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| 型号： | TC826CBU713 |
| 元件分类： | ADC |
| 英文描述： | 1-CH DUAL-SLOPE ADC, PQFP64 |
| 封装： | PLASTIC, QFP-64 |
| 文件页数： | 2/18页 |
| 文件大小： | 348K |
| 代理商： | TC826CBU713 |
TC826
DS21477C-page 10
2005 Microchip Technology Inc.
4.2
System Timing
The oscillator frequency is divided by 32 prior to clock-
ing the internal counters. The three-phase measure-
ment cycle takes a total of 80 clock pulses. The 80
count cycle is independent of input signal magnitude.
Each phase of the measurement cycle has the follow-
ing length:
Auto-Zero Phase: 19 to 59 Counts
For signals less than full scale, the auto-zero is
assigned the unused reference integrate time period.
Signal Integrate: 20 Counts
This time period is fixed. The integration period is:
EQUATION 4-3:
Reference Integrate: 0 to 41 Counts
4.3
Reference Voltage Selection
A full scale reading requires the input signal be twice
the reference voltage. The reference potential is mea-
sured between REF IN (Pin 5) and ANALOG
COMMON (Pin 2).
TABLE 4-1:
The internal voltage reference potential available at
analog common will normally be used to supply the
converter’s reference. This potential is stable when-
ever the supply potential is greater than approximately
7V. In applications where an externally generated refer-
ence voltage is desired, refer to Figure 4-3.
The reference voltage is adjusted with a near full scale
input signal. Adjust for proper LCD display read out.
FIGURE 4-3:
EXTERNAL REFERENCE
4.4
Components Value Selection
4.4.1
INTEGRATING RESISTOR (RINT)
The desired full scale input voltage and output current
capability of the input buffer and integrator amplifier set
the integration resistor value. The internal class A out-
put stage amplifiers will supply a 1
μA drive current with
minimal linearity error. RINT is easily calculated for a
1
μA full scale current:
EQUATION 4-4:
4.4.2
INTEGRATING CAPACITOR (CINT)
The integrating capacitor should be selected to maxi-
mize integrator output swing. The integrator output will
swing to within 0.4V of VS+ or VS- without saturating.
The integrating capacitor is easily calculated:
EQUATION 4-5:
The integrating capacitor should be selected for low
dielectric absorption to prevent rollover errors. Polypro-
pylene capacitors are suggested.
4.4.3
AUTO-ZERO CAPACITOR (CAZ)
CAZ should be 2-3 times larger than the integration
capacitor. A polypropylene capacitor is suggested. Typ-
ical values from 0.14
μF to 0.068μF are satisfactory.
4.4.4
REFERENCE CAPACITOR (CREF)
A 1
μF capacitor is suggested. Low leakage capacitors,
such as polypropylene, are recommended.
Several capacitor/resistor combinations for common
full scale input conditions are given in Table 4-2.
Required Full Scale Voltage
VREF
20mV
10mV
2V
1V
TSI = 20
32
FOSC
Where FOSC is the externally set clock frequency.
TC826
REF IN
ANALOG
COMMON
2.50V
Reference
5
2
V+
8
V+
(b)
MCP1525
1
μF
Where VFS = Full Scale Analog Input
RINT =
Full Scale Voltage(V)
1 x 10 – 6
VFS
1 x 10 – 6
=
Where: VINT = Integrator Swing
FOSC = Oscillator Frequency
CINT =
VFS
RINT
640
FOSC x VINT
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| TC826-TB | 制造商:Thomas & Betts 功能描述:CABLE TIE MOUNT, NYLON 6.6, NATURAL; Mount Fixing Type:Screw; Mount Material:Nylon 6.6; Mount Color:Natural; Accessory Type:Mounting Base; For Use With:Cable Ties ;RoHS Compliant: Yes 制造商:Thomas & Betts 功能描述:Cable Accessories Two Direction Mounting Base Bulk |
| TC-827-SC | 制造商:Thomas & Betts 功能描述: |
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| TC828A | 制造商:TELCOM 制造商全称:TelCom Semiconductor, Inc 功能描述:Switched Capacitor Voltage Converter |
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