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| 型號： | TC7126ACLW713 |
| 元件分類： | ADC |
| 英文描述： | 1-CH DUAL-SLOPE ADC, PQCC44 |
| 封裝： | PLASTIC, LCC-44 |
| 文件頁數(shù)： | 4/22頁 |
| 文件大?。?/td> | 553K |
| 代理商： | TC7126ACLW713 |
TC7126/A
DS21458B-page 12
2002 Microchip Technology Inc.
6.5
Oscillator Components
COSC should be 50pF; ROSC is selected from the
equation:
EQUATION 6-2:
For a 48kHz clock (3 conversions per second),
R = 180k
.
Note that FOSC is 44 to generate the TC7126A's inter-
nal clock. The backplane drive signal is derived by
dividing FOSC by 800.
To achieve maximum rejection of 60Hz noise pickup,
the signal integrate period should be a multiple of
60Hz. Oscillator frequencies of 24kHz, 12kHz, 80kHz,
60kHz, 40kHz, etc. should be selected. For 50Hz rejec-
tion,
oscillator
frequencies
of
20kHz,
100kHz,
66-2/3kHz, 50kHz, 40kHz, etc. would be suitable. Note
that 40kHz (2.5 readings per second) will reject both
50Hz and 60Hz.
6.6
Reference Voltage Selection
A full scale reading (2000 counts) requires the input
signal be twice the reference voltage.
Note:
VFS =2VREF.
In some applications, a scale factor other than unity
may exist between a transducer output voltage and the
required digital reading. Assume, for example, a pres-
sure transducer output for 2000lb/in2 is 400mV. Rather
than dividing the input voltage by two, the reference
voltage should be set to 200mV. This permits the trans-
ducer input to be used directly.
Thedifferential reference canalsobeusedwherea
digital zero reading is required when VIN is not equal to
zero. This is common in temperature measuring instru-
mentation. A compensating offset voltage can be
applied between analog common and VIN-. The trans-
ducer output is connected between VIN+ and analog
common.
7.0
DEVICE PIN FUNCTIONAL
DESCRIPTION
(Pin Numbers Refer to the 40-Pin PDIP.)
7.1
Differential Signal Inputs
VIN+(Pin31), VIN-(Pin 30)
The TC7126A is designed with true differential inputs
and accepts input signals within the input stage
Common mode voltage range (VCM). Typical range is
V+ – 1V to V- + 1V. Common mode voltages are
removed from the system when the TC7126A operates
from a battery or floating power source (isolated from
measured system), and VIN- is connected to analog
common (VCOM) (seeFigure7-2).
In systems where Common mode voltages exist, the
TC7126A's 86 dB Common mode rejection ratio mini-
mizes error. Common mode voltages do, however,
affect the integrator output level. A worst case condition
exists if a large positive VCM exists in conjunction with
a full scale negative differential signal. The negative
signal drives the integrator output positive along with
VCM (see Figure 7-1). For such applications, the inte-
grator output swing can be reduced below the recom-
mended 2V full scale swing. The integrator output
will swing within 0.3V of V+ or V- without increased
linearity error.
FIGURE 7-1:
COMMON MODE
VOLTAGE REDUCES
AVAILABLE INTEGRATOR
SWING (VCOM ≠ VIN)
Required Full Scale Voltage*
VREF
20mV
100mV
2V
1V
FOSC =
0.45
RC
RI
+
–
VIN
CI
Integrator
VI =
[
VCM – VIN
Input
Buffer
CI = Integration capacitor
RI = Integration resistor
4000
FOSC
tI = Integration time =
Where:
VI
–
+
–
+
tI
RI CI
VCM
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|---|---|
| TC7126ACPL | 功能描述:LCD 驅(qū)動器 Low Power 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 |
| TC7126AIPL | 制造商:TELCOM 制造商全稱:TelCom Semiconductor, Inc 功能描述:3-1/2 DIGIT ANALOG-TO-DIGITAL CONVERTERS |
| TC7126ARCPL | 功能描述:LCD 驅(qū)動器 Low Power 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 |
| TC7126ARIPL | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:3-1/2 Digit Analog-to-Digital Converters |
| TC7126CKW | 功能描述:LCD 驅(qū)動器 Low Power 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 |
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