For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
________________General Description
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 config-
urable for unipolar/bipolar and single-ended/differential
operation.
The 4-wire serial interface directly connects to SPITM,
QSPITM, and MicrowireTM 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 pro-
grammed 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 10A 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 pin-
compatible MAX147.
________________________Applications
Portable Data Logging
Medical Instruments
Battery-Powered Instruments
Data Acquisition
____________________________Features
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)
10A (1ksps)
1A (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
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
________________________________________________________________
Maxim Integrated Products
1
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
TOP VIEW
DIP/SSOP
V
DD
SCLK
CS
DIN
SSTRB
DOUT
DGND
AGND
V
DD
VREF
SHDN
COM
CH7
CH6
CH5
CH4
CH3
CH2
CH1
CH0
MAX1245
___________________Pin Configuration
V
DD
I/O
SCK (SK)*
MOSI (SO)
MISO (SI)
V
SS
SHDN
SSTRB
DOUT
DIN
SCLK
CS
COM
AGND
DGND
V
DD
CH7
0.1
F
0.1
F
CH0
0V to
+2.048V
ANALOG
INPUTS
MAX1245
CPU
+2.5V
VREF
+2.048V
___________Typical Operating Circuit
19-1066; Rev 0; 6/96
PART
MAX1245ACPP
MAX1245BCPP
MAX1245ACAP
0C to +70C
0C to +70C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
20 Plastic DIP
20 Plastic DIP
20 SSOP
________________Ordering Information
Ordering Information continued at end of data sheet.
Contact factory for availability of alternate surface-mount
packages.
*
Contact factory for availability.
MAX1245BCAP
0C to +70C
20 SSOP
MAX1245BC/D
0C to +70C
Dice*
INL
(LSB)
1/2
1
1/2
1
1
SPI and QSPI are registered trademarks of Motorola, Inc. Microwire is a registered trademark of National Semiconductor Corp.
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
DD
= +2.375V to +3.3V, COM = 0V, f
CLK
= 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps),
VREF = 2.048V applied to VREF pin, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
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.
V
DD
to AGND, DGND .............................................. -0.3V to +6V
AGND to DGND.................................................... -0.3V to +0.3V
CH0CH7, COM to AGND, DGND ............ -0.3V to (V
DD
+ 0.3V)
VREF to AGND........................................... -0.3V to (V
DD
+ 0.3V)
Digital Inputs to DGND............................................ -0.3V to +6V
Digital Outputs to DGND ........................... -0.3V to (V
DD
+ 0.3V)
Digital Output Sink Current .................................................25mA
Continuous Power Dissipation (T
A
= +70C)
Plastic DIP (derate 11.11mW/C above +70C) ......... 889mW
SSOP (derate 8.00mW/C above +70C) ................... 640mW
CERDIP (derate 11.11mW/C above +70C) .............. 889mW
Operating Temperature Ranges
MAX1245_C_P ................................................... 0C to +70C
MAX1245_E_P ................................................ -40C to +85C
Storage Temperature Range ............................ -60C to +150C
Lead Temperature (soldering, 10sec) ............................ +300C
8
s
35
65
t
CONV
Conversion Time (Note 5)
5.5
7.5
MHz
1.0
Full-Power Bandwidth
MHz
2.25
Small-Signal Bandwidth
dB
-85
Channel-to-Channel Crosstalk
dB
76
SFDR
Spurious-Free Dynamic Range
dB
-76
THD
Total Harmonic Distortion
dB
68
SINAD
Signal-to-Noise + Distortion Ratio
LSB
0.2
Channel-to-Channel Offset
Matching
ppm/C
0.25
Gain Temperature Coefficient
0.5
Bits
12
Resolution
LSB
Gain Error (Note 3)
