TC818A Auto-Ranging Analog-to-Digital Converter with 3-1/2 Digit Display Features General Description • Auto-Ranging Analog-to-Digital Converter with 3-1/2 Digit Display • Annunciator Outputs Permit Customizing of LCD • 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 Range Mode: 1/3000 • Internal AC-to-DC Conversion Op Amp • Triplex LCD Drive for Decimal Points, Digits, • Bar Graphs, and Annunciators • Continuity Detection and Piezoelectric Transducer Driver • Low Drift Internal Reference: 75ppm/°C • 9V Battery Operation: 10mW • Low Battery Detection and LCD Annunciator The TC818A is an integrating analog-to-digital converter (ADC) with a 3-1/2 digit numeric LCD driver, automatic ranging, and single 9V battery operation. The numeric display provides 0.05% resolution and a full set of annunciators that spell out the TC818A's many operating modes. Device Selection Table Part Number Package Operating Temperature Range TC818ACBU 64-Pin PQFP 0°C to +70°C Automatic range selection is provided for both voltage (DC and AC) and ohms (high and low power) measurements. Expensive and bulky mechanical range switches are not required. Five full scale ranges are available, with automatic selection of external volt/ohm attenuators over a 1 to 10,000 range. Two current ranges, 20mA and 200mA, can be manually selected. The auto-range feature can be bypassed, allowing input attenuator selection through a single line input. During Manual mode operation, resolution is extended to 3000 counts full scale. Extended resolution is also available during 2000kΩ and 2000V full scale autorange operation. The extended range operation is indicated by a flashing 1 MSD and by the fully extended bar graph. The TC818A includes an AC-to-DC converter for AC voltage and current measurements. Only external diodes/resistors/capacitors are required. Other features include a Memory mode, low battery detection, display HOLD input, and continuity buzzer driver. The 3-1/2 digit numeric display includes a full set of annunciators. Decimal points are adjusted as automatic or manual range changes occur, and Voltage, Current, and Ohms Operating modes are displayed. Additional annunciators are activated for manual, auto, memory, HOLD, AC, low power ohms, and low battery conditions. The TC818A is available in a surface mounted 64-pin flat package. Combining a numeric display driver, single 9V battery operation, internal range switching, and compact surface mounting, the TC818A is ideal for advanced portable instruments. 2002 Microchip Technology Inc. DS21475B-page 1 TC818A Package Type ACVH RVIBUF RΩBUF 57 56 55 54 RX VSS 58 CAZ DGND 59 CFI RANGE 61 60 62 ADO HOLD 63 ADI -MEM 64 I DC(Ω)/ AC(LOΩ) NC 64-Pin PQFP 53 52 51 50 49 NC 1 48 NC OHM 2 47 CI 20mA 3 46 ACVL BUZ 4 45 II XTAL1 5 44 VI XTAL2 6 VDISP 7 BP1 8 BP2 9 43 VR4 LCD Backplanes 42 VR5 TC818A 41 VR2 40 VR3 BP3 10 39 ΩR5 LCD Segment Drives LOΩ/A 11 38 ΩR4 Ω/V 12 k/m/ HOLD 13 37 ΩR3 BCP0 14 35 ΩR1 AGD0 15 34 REFHI 36 ΩR2 FE0 16 24 25 26 27 FE1 BCP2 AGD2 FE2 BCP3 AC/-/AUTO -MEM/BATT ANNUNC 28 29 30 31 32 CREFL 23 DEINT 22 RMREFL 21 COM 20 VCC 19 BCP1 NC DS21475B-page 2 18 AGD1 33 CREFH 17 2002 Microchip Technology Inc. 2002 Microchip Technology Inc. 0.1 µF R8/220Ω (PTC) R15 9Ω 200mA R16 1Ω 20mA D3 D4 45 R1/163.85Ω 35 6.2V II COM R9/1kΩ R10/10kΩ ADO 42 D1 D2 C5/1µF – + R24/10kΩ R23/10kΩ C4/1µF + – R22/470kΩ 53 R21/2.2MΩ R26/3kΩ R27/2kΩ 56 ACVH C2/0.22µF 52 ADI Voltage Range Attenuator VR5 (÷10,000) VR4 (÷1,000) 4.7µF 43 Ohms Range Attenuator SYNC Backplane Drivers *Not required when Resistor Network is used. (See Applications Section for details.) ΩR1 (÷1) ΩR2 (÷10) ΩR3 (÷100) ΩR4 (÷1,000) ΩR5 (÷10,000) RMREFL – + C1/1µF TC818A RΩBUF 220 kΩ 54 CAZ 0.1µF 49 CAZ RVIBUF 150 kΩ 55 ACVL RΩBUF RVIBUF 46 1's HOLD CINT 47 CI 60 HOLD 32 C6 0.01µF R20 100kΩ 51 CFI BUZ -MEM RANGE DC/AC or Ω/LOΩ I OHM 200mA DGND VSS VCC XTAL2 30 5 DEINT XTAL1 33 CREF 29 4 61 59 62 63 2 3 58 57 28 6 V V Audio Transducer 200mA 20mA Ω 200mA 20mA Ω R18/24kΩ VCC Enable 9V 32.768kHz (~ 33kHz) 39pF 163.85mV R19/5kΩ 34 CREFL CREFH COM REFHI 16 15 14 FE0 AGD0 BCP0 kΩ mVA LO W Segment and Decimal Point Drive 10's 20 19 18 FE1 AGD1 BCP1 HOLD 22 21 13 25 26 24 23 k/m/ AC/–/ –MEM/ BCP3 FE2 AGD2 BCP2 HOLD AUTO BATT 100's Display 1000's Annunciators AUTO 11 12 7 8 9 10 27 50 RX VDISP Ω/V ANNUNC LOΩ/A BP1 BP2 BP3 R13* 500kΩ Voltage R14/9.9MΩ 44 VR1 (÷1) Input R12/1.111MΩ 41 VR2 (÷10) R11/101kΩ 40 VR3 (÷100) Current Input R2/1638.5Ω 36 R3/16.385kΩ 37 163.85kΩ 38 1.6385MΩ 39 R6/100kΩ 31 R7/100kΩ Z1 Positive Temperature Coefficient Resistor Resistance Input 0.1µF LCD Bias AC -MEM TC818A Typical Application DS21475B-page 3 TC818A 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 ....................................................... 