MAX189BEWE ,+5V, Low-Power, 12-Bit Serial ADCsapplications, or for circuits where powerMAX187BCWE 0°C to +70°C 16 Wide SO ±1consumption and space ..
MAX189CCPA ,+5V, Low-Power, 12-Bit Serial ADCsFeaturesThe MAX187/MAX189 serial 12-bit analog-to-digital ' 12-Bit Resolution1converters (ADCs) ope ..
MAX189CCWE ,+5V, Low-Power, 12-Bit Serial ADCsMAX187/MAX18919-0196; Rev 0; 10/93+5V, Low-Power, 12-Bit Serial ADCs__________________
MAX189CEWE ,+5V, Low-Power, 12-Bit Serial ADCsFeaturesThe MAX187/MAX189 serial 12-bit analog-to-digital ' 12-Bit Resolution1converters (ADCs) ope ..
MAX189CEWE+ ,+5V, Low-Power, 12-Bit Serial ADCsapplications, or for circuits where powerMAX187BCWE 0°C to +70°C 16 Wide SO ±1consumption and space ..
MAX1901EAI ,500kHz Multi-Output / Low-Noise Power-Supply Controllers for Notebook Computersfeatures.Functional Diagram____
MAX485CSA ,Low-Power / Slew-Rate-Limited RS-485/RS-422 TransceiversMAX481/MAX483/MAX485/MAX487–MAX491/MAX148719-0122; Rev 5; 2/96Low-Power, Slew-Rate-LimitedRS-485/RS ..
MAX485CSA+ ,Low-Power, Slew-Rate-Limited RS-485/RS-422 TransceiversApplicationsMAX1487 are low-power transceivers for RS-485 and RS-MAX3430: ±80V Fault-Protected, Fai ..
MAX485CSA+T ,Low-Power, Slew-Rate-Limited RS-485/RS-422 TransceiversApplicationsMAX3483E/MAX3485E/MAX3486E/MAX3488E/Low-Power RS-485 TransceiversMAX3490E/MAX3491E: +3. ..
MAX485CSA-T ,Low-Power, Slew-Rate-Limited RS-485/RS-422 TransceiversApplicationsIndustrial-Control Local Area Networks Ordering Information appears at end of data shee ..
MAX485E ,±15kV ESD-Protected, Slew-Rate Limited, Low-Power, RS-485/RS-422 TransceiversApplicationsPART TEMP RANGE PIN-PACKAGELow-Power RS-485 TransceiversMAX481ECPA 0°C to +70°C 8 Plast ..
MAX485ECPA ,15kV ESD-Protected / Slew-Rate-Limited / Low-Power / RS-485/RS-422 TransceiversMAX481E/MAX483E/MAX485E/MAX487E–MAX491E/MAX1487E19-0410; Rev 3; 7/96±15kV ESD-Protected, Slew-Rate- ..
MAX187ACWE-MAX187AEWE-MAX187BCPA-MAX187BCWE-MAX187BEPA-MAX187BEWE-MAX187CCPA-MAX187CCWE-MAX187CEWE-MAX189ACPA-MAX189ACWE-MAX189AEWE-MAX189BCPA-MAX189BCWE-MAX189BEWE-MAX189CCPA-MAX189CCWE-MAX189CEWE
+5V, Low-Power, 12-Bit Serial ADCs
__________________General DescriptionThe MAX187/MAX189 serial 12-bit analog-to-digital
converters (ADCs) operate from a single +5V supply
and accept a 0V to 5V analog input. Both parts feature
an 8.5µs successive-approximation ADC, a fast
track/hold (1.5µs), an on-chip clock, and a high-speed
3-wire serial interface.
The MAX187/MAX189 digitize signals at a 75ksps
throughput rate. An external clock accesses data from
the interface, which communicates without external
hardware to most digital signal processors and micro-
controllers. The interface is compatible with SPI™,
QSPI™, and Microwire™.
