. Com-
pact, hand held multimeter designs benefit from the TelCom
Semiconductor small footprint package option.
The TC811 uses a dual slope conversion technique
which will reject interference signals if the converters inte-
gration time is set to a multiple of the interference signal
period. This is especially useful in industrial measurement
environments where 50, 60 and 400Hz line frequency sig-
nals are present.
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
+
to V
) ............................................ 15V
Analog Input voltage (Either Input)
1
..................... V
+
to V
Reference Input Voltage ...................................... V
+
to V
Clock Input ...................................................... TEST to V
+
Power Dissipation
2
(T
A
70
C)
44-Pin Flat Package .........................................1.00W
40-Pin Plastic DIP .............................................1.23W
Operating Temperature Range
Commercial Package (C) ...................... 0
C to +70
C
Industrial Package (I) ........................ 25
C to +85
C
Storage Temperature Range ................ 65
C to +150
C
Lead Temperature (Soldering, 10 sec) ................. +300
C
*Static-sensitive device. Unused devices must be stored in conductive
material. Protect devices from static discharge and static fields. Stresses
above those listed under "Absolute Maximum Ratings" may cause perma-
nent damage to the device. These are stress ratings only and functional
operation of the device at these or any other conditions above those
indicated in the operation sections of the specifications is not implied.
Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
ELECTRICAL CHARACTERISTICS:
V
Supply
= 9V, f
CLOCK
= 32.768kHz, and T
A
= 25
C, unless otherwise noted.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
Input
--
Zero Input Reading
V
IN
= 0V
000.0
000.0
+000.0
Digital
V
FS
= 200mV
Reading
--
Zero Reading Drift
V
IN
= 0V, 0
C
T
A
70
C
--
0.2
1
V/
C
--
Ratiometric Reading
V
IN
= V
REF
, V
REF
= 100mV
999
999/1000
1000
Digital
Reading
NL
Linearity Error
V
FS
= 200mV or 2.000V
1
0.2
+1
Counts
E
R
Roll Over Error
V
IN
= V
IN
+
200mV
1
0.2
+1
Counts
e
N
Noise
V
IN
= 0V, V
FS
= 200mV
--
15
--
V
P-P
I
L
Input Leakage Current
V
IN
= 0V
--
1
10
pA
CMRR
Common-Mode Rejection
V
CM
=
1V, V
IN
= 0V,
--
50
--
V/V
V
FS
= 200mV
3-1/2 DIGIT A/D CONVERTER WITH HOLD AND
DIFFERENTIAL REFERENCE INPUTS
TC811
3-139
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
ELECTRICAL CHARACTERISTICS:
V
Supply
= 9V, f
CLOCK
= 32.768kHz, and T
A
= 25
C, unless otherwise noted.
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
TC
SF
Scale Factor Temperature
V
IN
= 199mV, 0
C
T
A
70
C
--
1
5
ppm/
C
Coefficient
(ext. V
REF
tc = 0ppm)
Analog Common Section
V
CTC
Analog Common
250K
from V+ to Analog Common
--
--
--
--
Temperature Coefficient
0
C
T
A
70
C
--
--
--
--
"C" Commercial
--
35
75
ppm/
C
"I" Industrial
--
35
100
ppm/
C
V
C
Analog Common Voltage
250k
from V+ to Analog Common
2.7
3.05
3.35
Volts
Hold Pin Input Section
Input Resistance
Pin 1 to Pin 37
--
70
--
k
V
IL
Input Low Voltage
Pin 1
--
--
Test +1.5
V
V
IH
Input High Voltage
Pin 1
V
+
1.5
--
--
V
LCD Drive Section
3
V
SD
LCD Segment Drive Voltage
V
+
to V
= 9V
4
5
6
V
P-P
V
SD
LCD Backplane Drive Voltage
V
+
to V
= 9V
4
5
6
V
P-P
Power Supply
I
SUP
Power Supply Current
V
IN
= 0V, V
+
to V
= 9V
--
--
--
--
f
OSC
= 16kHz
--
70
100
A
f
OSC
= 48kHz
--
90
125
A
NOTES: 1. Input voltages may exceed supply voltages when input current is limited to 100
A.
2. Dissipation rating assumes device is mounted with all leads soldered to a printed circuit board.
3. Backplane drive is in phase with the segment drive for "segment off" 180
out of phase for "segment on." Frequency is 20 times the
conversion rate. Average DC component is less than 50mV.
V+
NORMAL PIN
CONFIGURATION
10's
100's
1000's
100's
TC811CPL
(40-PIN PDIP)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
1's
D2
C2
B2
A2
F2
E2
D3
B3
F3
E3
AB4
POL
(MINUS SIGN)
D1
C1
B1
A1
F1
G1
E1
10's
OSC
TEST
V
ANALOG
COMMON
CAZ
OSC2
HLDR
+
REF
V
REF
C
+
REF
C
REF
V
+
IN
V
IN
VBUFF
VINT
V
G
C
A
G
BP
(BACKPLANE)
3
3
3
2
1
NC = NO INTERNAL CONNECTION
27
28
29
30
31
32
33
7
4
3
2
1
NC
TC811CKW
(PQFP)
12
13
14
15
17
18
G
44
43
42
41
39
38
40
COM
16
37
AZ
36
B
UFF
35
INT
34
V
V
V
19
20
21
22
D
26
8
25
9
24
10
23
11
5
6
C
V
TEST
NC
NC
HLDR
+
3
D
2
C
2
B
2
A
2
F
2
E
2
NC
OSC2
OSC1
REF
C
REF
C
C
V
+
2
3
A3
G3
BP
POL
AB4
E3
F3
B3
D1
C1
B1
A
1
F
1
G
1
E
1
+
REF
V
+
REF
IN
V
IN
V
PIN CONFIGURATIONS
3-1/2 DIGIT A/D CONVERTER WITH HOLD AND
DIFFERENTIAL REFERENCE INPUTS
TC811
3-140
TELCOM SEMICONDUCTOR, INC.
