Data Sheet

EVALUATION KIT AVAILABLE
MAX1460
General Description
The MAX1460 implements a revolutionary concept in signal
conditioning, where the output of its 16-bit analog- to-digital
converter (ADC) is digitally corrected over the specified
temperature range. This feature can be readily exploited
by industrial and medical market segments, in applications
such as sensors and smart batteries. Digital correction is
provided by an internal digital signal processor (DSP) and
on-chip 128-bit EEPROM containing user-programmed
calibration coefficients. The conditioned output is available
as a 12-bit digital word and as a ratiometric (proportional
to the supply voltage) analog voltage using an on-board
12-bit digital-to-analog converter (DAC). The uncommitted
op amp can be used to filter the analog output, or implement a 2-wire, 4–20mA transmitter.
The analog front end includes a 2-bit programmablegain
amplifier (PGA) and a 3-bit coarse-offset (CO) DAC,
which condition the sensor’s output. This coarsely corrected signal is digitized by a 16-bit ADC. The DSP uses
the digitized sensor signal, the temperature sensor, and
correction coefficients stored in the internal EEPROM to
produce the conditioned output.
Multiple or batch manufacturing of sensors is supported with a
completely digital test interface. Built-in testability features on
the MAX1460 result in the integration of three traditional sensor-manufacturing operations into one automated process:
●● Pretest: Data acquisition of sensor performance under
the control of a host test computer.
●● Calibration and Compensation: Computation and storage of calibration and compensation coefficients
determined from transducer pretest data.
●● Final Test Operation: Verification of transducer calibration and compensation, without removal from the
pretest socket.
The MAX1460 evaluation kit (EV kit) allows fast evaluation
and prototyping, using a piezoresistive transducer (PRT) and
a Windows®-based PC. The user-friendly EV kit simplifies
small-volume prototyping; it is not necessary to fully understand the test-system interface, the calibration algorithm, or
many other details to evaluate the MAX1460 with a particular
sensor. Simply plug the PRT into the EV kit, plug the EV kit
into a PC parallel port, connect the sensor to an excitation
source (such as a pressure controller), and run the MAX1460
EV kit software. An oven is required for thermal compensation
Functional Diagram appears at end of data sheet.
Pin Configuration appears at end of data sheet.
Windows is a registered trademark of Microsoft Corp.
19-4784; Rev 1; 5/14
Low-Power, 16-Bit Smart ADC
Features
●● Low-Noise, 400μA Single-Chip Sensor Signal
Conditioning
●● High-Precision Front End Resolves Less than 1μV of
Differential Input Signal
●● On-Chip DSP and EEPROM Provide Digital
Correction of Sensor Errors
●● 16-Bit Signal Path Compensates Sensor Offset and
Sensitivity and Associated Temperature Coefficients
●● 12-Bit Parallel Digital Output
●● Analog Output
●● Compensates a Wide Range of Sensor Sensitivity
and Offset
●● Single-Shot Automated Compensation
Algorithm—No Iteration Required
●● Built-In Temperature Sensor
●● Three-State, 5-Wire Serial Interface Supports
High-Volume Manufacturing
Applications
●● Hand-Held Instruments
●● Piezoresistive Pressure and Acceleration
Transducers and Transmitters
●● Industrial Pressure Sensors and 4–20mA
Transmitters
●● Smart Battery Charge Systems
●● Weigh Scales and Strain-Gauge Measurement
●● Flow Meters
●● Dive Computers and Liquid-Level Sensing
●● Hydraulic Systems
Ordering Information
PART
TEMP RANGE
MAX1460CCM
0°C to +70°C
Customization
PIN-PACKAGE
48 TQFP
Maxim can customize the MAX1460 for unique requirements. With a dedicated cell library of more than 90 sensor- specific functional blocks, Maxim can quickly provide
customized MAX1460 solutions, including customized
microcode for unusual sensor characteristics. Contact
Maxim for further information.
MAX1460
Low-Power, 16-Bit Smart ADC
Absolute Maximum Ratings
Supply Voltage, VDD to VSS....................................-0.3V to +6V
All Other Pins................................. (VSS - 0.3V) to (VDD + 0.3V)
Short-Circuit Duration, All Outputs.............................Continuous
Continuous Power Dissipation (TA = +70°C)
48-Pin TQFP (derate 12.5mW/°C above +70°C )......1000mW
Operating Temperature Range................................0°C to +70°C
Storage Temperature Range............................. -65°C to +160°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
(VDD = +5V, VSS = 0, fXIN = 2MHz, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4.75
5.0
5.25
V
400
700
µA
GENERAL CHARACTERISTICS
Supply Voltage (Note 1)
VDD
During operation
Supply Current (Note 2)
IDD
Continuous conversion
Throughput Rate
15
Hz
1.0
MΩ
ANALOG INPUT
Input Impedance
RIN
Gain Temperature Coefficient (TC)
Input-Referred Offset TC
Common-Mode Rejection Ratio
CMRR
From VSS to VDD
±40
ppm/°C
±1200
nV/°C
90
dB
PGA AND COARSE-OFFSET DAC (Notes 3, 4)
PGA Gain
Coarse Offset
PGA gain code = 00
43
46
49
PGA gain code = 01
59
61
64
PGA gain code = 10
74
77
80
PGA gain code = 11
90
93
96
CO-DAC code = 111
-164
-149
-134
CO-DAC code = 110
-111
-96
-81
CO-DAC code = 101
-62
-47
-32
CO-DAC code = 100
-10
5
20
CO-DAC code = 000
-20
-5
10
CO-DAC code = 001
32
47
62
CO-DAC code = 010
81
96
111
CO-DAC code = 011
134
149
164
V/V
% VDD
