MAX1108 Datasheet, PDF (13/20 Pages) Maxim Integrated Products – Single-Supply, Low-Power, 2-Channel, Serial 8-Bit ADCs

Single-Supply, Low-Power,
2-Channel, Serial 8-Bit ADCs
Table 1. Control Byte Format
BIT 7
(MSB)
START
BIT 6
SEL2
BIT 5
SEL1
BIT 4
SEL0
BIT 3
I/ECLK
BIT 2
I/EREF
BIT 1
REFSHDN
BIT 0
(LSB)
SHDN
BIT
7 (MSB)
6
5
4
3
2
1
0 (LSB)
NAME
START
SEL2
SEL1
SEL0
I/ECLK
I/EREF
REFSHDN
SHDN
DESCRIPTION
The first logic “1” bit after CS goes low defines the beginning of the control byte.
Selects the mode of operation (Table 2).
1 = external clock, 0 = internal clock. The SAR can be driven by the internal oscillator, or with the
SCLK signal.
1 = internal reference, 0 = external reference. Internal reference selects +2.048V (MAX1108) or
+4.096V (MAX1109), or an external reference can be applied to the REF pin.
1 = operational (if I / EREF = 1), 0 = reference shutdown. When using an external reference, power
consumption can be minimized by powering down the internal reference separately (I / EREF = 0).
REFSHDN must be set to 0 when SHDN = 0.
1 = operational, 0 = power down. For a full power down set REFSHDN = SHDN = 0. (See Power-
Down Mode section.)
Table 2. Conversion Configuration
SEL2
1
1
1
1
0
0
0
0
SEL1
1
1
0
0
1
1
0
0
SEL0
1
0
1
0
1
0
1
0
SAMPLED INPUT
(SI)
CH0
CH1
CH0
CH1
CH0
CH1
CH0
V_DD / 2
REFERENCE INPUT
(RI)
COM
COM
GND
GND
COM
COM
CH1
GND
CONVERSION MODE
Unipolar
Unipolar
Unipolar
Unipolar
Bipolar
Bipolar
Bipolar
Unipolar
Table 3. Full- and Zero-Scale Voltages
UNIPOLAR MODE
Zero Scale
Full Scale
Negative
Full Scale
RI*
RI + V_REF
RI - V_REF / 2
*RI = Reference Input (Table 2)
BIPOLAR MODE
Zero
Scale
RI
Positive
Full Scale
RI + V_REF / 2
______________________________________________________________________________________ 13