15V Analog Input Voltage ..................................VCC to V SS Reference Input Voltage..............................VCC to V SS Voltage at Pin 43 ................................. Common ±0.7V Power Dissipation ............................................800mW Operating Temperature Range................ 0°C to +70°C Storage Temperature Range .............. -65°C to +150°C TC818A ELECTRICAL SPECIFICATIONS Electrical Characteristics: VA = 9V, TA = +25°C, unless otherwise specified. Symbol Parameter Zero Input Reading RE Rollover Error Min Typ Max Unit -0000 0000 +0000 Digital Reading 200mV Range without 10MΩ Resistor -0001 — +0001 Digital Reading 200mV Range with 10MΩ Resistor -0000 0000 +0000 Digital Reading 20mA and 200mA Range — — ±1 Counts — — ±3 200mV Range with 10MΩ Resistor — — ±1 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 — % Test Conditions 200mV Range without 10MΩ Resistor Best Case Straight Line BW = 0.1 to 10Hz 40 to 500Hz — ±5 — % Open Circuit Voltage for Ohm Measurements — 570 660 mV Excludes 200Ω Range Open Circuit Voltage for LO Ohm Measurements — 285 350 mV Excludes 200Ω Range VCOM Analog Common Voltage 2.8 3 3.3 V VCTC Common Voltage Temperature Coefficient — — 50 ppm/°C Display Multiplex Rate — 100 — Hz Low Logic Input — — 1 µA 20mA, AC, I, LOW Ω, HOLD Range, -MEM, OHMs (Relative to DGND, Pin 58) Logic 1 Pull-up Current — 25 — V 20mA, AC, I, LOW Ω, HOLD Range, -MEM, OHMs (Relative to DGND, Pin 58) VOL Low Logic Output — DGND +0.1 — V ANNUNC, DEINT: IL = 100µA VOH High Logic Output — VCC - 0.1 — V ANNUNC, DEINT: IL = 100µA kHz VIL Buzzer Drive Frequency — 4 — Low Battery Flag Voltage 6.3 6.6 7 V Operating Supply Current — 0.8 1.5 mA DS21475B-page 4 Error 40 to 2000Hz (VCC - VCOM) VCC to VSSA 2002 Microchip Technology Inc. TC818A 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 PQFP) Symbol 1 NC Description No connection. 2 OHM Logic Input. “0” (Digital Ground) for resistance measurement. 3 20mA Logic Input. “0” (Digital Ground) for 20mA full scale current 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 9 BP2 LCD Backplane #2. 10 BP3 LCD Backplane #3. 11 LOΩ/A Buzzer. Audio frequency, 4kHz, output for continuity indication during resistance measurement. A noncontinuous 4kHz signal is output to indicate an input over range during voltage or current measurements. LCD Backplane #1. LCD Annunciator segment drive for low ohms resistance measurement and current measurement. 12 Ω/V LCD Annunciator segment drive for resistance measurement and voltage measurement. 13 k/m/HOLD LCD Annunciator segment drive for k (“kilo-Ohms”), m (“milliamps” and “millivolts”) and HOLD mode. 14 BCP0 LCD segment drive for “b,” “c” segments and decimal point of least significant digit (LSD). (One’s digit) 15 AGD0 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 19 AGD1 LCD segment drive for “a,” “g,” “d” segments of 2nd LSD. 20 FE1 LCD segment drive for “f” and “e” segments of 2nd LSD. 21 BCP2 22 AGD2 23 FE2 24 BCP3 25 AC/-/AUTO 26 -MEM/BATT LCD annunciator segment drive for AC for low battery indication and memory (relative measurement). 27 ANNUNC LCD segment drive for “b,” “c” segments and decimal point 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 “f,” “e” segments of 3rd LSD. LCD segment drive for “b,” “c” segments and decimal point of MSD, (thousand’s digit). LCD annunciator segment drive for AC measurements, polarity, and auto-range operation. Square wave output at the backplane frequency, synchronized to BP1. ANNUNC can be used to control display annunciators. Connecting an LCD segment to ANNUNC turns it on; connecting it to its backplane turns it off. 28 VCC Positive battery supply connection. 29 COM Analog circuit ground reference point. Nominally 3V below VCC. 30 DEINT 31 RMREFL De-integrate output. 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 35 ΩR1 Standard resistor connection for 200Ω full scale. 36 ΩR2 Standard resistor connection for 2000Ω full scale. 2002 Microchip Technology Inc. Reference voltage for voltage and current measurement. Nominally 163.85mV. DS21475B-page 5 TC818A TABLE 2-1: Pin Number (64-Pin PQFP) PIN FUNCTION TABLE (CONTINUED) Symbol Description 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. 40 VR3 Voltage measurement ÷ 100 attenuator. 41 VR2 Voltage measurement ÷ 10 attenuator. 42 VR5 Voltage measurement ÷ 10,000 attenuator. 43 VR4 44 VI Unknown voltage input ÷ attenuator. 45 II Unknown current input. 