TC811 查看數據表（PDF） - Microchip Technology
零件编号
产品描述 (功能)
生产厂家
TC811
Microchip Technology
TC811 Datasheet PDF : 14 Pages
| |||
3-1/2 Digit Analog-To-Digital Converter with
Hold and Differential Reference Inputs
TC811
Oscillator
Freq. (kHz)
32.768
40
Full-Scale Voltage (VFS)
200mV
2.0V
RINT CINT RINT CINT
180k 0.068µF
150k 0.068µF
Figure 6b.
1.8M
1.5M
0.068µF
0.068µF
DEVICE PIN FUNCTIONAL DESCRIPTION
Differential Signal
VIN– (Pin 30))
Inputs
(VIN+
(Pin
31),
The TC811 is designed with true differential inputs and
accepts input signals within the input stage common mode
voltage range (VCM). The typical range is V+ – 1.0 to V– +
1.5V. Common-mode voltages are removed from the sys-
tem when the TC811 operates from a battery or floating
power source (isolated from measured system) and VIN– is
connected to Analog Common. (see Figure 8)
In systems where common-mode voltages exist, the
86dB common-mode rejection ratio minimizes error. Com-
mon-mode voltages do, however, affect the integrator out-
put level. A worse case condition exists if a large positive
VCM exists in conjunction with a full-scale negative differen-
tial signal. The negative signal drives the integrator output
positive along with VCM (Figure 8). For such applications the
integrator output swing can be reduced below the recom-
mended 2.0V full-scale swing. The integrator output will
swing within 0.3V of V+ or V– without increased linearity
error.
+
Reference (VREF (Pin
36), VR–EF
(Pin
33))
Unlike the ICL7116, the TC811 has a differential refer-
ence as well as the “hold” function. The differential reference
inputs permit ratiometric measurements and simplify inter-
facing with sensors such as load cells and temperature
sensors. The TC811 is ideally suited to applications in hand-
held multimeters, panel meters, and portable instrumenta-
tion. The reference voltage can be generated anywhere
within the V+ to V– power supply range.
To prevent rollover type errors from being induced by
large common-mode voltages, CREF should be large com-
pared to stray node capacitance. A 0.1µF capacitor is a
typical value.
The TC811 offers a significantly improved Analog Com-
mon temperature coefficient. This provides a very stable
voltage suitable for use as a voltage reference. The tem-
perature coefficient of Analog Common is typically
35ppm/°C.
+
VIN
–
VCM
INPUT
BUFFER
+
RI
–
CI
–
+
VI
INTEGRATOR
[ VI
Where:
=
TI
RI CI
VCM – VIN
TI
=
INTEGRATION TIME =
4000
fOSC
CI = INTEGRATION CAPACITOR
RI = INTEGRATION RESISTOR
Figure 8. Common-Mode Voltage Reduces Available
Integrator Swing. (VCOM ≠ VIN)
SEGMENT
DRIVE
LCD DISPLAY
MEASURED
SYSTEM
V+
V–
GND
V+ V– GND
POWER
SOURCE
VBUF
V+
CAZ VINT
V–
TC811
ANALOG
COMMON
VRE– F
VR+ EF
V+
POL BP
OSC1
20MΩ
OV –SC2
470k
10pF
40kHZ
20 pF
+
9V
Figure 7. Common-Mode Voltage Removed in Battery Operation With VI–N = Analog Common
© 2001 Microchip Technology Inc. DS21472A
9
V+
V+
TC811-7 11/5/96
Share Link: