MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
________________________________________________________________ Maxim Integrated Products
1
19-1430; Rev 1; 7/02
General Description
The MAX1400 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 MAX1400
operates from +5V.
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 MAX1400 can be configured to scan all signal inputs
sequentially 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 fre-
quency and associated harmonics, ensuring excellent
line rejection without the need for further post-filtering.
The MAX1400 comes in a 28-pin SSOP package.
Applications
Portable Industrial Instruments
Portable Weigh Scales
Loop-Powered Systems
Pressure Transducers
Features
o 18-Bit Resolution, Sigma-Delta ADC
o 16-Bit Performance with No Missing Codes
to 480sps
o Low Quiescent Current
250A (operating mode)
2A (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 Access to the Mux Output/ADC Input
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 +5V Analog Supply and
+3V or +5V Digital Supply
o SPITM/QSPITM-Compatible 3-Wire Serial Interface
o 28-Pin SSOP Package
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
SCLK
DIN
DOUT
INT
V
DD
DGND
AIN5
CALOFF+
CALOFF-
REFIN+
REFIN-
CALGAIN+
CALGAIN-
AIN6
AIN4
AIN3
AIN2
AIN1
V+
AGND
ADCIN-
ADCIN+
MUXOUT-
MUXOUT+
RESET
CS
CLKOUT
CLKIN
SSOP
TOP VIEW
MAX1400
SPI and QSPI are trademarks of Motorola, Inc.
Pin Configuration
Ordering Information
PART
MAX1400CAI
MAX1400EAI
-40C to +85C
0C to +70C
TEMP RANGE
PIN-PACKAGE
28 SSOP
28 SSOP
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V+ = +5V 5%, V
DD
= +2.7V to +5.25V, V
REFIN+
= +2.50V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless other-
wise noted. Typical values are at T
A
= +25C.)
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+ 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
= +70C)
28-Pin SSOP (derate 9.52mW/C above +70C) ........524mW
Operating Temperature Ranges
MAX1400CAI .....................................................0C to +70C
MAX1400EAI...................................................-40C to +85C
Storage Temperature Range .............................-60C to +150C
Lead Temperature (soldering, 10s) .................................+300C
Bipolar Negative Full-Scale Drift
0.3
V/C
For gains of 8, 16, 32, 64, 128
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
Unipolar Offset Error
-1
+2
%FSR
Nominal Gain
0.98
Integral Nonlinearity
INL
-0.0015
0.0015
%FSR
Output Noise
Table 16
0.5
Unipolar Offset Drift
0.3
V/C
Bipolar Zero Error
-2.0
+2.0
%FSR
0.8
Noise-Free Resolution
16
Bits
Bipolar Zero Drift
0.3
Positive Full-Scale Error
(Note 2)
-2.5
+2.5
%FSR
Full-Scale Drift (Note 3)
0.8
0.3
V/C
-2
+2
Gain Error (Note 4)
-3
+3
%FSR
1
Gain-Error Drift (Note 5)
5
ppm/C
-2.5
+2.5
%FSR
0.8
CONDITIONS
For gains of 8, 16, 32, 64, 128
Relative to nominal offset of 1% FSR
For gains of 1, 2, 4, 8, 16, 32, 64
(Note 1)
Bipolar mode, filter settings with FS1 = 0
Depends on filter setting and selected gain
For gains of 1, 2, 4
For gains of 8, 16, 32, 64, 128
For gains of 1, 2, 4
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
No missing codes guaranteed by design;
for filter settings with FS1 = 0
For gains of 1, 2, 4
V/C
For gain of 128
-3.5
+3.5
Bipolar Negative Full-Scale Error
-3.5
+3.5
For gain of 128
STATIC PERFORMANCE
Normal Mode 60Hz Rejection
NMR
100
dB
For filter notch 60Hz, 0.02
f
NOTCH
,
MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
________________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +5V 5%, V
DD
= +2.7V to +5.25V, V
REFIN+
= +2.50V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless other-
wise noted. Typical values are at T
A
= +25C.)
