©2014 Advanced Linear Devices, Inc., Vers. 2.0

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GENERAL DESCRIPTION

The ALD8100xx/ALD9100xx family of Supercapacitor Auto Balanc-

ing MOSFET Arrays, or SAB™ MOSFETs, are designed to address

voltage and leakage current balancing of supercapacitors connected

in series. Supercapacitors, also known as ultracapacitors or

supercaps, connected in series can be balanced with single or

multiple ALD8100xx/ALD9100xx packages. These SAB MOSFETs

are built with ALD production proven EPAD

SAB MOSFETs have unique electrical characteristics for superior

active continuous leakage current regulation and self-balancing of

stacked series-connected supercapacitors while dissipating near

zero leakage currents, practically eliminating extra power consump-

tion. For many applications, SAB MOSFET automatic charge bal-

ancing offers a simple, economical and effective method to bal-

ance and regulate supercapacitor voltages. With SAB MOSFETs,

each supercapacitor in a series-connected stack is continuously

monitored and automatically controlled for precise, effective bal-

ancing of its voltage and leakage current.

The SAB MOSFET regulates the voltage across a supercapacitor

cell by increasing its drain current exponentially across the

supercapacitor when its voltage increases, and by decreasing its

drain current exponentially across the supercapacitor when its volt-

age decreases. When a supercapacitor cell is charged to a volt-

age less than 90% of the desired voltage limit, the SAB MOSFET

across the supercap is turned off and there is zero leakage current

contribution from the SAB MOSFET. On the other hand, when the

voltage across the supercapacitor is over the desired voltage limit,

the SAB MOSFET is turned on to increase its drain currents to

keep the supercapacitor voltage from rising. Simultaneously, the

voltages and leakages of other supercapacitors in the series stack

are lowered to result in a near zero net increase in leakage current.

The ALD8100xx/ALD9100xx SAB MOSFET family offers a selec-

tion of different threshold devices for various supercapacitor maxi-

mum operating voltage values and desired leakage balancing char-

acteristics as well as different temperature range environments. A

list of the available ALD part numbers can be found in the tables on

pages 6 and 7 of this document. For individual datasheets and

specifications, please visit www.aldinc.com under “SAB MOSFET”.

SUPERCAPACITORS

Supercapacitors are typically rated with a nominal recommended

working voltage established for long life at their maximum rated

operating temperature. When a supercapacitor cell voltage ex-

ceeds its rated voltage for a prolonged time period, it experiences

reduced lifetime and eventual rupture and catastrophic failure. To

prevent such an occurrence, in most applications having two or

more supercapacitors connected in series, a means of automati-

cally monitoring and adjusting charge-balancing at their maximum

operating voltages is required. This is due to different internal leak-

age currents in each specific cell.

The supercapacitor’s leakage current is a variable function of many

parameters such as aging, initial leakage current at zero input volt-

age, material and construction of the supercapactor, its chemistry

composition, its leakage as a function of the charging voltage and

the charging current and temperature, operating temperature range,

and the rate of change of many of these parameters. Supercapacitor

balancing must correct for these changing effects automatically,

with minimal added leakage currents or power consumption.

ALD8100XX/ALD9100XX FAMILY of SUPERCAPACITOR

SAB MOSFET ADVANTAGES

The ALD8100xx/ALD9100xx family of SAB MOSFETs are designed

for automatic supercapacitor balancing. They are replacements for

many other passive or active supercapacitor balancing methods

where cost, board space, efficiency, simplicity and power dissipa-

tion are important design considerations. For example, in applica-

tions where supercapacitors require minimum long-term power dis-

sipation (internal leakage currents) as a primary goal, ALD8100xx/

ALD9100xx SAB MOSFETs are simpler and more effective in per-

forming the leakage balancing function, using significantly less

board space and contributing no additional charge loss beyond the

supercapacitor’s own leakages. Other common methods of charge

*IC pins are internally connected, connect to V-

PIN CONFIGURATIONS

SCL PACKAGES

ALD8100xx

IC*

V-

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

IC*

V+

V-

V-

M2

M1

M4

M3

V-

V-

SAL PACKAGES

ALD9100xx

V-

1

2

3

4

IC*

V+

6

7

8

5