19-1423; Rev 0; 3/99
KIT
ATION
EVALU
BLE
AVAILA
+5V, 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
Low Quiescent Current
250µA (operating mode)
2µA (power-down mode)
o
Matched On-Board Current Sources (200µA) for
Sensor Excitation
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 +5V Analog Supply and +3V or +5V
Digital Supply
o
3-Wire Serial Interface—SPI™/QSPI™ Compatible
o
28-Pin SSOP Package
MAX1402
The MAX1402 low-power, multichannel, serial-output
analog-to-digital converter (ADC) features matched
200µA current sources for sensor excitation. This ADC
uses a sigma-delta modulator with a digital decimation
filter to achieve 16-bit accuracy. The digital filter’s user-
selectable decimation factor allows the conversion res-
olution to be reduced in exchange for a higher output
data rate. True 16-bit performance is achieved at an
output data rate of up to 480sps. In addition, the modu-
lator sampling frequency may be optimized for either
lowest power dissipation or highest throughput rate.
The MAX1402 operates from a +5V supply.
This device offers three fully differential input channels
that may be independently programmed with a gain
between +1V/V and +128V/V. Furthermore, it can com-
pensate an input-referred DC offset up to 117% of the
selected full-scale range. These three differential chan-
nels 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.
The MAX1402 may be configured to sequentially scan all
signal inputs and provide the results via the serial inter-
face 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 rejection
without the need for further post-filtering.
The MAX1402 is available in a 28-pin SSOP package.
Pin Configuration
TOP VIEW
CLKIN 1
28 SCLK
27 DIN
26 DOUT
25 INT
24 V
DD
Applications
Portable Industrial Instruments
Portable Weigh Scales
Loop-Powered Systems
Pressure Transducers
CLKOUT 2
CS 3
RESET 4
DS1 5
DS0 6
OUT2 7
OUT1 8
AGND 9
MAX1402
23 DGND
22 CALOFF+
21 CALOFF-
20 REFIN+
19 REFIN-
18 CALGAIN+
17 CALGAIN-
16 AIN6
15 AIN5
Ordering Information
PART
MAX1402CAI
MAX1402EAI
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
V+ 10
AIN1 11
AIN2 12
AIN3 13
AIN4 14
SPI and QSPI are trademarks of Motorola, Inc.
SSOP
________________________________________________________________
Maxim Integrated Products
1
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.
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
MAX1402
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
MAX1402CAI .....................................................0°C to +70°C
MAX1402EAI...................................................-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+ = +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
= +25°C.)
PARAMETER
STATIC PERFORMANCE
Noise-Free Resolution
Output Noise
Integral Nonlinearity
Nominal Gain (Note 1)
Unipolar Offset Error
Unipolar Offset Drift
Bipolar Zero Error
Bipolar Zero Drift
Positive Full-Scale Error
(Note 2)
Full-Scale Drift (Note 3)
Gain Error (Note 4)
Gain-Error Drift (Note 5)
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 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, filter settings with FS1 = 0
-0.0015
0.98
2
%FSR
µV/°C
%FSR
µV/°C
%FSR
µV/°C
%FSR
ppm/°C
%FSR
%FSR
µV/°C
16
Table 16
0.0015
%FSR
Bits
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
MAX1402
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
= +25°C.)
PARAMETER
OFFSET DAC
Offset DAC Range (Note 6)
Offset DAC Resolution
Offset DAC Full-Scale Error
Offset DAC Zero-Scale Error
Additional Noise from Offset
DAC (Note 7)
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
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 8)
For filter notch 60Hz, ±0.02
·
f
NOTCH
,
MF1 = 0, MF0 = 0, f
CLKIN
= 2.4576MHz (Note 8)
Normal Mode 50Hz Rejection
(Note 8)
Normal Mode 60Hz Rejection
(Note 8)
Common-Mode Voltage Range
(Note 9)
Absolute Input Voltage Range
Absolute and Common-Mode
AIN Voltage Range
DC Input Leakage Current
(Note 10)
AIN Input Current (Note 10)
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
(Notes 11)
BUFF = 0
Gain = 2
Gain = 4
Gain = 8, 16, 32, 64, 128
BUFF = 1, all gains
AIN Differential Voltage Range
(Note 12)
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
dB
V
V
pA
nA
nA
dB
_______________________________________________________________________________________
3
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
MAX1402
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
= +25°C.)
