MAX1462 Datasheet, PDF (5/16 Pages) Maxim Integrated Products – Low-Voltage, Low-Power, 16-Bit Smart ADC

Low-Voltage, 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
29
D5
Parallel Digital Output - Bit 5
30
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.
33
AMPOUT General-Purpose Operational Amplifier Output
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 input 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
Test/Program Mode Enable Input. When high, enables the MAX1462 programming/testing operations.
Internally pulled to V_SS with a 1MΩ (typ) resistor.
48
INM
Negative Sensor Input. Input impedance is typically >1MΩ. Rail-to-Rail input range.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
Detailed Description
The main functions of the MAX1462 include:
• Analog front end: Includes PGA, CO-DAC, ADC,
and temperature sensor.
• Test system interface: Writes calibration coeffi-
cients to the DSP registers and EEPROM.
• Test system interface: Observes the DSP operation.
The sensor signal enters the MAX1462 and is adjusted
for coarse gain and offset by the analog front end. Five
bits in the configuration register set the CO-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 CO-
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 correct-
ed output.
The MAX1462 supports an automated production envi-
ronment, where a test system communicates with a
batch of MAX1462s and controls temperature and sen-
sor excitation. The three-state digital outputs on the
MAX1462 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 tem-
perature, calculate the correction coefficients for each
unit, load the coefficients into the MAX1462 nonvolatile
EEPROM, and test the resulting compensation.
The MAX1462 DSP implements the following character-
istic equation:
D = Gain ₍1 + G₁T + G₂T² ₎ ×
( ) ^{Signal + Of}0 ^{+ Of}1^{T + Of}2^{T2 + D}OFF
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