0.5
4
LSB
1.0
INL
Relative Accuracy (Note 2)
LSB
1
DNL
LSB
0.5
4
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
External clock = 1.5MHz, 12 clocks/conversion
Internal clock,
SHDN = V
DD
Internal clock,
SHDN = FLOAT
MAX1245A
-3dB rolloff
50kHz, 2V
p-p
(Note 4)
Up to the 5th harmonic
MAX1245B
No missing codes over temperature
CONDITIONS
Differential Nonlinearity
ns
40
Aperture Delay
MHz
1.5
SHDN = FLOAT
ps
<50
Aperture Jitter
MHz
0.1
1.5
s
2.0
t
ACQ
Track/Hold Acquisition Time
External clock = 1.5MHz
0.225
Internal Clock Frequency
SHDN = V
DD
0
1.5
External Clock Frequency
Data transfer only
DC ACCURACY
(Note 1)
DYNAMIC SPECIFICATIONS
(10kHz sine-wave input, 0Vp-p to 2.048Vp-p, 100ksps, 1.5MHz external clock, bipolar input mode)
CONVERSION RATE
Offset Error
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
_______________________________________________________________________________________
3
Multiplexer Leakage Current
pF
15
C
IN
DIN, SCLK,
CS Input Capacitance
A
0.01
1
I
IN
DIN, SCLK,
CS Input Leakage
V
0.2
V
HYST
DIN, SCLK,
CS Input Hysteresis
V
0.8
V
INL
DIN, SCLK,
CS Input Low Voltage
A
0.01
10
Shutdown VREF Input Current
k
18
25
VREF Input Resistance
A
82
120
VREF Input Current
V
1.0
V
DD
+
50mV
VREF Input Voltage Range
(Note 8)
pF
16
Input Capacitance
0 to VREF
V
VREF/2
Input Voltage Range, Single-
Ended and Differential (Note 6)
A
0.01
1
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
(Note 7)
V
IN
= 0V or V
DD
Unipolar, COM = 0V
VREF = 2.048V
Bipolar, COM = VREF/2
On/off leakage current, V
IN
= 0V or V
DD
(Note 7)
CONDITIONS
V
V
DD
/2
V
DD
/2
- 0.3
+ 0.3
V
IM
SHDN Input Mid Voltage
A
4.0
I
IN
SHDN Input Current
V
0.4
V
INL
SHDN Input Low Voltage
V
V
DD
- 0.4
V
INH
SHDN Input High Voltage
SHDN = 0V or V
DD
nA
80
SHDN Maximum Allowed Leakage,
Mid Input
V
V
DD
/2
V
FLT
SHDN Voltage, Floating
SHDN = open
SHDN = open
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +2.375V to +3.3V, COM = 0V, f
CLK
= 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps),
VREF = 2.048V applied to VREF pin, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
mV
0.3
PSR
Supply Rejection (Note 9)
mA
0.8
1.3
I
DD
Positive Supply Current
A
0.01
10
I
L
Three-State Leakage Current
V
V
DD
- 0.375
V
OH
Output Voltage High
V
0.5
V
OL
Output Voltage Low
0.4
V
2.375
3.3
V
DD
Positive Supply Voltage
pF
15
C
OUT
Three-State Output Capacitance
V
DD
= 2.375V to 3.3V, full-scale input,
external reference = 2.048V
Operating mode, full-scale input
CS = V
DD
(Note 7)
CS = V
DD
I
SOURCE
=0.5mA
I
SINK
= 16mA
I
SINK
= 5mA
1.2
10
Power-down
V
2.0
V
INH
DIN, SCLK,
CS Input High Voltage
ANALOG/COM INPUTS
EXTERNAL REFERENCE
DIGITAL INPUTS
(DIN, SCLK, CS, SHDN)
DIGITAL OUTPUTS
(DOUT, SSTRB)
POWER REQUIREMENTS
A
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
4
_______________________________________________________________________________________
TIMING CHARACTERISTICS
(V
DD
= +2.375V to +3.3V, COM = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
Note 1:
Tested at V
DD
= +2.375V; COM = 0V; unipolar single-ended input mode.
Note 2:
Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has
been calibrated.
Note 3:
External reference (VREF = +2.048V), offset nulled.
Note 4:
Ground "on" channel; sine wave applied to all "off" channels.
Note 5:
Conversion time defined as the number of clock cycles multiplied by the clock period; clock has 50% duty cycle.
Note 6:
The common-mode range for the analog inputs is from AGND to V
DD
.
Note 7:
Guaranteed by design. Not subject to production testing.
Note 8:
ADC performance is limited by the converter's noise floor, typically 300Vp-p.
Note 9:
Measured as
|
V
FS
(2.375V) - V
FS
(3.3V)
|
.