Unipolar mode
CONDITIONS
-116.7
+116.7
Bipolar mode
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
%FSR
-58.35
+58.35
Offset DAC Range (Note 6)
-2.5
+2.5
For filter notch 50Hz, 0.02
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz (Note 8)
DAC code = 0000 (Note 7)
For filter notch 50Hz, 0.02
fNOTCH,
MF1 = 0, MF0 = 0, fCLKIN = 2.4576MHz
(Note 8)
150
dB
100
NMR
Normal Mode 50Hz Rejection
At DC
V
RMS
0
Additional Noise from Offset
DAC
90
REFIN and AIN for BUFF = 0 (Note 9)
V
V
AGND
V+
Common-Mode Voltage Range
BUFF = 1
BUFF = 1 (Note 10)
10
AIN Input Current
nA
V
V
AGND
V+
+ 200mV
- 1.5
Absolute and Common-Mode
AIN Voltage Range
pA
40
DC Input Leakage Current
(Note 10)
Unipolar mode
16.7
Bipolar mode
%FSR
8.35
Offset DAC Resolution
For filter notch 60Hz, 0.02
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz (Note 8)
dB
150
CMR
Common-Mode Rejection
For filter notch 60Hz, 0.02
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz
(Note 8)
dB
100
NMR
Normal Mode 60Hz Rejection
REFIN and AIN for BUFF = 0
V
V
AGND
V+
- 30mV
+ 30mV
Absolute Voltage Range Input
REFIN and AIN for
BUFF = 0
T
A
= +25C
T
A
= T
MIN
to T
MAX
10
nA
34
38
45
BUFF = 0
60
BUFF = 1, all gains
30
AIN Input Capacitance
(Note 11)
pF
Bipolar input range (U/B bit = 0)
V
REF
/
gain
AIN Differential Voltage Range
(Note 12)
V
Gain = 1
Gain = 2
Gain = 4
Gain = 8, 16, 32, 64, 128
Unipolar input range (U/B bit = 1)
0 to V
REF
/
gain
%FSR
0
Offset DAC Zero-Scale Error
Input referred
%FSR
-3.5
+3.5
Offset DAC Full-Scale Error
Gain = 1, 2, 4, 8, 16, 32, 64
Gain = 128
OFFSET DAC
ANALOG INPUTS/REFERENCE INPUTS (Specifications for AIN and REFIN, unless otherwise noted.)
Power-Supply Rejection V+
(Note 16)
dB
PSR
MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +5V 5%, V
DD
= +2.7V to +5.25V, V
REFIN+
= +2.50V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless other-
wise noted. Typical values are at T
A
= +25C.)
