TC826CBU データシートの表示（PDF） - Microchip Technology
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TC826CBU Datasheet PDF : 18 Pages
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TC826
4.11 Polarity Indication (POL-, Pin 60)
The TC826 converts and displays data for positive and
negative input signals. The POL LCD segment driver
(Pin 60) is active for negative signals.
4.12 Oscillator Operation
The TC826 external oscillator frequency, FOSC, is set
by resistor ROSC connected between pins 13 and 14.
The oscillator frequency versus resistance curve is
shown in Figure 4-5.
FIGURE 4-5:
OSCILLATOR
FREQUENCY VS. ROSC
50 20
18
40 16
14
30 12
10
TA = 25°C
VDD to VSS = 9V
20 8
6
10 4
2
00
0 2 4 6 8 10 12 14 16 18 20
ROSC (X 100kΩ)
FOSC is divided by 32 to provide an internal system
clock, FYSY. Each conversion requires 80 internal
clock cycles. The internal system clock is divided by 8
to provide the LCD backplane drive frequency. The dis-
play flash rate during an input out-of-range signal is set
by dividing FSYS by 320.
The internal oscillator may be bypassed by driving
OSC1 (Pin 13) with an external signal generator. OSC2
(Pin 14) should be left unconnected.
The oscillator should swing from VDD to VSS in single
supply operation (Figure 4-6). In dual supply operation,
the signal should swing from power supply ground to
VDD.
FIGURE 4-6:
EXTERNAL OSCILLATOR
CONNECTION
8
9V
TC826
12
13
OSC1
14
OSC2
0.1µf
External
Oscillator
A. Single 9V Supply
VDD 8
TC826 13
0.1µf
VSS 12
Oscillator
VDD = 5V
Power
Supply
B. Dual Supply
VSS = 5V
4.13 LCD Display Format
The input signal can be displayed in two formats
(Figure 4-7). The BAR/DOT input (Pin 61) selects the
format. The TC826 measurement cycle operates
identically for either mode.
FIGURE 4-7:
DISPLAY OPTION
FORMATS
A. BAR Mode
1. Input = 0
Bar 4
Off
Bar 3
Off
Bar 2
Off
Bar 1
Off
Bar 0
On
2. Input = 5%
of Full Scale
Off
Off
On
On
On
B. DOT Mode
1. Input = 0
Bar 4
Off
Bar 3
Off
Bar 2
Off
Bar 1
Off
Bar 0
On
2. Input = 5%
of Full Scale
Off
Off
On
Off
Off
DS21477B-page 12
© 2002 Microchip Technology Inc.
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