MAX1304 Maxim, MAX1304 Datasheet - Page 27

• Manufacturer Part Number: MAX1304
• Description: 8-/4-/2-Channel / 12-Bit / Simultaneous-Sampling ADCs with 10V / 5V / and 0 to +5V Analog Input Ranges
• Manufacturer: Maxim

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
Table 5 and Figure 12 show the offset binary transfer
function for the MAX1304/MAX1305/MAX1306 with a 0
to +5V input range. The full-scale input range (FSR) is
two times the voltage at REF. The internal +2.5V refer-
ence gives a +5V FSR, while an external +2V to +3V
reference allows an FSR of +4V to +6V, respectively.
Calculate the LSB size using:
which equals 1.22mV when using a 2.5V reference.
Table 5. 0 to 5V Unipolar Code Table
OUTPUT CODE
1111 1111 1111
1111 1111 1110
1000 0000 0001
1000 0000 0000
0111 1111 1111
0000 0000 0001
0000 0000 0000
DIGITAL
BINARY
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
= 0xFFF
= 0xFFE
= 0x801
= 0x800
= 0x7FF
= 0x001
= 0x000
DIGITAL OUTPUT
1
______________________________________________________________________________________
EQUIVALENT
LSB
DECIMAL
(CODE
CODE
4095
4094
2049
2048
2047
=
1
0
2
10
Unipolar 0 to +5V Devices
x V
)
2
Transfer Functions
12
REF
(
+4.9994 ± 0.5 LSB
+4.9982 ± 0.5 LSB
+2.5018 ± 0.5 LSB
+2.5006 ± 0.5 LSB
+2.4994 ± 0.5 LSB
+0.0018 ± 0.5 LSB
+0.0006 ± 0.5 LSB
INPUT VOLTAGE
V
V
REFMS
REF
(V)
= +2.5V
= +2.5V
)
The input range is centered about V
to +2.5V. For a custom midscale voltage, drive REF
with an external voltage source and MSV will follow
REF
ples into the ADC result. Use a precision, low-drift volt-
age reference with adequate bypassing to prevent MSV
from degrading ADC performance. For maximum FSR,
do not violate the absolute maximum voltage ratings of
the analog inputs when choosing MSV.
Determine the input voltage as a function of V
V
Figure 12. 0 to +5V Unipolar Transfer Function
MSV
MS
, and the output code in decimal using:
0x0003
0x0002
0x0001
0x0000
0xFFD
0xFFC
0xFFF
0xFFE
0x801
0x800
0x7FF
. Noise present on MSV or REF
V
CH_
0
= LSB x CODE
1
2
3
INPUT VOLTAGE (LSBs)
2046 2048 2050
10
2 x V
(MSV)
+ V
REF
MSV
MSV
1 LSB =
MS
- 2.500V
, internally set
4093
directly cou-
2 x V
2
12
REF
4095
REF
MS
27
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