46 ACVL 47 CI Voltage measurement ÷ 1000 attenuator. Low output of AC-to-DC converter. Integrator capacitor connection. Nominally 0.1µF. (Must have low dielectric absorption. Polypropylene dielectric 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 ADI Negative input of internal AC-to-DC operational amplifier. 53 ADO 54 RΩBUF Active buffer output for resistance measurement. Integration resistor connection. Nominally 220kΩ. 55 RVIBUF Active buffer output for voltage and current measurement. Integration resistor connection. Nominally 15kΩ. 56 ACVH 57 VSS 58 DGND 59 RANGE 60 HOLD Input to hold display. Connect to DGND to "FREEZE" display. 61 -MEM Input to enter Memory Measurement mode for relative measurements. The two LSDs are stored and subtracted from future measurements. 62 DC(Ω)/ AC(LOΩ) Input that selects AC or DC option during voltage/current measurements. For resistance measurements, the ohms or low power (voltage) ohms option can be selected. 63 I 64 NC Output of internal AC-to-DC operational amplifier. Positive output of AC-to-DC converter. Negative supply connection. Connect to negative terminal of 9V battery. Internal logic digital ground. Ground connection for the logic "0" level. Nominally 4.7V below VCC . Input to set manual operation and change ranges. Input to select measurement. Connect to logic "0" (digital ground) for current measurement. No connection. 3.0 DETAILED DESCRIPTION 3.1 Analog-to-Digital Converter (ADC) The TC818A includes an integrating ADC with autoranging resolution of 2000 counts and manual range resolution of 3000 counts. Figure 3-1 shows a simplified schematic of the analog section. In Auto-Ranging mode, internal logic will adjust the input voltage or ohms attenuators so that measurements will always be made in the appropriate range. DS21475B-page 6 Measurement ranges, logic control inputs, 3-1/2 digit LCD formatting, and other features are identical to the TC818A auto-ranging A/D converter. However, the TC818A is not pin compatible with, and is not a replacement for, the TC818A. A display annunciator output (ANNUNC) can be used to customize the LCD. ANNUNC is a square wave at the backplane frequency. Connecting an annunciator segment to the ANNUNC driver turns the segment on; connecting the segment to its backplane turns it off. 2002 Microchip Technology Inc. TC818A FIGURE 3-1: TC818A ANALOG SECTION 0.1µF Ω RX 50 S12 V • 1/1 R6/100kΩ RMREFL 31 S21 DE • Ω R7/100 kΩ Ohms Input R8/220 Ω (PTC) R5/1.638MΩ 0.1µF Ω R5 39 TC818A 10k Ω Ω• S25 1/1k R4/163.85kΩ ΩR4 38 R3/16385Ω ΩR3 37 Z1 R2/1638.5Ω ΩR2 36 Ω• S26 1/100 Ω• S27 1/10 6.2V R1/163.85Ω ΩR1 35 S28 Ω • 1/1 S44 Ω • HI Ω 1.5Ω S43 VCC + Ω • LOΩ –2.8V REF AMP 1.5 kΩ + Current Input S33 S32 S31 S30 S29 Ω • Ω • Ω • Ω • Ω• 1/1 1/10 1/1001/1k 1/10k VCC W+1 S10 R15/9Ω II 45 200mA R16/1Ω 34 REFHI ≈163.85mV S22 DE • Ω VI 44 S1 *Not Required when Resistor Network is Used R12/1.11M Ω VR2 41 Common S2 V•1/100 R10/10kΩ VR4 43 S4 V•1/1k R9/1kΩ S5 V•1/10k VR5 42 53 R22 470 kΩ + AC-to-DC Converter Op Amp ADO 33 CREFH V•1/10 S3 D2 R23 10kΩ V•1/1 R11/101kΩ VR3 40 4.7µF S22 DE • Ω V• V• V• V• 1/10 1/100 1/1 1/10k k S6 S7 S8 S9 R13/500kΩ* S20 DE CREFH 0.1µF 32 CREFL S18 DE S19 DE+ Ω + Ω+AC S11 – S16 DE+ S17 DE51 CFI R21 2.2 MΩ C4 1µF C2 ADI R20/100kΩ 0.01µF C6 52 0.22µF ACVH 56 R26 3kΩ R19/5k Ω 29 D3 D4 Voltage Input R14/9.9 MΩ R24 C3 10kΩ +1µF R18/24k Ω Analog Cmmon – 20mA D1 VCC VCC S24Ω • 1/10k C1/1µF R27/2kΩ ACVH 46 INT•( Ω + DC) S13 S14 INT• Ω •ACΩ S40 + Buffer S38 AZ – S15 AZ – INT•Ω•ACΩ S39 INT+ Ω + DC S35 Ω S37 Ω Ω S34Ω 54 RΩBUF – + + Comparator To Digital Section Integrator 49 55 RΩ RVI C BUF BUF AZ 220 0.01µF k Ω 150 C AZ Ω k 47 INT 0.01µF CINT RΩBUF 2002 Microchip Technology Inc. DS21475B-page 7 TC818A 3.2 Resistance, Voltage, Current Measurement Selection The TC818A is designed to measure voltage, current, and resistance. Auto-ranging is available for resistance and voltage measurements. The OHM (Pin 2) and I (Pin 63) input controls are normally pulled internally to VCC. By tying these pins to DGND (Pin 58), the TC818A is configured internally to measure resistance, voltage, or current. The required signal combinations are shown in Table 3-1. TABLE 3-1: TC818A MEASUREMENT SELECTION LOGIC Function Select Pin 0 = Digital Ground 1 = Floating or Tied to VCC TABLE 3-2: Full-Scale Range Selected Measurement OHM (Pin 2) I (Pin 63) 0 0 Voltage 0 1 Resistance 1 0 Current 1 1 Voltage Resistance Measurements (Ohms and Low Power Ohms) The TC818A can be configured to reliably measure incircuit resistances shunted by semiconductor junctions. The TC818A 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/LOΩ (Pin 62) input selects the Low Power Ohms Measurement mode. For low power ohms