Datasheet

+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
MAX148/MAX149
7
Pin Description
Figure 1. Load Circuits for Enable Time
Figure 2. Load Circuits for Disable Time
PIN NAME FUNCTION
1–8 CH0–CH7 Sampling Analog Inputs
9 COM
Ground Reference for Analog Inputs. COM sets zero-code voltage in single-ended mode. Must be
stable to ±0.5 LSB.
10 SHDN
Three-Level Shutdown Input. Pulling SHDN low shuts the MAX148/MAX149 down; otherwise, they
are fully operational. Pulling SHDN high puts the reference-buffer amplifier in internal compensation
mode. Leaving SHDN unconnected puts the reference-buffer amplifier in external compensation
mode.
11 V
REF
Reference-Buffer Output/ADC Reference Input. Reference voltage for analog-to-digital conversion.
In internal reference mode (MAX149 only), the reference buffer provides a 2.500V nominal output,
externally adjustable at REFADJ. In external reference mode, disable the internal buffer by pulling
REFADJ to V
DD
.
12 REFADJ Input to the Reference-Buffer Amplifier. To disable the reference-buffer amplifier, tie REFADJ to V
DD
.
13 AGND Analog Ground
14 DGND Digital Ground
15 DOUT Serial-Data Output. Data is clocked out at SCLK’s falling edge. High impedance when CS is high.
16 SSTRB
Serial-Strobe Output. In internal clock mode, SSTRB goes low when the MAX148/MAX149 begin
the A/D conversion, and goes high when the conversion is finished. In external clock mode, SSTRB
pulses high for one clock period before the MSB decision. High impedance when CS is high
(external clock mode).
17 DIN Serial-Data Input. Data is clocked in at SCLK’s rising edge.
18 CS
Active-Low Chip Select. Data will not be clocked into DIN unless CS is low. When CS is high, DOUT
is high impedance.
19 SCLK
Serial-Clock Input. Clocks data in and out of serial interface. In external clock mode, SCLK also sets
the conversion speed (duty cycle must be 40% to 60%).
20 V
DD
Positive Supply Voltage
a) HIGH-Z TO V
OH
AND V
OL
TO V
OH
b) HIGH-Z TO V
OL
AND V
OH
TO V
OL
DOUT
DGND
6kI
V
DD
DGND
DOUT
6kI
C
LOAD
50pF
C
LOAD
50pF
b) V
OL TO
HIGH-Z a) V
OH TO
HIGH-Z
DOUT
DGND
6kI
C
LOAD
50pF
V
DD
DOUT
DGND
6kI
C
LOAD
50pF