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TC815
3-1/2 Digit Auto-Ranging A/D Converter with Triplex LCD Drive and Display Hold Function
Features
* 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
General Description
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. 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 200k 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.
Device Selection Table
Part Number TC815CBU Package 64-Pin PQFP Operating Temperature Range 0C to +70C
2002 Microchip Technology Inc.
DS21474B-page 1
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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
64-Pin PQFP
I DC/AC /LOW -MEM RVIBUF RANGE
RBUF
DGND
HOLD
ACVH
VSSA
AD0
AD1
64
63
62
61
60
59
58
57
56
55
54
53
52
51 50
49
CAZ
CFI
NC
RX
NC OHM
20mA
1
2
3
4
5
6
7
8 9
48
47 46
NC
CI
ACVL II VI VR4 VR5 VR2 VR3
BUZ XTAL1 XTAL2
45
44
43
42
VDISP
BP1 BP2
TC815
41
40
39
38
37
36
35
34
33
BP3 10
R5 R4 R3 R2 R1
REFHI
LO/A 11
/V 12 k/m/ HOLD 13
BCP0 14 AGD0 15 FE0 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
CREFH
ANALOG COM
AGD2
BCP1
AGD1
FE1
BCP2
FE2
BCP3
-MEM/BATT
NC
VSSD
AC/-/AUTO
RMREFH
RMREFL
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DS21474B-page 2
CREFL
VCC
2002 Microchip Technology Inc.
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LCD Bias -MEM AC 0.1F AUTO Audio Transducer 50 7 8 9 10 RX VDISP BP1 BP2 BP3 RMREFL R5 (/ 10,000) R4 (/ 1,000) R3 (/ 100) Ohms Range Attenuator Backplane Drivers Enable 32.768kHz ( 33kHz) + 9V - k mVA HOLD LO
-+
Tri-Plex LCD Display
If LCD Bias is Connected to DIG GND, Peak Drive Signal 5V.
R7/100k
0.01 F R6/100k 31
R8/220 (PTC)
Typical Application and Test Circuit
2002 Microchip Technology Inc.
11 12 13 25 26 24 23 22 21 20 19 18 16 15 14 45 LO/AV 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
SSA
Ohms Input
R5/1.6385M 39
R4/163.85k 38
39pf
Positive Temperature Coefficient Resistor
R3/16.385k 37
VSSD 27 Digital GND 58 V 20mA 3 SIB
Z1 6.2V 45 I I D4
R2/1638.5 36 R2 (/ 10) R1/163.85 35 R1 (/ 1)
Current Input
20mA
R15 D3 9
TC815 3-1/2 Digit Auto-Ranging DMM with HOLD Function
OHMS 2
20mA 200mA V SIA I 63 20mA 200mA DC/AC or /LOW 62 Manual RANGE Change 59 -MEM 61
200mA
R16 1
Voltage Input
R14/9.9M
R13 500k 44
RMREFH 30 ANALOG CAZ INT HOLD CIF CREFL CREFH COM REFHI 49 47 60 51 32 33 29 34 CAZ CINT 0.1F 0.1F R20 100 k CREF 0.1F C6 0.01F 153.850mV R19/5k R18/24k To VCC
Common
VI (/1) R12/1.11M 41 VR2 (/10) Voltage Range Attenuator R11/101k 40 VR3 (/100) R10/10k 43 VR4 (/1,000) ADO VR5 (/10,000) ADI ACVH ACVL RBUF RVIBUF 42 53 52 56 46 54 55 R21/2.2M R9/1k C1/1F 200 150 R22/470k k k C4/f C2/0.22F 4.7f -+ D2 R23/10k R24/10k D1 C5/1f -+ R26/3k R27/2k
RBUF RVIBUF
TC815
DS21474B-page 3
*Not Required when Resistor Network is used.