measurements, Ω/LOΩ (Pin 62) is momentarily brought LOW to digital ground potential. The TC818A 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, LOΩ, will be activated. On power-up, the Low Power Ohms mode is not active. If the Manual Operating mode has been selected, toggling Ω/LOΩ resets the TC818A back to the AutoRange mode. In Manual mode, the decision to make a normal or low power ohms measurement should be made before selecting the desired range. OHMS RANGE LADDER NETWORK Standard Resistance Low Power Ohms Mode 200Ω 163.85Ω (R1) NO 2000Ω 1638.5kΩ (R2) YES 20kΩ 16,385Ω(R3) YES 200kΩ 163,85Ω (R4) YES 1,638,500Ω (R5) YES 2,000kΩ 3.4 Note 1: OHM and I are normally pulled internally high to VCC (Pin 28). This is considered a logic “1”. 2: Logic “0” is the potential at digital ground (Pin 58). 3.3 R8, a positive temperature coefficient resistor, and the 6.2V zener, Z1, provide input voltage protection during ohms measurements. Ratiometric Resistance Measurements The TC818A 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 “incircuit” 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 3-2 shows a detailed block diagram of the TC818A, 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 3-3 shows that the conversion accuracy relies on the accuracy of the external standard resistors. 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: Full Scale Range REFERENCE RESISTORS Reference Resistor Ω/Count 200k 163.85 0.1 2k 1638.5 1 20k 16385 10 200k 163,850 100 2M 1,638,500 1000 The low power ohms measurement is not available on the 200Ω full scale range. Open circuit voltage on this range is below 2.8V. The standard resistance values are listed in Table 3-2. DS21475B-page 8 2002 Microchip Technology Inc. TC818A FIGURE 3-2: RATIOMETRIC RESISTANCE MEASUREMENT FUNCTIONAL DIAGRAM 9V VSS R5/1638500 Ω 39 S29 38 S30 37 S31 R2/1638.5Ω 36 S32 Low Ohms S33 Ω • LO VCC R4/163850Ω R3/16385 Ω ÷10k ÷1k ÷100 ÷10 ÷1 R1/163.85Ω 35 ÷10k ÷1k R8 220Ω (PTC) DE • Ω S23 33 S20 VCC 28 Ω • HIΩ VA ~1.5kΩ ÷100 ÷10 ÷1 S24 S25 S26 S27 S28 57 10kΩ Ohms R18 24kΩ REFHI 34 ~1.5kΩ Voltage Reference + DE + Ω – Analog Common VCC -2.6V CREF 0.1µF 32 S18 DE 31 S21 DE • Ω R6/100kΩ R7/100kΩ RX TC818A Buffer DE 50 Unknown S13 S12 V• INT • ( Ω + DC) 1 1 S37 S36 Ω S34 Ω Ω S35 Ω Integrator 49 RΩBUF 54 55 RVIBUF 150kΩ 220kΩ FIGURE 3-3: 5kΩ 29 ≈ VCC -2.8V DE S19 + Comparator 47 CAZ 0.1µF CINT 0.1µF RESISTANCE MEASUREMENT ACCURACY SET BY EXTERNAL STANDARD RESISTOR Example: 200kΩ Full Scale Measurement VA = RS 163.85kΩ 0.64V for Ohms 0.32V for LO Ohms CREF 100kΩ + VR 163.85kΩ (a ) VR = ------------------------------------------------ x0.64 163.85 + 220 + R X (b) VX = RX ------------------------------------------------------------- x0.64 163.85kΩ + 220Ω + R X (c) “Ramp Up Voltage” = “Ramp Down Voltage” . VX VX = ----------------T . . ----------------xT ( RICI) I ( R I C I ) DE 220Ω VX Unknown RX To Analog Buffer Where: RI = Integrating Resistor, TI = Integrate Time CI = Integrating Capacitor, TDE = De-integrate Time (TDE) (d) RX = 163.85 TI Independent of RI, CI or Internal Voltage Reference 2002 Microchip Technology Inc. DS21475B-page 9 TC818A 3.5 Voltage Measurement Resistive dividers are automatically changed to provide in range readings for 200mV to 2000V full scale readings (Figure 3-1). The input resistance is set by external resistors R14/R13. The divider leg resistors are R9R12. 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 10mΩ input impedance, the divider network impedances may be lowered. This will reduce voltage offset errors induced by switch leakage currents. 3.6 Current Measurement The TC818A 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 current input (II input, Pin 45). For 20mA measurements, a 10Ω resistor is used. The 200mA range requires a 1Ω resistor; full scale is 200mV. Printed circuit board trace resistance between analog common and R16 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 common (COM, Pin 29) and system common must be minimized. 3.7 The minimum AC full scale voltage range is 2V. The DC full scale minimum voltage is 200mV. AC current measurements are available on the 20mA and 200mA full scale current ranges. 