19-1430; Rev 1; 7/02
+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
General Description
Features
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.
o 18-Bit Resolution, Sigma-Delta ADC
o 16-Bit Performance with No Missing Codes
to 480sps
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
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.
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
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.
o SPI™/QSPI™-Compatible 3-Wire Serial Interface
o 28-Pin SSOP Package
Pin Configuration
TOP VIEW
The MAX1400 comes in a 28-pin SSOP package.
CLKIN
CLKOUT
CS
1
2
3
4
5
6
7
8
9
28 SCLK
27 DIN
Applications
Portable Industrial Instruments
Portable Weigh Scales
26 DOUT
25 INT
RESET
MUXOUT+
MUXOUT-
ADCIN+
ADCIN-
AGND
24 V
DD
Loop-Powered Systems
MAX1400
23 DGND
Pressure Transducers
22 CALOFF+
21 CALOFF-
20 REFIN+
19 REFIN-
18 CALGAIN+
17 CALGAIN-
16 AIN6
Ordering Information
V+ 10
AIN1 11
AIN2 12
AIN3 13
AIN4 14
PART
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
MAX1400CAI
MAX1400EAI
28 SSOP
15 AIN5
SSOP
SPI and QSPI are trademarks of Motorola, Inc.
________________________________________________________________ Maxim Integrated Products
1
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.