3-1/2 Digit Auto-Ranging A/D Converter with Triplex LCD ...

Obsolete Device
TC815
3-1/2 Digit Auto-Ranging A/D Converter with
Triplex LCD Drive and Display Hold Function
Features
General Description
• Auto-Range Operation for AC and DC Voltage
and Resistance Measurements
- Two User Selected AC/DC Current Ranges
20mA and 200mA
• 22 Operating Ranges
- 9 DC/AC Voltage
- 4 AC/DC Current
- 9 Resistance and Low Power Ohms
• Display HOLD Function
• 3-1/2 Digit Resolution in Auto-Range Mode:
- 1/2000
• Extended Resolution in Manual Mode: 1/3000
• Memory Mode for Relative Measurements:
- ±5% F.S.
• Internal AC to DC Conversion Op Amp
• Triplex LCD Drive for Decimal Points, Digits
and Annunciators
• Continuity Detection and Piezoelectric
Transducer Driver
• Compact Surface Mounted 64-pin
Plastic Flat Package
• Low Drift Internal Reference: 75ppm/°C
• 9V Battery Operation: 10mW
• Low Battery Detection and LCD Annunciator
The TC815 is a 3-1/2 digit integrating analog-to-digital
converter with triplex LCD display drive and automatic
ranging. A display hold function is on-chip. Input voltage/ohm attenuators ranging from 1 to 1/10,000 are
automatically selected. Five full scale ranges are provided. The CMOS TC815 contains all the logic and
analog switches needed to manufacture an autoranging instrument for ohms and voltage measurements. User selected 20mA and 200mA current ranges
are available. Full scale range and decimal point LCD
annunciators are automatically set in auto-range operation. Auto-range operation is available during ohms
(high and low power ohms) and voltage (AC and DC)
measurements, eliminating expensive range switches
in hand-held DMM designs. The auto-range feature
may be bypassed allowing decimal point selection and
input attenuator selection control through a single line
input. Expensive rotary switches are not required.
Device Selection Table
Part Number
Package
Operating
Temperature Range
TC815CBU
64-Pin PQFP
0°C to +70°C
During Manual mode operation, resolution is extended
to 3000 counts full scale. The extended range operation is indicated by a flashing 1 MSD. The extended
resolution is also available during 200kΩ and 2000V
full scale auto-range operation.
The Memory mode subtracts a reading, up to ±5% of
full scale from subsequent measurements. Typical
applications involve probe resistance compensation for
resistance measurements, tolerance measurements,
and tare weight measurements.
The TC815 includes an AC to DC converter for
AC measurements. Only external diodes/resistors/
capacitors are required.
A complete LCD annunciator set describes the TC815
meter function and measurement range during ohms,
voltage and current operation. AC measurements are
indicated as well as auto-range operation. A low battery
detection circuit also sets the low battery display
annunciator. The triplex LCD display drive levels may
be set and temperature compensation applied via the
VDISP pin. With HOLD low, the display is not updated.
A HOLD mode LCD annunciator is activated.
The “low ohms” measurement option allows in-circuit
resistance measurements by preventing semiconductor junctions from being forward biased.
© 2005 Microchip Technology Inc.
DS21474C-page 1
TC815
A continuity buzzer output is activated with inputs less
than 1% of full scale. An overrange input signal also
enables the buzzer, except during resistance measurements, and flashes the MSD display.
Featuring single 9V battery operation, 10mW power
consumption, a precision internal voltage reference
(75ppm/°C max TC) and a compact surface mounted
64-pin quad flat package, the TC815 is ideal for portable instruments.
Package Type
DS21474C-page 2
RVIBUF
RΩBUF
AD0
AD1
CFI
59
58
57
56
55
54
53
52
51 50
CAZ
ACVH
60
RX
VSSA
61
DGND
62
RANGE
63
HOLD
64
I
DC/AC
Ω/LOWΩ
-MEM
NC
64-Pin PQFP
49
NC
1
48
NC
OHM
2
47
CI
20mA
3
46
ACVL
BUZ
4
45
II
XTAL1
5
44
VI
XTAL2
6
43
VR4
VDISP
7
42
VR5
BP1
8
41
VR2
BP2
9
TC815
19
20
21
22
23
24
25
26
27
28
29
30
31
32
CREFL
18
RMREFL
CREFH
17
RMREFH
33
ANALOG COM
REFHI
FE0 16
VCC
34
VSSD
ΩR1
AGD0 15
-MEM/BATT
35
BCP3
ΩR2
BCP0 14
AC/–/AUTO
ΩR3
36
FE2
ΩR4
37
AGD2
38
Ω/V 12
k/m/
HOLD 13
FE1
LOΩ/A 11
BCP2
ΩR5
AGD1
39
NC
VR3
BP3 10
BCP1
40
© 2005 Microchip Technology Inc.
© 2005 Microchip Technology Inc.
Common
Voltage
Input
Current
Input
Ohms
Input
R14/9.9MΩ
200mA
20mA
Z1
6.2V
31
ΩR3 (÷ 100)
ΩR4 (÷ 1,000)
R13
500kΩ 44
– +
HOLD
TC815
3-1/2 Digit Auto-Ranging DMM
with HOLD Function
Ohms Range Attenuator
C5/1µf
– +
*Not Required when Resistor Network is used.
D1
R24/10kΩ
kΩ
mVA
LO
R27/2kΩ
R26/3kΩ
RΩBUF RVIBUF
0.1µF 0.1µF
CAZ CINT
0.1µF
CREF
C6
0.01µF
R20
100
kΩ
+
R19/5kΩ R18/24kΩ
200mA
20mA
–
SIA
9V
32.768kHz
( 33kHz)
Enable
Ω
20mA
200mA
V
Ω
V
153.850mV
RMREFH 30
ANALOG
CAZ INT HOLD CIF CREFL CREFH COM REFHI
49
47
60 51
32
33 29 34
-MEM 61
DC/AC or Ω/LOWΩ 62
Manual RANGE Change 59
I 63
OHMS 2
20mA 3
Digital GND 58
VSSD 27
SIB
Audio
Transducer
SSA
Tri-Plex
LCD Display
11 12 13 25 26 24 23 22 21 20 19 18 16 15 14
4 5
LOΩ/AΩV K/m
-MEM/ BCP3 FE2 AGD2 BCP2 FE1 AGD1 BCP1 FE0 AGD0 BCP0 BUZXTAL1 6
HOLD
BATT
XTAL2
AC/–/AUTO
100's
10's
1's
Display
VCC 28
1000's
Annunciators
57
V
Segment & Decimal Point Drive
AUTO
AC
-MEM
VI (÷1)
R12/1.11MΩ 41
VR2 (÷10)
Voltage Range Attenuator
R11/101kΩ 40
VR3 (÷100)
R10/10kΩ 43
VR4 (÷1,000)
ADO
VR5 (÷10,000)
ADI
ACVH
ACVL RΩBUF RVIBUF
42 53
52
56
46 54
55
R21/2.2MΩ
R9/1kΩ
C1/1µF
200 150
R22/470kΩ
kΩ kΩ
C4/µf
C2/0.22µF
4.7µf
– +
D2
R23/10kΩ
R16
1Ω
D4
45 I
I
R2/1638.5Ω 36
ΩR2 (÷ 10)
R1/163.85 35
R1 (÷ 1)
R3/16.385kΩ 37
R4/163.85kΩ 38
ΩR5 (÷ 10,000)
Backplane
Drivers
50 7 8 9 10
RX VDISP BP1 BP2 BP3
RMREFL
0.1µF
R5/1.6385MΩ 39
R6/100kΩ
R15 D3
9Ω
R8/220Ω (PTC)
Positive
Temperature
Coefficient
Resistor
0.01
µF
R7/100kΩ
If LCD Bias is Connected to DIG GND,
Peak Drive Signal ≈ 5V.
LCD Bias
To VCC
39pf
TC815
Typical Application and Test Circuit
DS21474C-page 3
TC815
1.0
ELECTRICAL
CHARACTERISTICS
*Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent 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.