The MAX187 has an on-chip buffered reference, and
the MAX189 requires an external reference. Both the
MAX187 and MAX189 save space with 8-pin DIP and
16-pin SO packages. Power consumption is 7.5mW
and reduces to only 10µW in shutdown.
Excellent AC characteristics and very low power con-
sumption combined with ease of use and small pack-
age size make these converters ideal for remote DSP
and sensor applications, or for circuits where power
consumption and space are crucial.
___________________________ApplicationsPortable Data Logging
Remote Digital Signal Processing
Isolated Data Acquisition
High-Accuracy Process Control
________________________________Features12-Bit Resolution±1⁄2LSB Integral Nonlinearity (MAX187A/MAX189A)Internal Track/Hold, 75kHz Sampling RateSingle +5V OperationLow Power: 2µA Shutdown Current
1.5mA Operating CurrentInternal 4.096V Buffered Reference (MAX187)3-Wire Serial Interface, Compatible with SPI,
QSPI, and MicrowireSmall-Footprint 8-Pin DIP and 16-Pin SO
_________________Ordering Information
MAX1
87/MAX189, Low-Power, 12-Bit Serial ADCs
________________________________________________________________Maxim Integrated Products1
Call toll free 1-800-998-8800 for free samples or literature.SPI and QSPI are trademarks of Motorola. Microwire is a trademark of National Semiconductor.
Ordering Information continued on last page.* Dice are specified at TA=+25°C, DC parameters only.
** Contact factory for availability and processing to MIL-STD-883.
________________Functional Diagram
_________________Pin Configurations
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS(VDD= +5V ±5%; GND = 0V; unipolar input mode; 75ksps, fCLK= 4.0MHz, external clock (50% duty cycle); MAX187—internal
reference: VREF= 4.096V, 4.7µF capacitor at REF pin, or MAX189—external reference: VREF= 4.096V applied to REF pin, 4.7µF
capacitor at REF pin; TA= TMINto TMAX; unless otherwise noted.)
VDDto GND.............................................................-0.3V to +6V
AIN to GND................................................-0.3V to (VDD + 0.3V)
REF to GND...............................................-0.3V to (VDD + 0.3V)
Digital Inputs to GND.................................-0.3V to (VDD + 0.3V)
Digital Outputs to GND..............................-0.3V to (VDD + 0.3V)
SHDNto GND.............................................-0.3V to (VDD + 0.3V)
REF Load Current (MAX187).........................4.0mA Continuous
REF Short-Circuit Duration (MAX187)................................20sec
DOUT Current..................................................................±20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C)..500mW
16-Pin Wide SO (derate 8.70mW/°C above +70°C)...478mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)......440mW
Operating Temperature Ranges:
MAX187_C_ _/MAX189_C_ _.............................0°C to +70°C
MAX187_E_ _/MAX189_E_ _..........................-40°C to +85°C
MAX187_MJA/MAX189_MJA.......................-55°C to +125°C
Storage Temperature Range............................-60°C to +150°C
Lead Temperature (soldering, 10sec)............................+300°C
ABSOLUTE MAXIMUM RATINGSStresses 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.
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs
_______________________________________________________________________________________3
ELECTRICAL CHARACTERISTICS (continued)(VDD= +5V ±5%; GND = 0V; unipolar input mode; 75ksps, fCLK= 4.0MHz, external clock (50% duty cycle); MAX187—internal
reference: VREF= 4.096V, 4.7µF capacitor at REF pin, or MAX189—external reference: VREF= 4.096V applied to REF pin, 4.7µF
capacitor at REF pin; TA= TMINto TMAX; unless otherwise noted.)
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)(VDD= +5V ±5%; GND = 0V; unipolar input mode; 75ksps, fCLK= 4.0MHz, external clock (50% duty cycle); MAX187—internal
reference: VREF= 4.096V, 4.7µF capacitor at REF pin, or MAX189—external reference: VREF= 4.096V applied to REF pin, 4.7µF
capacitor at REF pin; TA= TMINto TMAX; unless otherwise noted.)