PARAMETER
AIN and REFIN Input Sampling
Frequency
REFIN+ - REFIN- Voltage
(Note 13)
LOGIC INPUTS
Input Current
I
IN
All inputs except
CLKIN
Input Low Voltage
V
IL
CLKIN only
All inputs except
CLKIN
Input High Voltage
V
IH
CLKIN only
Input Hysteresis
LOGIC OUTPUTS
DOUT
and
INT
Output Low Voltage (Note 14)
V
OL
CLKOUT
DOUT
and
INT
CLKOUT
Floating-State Leakage Current
Floating-State Output
Capacitance
Current
Initial Tolerance
Drift
TRANSDUCER EXCITATION CURRENTS
Current
Initial Tolerance
Drift
Match
Drift Match
Compliance Voltage Range
V
AGND
OUT1 to OUT2
5
V+ - 1.0
100
±1
I
EXC
200
15
µA
%
ppm/°C
%
ppm/°C
V
I
L
C
O
V
DD
= 5V, I
SINK
= 800µA
V
DD
= 3.3V, I
SINK
= 100µA
V
DD
= 5V, I
SINK
= 10µA
V
DD
= 3.3V, I
SINK
= 10µA
V
DD
= 5V, I
SOURCE
= 200µA
V
DD
= 3.3V, I
SOURCE
= 100µA
V
DD
= 5V, I
SOURCE
= 10µA
V
DD
= 3.3V, I
SOURCE
= 10µA
4
V
DD
- 0.3
4
V
DD
- 0.3
-10
9
V
0.4
V
0.4
V
HYS
All inputs except
CLKIN
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
V
DD
= 5V
V
DD
= 3.3V
2
2
3.5
2.4
200
200
mV
V
-10
+10
0.8
0.4
0.8
0.4
V
µA
SYMBOL
f
S
±5% for specified performance; functional
with lower V
REF
CONDITIONS
MIN
TYP
(Table 15)
2.50
MAX
UNITS
Hz
V
Output High Voltage (Note 14)
V
OH
10
µA
pF
TRANSDUCER BURN-OUT
(Note 15)
I
BO
0.1
±10
±0.05
µA
%
%/°C
4
_______________________________________________________________________________________
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
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
= +25°C.)
PARAMETER
POWER REQUIREMENTS
V+ Voltage
V
DD
Voltage
Power-Supply Rejection V+
(Note 16)
V+
V
DD
PSR
For specified performance
4.75
2.7
(Note 17)
5.25
5.25
V
V
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1402
ANALOG POWER-SUPPLY CURRENT
(Measured with digital inputs at either DGND or V
DD
, external CLKIN, burn-out and auxil-
iary currents disabled, X2CLK = 0, CLK = 0 for 1.024MHz, CLK = 1 for 2.4576MHz.)
V+ Standby Current (Note 18)
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 and auxiliary
currents disabled, X2CLK = 0, CLK = 0 for 1.024MHz, CLK = 1 for 2.4576MHz.)
V
DD
Standby Current (Note 18)
PD bit = 1, external clock stopped
Normal mode,
MF1 = 0, MF0 = 0
2X mode,
MF1 = 0, MF0 = 1
3.3V Digital Supply Current
I
DD
4X mode,
MF1 = 1, MF0 = 0
8X mode,
MF1 = 1, MF0 = 1
Normal mode,
MF1 = 0, MF0 = 0
5V Digital Supply Current
I
DD
2X mode,
MF1 = 0, MF0 = 1
1.024MHz
2.4576MHz
1.024MHz
2.4576MHz
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
115
235
0.13
0.28
0.5
0.45
300
450
µA
mA
0.40
0.35
mA
10
200
300
µA
µA
_______________________________________________________________________________________
5
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