Absolute Maximum Ratings*
Supply Voltage (V+ to V–) .....................................15V
Analog Input Voltage (Either Input) ................ V+ to VReference Input Voltage.................................. V+ to VVoltage at Pin 45 ........................................GND ±0.7V
Power Dissipation (TA ≤ 70°C)
64-Pin Plastic Flat Package ...........................1.14W
Operating Temperature Range:
Commercial Package (C) .................... 0°C to +70°C
Storage Temperature Range ..............-65°C to +150°C
TC815 ELECTRICAL SPECIFICATIONS
Electrical Characteristics: VA = 9V, TA = +25°C, unless otherwise specified (see Typical Application and Test Circuit Figure).
Symbol
RE
Parameter
Min
Typ
Max
Zero Input Reading Input Resistor
-0000
0000
+0000
Digital Reading 200mV Range w/o 10MΩ Input
-0001
—
+0001
Digital Reading 200mV Range w/10MΩ Input
-0000
0000
+0000
Digital Reading 20mA and 200mA Range
—
—
±1 Count
—
—
±3
—
—
±1
Rollover Error
Unit
Test Conditions
200mV Range w/o 10MΩ
Input Resistor
200mV Range w/10MΩ Input
20mA and 200mA Range
NL
Linearity Error
—
—
±1
Count
IIN
Input Leakage Current
—
—
10
pA
EN
Input Noise
—
20
—
μVp-p
AC Frequency Error
—
±1
—
%
40Hz to 500Hz
—
±5
—
%
40Hz to 200Hz
Open Circuit Voltage
—
570
660
mV
Excludes 200Ω Range
for OHM Measurements
Open Circuit Voltage
—
285
350
mV
Excludes 200Ω Range
for LO OHM Measurement
VCOM
Analog Common Voltage
2.5
2.6
3.3
V
VCTC
Common Voltage Temperature
Coefficient
—
—
50
ppm/°C
Display Multiplex Rate
—
100
—
Hz
Low Logic Input
—
—
1
V
20mA, AC, I, LOW Ω, HOLD
Range, -MEM, OHMs
(Relative to DGND Pin 58)
Logic 1 Pull-up Current
—
25
—
μA
20mA, AC, I, LOW Ω, HOLD
Range, -MEM, OHMs
(Relative to DGND Pin 58)
kHz
VIL
Buzzer Drive Frequency
—
4
—
Low Battery Flag Voltage
6.3
6.6
7.0
V
Operating Supply Current
—
0.8
1.5
mA
DS21474C-page 4
Best Case Straight Line
BW = 0.1 to 10Hz
(V+ - VCOM)
VCC to VSSA
© 2005 Microchip Technology Inc.
TC815
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Pin Number
(64-Pin Plastic)
Quad Flat Package
Symbol
Description
1
NC
2
OHM
Logic Input. “0” (Digital Ground) for resistance measurement.
Logic Input. “0” (Digital Ground) for 20mA full scale current measurement.
3
20mA
Audio frequency, 4kHz, output for continuity indication during resistance measurement.
4
BUZ
5
XTAL1
32.768kHz Crystal Connection.
6
XTAL2
32.768kHz Crystal Connection.
7
VDISP
Sets peak LCD drive signal: VP - VDD - VDISP. VDISP may also be used to compensate for
temperature variation of LCD crystal threshold voltage.
8
BP1
LCD Backplane #1.
9
BP2
LCD Backplane #2.
10
BP3
LCD Backplane #3.
11
LOΩ/A
Audio frequency, 4kHz, output for continuity indication during resistance measurement. A
non-continuous 4kHz signal is output to indicate an input overrange during voltage or
current measurements.
LCD Annunciator segment drive for low ohms resistance measurement and current
measurement.
12
Ω/V
13
k/m/HOLD
14
BCP0
(One’s digit)
15
ADG0
LCD segment drive for “a,” “g,” “d” segments of LSD.
16
FE0
LCD segment drive for “f” and “e” segments of LSD.
17
NC
No connection.
18
BCP1
LCD segment drive for “b,” “c” segments and decimal point of 2nd LSD.
19
AGD1
LCD segment drive for “a,” “g,” “d” segments of 2nd LSD (Ten’s digit).
LCD Annunciator segment drive for resistance measurement and voltage measurement.
LCD Annunciator segment drive for k (“kilo-ohms”), m (“milliamps” and
“millivolts”) and HOLD mode.
LCD segment drive for “b,” “c” segments and decimal point of least significant digit (LSD).
20
FE1
21
BCP2
LCD segment drive for “f” and “e” segments of 2nd LSD.
LCD segment drive for “b,” “c” segments and decimal point of 3rd LSD
(Hundred’s digit).
22
AGD2
LCD segment drive for “a,” “g,” “d” segments of 3rd LSD.
23
FE2
24
BCP3
LCD segment drive for “b,” “c” segments and decimal point of 3rd LSD.
LCD segment drive for “b,” “c” segments and decimal point of MSD
(Thousand’s digit).
25
AC/-/AUTO
LCD annunciator drive signal for AC measurements, polarity, and auto-range operation.
26
-MEM/BATT
LCD annunciator drive signal for low battery indication and Memory
(Relative Measurement) mode.
27
VSSD
Negative battery supply connection for internal digital circuits. Connect to negative terminal
of battery.
28
VCC
Positive battery supply connection.
29
ANALOG
COM
Analog circuit ground reference point. Nominally 2.6V below VCC.
30
RMREFH
Ratiometric (Resistance measurement) reference high voltage.
31
RMREFL
Ratiometric (Resistance measurement) reference low voltage.
32
CREFL
Reference capacitor negative terminal CREF 0.1µf.
33
CREFH
Reference capacitor positive terminal CREF 0.1µf.
34
REFHI
Reference voltage for voltage and current measurement; nominally 163.85mV.
© 2005 Microchip Technology Inc.
DS21474C-page 5
TC815
TABLE 2-1:
PIN FUNCTION TABLE (CONTINUED)
Pin Number
(64-Pin Plastic)
Quad Flat Package
Symbol
Description
35
ΩR1
Standard resistor connection for 200Ω full scale.
36
ΩR2
Standard resistor connection for 2000Ω full scale.
37
ΩR3
Standard resistor connection for 20kΩ full scale range.
38
ΩR4
Standard resistor connection for 200kΩ full scale range.
39
ΩR5
Standard resistor connection for 2000kΩ full scale range.
40
VR3
Voltage measurement ÷ 100 attenuator.
41
VR2
Voltage measurement ÷ 10 attenuator.
42
VR5
Voltage measurement ÷ 10,000 attenuator.
43
VR4
Voltage measurement ÷ 1000 attenuator.
44
VI
Unknown voltage input ÷ 1 attenuator.
45
II
Unknown current input.
46
ACVL
47
CI
Integrator capacitor connection. Nominally 0.1µf. (Low dielectric absorption. Polypropylene
dielectrics suggested.)
48
NC
No connection.
49
CAZ
Auto-zero capacitor connection; nominally 0.1µf.
50
RX
Unknown resistance input.
51
CFI
Input filter connection.
52
AD1
Negative input of internal AC to DC operational amplifier.
53
AD0
Output of internal AC to DC operational amplifier.
54
RΩBUF
Active buffer output for resistance measurement. Integration resistor connection. Integrator
resistor nominally 220kΩ.
55
RVIBUF
Active buffer output for voltage and current measurement. Integration resistor connection.
Integration resistor nominally 150kΩ.
56
ACVH
Positive output of AC to DC converter.
57
VSSA
Negative supply connection for analog circuits. Connect to negative terminal of 9V battery.
58
DGND
59
RANGE
60
HOLD
Input to hold display. Connect to DIG GND.
61
-MEM
Input to enter Memory Measurement mode for relative measurements. The two LSD’s are
stored and subtracted from future measurements.
