MAX1455 Datasheet, PDF (5/25 Pages) Maxim Integrated Products – Low-Cost Automotive Sensor Signal Conditioner

Low-Cost Automotive Sensor Signal
Conditioner
PIN
1, 15, 16
2
3
4
5
6
7
8
9
10
11
12
13
14
Pin Description
NAME
TEST1,
TEST3,
TEST2
OUT
INP
BDR
INM
V_SS
V_DD1
AMP+
AMPOUT
AMP-
V_DD2
UNLOCK
DIO
TEST4
FUNCTION
Test Pins. Connect to V_SS or leave unconnected.
Analog Output. Internal voltage nodes can be accessed in digital mode. OUT can be parallel
connected to DIO. Bypass OUT to ground with a 0.1µF capacitor to reduce output noise.
Positive Input. Can be swapped to INM by the Configuration register.
Bridge Drive Output
Negative Input. Can be swapped to INP by the Configuration register.
Negative Supply Voltage
Positive Supply Voltage 1. Connect a 0.1µF capacitor from V_DD to V_SS.
Auxiliary Op Amp Positive Input
Auxiliary Op Amp Output
Auxiliary Op Amp Negative Input
Positive Supply Voltage 2. Connect a 0.47µF capacitor from V_DD2 to V_SS. Connect V_DD2 to V_DD1 or
for improved noise performance, connect a 1kΩ resistor to V_DD1.
Secure-Lock Disable. There is a 150µA pulldown to V_SS. Connect to V_DD to disable Secure-Lock
and enable serial communication.
Digital Input Output. Single-pin serial communication port. There are no internal pullups on DIO.
Connect pullup resistor from DIO to V_DD when in digital mode.
Test Pin. Do not connect.
Detailed Description
The MAX1455 provides amplification, calibration, and
temperature compensation to enable an overall perfor-
mance approaching the inherent repeatability of the
sensor. The fully analog signal path introduces no
quantization noise in the output signal while enabling
digitally controlled trimming with the integrated 16-bit
DACs. The MAX1455 includes four selectable high/low
clipping limits set in discrete 50mV steps from
0.1V/4.9V to 0.25V/4.75V. Offset and span can be cali-
brated to within ±0.02% of span.
The MAX1455 architecture includes a programmable
sensor excitation, a 16-step PGA, a 768-byte (6144 bits)
internal EEPROM, four 16-bit DACs, an uncommitted op
amp, and an on-chip temperature sensor. The MAX1455
also provides a unique temperature compensation strat-
egy that was developed to provide a remarkable degree
of flexibility while minimizing testing costs.
The customer can select from 1 to 114 temperature
points to compensate their sensor. This allows the lati-
tude to compensate a sensor with a simple first-order
linear correction or match an unusual temperature
curve. Programming up to 114 independent 16-bit
EEPROM locations corrects performance in 1.5°C tem-
perature increments over a range of -40°C to +125°C.
For sensors that exhibit a characteristic temperature
performance, a select number of calibration points can
be used with a number of preset values that define the
temperature curve. The sensor and the MAX1455
should be at the same temperature during calibration
and use. This allows the electronics and sensor errors
to be compensated together and optimizes perfor-
mance. For applications where the sensor and elec-
tronics are at different temperatures, the MAX1455 can
use the sensor bridge as an input to correct for temper-
ature errors.
The single pin, serial DIO communication architecture
and the ability to timeshare its activity with the sensor’s
output signal enables output sensing and calibration
programming on a single line by parallel connecting
OUT and DIO. The MAX1455 provides a Secure-Lock
feature that allows the customer to prevent modification
of sensor coefficients and the 52-byte user-definable
EEPROM data after the sensor has been calibrated.
The Secure-Lock feature also provides a hardware
override to enable factory rework and recalibration by
assertion of logic high on the UNLOCK pin.
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