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 70C) 64-Pin Plastic Flat Package ...........................1.14W Operating Temperature Range: Commercial Package (C) .................... 0C to +70C Storage Temperature Range .............. -65C to +150C
TC815 ELECTRICAL SPECIFICATIONS
Electrical Characteristics: VA = 9V, TA = +25C, unless otherwise specified (see Typical Application and Test Circuit Figure). Symbol Parameter Zero Input Reading Input Resistor Min -0000 -0001 -0000 RE Rollover Error -- -- -- NL IIN EN Linearity Error Input Leakage Current Input Noise AC Frequency Error Open Circuit Voltage Open Circuit Voltage VCOM VCTC Analog Common Voltage Common Voltage Temperature Coefficient Display Multiplex Rate VIL Low Logic Input -- -- -- -- -- -- -- 2.5 -- -- -- Typ 0000 -- 0000 -- -- -- -- -- 20 1 5 570 285 2.6 -- 100 -- Max +0000 +0001 +0000 1 Count 3 1 1 10 -- -- -- 660 350 3.3 50 -- 1 Count pA Vp-p % % mV mV V ppm/C Hz V 20mA, AC, I, LOW , HOLD Range, -MEM, OHMs (Relative to DGND Pin 58) 20mA, AC, I, LOW , HOLD Range, -MEM, OHMs (Relative to DGND Pin 58) VCC to VSSA BW = 0.1 to 10Hz 40Hz to 500Hz 40Hz to 200Hz Excludes 200 Range for OHM Measurements Excludes 200 Range for LO OHM Measurement (V+ - VCOM) Unit Test Conditions
Digital Reading 200mV Range w/o 10M Input Digital Reading 200mV Range w/10M Input Digital Reading 20mA and 200mA Range 200mV Range w/o 10M Input Resistor 200mV Range w/10M Input 20mA and 200mA Range Best Case Straight Line
Logic 1 Pull-up Current
--
25
--
A
Buzzer Drive Frequency Low Battery Flag Voltage Operating Supply Current
-- 6.3 --
4 6.6 0.8
-- 7.0 1.5
kHz V mA
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DS21474B-page 4
2002 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
Symbol NC OHM 20mA BUZ Description Logic Input. "0" (Digital Ground) for resistance measurement. Logic Input. "0" (Digital Ground) for 20mA full scale current measurement. Audio frequency, 4kHz, output for continuity indication during resistance measurement. 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. 32.768kHz Crystal Connection. 32.768kHz Crystal Connection. Sets peak LCD drive signal: VP - VDD - VDISP. VDISP may also be used to compensate for temperature variation of LCD crystal threshold voltage. LCD Backplane #1. LCD Backplane #2. LCD Backplane #3. LCD Annunciator segment drive for low ohms resistance measurement and current measurement. 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). LCD segment drive for "a," "g," "d" segments of LSD. LCD segment drive for "f" and "e" segments of LSD. No connection. LCD segment drive for "b," "c" segments and decimal point of 2nd LSD. LCD segment drive for "a," "g," "d" segments of 2nd LSD (Ten's digit). 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). LCD segment drive for "a," "g," "d" segments of 3rd LSD. 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). LCD annunciator drive signal for AC measurements, polarity, and auto-range operation. LCD annunciator drive signal for low battery indication and Memory (Relative Measurement) mode. Negative battery supply connection for internal digital circuits. Connect to negative terminal of battery. Positive battery supply connection. Analog circuit ground reference point. Nominally 2.6V below VCC. Ratiometric (Resistance measurement) reference high voltage. Ratiometric (Resistance measurement) reference low voltage. Reference capacitor negative terminal CREF 0.1f. Reference capacitor positive terminal CREF 0.1f. Reference voltage for voltage and current measurement; nominally 163.85mV.
Pin Number (64-Pin Plastic) Quad Flat Package 1 2 3 4
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
XTAL1 XTAL2 VDISP BP1 BP2 BP3 LO/A /V k/m/HOLD BCP0 (One's digit) ADG0 FE0 NC BCP1 AGD1 FE1 BCP2 AGD2 FE2 BCP3 AC/-/AUTO -MEM/BATT VSSD VCC ANALOG COM RMREFH RMREFL CREFL CREFH REFHI
2002 Microchip Technology Inc.
DS21474B-page 5
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TC815
TABLE 2-1: PIN FUNCTION TABLE (CONTINUED)
Symbol R1 R2 R3 R4 R5 VR3 VR2 VR5 VR4 VI II ACVL CI NC CAZ RX CFI AD1 AD0 RBUF RVIBUF ACVH VSSA DGND RANGE HOLD -MEM DS/AC /LOW I NC Description Standard resistor connection for 200 full scale. Standard resistor connection for 2000 full scale. Standard resistor connection for 20k full scale range. Standard resistor connection for 200k full scale range. Standard resistor connection for 2000k full scale range. Voltage measurement / 100 attenuator. Voltage measurement / 10 attenuator. Voltage measurement / 10,000 attenuator. Voltage measurement / 1000 attenuator. Unknown voltage input / 1 attenuator. Unknown current input. Low output of AC to DC converter. Integrator capacitor connection. Nominally 0.1f. (Low dielectric absorption. Polypropylene dielectrics suggested.) No connection. Auto-zero capacitor connection; nominally 0.1f. Unknown resistance input. Input filter connection. Negative input of internal AC to DC operational amplifier. Output of internal AC to DC operational amplifier. Active buffer output for resistance measurement. Integration resistor connection. Integrator resistor nominally 220k. Active buffer output for voltage and current measurement. Integration resistor connection. Integration resistor nominally 150k. Positive output of AC to DC converter. Negative supply connection for analog circuits. Connect to negative terminal of 9V battery. Internal logic digital ground. The logic "0" level. Nominally 4.7V below VCC. Input to set manual operation and change ranges. Input to hold display. Connect to DIG GND. Input to enter Memory Measurement mode for relative measurements. The two LSD's are stored and subtracted from future measurements. Input that selects AC or DC option during voltage/current measurements. For resistance measurements, /LOW, the ohms or low power (voltage) ohms option can be selected. Input to select current measurement. Set to logic "0" (Digital ground) for current measurement No connection. Pin Number (64-Pin Plastic) Quad Flat Package 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
