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PDF TC826CBU Data sheet ( Hoja de datos )
| Número de pieza | TC826CBU | |
| Descripción | Analog-to-Digital Converter with Bar Graph Display Output | |
| Fabricantes | Microchip Technology | |
| Logotipo |  |
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TC826
Analog-to-Digital Converter with Bar Graph Display Output
Features
• Bipolar A/D Conversion
• 2.5% Resolution
• Direct LCD Display Drive
• ‘Thermometer’ BAR or DOT Display
• 40 Data Segments Plus Zero
• Over Range Plus Polarity Indication
• Precision On-Chip Reference: 35ppm/°C
• Differential Analog Input
• Low Input Leakage: 10pA
• Display Flashes on Over Range
• Display HOLD Mode
• Auto-Zero Cycle Eliminates Zero Adjust
Potentiometer
• 9V Battery Operation
• Low Power Consumption: 1.1mW
• 20mV to 2.0V Full Scale Operation
• Non-Multiplexed LCD Drive for Maximum
Viewing Angle
Device Selection Table
Part Number
TC826CBU
Package
64-Pin PQFP
Temperature Range
0°C to +70°C
General Description
In many applications, a graphical display is preferred
over a digital display. Knowing a process or system
operates, for example, within design limits is more valu-
able than a direct system variable read out. A bar or
moving dot display supplies information precisely with-
out requiring further interpretation by the viewer.
The TC826 is a complete analog-to-digital converter
with direct liquid crystal (LCD) display drive. The 40
LCD data segments plus zero driver give a 2.5% reso-
lution bar display. Full scale differential input voltage
range extends from 20mV to 2V. The TC826 sensitivity
is 500µV. A low drift 35ppm/°C internal reference, LCD
backplane oscillator and driver, input polarity LCD
driver, and over range LCD driver make designs simple
and low cost. The CMOS design required only 125µA
from a 9V battery. In +5V systems, a TC7660 DC to DC
converter can supply the -5V supply. The differential
analog input leakage is a low 10pA.
Two display formats are possible. The BAR mode dis-
play is like a ‘thermometer’ scale. The LCD segment
driver that equals the input, plus all below it are on. The
DOT mode activates only the segment equal to the
input. In either mode, the polarity signal is active for
negative input signals. An over range input signal
causes the display to flash and activates the over range
annunciator. A HOLD mode can be selected that
freezes the display and prevents updating.
The dual slope integrating conversion method with
auto-zero phase maximizes noise immunity and elimi-
nates zero scale adjustment potentiometers. Zero
scale drift is a low 5µV/°C. Conversion rate is typically
5 per second and is adjustable by a single external
resistor.
A compact, 0.5" square, flat package minimizes PC
board area. The high pin count LSI package makes
multiplexed LCD displays unnecessary. Low cost,
direct drive LCD displays offer the widest viewing angle
and are readily available. A standard display is avail-
able now for TC826 prototyping work.
© 2002 Microchip Technology Inc.
DS21477B-page 1
1 page  
TC826
TABLE 2-1:
Pin Number
(64-Pin PQFP)
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
PIN FUNCTION TABLE (CONTINUED)
Symbol
Description
BAR 24
BAR 25
BAR 26
BAR 27
BAR 28
BAR 29
BAR 30
NC
BAR 31
BAR 32
BAR 33
BAR 34
BAR 35
BAR 36
BAR 37
BAR 38
BAR 39
BAR 40
OR
POL-
BAR/DOT
HOLD
TEST
NC
LCD Segment driver: Bar 24.
LCD Segment driver: Bar 25.
LCD Segment driver: Bar 26.
LCD Segment driver: Bar 27.
LCD Segment driver: Bar 28.
LCD Segment driver: Bar 29.
LCD Segment driver: Bar 30.
No connection.
LCD Segment driver: Bar 31.
LCD Segment driver: Bar 32.
LCD Segment driver: Bar 33.
LCD Segment driver: Bar 34.
LCD Segment driver: Bar 35.
LCD Segment driver: Bar 36.
LCD Segment driver: Bar 37.
LCD Segment driver: Bar 38.
LCD Segment driver: Bar 39.
LCD Segment driver: Bar 40.
LCD segment driver that indicated input out-of-range condition.
LCD segment driver that indicates input signal is negative.
