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PDF TC815 Data sheet ( Hoja de datos )
| Número de pieza | TC815 | |
| Descripción | 3-1/2 Digit Auto-Ranging A/D Converter with Triplex LCD Drive and Display Hold Function | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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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
Device Selection Table
Part Number
TC815CBU
Package
64-Pin PQFP
Operating
Temperature Range
0°C to +70°C
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 volt-
age/ohm attenuators ranging from 1 to 1/10,000 are
automatically selected. Five full scale ranges are pro-
vided. The CMOS TC815 contains all the logic and
analog switches needed to manufacture an auto-
ranging instrument for ohms and voltage measure-
ments. User selected 20mA and 200mA current ranges
are available. Full scale range and decimal point LCD
annunciators are automatically set in auto-range oper-
ation. 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 opera-
tion is indicated by a flashing 1 MSD. The extended
resolution is also available during 200kΩ and 2000V
full scale auto-range operation.
The Memory mode subtracts a reading, up to ±5% of
full scale from subsequent measurements. Typical
applications involve probe resistance compensation for
resistance measurements, tolerance measurements,
and tare weight measurements.
The TC815 includes an AC to DC converter for
AC measurements. Only external diodes/resistors/
capacitors are required.
A complete LCD annunciator set describes the TC815
meter function and measurement range during ohms,
voltage and current operation. AC measurements are
indicated as well as auto-range operation. A low battery
detection circuit also sets the low battery display
annunciator. The triplex LCD display drive levels may
be set and temperature compensation applied via the
VDISP pin. With HOLD low, the display is not updated.
A HOLD mode LCD annunciator is activated.
The “low ohms” measurement option allows in-circuit
resistance measurements by preventing semiconduc-
tor junctions from being forward biased.
© 2002 Microchip Technology Inc.
DS21474B-page 1
1 page  
TC815
2.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1: PIN FUNCTION TABLE
Pin Number
(64-Pin Plastic)
Quad Flat Package
Symbol
Description
1 NC Logic Input. “0” (Digital Ground) for resistance measurement.
2
OHM
Logic Input. “0” (Digital Ground) for 20mA full scale current measurement.
3
20mA
Audio frequency, 4kHz, output for continuity indication during resistance measurement.
4
BUZ
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.
5 XTAL1 32.768kHz Crystal Connection.
6 XTAL2 32.768kHz Crystal Connection.
7
VDISP
Sets peak LCD drive signal: VP - VDD - VDISP. VDISP may also be used to compensate for
temperature variation of LCD crystal threshold voltage.
8 BP1 LCD Backplane #1.
9 BP2 LCD Backplane #2.
10 BP3 LCD Backplane #3.
11 LOΩ/A 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
ADG0
LCD segment drive for “a,” “g,” “d” segments of LSD.
16 FE0 LCD segment drive for “f” and “e” segments of LSD.
17 NC No connection.
18
BCP1
LCD segment drive for “b,” “c” segments and decimal point of 2nd LSD.
19
AGD1
LCD segment drive for “a,” “g,” “d” segments of 2nd LSD (Ten’s digit).
20 FE1 LCD segment drive for “f” and “e” segments of 2nd LSD.
21
BCP2
LCD segment drive for “b,” “c” segments and decimal point of 3rd LSD
(Hundred’s digit).
22
AGD2
LCD segment drive for “a,” “g,” “d” segments of 3rd LSD.
23 FE2 LCD segment drive for “b,” “c” segments and decimal point of 3rd LSD.
24
BCP3
LCD segment drive for “b,” “c” segments and decimal point of MSD
(Thousand’s digit).
25 AC/-/AUTO LCD annunciator drive signal for AC measurements, polarity, and auto-range operation.
26 -MEM/BATT LCD annunciator drive signal for low battery indication and Memory
(Relative Measurement) mode.
27
VSSD
Negative battery supply connection for internal digital circuits. Connect to negative terminal
of battery.
28 VCC Positive battery supply connection.
29 ANALOG Analog circuit ground reference point. Nominally 2.6V below VCC.
COM
30 RMREFH Ratiometric (Resistance measurement) reference high voltage.
31 RMREFL Ratiometric (Resistance measurement) reference low voltage.
32
CREFL
Reference capacitor negative terminal CREF 0.1µf.
33
CREFH
Reference capacitor positive terminal CREF 0.1µf.
34 REFHI Reference voltage for voltage and current measurement; nominally 163.85mV.
© 2002 Microchip Technology Inc.
DS21474B-page 5
5 Page 
4.0 CONVERSION TIMING
The TC815 analog-to-digital converter uses the con-
ventional 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 avail-
able; it serves as a time-base oscillator crystal in many
digital clocks. (See External Crystal Sources.)
The external clock is divided by two. The internal clock
frequency is 16.348kHz, giving a clock period of
61.04µsec. The total conversion — auto-zero phase,
signal integrate and reference deintegrate — requires
8000 clock periods or 488.3msec. There are approxi-
mately 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, represent-
ing a full scale analog input, is 3000 clock periods or
183.1msec during manual extended resolution opera-
tion. 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 auto-
zero phase. An auto-ranging, or manual conversion
takes 8000 clock periods. After a zero crossing is
detected in the Reference De-integrate mode, the auto-
zero phase is entered. Figure 4-1 shows the basic
TC815 timing relationships.
TC815
FIGURE 4-1:
TC815
Auto-Zero
Phase
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
TCONV 8000 TP
*Max
3000.0 TP
TDE
To Input
Signal
*In Auto-Range Operation
Maximum is 2000TP and
Minimum Auto-Zero time
i s 4361.5TP
External Crystal = 32.768kHz
Internal Clock Period = TP = 2/32.768 = 61.04µsec
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
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet TC815.PDF ] | |
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