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DS21474B-page 6
2002 Microchip Technology Inc.
TC815
3.0
3.1
DETAILED DESCRIPTION
Resistance, Voltage, Current Measurement Selection
The low power ohms measurement is not available on the 100 full scale range. Open circuit voltage on this range is below 2.8V. The standard resistance values are listed in Table 3-2. R8, a positive temperature coefficient resistor, and the 6.2V zener Z1 in Figure 3-1, provide input voltage protection during ohms measurements.
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 3-2:
OHMS RANGE LADDER NETWORK
Standard Resistance 163.85 (R1) 1638.5 k (R2) 16,385 (R3) 16385 (R4) 1,638,500 (R5) Low Power Ohms Mode NO YES YES YES YES
Full Scale Range 200 2000 20k 200k 2,000k
TABLE 3-1:
MEASUREMENT SELECTION LOGIC
Selected Measurement Voltage Resistance Current Voltage
Function Select Pin OHM (Pin 2) 0 0 1 1 I (Pin 63) 0 1 0 1
3.3
Ratiometric Resistance Measurements
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).
3.2
Resistance Measurements (Ohms and Low Power Ohms)
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 200 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.
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 /LOW (Pin 62) input selects the Low Power Ohms Measurement mode. For low power ohms measurements, /LOW (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, LOW, will be activated. On power-up, the Low Power Ohms mode is not active. If the Manual mode has been selected, toggling /LOW 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.
TABLE 3-3:
Full Scale Range 200k 2k 20k 200k 2M
REFERENCE RESISTORS
Reference Resistor 163.85 1638.5 16385 163850 1638500 /Count 0.1 1 10 100 1000
2002 Microchip Technology Inc.
DS21474B-page 7
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TC815
FIGURE 3-1: RATIOMETRIC RESISTANCE MEASUREMENT FUNCTIONAL DIAGRAM
9V VSSD 30 R5/1638500 R4/163850 R3/16385 39 38 37 S29 S30 S31 S32 S33 /10k /1k /100 /10 /1 VA Ohms 10k 57 VSSA VCC 28 30 * HI
R2/1638.5 36 R1/163.85
~1.5k Low Ohms
* LO VCC
R18 24k
/10k /1k /100 /10 /1
35
~1.5kV
Voltage Reference + - VCC - 2.6V
REFHI 34
5k
S24 S25 S26 S27 S28 R8 220 33 CREF 0.1F 32 31 50 R6/100k R7/100k 50 RX Unknown V* S12 1 1 S18 S21 DE S13 INT * ( + DC) DE DE * DE * S20 DE S19
29
S23
VCC - 2.8V
DE +
Analog Common
TC815
Buffer
S37 S36 S34
S35
Integrator
Comparator
RBUF 54 55
49 RVIBUF
CAZ 0.1F CINT 0.1F
47
150k 220k
FIGURE 3-2:
RESISTANCE MEASUREMENT ACCURACY SET BY EXTERNAL STANDARD RESISTOR
VA 0.64V for Ohms 0.32V for LO Ohms + CREF 100 k VR VR
Example: 200k Full Scale Measurement

(a ) V R = (b) VX =
163.85k ------------------------------------------------ x0.64 163.85 + 220 + R X RX -------------------------------------------------------------- x0.64 163.85k + 220 + R X

RS 16.385k
(c) "Ramp Up Voltage" = "Ramp Down Voltage" . VX VX . . ----------------xT I = ----------------T DE ( RICI) ( RI C I )
220 VX Unknown 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
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DS21474B-page 8
2002 Microchip Technology Inc.
TC815
3.4 Voltage Measurement
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. The divider leg resistors give a 200mV signal VI (Pin 44) for full scale voltages from 200mV to 2000V. For applications which do not require a 10m input impedance, the divider network impedances may be lowered. This will reduce voltage offset errors induced by switch leakage currents.
