device output waveform is a fixed 50% duty cycle (the pro-
grammed quiescent duty cycle value) regardless of the applied
external magnetic field. After powering-up, the A1354 outputs
its quiescent duty cycle waveform for 800 ms, regardless of the
applied magnetic field (see figure 9). This allows the BCM to
compare the measured quiescent duty cycle with an ideal 50%
duty cycle.
After the initial 800 ms has elapsed, the duty cycle corresponds to
an applied magnetic field as expected. The 800 ms calibration test
time corresponds to a PWM frequency of 125 Hz. If the PWM
frequency is programmed away from its target of 125 Hz, the
duration of the calibration test time will scale inversely with the
change in PWM frequency.
Figure 9. Calibration Test Mode. After powering-on, the A1354 outputs a 50% duty cycle for
the first 800 ms, regardless of the applied magnetic field (Calibration Test mode in effect).
After the initial 800 ms has elapsed, the output responds to a magnetic field as expected.
The example in this figure assumes that a large +B (south polarity) field is applied to the
device after the initial 800 ms.
During Calibration Teat mode
PMW output = 50% duty cycle
After the calibration expires, PWM output
proportional to external magnetic field
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
21
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com