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General Description
The MAX1280/MAX1281 12-bit ADCs combine an 8-chan-
nel analog-input multiplexer, high-bandwidth track/hold,
and serial interface with high conversion speed and low
power consumption. The MAX1280 operates from a single
+4.5V to +5.5V supply; the MAX1281 operates from a sin-
gle +2.7V to +3.6V supply. Both devices' analog inputs
are software configurable for unipolar/bipolar and single-
ended/pseudo-differential operation.
The 4-wire serial interface connects directly to
SPITM/QSPITM/MICROWIRETM devices without external
logic. A serial strobe output allows direct connection to
TMS320-family digital signal processors. The MAX1280/
MAX1281 use an external serial-interface clock to per-
form successive-approximation analog-to-digital con-
versions. Both parts feature an internal +2.5V reference
and a reference-buffer amplifier with a ±1.5% voltage-
adjustment range. An external reference with a 1V to
V
DD1
range may also be used.
The MAX1280/MAX1281 provide a hard-wired SHDN
pin and four software-selectable power modes (normal
operation, reduced power, fast power-down, and full
power-down). These devices can be programmed to
automatically shut down at the end of a conversion or to
operate with reduced power. When using the power-
down modes, accessing the serial interface automatical-
ly powers up the devices, and the quick turn-on time
allows them to be powered down between all conver-
sions. This technique can cut supply current to under
100µA at reduced sampling rates.
The MAX1280/MAX1281 are available in 20-pin TSSOP
packages. These devices are higher-speed versions of
the MAX146/MAX147 (for more information, see the
respective data sheet).
Applications
Portable Data Logging
Data Acquisition
Medical Instruments
Battery-Powered Instruments
Pen Digitizers
Process Control
Features
o 8-Channel Single-Ended or 4-Channel
Pseudo-Differential Inputs
o Internal Multiplexer and Track/Hold
o Single-Supply Operation
+4.5V to +5.5V (MAX1280)
+2.7V to +3.6V (MAX1281)
o Internal +2.5V Reference
o 400ksps Sampling Rate (MAX1280)
o Low Power 2.5mA (400ksps)
1.3mA (Reduced-Power Mode)
0.9mA (Fast Power-Down Mode)
2µA (Full Power-Down)
o SPI/QSPI/MICROWIRE/TMS320-Compatible
4-Wire Serial Interface
o Software-Configurable Unipolar or Bipolar Inputs
o 20-Pin TSSOP Package
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1280/MAX1281
400ksps/300ksps, Single-Supply, Low-Power, 8-Channel,
Serial 12-Bit ADCs with Internal Reference
________________________________________________________________ Maxim Integrated Products
1
19-1684; Rev 0; 5/00
PART
TEMP.
RANGE
PIN-
PACKAGE
Ordering Information continued at end of data sheet.
Pin Configuration
Ordering Information
INL
(LSB)
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
MAX1280BCUP
0°C to +70°C
20 TSSOP
±1
MAX1280BEUP
-40°C to +85°C
20 TSSOP
±1
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
TOP VIEW
TSSOP
V
DD1
V
DD2
DIN
SSTRB
DOUT
GND
REFADJ
REF
COM
CH7
CH6
CH5
CH4
CH3
CH2
CH1
CH0
MAX1280
MAX1281
SHDN
CS
SCLK
MAX1280/MAX1281
400ksps/300ksps, Single-Supply, Low-Power, 8-Channel,
Serial 12-Bit ADCs with Internal Reference
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS--MAX1280
(V
DD1
= V
DD2
= +4.5V to +5.5V, COM = GND, f
SCLK
= 6.4MHz, 50% duty cycle, 16 clocks/conversion cycle (400ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
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 GND ............................................................ -0.3V to +6V
V
DD1
to V
DD2
........................................................ -0.3V to +0.3V
CH0CH7, COM to GND.......................... -0.3V to (V
DD1
+ 0.3V)
REF, REFADJ to GND .............................. -0.3V to (V
DD1
+ 0.3V)