FIGURE 3-3:
TC815 ANALOG SECTION
0.1F R7/100k RX 50 RMREFL 31 R 5 39 R 4 38 R 3 37 R 2 36 R 1 35 S12 V * 1/1 S21 DE * S24 W* 1/10k * S25 1/1k * S26 1/100 * S27 1/10 S28 *1/1 VCC 10k S44 * HI 1.5k VCC S43 + * LOW 2.8V REF AMP - 1.5k + - 20mA R15/9 200mA R16/1 I I 45 D3 D4 S22 DE * R14/9.9M VI 44 R13/500k* S1 V* V* V* V* 1/10 1/100 1/1 1/10k k S8 S9 S6 S7 S2 S3 S4 S5 AC-to-DC Converter Op Amp + - S11 +AC S16 DE+ S17 DE51 CIF R20/100k 0.01F C6 V*1/10 S20 DE R11/101k VR3 40 R10/10k R9/1k 4.7F VR4 43 VR2 42 V*1/100 V*1/1k S18 DE V*1/10k S19 DE+ CREFH 32 CREFL 0.1F 33 CREFH V*1/1 S22 DE * S33 S32 S31 S30 S29 * * * * * 1/1 1/10 1/100 1/1k 1/10k VCC +1 S10 30 VCC RMREFH
Ohms Input
TC815
R8/220 (PTC) 0.01F
R6/100k R5/1.638M
R4/163.85k R3/16385 Z1 6.2V Current Input R2/1638.5 R1/163.85
R18/24k
R19/5k 29 ANALOG COM 34 REFHI 163.85mV
Voltage Input
*Not required when Resistor Network is used. R12/1.11M VR2 41
Common
53 ADO
D1
D2
R22 470 kW + C4 1F
R24 C3 10k + 1F
R23 10k
R21 2.2 M 52 C2 ADI 0.22 F ACVH 56 C1/1F S14 INT* *AC + ACVL 46 S40 INT* *AC S15 AZ - - S35 S34 54 RBUF RBUF S37 Buffer S38 AZ - S13 INT*( +DC)
R26 33k R27/2k
S39 INT+ +DC
Comparator Integrator 55 49 R RVI C BUF BUF AZ 220 0.01F k 150 k CAZ 47 INT 0.01F CINT
2002 Microchip Technology Inc.
+ + To Digital Section
DS21474B-page 9
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TC815
3.5 Current Measurement 3.6
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 10 resistor is used. The 200mA range needs a 1 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.
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.
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DS21474B-page 10
2002 Microchip Technology Inc.
TC815
4.0 CONVERSION TIMING
FIGURE 4-1:
TC815
Auto-Zero Phase
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 61.04sec. 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. The integration time is fixed at 1638.5 clock periods or 100msec. This gives rejection of 50/60Hz AC line noise. 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.
BASIC TC815 CONVERSION TIMING
Signal Integrate Phase Reference De-integrate Phase Next Conversion Auto-Zero Cycle Extended Resolution Zero Crossing
Min. Auto-Zero Time 3361.5TP
Fixed 1638.5 TP TI
*Max 3000.0 TP TDE To Input Signal *In Auto-Range Operation Maximum is 2000TP and Minimum Auto-Zero time i s 4361.5TP
TCONV 8000 TP
External Crystal = 32.768kHz Internal Clock Period = TP = 2/32.768 = 61.04sec Total Conversion Time = TCONV = 8000 (TP) = 488.3mec 2 Conv/Sec. Integration Time = TI = 1638.5 (TP) = 100.0msec. Maximum Reference De-integration Time = TDE = 3000 (TP) = 183.1msec (Manual Extended Resolution) Minimum Auto-Zero Time = (8000-3000-1638.5) (TP) = 205.1msec (Manual, Extended Resolution) = (8000-2000-1638.5) (TP) = 266.2msec (Auto-Range)
2002 Microchip Technology Inc.
DS21474B-page 11
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TC815
5.0 MANUAL RANGE SELECTION
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 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 (voltage or resistance), or measurement option (AC/ DC, /LO) changes. This causes the TC815 to return to auto-ranging operation. 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.
TABLE 5-1:
MANUAL RANGE OPERATION
DC Volts AC Volts 18.2V Display "1"00.0V 1.000V "1"0.00V 23.5V Range 2V 20V -- -- Range "1"000V 18.20V -- -- Ohm 18.2k Display 200 2k 20k -- Range "1"00.0 "1".000k 18.20 -- Range 2k 10k 200k 2000k LO Ohm 2.35M Display "1".000k "1".0.00k "1".00.0k "1"350k
Input Range 200mV Power-on Auto-Range Operation Manual Operation 2V 20V 200V
23.5V
DC Volts Input 23.5V # of Range Changes (See Note 4)
AC Volts 18.2V
Ohm 18.2k
LO Ohm 2.35M
Range
Display
Range
Range
Display
Range
Range
Display
1 2 3 4 5 6 7 8
200V 200mV 2V 20V 200V 1000V 200mV 2V
23.5V "1"00.0V 1.000V "1"3.50V 23.5V 24V "1"00.0mV "1".000V
20V 2V 20V 20V 600V 2V 20V 200V
18.20V "1".000V 18.20V 18.2V 19V "1".000V 18.20V 18.2V
20k 200 2k 20k 200k 2000k 200k 2k
18.20V "1"00.0k "1"000k 18.20k 18.2k 19k "1"00.0 "1".000k
2000k 2k 20k 200k 2000k 2k 20k 200k
"1"350k "1".000k "1"0.00k "1"00.0k "1"350k "1".000k "1"0.00k "1"00.0k
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.