ADC (Notes 3, 4)
Resolution
Integral Nonlinearity (Note 5)
INL
PGA gain code = 00, CO-DAC code = 000
Input-Referred Noise
Output-Referred Noise
5kΩ input impedance
16
Bits
0.006
%
1700
nVRMS
2
LSBRMS
260
LSB/°C
1.3
°C
TEMPERATURE SENSOR (Note 6)
Resolution
Linearity
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TA = 0°C to +70°C
Maxim Integrated │ 2
MAX1460
Low-Power, 16-Bit Smart ADC
Electrical Characteristics (continued)
(VDD = +5V, VSS = 0, fXIN = 2MHz, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
OUTPUT DAC (Note 7)
DAC Resolution
12
bits
Integral Nonlinearity
INL
1
LSB
Differential Nonlinearity
DNL
0.5
LSB
100
µA
UNCOMMITTED OP AMP
Op Amp Supply Current
Input Common-Mode Range
Open-Loop Gain
Offset Voltage (as unity-gain
follower)
CMR
VSS + 1.3
VDD - 1.0
AV
VOS
60
VIN = 2.5V (no load)
Output Voltage Swing
No load
Output Current Range
VOUT = (VSS + 0.2V) to (VDD - 0.2V)
-30
+30
VSS + 0.05
V
dB
VDD - 0.05
±500
mV
V
µA
DIGITAL INPUTS: START, CS1, CS2, SDIO (Note 8), RESET, XIN (Note 9), TEST
Input High Voltage
Input Low Voltage
Input Hysteresis
VIH
4.0
V
VIL
1.0
VHYST
1.0
V
V
Input Leakage
IIN
VIN = 0 or VDD
±10
µA
Input Capacitance
CIN
(Note 10)
50.0
pF
Output Voltage Low
VOL
ISINK = 500μA
0.5
V
Output Voltage High
VOH
ISOURCE = 500μA
DIGITAL OUTPUTS: D[11...0]
Three-State Leakage Current
Three-State Output Capacitance
IL
COUT
4.5
V
CS = 0
±10
µA
CS = 0 (Note 10)
50.0
pF
DIGITAL OUTPUTS: SDIO (Note 8), SDO, EOC, OUT
Output Voltage Low
VOL
ISINK = 500μA
0.3
V
Output Voltage High
VOH
ISOURCE = 500μA
4.7
V
CS = 0
±10
µA
Three-State Leakage Current
Three-State Output Capacitance
IL
COUT
CS = 0 (Note 10)
50.0
pF
Note 1: EEPROM programming requires a minimum VDD = 4.75V. IDD may exceed its limits during this time.
Note 2: This value does not include the sensor or load current. This value does include the uncommitted op amp current. Note that
the MAX1460 will convert continuously if REPEAT MODE is set in the EEPROM.
Note 3: See the Analog Front-End, including PGA, Coarse Offset DAC, ADC, and Temperature Sensor sections.
Note 4: The signal input to the ADC is the output of the PGA plus the output of the CO-DAC. The reference to the ADC is VDD.
The plus full-scale input to the ADC is +VDD and the minus full-scale input to the ADC is -VDD. This specification shows the
contribution of the CO-DAC to the ADC input.
Note 5: See Figure 2 for ADC outputs between +0.8500 to -0.8500.
Note 6: The sensor and the MAX1460 must always be at the same temperature during calibration and use.
Note 7: The Output DAC is specified using the external lowpass filter (Figure 8).
Note 8: SDIO is an input/output digital pin. It is only enabled as a digital output pin when the MAX1460 receives from the test system
the commands 8 hex or A hex (Table 4).
Note 9: XIN is a digital input pin only when the TEST pin is high.
Note 10: Guaranteed by design. Not subject to production testing.
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Maxim Integrated │ 3
MAX1460
Low-Power, 16-Bit Smart ADC
Pin Description
PIN
NAME
1, 2, 12,
13, 18, 19,
31, 32, 36,
41–45
N.C.
3
AGND
Analog Ground. Connect to VDD and VSS using 10kΩ resistors (see Functional Diagram).
4
START
Optional conversion start input signal, used for extending sensor warm-up time. Internally pulled to
VDD with a 1MΩ (typical) resistor.
5
I.C.
Internally Connected. Leave unconnected.
6
D6
Parallel Digital Output - bit 6
7
D7
Parallel Digital Output - bit 7
8
D8
Parallel Digital Output - bit 8
9
D9
Parallel Digital Output - bit 9
10
D10
Parallel Digital Output - bit 10
11
D11
Parallel Digital Output - bit 11 (MSB)
14, 37, 38
VDD
Positive Supply Voltage Input. Connect a 0.1μF bypass capacitor from VDD to VSS. Pins 14, 37, and
38 must all be connected to the positive power supply on the PCB.
15
VSS
Negative Supply Input
16,17
CS1,
CS2
Chip-Select Input. The MAX1460 is selected when CS1 and CS2 are both high. When either CS1 or
CS2 is low, all digital outputs are high impedance and all digital inputs are ignored. CS1 and CS2 are
internally pulled high to VDD with a 1MΩ (typical) resistor.
20
SDIO
Serial Data Input/Output. Used only during programming/testing, when the TEST pin is high. The
test system sends commands to the MAX1460 through SDIO. The MAX1460 returns the current
instruction ROM address and data being executed by the DSP to the test system. SDIO is internally
pulled to VSS with a 1MΩ (typical) resistor. SDIO goes high impedance when either CS1 or CS2 is
low and remains in this state until the test system initiates conversion.
21
SDO
Serial Data Output. Used only during programming/testing. SDO allows the test system to monitor the
DSP registers. The MAX1460 returns to the test system results of the DSP current instruction. SDO is
high impedance when TEST is low.
22
RESET
Reset Input. When TEST is high, a low-to-high transition on RESET enables the MAX1460 to accept
commands from the test system. This input is ignored when TEST is low. Internally pulled high to VDD
with a 1MΩ (typical) resistor.
23
EOC
End of Conversion Output. A high-to-low transition of the EOC pulse can be used to latch the Parallel
Digital Output (pins D[11...0]).
24
D0
Parallel Digital Output - bit 0 (LSB)
25
D1
Parallel Digital Output - bit 1
26
D2
Parallel Digital Output - bit 2
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FUNCTION
No Connection. Not internally connected.
