HMC1051/HMC1052/HMC1053

10

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Three Axis Compassing with Tilt Compensation

For full three-axis compassing, the circuit depicted in Figure 7 shows both a HMC1051 and a HMC1052 used for sensing

the magnetic field in three axes. Alternatively a single HMC1053 could be used for a single sensor package design. A

two-axis accelerometer with digital (PWM) outputs is also shown to provide pitch and roll (tilt) sensing, to correct the

three-axis magnetic sensors outputs into to the tilt-compensated two-axis heading. The accelerometer can be substituted

with a fluidic 2-axis tilt sensor if desired. For lower voltage operation with Lithium battery supplies (2.5 to 3.6Vdc), the

Set/Reset circuit should be upgraded from a single IRF7507 to the dual IRF7507 implementation (per Figure 2) to permit

a minimum 1-ampere pulse (500mA per set/reset strap resistance) to both the HMC1052 and HMC1051 sensors.

Duty Cycling for Lower Energy Consumption

For battery powered and other applications needing limited energy consumption, the sensor bridge and support

electronics can be s

witched “off” between magnetic field measurements. The HMC105X family of magnetic sensors are

very low capacitance (Bandwidth > 5MHz) sensor bridges and can stabilize quickly, typically before the support

electronics can. Other energy saving ideas would be to minimize the quantity of set/reset pulses which saves energy over

the battery life. Figure 8 shows a simple supply switching circuit that can be microprocessor controlled to duty cycle

(toggle) the electronics in moderate current (<25mA) applications.

HMC1052

U1

Vcc

offset

set/reset

.1uf

IRF7509

set/reset

Vcc/2

Vcc/2

5.00k

5.00k

500k

500k

5.00k

5.00k

500k

500k

LMV324

LMV324

1nf

1nf

U3

U4

3.3 to 5.0v

HMC1051

U2

Vcc

Vcc/2

5.00k

5.00k

500k

500k

LMV324

.1 f

+

-

set/reset

C

with

Multiplexed

A/D Conv.

AN0

AN1

AN2

AN3

Vcc/2

U6

U5

xout

yout

Two-axis

accelerometer

Vcc

Vcc

DO0

DI0

DI1

HMC1052

U1

Vcc

offset

set/reset

.1uf

IRF7509

set/reset

Vcc/2

Vcc/2

5.00k

5.00k

500k

500k

5.00k

5.00k

500k

500k

LMV324

LMV324

1nf

1nf

U3

U4

3.3 to 5.0v

HMC1051

U2

Vcc

Vcc/2

5.00k

5.00k

500k

500k

LMV324

.1 f

+

-

set/reset

C

with

Multiplexed

A/D Conv.

AN0

AN1

AN2

AN3

Vcc/2

U6

U5

xout

yout

Two-axis

accelerometer

Vcc

Vcc

DO0

DI0

DI1

Figure 7

Three Axis Compass