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DS21474B-page 12
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TC815
FIGURE 5-1: MANUAL RANGE SELECTION: RESISTANCE MEASUREMENTS
Manual Range Select Continuity Indicator Output 4kHz Audio Frequency Continuous 4kHz Buzzer Yes Is RX < 19 ? No Is RX > 3000 ? No Is RX > 2000 ? No Display True Reading *Mode also operates when Auto-Ranging Operation is selected and 2M < RX < 2.999M Yes
FIGURE 5-3:
MANUAL RANGE SELECTION: VOLTAGE MEASUREMENTS
TC815
Output Noncontinuous 4kHz Audio Frequency
Range Select
TC815
Over Range Indicator Display "1" 000 "1" = > Flashing MSD Yes* Display Last 3 Digits and Flash MSD Extended Resolution Feature
Over Range Indicator
Is VX > 3000 ? No
Yes
Display "1" 000 "1" = > Flashing MSD
Is VX > 2000 ? No
Yes
Display Last 3 Digits and Flash MSD Extended Resolution Feature
Display True Reading
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.
5.1
Extended Resolution Manual Operation
FIGURE 5-2:
MANUAL RANGE SELECTION: CURRENT MEASUREMENTS
Range Select Yes
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 2000k 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.
TC815
Output 4kHz Audio Frequency Over Range Indicator
Is IX > 3000 ? No
Yes
Display "1" 000 "1" = > Flashing MSD
Is I > 2000 X ? No
Yes
Display Last 3 Digits and Flash MSD Extended Resolution Feature
Display True Reading
2002 Microchip Technology Inc.
DS21474B-page 13
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TC815
6.0 -MEM OPERATING MODE 7.0
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:
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, /LO). 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 10M 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 200 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 2k. 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 2000k 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.
EXAMPLE 6-1:
IN AUTO-RANGING
RI (N) = 18.21k (20k Range) = > Display 18.21k MEM = > Store 0.21k RI (N+1) = 19.87k (20k Range) = > Display 19.87 - 0.21 = 19.66k RI (N+2) = 22.65k (200k Range) = > Display 22.7k and MEM disappears
EXAMPLE 6-2:
IN FIXED RANGE (200.0 FULL SCALE)
RI (N) = 18.21k = > Display 18.2k MEM = > Store 8.2 RI (N+1) = 36.7 = > Display 36.7 - 8.2 = 28.5 RI (N+2) = 5.8 = > Display 5.8 = 2.4* *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 MEM = > Store 0.51V 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, /LO) or range is changed. The LCD -MEM annunciator will be off in normal operation. 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.
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TC815
FIGURE 7-1: AUTO-RANGE OPERATION: VOLTAGE MEASUREMENT
N = 0 if DC N = 1 if AC
TC815
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
N=N-1
VX < 180 ? No
Yes
N = 0 if DC N = 1 if AC Yes
VX > 2000 ? Yes No N=4 ? Yes
No
Display Voltae (VX)
K=K+1
N=N+1
VX > 3000 ?
No
Display "1" XXX Flash MSD
Yes
Activate Buzzer Over Range
Display "1" 000 Flash MSD
Start: Power-on, Function or Measurement Option Change
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DS21474B-page 15
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TC815
FIGURE 7-2: AUTO-RANGE OPERATION: RESISTANCE MEASUREMENT
N = 0 if N = 1 if LO
TC815
N = 0: 200.0 Full Scale Range N = 1: 2,000k Full Scale Range
Remaining in Range Selected during the Kth Conversion Kth Conversion
RX = (1/10N) RIN Continuity Indicator Activate Buzzer Continuous 4kHz Signal Yes RX < 19 ? No No RX < 180 ? No Yes N = 0 if N =1 if LOW Yes N=N-1
RX >2000 ? Yes No N=N+1 N=4 ? Yes No
Display Resistance
K=K+1
Over Range Display "1" XXX Flash MSD Extended Resolution Display "1" 000 Flash MSD
RX >3000 ?