Digital Inputs to GND .............................................. -0.3V to +6V
Digital Outputs to GND ............................ -0.3V to (V
DD2
+ 0.3V)
Digital Output Sink Current .................................................25mA
Continuous Power Dissipation (T
A
= +70°C)
20-Pin TSSOP (derate 7.0mW/°C above +70°C) .........559mW
Operating Temperature Ranges
MAX128_BCUP .................................................. 0°C to +70°C
MAX128_BEUP ............................................... -40°C to +85°C
Storage Temperature Range ............................ -60°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
SINAD > 68dB
-3dB point
f
IN
= 200kHz, V
IN
= 2.5Vp-p
f
IN1
= 99kHz, f
IN2
= 102kHz
No missing codes over temperature
Up to the 5th harmonic
CONDITIONS
MHz
0.5
6.4
f
SCLK
Serial Clock Frequency
ps
<50
Aperture Jitter
ns
10
Aperture Delay
ns
468
t
ACQ
Track/Hold Acquisition Time
µs
2.5
t
CONV
Conversion Time (Note 5)
kHz
350
Full-Linear Bandwidth
MHz
6
Full-Power Bandwidth
dB
-78
Channel-to-Channel Crosstalk
(Note 4)
dB
76
IMD
Intermodulation Distortion
dB
80
SFDR
Spurious-Free Dynamic Range
dB
-81
THD
Total Harmonic Distortion
Bits
12
Resolution
dB
70
SINAD
Signal-to-Noise plus Distortion
Ratio
LSB
±0.1
Channel-to-Channel Offset-Error
Matching
ppm/°C
±0.8
Gain-Error Temperature
Coefficient
±1.0
LSB
±1.0
DNL
Differential Nonlinearity
LSB
±6.0
Offset Error
LSB
±6.0
Gain Error (Note 3)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
%
40
60
Duty Cycle
DYNAMIC SPECIFICATIONS (100kHz sine-wave input, 2.5Vp-p, 400ksps, 6.4MHz clock, bipolar input mode)
DC ACCURACY (Note 1)
CONVERSION RATE
LSB
INL
Relative Accuracy (Note 2)
ELECTRICAL CHARACTERISTICS--MAX1280
(V
DD1
= V
DD2
= +4.5V to +5.5V, COM = GND, f
SCLK
= 6.4MHz, 50% duty cycle, 16 clocks/conversion cycle (400ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
mA
MAX1280/MAX1281
400ksps/300ksps, Single-Supply, Low-Power, 8-Channel,
Serial 12-Bit ADCs with Internal Reference
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS--MAX1280 (continued)
(V
DD1
= V
DD2
= +4.5V to +5.5V, COM = GND, f
SCLK
= 6.4MHz, 50% duty cycle, 16 clocks/conversion cycle (400ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
To power down the internal reference
For small adjustments, from 1.22V
0 to 1mA output load
On/off leakage current, V
CH_
= 0 or V
DD1
T
A
= +25°C
Bipolar, V
COM
or V
CH_
= V
REF
/2,
referenced to COM or CH_
Unipolar, V
COM
= 0
V/V
2.05
Buffer Voltage Gain
V
1.4
V
DD1
REFADJ Buffer Disable
Threshold
mV
±100
REFADJ Input Range
V
1.22
REFADJ Output Voltage
µF
0.01
10
Capacitive Bypass at REFADJ
µF
4.7
10
Capacitive Bypass at REF
mV/mA
0.1
2.0
Load Regulation (Note 7)
ppm/°C
±15
TC V
REF
REF Output Temperature
Coefficient
mA
30
REF Short-Circuit Current
V
2.480
2.500
2.520
V
REF
REF Output Voltage
pF
18
Input Capacitance
µA
±0.001
±1
Multiplexer Leakage Current
±V
REF
/2
V
V
REF
V
CH_
Input Voltage Range, Single-
Ended and Differential (Note 6)
V
IN
= 0 or V
DD2
In power-down, f
SCLK
= 0
V
REF
= 2.500V, f
SCLK
= 0
V
REF
= 2.500V, f
SCLK
= 6.4MHz
(Note 8)
pF
C
IN
Input Capacitance
µA
±1
I
IN
Input Leakage
V
0.2
V
HYST
Input Hysteresis
V
0.8
V
INL
Input Low Voltage
V
3.0
V
INH
Input High Voltage
5
320
µA
200
350
REF Input Current
V
1.0
V
DD1
+
50mV
REF Input Voltage Range
I
SINK
= 5mA
V
0.4
V
OL
Output Voltage Low
15
I
SOURCE
= 1mA
V
4
V
OH
Output Voltage High
CS = 5V
µA
±10
I
L
Three-State Leakage Current
CS = 5V
pF
15
C
OUT
Three-State Output Capacitance
ANALOG INPUTS (CH7CH0, COM)
EXTERNAL REFERENCE (Reference buffer disabled, reference applied to REF)
INTERNAL REFERENCE
DIGITAL INPUTS (DIN, SCLK, CS, SHDN)
DIGITAL OUTPUTS (DOUT, SSTRB)
Supply Current
MAX1280/MAX1281
400ksps/300ksps, Single-Supply, Low-Power, 8-Channel,
Serial 12-Bit ADCs with Internal Reference
4