Maxim Integrated │ 4
MAX1460
Low-Power, 16-Bit Smart ADC
Pin Description (continued)
PIN
NAME
FUNCTION
27
D3
Parallel Digital Output - bit 3
28
D4
Parallel Digital Output - bit 4
28
D5
Parallel Digital Output - bit 5
30
OUT
33
AMPOUT
34
AMP+
Noninverting Input of General-Purpose Operational Amplifier
35
AMP-
Inverting Input of General-Purpose Operational Amplifier
39
XOUT
Internal Oscillator Output. Connect a 2MHz ceramic resonator (Murata CST200) or crystal from XOUT
to XIN.
40
XIN
Internal Oscillator Input. When TEST is high, this pin must be driven by the test system with a 2MHz,
50% duty cycle clock signal. The resonator does not need to be disconnected in test mode.
46
INP
Positive Sensor Input. Input impedance is typically > 1MΩ. Rail-to-Rail® input range.
47
TEST
48
INM
Output DAC. The bitstream on OUT, when externally filtered, creates a ratiometric analog output
voltage. OUT is proportional to the 12-bit parallel digital output.
General-Purpose Operational Amplifier Output
Test/Program Mode Enable Input. When high, enables the MAX1460 programming/testing operations.
Internally pulled to VSS with a 1MΩ (typical) resistor.
Negative Sensor Input. Input impedance is typically > 1MΩ. Rail-to-rail input range.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
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Maxim Integrated │ 5
MAX1460
Low-Power, 16-Bit Smart ADC
Detailed Description
The main functions of the MAX1460 include:
●● Analog Front End: Includes PGA, coarse-offset DAC,
ADC, and temperature sensor
●● Test System Interface: Writes calibration coefficients
to the DSP registers and EEPROM
●● Test System Interface: observes the DSP operation.
The sensor signal enters the MAX1460 and is adjusted
for coarse gain and offset by the analog front end. Five
bits in the configuration register set the coarse-offset DAC
and the coarse gain of the PGA (Tables 1 and 2). These
bits must be properly configured for the optimum dynamic
range of the ADC. The digitized sensor signal is stored in
a read-only DSP register.
The on-chip temperature sensor also has a 3-bit coarseoffset DAC that places the temperature signal in the ADC
operating range. Digitized temperature is also stored in
a read-only DSP register. The DSP uses the digitized
sensor, the temperature signals, and the correction coefficients to calculate the compensated and corrected output.
The MAX1460 supports an automated production environment, where a test system communicates with a batch
of MAX1460s and controls temperature and sensor excitation. The three-state digital outputs on the MAX1460
Table 1. Nominal PGA Gain Settings
PGA
SETTING
PGA-1
PGA-0
NOMINAL GAIN
(V/V)
0
0
0
46
1
0
1
61
2
1
0
77
3
0
1
93
allow parallel connection of transducers, so that all five
serial interface lines (XIN, TEST, RESET, SDIO, and
SDO) can be shared. The test system selects an individual transducer using CS1 and CS2. The test system
must vary the sensor’s input and temperature, calculate
the correction coefficients for each unit, load the coefficients into the MAX1460 nonvolatile EEPROM, and test
the resulting compensation.
The MAX1460 DSP implements the following characteristic equation:
(
D= Gain 1 + G1T + G 2T 2
)
(Signal + Of0 + Of1T + Of 2T 2) + D OFF
where Gain corrects the sensor’s sensitivity, G1 and G2
correct for Gain-TC, T and Signal are the digitized outputs
of the analog front end, Of0 corrects the sensor’s offset,
Of1 and Of2 correct the Offset-TC, and DOFF is the output
offset pedestal.
The test system can write the calibration coefficients into
the MAX1460 EEPROM or write to the DSP registers
directly. The MAX1460 can begin a conversion using
either the EEPROM contents or the register contents.
When the test system issues commands, the MAX1460
is a serially controlled slave device.
The test system observes the MAX1460 DSP operation in
order to acquire the temperature and signal ADC results,
to verify the calibration coefficients, and to get the output
D. The MAX1460 places the contents of several important DSP registers on the serial interface after the tester
issues a Start Conversion command.
After calibration, compensation, and final test, the
MAX1460 is adapted to its sensor and the pair can be
removed from the test system. Use the resulting trans-
Table 2. Typical Coarse Offset DAC Settings
CO-0
% VDD
(at ADC
input)
PGA SETTING
0
(mV RTI)
(VDD = 5V)
PGA SETTING
1
(mV RTI)
(VDD = 5V)
PGA SETTING
2
(mV RTI)
(VDD = 5V)
PGA SETTING
3
(mV RTI)
(VDD = 5V)
1
1
-149
-162
-122
-97
-80
1
1
0
-96
-104
-79
-62
-52
-1
1
0
1
-47
-51
-39
-31
-25
-0
1
0
0
5
5
4
3
3
+0
0
0
0
-5
-5
-4
-3
-3
+1
0
0
1
47
51
39
31
25
+2
0
1
0
96
104
79
62
52
+3
0
1
1
149
162
122
97
80
CO
SETTING
CO-S
CO-1
-3
1
-2
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Maxim Integrated │ 6
MAX1460
Low-Power, 16-Bit Smart ADC
ducer by applying power and the START signal. Latch
the 12-bit parallel digital output using the EOC pulse. The
maximum conversion rate of the MAX1460 is 15Hz, using
a 2MHz resonator. If an analog output is desired, build a
simple lowpass filter using the OUT pin, the uncommitted
op amp, and a few discrete components (Figure 8).
Analog Front End, Including PGA, Coarse Offset DAC, ADC, and Temperature Sensor
Before the sensor signal is digitized, it must be gained
and coarse-offset corrected to maximize the ADC dynamic range. There are 2 bits (four possible settings) in the
configuration register for the PGA gain, and 3 bits (eight
possible settings) for the CO DAC. The flowchart (Figure
1) shows a procedure for finding the optimum analog
–MAKE A TEST SYSTEM VARIABLE CALLED “NoMoreGain.”
–SET THE TEMPERATURE TO WHERE THE SENSOR’S SENSITIVITY IS HIGHEST. THIS IS NORMALLY COLD FOR SILICON PRTs.
–SET THE PGA GAIN SETTINGS TO MINIMUM.
–CLEAR THE VARIABLE “NoMoreGain.”
–APPLY MIDSCALE EXCITATION TO THE SENSOR.