3.8 Conversion Timing The TC818A analog-to-digital converter uses the conventional dual slope integrating conversion technique, with an added phase that automatically eliminates zero offset errors. The TC818A gives a zero reading with a 0 volt input. The TC818A is designed to operate with a low cost, readily available 32.768kHz crystal. It serves as a timebase 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 de-integrate — 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 (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 3-4 shows the basic TC818A timing relationships. AC-to-DC Measurements In voltage and current measurements, the TC818A 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 TC818A enters the DC Measurement mode. For AC measurements (current or voltage), AC/DC (Pin 62) is momentarily brought LOW to digital ground potential; the TC818A sets up for AC measurements, and the AC liquid crystal display annunciator activates. Toggling AC/DC LOW again returns the TC818A to DC operation. If the Manual Operating mode has been selected, toggling AC/DC resets the TC818A back to the AutoRange mode. In Manual mode operation, AC or DC should be selected first, then the desired range. DS21475B-page 10 2002 Microchip Technology Inc. TC818A FIGURE 3-4: BASIC TC818A CONVERSION TIMING TC818A Signal INT Phase Auto-Zero Phase REF DEINT Phase Next Conversion Auto-Zero Cycle Extended Resolution Zero Crossing External Crystal = 32.768kHz Internal Clock Period = tP = 2/32.768 = 61.04µsec Total Conversion Time = tCONV = 8000(tP) = 488.3msec ≈ 2 conv/sec Integration Time = TI = 1638.5(tP) = 100msec Min. Auto-Zero Time Fixed 1638.5tP *Max. 3000tP 3361.5tP tI tDE µ To Input Signal tCONV = 8000tP *In Auto-Range Operation, Maximum is 2000tP and minimum Auto-Zero Time is 4361.5tP 3.9 Manual Range Selection The TC818A 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 TC818A power-up circuit initially selects autorange operation. Once the manual range option is entered, range changes are made by momentarily grounding the RANGE control input. The TC818A remains in the Manual Range mode until the measurement function (voltage or resistance), or measurement option (AC/DC, Ω/LOΩ) changes. This causes the TC818A to return to auto-ranging operation. The “Auto” LCD annunciator driver is active only in the Auto-Range mode. Figure 3-5 shows typical operation where the manual range selection option is used. Also shown is the extended resolution display format. Also, see Figure 3-6 and Figure 3-7. Maximum Reference De-integrate Time = tDE 3000(tP) = 183.1msec (manual extended resolution) = 2000(tP) = 122.1msec (auto-range) Maximum Auto-Zero Time = (8000 - 3000 - 1638.5) (tP) = 205.1msec (manual extended resolution) = (8000 - 3000 - 1638.5) (tP) = 205.1msec (manual extended resolution) FIGURE 3-5: 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 ? Over Range Indicator Yes "1" = > Flashing MSD No Is RX > 2000 ? No Display "1" 000 Yes* Display Last 3 Digits and Flash MSD Extended Resolution Feature Display True Reading *Mode also operates when Auto-Ranging Operator is selected and 2MΩ < RX < 2.999MΩ. 2002 Microchip Technology Inc. DS21475B-page 11 TC818A FIGURE 3-6: MANUAL RANGE SELECTION CURRENT MEASUREMENTS FIGURE 3-7: MANUAL RANGE SELECTION VOLTAGE MEASUREMENTS Range Select Range Select Noncontinuous Noncontinuous Yes Output 4kHz Audio Frequency Output 4kHz Audio Frequency Over Range Indicator Over Range Indicator Is IX > 3000 ? Yes "1" = > Flashing MSD No Is IX > 2000 ? 3.10 Display "1" 000 Yes Display Last 3 Digits and Flash MSD Is VX > 3000 ? Yes "1" = > Flashing MSD No Is VX > 2000 ? No No Display True Reading Display True Reading Display "1" 000 Yes Display Last 3 Digits and Flash MSD Extended Resolution Feature Extended Resolution Manual Operation When operated in the Manual Range mode, the TC818A extends resolution by 50% for current, voltage, and resistance measurements. Resolution increases to 3000 counts from 2000 counts. The extended resolution feature operates only in 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. The bar graph LCD will be fully extended. An input over range condition causes the most significant digit (MSD) to blink and sets the three least significant digits (LSDs) 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 operations. For resistance measurements, the buzzer signal does not indicate an over range condition. The buzzer is used to indicate continuity. Continuity is defined as a resistance reading less than 19 counts. DS21475B-page 12 2002 Microchip Technology Inc. TC818A 3.11 -MEM Operating Mode Bringing -MEM (Pin 61) momentarily LOW configures the TC818A “-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 3-1: RI (N) MEM IN AUTO-RANGING = 18.21kΩ (20kΩ Range) = ≥ Display 18.21kΩ = ≥ 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 3-2: RI (N) MEM IN FIXED RANGE (200 FULL SCALE) = 18.21kΩ = ≥ Display 18.2kΩ = ≥ Store 8.2Ω RI (N+1) = 36.7Ω = ≥ Display 36.7 - 8.2 = 28.5Ω RI (N+2) = 5.8Ω = ≥ Display 5.8-8.2 = -2.4Ω* *Will display minus resistance if following input is less than offset stored at fixed range. EXAMPLE 3-3: VI (N) MEM IN FIXED RANGE 20V FULL SCALE = 0.51V = ≥ Display 0.51V = ≥ 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 “-MEM” mode is not active. Once the “-MEM” is entered, bringing MEM LOW again returns the TC818A 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. 