3-1/2 DIGIT A/D CONVERTER WITH HOLD AND
DIFFERENTIAL REFERENCE INPUTS
TC811
PIN DESCRIPTION
Pin No.
40-Pin Plastic DIP
Symbol
Description
1
HLDR
Hold pin, logic 1 holds present display reading.
2
D
1
Activates the D section of the units display.
3
C
1
Activates the C section of the units display.
4
B
1
Activates the B section of the units display.
5
A
1
Activates the A section of the units display.
6
F
1
Activates the F section of the units display.
7
G
1
Activates the G section of the units display.
8
E
1
Activates the E section of the units display.
9
D
2
Activates the D section of the tens display.
10
C
2
Activates the C section of the tens display.
11
B
2
Activates the B section of the tens display.
12
A
2
Activates the A section of the tens display.
13
F
2
Activates the F section of the tens display.
14
E
2
Activates the E section of the tens display.
15
D
3
Activates the D section of the hundreds display.
16
B
3
Activates the B section of the hundreds display.
17
F
3
Activates the F section of the hundreds display.
18
E
3
Activates the E section of the hundreds display.
19
AB
4
Activates both halves of the 1 in the thousands display.
20
POL
Activates the negative polarity display.
21
BP
Backplane drive output.
22
G
3
Activates the G section of the hundreds display.
23
A
3
Activates the A section of the hundreds display.
24
C
3
Activates the C section of the hundreds display.
25
G
2
Activates the G section of the tens display.
26
V
Negative power supply voltage.
27
V
INT
Integrator output, connection for C
INT
.
28
V
BUFF
Buffer output, connection for R
INT
.
29
C
AZ
Integrator input, connection for C
AZ
.
30
V
IN
Analog input low.
31
V
IN
+
Analog input high.
32
COM
Analog Common: Internal zero reference.
33
V
REF
Reference input low.
34
C
REF
Negative connection for reference capacitor.
35
C
REF
+
Positive connection for reference capacitor.
36
V
REF
+
Reference input high.
37
TEST
All LCD segment test when pulled high (V
+
).
38
V
+
Positive power supply voltage.
39
OSC
2
Crystal oscillator output.
40
OSC
1
Crystal oscillator input.
3-141
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
3-1/2 DIGIT A/D CONVERTER WITH HOLD AND
DIFFERENTIAL REFERENCE INPUTS
TC811
where:
V
REF
= Reference voltage
t
INT
= Integration Time
t
DEINT
= Deintegration Time
GENERAL THEORY OF OPERATION
Dual-Slope Conversion Principles
(All Pin Designations Refer to 40-Pin DIP Package)
The TC811 is a dual slope, integrating analog-to-digital
converter. An understanding of the dual slope conversion
technique will aid the user in following the detailed TC811
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 (T
DEINT
) is then
directly proportional to the unknown input voltage (V
IN
).
In a simple dual slope converter, a complete conversion
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:
30
20
10
0
NORMAL MODE REJECTION (dB)
0.1/T
1/T
10/T
INPUT FREQUENCY
T = MEASUREMENT PERIOD
Figure 2. Basic Dual Slope Converter
+
REF
VOLTAGE
ANALOG
INPUT
SIGNAL
+
+/
DISPLAY
SWITCH
DRIVER
CONTROL
LOGIC
INTEGRATOR
OUTPUT
CLOCK
COUNTER
POLARITY CONTROL
PHASE
CONTROL
VIN
VIN
VFULL SCALE
1.2 VFULL SCALE
VARIABLE
REFERENCE
INTEGRATE
TIME
FIXED
SIGNAL
INTEGRATE
TIME
INTEGRATOR
C
COMPARATOR
VREF
+
TC811
33
35
240k
10k
31
29
39
40
VREF
0.47
F
0.1F
V
1
OSC
2
OSC
TO ANALOG COMMON
(PIN 32)
2 CONVERSION/SEC
180k
0.068F
0.01F
ANALOG
INPUT
+
C
REF
34
C
REF
+
VIN
+
VIN
ANALOG
COMMON
VINT
VBUFF
CAZ
20
21
38
SEGMENT
DRIVE
919
2225
POL
BP
V
+
MINUS SIGN
BACKPLANE
28
LCD
1M
27
30
32
33
36
9V
+
26
20pF
10pF
V +
V +
22M
470k
1
HLDR
0
t
INT
1
V
REF
t
DEINT
R
INT
C
INT
R
INT
C
INT
V
IN
(t) dt =
[ ]
For a constant V
INT
:
V
IN
= V
REF
t
DEINT
t
INT
Figure 3. Normal-Mode Rejection of
Dual Slope Converter
Figure 1. Typical Operating Circuit