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參數(shù)資料
| 型號(hào)： | TC835CBU |
| 廠商： | TelCom Semiconductor, Inc. |
| 英文描述： | PERSONAL COMPUTER DATA ACQUISITION A/D CONVERTER |
| 中文描述： | 個(gè)人計(jì)算機(jī)數(shù)據(jù)采集的A / D轉(zhuǎn)換器 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大?。?/td> | 206K |
| 代理商： | TC835CBU |
3-74
TELCOM SEMICONDUCTOR, INC.
PERSONAL COMPUTER
DATA ACQUISITION A/D CONVERTER
TC835
Power Supplies and Grounds
Power Supplies
The TC835 is designed to work from
±
5V supplies. For
single +5V operation, a TC7660 can provide a – 5V supply.
Grounding
Systems should use separate digital and analog ground
systems to avoid loss of accuracy.
Displays and Driver Circuits
TelCom Semiconductor manufactures two display de-
coder/driver circuits to interface the TC835 to an LCD or LED
display. Each drive has 28 outputs for driving four 7-segment
digit displays.
Device
Package
Description
TC7211AIPL
40-Pin Epoxy
4-Digit LCD Driver/Decoder
Several sources exist for LCD and LED display:
Display
Type
Manufacturer
Address
Hewlett Packard
Components
Litronix, Inc.
640 Page Mill Rd.
Palo Alto, CA 94304
19000 Homestead Rd.
Cupertino, CA 94010
720 Palomar Ave.
Sunnyvale, CA 94086
3415 Kanhi Kawa St.
Torrance, CA 90505
LED
LED
AND
LCD and
LED
LCD
Epson America, Inc.
For many dedicated applications where the input signal
is always of one polarity, the delay of the comparator need
not be a limitation. Since the nonlinearity and noise do not
increase substantially with frequency, clock rates of up to
~1 MHz may be used. For a fixed clock frequency, the extra
count or counts caused by comparator delay will be a
constant and can be subtracted out digitally.
The clock frequency may be extended above 200 kHz
without this error, however, by using a low-value resistor in
series with the integrating capacitor. The effect of the
resistor is to introduce a small pedestal voltage on to the
integrator output at the beginning of the reference integrate
phase. By careful selection of the ratio between this resistor
and the integrating resistor (a few tens of ohms in the
recommended circuit), the comparator delay can be com-
pensated and the maximum clock frequency extended by
approximately a factor of 3. At higher frequencies, ringing
and second-order breaks will cause significant nonlinearities
in the first few counts of the instrument.
The minimum clock frequency is established by leakage
on the auto-zero and reference capacitors. With most de-
vices, measurement cycles as long as 10 seconds give no
measurable leakage error.
The clock used should be free from significant phase or
frequency jitter. Several suitable low-cost oscillators are
shown in the applications section. The multiplexed output
means that if the display takes significant current from the
logic supply, the clock should have good PSRR.
Zero-Crossing Flip-Flop
The flip-flop interrogates the data once every clock
pulse after the transients of the previous clock pulse and
half-clock pulse have died down. False zero-crossings caused
by clock pulses are not recognized. Of course, the flip-flop
delays the true zero-crossing by up to one count in every
instance, and if a correction were not made, the display
would always be one count too high. Therefore, the counter
is disabled for one clock pulse at the beginning of the
reference integrate (deintegrate) phase. This one-count
delay compensates for the delay of the zero-crossing flip-
flop, and allows the correct number to be latched into the
display. Similarly, a one-count delay at the beginning of
auto-zero gives an overload display of 0000 instead of 0001.
No delay occurs during signal integrate, so that true ratiometric
readings result.
High-Speed Operation
The maximum conversion rate of most dual-slope A/D
converters is limited by the frequency response of the
comparator. The comparator in this circuit follows the inte-
grator ramp with a 3
μ
sec delay, and at a clock frequency of
200 kHz (5
μ
sec period), half of the first reference integrate
clock period is lost in delay. This means that the meter
reading will change from 0 to 1 with a 50
μ
V input, 1 to 2 with
150
μ
V, 2 to 3 at 250
μ
V, etc. This transition at midpoint is
considered desirable by most users; however, if the clock
frequency is increased appreciably above 200 kHz, the
instrument will flash "1" on noise peaks even when the input
is shorted.
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| TC835CKW | 功能描述:LED顯示驅(qū)動(dòng)器 4.5 D BCD A/D-PC Dat RoHS:否 制造商:Micrel 數(shù)位數(shù)量:5 片段數(shù)量: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PLCC-44 工作電源電壓:4.75 V to 11 V 最大電源電流:10 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝:Tube |
| TC835CKW713 | 功能描述:LED顯示驅(qū)動(dòng)器 4.5 D BCD A/D-PC Dat RoHS:否 制造商:Micrel 數(shù)位數(shù)量:5 片段數(shù)量: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PLCC-44 工作電源電壓:4.75 V to 11 V 最大電源電流:10 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝:Tube |
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