62
DS/AC
Ω/LOWΩ
Input that selects AC or DC option during voltage/current measurements. For resistance
measurements, Ω/LOWΩ, the ohms or low power (voltage) ohms option can be selected.
63
I
64
NC
DS21474C-page 6
Low output of AC to DC converter.
Internal logic digital ground. The logic “0” level. Nominally 4.7V below VCC.
Input to set manual operation and change ranges.
Input to select current measurement. Set to logic “0” (Digital ground) for
current measurement
No connection.
© 2005 Microchip Technology Inc.
TC815
3.0
DETAILED DESCRIPTION
3.1
Resistance, Voltage, Current
Measurement Selection
The TC815 is designed to measure voltage, current,
and resistance. Auto-ranging is available for resistance
and voltage measurements. The OHMS (Pin 2) and
I (Pin 63) input controls are normally pulled internally to
VCC. By tying these pins to Digital Ground (Pin 58), the
TC815 is configured internally to measure resistance,
voltage, or current. The required signal combinations
are shown in Table 3-1.
TABLE 3-1:
R8, a positive temperature coefficient resistor, and the
6.2V zener Z1 in Figure 3-1, provide input voltage protection during ohms measurements.
TABLE 3-2:
OHM (Pin 2)
I (Pin 63)
Selected
Measurement
0
0
Voltage
0
1
Resistance
1
0
Current
1
1
Voltage
Note 1: 0 = Digital Ground
2: 1 = Floating or Tied to VCC
3: OHM and I are normally pulled internally high to
VCC (Pin 28). This is considered a logic “1.”
4: Logic “0” is the potential at digital ground (Pin 58).
Resistance Measurements
(Ohms and Low Power Ohms)
The TC815 can be configured to reliably measure incircuit resistances shunted by semiconductor junctions. The TC815 Low Power Ohms Measurement
mode limits the probe open circuit voltage. This prevents semiconductor junctions in the measured system
from turning on.
In the Resistance Measurement mode, the Ω/LOWΩ
(Pin 62) input selects the Low Power Ohms Measurement mode. For low power ohms measurements,
Ω/LOWΩ (Pin 62) is momentarily brought low to digital
ground potential. The TC815 sets up for a low power
ohms measurement with a maximum open circuit
probe voltage of 0.35V above analog common. In the
Low Power Ohms mode, an LCD display annunciator,
LOWΩ, will be activated. On power-up, the Low Power
Ohms mode is not active.
If the Manual mode has been selected, toggling
Ω/LOWΩ will reset the TC815 back to the Auto-Range
mode. In Manual mode, the decision to make a normal
or low power ohms measurement should be made
before selecting the desired range.
© 2005 Microchip Technology Inc.
OHMS RANGE LADDER
NETWORK
Full Scale
Range
Standard
Resistance
Low Power
Ohms Mode
200Ω
163.85 Ω (R1)
NO
2000Ω
1638.5 kΩ (R2)
YES
MEASUREMENT SELECTION
LOGIC
Function Select Pin
3.2
The low power ohms measurement is not available on
the 100Ω full scale range. Open circuit voltage on this
range is below 2.8V. The standard resistance values
are listed in Table 3-2.
20kΩ
16,385Ω (R3)
YES
200kΩ
16385Ω (R4)
YES
2,000kΩ
1,638,500Ω (R5)
YES
3.3
Ratiometric Resistance
Measurements
The TC815 measures resistance ratiometrically. Accuracy is set by the external standard resistors connected
to Pin 35 through 39. A Low Power Ohms mode may
be selected on all but the 200Ω full scale range. The
Low Power Ohms mode limits the voltage applied to the
measured system. This allows accurate “in-circuit”
measurements when a resistor is shunted by semiconductor junctions. Full auto-ranging is provided. External
precision standard resistors are automatically switched
to provide the proper range.
Figure 3-1 shows a detailed block diagram of the
TC815 configured for ratiometric resistance measurements. During the signal integrate phase, the reference
capacitor charges to a voltage inversely proportional to
the measured resistance, RX. Figure 3-2 shows the
conversion accuracy relies on the accuracy of the
external standard resistors only.
Normally the required accuracy of the standard resistances will be dictated by the accuracy specifications of
the users end product. Table 3-3 gives the equivalent
ohms per count for various full scale ranges to allow
users to judge the required resistor for accuracy.
TABLE 3-3:
REFERENCE RESISTORS
Full Scale
Range
Reference
Resistor
Ω/Count
200k
163.85
0.1
2k
1638.5
1
20k
16385
10
200k
163850
100
2M
1638500
1000
DS21474C-page 7
TC815
FIGURE 3-1:
RATIOMETRIC RESISTANCE MEASUREMENT FUNCTIONAL DIAGRAM
9V
VSSD
57 VSSA
30
R5/1638500Ω
39
S29
38
S30
37
S31
R2/1638.5Ω 36
S32
R4/163850Ω
R3/16385Ω
÷10k
÷1k
÷100
÷10
÷1
R1/163.85Ω
VCC
DE • Ω
S23
33
S20
30
~1.5kΩ
Low Ohms
Ω • LO
VCC
÷100 ÷10 ÷1
S24 S25 S26 S27 S28
R8
220Ω
28
Ω • HIΩ
VA
S33
÷10k ÷1k
35
10kΩ
Ohms
REFHI
34
~1.5kV
Voltage
Reference
+
DE + Ω
–
Analog
Common
VCC - 2.6V
CREF
0.1µF
32
31 50
S18
DE
S21
DE • Ω
R6/100kΩ
RX
S13
S12
INT • (Ω + DC)
1
V•
1
Unknown
TC815
Buffer
DE
R7/100k Ω 50
S37
S36
Ω
S34
Ω
Ω
S35
Ω
Integrator
49
RΩBUF 54 55
RVIBUF
150kΩ
220kΩ
FIGURE 3-2:
Comparator
47
CAZ
0.1µF
CINT
0.1µF
RESISTANCE MEASUREMENT ACCURACY SET BY EXTERNAL
STANDARD RESISTOR
0.64V for Ohms
0.32V for LO Ohms
VA
+
RS
16.385k
CREF
100 kΩ
VR
Example: 200kΩ Full Scale Measurement
163.85kΩ
(a ) V R = ⎛ ------------------------------------------------⎞ x0.64
⎝ 163.85 + 220 + R X⎠
(b)
VR
RX
⎞ x0.64
V X = ⎛ -------------------------------------------------------------⎝ 163.85kΩ + 220Ω + R X⎠
(c) “Ramp Up Voltage” = “Ramp Down Voltage”
.
VX
VX
= ----------------T
. . ----------------xT
( RI CI ) I
( R I C I ) DE
220Ω
VX
Unknown
5kΩ
29
≈ VCC - 2.8V
DE S19
R18
24kΩ
RX
To Analog Buffer
Where:
RI = Integrating Resistor, TI = Integrate Time
CI = Integrating Capacitor, TDE = Deintegrate Time
(TDE)
(d) RX = 163.85
TI
Independent of RI, CI or Internal Voltage Reference
DS21474C-page 8
© 2005 Microchip Technology Inc.
TC815
3.4
Voltage Measurement
The divider leg resistors give a 200mV signal VI
(Pin 44) for full scale voltages from 200mV to 2000V.
Resistive dividers are automatically changed to provide
in range readings for 200mV to 2000V full scale readings
(Figure 3-3). The input resistance is set by external
resistors R14/R13. The divider leg resistors are R9-R12.
FIGURE 3-3:
TC815 ANALOG SECTION
0.1µF
R7/100kΩ
Ohms
Input
For applications which do not require a 10mΩ input
impedance, the divider network impedances may be
lowered. This will reduce voltage offset errors induced
by switch leakage currents.
