General Description

The MAX1460 implements a revolutionary concept in
signal conditioning, where the output of its 16-bit ana-
log-to-digital converter (ADC) is digitally corrected over
the specified temperature range. This feature can be
readily exploited by automotive, 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 uncommit-
ted op amp can be used to filter the analog output, or
implement a 2-wire, 420mA transmitter.

The analog front end includes a 2-bit programmable-
gain 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 sen-
sor, and correction coefficients stored in the internal
EEPROM to produce the conditioned output.

Multiple or batch manufacturing of sensors is support-
ed with a completely digital test interface. Built-in testa-
bility 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 cali-

bration and compensation, without removal from the
pretest socket.

The MAX1460 evaluation kit (EV kit) allows fast evalua-
tion 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 calibra-
tion 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, con-
nect the sensor to an excitation source (such as a pres-
sure controller), and run the MAX1460 EV kit software.
An oven is required for thermal compensation.

Features

o Low-Noise, 400µA Single-Chip Sensor Signal

Conditioning

o High-Precision Front End Resolves Less than 1µV

of Differential Input Signal

o On-Chip DSP and EEPROM Provide Digital

Correction of Sensor Errors

o 16-Bit Signal Path Compensates Sensor Offset

and Sensitivity and Associated Temperature
Coefficients

o 12-Bit Parallel Digital Output
o Analog Output
o Compensates a Wide Range of Sensor Sensitivity

and Offset

o Single-Shot Automated Compensation

Algorithm--No Iteration Required

o Built-In Temperature Sensor
o 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 420mA
Transmitters

Smart Battery Charge Systems

Weigh Scales and Strain-Gauge Measurement

Flow Meters

Dive Computers and Liquid-Level Sensing

Hydraulic Systems

Automotive Systems

Customization

Maxim can customize the MAX1460 for unique require-
ments. With a dedicated cell library of more than 90 sen-
sor-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

________________________________________________________________ Maxim Integrated Products

19-4784; Rev 0; 10/99

PART

MAX1460CCM

0°C to +70°C

TEMP. RANGE

PIN-PACKAGE

48 TQFP

Ordering Information

Functional Diagram appears at end of data sheet.

Pin Configuration appears at end of data sheet.

Windows is a registered trademark of Microsoft Corp.

EVALUATION KIT

AVAILABLE

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.

PGA Gain

MAX1460

Low-Power, 16-Bit Smart ADC

_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

= +5V, V

= 0, f

XIN

= 2MHz, T

= T

MIN

to T

MAX

, unless otherwise noted.)

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.

Supply Voltage, V

to V

......................................-0.3V to +6V

All Other Pins ...................................(V

- 0.3V) to (V

+ 0.3V)

Short-Circuit Duration, All Outputs .............................Continuous
Continuous Power Dissipation (T

= +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

CO-DAC code = 011

CO-DAC code = 010

Continuous conversion

CO-DAC code = 001

CO-DAC code = 000

During operation

CO-DAC code = 100

CO-DAC code = 101

CO-DAC code = 110

CO-DAC code = 111

PGA gain code = 11

PGA gain code = 10

From V

to V

PGA gain code = 01

PGA gain code = 00

CONDITIONS

134

149

164

111

-20

-5

-10

-62

-47

-32

-111

-96

-81

% V

-164

-149

-134

Coarse Offset

V/V

µA

400

700

Supply Current (Note 2)

4.75

5.0 5.25

Supply Voltage (Note 1)

CMRR

Common-Mode Rejection Ratio

nV/°C

±1200

Input-Referred Offset TC

Throughput Rate

1.0

Input Impedance

ppm/°C

±40

Gain Temperature Coefficient (TC)

UNITS

MIN

TYP

MAX

SYMBOL

PARAMETER

= 0°C to +70°C

input impedance

PGA gain code = 00, CO-DAC code = 000

°C

1.3

Linearity

LSB/°C

260

Resolution

LSB

RMS

Output-Referred Noise

RMS

1700

Input-Referred Noise

0.006

INL

Integral Nonlinearity (Note 5)

Bits

Resolution

ADC (Notes 3, 4)

TEMPERATURE SENSOR (Note 6)

GENERAL CHARACTERISTICS

ANALOG INPUT

PGA AND COARSE-OFFSET DAC (Notes 3, 4)

