Rainbow Electronics MAX1494 - Manual (Page 14)

MAX1492/MAX1494
The MAX1492/MAX1494 allow for full decimal-point con-
trol and feature leading zero suppression. Use the
DP_EN, DPSET1, and DPSET2 bits in the control register
to set the value of the decimal point. Tables 2 and 3 show
the truth tables of the DP_EN, DPSET1, and DPSET2. The
truth tables determine decimal-point usage.
The MAX1492/MAX1494 overrange and underrange
display is shown in Table 4.
Reference
The MAX1492/MAX1494 reference sets the full-scale
range of the ADC transfer function. With a nominal
2.048V reference, the ADC full-scale range is ±2V with
the RANGE bit equal to 0. With the RANGE bit set to 1,
the full-scale range is ±200mV. A decreased reference
voltage decreases full-scale range (see the Transfer
Functions section).
The MAX1492/MAX1494 accept either an external ref-
erence or an internal reference. The INTREF bit selects
the reference mode (see the Control Register
(Read/Write) section).
For internal-reference operation, set INTREF to 1, con-
nect REF- to GND and bypass REF+ to GND with a
4.7µF capacitor. The internal reference provides a nom-
inal 2.048V source between REF+ and GND. The inter-
nal-reference temperature coefficient is typically
40ppm/°C.
The default power-on state sets the MAX1492/
MAX1494 to use the external reference with INTREF
cleared to 0. The external reference inputs, REF+ and
REF-, are fully differential. For a valid external-reference
input, V
REF+ must be greater than V REF- . Bypass REF+
and REF- with a 0.1µF or greater capacitor to GND in
external-reference mode.
3.5- and 4.5-Digit, Single-Chip ADCs
with LCD Drivers
14 ______________________________________________________________________________________
BP1
BP2
BP3
DP DP
f
e
d
g
a b
c
X Y Z
Figure 8. Schematic of Display Digit
DP_EN DPSET1 DPSET2 DISPLAY OUTPUT ZERO INPUT READING
0 0 0 1 8 8 8 8 0
0 0 1 1 8 8 8 8 0
0 1 0 1 8 8 8 8 0
0 1 1 1 8 8 8 8 0
1 0 0 1 8 8 8.8 0.0
1 0 1 1 8 8.8 8 0.00
1 1 0 1 8.8 8 8 0.000
1 1 1 1.8 8 8 8 0.0000
Table 2. Decimal-Point Control Table (MAX1494)
DP_EN DPSET1 DPSET2 DISPLAY OUTPUT ZERO INPUT READING
X 0 0 1 8 8.8 0.0
X 0 1 1 8.8 8 0.00
X 1 0 1.8 8 8 0.000
X 1 1 1 8 8 8 000
Table 3. Decimal-Point Control Table (MAX1492)
X = Don’t care.
CONDITION MAX1492 MAX1494
OVERRANGE 1– – – 1– – – –
UNDERRANGE -1– – – -1– – – –
Table 4. LCD During Overrange and
Underrange Conditions