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High-Performance Power ICs and Hall-Effect Sensors
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Datasheets:
A1391, A1392, A1393, and A1395: Micro Power 3 V Linear Hall Effect Sensors with Tri-State Output and User-Selectable Sleep Mode (PDF)
Selection Guides:
Hall-Effect Sensors,
Linear Hall-Effect Sensors
FAQs:
A139x FAQ
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FAQs - A1391/92 
Q1: What happens to the device if it is operated above max Vcc?
Q2: What happens to the device if it is operated below -20°C or above +85°C?
Q3: What happens if Vcc and Vref are tied together and toggled to conserve power?
Q4: What happens if Vref is higher than Vcc?
Q5: What happens if Vcc is higher than Vref?
Q7: How long can Vcc be below Vref and at what voltage?
Q8: What does it mean that the sensitivity of the device is ratiometric with Vref?
Q9: What happens if Vref is connected to a source less than 2.5 V?
Q10: Can I multiplex several sensors to a common input port (i.e. A/D) in the ECU?
Q11: How many A139x devices may be multiplexed in a parallel circuit?
Q1 - What happens to the device if it is operated above max Vcc?
The device will function properly but may also deviate from datasheet limits.
Q2 - What happens to the device if it is operated below -20°C or above +85°C?
Basic device functionality will be held in tact but datasheet specifications per the datasheet will may be compromised.
Q3 - What happens if Vcc and Vref are tied together and toggled to conserve power?
There will not be any issues and the device will function as it would if only the sleep pin was being toggled.
Q4 - What happens if Vref is higher than Vcc?
Sensitivity ratiometry only works up to Vref equal to Vcc, thus sensitivity would no longer be ratiometic to Vref.
Q5 - What happens if Vcc is higher than Vref?
There are no issues as long as Vcc is less than 3.5 V and Vref is greater than 2.5 V.
Q6 - What happens if Vcc is toggled and results in a potential that is lower than Vref for a short duration?
This should not cause any damage to the device.
Q7 - How long can Vcc be below Vref and at what voltage?
The device can handle 400 mV switching transients (digital noise), without a capacitor from Vcc to ground.
Q8 - What does it mean that the sensitivity of the device is ratiometric with Vref?
Sensitivity is directly proportional to Vref and is independent of Vcc variations.
Q9 - What happens if Vref is connected to a source less than 2.5 V?
The Hall plate bias goes into a non-linear state, which results in an invalid output.
Q10 - Can I multiplex several sensors to a common input port (i.e. A/D) in the ECU?
Yes, please see the datasheet for maximum loading.
Q11 - How many A139x devices may be multiplexed in a parallel circuit?
The output capacitance of the A139x in sleep mode is nominally 60 pF. The total capacitance on the output of a 139x should not exceed 10 nF. Thus if the customer were to use an R-C filter or a sufficiently large capacitor on the output of each device, this could decrease the number of units. If the customer does use a capacitor on the output of each device in the circuit, the number of units that may be multiplexed is approximately 165 devices.