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. 2002 Microchip Technology Inc. The “-MEM” Operating mode can be very useful in resistance measurements when lead length resistance would cause measurement errors. 3.12 Automatic Range Selection Operation When power is first applied, the TC818A enters the auto-range 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 (AC/DC, Ω/LOΩ). The automatic voltage range selection begins on the most sensitive scale first: 200mV for DC or 2V for AC measurements. The voltage range selection flow chart is shown in Figure 3-8. Internal input protection diodes to VCC (Pin 28) and VSS (Pin 57) clamp the input voltage. The external 10MΩ input resistance (see R14 and R13 of Functional diagram) limits current safely in an over range 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 for 122msec, off for 122msec, on for 122msec and off for 610msec (see Figure 3-14). 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 3-9. The 200Ω range is the first range selected, unless the 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 MSD with the three LSDs 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. DS21475B-page 13 TC818A FIGURE 3-8: AUTO-RANGE OPERATION: VOLTAGE MEASUREMENT N = 0 If DC N = 1 If AC FIGURE 3-9: N = 0; 200mV Full Scale Range N = 1; 2V Full Scale Range AUTO-RANGE OPERATION: RESISTANCE MEASUREMENT N = 0 If Ω N = 1 If LOΩ N = 0; 200Ω Full Scale Range N = 1; 2kΩ Full Scale Range N = NK (Remain in Range Selected during the Kth Conversion) Kth Conversion VX = (1/10N) VIN (Remain in Range Selected during the Kth Conversion) Kth Conversion RX = 1 RIN 10N N = N –1 Continuity Indicator VX < 180 ? Activate Buzzer Yes N = 0 If DC N = 1 If AC ? No Yes RX < 19 ? Continuous 4kHz Signal N = N –1 No Yes RX < 180 No Yes ? VX > 2000 ? No Display Voltage (V)X No Yes N = N +1 No Extended Resolution No Display "1" XXX Flash MSD Activate Buzzer No N = N +1 N=4 ? Yes RX > 3000 ? Yes Display "1" 000 Flash MSD K = K +1 Yes Yes Yes Display Resistance ? N=4 ? VX > 3000 ? Yes RX > 2000 K = K +1 N = 0 If Ω N = 1 If LOΩ ? Over Range No Display "1" XXX Flash MSD Display "1" 000 Flash MSD Extended Resolution Over Range Start: Power-on, Function or Measurement Option Change Start: Power-on, Function or Measurement Option Change DS21475B-page 14 2002 Microchip Technology Inc. TC818A 3.13 Low Battery Detection Circuit The TC818A contains a low battery detector. When the 9V battery supply has been depleted to a 7V nominal value, the LCD low battery annunciator is activated. The low battery detector is shown in Figure 3-10. 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 3-10: LOW BATTERY DETECTOR The TC818A internally generates two intermediate LCD drive potentials (VH and VL) from a resistive divider (Figure 3-11) between VCC and VDISP. The latter 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 3-12 shows a typical drive signal and the resulting waveforms for “ON” and “OFF” RMS voltage levels across a selected LCD element. FIGURE 3-11: VCC Low Battery Detector 1/3 BIAS LCD DRIVE VCC TC818A R1 VT Comparator + To LCD Annunciator Selection Logic R3 – 50k R2 VZ ≈ 6.2V VSS R2 = 6.2V VT = 73 R1 + R 2 To Triplex Segment Drive Logic VH 50k VL 50k Low Battery Annunciator Displayed for VS < 7V. 3.14 TC818A Triplex Liquid Crystal Display (LCD) Drive VCC - VDISP For example, if V DISP 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 0.63V P signal across it or 1.92V for V CC -V DISP = 3V. Since the VDISP pin is available, the user may adjust the “ON” and “OFF” LCD levels for various manufacturers’ displays, by changing V P signal across it, or 1.92V for V DISP = 3V. VDISP VP = VCC - VDISP "OFF" = VP/3 RMS "ON" = 11 VP RMS 3 3 The TC818A directly drives a triplexed liquid crystal display (LCD) using 1/3 bias drive. All numeric data, decimal point, polarity and function annunciator drive signals are developed by the TC818A. 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: See VDSIP For Proper VP with Resistive Divider 3.15 Liquid Crystal Displays (LCDs) Most users will design their own custom LCD. However, for prototyping purposes, a standard display is available from Varitronix, Ltd. This prototype display configuration is shown in Figure 3-13 and Table 3-4. Varitronix Ltd. 9/F Liven House, 61-63, King Yip Street Kwun Tong, Hong Kong Tel: (852)3-410286 Fax: (852)34-39555 Part No.: VIM-328-DP USA Office: VL Electronics, Inc. 3171 LOs Feliz Blvd, #303 Los Angeles, CA 90039 Tel: (213) 738-8700 “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. 