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
0.8
0.8
All inputs except
CLKIN
0.4
A
-10
+10
I
IN
Input Current
200
CLKIN only
All inputs except
CLKIN
mV
200
V
HYS
Input Hysteresis
DOUT
and INT
0.4
pF
9
C
O
Floating State Output
Capacitance
A
-10
+10
I
L
Floating State Leakage Current
V
0.4
V
IL
Input Low Voltage
5% for specified performance; functional with
lower V
REF
(Note 13)
V
2.50
REFIN+ - REFIN- Voltage
V
DD
= 5V
V
DD
= 3.3V
V
DD
= 5V
V
DD
= 3.3V
V
DD
= 5V
V
DD
= 3.3V
V
DD
= 5V
V
DD
= 3.3V
2
3.5
All inputs except
CLKIN
2
CLKIN only
V
2.4
V
IH
Input High Voltage
V
DD
= 5V
V
DD
= 3.3V
A
0.1
I
BO
Current
%
10
Initial Tolerance
%/C
0.05
Drift
Hz
(Table 15)
f
S
AIN and REFIN Input Sampling
Frequency
CLKOUT
V
0.4
V
OL
Output Low Voltage (Note 14)
V
DD
= 5V, I
SINK
= 800A
V
DD
= 3.3V, I
SINK
= 100A
V
DD
= 5V, I
SINK
= 10A
V
DD
= 3.3V, I
SINK
= 10A
CLKOUT
V
V
DD
- 0.3
V
OH
Output High Voltage (Note 14)
4
V
DD
= 5V, I
SOURCE
= 200A
V
DD
= 3.3V, I
SOURCE
= 100A
V
DD
= 5V, I
SOURCE
= 10A
DOUT
and INT
V
DD
- 0.3
4
V
DD
= 3.3V, I
SOURCE
= 10A
For specified performance
V
4.75
5.25
V+
V+ Voltage
V
2.7
5.25
V
DD
V
DD
Voltage
(Note 16)
dB
(Note 17)
PSR
Power-Supply Rejection V+
TRANSDUCER BURN-OUT (Note 15)
LOGIC OUTPUTS
LOGIC INPUTS
POWER REQUIREMENTS
MAX1400
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
_______________________________________________________________________________________
5
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +5V 5%, V
DD
= +2.7V to +5.25V, V
REFIN+
= +2.50V, REFIN- = AGND, f
CLKIN
= 2.4576MHz, T
A
= T
MIN
to T
MAX
, unless other-
wise noted. Typical values are at T
A
= +25C.)
2.4576MHz
1.024MHz
Buffers off
Buffers off
Buffers on
2.4576MHz
1.024MHz
370
420
Buffers off
Buffers off
Buffers on
Normal mode,
MF1 = 0,
MF0 = 0
610
700
250
300
Buffers on
610
Buffers on
2X mode,
MF1 = 0,
MF0 = 1
1.2
1.5
CONDITIONS
PD bit = 1, external clock stopped (Note 18)
0.42
0.55
245
2.4576MHz
1.024MHz
Buffers off
Buffers off
Buffers on
2.4576MHz
1.024MHz
1.2
Buffers off
Buffers off
Buffers on
4X mode,
MF1 = 1,
MF0 = 0
A
4.8
6
1
10
1.8
2.2
Buffers on
4.8
Buffers on
8X mode,
MF1 = 1,
MF0 = 1
mA
4.8
6
I
V+
V+ Current
1.8
2.2
1.8
0.42
V+ Standby Current
0.08
70
200
2X mode,
MF1 = 0, MF0 = 1
0.17
0.35
0.13
Normal mode,
MF1 = 0, MF0 = 0
PD bit = 1, external clock stopped (Note 18)
1
10
150
300
A
V
DD
Standby Current
A
150
300
2X mode,
MF1 = 0, MF0 = 1
1.024MHz
2.4576MHz
0.28
0.50
Normal mode,
MF1 = 0, MF0 = 0
1.024MHz
175
210
2.4576MHz
0.15
0.11
8X mode,
MF1 = 1, MF0 = 1
0.32
0.45
mA
4X mode,
MF1 = 1, MF0 = 0
0.22
0.40
235
450
A
1.024MHz
1.024MHz
2.4576MHz
I
DD
3.3V Digital Supply Current
1.024MHz
2.4576MHz
2.4576MHz
1.024MHz
2.4576MHz
0.24
0.17
8X mode,
MF1 = 1, MF0 = 1
0.53
0.80
mA
4X mode,
MF1 = 1, MF0 = 0
0.36
0.60
1.024MHz
2.4576MHz
I
DD
5V Digital Supply Current
1.024MHz
2.4576MHz
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
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.)
DIGITAL POWER-SUPPLY CURRENT (Measured with digital inputs at either DGND or V
DD
, external MCLKIN, burn-out currents
disabled, X2CLK = 0, CLK = 0 for 1.024MHz, CLK = 1 for 2.4576MHz.)
A
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