TC818ACBU View Datasheet(PDF) - Microchip Technology
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TC818ACBU Datasheet PDF : 24 Pages
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TC818A
FIGURE 3-4:
BASIC TC818A CONVERSION TIMING
TC818A
Auto-Zero
Phase
Signal
INT
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
Min. Auto-Zero
Time
3361.5tP
Fixed
1638.5tP
tI
*Max.
3000tP
tDE
tCONV = 8000tP
µTo
Input
Signal
*In Auto-Range Operation, Maximum
is 2000tP and minimum Auto-Zero Time is 4361.5tP
Integration Time = TI = 1638.5(tP) = 100msec
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)
3.9 Manual Range Selection
The TC818A voltage and resistance auto-ranging fea-
ture 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 Auto-
Ranging mode.
The TC818A power-up circuit initially selects auto-
range 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 measure-
ment 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.
FIGURE 3-5:
MANUAL RANGE
SELECTION RESISTANCE
MEASUREMENTS
Continuity
Indicator
Output 4kHz
Audio
Frequency
Continuous
4kHz Buzzer
Manual
Range
Select
Yes
Is
RX < 19
?
No
Over Range
Indicator
Is
Yes
RX > 3000
?
Display
"1" 000
No
"1" = > Flashing
MSD
Is
RX > 2000
?
No
Display
True
Reading
Yes*
Display Last
3 Digits and
Flash MSD
Extended Resolution
Feature
*Mode also operates when Auto-Ranging Operator is selected
and 2MΩ < RX < 2.999MΩ.
© 2002 Microchip Technology Inc.
DS21475B-page 11
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