–FIND THE COARSE OFFSET DAC SETTING WHERE THE DIGITIZED SIGNAL REGISTER IS CLOSEST TO ZERO (MIDSCALE).
–APPLY MINIMUM SENSOR EXCITATION.
–TEST FOR CLIPPING (DIGITIZED SIGNAL < -0.85).
–APPLY MAXIMUM SENSOR EXCITATION.
–TEST FOR CLIPPING (DIGITIZED SIGNAL > 0.85).
THE SENSOR SENSITIVITY
IS TOO LARGE. ADD A
RESISTOR BETWEEN THE
TOP OF THE BRIDGE
AND VDD , THEN
START OVER.
DID ADC CLIP?
YES
IS THE PGA AT
MINIMUM GAIN?
VDD
SERIES
RESISTOR
YES
SENSOR
NO
NO
–REDUCE THE PGA GAIN ONE STEP.
–SET THE VARIABLE “NoMoreGain.”
IS THE PGA AT
MAXIMUM GAIN?
NO
IS “NoMoreGain” SET?
YES
NO
INCREASE THE PGA GAIN ONE STEP.
YES
RECORD THE PGA AND COARSE OFFSET SETTINGS.
CAUTION: CLIPPING IS STILL POSSIBLE FOR LARGE SENSOR’S OFFSET TC AND LARGE TEMPERATURE RANGES.
IF NECESSARY, GUARDBAND AGAINST CLIPPING BY REDUCING THE ±0.85 CLIPPING CONSTANTS ABOVE.
Figure 1. Flowchart for Determining PGA and CO Settings
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Maxim Integrated │ 7
MAX1460
Low-Power, 16-Bit Smart ADC
0.010
4
3
0.006
ERROR (16-BIT LSBs)
NONLINEARITY ERROR (%FS)
0.008
0.004
0.002
0
-0.002
0.004
-0.006
-100 -80 -60 -40 -20 0
20 40 60 80 100
SENSOR SIGNAL INPUT OR ADC INPUT/OUTPUT RANGE (%)
NOISE STANDARD DEVIATION (16-BIT LSBs)
Figure 2a. Analog Front-End INL (typical)
0
-1
-2
-4
-100 -80 -60 -40 -20 0
20 40 60 80 100
SENSOR SIGNAL INPUT OR ADC INPUT RANGE (%)
Figure 2b. Analog Front-End Differential Nonlinearity (DNL)
(typical)
+5V. The full scale (-FS) output of the sensor is then
+5V(-12mV/V) = -60mV; +FS is then +5V (-12mV/V +
10mV/V) = -10mV. Following through the flowchart, the
PGA gain setting is +3 (gain = 93V/V) and the CO correction setting is +1 (+25mV RTI) - (Referred-to Input).
The coarsely corrected -FS input to the ADC is (-60mV +
25mV)93 = -3.255V. The +FS input to the ADC is (-10mV
+ 25mV)93 = +1.395V. The input range of the ADC is
±VDD. Thus the maximum and minimum digitized sensor signals become -3.255 / 5 = -0.651 and +1.395 / 5 =
+0.279.
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1
-3
-0.008
-0.010
2
-100 -80 -60 -40 -20 0
20 40 60 80 100
SENSOR SIGNAL INPUT OR ADC INPUT/OUTPUT RANGE (%)
Figure 2c. Analog Front-End Noise Standard Deviation of the
Samples (typical)
front-end settings when the sensor’s characteristics are
unknown. Use the tabulated values (Tables 1 and 2) if the
peak sensor excursions are known. See the Test System
Interface section for details on writing these analog frontend bits.
The PGA gain and the CO are very stable, but are not
accurate. Manufacturing variances on the gain and offset of the MAX1460 analog front-end superposition the
residual sensor errors, and are later removed during final
calibration.
For example, suppose the sensor’s sensitivity is +10mV/V
with an offset of -12mV/V. Let the supply voltage be
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Notice that the bridge multiplies the signal by VDD and the
ADC divides the signal by VDD. Thus, the system is ratiometric and not dependent on the DC value of VDD. The
ADC output clips to ±1.0 when input values exceed ±VDD.
The best signal-to-noise ratio (SNR) is achieved when the
ADC input is within ±85% of VDD (Figure 2).
The MAX1460 includes an internal temperature-sensing
bridge allowing the MAX1460 temperature to be used as
a proxy for the sensor temperature. For this reason the
MAX1460 must be mounted in thermal proximity to the
sensor. The output of the temperature-sensing bridge
is also corrected by a 3-bit coarse-offset DAC and processed by the ADC. The selection of the Temperature
Sensor Offset (TSO) bits in the configuration register
should be made so that the digitized temperature signal is
as close to 0.0 as possible at midscale temperature. This
is done to maximize the dynamic range of the thermalcalibration coefficients (Table 3).
Maxim Integrated │ 8
MAX1460
Low-Power, 16-Bit Smart ADC
MIN
16 CLK
CYCLES
00 01 02 03 29 30 31 00 01 02 03
29 30 31 00 01 02 03 29 30 31 00 01 02 03 29 30 31
XIN
TEST
RESET
D0 D1 D2 D3 C3 NU NU D0 D1 D2 D3 C3 NU NU D0 D1 D2 D3 C3 NU NU D0 D1 D2 D3 C3 NU NU
SDIO
COMMAND 1
D0 D1 D2 D3 D4
COMMAND 2
COMMAND 3
COMMAND n
D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 E0 E1 E2 E3 E4 E5 E6 R0 R1 R2 C0 C1 C2 C3 NU NU
LSB
MSB LSB
REGISTER DATA FIELD
EEPROM ADDRESS
FIELD
MSB LSB
MSB LSB
MSB
REG.
COMMAND
ADD
NOTE: ALL TRANSITIONS MUST OCCUR WITHIN 100ns OF THE XIN CLOCK EDGE.
Figure 3. Test-System Command Timing Diagram
Table 3. Temperature Sensor Offset
(TSO) Settings
TSO
SETTING
TSO-2
TSO-1
TSO-0
TEMPERATUR
BRIDGE
OFFSET
0
0
0
0
Maximum
1
0
0
0
–
2
0
1
0
–
3
0
1
0
–
4
1
0
0
–
5
1
0
1
–
6
1
1
0
–
7
1
1
1
Minimum
Test-System Interface: Writing Calibration
Coefficients to the DSP Registers
and EEPROM
To make the MAX1460 respond to commands from the
test system, raise the TEST pin and drive XIN with a 2MHz
clock signal. It is not necessary to remove the resonator.