R8/220 Ω
ΩRX 50
S12 V • 1/1
RMREFL 31
S21 DE • Ω
R5/1.638MΩ
ΩR 5 39
S24 W• 1/10k
R4/163.85kΩ
ΩR 4 38
Ω•
S25 1/1k
R3/16385Ω
ΩR 3 37
Ω•
S26 1/100
R2/1638.5Ω
ΩR 2 36
Ω•
S27 1/10
R1/163.85Ω
ΩR 1 35
R6/100kΩ
(PTC)
0.01µF
Z1
6.2V
S28
TC815
VCC
VCC
10kΩ
S44 Ω • HI Ω
1.5k
VCC S43
+ Ω • LOW
2.8V REF AMP
–
1.5k
+
Ω •1/1
Current Input
R15/9 Ω
I I 45
200mA
R19/5k Ω
29
34 REFHI
≈163.85mV
D3 D4
R16/1Ω
Voltage
Input
RMREFH
R18/24k Ω
ANALOG
COM
–
S33 S32 S31 S30 S29
Ω • Ω • Ω•
Ω • Ω•
1/1 1/10 1/100 1/1k 1/10k
VCC
Ω+1
S10
20mA
30
S22
DE • Ω
R14/9.9MΩ
VI 44
S1
S22
DE • Ω
V•1/1
V• V•
V• V•
1/10 1/100 1/1 1/10k
k
S8 S9
S6 S7
R13/500kΩ*
*Not required when
Resistor Network is used.
R12/1.11M Ω VR2 41
S2
33 CREFH
V•1/10
S20 DE
R11/101kΩ VR3 40
S3
V•1/100
R10/10kΩ
S4
V•1/1k
VR4 43
VR2 42
4.7µF
D2
D1
R24
C3
10k Ω + 1µF
R23
10kΩ
53
R22
470
kW
+
C4
1µF
R26
33kΩ
0.1µF
32 CREFL
S18 DE
R9/1kΩ
Common
CREFH
S5
AC-to-DC
Converter
Op Amp
ADO
V•1/10k
S19 DE+ Ω
+
S11
–
Ω +AC
S16 DE+
S17 DE51 CIF
R21
2.2
MΩ
52
C2
ADI
R20/100kΩ
0.01µF
C6
S13
0.22 µF
ACVH 56
S14
C1/1µF
INT• Ω •AC
R27/2kΩ
INT•(Ω +DC)
Buffer
+
ACVL 46
S40
S38 AZ
S15 AZ
–
INT• Ω •AC
S39
INT+Ω +DC
–
S35
Ω
Ω
S34 Ω
54
RBUFΩ
S37
Ω
–
+
+
Comparator
To Digital
Section
Integrator
49
55
R Ω RVI C
BUF BUF AZ
220
0.01µF
k Ω 150
k Ω CAZ
47
INT
0.01µF
CINT
RBUFΩ
© 2005 Microchip Technology Inc.
DS21474C-page 9
TC815
3.5
Current Measurement
The TC815 measures current only under manual range
operation. The two user selectable full scale ranges
are: 20mA and 200mA. Select the current Measurement mode by holding the I input (Pin 63) low at digital
ground potential. The OHM input (Pin 2) is left floating
or tied to the positive supply.
Two ranges are possible. The 20mA full scale range is
selected by connecting the 20mA input (Pin 3) to digital
ground. If left floating the 200mA full scale range is
selected.
External current to voltage conversion resistors are
used at the II input (Pin 45). For 20mA measurements
a 10Ω resistor is used. The 200mA range needs a 1Ω
resistor; full scale is 200mV.
PC board trace resistance between analog common
and R16 (see Figure 2-1) must be minimized. In the
200mA range, for example, a 0.05 trace resistance will
cause a 5% current to voltage conversion error at II
(Pin 45).
The extended resolution measurement option operates
during current measurements. To minimize rollover
error the potential difference between ANALOG COM
(Pin 29) and system common must be minimized.
DS21474C-page 10
3.6
Measurement Options
(AC to DC Measurements)
In voltage and current measurements, the TC815 can
be configured for AC measurements. An on-chip operational amplifier and external rectifier components perform the AC to DC conversion.
When power is first applied, the TC815 enters the DC
Measurement mode. For AC measurements (current or
voltage), AC/DC (Pin 62) is momentarily brought low to
digital ground potential; the TC815 sets-up for AC measurements and the AC liquid crystal display annunciator activates. Toggling AC/DC low again will return the
TC815 to DC operation.
If the Manual Operating mode has been selected, toggling AC/DC will reset the TC815 back to the AutoRange mode. In Manual mode operation, AC or DC
operation should be selected first and then the desired
range selected.
The minimum AC voltage full scale voltage range is 2V.
The DC full scale minimum voltage is 200mV. AC current measurements are available on the 20mA and
100mA full scale current ranges.
© 2005 Microchip Technology Inc.
TC815
4.0
CONVERSION TIMING
The TC815 analog-to-digital converter uses the conventional dual slope integrating conversion technique
with an added phase that automatically eliminates zero
offset errors. The TC815 gives a zero reading with a
zero volt input.
The TC815 is designed to operate with a 32.768kHz
crystal. The 32kHz crystal is low cost and readily available; it serves as a time-base oscillator crystal in many
digital clocks. (See External Crystal Sources.)
The external clock is divided by two. The internal clock
frequency is 16.348kHz, giving a clock period of
61.04µsec. The total conversion — auto-zero phase,
signal integrate and reference deintegrate — requires
8000 clock periods or 488.3msec. There are approximately two complete conversions per second.
FIGURE 4-1:
BASIC TC815
CONVERSION TIMING
Signal
Integrate
Phase
TC815
Reference
De-integrate
Phase
Next Conversion
Auto-Zero Cycle
Extended
Resolution
Auto-Zero
Phase
Zero Crossing
Min. Auto-Zero
Time
Fixed
1638.5 TP
3361.5TP
TI
TCONV 8000 TP
*Max
3000.0 TP
TDE
To Input
Signal
*In Auto-Range Operation
Maximum is 2000TP and
Minimum Auto-Zero time
i s 4361.5TP
External Crystal = 32.768kHz
Internal Clock Period = TP = 2/32.768 = 61.04µsec
The integration time is fixed at 1638.5 clock periods or
100msec. This gives rejection of 50/60Hz AC line
noise.
Total Conversion Time = TCONV = 8000 (TP)
= 488.3mec ≈ 2 Conv/Sec.
The maximum reference de-integrate time, representing a full scale analog input, is 3000 clock periods or
183.1msec during manual extended resolution operation. The 3000 counts are available in Manual mode,
extended resolution operation only. In Auto-Ranging
mode, the maximum de-integrate time is 2000 clock
periods. The 1000 clock periods are added to the autozero phase. An auto-ranging, or manual conversion
takes 8000 clock periods. After a zero crossing is
detected in the Reference De-integrate mode, the autozero phase is entered. Figure 4-1 shows the basic
TC815 timing relationships.
Maximum Reference De-integration Time =
TDE = 3000 (TP) = 183.1msec
(Manual Extended Resolution)
© 2005 Microchip Technology Inc.
Integration Time = TI = 1638.5 (TP) = 100.0msec.
Minimum Auto-Zero Time
= (8000-3000-1638.5) (TP) = 205.1msec
(Manual, Extended Resolution)
= (8000-2000-1638.5) (TP) = 266.2msec
(Auto-Range)
DS21474C-page 11
TC815
5.0
MANUAL RANGE SELECTION
(voltage or resistance), or measurement option (AC/
DC, Ω/LOΩ) changes. This causes the TC815 to return
to auto-ranging operation.
The TC815 voltage and resistance auto-ranging feature can be disabled by momentarily bringing RANGE
(Pin 59) to digital ground potential (Pin 58). When the
change from auto-to-manual ranging occurs, the first
manual range selected is the last range in the AutoRanging mode.
The “Auto” LCD annunciator driver is active only in the
Auto-Range mode. Table 5-1 shows typical operation,
where the manual range selection option is used. Also
shown is the extended resolution display format.
Also see Figure 5-1 through Figure 5-3.
