TC7116(2002) View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
TC7116 Datasheet PDF : 22 Pages
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TC7116/A/TC7117/A
FIGURE 3-5:
TC7116/TC7116A DIGITAL SECTION
TC7116
TC7116A
Backplane
21
Typical Segment Output
V+
0.5mA
2mA
Segment
Output
LCD Phase Driver
7-Segment 7-Segment 7-Segment
Decode
Decode
Decode
÷200
Latch
Internal Digital Ground
Thousands
Hundreds
Tens
Units
To Switch Drivers
From Comparator Output
40
OSC1
Clock
39
OSC2
÷4
Logic Control
38 Internal Digital Ground
OSC3
1
HLDR
~70kΩ
VTH = 1V
35
V+
6.2V 37
TEST
500Ω
26 V-
3.2.1 SYSTEM TIMING
The clocking method used for the TC7116/TC7116A
and TC7117/TC7117A is shown in Figure 3-6. Three
clocking methods may be used:
1. An external oscillator connected to Pin 40.
2. A crystal between Pins 39 and 40.
3. An RC network using all three pins.
The oscillator frequency is ÷4 before it clocks the
decade counters. It is then further divided to form the
three convert cycle phases: Signal Integrate (1000
counts), Reference De-integrate (0 to 2000 counts),
and Auto-Zero (1000 to 3000 counts). For signals less
than full scale, auto-zero gets the unused portion of ref-
erence de-integrate. This makes a complete measure
cycle of 4000 (16,000 clock pulses), independent of
input voltage. For 3 readings per second, an oscillator
frequency of 48kHz would be used.
To achieve maximum rejection of 60Hz pickup, the sig-
nal integrate cycle should be a multiple of 60Hz. Oscil-
lator frequencies of 240kHz, 120kHz, 80kHz, 60kHz,
48kHz, 40kHz, etc. should be selected. For 50Hz rejec-
tion, oscillator frequencies of 200kHz, 100kHz,
66-2/3kHz, 50kHz, 40kHz, etc. would be suitable. Note
that 40kHz (2.5 readings per second) will reject both
50Hz and 60Hz.
3.2.2 HOLD READING INPUT
When HLDR is at a logic HIGH, the latch will not be
updated. Analog-to-digital conversions will continue,
but will not be updated until HLDR is returned to LOW.
To continuously update the display, connect to TEST
(TC7116/TC7116A) or GROUND (TC7117/TC7117A),
or disconnect. This input is CMOS compatible with
70kΩ typical resistance to TEST (TC7116/TC7116A) or
GROUND (TC7117/TC7117A).
DS21457B-page 10
© 2002 Microchip Technology Inc.
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