
MAX1202/MAX1203
5V, 8-Channel, Serial, 12-Bit ADCs
with 3V Digital Interface
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19
External and Internal References
The MAX1202 can be used with an internal or external
reference, whereas an external reference is required for
the MAX1203. An external reference can be connected
directly at the REF terminal, or at the REFADJ pin.
An internal buffer is designed to provide 4.096V at
REF for both the MAX1202 and the MAX1203. The
MAX1202’s internally trimmed 2.44V reference is
buffered with a gain of 1.68. The MAX1203’s REFADJ
pin is buffered with a gain of 1.64, to scale an external
2.5V reference at REFADJ to 4.096V at REF.
MAX1202 Internal Reference
The MAX1202’s full-scale range using the internal
reference is 4.096V with unipolar inputs and ±2.048V
with bipolar inputs. The internal reference voltage is
adjustable to ±1.5% with the circuit of Figure 17.
Figure 12b. Timing Diagram for Power-Down Modes, Internal Clock
Figure 12c. Additional IDD Shutdown Supply Current vs. VIH
for Each Digital Input at a Logic 1
Figure 13. MAX1202 FULLPD/FASTPD Power-Up Sequence
FULL
POWER-DOWN
POWERED
UP
POWERED UP
DATA VALID
INTERNAL CLOCK MODE
SX XXXX 10
S
0 0
XX
X
S
MODE
DOUT
DIN
CLOCK
MODE
SETS INTERNAL
CLOCK MODE
SETS FULL
POWER-DOWN
CONVERSION
SSTRB
10 0
DIN
REFADJ
REF
2.5V
0V
4V
0V
10 1
1
11
0 0
10 1
FULLPD
FASTPD
NOPD
FULLPD
FASTPD
2ms WAIT
COMPLETE CONVERSION SEQUENCE
tBUFFEN ≈ 15s
τ = RC = 20k x CREFADJ
(ZEROS)
CH1
CH7
(ZEROS)
0
-60
10
5
TEMPERATURE (°C)
SUPPLY
CURRENT
PER
INPUT
(
A)
100
25
20
15
-20
60
140
40
35
30
20
(VDD - VIH) = 1.95V
(VDD - VIH) = 2.55V
(VDD - VIH) = 2.25V