RESET must be low for at least 16 clock cycles to initialize
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the MAX1460. Then, a rising transition on RESET begins
a 32-bit serial transfer of the testsystem command word
through SDIO. The test system transitions SDIO on falling
edges of the XIN clock; the MAX1460 latches data is on
the rising edge (Figure 3).
The 32-bit command word generated by the test-system
is divided into four fields (Figure 3). The 4-bit command
field is interpreted in Table 4. The other fields are usually ignored, except that command 1 hex uses the two
register fields, and command 2 hex requires an EEPROM
address. The command word fields are:
●● Register Data Field: Holds the calibration coefficients
to be written into the MAX1460 16-bit registers
●● EEPROM Address Field: Holds the hexadecimal
address of the EEPROM bit to be set (from 00 hex to
7F hex)
●● Register Address Field: Contains the address of the
register (0 to 7) where the calibration coefficient is to
be written
●● Command Field: Instructs the MAX1460 to take a particular action (Table 4)
Maxim Integrated │ 9
MAX1460
Low-Power, 16-Bit Smart ADC
Table 4. Test System Commands
COMMAND
HEX CODE
C3 C2 C1 C0
Write a calibration coefficient into a DSP register.
1 hex
0
0
0
1
Block-Erase the entire EEPROM (writes “0” to all 128 bits).
4 hex
0
1
0
0
Write “1” to a single EEPROM bit.
2 hex
0
0
1
0
NOOP (NO-OPeration)
0 hex
0
0
0
0
Start Conversion command. The registers are not updated with EEPROM values.
SDIO and SDO are enabled as DSP outputs.
8 hex
1
0
0
0
Start Conversion command. The registers are updated with EEPROM values. SDIO
and SDO are enabled as DSP outputs.
A hex
1
0
1
0
Start Conversion command. The registers are not updated with EEPROM values.
SDIO and SDO are disabled.
C hex
1
1
0
0
Start Conversion command. The registers are updated with EEPROM values. SDIO
and SDO are disabled.
E hex
1
1
1
0
3, 5, 6, 7, 9, B, D, F hex
-
-
-
-
Reserved
Table 5. DSP Calibration Coefficient Registers
COEFFICIENT
REGISTER
ADDRESS
FUNCTION
RANGE
Gain
1
Gain correction
-32768 to +32767
Integer
G1
2
Linear TC gain
-1.0 to +0.99997
Fraction
G2
3
Quadratic TC gain
-1.0 to +0.99997
Fraction
Of0
4
Offset correction
-1.0 to +0.99997
Fraction
Of1
5
Linear TC offset
-1.0 to +0.99997
Fraction
Of2
6
Quadratic TC offset
-1.0 to +0.99997
Fraction
DOFF
7
Output midscale pedestal
-32768 to +32767
Integer
Writing to the DSP Registers
Command 1 hex writes calibration coefficients from the
test system directly into the DSP registers. Tester commands 8 hex and C hex cause the MAX1460 to start a
conversion using the calibration coefficients in the registers. This direct use of the registers speeds calibration
and compensation because it does not require EEPROM
write-access time. Bringing RESET low clears the DSP
registers, so the test system should always write to the
registers and start a conversion in a single command timing sequence.
As shown in Table 5, seven registers hold the calibration
coefficients of the characteristic equation [DOUT = Gain
(1+G1T + G2T2) (Signal + Of0 + Of1T + Of2T2) + DOFF]
implemented by the MAX1460 DSP. All of th registers are
16-bit, two’s complement coding format. When a register
www.maximintegrated.com
FORMAT
is interpreted as an integer, the decimal range is from
-32768 (8000 hex) to +32767 (7FFF hex). Fractional
coefficient values range from -1.0 (8000 hex) to +0.99997
(7FFF hex).
The register at address 0 is called the Configuration
Register. It holds the coarse offset, PGA gain, Op Amp
Power-Down, temperature-sensor offset, repeat mode,
and reserved bits, as shown in Table 6. The functionality
of the coarse offset, PGA gain, and temperature-sensor
bits are described in the Analog Front End section.
The Op Amp Power-Down bit enables the uncommitted
op amp when set. The repeat-mode bit is tested by the
last instruction of the DSP microcode, and, if set, immediately initiates another conversion cycle. The Maxim
reserved bits should not be altered.
Maxim Integrated │ 10
MAX1460
Low-Power, 16-Bit Smart ADC
Table 6. Configuration Register Bitmap
EEPROM
ADDRESS
(HEX)
BIT
POSITION
01
0 (LSB)
CO-0 (LSB)
02
1
CO-1 (MSB)
03
2
CO-S (Sign)
04
3
PGA-1 (MSB)
05
4
PGA-0 (LSB)
06
5
Maxim Reserved
07
6
Maxim Reserved
08
7
Op Amp Power-Down
09
8
Maxim Reserved
DESCRIPTION
0A
9
TSO-0 (LSB)
0B
10
TSO-1
0C
11
TSO-2 (MSB)
0D
12
Maxim Reserved
0E
13
Maxim Reserved
0F
14
Maxim Reserved
10
15 (MSB)
Repeat Mode
Writing to the Internal EEPROM
The test system writes to the EEPROM with commands
4 hex (Block-Erase the entire EEPROM), 2 hex (Write
“1” to a single EEPROM bit) and 0 hex (NOOP). During
normal operation (when the TEST pin is low) or when
the test system issues instructions A hex or E hex (Start
conversion from EEPROM values), the DSP reads the
Calibration Coefficients from the EEPROM.
In the normal production flow, determine the calibration coefficients using direct register access. Then load
the calibration coefficients into the EEPROM with tester
instruction 2 hex. Instruction 4 hex block-erases the
EEPROM and is necessary only for a rework or reclaim
operation. For each part, the Maxim reserved bits in the
Configuration Register should be read before instruction
4 hex is issued, and restored afterwards. The MAX1460
is shipped with its internal EEPROM uninitialized, except
for the reserved bits.
locations that are to be set. There is no bitclear instruction. Any EEPROM write operation is necessarily long
because the internal charge pump must create and maintain voltages above 20V long enough to cause a reliably
permanent change in the memory.