2002 Microchip Technology Inc. DS21475B-page 15 TC818A FIGURE 3-12: TRIPLEX LCD DRIVE WAVEFORMS TC818A Segments Backplanes Segments 1 2 3 4 5 6 VP VH a (FE – BP1) "ON" VP (3V) BP1 VP VH b (BCP – BP1) "ON" VL BP2 0 VP VH VL BP3 c (BCP – BP2) "ON" 0 Waveforms to Generate d (AGD – BP3) "ON" e (FE – BP2) "OFF" a BP1 BP2 e c d BP3 FE AGD DS21475B-page 16 BCP f (FE – BP1) "OFF" BACKP g LANES b f 1 g (AGD – BP2) "ON" 0 -VL -VH -VP VP VH VL 0 -VL -VH -VP VP VH VL 0 -VL -VH -VP VP VH VL 0 -VL -VP VP VH VL 0 -VL -VP VP VH VL -VL -VP VP VH VL 0 -VL -VH -VP 2 3 4 5 6 Applied RMS Voltage VRMS = 11 V P 3 3 VRMS = 11 V P 3 3 VRMS = 11 V P 3 3 VRMS = 11 V P 3 3 VRMS = VP 3 VRMS = VP 3 VRMS = 11 V P 3 3 2002 Microchip Technology Inc. TC818A 3.16 FIGURE 3-13: External Crystal The TC818A 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 488.3msec ( ≈ 2 conversions/ second). Integration time is 1638.5 clock periods or 100msec. TYPICAL LCD CONFIGURATION, TC818A TRIPLEX –+ -MEM The 32kHz quartz crystal is readily available and inexpensive. The 32kHz crystal is commonly used in digital clocks and counters. LO W HOLD AC kΩ mVA AUTO 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. TABLE 3-4: TYPICAL LCD CONFIGURATION PAD BP1 BP2 BP3 PAD BP1 BP2 BP3 1 — — SCALE 19 — — BP3 2 X0 X1 X2 20 — BP2 — 3 X5 X4 X3 21 BP1 — — 4 X6 X7 X8 22 — LOW A 5 X11 X10 X9 23 — W V 6 X12 X13 X14 24 HOLD k m 7 X17 X16 X15 25 4B 4C — 8 X18 X19 X20 26 4A 4G 4D 9 X23 X22 X21 27 4F 4E — 10 X24 X25 X26 28 3B 3C 3P 11 X29 X28 X27 29 3A 3G 3D 12 X30 X31 X32 30 3F 3E — 13 X35 X34 X33 31 2B 2C 2P 14 X36 X37 X38 32 2A 2G 2D 15 — X40 X39 33 2A 2G 2D 16 BPI — — 34 1B 1G 1P 17 — BP2 — 35 Z -MEM — 18 — — BP3 36 AC y AUTO 2002 Microchip Technology Inc. DS21475B-page 17 TC818A 3.17 Figure 3-14. The BUZ 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. “Buzzer” Drive Signal The BUZ output (Pin 4) will drive a piezo electric audio transducer. The signal is activated to indicate an input over range condition for current and voltage measurements, or continuity during resistance measurements. The BUZ signal swings from V CC (Pin 28) to DGND (Pin 58). The signal is at V CC when not active. 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 15ms 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), also activates the buzzer output for 15msec. A range change during a current measurement will not activate the buzzer output. A voltage or current input measurement over range is indicated by a noncontinuous 4kHz signal at the BUZ output. The LCD most significant digit also flashes and the three least significant digits are set to display zero. The buzzer drive signal for over range is shown in FIGURE 3-14: TC818A TIMING WAVEFORM FOR BUZZER OUTPUT 122ms 122ms 122ms 610ms 122ms 122ms VCC Digital Ground 1 Conversion 4kHz Signal Noncontinuous Buzzer Signal Indicates Input Over Range Power-up VIN = 250mV 4000 Change Range 8000 12000 Change Range Change Range Change Input VIN = 3.2V 1000 Clock Pulses INT Integrate TSC818A Signals DEINT AZ 100ms 1638.5 CP 122ms 2000 CP 250CP 250CP Auto-Ranging BUZ (Pin 4) 200mV Range Over Range 2V Range In Range 4kHz 15ms One Cycle of Over Range Buzzer 4kHz Buzzer Activated due to Power-up DS21475B-page 18 2500CP 250CP 3000CP Manual Range 2V Range In Range 200mV Range Extended Range 15ms 15ms Due to Manual Due to Range Change Range Change 2V Range In Range 4kHz 2V Range Out of Range 4kHz 610ms 122ms Buzzer Activated due to Previous Conversion Over Range Buzzer Activated due to Previous Conversion Over Range 2002 Microchip Technology Inc. TC818A 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 3.20.2 The TC818A provides a decimal point LCD drive signal. The decimal point position is a function of the selected full scale range, as shown in Table 3-5. DECIMAL POINT SELECTION RVIBUF SELECTION (PIN 55) In auto-range operation, the TC818A 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: 1*9 *9 *9 DP3 DP2 DP1 2000V, 2000kΩ OFF OFF OFF 200V, 200kΩ OFF OFF ON 20V, 20kΩ OFF ON OFF VINT = Integrator swing = ±2V 2V, 2kΩ ON OFF OFF tI = Integration time = 100msec 200V, 200Ω OFF OFF ON CI = Integration capacitor = 0.1µF 200mV, 200Ω OFF OFF ON 20mA OFF ON OFF 200mA OFF OFF ON Full Scale Range 3.19 Where: VMAX = Maximum input at VI = 300mV EQUATION 3-1: AC-to-DC Converter Operational Amplifier The TC818A 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: • • • • INTEGRATION RESISTOR SELECTION The