Yes Start: Power-on, Function or Measurement Option Change
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DS21474B-page 16
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TC815
8.0 LOW BATTERY DETECTION CIRCUIT
"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. 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 150k. 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.
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:
LOW BATTERY DETECTOR
VCC R1
Low Battery Detector
TC815
VT R3 R2 - VZ 6.2V R2 VT 7 X R1 + R2 = 6.2V VSSA
VH To Triplex Segment Drive Logic VL 50k Set VDISP For Proper VP with Resistive Divider 6 VSSA VP = VCC - VDISP "OFF" = VP/3 RMS 11 "ON" = VP RMS 33 VDISP 50k
FIGURE 9-1:
+ Comparator To LCD Annunciator Selection Logic
1/3 BIAS LCD DRIVE
VCC 28
TC815
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.
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
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DS21474B-page 17
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TC815
FIGURE 9-2: TRIPLEX LCD DRIVE WAVEFORMS
Backplanes
1 2 3 4 5 6
Segments
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
Applied RMS Voltage
VRMS = 3 11 3 VP
a (FE - BP1) "On"
b (BCP - BP1) "On"
VRMS = 3
11 3
VP
Backplanes
1 2 3 4 5 6
c (BCP - BP2) "On"
VRMS = 3
11 3
VP
a f g e c d
BP3 FE AGD BCP
BP1
b
lanes
VP (3V) BP1 VP VH VL BP20 VP VH VL BP30
d (AGD - BP3) "On"
VRMS = 3
11 3
VP
Backp
BP2
e (FE - BP2) "Off"
VRMS =
VP 3
f (FE - BP1) "Off"
g (AGD - "On" Waveforms to Generate
-VL -VH -VP VP VH VL BP2) 0 -VL -VH -VP
VRMS =
VP 3
VRMS = 3
11 3
VP
FIGURE 9-3:
TYPICAL LCD DISPLAY CONFIGURATION TC815 TRIPLEX
50.8 (+0.3-0.1) 45.0 Viewing Area Min. 1.27 1.27 CL Between Pads 2.54 X 17 - 43.18 2.9 3.81
19
36
18.0 Viewing Area Min.
- MEM
-+ 6
3 10 5.5
HOLD
3
LO 22.86 (+0.3-0.1) 30.48 (+0.3-0.1) 0.2 0.2 1.1 1.1
10.0 Max.
a AC 1.4 10 4 0.5 Max. 18 AUTO P4 3 1 P3 2 P2 1 e c d 2.4 f g mVA b k 3
6.24
Dimensions in mm (Not to Scale)
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DS21474B-page 18
2002 Microchip Technology Inc.
3.81
TC815
TABLE 9-1:
PAD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 BP1 BP1 / / / / HOLD b1 a1 f1 b2 a2 f2 b3 a3 f3 b4 AC -MEM BP2 / BP2 / LO W k c1 g1 e1 c2 g2 e2 c3 g3 e3 c4 BP3 / / BP3 A V m / d1 / P2 d2 / P3 d3 / P4 Auto / PAD 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 COM1 / / / / / / / / / / / / / / / / / / COM2 / / / / / / / / / / / / / / / / / / COM3 / / / / / / / / / / / / / / / / / /
10.0
EXTERNAL CRYSTAL
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.
The TC815 is designed to operate with a 32,768Hz crystal. This frequency is internally divided by two to give a 61.04sec 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.
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DS21474B-page 19
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TC815
11.0 "BUZZER" DRIVE SIGNAL
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. 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. 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 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, /LO) will also activate the buzzer output for 15msec. A range change during a current measurement will not activate the buzzer output.
FIGURE 11-1:
TC815 WAVEFORM FOR BUZZER OUTPUT
122ms 122ms 122ms 122ms 610ms 122ms
Digital Ground 1 Conversion 4kHz Signal
Power-up VIN = 250mV 4000 8000 12000
Noncontinuous Buzzer Signal Indicates Input Overrange
Change Range Change Range Change Range Change Input VIN = 3.2V
1000 Clock Pulses Integrate 100ms 1638.5CP De-integrate 250CP 122ms 2000CP Auto-Zero 250CP 2500CP 250CP 3000CP
Internal TC815 Signals
Auto-Ranging 200mV Range Over Range BUZ (Pin 4) 4kHz 4kHz 15ms 15ms Due to Manual Due to Range Change Range Change 2,000V Range In Range 2,000V Range In Range
Manual Range 200mV Range Extended Range 2,000V Range In Range 2,000V Range Out of Range
One Cycle of Over Range Buzzer Buzzer activated due to Power-up
15ms Due to Range Change
4kHz 4kHz 122ms 122ms122ms
610ms Buzzer activated due to Previous Over Range
Buzzer activated due to Previous Conversion Over Range
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DS21474B-page 20
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TC815
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 * Taiyo Yuden (USA) Inc. Arlington Center 714 West Algonquin Road Arlington Heights, Illinois 60005 Typical P/Ns: CB27BB, CB20BB, CB355BB
11.3
11.3.1
Component Selection
INTEGRATION RESISTOR SELECTION
The TC815 automatically selects one of two external integration resistors. RVBUF (pin 55) is selected for voltage and current measurement. RBUF (Pin 54) is selected for resistance measurements.