_______________________________________________________________________________________
CONDITIONS
mA
2.5
4.0
I
VDD1 +
I
VDD2
Supply Current
V
4.5
5.5
V
DD1
,
V
DD2
Positive Supply Voltage
(Note 9)
1.3
2.0
0.9
1.5
µA
2
10
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
V
DD1
=
V
DD2
= 5.5V
ELECTRICAL CHARACTERISTICS--MAX1281
(V
DD1
= V
DD2
= +2.7V to +3.6V, COM = GND, f
SCLK
= 4.8MHz, 50% duty cycle, 16 clocks/conversion cycle (300ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
SINAD > 68dB
-3dB point
f
IN
= 150kHz, V
IN
= 2.5Vp-p
f
IN1
= 73kHz, f
IN2
= 77kHz
No missing codes over temperature
Up to the 5th harmonic
CONDITIONS
kHz
250
Full-Linear Bandwidth
MHz
3
Full-Power Bandwidth
dB
-78
Channel-to-Channel Crosstalk
(Note 4)
dB
76
IMD
Intermodulation Distortion
dB
80
SFDR
Spurious-Free Dynamic
Range
dB
-81
THD
Total Harmonic Distortion
LSB
±1.0
INL
Relative Accuracy (Note 2)
Bits
12
Resolution
dB
70
SINAD
Signal-to-Noise plus
Distortion Ratio
LSB
±0.2
Channel-to-Channel Offset-
Error Matching
ppm/°C
±1.6
Gain-Error Temperature
Coefficient
LSB
±1.0
DNL
Differential Nonlinearity
LSB
±6.0
Offset Error
LSB
±6.0
Gain Error (Note 3)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Operating mode (Note 10)
Reduced-power mode (Note 11)
Fast power-down (Note 11)
Full power-down (Note 11)
V
DD1
= V
DD2
= 5V ±10%, midscale input
mV
±0.5
±2.0
PSR
Power-Supply Rejection
POWER SUPPLY
DC ACCURACY (Note 1)
DYNAMIC SPECIFICATIONS (75kHz sine-wave input, 2.5Vp-p, 300ksps, 4.8MHz clock, bipolar input mode)
ELECTRICAL CHARACTERISTICS--MAX1280 (continued)
(V
DD1
= V
DD2
= +4.5V to +5.5V, COM = GND, f
SCLK
= 6.4MHz, 50% duty cycle, 16 clocks/conversion cycle (400ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
MAX1280/MAX1281
400ksps/300ksps, Single-Supply, Low-Power, 8-Channel,
Serial 12-Bit ADCs with Internal Reference
_______________________________________________________________________________________
5
ELECTRICAL CHARACTERISTICS--MAX1281 (continued)
(V
DD1
= V
DD2
= +2.7V to +3.6V, COM = GND, f
SCLK
= 4.8MHz, 50% duty cycle, 16 clocks/conversion cycle (300ksps), external
+2.5V at REF, REFADJ = V
DD1
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
Normal operating mode
Normal operating mode
Normal operating mode
CONDITIONS
MHz
0.5
4.8
f
SCLK
Serial Clock Frequency
ps
<50
Aperture Jitter
ns
10
Aperture Delay
ns
625
t
ACQ
Track/Hold Acquisition Time
µs
3.3
t
CONV
Conversion Time (Note 5)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
To power down the internal reference
For small adjustments, from 1.22V
0 to 0.75mA output load
On/off leakage current, V
CH_
= 0 or AV
DD
T
A
= +25°C
Bipolar, V
COM
or V
CH_
= V
REF
/2,
referenced to COM or CH_
Unipolar, V
COM
= 0
V/V
2.05
Buffer Voltage Gain
V
1.4
V
DD1
- 1
REFADJ Buffer Disable
Threshold
mV
±100
REFADJ Input Range
V
1.22
REFADJ Output Voltage
µF
0.01
10
Capacitive Bypass at REFADJ
µF
4.7
10
Capacitive Bypass at REF
mV/mA
0.1
2.0
Load Regulation (Note 7)
ppm/°C
±15
TC V
REF
REF Output Temperature
Coefficient
mA
15
REF Short-Circuit Current
V
2.480
2.500
2.520
V
REF
REF Output Voltage
pF
18
Input Capacitance
µA
±0.001
±1
Multiplexer Leakage Current
±V
REF
/2
%
40
60
Duty Cycle
V
V
REF
V
CH_
Input Voltage Range, Single-
Ended and Differential (Note 6)
V
IN
= 0 or V
DD2
In power-down, f
SCLK
= 0
V
REF
= 2.500V, f
SCLK
= 0
V
REF
= 2.500V, f
SCLK
= 4.8MHz
(Note 8)
pF
15
C
IN
Input Capacitance
µA
±1
I
IN
Input Leakage
V
0.2
V
HYST
Input Hysteresis
V
0.8
V
INL
Input Low Voltage
V
2.0
V
INH
Input High Voltage
5
REF Input Current
320
µA
200
350
V
1.0
V
DD1
+
50mV
REF Input Voltage Range
CONVERSION RATE
ANALOG INPUTS (CH7CH0, COM)
INTERNAL REFERENCE
EXTERNAL REFERENCE (Reference buffer disabled, reference applied to REF)
DIGITAL INPUTS (DIN, SCLK, CS, SHDN)
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