Detailed Description
The MAX1236–MAX1239 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 MAX1236/MAX1237 are
4-channel ADCs, and the MAX1238/MAX1239 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
MAX1238/MAX1239.
Power Supply
The MAX1236–MAX1239 operates from a single supply
and consumes 670µA (typ) at sampling rates up to
94.4ksps. The MAX1237/MAX1239 feature a 2.048V
internal reference and the MAX1236/MAX1238 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 MAX1236–MAX1239 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 (Write Cycle)
section) and GND (Table 3). In differential mode, the
analog-input multiplexer connects C
T/H
to the “+” and “-”
analog 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
MAX1236–MAX1239
2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
_______________________________________________________________________________________ 9
