19-0464; Rev 2; 5/98
+2.7V to +5.25V, Lo w -P o w e r, 8 -Ch a n n e l,
S e ria l 1 0 -Bit ADCs
8/MAX149
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX148/MAX149 10-bit data-acquisition systems
c omb ine a n 8-c ha nne l multip le xe r, hig h-b a nd wid th
track/hold, and serial interface with high conversion
speed and low power consumption. They operate from a
single +2.7V to +5.25V supply, and sample to 133ksps.
Both devices’ analog inputs are software configurable for
unipolar/bipolar and single-ended/differential operation.
♦ 8-Channel Single-Ended or 4-Channel
Differential Inputs
♦ Single-Supply Operation: +2.7V to +5.25V
♦ Internal 2.5V Reference (MAX149)
♦ Low Power: 1.2mA (133ksps, 3V supply)
54µA (1ksps, 3V supply)
The 4-wire serial interface connects directly to SPI™/
QSPI™ and MICROWIRE™ devices without external
logic. A serial-strobe output allows direct connection to
TMS320-family digital signal processors. The MAX148/
MAX149 use either the internal clock or an external serial-
interface clock to perform successive-approximation
analog-to-digital conversions.
1µA (power-down mode)
♦ SPI/QSPI/MICROWIRE/TMS320-Compatible
4-Wire Serial Interface
♦ Software-Configurable Unipolar or Bipolar Inputs
♦ 20-Pin DIP/SSOP Packages
The MAX149 has an internal 2.5V reference, while the
MAX148 requires an external reference. Both parts have
a re fe re nc e -b uffe r a mp lifie r with a ± 1.5% volta g e -
adjustment range.
Ord e rin g In fo rm a t io n
These devices provide a hard-wired SHDN pin and a
s oftwa re -s e le c ta b le p owe r-d own, a nd c a n b e p ro-
grammed to automatically shut down at the end of a con-
version. Accessing the serial interface automatically
powers up the MAX148/MAX149, and the quick turn-on
time allows them to be shut down between all conver-
sions. This technique can cut supply current to under
60µA at reduced sampling rates.
INL
(LSB)
PART†
TEMP. RANGE PIN-PACKAGE
MAX148ACPP
MAX148BCPP
MAX148ACAP
MAX148BCAP
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
20 Plastic DIP
20 Plastic DIP
20 SSOP
±1/2
±1
±1/2
±1
20 SSOP
Ordering Information continued at end of data sheet.
Contact factory for availability of alternate surface-mount
packages.
†
The MAX148/MAX149 are available in a 20-pin DIP and a
20-pin SSOP.
For 4-c ha nne l ve rs ions of the s e d e vic e s , s e e the
MAX1248/MAX1249 data sheet.
__________Typ ic a l Op e ra t in g Circ u it
________________________Ap p lic a t io n s
+3V
Portable Data Logging
Medical Instruments
Pen Digitizers
Data Acquisition
V
V
CH0
DD
DD
0.1µF
0V TO
+2.5V
ANALOG
INPUTS
DGND
Battery-Powered Instruments
Process Control
MAX149
CH7
AGND
COM
CPU
I/O
VREF
CS
4.7µF
SCLK
SCK (SK)
MOSI (SO)
MISO (SI)
DIN
DOUT
REFADJ
0.01µF
SSTRB
SHDN
V
SS
Pin Configuration appears at end of data sheet.
SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.