Writing an EEPROM bit requires 6ms, so writing the
EEPROM typically requires less than 400ms. Do not
decrease the EEPROM write times.
To write an EEPROM bit, the test system must be compliant with the Command Timing Diagram shown in Figure
3, performing the following operations:
1) Issue command 0 hex, including the EEPROM address
field of the bit to be written.
2) Issue command 2 hex, with the address field used in
step 1. Continuously repeat this command 375 times
(6ms).
3) Issue command 0 hex, including the EEPROM address
field used in steps 1 and 2.
The procedure for using command 4 hex (Block-Erase
the EEPROM) is similar. Record the Maxim Reserved bits
in the configuration register prior to using this command,
and restore them afterwards. The number of Block-Erase
operations should not exceed 100.
1) Issue command 0 hex.
2) Issue command 4 hex. Continuously repeat this command 375 times (6ms).
3) Issue command 0 hex.
Test System Interface:
Observing the DSP Operation
Test system commands 8 hex and A hex initiate a conversion while allowing the test system to observe the operation of the DSP. To calibrate a unit, the test system must
know the digitized temperature and sensor signals, stored
in DSP registers 8 and 9, and the calibrated and compensated output stored in DSP register 10. The test system
should also verify the EEPROM contents, registers 0–7.
All these signals pass through DSP register S during the
execution of the instruction ROM microcode. The SDO pin
outputs the S register values, and the SDIO pin tells the
tester which signal is currently on S.
The internal 128-bit EEPROM is arranged as eight 16- bit
words. These eight words are the configuration register
and the seven calibration-coefficient values (Table 7).
The MAX1460 EEPROM is bit addressable. The final calibration coefficients must be mapped into the EEPROM
www.maximintegrated.com
Maxim Integrated │ 11
MAX1460
Low-Power, 16-Bit Smart ADC
Table 7. EEPROM Memory Map
EE Address (hex)
Contents
10
20
Contents
MSB
EE Address (hex)
30
EE Address (hex)
Contents
EE Address (hex)
Contents
EE Address (hex)
Contents
EE Address (hex)
Contents
EE Address (hex)
Contents
0E
0D
0C
0B
0A
MSB
EE Address (hex)
Contents
0F
09
1F
1E
1D
1C
1B
1A
19
2F
2E
2D
2C
2B
2A
3F
3E
3D
3C
3B
3A
03
02
4F
4E
4D
4C
4B
4A
17
16
15
14
13
12
27
26
25
24
23
22
37
36
35
34
33
32
5E
5D
5C
5B
5A
48
59
47
46
45
44
43
42
6E
6D
6C
6B
6A
58
69
57
56
55
54
53
52
7E
7D
7C
7B
7A
79
68
INSTRUCTION
CODE (PS)
(HEX)
PROGRAM
COUNTER
(P)
(HEX)
D0
66 or 6C
D1
47
Register 1—Gain
D2
11
Register 2—G1
D3
2E
Register 3—G2
D4
38
Register 4—Of0
D5
03
Register 5—Of1
D6
22
Register 6—Of2
D7
56
Register 7—DOFF
D8
01
Register 8—Temperature
Signal
D9
3B
Register 9—Sensor Signal
EA
65 or 6B
Register 10—Compensated
Output D
S REGISTER VALUE
CO-0 (LSB)
51
67
66
65
64
63
62
61
LSB
78
DOFF
Table 8. Subset of DSP Instruction
41
LSB
Of2
7F
31
LSB
Of1
6F
21
LSB
Of0
5F
11
LSB
38
49
01
LSB
G2
MSB
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04
LSB
28
39
MSB
00
05
G1
MSB
70
18
29
MSB
60
06
Gain
MSB
50
07
Configuration
MSB
40
08
77
76
75
74
73
72
71
LSB
There are three internal DSP registers that are directly
observable on the SDIO and SDO pins:
●● S: 16-bit DSP Scratch or Accumulator register, containing the result of the execution of the current microcode instruction.
●● P: 8-bit DSP Program Pointer register, which holds the
address of the instruction ROM microcode.
●● PS: 8-bit DSP Program Store register. PS is the
instruction that the DSP is currently executing. PS is
the instruction ROM data at address P.
The DSP instructions relevant to the test system are listed
in Table 8.
After the test system sends the Start Conversion commands 8 hex or A hex, SDIO and SDO are both enabled
as MAX1460 serial outputs. The test system should
disable (high impedance) its SDIO driver to avoid a bus
conflict at this time so that the MAX1460 can drive the
pin. After the DSP executes each one of the microcode
instructions, the contents of the registers S, P, and PS are
output in a serial format (Figure 4). A new DSP instruction
and a new state of the S, P, and PS registers are delivered
every 16n + 9 clock cycles, where n = 0, 1, 2... after the
Start Conversion command completes. The tester should
latch the SDIO and SDO bits on the falling edge of the
Maxim Integrated │ 12
MAX1460
Low-Power, 16-Bit Smart ADC
(16 n + 9)th CLOCK CYCLE
(16 (n + 1) + 9)th CLOCK CYCLE
XIN
LSB
MSB
SDO
S12 S13 S14 S15 S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11
SDIO
PS4 PS5 PS6 PS7 P0 P1 P2 P3 P4 P5 P6 P7 PS0 PS1 PS2 PS3 PS4 PS5 PS6 PS7 P0 P1 P2 P3 P4 P5 P6 P7 PS0 PS1 PS2 PS3
LSB
MSB LSB
DSP CYCLE n-1
MSB
DSP CYCLE n
DSP CYCLE n+1
NOTE: ALL TRANSITIONS MUST OCCUR WITHIN 100ns OF THE XIN CLOCK EDGE.
