MAX1459 Datasheet, PDF (5/24 Pages) Maxim Integrated Products – 2-Wire, 4-20mA Smart Signal Conditioner

2-Wire, 4–20mA
Smart Signal Conditioner
Pin Description
PIN
NAME
FUNCTION
1
SCLK
Data Clock Input. Used only during programming/testing. Internally pulled to V_SS with a 1MΩ (typical) resistor.
Data is clocked in on the rising edge of the clock. Recommended SCLK frequency is below 50kHz.
2
CS
Chip-Select Input. The MAX1459 is selected when this pin is high. When low, OUT and DIO become high
impedance. Internally pulled to V_DD with a 1MΩ (typical) resistor. Leave unconnected for normal operation.
3
DIO
Data Input/Output. Used only during programming/testing. Internally pulled to V_SS with a 1MΩ (typical)
resistor. High impedance when CS is low.
Write Enable, Dual-Function Input Pin. Used to enable EEPROM erase/write operations. Also used to set
4
WE
the DAC refresh-rate mode. Internally pulled to V_DD with a 1MΩ (typ) resistor. See the Chip-Select (CS)
and Write-Enable (WE) section.
Buffered Full-Span Output Temperature Coefficient DAC Output. An internal 100kΩ resistor (R_FTC) con-
5
FSOTC nects FSOTC to ISRC (see Functional Diagram). Optionally, external resistors can be used in place of or in
parallel with R_FTC and R_ISC.
6
AMP+ Auxiliary Op Amp Positive Input
7
AMP-
Auxiliary Op Amp Negative Input
8
AMPOUT Auxiliary Op Amp Output
Input pin for an External Temperature-Dependent Reference Voltage for FSOTC DAC and OTC DAC. In the
9
TEMPIN default mode, the MAX1459 uses the temperature-dependent bridge drive voltage as the FSOTC DAC and
OTC DAC reference.
10
ISRC
Current Source Reference. An internal 100kΩ resistor (R_ISRC) connects ISRC to V_SS (see Functional
Diagram). Optionally, external resistors can be used in place of or in parallel with R_FTC and R_ISRC.
11
OUT
Output Voltage. OUT is a Rail-to-Rail® output that can drive resistive loads down to 10kΩ and capacitive
loads up to 0.1µF.
12
V_SS
Negative Power Supply
13
BDRIVE Sensor Excitation Current Output. The current source that drives the bridge.
14
INP
Positive Sensor Input. Input impedance is typically 1MΩ. Rail-to-rail input range.
15
INM
Negative Sensor Input. Input impedance is typically 1MΩ. Rail-to-rail input range.
16
TEMP1 Temperature Sensor Terminal 1
17
TEMP2
Temperature Sensor Terminal 2. R_TEMP is a 100kΩ temperature-dependent resistor with 4600ppm/°C
tempco.
18
CK50
Clock Output, nominally 50kHz
19
NBIAS Chip Current Bias Source. Connect an external 402kΩ ±1% resistor between V_DD and NBIAS.
20
V_DD
Positive Power-Supply Input. Connect a 0.1µF capacitor from V_DD to V_SS.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
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