TC818A 查看數據表（PDF） - Microchip Technology
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TC818A Datasheet PDF : 24 Pages
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Vendors for piezo electric audio transducers are:
• Gulton Industries
Piezo Products Division
212 Durham Avenue
Metuchen, New Jersey 08840
(201) 548-2800
Typical P/Ns: 102-95NS, 101-FB-00
• Taiyo Yuden (USA) Inc.
Arlington Center
714 West Algonquin Road
Arlington Heights, Illinois 60005
Typical P/Ns: CB27BB, CB20BB, CB355BB
3.18 Display Decimal Point Selection
The TC818A provides a decimal point LCD drive sig-
nal. The decimal point position is a function of the
selected full scale range, as shown in Table 3-5.
TABLE 3-5: DECIMAL POINT SELECTION
Full Scale Range
2000V, 2000kΩ
200V, 200kΩ
20V, 20kΩ
2V, 2kΩ
200V, 200Ω
200mV, 200Ω
20mA
200mA
1*9
DP3
OFF
OFF
OFF
ON
OFF
OFF
OFF
OFF
*9
DP2
OFF
OFF
ON
OFF
OFF
OFF
ON
OFF
*9
DP1
OFF
ON
OFF
OFF
ON
ON
OFF
ON
3.19 AC-to-DC Converter Operational
Amplifier
The TC818A contains an on-chip operational amplifier
that may be connected as a rectifier for AC-to-DC volt-
age and current measurements. Typical operational
amplifier characteristics are:
• Slew Rate: 1V/µsec
• Unity Gain Bandwidth: 0.4MHz
• Open Loop Gain: 44dB
• Output Voltage Swing (Load = 10kΩ) ± 1.5V
(Referenced to Analog Common)
When the AC measurement option is selected, the
input buffer receives an input signal through switch
S14, rather than switch S11 (see Figure 3-1). With
external circuits, the AC Operating mode can be used
to perform other types of functions within the con-
straints of the internal operational amplifier. External
circuits that perform true RMS conversion, or a peak
hold function, are typical examples.
TC818A
3.20 Component Selection
3.20.1 INTEGRATION RESISTOR
SELECTION
The TC818A automatically selects one of two external
integration resistors. RVIBUF (Pin 55) is selected for
voltage and current measurement. RΩBUF (Pin 54) is
selected for resistance measurements.
3.20.2 RVIBUF SELECTION (PIN 55)
In auto-range operation, the TC818A operates with a
200mV maximum full scale potential at VI (Pin 44).
Resistive dividers at VR2 (Pin 41), VR3 (Pin 40), VR4
(Pin 43), and VR5 (Pin 42) are automatically switched
to maintain the 200V full scale potential.
In Manual mode, the Extended Operating mode is acti-
vated, giving a 300mV full scale potential at VI (Pin 44).
The integrator output swing should be maximized, but
saturations must be avoided. The integrator will swing
within 0.45V of VCC (Pin 28) and 0.5V of VSS (Pin 57)
without saturating. A ±2V swing is suggested. The
value of RVIBUF is easily calculated, assuming a worst
case extended resolution input signal:
Where:
VINT =
tI =
CI =
VMAX =
Integrator swing = ±2V
Integration time = 100msec
Integration capacitor = 0.1µF
Maximum input at VI = 300mV
EQUATION 3-1:
RVIBUF =
VMAX(TI)
VINT(CI)
= 150kΩ
3.20.3 RΩBUF SELECTION (PIN 54)
In ratiometric resistance measurements, the signal at
RX (Pin 50) is always positive, with respect to analog
common. The integrator swings negative.
The worst case integrator swing is for the 200Ω range
with the manual, extended resolution option.
The input voltage, VX (Pin 50) is easily calculated (see
Figure 3-15).
© 2002 Microchip Technology Inc.
DS21475B-page 19
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