High-Performance Power and Hall-Effect Sensor ICs

FAQs - A3212 Micropower, Ultra-Sensitive Hall-Effect Switch

1. Is the A3212 "pole independent"?

Yes. This device is different from Allegro's other unipolar switches because it is pole independent. The term "pole independent" refers to the unique feature of being able to switch on with either a north- or south-pole magnet of sufficient strength. Omnipolar switch is the term for a unipolar switch with pole independence.

2. What is the supply voltage range of the A3212?

The supply range is 2.5 V to 3.5 V.

3. Why is the supply range so much lower and tighter than other Allegro Hall sensor ICs?

Unlike other Allegro Hall sensor ICs, the A3212 does not have its own internal voltage regulator. The regulator was intentionally left out in order to conserve power. The target applications in which it is designed into are battery powered such as cell phones, PDAs, etc. Therefore, the regulator is not as important and can be removed to conserve power on current.

4. Does the A3212 require any external circuitry?

It is strongly recommended that an external bypass capacitor be connected (in close proximity to the Hall sensor IC) between the supply and ground pins of the device to reduce both external noise and noise generated by the chopper-stabilization technique. Additional circuitry may also be required if there are any transients on the line or if reverse battery is possible in the application. The absolute maximum voltage for this part is 5 V and there is no reverse battery protection.

5. What package styles is this device offered in?

The A3212 is available in either the '-UA' (3-lead ultra-mini SIP) through-hole package or the SOT-23 type '-LH' (miniature low profile) surface-mount package.

6. What is the operating temperature range?

The A3212 standard operating range 'E' is from -40°C to +85°C. This device is also available in an extended temperature range 'L' version (-40°C to 150°C).

7. On power up, when will this device begin sampling?

After 90 ms.

8. Can the A3212 be used to detect a moving object such as a rotating magnet?

Yes, but the period of the magnet's rotation must be at least 90 ms. If it is not, there is a chance that this sensor could miss "seeing" the magnet during the sleep mode of its operation.

9. Are there any technical papers concerning the A3212?

Yes. An article written by Christine Graham, Systems Engineer for Allegro's Sensor Business Unit is located at allegromicro.com. The article is for the A3210; however it equally applies to the A3212 with the exception of magnetic switch points and current draw as specified in question 10.

10. What are the differences between the A3212 and A3210?

The A3212 is an improvement to the A3210 in power consumption, magnetic switch points, and offers an extended temperature range as referenced in question 6. The max supply current of the 3212 is lower at 10 µA at 2.75 V, versus the 3210 which is 25 µA. The switch points are tighter with a B_OP of ±55 Gauss and B_RP of ±10 Gauss compared to the A3210 with a B_OP of ±60 Gauss and B_RP of ±5 Gauss. The switch point change allows for operation with a weaker magnetic field while compensating for magnetic noise created by such things as a cellular phone speaker or computer hard drive. The changes make the new device more attractive to applications concerned with battery life and switch point sensitivity.

Related Links:

FAQs - A3212 Micropower, Ultra-Sensitive Hall-Effect Switch