The TC815 power-up circuit selects auto-range operation initially. Once the manual range option is entered,
range changes are made by momentarily grounding
the RANGE control input. The TC815 remains in the
Manual Range mode until the measurement function
TABLE 5-1:
MANUAL RANGE OPERATION
DC Volts
AC Volts
Ohm
LO Ohm
23.5V
18.2V
18.2kΩ
2.35MΩ
Input
Power-on
Auto-Range
Operation
Range
Display
Range
Range
Display
Range
Range
Display
200mV
“1”00.0V
2V
“1”000V
200Ω
“1”00.0Ω
2kΩ
“1”.000kΩ
2V
1.000V
20V
18.20V
2kΩ
“1”.000kΩ
10kΩ
“1”.0.00kΩ
20V
“1”0.00V
—
—
20kΩ
18.20Ω
200kΩ
“1”.00.0kΩ
200V
23.5V
—
—
—
—
2000kΩ
“1”350kΩ
Manual Operation
DC Volts
AC Volts
Ohm
LO Ohm
23.5V
18.2V
18.2kΩ
2.35MΩ
Input
# of Range
Changes
(See Note 4)
Range
Display
Range
Range
Display
Range
Range
Display
1
200V
23.5V
20V
18.20V
20kΩ
18.20V
2000kΩ
“1”350kΩ
2
200mV
“1”00.0V
2V
“1”.000V
200Ω
“1”00.0ΩkΩ
2kΩ
“1”.000kΩ
3
2V
1.000V
20V
18.20V
2kΩ
“1”000kΩ
20kΩ
“1”0.00kΩ
4
20V
“1”3.50V
20V
18.2V
20kΩ
18.20kΩ
200kΩ
“1”00.0kΩ
5
200V
23.5V
600V
19V
200kΩ
18.2kΩ
2000kΩ
“1”350kΩ
6
1000V
24V
2V
“1”.000V
2000kΩ
19kΩ
2kΩ
“1”.000kΩ
7
200mV
“1”00.0mV
20V
18.20V
200kΩ
“1”00.0Ω
20kΩ
“1”0.00kΩ
8
2V
“1”.000V
200V
18.2V
2kΩ
“1”.000kΩ
200kΩ
“1”00.0kΩ
Note 1: A flashing MSD is shown as a “1”. A flashing MSD indicates the TC815 is over-ranging if all other digits are zero.
2: The first manual range selected is the last range in the Auto-Ranging mode.
3: A flashing MSD with a non-zero display indicates the TC815 has entered the Extended Resolution Operating mode. An
additional 1000 counts of resolution is available. This extended operation is available only in manual operation for voltage,
resistance and current measurements.
4:
= Momentary ground connection.
DS21474C-page 12
© 2005 Microchip Technology Inc.
TC815
FIGURE 5-1:
MANUAL RANGE
SELECTION: RESISTANCE
MEASUREMENTS
FIGURE 5-3:
Manual Range
Select
MANUAL RANGE
SELECTION: VOLTAGE
MEASUREMENTS
Range Select
TC815
Continuity
Indicator
Output 4kHz
Audio
Frequency
Yes
Output Noncontinuous
4kHz Audio
Frequency
Is
RX < 19
?
Continuous 4kHz
Buzzer
TC815
No
Is
RX > 3000
?
No
Over Range Indicator
Over Range Indicator
Yes
Is
VX > 3000
?
Display "1" 000
"1" = > Flashing MSD
Yes
"1" = > Flashing MSD
No
Is
RX > 2000
?
No
Yes*
Display Last
3 Digits and Flash
MSD
Is
VX > 2000
?
Extended
Resolution
Feature
Display True
Reading
No
*Mode also operates when Auto-Ranging Operation
is selected and 2MΩ < RX < 2.999MΩ
For resistance measurements, the buzzer signal does
not indicate an overrange condition. The buzzer is used
to indicate continuity. Continuity is defined as a resistance reading less than 19 counts.
FIGURE 5-2:
MANUAL RANGE
SELECTION: CURRENT
MEASUREMENTS
Range
Select
TC815
Yes
Output 4kHz
Audio
Frequency
Over Range Indicator
Is
IX > 3000
?
Yes
Is
IX > 2000
?
Display
"1" 000
"1" = > Flashing MSD
No
Yes
No
Display
"1" 000
Yes
Display Last 3 Digits
and Flash
MSD
Extended Resolution
Feature
Display True
Reading
5.1
Extended Resolution
Manual Operation
The TC815 extends resolution by 50% when operated
in the Manual Range Select mode for current, voltage,
and resistance measurements. Resolution increases to
3000 counts from 2000 counts. The extended resolution feature operates only on the 2000kΩ and 2000V
ranges during auto-range operation.
In the Extended Resolution Operating mode, readings
above 1999 are displayed with a blinking “1” most significant digit. The blinking “1” should be interpreted as
the digit 2. The three least significant digits display data
normally.
An input overrange condition causes the most significant digit to blink and sets the three least significant
digits to display “000.” The buzzer output is enabled for
input voltage and current signals with readings greater
than 2000 counts in both manual and auto-range
operation.
Display Last
3 Digits and Flash
MSD
Extended
Resolution
Feature
Display True
Reading
© 2005 Microchip Technology Inc.
DS21474C-page 13
TC815
6.0
-MEM OPERATING MODE
Bringing -MEM (Pin 61) momentarily low configures the
TC815 “-MEM” Operating mode. The -MEM LCD
Annunciator becomes active. In this Operating mode,
subsequent measurements are made relative to the last
two digits (-99) displayed at the time MEM is low. This
represents 5% of full scale. The last two significant digits
are stored and subtracted from all the following input
conversions. The following examples clarify operation:
EXAMPLE 6-1:
IN AUTO-RANGING
RI (N) = 18.21kΩ (20kΩ Range) = > Display 18.21kΩ
MEM
= > Store 0.21kΩ
RI (N+1) = 19.87kΩ (20kΩ Range)
= > Display 19.87 - 0.21 = 19.66kΩ
RI (N+2) = 22.65kΩ (200kΩ Range)
= > Display 22.7kΩ and MEM disappears
EXAMPLE 6-2:
IN FIXED RANGE
(200.0Ω FULL SCALE)
RI (N) = 18.21kΩ = > Display 18.2kΩ
= > Store 8.2Ω
MEM
RI (N+1) = 36.7Ω
= > Display 36.7 - 8.2 = 28.5Ω
RI (N+2) = 5.8Ω
= > Display 5.8 = 2.4Ω*
*Will display minus resistance if following input is
less than offset stored at fixed range.
EXAMPLE 6-3:
IN FIXED RANGE
VI (N) = 0.51V = > Display 0.51V
= > Store 0.51V
MEM
VI (N+1) = 3.68V
= > Display 3.68 - 0.51 = 3.17V
VI (N+2) = 0.23V
= > Display 0.23 - 0.51 = -0.28V
VI (N+3) = -5.21V
= > Display - 5.21 - 0.51 = -5.72V
On power-up, the TC815 “-MEM” mode is not active.
Once the “-MEM” is entered, bringing MEM low again,
it returns the TC815 to normal operation.
The “-MEM” mode is also cancelled whenever the measurement type (resistance, voltage, current AC/DC,
Ω/LOΩ) or range is changed. The LCD -MEM annunciator will be off in normal operation.
7.0
AUTOMATIC RANGE
SELECTION OPERATION
When power is first applied, the TC815 enters the autorange operating state. The Auto-Range mode may be
entered from Manual mode by changing the measurement function (resistance or voltage), or by changing
the measurement option (AD/DC, Ω/LOΩ).
The automatic voltage range selection begins on the
most sensitive scale first: 200mV for DC or 2.000V for
AC measurements. The voltage range selection flow
chart is given in Figure 7-1.
Internal input protection diodes to VDD (Pin 28) and
VSSA (Pin 57) clamp the input voltage. The external
10MΩ input resistance (see Figure 7-1, R14 and R13)
limits current safely in an overrange condition.
The voltage range selection is designed to maximize
resolution. For input signals less than 9% of full scale
(count reading <180), the next most sensitive range is
selected.