PGA Gain

MAX1460

Low-Power, 16-Bit Smart ADC

_______________________________________________________________________________________

CONDITIONS

UNITS

MIN

TYP

MAX

SYMBOL

PARAMETER

DAC Resolution

bits

Integral Nonlinearity

INL

LSB

Differential Nonlinearity

DNL

0.5

LSB

Op Amp Supply Current

100

µA

Input Common-Mode Range

CMR

+ 1.3

- 1.0

Open-Loop Gain

Offset Voltage (as unity-gain
follower)

= 2.5V (no load)

-30

+30

Output Voltage Swing

No load

+ 0.05

- 0.05

Output Current Range

OUT

= (V

+ 0.2V) to (V

- 0.2V)

±500

µA

Note 1: EEPROM programming requires a minimum V

= 4.75V. I

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 V

. The

plus full-scale input to the ADC is +V

and the minus full-scale input to the ADC is -V

. This specification shows the con-

tribution 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 sys-

tem 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.

ELECTRICAL CHARACTERISTICS (continued)

= +5V, V

= 0, f

XIN

= 2MHz, T

= T

MIN

to T

MAX

, unless otherwise noted.)

Input High Voltage

4.0

Input Low Voltage

1.0

Input Hysteresis

HYST

1.0

Input Leakage

= 0 or V

±10

µA

Input Capacitance

(Note 10)

50.0

Output Voltage Low

SINK

= 500µA

0.5

Output Voltage High

SOURCE

= 500µA

4.5

Three-State Leakage Current

CS = 0

±10

µA

Three-State Output Capacitance

OUT

CS = 0 (Note 10)

50.0

Output Voltage Low

SINK

= 500µA

0.3

Output Voltage High

SOURCE

= 500µA

4.7

Three-State Leakage Current

CS = 0

±10

µA

Three-State Output Capacitance

OUT

CS = 0 (Note 10)

50.0

OUTPUT DAC (Note 7)

UNCOMMITTED OP AMP

DIGITAL INPUTS: START, CS1, CS2, SDIO (Note 8), RESET, XIN (Note 9), TEST

DIGITAL OUTPUTS: D[11...0]

DIGITAL OUTPUTS: SDIO (Note 8), SDO, EOC, OUT

MAX1460

Low-Power, 16-Bit Smart ADC

_______________________________________________________________________________________

NAME

FUNCTION

1, 2, 12,

13, 18, 19,
31, 32, 36,

4145

N.C.

No Connection. Not internally connected.

AGND

Analog Ground. Connect to V

and V

using 10k

resistors (see Functional Diagram).

PIN

START

Optional conversion start input signal, used for extending sensor warm-up time. Internally pulled to
V

with a 1M

(typical) resistor.

I.C.

Internally Connected. Leave unconnected.

Parallel Digital Output - bit 9

Parallel Digital Output - bit 8

Parallel Digital Output - bit 7

Parallel Digital Output - bit 6

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 V

with a 1M

(typical) resistor.

Negative Supply Input

14, 37, 38

Positive Supply Voltage Input. Connect a 0.1µF bypass capacitor from V

to V

. Pins 14, 37, and 38

must all be connected to the positive power supply on the PCB.

D11

Parallel Digital Output - bit 11 (MSB)

D10

Parallel Digital Output - bit 10

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 V

with a 1M

(typical) resistor. SDIO goes high impedance when either CS1 or CS2 is low and remains

in this state until the test system initiates conversion.

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.

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 V

with a 1M

(typical) resistor.

Parallel Digital Output - bit 2

Parallel Digital Output - bit 1

Parallel Digital Output - bit 0 (LSB)

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]).

Pin Description

MAX1460

Low-Power, 16-Bit Smart ADC

_______________________________________________________________________________________

Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.

Pin Description (continued)

NAME

FUNCTION

PIN

AMPOUT

General-Purpose Operational Amplifier Output

OUT

Output DAC. The bitstream on OUT, when externally filtered, creates a ratiometric analog output volt-
age. OUT is proportional to the 12-bit parallel digital output.

Parallel Digital Output - bit 5

Parallel Digital Output - bit 4

Parallel Digital Output - bit 3

AMP+

Noninverting Input of General-Purpose Operational Amplifier

AMP-

Inverting Input of General-Purpose Operational Amplifier

XOUT

Internal Oscillator Output. Connect a 2MHz ceramic resonator (Murata CST200) or crystal from XOUT
to XIN.

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.

INP

Positive Sensor Input. Input impedance is typically > 1M

. Rail-to-Rail

input range.

TEST

Test/Program Mode Enable Input. When high, enables the MAX1460 programming/testing operations.
Internally pulled to V

with a 1M

(typical) resistor.

INM

Negative Sensor Input. Input impedance is typically > 1M

. Rail-to-rail input range.

Part Number MAX1460