HMC6042 Datasheet, PDF (7/7 Pages) Honeywell Solid State Electronics Center – 2-Axis Magnetic Sensor Circuit

HMC6042
stages composed of 400 milli-ohm switches for high efficiency switching of the set and reset currents. The logic input is
expected to be normally high with high-to-low and low-to-high transitions creating reset and set pulses respectively.
Typically, the logic low time between pulses is from a half a millisecond to hundreds of milliseconds to accommodate
reverse polarity sensor measurements as desired. See application notes AN212 and AN213 for further details on nulling
sensor bridge offsets and set/reset strap operation.
To ensure plenty of current at all temperatures, strap load values, and VDD2 supply voltages, a charge pump is designed
into the ASIC to push the reservoir capacitor C1 up to a 3.3 volt value. This pump contains its own 25MHz oscillator and is
current limited to about 1mA draw for modest but quick charges after set and reset pulse usage. When using C1 values of
2.2 to 10 microfarad, only a small amount of voltage drop occurs on C1 and is quickly recharged to its quiescent voltage.
Other than momentary charge pump or set/reset pulse operation, the current draw on VDD2 goes to zero; and can be left
on continuous power supply rails indefinitely.
The choice of C1 and C2 capacitor values is dependant on the quantity and type of sensor set/reset straps used. The
requirement for the set/reset pulse values are one to two microsecond time constant pulses, with C2 and the set/reset
strap load resistance setting the RC time constant. Stand alone, the HMC6042 requires a 0.22 to 0.47 microfarad
capacitor, and with the extra HMC1041Z sensor in parallel the values increase to 0.47 to 1.0 microfarad. C1 is typically
sized at ten times the C2 value to have minimum voltage droop as a C2 charge is extracted from C1.
Amplifiers
Three sensor amplifier sections are designed into the ASIC for the embedded HMC1042 two-axis sensors and an optional
external third axis sensor. The nominal gain of each amplifier section is about 225 V/V with all three amplifiers fairly close
in matched gains. The amplifier sections are broken into two cascaded stages with gains of 22.5 and 10 from input to
output. The second stage has a feedback pin brought out to adjust the gain from unity (output and feedback pins shorted)
to ten (output and feedback pins open). The second stage feedback resistors are nominally 10k-ohms and sections gains
can be trimmed by adding external shunt resistances. Also modest amounts of feedback capacitance can be placed
across the output and feedback pins to lower the bandwidth of the amplifiers for greater EMI immunity.
ORDERING INFORMATION
Ordering Number
HMC6042
HMC6042 T/R 1k
HMC6042 Cut Tape
Product
Two-Axis Magnetic Sensor Circuit
Tape and Reel 1k pieces/reel
Cut Tape
Caution
This part is sensitive to damage
by electrostatic discharge. Use ESD
precautionary procedures when
touching, removing or inserting.
CAUTION: ESDS CAT. 1A
FIND OUT MORE
For more information on Honeywell’s Magnetic Sensors visit us online at www.magneticsensors.com or contact us at
800-323-8295 (763-954-2474 internationally).
The application circuits herein constitute typical usage and interface of Honeywell product. Honeywell does not warranty or assume liability of customer-
designed circuits derived from this description or depiction.
Honeywell reserves the right to make changes to improve reliability, function or design. Honeywell does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
U.S. Patents 4,441,072, 4,533,872, 4,569,742, 4,681,812, 4,847,584 and 6,529,114 apply to the technology described
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