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參數(shù)資料
| 型號： | TC820CKW |
| 廠商： | Microchip Technology Inc. |
| 元件分類： | 通用總線功能 |
| 英文描述： | 3-3/4 Digit A/D Converter with Frequency Counter and Logic Probe |
| 中文描述： | 3-3/4位A / D轉(zhuǎn)換頻率計數(shù)器和邏輯轉(zhuǎn)換的探討 |
| 文件頁數(shù)： | 9/22頁 |
| 文件大小： | 275K |
| 代理商： | TC820CKW |
3-157
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
where: V
REF
= Reference voltage
= Integration time
t
DEINT
= Deintegration time
t
INT
For a constant t
INT
:
V
IN
= V
REF
3
0
t
DEINT
t
INT
Accuracy in a dual-slope converter is unrelated to the
integrating resistor and capacitor values as long as they are
stable during a measurement cycle. An inherent benefit of
the dual-slope technique is noise immunity. Noise spikes
are integrated or averaged to zero during the integration
periods, making integrating ADCs immune to the large
conversion errors that plague successive approximation
converters in high-noise environments. Interfering signals,
with frequency components at multiples of the averaging
(integrating) period, will be attenuated (Figure 3). Integrating
ADCs commonly operate with the signal integration period
set to a multiple of the 50/60Hz power line period.
Figure 3. Normal-Mode Rejection of Dual-Slope Converter
30
20
10
0
0.1/T
1/T
10/T
INPUT FREQUENCY
N
T = MEASUREMENT
PERIOD
Analog Section
In addition to the basic integrate and deintegrate dual-
slope phases discussed above, the TC820 design incorpo-
rates a "zero integrator output" phase and an "auto-zero"
phase. These additional phases ensure that the integrator
starts at 0V (even after a severe overrange conversion), and
that all offset voltage errors (buffer amplifier, integrator and
comparator) are removed from the conversion. A true digital
zero reading is assured without any external adjustments.
A complete conversion consists of four distinct phases:
(1) Zero Integrator Output
(2) Auto-Zero
(3) Signal Integrate
(4) Reference Deintegrate
Zero Integrator Output Phase
This phase guarantees that the integrator output is at 0V
before the system zero phase is entered, ensuring that the
true system offset voltages will be compensated for even
after an overrange conversion. The duration of this phase is
500 counts plus the unused deintegrate counts.
Auto-Zero Phase
During the auto-zero phase, the differential input signal
is disconnected from the measurement circuit by opening
internal analog switches, and the internal nodes are shorted
to Analog Common (0V
REF
) to establish a zero input condi-
tion. Additional analog switches close a feedback loop
around the integrator and comparator to permit comparator
offset voltage error compensation. A voltage established on
C
AZ
then compensates for internal device offset voltages
during the measurement cycle. The auto-zero phase re-
sidual is typically 10
μ
V to 15
μ
V. The auto-zero duration is
1500 counts.
Signal Integration Phase
Upon completion of the auto-zero phase, the auto-zero
loop is opened and the internal differential inputs connect to
V
IN+
and V
IN–
. The differential input signal is then integrated
for a fixed time period, which is 2000 counts (4000 clock
periods). The externally-set clock frequency is divided by
two before clocking the internal counters. The integration
time period is:
t
INT
=
The differential input voltage must be within the device's
common-mode range when the converter and measured
system share the same power supply common (ground). If
the converter and measured system do not share the same
power supply common, as in battery-powered applications,
V
IN–
should be tied to analog common.
Polarity is determined at the end of signal integration
phase. The sign bit is a "true polarity" indication in that
signals less than 1 LSB are correctly determined. This
allows precision null detection that is limited only by device
noise and auto-zero residual offsets.
1
R
INT
C
INT
∫
t
INT
V
IN
(t) dt =
V
REF
t
DEINT
R
INT
C
INT
4000
f
OSC
TC820
3-3/4 A/D CONVERTER WITH
FREQUENCY COUNTER
AND LOGIC PROBE
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| TC820CLW | 3-3/4 Digit A/D Converter with Frequency Counter and Logic Probe |
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| TC820CLW | 3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE |
| TC820CPL | 3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE |
| TC820 | 3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE |
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| TC820CKW713 | 功能描述:LCD 驅(qū)動器 3-3/4 A/D Converter RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TC820CLW | 功能描述:LCD 驅(qū)動器 3-3/4 A/D Converter RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TC820CLW713 | 功能描述:LCD 驅(qū)動器 3-3/4 A/D Converter RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TC820CPL | 功能描述:LCD 驅(qū)動器 3-3/4 A/D Converter RoHS:否 制造商:Maxim Integrated 數(shù)位數(shù)量:4.5 片段數(shù)量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TC8-20S2405R | 制造商:TRUMPOWER 制造商全稱:Tumbler Technologies + TRUMPower 功能描述:DC/DC CONVERTERS 2:1 Input, 12.5 to 20 Watt |
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