Figure 4. DSP Serial Output Timing Diagram
tCONV
VDD
tWARM
START
(OPTIONAL)
tADC
SDIO & SDO
(TEST MODE)
tDSP
D [11...0]
EOC
tEOC
Figure 5. MAX1460 Conversion Timing
XIN clock signal. When the P and PS registers in Table 8
appear on SDIO, the tester should save the corresponding SDO data.
The conversion timing of the MAX1460 is shown in Figure
5 and Table 9. In the figure, the conversion is initiated by
a rising transition on the START pin. Equivalently, conversion can be initiated in TEST mode after completion of
tester commands 8 hex or A hex, or reinitiated by the state
of the Repeat Mode bit in the configuration register. After
a conversion is initiated, the 16-bit ADC digitizes the tem-
www.maximintegrated.com
perature and sensor signals during tADC. Then, the DSP
executes the instruction ROM microcode during tDSP. In
TEST mode, and during tDSP, SDIO and SDO outputs
carry useful information. At 130,586 clock cycles after the
Start Conversion command is received, the LSB of the S
and P DSP registers is available on SDO and SDIO. The
last DSP instruction is D0 hex. The tester can now start a
new communication sequence by lowering the RESET pin
for at least 16 clock cycles, and then resume driving SDIO.
SDIO becomes high impedance when RESET is low.
Maxim Integrated │ 13
MAX1460
Low-Power, 16-Bit Smart ADC
Table 9. MAX1460 Conversion Timing
PARAMETER
SYMBOL
MIN
MAX
UNITS
tWARM
35
—
ms
ADC Time
tADC
130,585
130,585
XIN clk cycles
DSP Time
tDSP
3,220
3,364
XIN clk cycles
EOC Pulse Width
tEOC
8
8
XIN clk cycles
Conversion Time
tCONV
133,805
133,949
XIN clk cycles
Sensor Warm-Up Time
Applications Information
Calibration and Compensation Procedure
Perform fine calibration by characterizing the sensor/
MAX1460 pair using the test system and then finding the
calibration coefficients Gain, G1, G2, Of0, Of1, and Of2
using the equations below. This simple fine-calibration
procedure requires three temperatures, denoted A, B, and
C, and two sensor excitations, named S and L for small
and large. Thus, there are six data points (AS, AL, BS, BL,
CS, and CL); six unknown calibration coefficients; and six
versions of the characteristic equation, in the form:
Equation (1)
(
D L − D OFF = Gain 1 + G1TC + G 2TC 2
(Signal CL + Of0 + Of1TC + Of 2TC 2)
)
where DL, DS, and DOFF are determined by the end
product specification. DL is the desired MAX1460 output
corresponding to the L sensor excitation; DS is the desired
MAX1460 output corresponding to the S sensor excitation; DOFF is the desired midscale output; SignalCL is the
digitized sensor reading at temperature C with the L sensor excitation applied; and TC is the digitized temperature
reading at temperature C.
Unstable digitized temperature readings indicate that
thermal equilibrium has not been achieved, necessitating increased soak times or a better thermal control.
Averaging many readings from the MAX1460 will help
filter out AC variations in the sensor excitation and oven
temperature.
Begin calibration by soaking the sensor and the MAX1460
pair at the first temperature, A, and apply the L excitation
to the sensor. Start a conversion and record the digitized
temperature TA and the digitized signal SignalAL. Apply
the S sensor excitation, and record the digitized signal
SignalAS. Repeat this procedure for temperatures B and
C, recording TB, SignalBL, SignalBS, TC, SignalCL, and
SignalCS.
www.maximintegrated.com
The AL and AS versions of equation 1 may be ratioed to
obtain:
Equation (2a)
Signal AL − x ⋅ Signal AS
+ Of 0 + Of1T A + Of 2T A 2 =
0
1− x
Similarly,
Equation (2b)
Signal BL − x ⋅ Signal BS
+ Of 0 + Of1TB + Of 2TB 2 =
0
1− x
Equation (2c)
Signal CL − x ⋅ Signal CS
+ Of 0 + Of1TC + Of 2TC 2 =
0
1− x
where
Equation (3)
x=
D L − D OFF
D S − D OFF
Equations 2a, 2b, and 2c form a system of three linear
equations, with three unknowns, Of0, Of1, and Of2. Solve
for Of0, Of1, and Of2.
Equation (4a)
(YCS − YAS ) + G1 (TA YCS − TCYAS ) +
(
)
G 2 T A 2YCS − TC 2Y AS =
0
The small sensor excitation versions of Equation 1 can be
ratioed to obtain:
Equation (4b)
(YCS − YBS ) + G1 (TB YCS − TCYBS ) +
(
)
G 2 TB 2YCS − TC 2YBS =
0
Maxim Integrated │ 14
MAX1460
Low-Power, 16-Bit Smart ADC
UNCOMPENSATED SENSOR ERROR
CF
1µF
10
8
6
ERROR (%FSO)
4
VDD
2
0
FSO
-2
-4
RD1
10k
-8
-10
RD2
10k
0
10
20
30
40
50
AMP-
AGND
OFFSET
-6
OUT
UNFILTERED
BITSTREAM
RF
500k
R1
500k
60
MAX1460
OP AMP
AMPOUT
AMP+
FILTERED
ANALOG
OUTPUT
70
TEMPERATURE (°C)
Figure 6. Sensor Characteristics Before Compensation
Figure 8. Filtering the Output DAC
Equation (5c)
ERROR (% SPAN, 4000 CODES)
0.20
COMPENSATED TRANSDUCER ERROR
0.15
0.10
0.05
Equations 4a and 4b form a system of two linear equations and two unknowns, G1 and G2. Solve for G1 and
G2. Equation 1 can now be readily solved for the last
unknown, Gain.
FSO
0
OFFSET
-0.05
-0.10
-0.15
-0.20
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
Figure 7. Compensated Sensor/MAX1460 Pair
where:
Equation (5a)
Y AS =
Signal AL − x ⋅ Signal AS
+ Of 0 + Of1T A + Of 2T A 2 =
0
1− x
D S − D OFF
Arithmetic manipulation can magnify measurement errors
and noise. Quantization of the calibration coefficients is
another reason to consider adjusting the Gain and DOFF
coefficients. To do this, load the MAX1460 registers with
the calculated coefficients Gain, G1, G2, Of0, Of1, Of2,
and DOFF. Assuming the oven is still at temperature
C and the S sensor excitation is still applied, measure
the output DCS. Change to the L sensor excitation, and
measure DCL. Compute the new Gain coefficient using
equation 6. Remeasure DCL, and compute the new DOFF
coefficient, given by equation 7.
