Rainbow Electronics MAX1139 - Manual (Page 9)

Detailed Description
The MAX1136–MAX1139 analog-to-digital converters
(ADCs) use successive-approximation conversion tech-
niques and fully differential input track/hold (T/H) cir-
cuitry to capture and convert an analog signal to a
serial 12-bit digital output. The MAX1136/MAX1137 are
4-channel ADCs, and the MAX1138/MAX1139 are
12-channel ADCs. These devices feature a high-speed
2-wire serial interface supporting data rates up to
1.7MHz. Figure 2 shows the simplified internal structure
for the MAX1138/MAX1139.
Power Supply
The MAX1136–MAX1139 operates from a single supply
and consumes 670µA (typ) at sampling rates up to
94.4ksps. The MAX1137/MAX1139 feature a 2.048V
internal reference and the MAX1136/MAX1138 feature
a 4.096V internal reference. All devices can be config-
ured for use with an external reference from 1V to V
DD
.
Analog Input and Track/Hold
The MAX1136–MAX1139 analog-input architecture con-
tains an analog-input multiplexer (mux), a fully differen-
tial track-and-hold (T/H) capacitor, T/H switches, a
comparator, and a fully differential switched capacitive
digital-to-analog converter (DAC) (Figure 4).
In single-ended mode the analog-input multiplexer con-
nects C
T/H between the analog input selected by
CS[3:0] (see the Configuration Setup Bytes section)
and GND (Table 3). In differential mode, the analog-
input multiplexer connects C
T/H
to the “+” and “-” ana-
log inputs selected by CS[3:0] (Table 4).
During the acquisition interval the T/H switches are in
the track position and C
T/H charges to the analog input
MAX1136–MAX1139
2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel, 2-Wire Serial 10-Bit ADCs
_______________________________________________________________________________________ 9
ANALOG
INPUT
MUX
AIN1
AIN11/REF
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN0
SCL
SDA
INPUT SHIFT REGISTER
SETUP REGISTER
CONFIGURATION REGISTER
CONTROL
LOGIC
REFERENCE
4.096V (MAX1138)
2.048V (MAX1139)
INTERNAL
OSCILLATOR
OUTPUT SHIFT
REGISTER
AND RAM
REF
T/H
10-BIT
ADC
V DD
GND
MAX1138
MAX1139
Figure 2. MAX1138/MAX1139 Functional Diagram
V
DD
I OL
I
OH
V
OUT
400pF
SDA
Figure 3. Load Circuit