Input logic signal that selects BAR or DOT display format. Normally in BAR mode. Connect
to VSS through 1MΩ resistor for DOT format.
Input logic signal that prevents display from changing. Pulled high internally to inactive
state. Connect to VSS through 1MΩ series resistor for HOLD mode operation.
Input logic signal. Sets TC826 to BAR Display mode. BAR 0 to 40, plus OR flash on and
off. The POL- LCD driver is on. Pulled high internally to inactive state. Connect to VSS with
1MΩ series resistor to activate.
No connection.
© 2002 Microchip Technology Inc.
DS21477B-page 5
5 Page 
TABLE 4-2: SUGGESTED COMPONENT
VALUES
Comp.
2V
Full Scale
VREF ≈ 1V
2mV
Full Scale
VREF ≈ 100V
RINT
2MΩ
200kΩ
CINT
0.033µF
0.033µF
CREF
1µF
1µF
CAZ 0.068µF 0.068µF
ROSC
430kΩ
430kΩ
Note: Approximately 5 conversions/second.
20mV
Full Scale
VREF ≈ 10V
20kΩ
0.033µF
1µF
1.14µF
430kΩ
4.5 Differential Signal Inputs
The TC826 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
to V- +1V. Common mode voltages are removed from
the system when the TC826 operates from a battery or
floating power source (isolated from measured sys-
tem) and -IN is connected to analog common (VCOM).
In systems where Common mode rejection ratio mini-
mizes error. Common mode voltages do, however,
affect the integrator output level. Integrator output sat-
uration must be prevented. A worse 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. For such applications, the integrator output swing
can be reduced below the recommended 2V full scale
swing. The integrator output will swing within 0.3V of
VDD or VSS without increased linearity error.
4.6 Digital Section
The TC826 contains all the segment drivers necessary
to drive a liquid crystal display (LCD). An LCD back-
plane driver is included. The backplane frequency is
the external clock frequency divided by 256. A 430kΩ
OSC gets the backplane frequency to approximately
55Hz, with a 5V nominal amplitude. When a segment
driver is in phase with the backplane signal, the seg-
ment is ‘OFF’. An out-of-phase segment drive signal
causes the segment to be ‘ON’ or visible. This AC drive
configuration results in negligible DC voltage across
each LCD segment. This insures long LCD display life.
The polarity segment drive, -POL, is ‘ON’ for negative
analog inputs. If +IN and -IN are reversed, this indicator
would reverse. The TC826 transfer function is shown in
Figure 4-4.
TC826
FIGURE 4-4:
40
TRANSFER FUNCTION
Over Range
Indication
39
2
1
-0.5 0
-2 -1
0.5 1
2 3 39 39.5 40 40.5
Analog Input
(X VFS )
40
4.7 BAR/DOT Input (Pin 61)
The BAR/DOT input allows the user to select the dis-
play format. The TC826 powers up in the BAR mode.
Select the DOT display format by connecting BAR/DOT
to the negative supply (Pin 12) through a 1MΩ resistor.
4.8 HOLD Input (Pin 62)
The TC826 data output latches are not updated at the
end of each conversion if HOLD is tied to the negative
supply (Pin 12) through a 1MΩ resistor. The LCD dis-
play continuously displays the previous conversion
results.
The HOLD pin is normally pulled high by an internal
pull-up.
4.9 TEST Input (Pin 63)
The TC826 enters a Test mode with the TEST input
connected to the negative supply (Pin 12). The connec-
tion must be made through a 1MΩ resistor. The TEST
input is normally internally pulled high. A low input sets
the output data latch to all ones. The BAR Display
mode is set. The 41 LCD output segments (zero plus
40 data segments) and over range annunciator flash on
and off at 1/4 the conversion rate. The polarity annun-
ciator (POL-) segment will be on, but not flashing.
4.10 Over Range Display Operation
(OR, Pin 59)
An out-of-range input signal will be indicated on the
LCD display by the OR annunciator driver (Pin 59)
becoming active.
In the BAR display format, the 41 bar segments and the
over range annunciator, OR, will flash ON and OFF. The
flash rate is on fourth the conversion rate (FOSC/2560).
In the DOT Display mode, OR flashes and all other data
segment drivers are off.
© 2002 Microchip Technology Inc.
DS21477B-page 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet TC826CBU.PDF ] | |
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