11.3.2
RVIBUF SELECTION (PIN 55)
11.1
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.
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: VINT tI CI = Integrator swing = 2V = Integration time = 100msec = Integration capacitor = 0.1F
TABLE 11-1:
DECIMAL POINT SELECTION
1 * DP3 OFF OFF OFF ON OFF OFF OFF OFF 9 *9 DP2 OFF OFF ON OFF OFF OFF ON OFF *9 DP1 OFF ON OFF OFF OFF ON OFF ON
Full Scale Range 2000V, 2000k 200V, 200.0k 20V, 20.00k 2V, 2.000k 200V, 200.0 200mV, 200.0 20mA 200mA
VMAX = Maximum input at VI = 300mV
EQUATION 11-1:
RVIBUF = VMAX(TI) = 150k VINT(CI)
11.2
AC-to-DC Converter Operational Amplifier
11.3.3
RBUF SELECTION (PIN 54)
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/sec * Unity-Gain Bandwidth: 0.4MHz * Open Loop Gain: 44dB * Output Voltage Swing (Load = 10k) 1.5V (Referenced to Analog Common) 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.
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 200 range with the manual, extended resolution option. The input voltage, VX (Pin 50) is easily calculated (see Figure 11-2): VANCOM = Potential at Analog Common 2.7V R8 RI RX RS = 220 = 163.85 = 300 = Internal switch 33 resistance 600
EQUATION 11-2:
RBUF = VCC - (VANCOM)R X = 0.63V (R X + RS + R1 + R8)
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DS21474B-page 21
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TC815
For a 3.1V integrator swing, the value of RBUF is easily calculated: VINT tI CI R XMAX VX MAX = Integrator swing = 3.1V = Integration time = 100msec = Integration capacitor = 0.1F = 300 = 700mV
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.
EQUATION 11-3:
RBUF = VXMAX(T I) = 200k CI(VINT)
11.6
Display Hold Feature
FIGURE 11-2:
VCC = 9V
SW33
R CALCULATION (200 MANUAL OPERATION)
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.
RS 600
11.7
Flat Package Socket
Sockets suitable for prototype work are available. A USA source is:
R1
163.85
R2
220
* 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
VX R3 300
11.8
Resistive Ladder Networks
Resistor attenuator networks for voltage and resistance measurements are available from: * Caddock Electronics 1717 Chicago Avenue Riverside, CA 92507 Tel: (714) 788-1700 TWX: 910-332-6108
Analog Common = VCC - 3V
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.
TABLE 11-2:
RESISTIVE LADDER NETWORKS
Attenuator Type Voltage Voltage Resistance Caddock Part Number 1776-C441 1776-C44 T1794-204-1
11.4
Capacitors - C INT, CAZ and C REF
Attenuator Accuracy 0.1% 0.25% 0.25%
The integration capacitor, CINT, must have low dielectric absorption. A 0.1F 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.
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DS21474B-page 22
2002 Microchip Technology Inc.
TC815
12.0
12.1
PACKAGING INFORMATION
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 Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size
64-Pin PQFP
32 mm
24 mm
250
13 in
Note: Drawing does not represent total number of pins.
12.3
Package Dimensions
64-Pin PQFP
PIN 1 .018 (0.45) .012 (0.30) .009 (0.23) .005 (0.13)
7 MAX.
.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)
2002 Microchip Technology Inc.
DS21474B-page 23
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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.
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DS21474B-page 24
2002 Microchip Technology Inc.
TC815
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. 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 intellectual property rights.
Trademarks The Microchip name and logo, the Microchip logo, FilterLab, KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER, PICSTART, PRO MATE, SEEVAL and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, microPort, Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM, MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select Mode and Total Endurance are trademarks of Microchip Technology Incorporated in the U.S.A. Serialized Quick Turn Programming (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. (c) 2002, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received QS-9000 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona in July 1999 and Mountain View, California in March 2002. The Company's quality system processes and procedures are QS-9000 compliant for its PICmicro (R) 8-bit MCUs, KEELOQ(R) code hopping devices, Serial EEPROMs, microperipherals, non-volatile memory and analog products. In addition, Microchip's quality system for the design and manufacture of development systems is ISO 9001 certified.
