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DATASHEET PDFA3210.pdf
¡¡¡¡The A3209Ex and A3210Ex integrated circuits are ultra-sensitive, pole
¡¡¡¡independent Hall-effect switches with a latched digital output.  They are
¡¡¡¡especially suited for operation in battery-operated, hand-held equipment such as
¡¡¡¡cellular and cordless telephones, pagers, and palmtop computers.  2.5 volt to
¡¡¡¡3.5 volt operation and a unique clocking scheme to reduce the average operat-
¡¡¡¡ing power requirements ¨C the A3209Ex to 400 ?W, the A3210Ex to 25 ?W!
¡¡¡¡Except for operating duty cycle and average operating current, the A3209Ex
¡¡¡¡and A3210Ex are identical.
¡¡¡¡Unlike other Hall-effect switches, either a north or south pole of sufficient
¡¡¡¡strength will turn the output on; in the absence of a magnetic field, the output is
¡¡¡¡off.  The polarity independence and minimal power requirement allows these
¡¡¡¡devices to easily replace reed switches for superior reliability and ease of
¡¡¡¡manufacturing, while eliminating the requirement for signal conditioning.
¡¡¡¡Improved stability is made possible through chopper stabilization (dynamic
¡¡¡¡offset cancellation), which reduces the residual offset voltage normally caused
¡¡¡¡by device overmolding, temperature dependencies, and thermal stress.
¡¡¡¡These devices include on a single silicon chip a Hall-voltage generator,
¡¡¡¡small-signal amplifier, chopper stabilization, a latch, and a MOSFET output.
¡¡¡¡Advanced BiCMOS processing is used to take advantage of low-voltage and
¡¡¡¡low-power requirements, component matching, very low input-offset errors,
¡¡¡¡and small component geometries.
¡¡¡¡The A3209Ex and A3210Ex are rated for operation over a temperature
¡¡¡¡range of -40?C to +85?C.  Two package styles provide a magnetically opti-
¡¡¡¡mized package for most applications.  Suffix ¡®LH¡¯ is a miniature low-profile
¡¡¡¡surface-mount package while suffix ¡®UA¡¯ is a three-lead ultra-mini-SIP for
¡¡¡¡through-hole or surface mounting.
¡¡¡¡FEATURES
¡¡¡¡¡ö Micropower Operation
¡¡¡¡¡ö Operate With North or South Pole
¡¡¡¡¡ö 2.5 V to 3.5 V Battery Operation
¡¡¡¡¡ö Chopper Stabilized
¡¡¡¡Superior Temperature Stability
¡¡¡¡Extremely Low Switch-Point Drift
¡¡¡¡Insensitive to Physical Stress
¡¡¡¡¡ö ESD Protected to 5 kV
¡¡¡¡¡ö Solid-State Reliability
¡¡¡¡¡ö Small Size
¡¡¡¡¡ö Easily Manufacturable With Magnet Pole Independence
¡¡¡¡Always order by complete part number: the prefix ¡®A¡¯ + the basic four-digit
¡¡¡¡part number + the suffix ¡®E¡¯ to indicate operating temperature range + a
¡¡¡¡suffix to indicate package style, e.g.,
¡¡¡¡Chopper-Stabilized Technique.  The Hall element can be
¡¡¡¡considered as a resistor array similar to a Wheatstone bridge.  A
¡¡¡¡large portion of the offset is a result of the mismatching of these
¡¡¡¡resistors.  These devices use a proprietary dynamic offset
¡¡¡¡cancellation technique, with an internal high-frequency clock to
¡¡¡¡reduce the residual offset voltage of the Hall element that is
¡¡¡¡normally caused by device overmolding, temperature dependen-
¡¡¡¡cies, and thermal stress.  The chopper-stabilizing technique
¡¡¡¡cancels the mismatching of the resistor circuit by changing the
¡¡¡¡direction of the current flowing through the Hall plate using
¡¡¡¡CMOS switches and Hall voltage measurement taps, while
¡¡¡¡maintaing the Hall-voltage signal that is induced by the external
¡¡¡¡magnetic flux.  The signal is then captured by a sample-and-
¡¡¡¡hold circuit and further processed using low-offset bipolar
¡¡¡¡circuitry.  This technique produces devices that have an
¡¡¡¡extremely stable quiescent Hall output voltage, are immune to
¡¡¡¡thermal stress, and have precise recoverability after temperature
¡¡¡¡cycling.  This technique will also slightly degrade the device
¡¡¡¡output repeatability.  A relatively high sampling frequency is
¡¡¡¡used in order that faster signals can be processed.
¡¡¡¡More detailed descriptions of the circuit operation can be
¡¡¡¡found in: Technical Paper STP 97-10, Monolithic Magnetic
¡¡¡¡Hall Sensor Using Dynamic Quadrature Offset Cancellation
¡¡¡¡and Technical Paper STP 99-1, Chopper-Stabilized Amplifiers
¡¡¡¡With A Track-and-Hold Signal Demodulator.
¡¡¡¡Operation.  The output of this device switches low (turns on)
¡¡¡¡when a magnetic field perpendicular to the Hall sensor exceeds
¡¡¡¡the operate point BOPS (or is less than BOPN).  After turn-on, the
¡¡¡¡output is capable of sinking up to 1 mA and the output voltage
¡¡¡¡is VOUT(ON).  When the magnetic field is reduced below the
¡¡¡¡release point BRPS (or increased above BRPN), the device output
¡¡¡¡switches high (turns off).  The difference in the magnetic
¡¡¡¡operate and release points is the hysteresis (Bhys) of the device.
¡¡¡¡This built-in hysteresis allows clean switching of the output
¡¡¡¡even in the presence of external mechanical vibration and
¡¡¡¡electrical noise.
¡¡¡¡As used here, negative flux densities are defined as less
¡¡¡¡than zero (algebraic convention) and -50 G is less than +10 G