TC820 TelCom Semiconductor, TC820 Datasheet - Page 21

• Manufacturer Part Number: TC820
• Description: 3-3/4 DIGIT A/D CONVERTER WITH FREQUENCY COUNTER AND LOGIC PROBE
• Manufacturer: TelCom Semiconductor

3-3/4 A/D CONVERTER WITH
FREQUENCY COUNTER
AND LOGIC PROBE
a SEGMENT
SEGMENT
ALL OFF
d, g OFF
BP1
BP2
BP3
TELCOM SEMICONDUCTOR, INC.
ALL ON
a, g ON
d OFF
LINE
ON
Figure 25. Typical Display Output Waveforms
HIGH
LOW
Figure 24. Backplane Waveforms
PIN 1
Figure 26. Typical TC820 LCD
OVER
PEAK
BATT
V DD
V H
V L
V DISP
V DD
V H
V L
V DISP
V DD
V H
V L
V DISP
V DD
V H
V L
V DISP
LCD Source
a standard display for the TC820 (Figure 26), Part No. ST-
1355-M1, is available from:
Annunciator Output
at the backplane frequency (for example, 167Hz when
f
– V
annunciator output turns it on; connecting it to its backplane
turns it off.
LCD Drive Voltage (V
V
internally connected to DGND, providing a typical LCD drive
voltage of 5V
LCDs require that the drive levels vary with temperature to
maintain good viewing angle and display contrast. In this
case, the TC820 44-pin package provides a pin connection
for V
adjusted to give a temperature compensation of about
10mV/ C between V
and V
cannot exceed 0.3V below GND.
Crystal Source
OSC
DISP
DISP
Although most users will design their own custom LCD,
Crystaloid (USA)
Crystaloid Electronics
P.O. Box 628
5282 Hudson Dr.
Hudson, OH 44238
Phone: [phone]
Fax: [phone]
The annunciator output is a square wave running
The peak-to-peak LCD drive voltage is equal to (V
For applications with a wide temperature range, some
Two sources of the 40 kHz crystal are:
Statek Corp.
512 N. Main St.
Orange, CA 92668
Phone: [phone]
Fax: [phone]
Part #: CX-1V-40.0
= 40kHz). The peak-to-peak amplitude is equal to (V
DISP
). In the 40-pin dual-in-line package (DIP), V
DISP
). Connecting an annunciator of the LCD to the
. Figure 27 shows TC820 circuits that can be
should have a low turn-on voltage because V
P-P
.
DD
and V
DISP
DISP
)
Crystaloid (Europe)
Rep France
102, rue des Nouvelles
F92150 Suresnes
France
Phone: [phone]
Fax: [phone]
SPK Electronics
2F-1, No. 312, Sec. 4,
Taipei, Taiwan R.O.C.
Phone: [phone]
Fax: [phone]
Part#: QRT-38-40.0kHz
. The diode between GND
Jen Ai Rd
TC820
DISP
3-169
DD
DISP
DD
is
–
1
2
3
4
5
6
7
8