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19-1480; Rev 0; 5/99
KIT
ATION
EVALU
E
BL
AVAILA
+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
General Description
Features
o
18-Bit Resolution, Sigma-Delta ADC
o
16-Bit Accuracy with No Missing Codes to 480sps
o
Access to the Mux Output/ADC Input
o
Low Quiescent Current
250µA (operating mode)
2µA (power-down mode)
o
3 Fully Differential or 5 Pseudo-Differential Signal
Input Channels
o
2 Additional Fully Differential Calibration
Channels/Auxiliary Input Channels
o
Programmable Gain and Offset
o
Fully Differential Reference Inputs
o
Converts Continuously or On Command
o
Automatic Channel Scanning and Continuous
Data Output Mode
o
Operates with Analog and Digital Supplies
from +2.7V to +3.6V
o
SPI™/QSPI™-Compatible 3-Wire Serial Interface
o
28-Pin SSOP Package
MAX1401
The MAX1401 18-bit, low-power, multichannel, serial-
output ADC uses a sigma-delta modulator with a digital
decimation filter to achieve true 16-bit accuracy. The
user-selectable decimation factor of the digital filter
allows the conversion resolution to be reduced in
exchange for a higher output data rate. The device
achieves true 16-bit performance at an output data rate of
up to 480sps. In addition, the modulator sampling
frequency may be optimized for either lowest power
dissipation or highest throughput rate. The MAX1401
operates from +3V.
This device offers three fully differential input channels
that can be independently programmed with a gain
between +1V/V and +128V/V. Furthermore, it can com-
pensate an input-referred DC offset (such as system off-
set) up to 117% of the selected full-scale range. These
three differential channels may also be configured to
operate as five pseudo-differential input channels. Two
additional, fully differential system-calibration channels
are provided for gain and offset error correction. External
access is provided to the multiplexer (mux) output to
facilitate additional signal processing.
The MAX1401 can be configured to sequentially scan all
signal inputs and provide the results through the serial
interface with minimum communications overhead. When
used with a 2.4576MHz or 1.024MHz master clock, the
digital decimation filter can be programmed to produce
zeros in its frequency response at the line frequency
and associated harmonics, ensuring excellent line rejec-
tion without the need for further postfiltering.
The MAX1401 is available in a 28-pin SSOP package.
Pin Configuration
TOP VIEW
CLKIN 1
CLKOUT 2
CS 3
RESET 4
MUXOUT+ 5
MUXOUT- 6
ADCIN+ 7
28 SCLK
27 DIN
26 DOUT
25 INT
24 V
DD
Applications
Portable Industrial Instruments
Portable Weigh Scales
Loop-Powered Systems
Pressure Transducers
MAX1401
23 DGND
22 CALOFF+
21 CALOFF-
20 REFIN+
19 REFIN-
18 CALGAIN+
17 CALGAIN-
16 AIN6
15 AIN5
Ordering Information
PART
MAX1401CAI
MAX1401EAI
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
ADCIN- 8
AGND 9
V+ 10
AIN1 11
AIN2 12
AIN3 13
AIN4 14
SPI and QSPI are trademarks of Motorola, Inc.
SSOP
1
________________________________________________________________
Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
MAX1401
ABSOLUTE MAXIMUM RATINGS
V+ to AGND, DGND .................................................-0.3V to +6V
V
DD
to AGND, DGND ...............................................-0.3V to +6V
AGND to DGND.....................................................-0.3V to +0.3V
Analog Inputs to AGND................................-0.3V to (V+ + 0.3V)
Analog Outputs to AGND .............................-0.3V to (V+ + 0.3V)
Reference Inputs to AGND...........................-0.3V to (V+ + 0.3V)
CLKIN and CLKOUT to DGND...................-0.3V to (V
DD
+ 0.3V)
All Other Digital Inputs to DGND..............................-0.3V to +6V
All Digital Outputs to DGND .......................-0.3V to (V
DD
+ 0.3V)
Maximum Current Input into Any Pin ..................................50mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin SSOP (derate 9.52mW/°C above +70°C) ........524mW
Operating Temperature Ranges
MAX1401CAI .....................................................0°C to +70°C
MAX1401EAI...................................................-40°C to +85°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°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.