TC818A automatically selects one of two external integration resistors. RVIBUF (Pin 55) is selected for voltage and current measurement. RΩBUF (Pin 54) is selected for resistance measurements. Display Decimal Point Selection TABLE 3-5: Component Selection 3.20.1 • Taiyo Yuden (USA) Inc. Arlington Center 714 West Algonquin Road Arlington Heights, Illinois 60005 Typical P/Ns: CB27BB, CB20BB, CB355BB 3.18 3.20 Slew Rate: 1V/µsec Unity Gain Bandwidth: 0.4MHz Open Loop Gain: 44dB Output Voltage Swing (Load = 10kΩ) ± 1.5V (Referenced to Analog Common) RVIBUF = 3.20.3 VMAX(T I) = 150kΩ VINT(CI) 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 3-15). When the AC measurement option is selected, the input buffer receives an input signal through switch S14, rather than switch S11 (see Figure 3-1). 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. 2002 Microchip Technology Inc. DS21475B-page 19 TC818A FIGURE 3-15: RΩ CALCULATION (200Ω MANUAL OPERATION) VCC = 9V SW33 RS ≈ 600Ω 3.21 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. 3.22 R1 163.85Ω R2 220Ω With an input voltage near full scale on the 200mV range, R19 is adjusted for the proper reading. 300Ω 3.23 Analog Common = VCC – 3V Where: VANCOM RS RI RX RS = = = = = Potential at Analog Common ≈ 2.7V 220Ω 163.85Ω 300Ω Internal switch 33 resistance ≈ 600Ω (V CC – VANCOM)RX (RX + RS + R 1 + R8) = 0.63V For a 3.1V integrator swing, the value of RΩBUF is easily calculated: Where: VINT TI CI R XMAX VXMAX = = = = = Integrator swing = 3.1V Integration time = 100msec Integration capacitor = 0.1µF 300Ω 700mV EQUATION 3-3: RΩBUF = VXMAX(TI) CI(VINT) = 200kΩ 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. DS21475B-page 20 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. 3.24 Flat Package Socket Sockets suitable for prototype work are available. A USA source is: EQUATION 3-2: RΩBUF = Reference Voltage Adjustment The TC818A 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 TC818A reference input voltage (REFHI, Pin 34) to approximately 163.85mV. VX R3 Capacitors - CINT, CAZ and C REF • 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 3.25 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 TABLE 3-6: RESISTIVE LADDER NETWORKS Attenuator Accuracy Attenuator Type Caddock Part Number 0.1% 0.25% 0.25% Voltage Voltage Resistance 1776-C441 1776-C44 T1794-204-1 2002 Microchip Technology Inc. TC818A 4.0 PACKAGING INFORMATION 4.1 Package Marking Information Package marking data not available at this time. 4.2 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. 4.3 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) 2002 Microchip Technology Inc. DS21475B-page 21 TC818A 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. DS21475B-page 22 2002 Microchip Technology Inc. TC818A 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. © 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 ® 8-bit MCUs, KEELOQ® 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. DS21475B-page 23 WORLDWIDE SALES AND SERVICE AMERICAS ASIA/PACIFIC Japan Corporate Office Australia 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: 480-792-7627 Web Address: http://www.microchip.com Microchip Technology Australia Pty Ltd Suite 22, 41 Rawson Street Epping 2121, NSW Australia Tel: 61-2-9868-6733 Fax: 61-2-9868-6755 Microchip Technology Japan K.K. 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B Far East International Plaza No. 317 Xian Xia Road Shanghai, 200051 Tel: 86-21-6275-5700 Fax: 86-21-6275-5060 China - Shenzhen 150 Motor Parkway, Suite 202 Hauppauge, NY 11788 Tel: 631-273-5305 Fax: 631-273-5335 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 San Jose Hong Kong Microchip Technology Inc. 2107 North First Street, Suite 590 San Jose, CA 95131 Tel: 408-436-7950 Fax: 408-436-7955 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 New York 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 Korea Microchip Technology Korea 168-1, Youngbo Bldg. 3 Floor Samsung-Dong, Kangnam-Ku Seoul, Korea 135-882 Tel: 82-2-554-7200 Fax: 82-2-558-5934 Singapore Microchip Technology Singapore Pte Ltd. 200 Middle Road #07-02 Prime Centre Singapore, 188980 Tel: 65-6334-8870 Fax: 65-6334-8850 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 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 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 Germany Microchip Technology GmbH Gustav-Heinemann Ring 125 D-81739 Munich, Germany Tel: 49-89-627-144 0 Fax: 49-89-627-144-44 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 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 *DS21475B* DS21475B-page 24 2002 Microchip Technology Inc.