DIN to SCLK Setup
ns
400
t
STR
CS Rise to SSTRB Output Disable
ns
240
t
SDV
CS Fall to SSTRB Output Enable
260
t
SSTRB
SCLK Fall to SSTRB
ns
300
t
CL
SCLK Pulse Width Low
ns
300
SCLK Pulse Width High
ns
0
CS to SCLK Rise Hold
ns
200
t
CSS
CS to SCLK Rise Setup
ns
400
t
TR
CS Rise to Output Disable
ns
240
t
DV
CS Fall to Output Enable
t
DO
SCLK Fall to Output Data Valid
ns
0
t
DH
DIN to SCLK Hold
ns
s
2.0
t
ACQ
Acquisition Time
0
t
SCK
SSTRB Rise to SCLK Rise
ns
200
t
DS
UNITS
MIN
TYP
MAX
SYMBOL
Internal clock mode only (Note 7)
External clock mode only, Figure 2
External clock mode only, Figure 1
Figure 1
Figure 2
Figure 1
CONDITIONS
Figure 1
ns
20
260
t
CSH
t
CH
__________________________________________Typical Operating Characteristics
(V
DD
= 2.5V, VREF = 2.048V, f
CLK
= 1.5MHz, C
LOAD
= 20pF, T
A
= +25C, unless otherwise noted.)
ns
1.25
2.375
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.00
V
DD
(V)
I
DD
(mA)
2.875
0.75
0.50
3.375
3.125
2.625
R
L
=
CODE = 101010100000
MAX1245-01
C
LOAD
= 50pF
C
LOAD
= 20pF
0.90
0.65
-55
-30
70
SUPPLY CURRENT
vs. TEMPERATURE
0.85
0.80
0.75
0.70
TEMPERATURE (C)
I
DD
(mA)
20
145
120
-5
45
95
MAX1245-02
R
L
=
CODE = 101010100000
0.50
0.00
INTEGRAL NONLINEARITY
vs. SUPPLY VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
DD
(V)
INL (LSB)
MAX1245-03
2.375
2.875
3.375
3.125
2.625
PARAMETER
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
_______________________________________________________________________________________
5
0.50
0
-55
-30
45
INTEGRAL NONLINEARITY
vs. TEMPERATURE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
TEMPERATURE (C)
INL (LSB)
20
-5
70
95
145
120
MAX1245-04
V
DD
= 2.375V
0.50
0
OFFSET vs. SUPPLY VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
DD
(V)
OFFSET (LSB)
MAX1245-05
2.375
2.875
3.375
3.125
2.625
0.50
0
-55
-30
45
OFFSET vs. TEMPERATURE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
TEMPERATURE (C)
OFFSET (LSB)
20
-5
70
145
120
95
MAX1245-06
0.50
0
CHANNEL-TO-CHANNEL OFFSET MATCHING
vs. SUPPLY VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
DD
(V)
OFFSET MATCHING (LSB)
MAX1245-07
2.375
2.875
3.375
3.125
2.625
0.50
0
-55
-30
20
GAIN ERROR
vs. TEMPERATURE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
TEMPERATURE (C)
GAIN ERROR (LSB)
-5
45
120 145
95
70
MAX1245-10
0.50
0
-55
-30
45
CHANNEL-TO-CHANNEL OFFSET MATCHING
vs. TEMPERATURE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
TEMPERATURE (C)
OFFSET MATCHING (LSB)
20
-5
70
145
120
95
MAX1245-08
0.50
0
GAIN ERROR
vs. SUPPLY VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
DD
(V)
GAIN ERROR (LSB)
MAX1245-09
2.375
2.875
3.375
3.125
2.625
0.50
0
CHANNEL-TO-CHANNEL GAIN MATCHING
vs. SUPPLY VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
V
DD
(V)
GAIN MATCHING (LSB)
MAX1245-11
2.375
2.875
3.375
3.125
2.625
0.50
0
-55
-30
20
CHANNEL-TO-CHANNEL GAIN MATCHING
vs. TEMPERATURE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
TEMPERATURE (C)
GAIN MATCHING (LSB)
-5
45
145
120
95
70
MAX1245-12
____________________________Typical Operating Characteristics (continued)
(V
DD
= 2.5V, VREF = 2.048V, f
CLK
= 1.5MHz, C
LOAD
= 20pF, T
A
= +25C, unless otherwise noted.)
PDF 
ZIP