ELECTRICAL CHARACTERISTICS
(V+ = +2.7V to +3.6V, V
DD
= +2.7V to +3.6V, V
REFIN+
= +1.25V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless
otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
STATIC PERFORMANCE
Noise-Free Resolution
Output Noise
Integral Nonlinearity
(Notes 1, 2)
Nominal Gain (Note 3)
Unipolar Offset Error
Unipolar Offset Drift
Bipolar Zero Error
Bipolar Zero Drift
Positive Full-Scale Error
(Note 4)
Full-Scale Drift (Note 5)
Gain Error (Note 6)
Gain-Error Drift (Note 7)
Bipolar Negative Full-Scale Error
Bipolar Negative Full-Scale Drift
For gains of 1, 2, 4
For gains of 8, 16, 32, 64, 128
For gains of 1, 2, 4, 8, 16, 32, 64
For gain of 128
For gains of 1, 2, 4
For gains of 8, 16, 32, 64, 128
For gains of 1, 2, 4, 8, 16, 32, 64
For gain of 128
For gains of 1, 2, 4, 8, 16, 32, 64
For gain of 128
For gains of 1, 2, 4, 8, 16, 32, 64
For gain of 128
For gains of 1, 2, 4
For gains of 8, 16, 32, 64, 128
-2.5
-3.5
0.8
0.3
-2
-3
1
5
2.5
3.5
-2.5
-3.5
0.8
0.3
2
3
Relative to nominal offset of 1% FSR
For gains of 1, 2, 4
For gains of 8, 16, 32, 64, 128
-2.0
0.8
0.3
2.5
3.5
-1
0.5
0.3
2.0
INL
No missing codes guaranteed by design;
for filter settings with FS1 = 0
Depends on filter setting and selected gain
Bipolar mode; FS1 = 0; MF1, MF0 = 0
FS1 = 0; MF1, MF0 = 1, 2, 3
-0.0015
±0.001
0.98
2
%FSR
µV/°C
%FSR
µV/°C
%FSR
µV/°C
%FSR
ppm/°C
%FSR
µV/°C
16
(Table 16)
0.0015
%FSR
Bits
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +2.7V to +3.6V, V
DD
= +2.7V to +3.6V, V
REFIN+
= +1.25V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless
otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
OFFSET DAC
Offset DAC Range (Note 8)
Offset DAC Resolution
Offset DAC Full-Scale Error
Offset DAC Zero-Scale Error
Additional Noise from Offset
DAC (Note 9)
DAC code = 0000
Unipolar mode
Bipolar mode
Unipolar mode
Bipolar mode
Input referred
-2.5
0
0
-116.7
-58.35
16.7
8.35
2.5
116.7
58.35
%FSR
%FSR
%FSR
%FSR
µV
RMS
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1401
ANALOG INPUTS/REFERENCE INPUTS
(Specifications for AIN and REFIN, unless otherwise noted.)
