SABMB16/SABMB810025/SABMB910025

Advanced Linear Devices, Inc.

3 of 4

SABMB8100XX/SABMB9100XX

SUPERCAPACITOR AUTO BALANCING PCB

maximizing any energy harvesting gathering efforts. The SAB

MOSFET would not become active until the supercapacitor is

already charged to over 90% of its max. rated voltage. The trickle

charging of supercapacitors with energy harvesting techniques

tends to work well with SAB MOSFETs as charge balancing

devices, as it is less likely to have high transient energy spurts

resulting in excessive voltage or current excursions.

If an energy harvesting source only provides a few µA of current,

the power budget does not allow wasting any of this current on

capacitor leakage currents and power dissipation of resistor or

operational amplifier based charge-balancing circuits. It may also

be important to reduce long term leakage currents, as energy

harvesting charging at low levels may take up to many days.

In summary, in order for an energy harvesting application to be

successful, the input energy harvested must exceed all the energy

required due to the leakages of the supercapacitors and the charge-

balancing circuits, plus any load requirements. With their unique

balancing characteristics and near-zero charge loss, SAB

MOSFETs are ideal devices for use in supercapacitor charge-

balancing in energy harvesting applications.

BATTERY POWERED APPLICATIONS

Many battery powered circuits that also require supercapacitor at

its output to boost power output can benefit from using SAB

MOSFETs for supercapacitor balancing. As previously described,

the additional power burn by using SAB MOSFETs for

supercapacitor stack balancing can be negative, meaning that

adding SAB MOSFETs can not only not burn extra power, but can

actually save supercapacitor leakage current and associated power

dissipation. Applications that depend on long life battery usage

must take into account the supercapacitor leakage current and

balancing circuit power burn because the currents involved are

steady state DC currents that are continuous throughout the lifetime

of the application and its battery life. The average power dissipation

of addition of SABMB16 board is zero, provided the selection of

the operating voltages and SAB MOSFETs are appropriate for the

leakage currents of the supercapacitors specified.

For more information on the CHARACTERISTICS OF

SUPERCAPACITOR AUTO BALANCING (SABª) MOSFETS,

please refer to the document:

ALD8100XX/ALD9100XX FAMILY of SUPERCAPACITOR AUTO

of each of the SAB MOSFETs.

SABMB16 PCB CONNECTION TO

SUPERCAPACITORS C1, C2, C3, C4

C1

C2

C3

C4

A

A

B

B

C

C

D

D

E

E

V

R

R

U

U

V

V

TO NEXT BOARD V

V TO NEXT BOARD V

C1

C2

C3

C4

A

A

B

B

C

C

D

D

E

E

V

R

R

U

U

V

V

TO NEXT BOARD V

V TO NEXT BOARD V

* Magnified, not to scale