A1242: Two-Wire Chopper-Stabilized Hall-Effect Latch

This device is no longer in production. The device should not be purchased for new design applications. Samples are no longer available. Date of status change: October 31, 2011.

Recommended Substitutions: For existing customer transition, and for new customers or new applications, refer to the following parts:

• for the A1242ELHLT-I2-T use the A1244LLHLX-I2-T
• for the A1242ELHLT-I1-T use the A1244LLHLX-I1-T
• for the A1242LLHLT-I2-T use the A1244LLHLX-I2-T
• for the A1242LLHLT-I1-T use the A1244LLHLX-I1-T
• for the A1242EUA-I1-T and A1242LUA-I1-T use the A1244LUA-I1-T
• for the A1242LUA-I2-T use the A1244LUA-I2-T

The A1242 Hall-effect latch is a two-wire latch especially suited for operation over extended temperature ranges, from –40 to +150°C. Superior high-temperature performance is made possible through the Allegro patented dynamic offset cancellation technique, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress.

The current-switching output technique allows for the reduction in cost in the wiring harness because only two connections to the sensor OC are required. The current-switching output structure also inherently provides more immunity against EMC/ESD transients. These sensor ICs have low magnetic thresholds, thereby enabling more flexibility in the magnetic circuit design.

The Hall-effect latch will be in the high output current state in the presence of a magnetic South Pole field of sufficient magnitude and will remain in this state until a sufficient North Pole field is present.

The A1242 includes the following on a single silicon chip: a voltage regulator, Hall-voltage generator, small-signal amplifier, chopper stabilization, Schmitt trigger, and a current source output. Advanced BiCMOS wafer fabrication processing takes advantage of low-voltage requirements, component matching, very low input-offset errors and small component geometries.

Suffix ‘L-’ devices are rated for operation over a temperature range of –40°C to +150°C; suffix ‘E-’ devices are rated for operation over a temperature range of –40°C to +85°C. Two A1242 package styles provide magnetically optimized solutions for most applications. Package LH is a SOT23W, a miniature low-profile surface-mount package, while package UA is a three-lead ultra-mini SIP for through-hole mounting. Each package is available lead (Pb) free, with 100% matte tin plated leadframes.

• Chopper stabilization
• Superior temperature stability
• Extremely low switchpoint drift
• Insensitive to physical stress
• Reverse battery protection
• Solid-state reliability
• Small size
• Robust EMC capability
• High ESD ratings (HBM)