At DC
Common-Mode Rejection
CMR
For filter notch 50Hz, ±0.02
·
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz (Note 10)
For filter notch 60Hz, ±0.02
·
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz (Note 10)
Normal-Mode 50Hz Rejection
(Note 10)
Normal-Mode 60Hz Rejection
(Note 10)
Common-Mode Voltage Range
(Note 11)
Absolute Input Voltage Range
Absolute and Common-Mode
AIN Voltage Range
DC Input Leakage Current
(Note 12)
AIN Input Current (Note 12)
NMR
NMR
For filter notch 50Hz, ±0.02
·
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz
For filter notch 60Hz, ±0.02
·
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz
REFIN and AIN for BUFF = 0
REFIN and AIN for BUFF = 0
BUFF = 1
REFIN and AIN for
BUFF = 0
BUFF = 1
Gain = 1
AIN Input Capacitance
(Note 13)
BUFF = 0
Gain = 2
Gain = 4
Gain = 8, 16, 32, 64, 128
BUFF = 1, all gains
AIN Differential Voltage Range
(Note 14)
Unipolar input range (U/B bit = 1)
Bipolar input range (U/B
bit = 0)
34
38
45
60
30
0 to V
REF
/ gain
±V
REF
/ gain
V
pF
T
A
= +25°C
T
A
= T
MIN
to T
MAX
90
150
150
100
100
V
AGND
V
AGND
- 30mV
V
AGND
+ 200mV
40
10
10
V+
V+
+ 30mV
V+
- 1.5
dB
dB
V
V
V
pA
nA
nA
dB
________________________________________________________________________________________
3
+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
MAX1401
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +2.7V to +3.6V, V
DD
= +2.7V to +3.6V, V
REFIN+
= +1.25V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless
otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
AIN and REFIN Input Sampling
Frequency
REFIN+ - REFIN- Voltage
(Note 15)
LOGIC INPUTS
Input Current
Input Low Voltage
Input High Voltage
Input Hysteresis
LOGIC OUTPUTS
Output Low Voltage (Note 16)
Output High Voltage (Note 16)
Floating-State Leakage Current
Floating-State Output
Capacitance
Current
Initial Tolerance
Drift
POWER REQUIREMENTS
V+ Voltage
V
DD
Voltage
Power-Supply Rejection V+
(Note 18)
V+
V
DD
PSR
For specified performance
2.7
2.7
(Note 19)
3.6
3.6
V
V
dB
V
OL
V
OH
I
L
C
O
DOUT and
INT,
I
SINK
= 100µA
CLKOUT, I
SINK
= 10µA
DOUT and
INT,
I
SOURCE
= 100µA
CLKOUT, I
SOURCE
= 10µA
V
DD
- 0.3
V
DD
- 0.3
-10
9
10
0.4
0.4
V
V
µA
pF
I
IN
V
IL
V
IH
V
HYS
All inputs except CLKIN
CLKIN only
All inputs except CLKIN
CLKIN only
All inputs except CLKIN
2
2.4
200
-10
+10
0.4
0.4
µA
V
V
mV
SYMBOL
f
S
±5% for specified performance; functional
with lower V
REF
CONDITIONS
MIN
TYP
(Table 15)
1.25
MAX
UNITS
Hz
V
TRANSDUCER BURN-OUT
(Note 17)
I
BO
0.1
±10
±0.05
µA
%
%/°C
4
_______________________________________________________________________________________
+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +2.7V to +3.6V, V
DD
= +2.7V to +3.6V, V
REFIN+
= +1.25V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless
otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1401
ANALOG POWER-SUPPLY CURRENT
(Measured with digital inputs at either DGND or V
DD
, external CLKIN, burn-out currents
disabled, X2CLK = 0, CLK = 0 for 1.024MHz, CLK = 1 for 2.4576MHz.)
V+ Standby Current (Note 20)
PD bit = 1, external clock stopped
Normal mode,
MF1 = 0,
MF0 = 0
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
Buffers off
Buffers on
1
175
370
250
610
245
610
0.42
1.2
0.42
1.2
1.8
4.8
1.8
4.8
1.8
4.8
2.2
6
2.2
6
mA
0.55
1.5
10
210
420
300
700
µA
µA
2X mode,
MF1 = 0,
MF0 = 1
V+ Current
I
V+
4X mode,
MF1 = 1,
MF0 = 0
8X mode,
MF1 = 1,
MF0 = 1
DIGITAL POWER-SUPPLY CURRENT
(Measured with digital inputs at either DGND or V
DD
, external CLKIN, burn-out currents
disabled, X2CLK = 0, CLK = 0 for 1.024MHz, CLK = 1 for 2.4576MHz.)
V
DD
Standby Current (Note 20)
PD bit = 1, external clock stopped
Normal mode,
MF1 = 0, MF0 = 0
2X mode,
MF1 = 0, MF0 = 1
Digital Supply Current
I
DD
4X mode,
MF1 = 1, MF0 = 0
8X mode,
MF1 = 1, MF0 = 1
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
1
70
150
0.08
0.17
0.11
0.22
0.15
0.32
0.50
0.40
0.35
mA
10
200
300
µA
µA
_______________________________________________________________________________________
5

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