Equation (6)
Signal AS + Of 0 + Of1T A + Of 2T A 2
Equation(5b)
Signal AL − x ⋅ Signal AS
+ Of 0 + Of1T A + Of 2T A 2 =
0
1− x
www.maximintegrated.com
GAIN new = Gain
DL − D S
D CL − D CS
Equation (7)
D OFFnew= D OFF + D L − D CL
The final calibration coefficients may now be written into
the MAX1460 EEPROM. The unit is now ready for final
test.
Maxim Integrated │ 15
MAX1460
4)Detailed Design/Applications manual, developed for
sensor-test engineers.
The evaluation kit order number is MAX1460EVKIT.
37
38
XIN
XOUT
VDD
VDD
39
40
41
42
N.C.
N.C.
N.C.
N.C.
43
44
45
46
47
INM
TEST
INP
N.C.
Pin Configuration
N.C.
N.C.
1
36
2
35
AGND
START
I.C.
D6
3
34
4
33
D7
D8
D9
D10
D11
N.C.
7
30
8
29
9
28
10
27
11
26
12
25
5
32
AMP+
AMPOUT
N.C.
N.C.
OUT
D5
D4
D3
D2
D1
24
23
N.C.
AMP-
EOC
D0
22
21
20
19
18
31
N.C.
N.C.
SDIO
SDO
RESET
17
MAX1460
6
16
The output DAC converts the parallel digital output into
a serial bitstream on OUT. A simple external lowpass
filter, using the MAX1460 op amp, converts the OUT bitstream into a ratiometric analog voltage (Figure 8). The
filter shown is an inverting configuration, but the Gain
and DOFF coefficients of the characteristic equation can
be adjusted to obtain either polarity. If the op amp is not
used, it can be powered down using the Op Amp PowerDown bit in the configuration register.
3)MAX1460 communication/compensation software
(Windows compatible), which enables programming of
the MAX1460 one module at a time.
15
If the sensor requires more than 35ms of warm-up time,
the START pin may be used to initiate conversion (Figure
5). If the Repeat Mode bit is set, START should remain
high. If the Repeat Mode bit is reset, START may be used
to externally control the conversion rate of the MAX1460.
After the 12-bit parallel output D is latched, end the conversion by taking START low for at least one clock cycle.
2) Interface board that must be connected to a PC parallel port.
48
After calibration and removal from the test system, the
MAX1460 and the sensor form a mated pair. The START
pin can be connected to VDD or left unconnected if the
sensor does not require a significant warm-up time. Now
operation is simple: just apply power and latch the parallel
output D when EOC falls. Temperature is digitized during
the first half of tADC, so the MAX1460 provides a minimum
sensor warm-up time of 35ms. Using a 2MHz resonator,
the conversion time tCONV is nominally 67ms. If the Repeat
Mode bit is set, conversions repeat at a rate of 15Hz.
1) Evaluation board, with a MAX1460 sample and a silicon pressure sensor, ready for customer evaluation.
14
Using the Compensated
Sensor/MAX1460 Pair
The MAX1460 evaluation kit (EV kit) speeds the development of MAX1460-based transducer prototypes and test
systems. First-time users of the MAX1460 are strongly
encouraged to use this kit, which includes:
13
Figure 6 shows the characteristics of an individual LucasNovaSensor model NPH8-100-EH, 0 to 15psig, silicon
pressure sensor. Figure 7 shows the result of the compensated sensor/MAX1460 pair.
MAX1460 Evaluation/
Development Kit
N.C.
VDD
VSS
CS1
CS2
This algorithm minimizes the error directly at the six
test conditions, AS, AL, BS, BL, CS, and CL. Space the
temperatures A, B, and C widely to minimize the signaltonoise ratio of the measurement. If there is a large error
remaining in the finished product, move the calibration
temperatures closer to the peak error temperatures.
Similarly, full-scale sensor excitation may not be the best
calibration condition if the sensor has nonlinearities. Move
S and L away from full scale.
Low-Power, 16-Bit Smart ADC
The MAX1460 requires a minimum of external components:
●● One power-supply bypass capacitor (C1) from VDD
to VSS.
●● One 2MHz ceramic resonator (X1).
●● Two 10kΩ resistors for the AGND pin.
●● If an analog output is desired, two 500kΩ resistors and
a 1μF capacitor are needed for filtering.
www.maximintegrated.com
Maxim Integrated │ 16
MAX1460
Low-Power, 16-Bit Smart ADC
Functional Diagram
CS1
CS2
START
TEST
RESET
SDIO
SDO
EOC AMP- AMP+
+5V
10k
AGND
MAX1460
16-BIT INTERFACE TO ALL SIGNALS
10k
2MHz RESONATOR XIN
X1
+5V
OSCILLATOR
CONTROL
LOGIC
EEPROM
XOUT
INSTRUCTION
ROM
VDD
REF = VDD
CONFIGURATION
REGISTER
C1
0.1mF
TEMPERATURE
SENSOR
INP
INM
PGA &
COARSE
OFFSET
CORRECTION
AMPOUT
OP
AMP
CORRECTION
COEFFICIENTS
REGISTERS
DAC
16-BIT
DIGITAL SIGNAL
PROCESSOR
(DSP)
12-BIT DIGITAL OUTPUT
OUT
D [11...0]
REF = VDD
MUX
16-BIT ADC
TEMPERATURE &
SENSOR SIGNAL
REGISTERS
VSS
SENSOR
Chip Information
TRANSISTOR COUNT: 59,855
SUBSTRATE CONNECTED TO VSS
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Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
20 TQFP
C48-6
21-0054
90-0093
Maxim Integrated │ 17
MAX1460
Low-Power, 16-Bit Smart ADC
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
10/99
Initial release
—
1
5/14
Removed automotive information from General Description and Applications sections
1
DESCRIPTION
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2014 Maxim Integrated Products, Inc. │ 18