HALL EFFECT GEAR-TOOTH SENSORS

CR3017 Hall effect gear-tooth sensor is monolithic integrated circuits which are ideal for use in gear-tooth-based speed position and timing applications and operate down to zero rpm over a wide range of air gaps and temperatures. When combined with a back biasing magnet and proper assembly techniques, devices can be configured to give suitable duty cycle or to switch on either leading, trailing or both edges of a passing gear tooth or slot. The CR3094 is a self adjusting digital output rotary position gear tooth sensor designed for use in automotive camshaft sensing as well as other speed sensing applications. It is designed to be used with a bias magnet south facing the back (non-marked) side of the IC. The device has an open collector output which is short circuit protected. The CR3094 is a sophisticated IC featuring an on-chip 10-bit A/D Converter and logic that acts as a digital sample and hold circuit. A separate 4- bit A/D converter provides a fixed hysteresis. The CR3094 does not have a chopper delay. The CR3094 uses a single Hall plate which is immune to rotary alignment problems. The bias magnet can be from 100 to 400mT. As the signal is sampled, the logic recognizes an increasing or decreasing flux density. The output will turn on (BOP) after the flux has reached its peak and decreased by an amount equal to the hysteresis. Similarly, the output will turn off (BOP) after the flux has reached its minimum value and increased by an amount equal to the hysteresis.

Ø                      Feature

1.                      Rotary Position Gear Tooth Sensor

2.                      Short Circuit Protection

3.                      On-chip 10 bit A/D Converter

4.                      Self-Adjusting Magnetic Range

5.                      High Speed Operation

6.                      No Chopper Delay

7.                      Zero Speed Detection

8.                      No Rotary Orientation Concerns

Ø                      Application

9.                      Camshaft Sensor

10.                      Geartooth Sensor

11.                      Linear Encoder

12.                      Rotary Encoder

13.                      Direction Detection

Ø                      Functional diagram

Ø                      Pin Description

Ø                      Absolute Maximum Rating

Ø                      Electrical Characteristics              

DC Operating Parameters TA = -55℃ to 150℃, VDD = 4.0V to 30V (unless otherwise specified) 

Ø                      Magnetic Specifications

10Gs=1mT

Ø                      Application and typical connection

A gear-tooth sensing system consists of the sensor IC, a back-biasing magnet, an optional pole piece and gear teeth. The system requirements are usually specified in terms of the effective working air gap between the package and gear teeth, the number of switching events per rotation of the gear tooth, temperature and speed range, minimum pulse duration or duty cycle and switch point accuracy. Careful choice of the sensor IC, magnet material and shape, target material and shape, and assembly techniques enables large working air gaps and high switch-point accuracy over the system temperature range.

Maximum dynamic range is 400 mT. The hysteresis is fixed around at 5.0 mT. Best angular accuracy will be obtained when the magnetic circuit provides peak magnetic flux at the chip near the high end of the linear range of 400 mT. EMC protection using external components are recommended. Two possibilities are shown on the following page. Normally the South pole faces the unbranded side of the device. A North pole will enable a test sequence used in factory testing.

The output is reset to the high state at power on (output driver is off) whatever the field is. The output only changes after the first min is detected. The reset state holds no information about the field. If the supply of the chip is raised slowly, the reset state is not stable. This has been observed at 0 field but it should be the same with small and large fields. Gear tooth sensors often need to be adjusted after the module is assembled to align the magnet with differential Hall plates or orient with teeth. However the CR3017 is “self adjusting” over a wide range of back bias flux eliminating the need for any trimming in the application. The magnet may be glued to the back surface (non branded side) of the IC using a cyanoacrylate adhesive or suitable epoxy.

Ø                      Package Dimension