An over range voltage input condition is flagged whenever the internal count exceeds 2000, by activating the
buzzer output (Pin 4). This 4kHz signal can directly
drive a piezo electric acoustic transducer. An out of
range input signal causes the 4kHz signal to be on
122msec, off for 122 msec, on for 122msec and off for
610msec (see Figure 11-1).
During voltage auto-range operation, the extended resolution feature operates on the 2000V range only. (See
Extended Resolution Operating mode discussion.)
The resistance automatic range selection procedure is
shown in Figure 7-2. The 200Ω range is the first range
selected unless the TC815 low ohms resistance measurement option is selected. In low ohms operation, the
first full scale range tried is 2kΩ.
The resistance range selected maximizes sensitivity. If
the conversion results in a reading less than 180, the
next most sensitive full scale range is tried.
If the conversion is less than 19 in auto-range operation, a continuous 4kHz signal is output at BUZ (Pin 4).
An over range input does not activate the buzzer.
Out of range input conditions are displayed by a blinking most significant digit with the three least significant
digits set to “000.”
The extended resolution feature operates only on the
2000kΩ and 2000V full scale range during auto-range
operation. A blinking “1” most significant digit is interpreted as the digit 2. The three least significant digits
display data normally.
In the auto-range operation, if the following input signal
cannot be converted on the same range as the stored
value, the “-MEM” mode is cancelled. The LCD annunciator is turned off.
The “-MEM” Operating mode can be very useful in
resistance measurements when lead length resistance
would cause measurement errors.
DS21474C-page 14
© 2005 Microchip Technology Inc.
TC815
FIGURE 7-1:
AUTO-RANGE OPERATION: VOLTAGE MEASUREMENT
TC815
N = 0 if DC
N = 1 if AC
N = 0: 200.0mV Full Scale Range
N = 1: 2,000V Full Scale Range
N = NK
Remaining in Range Selected
during the Kth Conversion
Kth
Conversion
VX - (1/10N) VIN
VX < 180
?
N=N–1
Yes
No
VX > 2000
?
N = 0 if DC
N = 1 if AC
Yes
No
Display
Voltae (VX)
K=K+1
Yes
N=N+1
No
N=4
?
Yes
VX > 3000
?
Yes
No
Display "1" XXX
Flash MSD
Activate
Buzzer
Over Range
Display "1" 000
Flash MSD
Start: Power-on, Function or Measurement Option Change
© 2005 Microchip Technology Inc.
DS21474C-page 15
TC815
FIGURE 7-2:
AUTO-RANGE OPERATION: RESISTANCE MEASUREMENT
N = 0 if Ω
N = 1 if LOΩ
TC815
N = 0: 200.0Ω Full Scale Range
N = 1: 2,000kΩ Full Scale Range
Remaining in Range Selected
during the Kth Conversion
Kth
Conversion
RX = (1/10N) RIN
Continuity
Indicator
Activate
Buzzer
Yes
RX < 19
?
N=N–1
No
Continuous
4kHz Signal
No
RX < 180
?
Yes
N = 0 if Ω
N =1 if LOWΩ
No
Yes
RX >2000
?
Display
Resistance
K=K+1
Yes
No
N=N+1
N=4
?
Yes
RX >3000
?
Over Range
No
Display "1" XXX
Flash MSD
Display "1" 000
Flash MSD
Extended Resolution
Yes
Start: Power-on, Function or Measurement Option Change
DS21474C-page 16
© 2005 Microchip Technology Inc.
TC815
8.0
LOW BATTERY DETECTION
CIRCUIT
The TC815 contains a low battery detector. When the
9V battery supply has been depleted to a 7V nominal
value, the LCD display low battery annunciator is
activated.
The low battery detector is shown in Figure 8-1. The
low battery annunciator remains OFF with the battery
supply greater than 0.7V. The annunciator is ON before
the supply battery has reached 6.3V.
FIGURE 8-1:
The TC815 internally generates two intermediate LCD
drive potentials (VH and VL) from a resistive divider
(Figure 9-1), between VCC (Pin 28) and VDISP (Pin 7).
The ladder impedance is approximately 150kΩ. This
drive method is commonly known as 1/3 bias. With
VDISP connected to digital ground VP ≈ 5.0V.
The intermediate levels are needed so that drive signals giving RMS “ON” and “OFF” levels can be generated. Figure 9-2 shows a typical drive signal and the
resulting wave forms for “ON” and “OFF.” RMS voltage
levels across a selected LCD element. Also, see
Figure 9-3 and Table 9-1.
LOW BATTERY
DETECTOR
VCC
“OFF” segments may become visible at high LCD operating temperatures. A voltage with a -5 to -20mV/°C
temperature coefficient can be applied to VDISP to
accommodate the liquid crystal temperature operating
characteristics, if necessary.
Low Battery Detector
TC815
R1
VT
FIGURE 9-1:
+
R3
–
R2
1/3 BIAS LCD DRIVE
Comparator
VCC
To LCD
Annunciator
Selection
Logic
28
TC815
50k
VZ 6.2V
VH
R2
VT ≈ 7 X R1 + R2 = 6.2V
To Triplex
Segment Drive
Logic
VSSA
50k
VL
Set VDISP
For Proper VP
with Resistive
Divider
50k
9.0
TRIPLEX LIQUID CRYSTAL
DRIVE
The TC815 directly drives a triplexed liquid crystal display (LCD) using 1/3 bias drive (see Figure 9-1). All
data, decimal point, polarity and function annunciator
drive signals are developed by the TC815. A direct
connection to a triplex LCD display is possible without
external drive electronics. Standard and custom LCD
displays are readily available from LCD manufacturers.
The LCDs must be driven with an AC signal having
zero DC component for long display life. The liquid
crystal polarization is a function of the RMS voltage
appearing across the backplane and segment driver.
The peak drive signal applied to the LCD is: VCC VDISP.
If VDISP, for example, is set at a potential 3V below VCC,
the peak drive signal is:
VP = VCC – VDISP = 3V
An “OFF” LCD segment has an RMS voltage of Vp/3
across it or 1 volt. An “ON” segment has a 0.63Vp signal across it or 1.92V for VCC –VDISP = 3V.
Since the VDISP pin is available, the user may adjust
the “ON” and “OFF” LCD levels for various manufacturer’s displays by changing Vp. The liquid crystal
threshold voltage moves down with temperature.
© 2005 Microchip Technology Inc.
6
VDISP
VSSA
VP = VCC – VDISP
"OFF" = VP/3 RMS
11
"ON" =
VP RMS
3 3
9.1
LCD Displays
Although most users will design their own custom LCD
display, several manufacturers offer standard displays
for the TC815. Figure 9-3 shows a typical display available from Varitronix.
1. Varitronix Ltd.
4/F Liven House, 61-63, King Yip Street
Kwun Tong, Hong Kong
Tel: (852)2389-4317
Part No.: VIM 310-1 Pin Connector
VIM 310-2 Elastomer Connector
USA OFFICE:
VL Electronics/Varitronix
3250 Wilshire Blvd. Suite 1901
Los Angeles, CA 90010
Tel: (213) 738-8700
2. Adamant Kogyo Co., LTD
16-7, Shinden, 1-Chome, Adachi-Ku,
Tokyo, 123, Japan
Tel: Tokyo 919-1171
DS21474C-page 17
TC815
FIGURE 9-2:
TRIPLEX LCD DRIVE WAVEFORMS
Backplanes
1
2
3
4
5
6
Segments
a (FE – BP1)
"On"
b (BCP – BP1)
"On"
Backplanes
1
a
2
3
4
5
c (BCP – BP2)
"On"
6
BP1
b
d (AGD – BP3)
"On"
VP (3V)
lanes
f
g
e
Backp
BP2
c
d
BP1
e (FE – BP2)
"Off"
VP
VH
VL
BP20
BP3
FE
AGD
VP
VH
VL
BP30
BCP
11
VRMS =
3
3
3
3
VRMS =
g (AGD –
"On"
VRMS =
VP
3
11
VRMS =
–VL
–VH
–VP
VP
VH
VL
BP2) 0
–VL
–VH
–VP
VP
3
11
VRMS =
VRMS =
VP
3
11
VRMS =
f (FE – BP1)
"Off"
Waveforms to Generate
FIGURE 9-3:
Applied
RMS Voltage
VP
VH
0
–VL
–VH
–VP
VP
VH
VL
0
–VL
–VH
–VP
VP
VH
VL
0
–VL
–VH
–VP
VP
VH
VL
0
–VL
–VH
–VP
VP
VH
VL
0
–VL
–VH
–VP
VP
VH
VL
VP
3
VP
3
VP
3
11
3
VP
3
TYPICAL LCD DISPLAY CONFIGURATION TC815 TRIPLEX
50.8 (+0.3–0.1)
2.9
45.0 Viewing Area Min.
1.27
1.27
3.81
CL Between Pads 2.54 X 17 - 43.18
36
3
3
HOLD
LOΩ
10
6
5.5
a
1.4
AC
4
AUTO
0.5
Max.