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs
_______________________________________________________________________________________5
TIMING CHARACTERISTICS(VDD= +5.0V ±5%, TA= TMINto TMAX, unless otherwise noted.)
Note 1:Tested at VDD= +5V.
Note 2:Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has
been calibrated.
Note 3:MAX187—internal reference, offset nulled; MAX189–external +4.096V reference, offset nulled. Excludes reference errors.
Note 4:Guaranteed by design. Not subject to production testing.
Note 5:External load should not change during conversion for specified ADC accuracy.
Note 6:DC test, measured at 4.75V and 5.25V only.
Note 7:To guarantee acquisition time, tACQis the maximum time the device takes to acquire the signal, and is also the minimum
time needed for the signal to be acquired.
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs_______________________________________________________________________________________TEMPERATURE (°C)
POWER-SUPPLY REJECTION (mV)
POWER-SUPPLY REJECTION vs.
TEMPERATURETEMPERATURE (°C)
INTERNAL REFERENCE VOLTAGE (V)
VREF vs. TEMPERATURETEMPERATURE (°C)
SUPPLY CURRENT (mA)
SUPPLY CURRENT vs. TEMPERATURE________________________________________________Typical Operating Characteristics
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (
SHUTDOWN SUPPLY CURRENT vs.
TEMPERATUREMAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs
_______________________________________________________________________________________7
_______________________________________________________________________Pin Description
_______________Detailed Description
Converter OperationThe MAX187/MAX189 use input track/hold (T/H) and
successive approximation register (SAR) circuitry to
convert an analog input signal to a digital 12-bit output.
No external hold capacitor is needed for the T/H.
Figures 3a and 3b show the MAX187/MAX189 in their
simplest configuration. The MAX187/MAX189 convert
input signals in the 0V to VREFrange in 10µs, including
T/H acquisition time. The MAX187’s internal reference
is trimmed to 4.096V, while the MAX189 requires an
external reference. Both devices accept external refer-
ence voltages from +2.5V to VDD. The serial interface
requires only three digital lines, SCLK, CS,and DOUT,
and provides easy interface to microprocessors (mPs).
Both converters have two modes: normal and shut-
down. Pulling SHDNlow shuts the device down and
reduces supply current to below 10µA, while pulling
SHDNhigh or leaving it floating puts the device into the
operational mode. A conversion is initiated by CS
falling. The conversion result is available at DOUT in
unipolar serial format. A high bit, signaling the end of
conversion (EOC), followed by the data bits (MSB first),
make up the serial data stream.
The MAX187 operates in one of two states: (1) internal
reference and (2) external reference. Select internal
reference operation by forcing SHDNhigh, and external
reference operation by floating SHDN.
Analog InputFigure 4 illustrates the sampling architecture of the
ADC’s analog comparator. The full-scale input voltage
depends on the voltage at REF.
For specified accuracy, the external reference voltage
range spans from +2.5V to VDD.
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs_______________________________________________________________________________________Figure 1. Load Circuits for DOUT Enable Time
Figure 2. Load Circuits for DOUT Disable Time
Track/HoldIn track mode, the analog signal is acquired and stored
in the internal hold capacitor. In hold mode, the T/H
switch opens and maintains a constant input to the
ADC’s SAR section.
During acquisition, the analog input AIN charges
capacitor CHOLD. Bringing CSlow ends the acquisition
interval. At this instant, the T/H switches the input side
of CHOLDto GND. The retained charge on CHOLDrep-
resents a sample of the input, unbalancing the node
ZERO at the comparator’s input.