2002 Microchip Technology Inc.
DS21474B-page 25
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WORLDWIDE SALES AND SERVICE
AMERICAS
Corporate Office
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500 Sugar Mill Road, Suite 200B Atlanta, GA 30350 Tel: 770-640-0034 Fax: 770-640-0307
Singapore
Microchip Technology Singapore Pte Ltd. 200 Middle Road #07-02 Prime Centre Singapore, 188980 Tel: 65-6334-8870 Fax: 65-6334-8850
Boston
2 Lan Drive, Suite 120 Westford, MA 01886 Tel: 978-692-3848 Fax: 978-692-3821
China - Chengdu
Microchip Technology Consulting (Shanghai) Co., Ltd., Chengdu Liaison Office Rm. 2401, 24th Floor, Ming Xing Financial Tower No. 88 TIDU Street Chengdu 610016, China Tel: 86-28-6766200 Fax: 86-28-6766599
Taiwan
Microchip Technology Taiwan 11F-3, No. 207 Tung Hua North Road Taipei, 105, Taiwan Tel: 886-2-2717-7175 Fax: 886-2-2545-0139
Chicago
333 Pierce Road, Suite 180 Itasca, IL 60143 Tel: 630-285-0071 Fax: 630-285-0075
Dallas
4570 Westgrove Drive, Suite 160 Addison, TX 75001 Tel: 972-818-7423 Fax: 972-818-2924
China - Fuzhou
Microchip Technology Consulting (Shanghai) Co., Ltd., Fuzhou Liaison Office Unit 28F, World Trade Plaza No. 71 Wusi Road Fuzhou 350001, China Tel: 86-591-7503506 Fax: 86-591-7503521
EUROPE
Denmark
Microchip Technology Nordic ApS Regus Business Centre Lautrup hoj 1-3 Ballerup DK-2750 Denmark Tel: 45 4420 9895 Fax: 45 4420 9910
Detroit
Tri-Atria Office Building 32255 Northwestern Highway, Suite 190 Farmington Hills, MI 48334 Tel: 248-538-2250 Fax: 248-538-2260
China - Shanghai
Microchip Technology Consulting (Shanghai) Co., Ltd. Room 701, Bldg. B Far East International Plaza No. 317 Xian Xia Road Shanghai, 200051 Tel: 86-21-6275-5700 Fax: 86-21-6275-5060
Kokomo
2767 S. Albright Road Kokomo, Indiana 46902 Tel: 765-864-8360 Fax: 765-864-8387
France
Microchip Technology SARL Parc d'Activite du Moulin de Massy 43 Rue du Saule Trapu Batiment A - ler Etage 91300 Massy, France Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79
Los Angeles
18201 Von Karman, Suite 1090 Irvine, CA 92612 Tel: 949-263-1888 Fax: 949-263-1338
China - Shenzhen
Microchip Technology Consulting (Shanghai) Co., Ltd., Shenzhen Liaison Office Rm. 1315, 13/F, Shenzhen Kerry Centre, Renminnan Lu Shenzhen 518001, China Tel: 86-755-2350361 Fax: 86-755-2366086
New York
150 Motor Parkway, Suite 202 Hauppauge, NY 11788 Tel: 631-273-5305 Fax: 631-273-5335
Germany
Microchip Technology GmbH Gustav-Heinemann Ring 125 D-81739 Munich, Germany Tel: 49-89-627-144 0 Fax: 49-89-627-144-44
San Jose
Microchip Technology Inc. 2107 North First Street, Suite 590 San Jose, CA 95131 Tel: 408-436-7950 Fax: 408-436-7955
Hong Kong
Microchip Technology Hongkong Ltd. Unit 901-6, Tower 2, Metroplaza 223 Hing Fong Road Kwai Fong, N.T., Hong Kong Tel: 852-2401-1200 Fax: 852-2401-3431
Italy
Microchip Technology SRL Centro Direzionale Colleoni Palazzo Taurus 1 V. Le Colleoni 1 20041 Agrate Brianza Milan, Italy Tel: 39-039-65791-1 Fax: 39-039-6899883
Toronto
6285 Northam Drive, Suite 108 Mississauga, Ontario L4V 1X5, Canada Tel: 905-673-0699 Fax: 905-673-6509
India
Microchip Technology Inc. India Liaison Office Divyasree Chambers 1 Floor, Wing A (A3/A4) No. 11, O'Shaugnessey Road Bangalore, 560 025, India Tel: 91-80-2290061 Fax: 91-80-2290062
United Kingdom
Arizona Microchip Technology Ltd. 505 Eskdale Road Winnersh Triangle Wokingham Berkshire, England RG41 5TU Tel: 44 118 921 5869 Fax: 44-118 921-5820
03/01/02
(c)
DS21474B-page 26
2002 Microchip Technology Inc.
*B47412SD*

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