3
1
b
f
10
2.4
P2
1
3.81
6.24
18
P3
mVA
c
d
P4
3
g
e
2
kΩ
30.48 (+0.3–0.1)
– +
22.86 (+0.3–0.1)
- MEM
10.0 Max.
18.0 Viewing Area Min.
19
0.2
0.2
Dimensions in mm (Not to Scale)
1.1
DS21474C-page 18
1.1
© 2005 Microchip Technology Inc.
TC815
TABLE 9-1:
PAD
BP1
BP2
BP3
PAD
COM1
COM2
COM3
1
2
BP1
/
/
19
/
/
/
/
BP2
/
20
/
/
/
3
/
/
BP3
21
/
/
/
4
/
LOΩ
A
22
/
/
/
5
/
W
V
23
/
/
/
6
HOLD
k
m
24
/
/
/
7
b1
c1
/
25
/
/
/
8
a1
g1
d1
26
/
/
/
9
f1
e1
/
27
/
/
/
10
b2
c2
P2
28
/
/
/
11
a2
g2
d2
29
/
/
/
12
f2
e2
/
30
/
/
/
13
b3
c3
P3
31
/
/
/
14
a3
g3
d3
32
/
/
/
15
f3
e3
/
33
/
/
/
16
b4
c4
P4
34
/
/
/
17
AC
Auto
35
/
/
/
/
36
/
/
/
18
10.0
–MEM
EXTERNAL CRYSTAL
The TC815 is designed to operate with a 32,768Hz
crystal. This frequency is internally divided by two to
give a 61.04µsec clock period. One conversion takes
8000 clock periods or 488.3 msec ( ≈ 2 conversions/
second). Integration time is 1638.5 clock periods or
100msec.
The 32kHz quartz crystal is readily available and inexpensive. The 32kHz crystal is commonly used in digital
clocks and counters.
Several crystal sources exist. A partial listing is:
• Statek Corporation
512 N. Main
Orange, CA 92668
(714) 639-7810
TWX: 910-593-1355
TELEX: 67-8394
• Fox Electronics
5570 Enterprise Parkway
Fort Myers, FL 33905
(941) 693-0099
Contact manufacturer for full specifications.
© 2005 Microchip Technology Inc.
DS21474C-page 19
TC815
11.0
“BUZZER” DRIVE SIGNAL
The buzzer drive signal for over range is shown in
Figure 11-1 The buzzer output is active for any reading
over 2000 counts in both manual and auto-range operation. The buzzer is activated during an extended resolution measurement. The BUZ signal swings from VCC
(Pin 28) to Digital Ground (Pin 58). The signal is at VCC
when not active.
The TC815 BUZ output (Pin 4) will drive a piezo electric
audio transducer. The signal is activated to indicate an
input overrange condition for current and voltage
measurements, or continuity during resistance
measurements.
During a resistance measurement, a reading less than
19 on any full scale range, causes a continuous 4kHz
signal to be output. This is used as a continuity
indication.
The BUZ output is also activated for 15msec whenever
a range change is made in auto-range or manual operation. Changing the type of measurement (voltage, current, or resistance) or measurement option (AC/DC,
Ω/LOΩ) will also activate the buzzer output for 15msec.
A range change during a current measurement will not
activate the buzzer output.
A voltage or current input measurement overrange is
indicated by a noncontinuous 4kHz signal at the BUZ
output. The LCD display MSD also flashes and the
three least significant digits are set to display zero.
FIGURE 11-1:
TC815 WAVEFORM FOR BUZZER OUTPUT
122ms
122ms
122ms
122ms
610ms 122ms
Digital Ground
1 Conversion
Noncontinuous Buzzer Signal Indicates Input Overrange
Power-up
VIN = 250mV
4000
4kHz Signal
8000
Change Range
12000
Change Range
Change Input
VIN = 3.2V
Change Range
1000 Clock Pulses
Integrate
Internal
TC815
Signals
100ms
1638.5CP
De-integrate
250CP
250CP
2,000V Range
In Range
2,000V Range
In Range
2500CP
250CP
3000CP
122ms
2000CP
Auto-Zero
Auto-Ranging
200mV Range
Over Range
Manual Range
200mV Range
Extended Range
2,000V Range
In Range
2,000V Range
Out of Range
BUZ
(Pin 4)
4kHz
4kHz
One Cycle of Over Range
Buzzer
Buzzer activated due
to Power-up
DS21474C-page 20
15ms
15ms
Due to Manual
Due to
Range Change
Range
Change
15ms
Due to
Range
Change
4kHz
4kHz
122ms 122ms122ms
Buzzer activated due to
Previous Conversion Over Range
610ms
Buzzer
activated due
to Previous
Over Range
© 2005 Microchip Technology Inc.
TC815
11.3
Vendors for piezo electric audio transducers are:
• Gulton Industries
Piezo Products Division
212 Durham Avenue
Metuchen, New Jersey 08840
(201) 548-2800
Typical P/Ns: 102-95NS, 101-FB-00
11.3.1
11.3.2
Display Decimal Point Selection
The TC815 provides a decimal point LCD drive signal.
The decimal point position is a function of the selected
full scale range, as shown in Table 11-1.
TABLE 11-1:
DECIMAL POINT SELECTION
1
*
9
* 9
INTEGRATION RESISTOR
SELECTION
The TC815 automatically selects one of two external
integration resistors. RVBUF (pin 55) is selected for
voltage and current measurement. RΩBUF (Pin 54) is
selected for resistance measurements.
• Taiyo Yuden (USA) Inc.
Arlington Center
714 West Algonquin Road
Arlington Heights, Illinois 60005
Typical P/Ns: CB27BB, CB20BB, CB355BB
11.1
Component Selection
* 9
RVIBUF SELECTION (PIN 55)
In auto-range operation, the TC815 operates with a
200mV maximum full scale potential at VI (Pin 44).
Resistive dividers at VR2 (Pin 41), VR3 (Pin 40), VR4
(Pin 43), and VR5 (Pin 42) are automatically switched
to maintain the 200V full scale potential.
In Manual mode, the Extended Operating mode is activated, giving a 300mV full scale potential at VI (Pin 44).
