19-1066; Rev 1; 11/09
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
____________________________Features
The MAX1245 12-bit data-acquisition system combines
an 8-channel multiplexer, high-bandwidth track/hold, and
serial interface with high conversion speed and ultra-low
power consumption. It operates from a single +2.375V to
+3.3V supply, and its analog inputs are software configurable for unipolar/bipolar and single-ended/differential
operation.
o Single +2.375V to +3.3V Operation
o 8-Channel Single-Ended or 4-Channel
Differential Analog Inputs
o Low Power: 0.8mA (100ksps)
10µA (1ksps)
1µA (power-down mode)
o Internal Track/Hold, 100kHz Sampling Rate
o SPI/QSPI/MICROWIRE/TMS320-Compatible
4-Wire Serial Interface
o Software-Configurable Unipolar or Bipolar Inputs
o 20-Pin DIP/SSOP Packages
The 4-wire serial interface directly connects to SPI™,
QSPI™, and MICROWIRE™ devices without external
logic. A serial strobe output allows direct connection to
TMS320-family digital signal processors. The MAX1245
works with an external reference, and uses either the
internal clock or an external serial-interface clock to
perform successive-approximation analog-to-digital
conversions.
This device provides a hard-wired SHDN pin and a
software-selectable power-down, and can be programmed to automatically shut down at the end of a
conversion. Accessing the serial interface powers up
the MAX1245, and the quick turn-on time allows it to be
shut down between conversions. This technique can
cut supply current to under 10µA at reduced sampling
rates.
The MAX1245 is available in a 20-pin DIP package and
an SSOP that occupies 30% less area than an 8-pin DIP.
For supply voltages from +2.7V to +5.25V, use the pincompatible MAX147.
________________________Applications
Portable Data Logging
Medical Instruments
Battery-Powered Instruments
Data Acquisition
___________Typical Operating Circuit
+2.5V
0V to
+2.048V
ANALOG
INPUTS
VDD
VDD
CH0
0.1µF
CPU
MAX1245
+2.048V
0.1µF
VREF
CS
SCLK
DIN
DOUT
SSTRB
SHDN
PART*
TEMP RANGE
I/O
SCK (SK)
MOSI (SO)
MISO (SI)
PIN-PACKAGE
INL
(LSB)
±1/2
MAX1245ACPP
0°C to +70°C
20 Plastic DIP
MAX1245BCPP
0°C to +70°C
20 Plastic DIP
MAX1245ACAP
0°C to +70°C
20 SSOP
20 SSOP
±1
±1/2
±1
MAX1245BCAP
0°C to +70°C
MAX1245AEPP
-40°C to +85°C
20 Plastic DIP
±1/2
MAX1245BEPP
-40°C to +85°C
20 Plastic DIP
±1
MAX1245AEAP
-40°C to +85°C
20 SSOP
±1/2
MAX1245BEAP
-40°C to +85°C
20 SSOP
±1
*Contact factory for availability of alternate surface-mount packages.
___________________Pin Configuration
TOP VIEW
CH0 1
20 VDD
CH1 2
19 SCLK
CH2 3
18 CS
CH3 4
DGND
AGND
COM
CH7
________________Ordering Information
MAX1245
17 DIN
CH4 5
16 SSTRB
CH5 6
15 DOUT
CH6 7
14 DGND
CH7 8
13 AGND
COM 9
12 VDD
SHDN 10
11 VREF
VSS
DIP/SSOP
SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX1245
________________General Description
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
ABSOLUTE MAXIMUM RATINGS
SSOP (derate 8.00mW/°C above +70°C) ................... 640mW
CERDIP (derate 11.11mW/°C above +70°C) .............. 889mW
Operating Temperature Ranges
MAX1245_C_P ................................................... 0°C to +70°C
MAX1245_E_P ................................................ -40°C to +85°C
Storage Temperature Range ............................ -60°C to +150°C
Lead Temperature (soldering, 10sec) ............................ +300°C
VDD to AGND, DGND .............................................. -0.3V to +6V
AGND to DGND.................................................... -0.3V to +0.3V
CH0–CH7, COM to AGND, DGND ............ -0.3V to (VDD + 0.3V)
VREF to AGND........................................... -0.3V to (VDD + 0.3V)
Digital Inputs to DGND............................................ -0.3V to +6V
Digital Outputs to DGND ........................... -0.3V to (VDD + 0.3V)
Digital Output Sink Current .................................................25mA
Continuous Power Dissipation (TA = +70°C)
Plastic DIP (derate 11.11mW/°C above +70°C) ......... 889mW
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = +2.375V to +3.3V, VCOM = 0V, fCLK = 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps),
VREF = 2.048V applied to VREF pin, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
DC ACCURACY (Note 1)
Resolution
MIN
TYP
MAX
12
Relative Accuracy (Note 2)
INL
Differential Nonlinearity
DNL
UNITS
Bits
MAX1245A
±0.5
MAX1245B
±1.0
No missing codes over temperature
LSB
±1
LSB
Offset Error
±0.5
±4
LSB
Gain Error (Note 3)
±0.5
±4
LSB
Gain Temperature Coefficient
±0.25
ppm/°C
Channel-to-Channel Offset
Matching
±0.2
LSB
DYNAMIC SPECIFICATIONS (10kHz sine-wave input, 0Vp-p to 2.048Vp-p, 100ksps, 1.5MHz external clock, bipolar input mode)
Signal-to-Noise + Distortion Ratio
SINAD
68
dB
Total Harmonic Distortion
THD
Spurious-Free Dynamic Range
SFDR
Up to the 5th harmonic
-76
76
dB
dB
Channel-to-Channel Crosstalk
50kHz, 2Vp-p (Note 4)
-85
dB
Small-Signal Bandwidth
-3dB rolloff
2.25
MHz
1.0
MHz
Full-Power Bandwidth
CONVERSION RATE
Conversion Time (Note 5)
Track/Hold Acquisition Time
tCONV
tACQ
Internal clock, SHDN = open
5.5
7.5
Internal clock, SHDN = VDD
35
65
µs
External clock = 1.5MHz, 12 clocks/conversion
8
2.0
µs
External clock = 1.5MHz
Aperture Delay
40
ns
Aperture Jitter
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