In hold mode, the capacitive DAC adjusts during the
remainder of the conversion cycle to restore node
ZERO to 0V within the limits of a 12-bit resolution. This
action is equivalent to transferring a charge from
CHOLDto the binary-weighted capacitive DAC, which in
turn forms a digital representation of the analog input
signal. At the conversion’s end, the input side of CHOLD
switches back to AIN, and CHOLDcharges to the input
signal again.
The time required for the T/H to acquire an input signal
is a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is
high, the acquisition time lengthens and more time
must be allowed between conversions. Acquisition time
is calculated by:
tACQ= 9 (RS+ RIN) 16pF,
where RIN= 5kΩ, RS= the source impedance of the
input signal, and tACQis never less than 1.5µs. Source
impedances below 5kΩdo not significantly affect the
AC performance of the ADC.
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs
_______________________________________________________________________________________9Figure 3a. MAX187 Operational DiagramFigure 3b. MAX189 Operational Diagram
MAX1
87/MAX189
+5V, Low-Power, 12-Bit Serial ADCs______________________________________________________________________________________
Input BandwidthThe ADCs’ input tracking circuitry has a 4.5MHz small-
signal bandwidth, and an 8V/µs slew rate. It is possible
to digitize high-speed transient events and measure
periodic signals with bandwidths exceeding the ADC's
sampling rate by using undersampling techniques. To
avoid aliasing of unwanted high-frequency signals into
the frequency band of interest, an anti-alias filter is rec-
ommended. See the MAX274/MAX275 continuous-time
filters data sheet.
Input ProtectionInternal protection diodes that clamp the analog input
allow the input to swing from GND - 0.3V to VDD+ 0.3V
without damage. However, for accurate conversions
near full scale, the input must not exceed VDDby more
than 50mV, or be lower than GND by 50mV.
If the analog input exceeds the supplies by more than
50mV beyond the supplies,limit the input current to
2mA, since larger currents degrade conversion
accuracy.
Driving the Analog Input The input lines to AIN and GND should be kept as short
as possible to minimize noise pickup. Shield longer
leads. Also see the Input Protection section.
Because the MAX187/MAX189 incorporate a T/H, the
drive requirements of the op amp driving AIN are less
stringent than those for a successive-approximation
ADC without a T/H. The typical input capacitance is
16pF. The amplifier bandwidth should be sufficient to
handle the frequency of the input signal. The MAX400
and OP07 work well at lower frequencies. For higher-
frequency operation, the MAX427 and OP27 are practi-
cal choices. The allowed input frequency range is limit-
ed by the 75ksps sample rate of the MAX187/MAX189.
Therefore, the maximum sinusoidal input frequency
allowed is 37.5kHz. Higher-frequency signals cause
aliasing problems unless undersampling techniques
are used.
ReferenceThe MAX187 can be used with an internal or external ref-
erence, while the MAX189 requires an external reference.
Internal ReferenceThe MAX187 has an on-chip reference with a buffered
temperature-compensated bandgap diode, laser-
trimmed to +4.096V ±0.5%. Its output is connected to
REF and also drives the internal DAC. The output can
be used as a reference voltage source for other com-
ponents and can source up to 0.6mA. Decouple REF
with a 4.7µF capacitor. The internal reference is
enabled by pulling the SHDNpin high. Letting SHDN
float disables the internal reference, which allows the
use of an external reference, as described in the
External Referencesection.
External ReferenceThe MAX189 operates with an external reference at the
REF pin. To use the MAX187 with an external reference,
disable the internal reference by letting SHDNfloat. Stay
within the voltage range +2.5V to VDDto achieve speci-
fied accuracy. The minimum input impedance is 12kΩ
for DC currents. During conversion, the external refer-
ence must be able to deliver up to 350µA DC load cur-
rent and have an output impedance of 10Ωor less. The
recommended minimum value for the bypass capacitor
is 0.1µF. If the reference has higher output impedance
or is noisy, bypass it close to the REF pin with a 4.7µF
capacitor.
Figure 5. MAX187/MAX189 Shutdown Sequence