The integrator output swing should be maximized, but
saturations must be avoided. The integrator will swing
within 0.45V of VCC (Pin 28) and 0.5V of VSS (Pin 57)
without saturating. A ±2V swing is suggested. The
value of RVIBUF is easily calculated, assuming a worst
case extended resolution input signal:
Full Scale Range
DP3
DP2
DP1
2000V, 2000kΩ
OFF
OFF
OFF
200V, 200.0kΩ
OFF
OFF
ON
VINT
= Integrator swing = ±2V
= Integration time = 100msec
= Integration capacitor = 0.1µF
OFF
ON
OFF
tI
2V, 2.000kΩ
ON
OFF
OFF
CI
200V, 200.0Ω
OFF
OFF
OFF
VMAX = Maximum input at VI = 300mV
200mV, 200.0Ω
OFF
OFF
ON
20mA
OFF
ON
OFF
200mA
OFF
OFF
ON
20V, 20.00kΩ
EQUATION 11-1:
RVIBUF =
11.2
AC-to-DC Converter Operational
Amplifier
The TC815 contains an on-chip operational amplifier
that may be connected as a rectifier for AC-to-DC voltage and current measurements. Typical operational
amplifier characteristics are:
• Slew Rate: 1 V/µsec
• Unity-Gain Bandwidth: 0.4MHz
• Open Loop Gain: 44dB
11.3.3
VMAX(TI)
VINT(CI) = 150kΩ
RΩBUF SELECTION (PIN 54)
In ratiometric resistance measurements, the signal at
RX (pin 50) is always positive, with respect to analog
common. The integrator swings negative.
The worst case integrator swing is for the 200Ω range
with the manual, extended resolution option.
The input voltage, VX (Pin 50) is easily calculated (see
Figure 11-2):
• Output Voltage Swing (Load = 10kΩ) ± 1.5V
(Referenced to Analog Common)
VANCOM = Potential at Analog Common ≈ 2.7V
R8
= 220Ω
When the AC measurement option is selected, the
input buffer receives an input signal through switch
S14, rather than switch S11. With external circuits, the
AC Operating mode can be used to perform other types
of functions within the constraints of the internal operational amplifier. External circuits that perform true RMS
conversion, or a peak hold function are typical
examples.
RI
= 163.85Ω
RX
= 300Ω
RS
= Internal switch 33 resistance ≈ 600Ω
© 2005 Microchip Technology Inc.
EQUATION 11-2:
VCC - (VANCOM)RX
RΩBUF = (R + R + R + R ) = 0.63V
X
S
1
8
DS21474C-page 21
TC815
For a 3.1V integrator swing, the value of RΩBUF is
easily calculated:
VINT
= Integrator swing = 3.1V
tI
= Integration time = 100msec
CI
= Integration capacitor = 0.1µF
RXMAX
= 300Ω
VX MAX
= 700mV
EQUATION 11-3:
RΩBUF =
FIGURE 11-2:
VXMAX(TI)
= 200kΩ
CI(VINT)
RΩ CALCULATION (200Ω
MANUAL OPERATION)
VCC = 9V
SW33
RS ≈ 600Ω
11.5
Reference Voltage Adjustment
The TC815 contains a low temperature drift internal
voltage reference. The analog common potential
(Pin 29) is established by this reference. Maximum drift
is a low 75ppm/°C. Analog common is designed to be
approximately 2.6V below VCC (Pin 28). A resistive
divider (R18/R19, Functional Diagram) sets the TC815
reference input voltage (REFHI, Pin 34) to approximately 163.85mV.
With an input voltage near full scale on the 200mV
range, R19 is adjusted for the proper reading.
11.6
Display Hold Feature
The LCD will not be updated when HOLD (Pin 60) is
connected to GND (Pin 58). Conversions are made, but
the display is not updated. A HOLD mode LCD annunciator is activated when HOLD is low.
The LCD HOLD annunciator is activated through the
triplex LCD driver signal at Pin 13.
11.7
Flat Package Socket
Sockets suitable for prototype work are available. A
USA source is:
R1
163.85Ω
R2
220Ω
VX
R3
Resistive Ladder Networks
Resistor attenuator networks for voltage and resistance
measurements are available from:
Analog Common = VCC – 3V
• Caddock Electronics
1717 Chicago Avenue
Riverside, CA 92507
Tel: (714) 788-1700
TWX: 910-332-6108
Capacitors - CINT, CAZ and CREF
The integration capacitor, CINT, must have low dielectric absorption. A 0.1µF polypropylene capacitor is suggested. The auto-zero capacitor, CAZ, and reference
capacitor, CREF, should be selected for low leakage
and dielectric absorption. Polystyrene capacitors are
good choices.
DS21474C-page 22
11.8
300Ω
With a low battery voltage of 6.6V, analog common will
be approximately 3.6V above the negative supply terminal. With the integrator swinging down from analog
common toward the negative supply, a 3.1V swing will
set the integrator output to 0.5V above the negative
supply.
11.4
• Nepenthe Distribution
2471 East Bayshore, Suite 520
Palo Alto, CA 94303
(415) 856-9332
TWX: 910-373-2060
“CBQ” Socket, Part No. IC51-064-042
TABLE 11-2:
RESISTIVE LADDER
NETWORKS
Attenuator
Accuracy
Attenuator Type
Caddock
Part Number
0.1%
Voltage
1776-C441
0.25%
Voltage
1776-C44
0.25%
Resistance
T1794-204-1
© 2005 Microchip Technology Inc.
TC815
12.0
PACKAGING INFORMATION
12.1
Package Marking Information
Package marking data not available at this time.
12.2
Taping Form
Component Taping Orientation for 64-Pin PQFP Devices
User Direction of Feed
PIN 1
W
P
Standard Reel Component Orientation
for TR Suffix Device
Carrier Tape, Number of Components Per Reel and Reel Size
Package
64-Pin PQFP
Carrier Width (W)
Pitch (P)
Part Per Full Reel
Reel Size
32 mm
24 mm
250
13 in
Note: Drawing does not represent total number of pins.
12.3
Package Dimensions
64-Pin PQFP
7° MAX.
.009 (0.23)
.005 (0.13)
PIN 1
.018 (0.45)
.012 (0.30)
.041 (1.03)
.031 (0.78)
.555 (14.10)
.547 (13.90)
.687 (17.45)
.667 (16.95)
.031 (0.80) TYP.
.555 (14.10)
.547 (13.90)
.687 (17.45)
.667 (16.95)
.010 (0.25) TYP.
.120 (3.05)
.100 (2.55)
.130 (3.30) MAX.
Dimensions: mm (inches)
© 2005 Microchip Technology Inc.
DS21474C-page 23
TC815
SALES AND SUPPORT
Data Sheets
Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following:
1.
2.
3.
Your local Microchip sales office
The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277
The Microchip Worldwide Site (www.microchip.com)
Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using.
New Customer Notification System
Register on our web site (www.microchip.com/cn) to receive the most current information on our products.
DS21474C-page 24
© 2005 Microchip Technology Inc.
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED,
WRITTEN OR ORAL, STATUTORY OR OTHERWISE,
RELATED TO THE INFORMATION, INCLUDING BUT NOT
LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANTABILITY OR FITNESS FOR PURPOSE.
Microchip disclaims all liability arising from this information and
its use. Use of Microchip’s products as critical components in
life support systems is not authorized except with express
written approval by Microchip. No licenses are conveyed,
implicitly or otherwise, under any Microchip intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART,
PRO MATE, PowerSmart, rfPIC, and SmartShunt are
registered trademarks of Microchip Technology Incorporated
in the U.S.A. and other countries.
AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB,
PICMASTER, SEEVAL, SmartSensor and The Embedded
Control Solutions Company are registered trademarks of
Microchip Technology Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, dsPICDEM,
dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR,
FanSense, FlexROM, fuzzyLAB, In-Circuit Serial
Programming, ICSP, ICEPIC, Linear Active Thermistor,
MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM,
PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo,
PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode,
Smart Serial, SmartTel, Total Endurance and WiperLock are
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2005, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received ISO/TS-16949:2002 quality system certification for
its worldwide headquarters, design and wafer fabrication facilities in
Chandler and Tempe, Arizona and Mountain View, California in
October 2003. The Company’s quality system processes and
procedures are for its PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
© 2005 Microchip Technology Inc.
DS21474C-page 25
WORLDWIDE SALES AND SERVICE
AMERICAS
ASIA/PACIFIC
ASIA/PACIFIC
EUROPE
Corporate Office
2355 West Chandler Blvd.
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Tel: 480-792-7200
Fax: 480-792-7277
Technical Support:
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Tel: 61-2-9868-6733
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10/31/05
DS21474C-page 26
© 2005 Microchip Technology Inc.
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