Rainbow Electronics MAX11645 - Manual (Page 10)

MAX11644/MAX11645
Low-Power, 1-/2-Channel, I
2
C, 12-Bit ADCs
in Ultra-Tiny 1.9mm x 2.2mm Package
10 ______________________________________________________________________________________
Detailed Description
The MAX11644/MAX11645 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 MAX11644/MAX11645
measure either two single-ended or one differential
input(s). 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
MAX11644/MAX11645.
Power Supply
The MAX11644/MAX11645 operate from a single sup-
ply and consume 670μA (typ) at sampling rates up to
94.4ksps. The MAX11645 feature a 2.048V internal ref-
erence and the MAX11644 feature a 4.096V internal ref-
erence. All devices can be configured for use with an
external reference from 1V to V
DD .
Analog Input and Track/Hold
The MAX11644/MAX11645 analog-input architecture
contains an analog-input multiplexer (mux), a fully dif-
ferential 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
connects C
T/H between the analog input selected by
CS[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[0] (Table 4).
ANALOG
INPUT
MUX
AIN1
REF
AIN0
SCL
SDA
INPUT SHIFT REGISTER
SETUP REGISTER
CONFIGURATION REGISTER
CONTROL
LOGIC
REFERENCE
4.096V (MAX11644)
2.048V (MAX11645)
INTERNAL
OSCILLATOR
OUTPUT SHIFT
REGISTER
AND RAM
REF
T/H
12-BIT
ADC
V DD
GND
MAX11644
MAX11645
Figure 2. Simplified Functional Diagram
V DD
I OL
I
OH
V OUT
400pF
SDA
Figure 3. Load Circuit