ICL7149 データシートの表示（PDF） - Intersil
部品番号
コンポーネント説明
メーカー
ICL7149 Datasheet PDF : 13 Pages
| |||
ICL7139, ICL7149
OSC OUT pin is not designed to drive large external loads,
loading on this pin should not exceed a single CMOS input.
The oscillator frequency is internally divided by two to gener-
ate the ICL7139 and ICL7149 clock. The frequency should
be 120kHz to reject 60Hz AC signals, and 100kHz to reject
50Hz signals.
OSC IN
5M
OSC OUT
330K
Ternary Input
The Ω/Volts/Amps logic input is a ternary, or 3-level input.
This input is internally tied to the common voltage through a
high-value resistor, and will go to the middle, or “Volts” state,
when not externally connected. When connected to V-,
approximately 5µA of current flows out of the input. In this
case, the logic level is the “Amps”, or low state. When con-
nected to V+, about 5µA of current flows into the input. Here,
the logic level is the “Ω”, or high state. For other pins, see
Table 2.
TABLE 2. TERNARY INPUTS CONNECTIONS
5pF
10pF
PIN
OPEN
NUMBER
V+
OR COM
V-
FIGURE 11. INTERNAL OSCILLATOR CIRCUIT DIAGRAM
Display Drivers
Figure 12 shows typical LCD Drive waveforms, RMS ON, and
RMS OFF voltage calculations. Duplex multiplexing is used to
minimize the number of connections between the ICL7139
and ICL7149 and the LCD. The LCD has two separate back-
planes. Each drive line can drive two individual segments, one
referenced to each backplane. The ICL7139 and ICL7149
drive 33/4 7-segment digits, 3 decimal points, and 11 annunci-
ators. Annunciators are used to indicate polarity, low battery
condition, and the range in use. Peak drive voltage across the
display is approximately 3V. An LCD with approximately
1.4VRMS threshold voltage should be used. The third voltage
level needed for duplex drive waveforms is generated through
an on-chip resistor string. The DC component of the drive
waveforms is guaranteed to be less than 50mV.
17
mA
µA
Test
18
Ω
V
Amps
19
HiΩ/DC
LoΩ/AC
Test
20
Hold
Auto
Test
Component Selection
For optimum performance while maintaining the low-cost
advantages of the ICL7139 and ICL7149, care must be
taken when selecting external components. This section
reviews specifications and performance effects of various
external components.
BACKPLANE
SEGMENT ON
SEGMENT OFF
VSEGMENT ON
VSEGMENT OFF
VPEAK V+
VPEAK / 2
O
DCOM
VPEAK
O
VPEAK
O
VRMS = 58-- VPEAK ON
VRMS = 58-- VPEAK OFF
VPEAK = 3V ±10%
RMS ON → 2.37V
RMS OFF → 1.06V
2VPEAK (VOLTAGE ACROSS ON SEGMENT)
O
-2VPEAK
VPEAK
O
-VPEAK
(VOLTAGE ACROSS OFF SEGMENT)
FIGURE 12. DUPLEXED LCD DRIVE WAVEFORMS
3-42
Share Link: 