Rainbow Electronics MAX1494 User Manual
Page 15
Figure 21 shows the MAX1492/MAX1494 operating with
an external single-ended reference. In this mode, REF-
is connected to GND and REF+ is driven with an exter-
nal 2.048V reference. Bypass REF+ to GND with a
0.47µF capacitor.
Figure 20 shows the MAX1492/MAX1494 operating with
an external differential reference. In this mode, REF-
is connected to the top of the strain gauge and REF+
is connected to the midpoint of the resistor-divider of
the supply.
MAX1492/MAX1494
3.5- and 4.5-Digit, Single-Chip ADCs
with LCD Drivers
______________________________________________________________________________________
15
φ1
φ2
φ3
φ1'
φ2'
φ3'
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V+
V
H
V
L
V-
V
LCD
BP1
BP2
BP3
ALL
OFF
a ON
g, d OFF
g ON
a, d OFF
d ON
a, g OFF
FREQUENCY = 107Hz
φ1, φ2, φ3 - - BP HIGH WITH RESPECT TO SEGMENT (BP+ TIME)
φ1', φ2', φ3' - - BP LOW WITH RESPECT TO SEGMENT (BP- TIME)
BP1 ACTIVE DURING
φ1 AND φ1'
BP2 ACTIVE DURING
φ2 AND φ2'
BP3 ACTIVE DURING
φ3 AND φ3'
V+ = DV
DD
, V
H
= 2/3 DV
DD
V
L
= 1/3 V
LCD
, V- = GND OR V
DISP
V
LCD
= D
VDD
- V
DISP
(MAX1494)
V
LCD
= D
VDD
- GND (MAX1492)
Figure 9. LCD Voltage Waveform—Combinations 1–4 (BP_, SEG2/5/8)