A1357 Datasheet, PDF (1/20 Pages) Allegro MicroSystems – Two-Wire High Precision Linear Hall-Effect Sensor IC

A1357
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
Features and Benefits
▪ Two-wire output enables reduced wiring costs in
long wire systems
▪ Simultaneous programming of PWM carrier frequency,
quiescent duty cycle (QDC), and sensitivity for system
optimization
▪ Fully differential signal path increases EMC immunity and
reduces output offset drifts
▪ Factory programmed sensitivity temperature coefficient
and quiescent duty cycle drift
▪ Programmability at end-of-line
▪ Pulse width modulated (PWM) current output provides
increased noise and EMC immunity compared to an
analog output
▪ Precise recoverability after temperature cycling
• Duty cycle clamps provide short circuit diagnostic
capabilities
▪ Optional 50% duty cycle calibration test mode at device
power up
▪ Wide ambient temperature range: –40°C to 150°C
▪ Resistant to mechanical stress
Package: 3-pin SIP (suffix KB)
Not to scale
Description
The A1357 device is a high precision, programmable two-wire
Hall-effect linear sensor IC with a pulse width modulated
(PWM) current. The A1357 device converts an analog signal
from its internal Hall sensor element to a digitally encoded
PWM signal. The coupled noise immunity of the digitally
encoded PWM is far superior to the noise immunity of an
analog output signal.
The BiCMOS, monolithic circuit inside of theA1357 integrates
a Hall element, precision temperature-compensating circuitry
to reduce the intrinsic sensitivity and offset drift of the Hall
element, a small-signal high-gain amplifier, proprietary
dynamic offset cancellation circuits, and PWM conversion
circuitry. The dynamic offset cancellation circuits reduce the
residual offset voltage of the Hall element that is normally
caused by device overmolding, temperature dependencies,
and thermal stress. The high frequency offset cancellation
(chopping) clock allows for a greater sampling rate, which
increases the accuracy of the output current signal and results
in faster signal processing capability.
The A1357 sensor is provided in a lead (Pb) free 3-pin single
inline package (KB suffix), with 100% matte tin leadframe
plating.
V_SUPPLY
VCC (and
programming)
C_BYBASS
A1357-DS
Functional Block Diagram
Regulator
PWM Carrier
Generation
PWM
1
Frequency Trim
2
2
1
Chopper
Switches
Amp
Signal
Recovery
Signal
Conditioning
Sensitivity Temperature % Duty
Trim
Compensation ^Cycle
% Duty Cycle
Temperature
Coefficient
Voltage Controlled
Current Source
GND