参数资料
型号: TC820C/PL
元件分类: ADC
英文描述: 1-CH 3-BIT DUAL-SLOPE ADC, PARALLEL ACCESS, PDIP40
封装: 0.600 INCH, PLASTIC, DIP-40
文件页数: 3/34页
文件大小: 435K
代理商: TC820C/PL
2007 Microchip Technology Inc.
DS21476C-page 11
TC820
The peak reading function is also available when the
TC820 is in the Frequency Counter mode. The counter
auto-ranging feature is disabled when peak reading
hold is selected.
3.2.7
10:1 RANGE CHANGE
The analog input full scale range can be changed with
the RANGE/FREQ input. Normally, RANGE/FREQ is
held low by an internal pull-down. Connecting this pin
to VS+ will increase the full scale voltage by a factor of
10. No external component changes are required.
The RANGE/FREQ input operates by changing the
integrate period. When RANGE/FREQ is connected to
VDD, the signal integration phase of the conversion is
reduced by a factor of 10 (i.e., from 2000 counts to 200
counts).
For the TC820, the 10:1 range change will result in ±4V
full scale. This full scale range will exceed the Common
mode range of the input buffer when operating from a
9V battery. If range changing is required for the TC820,
a higher supply voltage can be provided, or the input
voltage can be divided by 2 externally.
3.3
Frequency Counter
In addition to serving as an analog-to-digital converter,
the TC820 internal counter can also function as a fre-
quency counter (Figure 3-3). In the Counter mode,
pulses at the RANGE/FREQ input will be counted and
displayed.
The frequency counter derives its time-base from the
clock oscillator. The counter time-base is:
EQUATION 3-5:
Thus, the counter will operate with a 1-second time-
base when a 40 kHz oscillator is used. The frequency
counter accuracy is determined by the oscillator
accuracy. For accurate frequency measurements, a
crystal oscillator is recommended.
The frequency counter will automatically select the
proper range. Auto-range operation extends over four
decades, from 3.999 kHz to 3.999 MHz. Decimal points
are set automatically in the Frequency mode (Figure 3-2).
The logic switching levels of the RANGE/FREQ input
are CMOS levels. For best counter operation, an
external buffer is recommended. See the applications
section for details.
3.4
Logic Probe
The TC820 can also function as a simple logic probe
(Figure 3-5). This mode is selected when the LOGIC
input is high. Two dual purpose pins, which normally
control the decimal points, are used as logic inputs.
Connecting either input to a logic high level will turn on
the corresponding LCD annunciator. When the "low"
annunciator is on, the buzzer will be on. As with the
frequency counter input, external level shifters/buffers
are recommended for the logic probe inputs.
FIGURE 3-3:
TC820 Counter Operation.
tCOUNT =
FOSC
40,000
Data Latch, Peak Hold
Register, LCD
Decoder/Drivers
Over Range
Detect
Under Range
Control
Auto-Range
Control
Programmable
Divider
( ÷1, 10, 100, 1000)
Clock
Oscillator
To Decimal
Point Drivers
Frequency Input
RANGE/
FREQ
÷20,000
From Integrator
of A/D Converter
Comparator
LCD
3-3/4 Digit Counter
Enable
Count
Overflow
A/D Converter
Frequency Counter
A/D Converter/Frequency
Counter Select
TC820
÷2
FREQ/
VOLTS
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