GENERAL DESCRIPTION
The ALD810027/ALD910027 are members of the ALD8100xx
(quad) and ALD9100xx (dual) family of Supercapacitor Auto Balancing
MOSFETs, or SAB™ MOSFETs. SAB MOSFETs are built
with production proven EPAD® technology and 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 leakage-current balanced
by using a combination of one or more devices connected across
each supercapacitor stack to prevent over-voltages.
The ALD810027 offers a set of unique, precise operating voltage
and current characteristics for each of four SAB MOSFET devices,
as shown in its Operating Electrical Characteristics table. It can be
used to balance up to four supercapacitors connected in series.
The ALD910027 has its own set of unique precision Operating Electrical
Characteristics for each of its two SAB MOSFET devices,
suitable for up to two series-connected supercapacitors.
Each SAB MOSFET features a precision gate threshold voltage in
the Vt mode, which is 2.70V when the gate-drain source terminals
(VGS = VDS) are connected together at a drain-source current of
IDS(ON) = 1μA. In this mode, input voltage VIN = VGS = VDS. Different
VIN produces an Output Current IOUT = IDS(ON) characteristic
and results in an effective variable resistor that varies in value
exponentially with VIN. This VIN, when connected across each
supercapacitor in a series, balances each supercapacitor to within
its voltage and current limits.
When VIN = 2.70V is applied to an ALD810027/ALD910027, its
IOUT is 1μA. For a 100mV increase in VIN, to 2.80V, IOUT increases
by about tenfold. For an additional increase in VIN to 2.92V for the
ALD910027 (2.94V for the ALD810027), IOUT increases one hundredfold,
to 100μA. Conversely, for a 100mV decrease in VIN to
2.60V, IOUT decreases to one tenth of its previous value, to 0.1μA.
Another 100mV decrease in input voltage would reduce IOUT to
0.01μA. Hence, when an ALD810027/ALD910027 SAB MOSFET
is connected across a supercapacitor that charges to less than
2.50V, it would dissipate essentially no power.
(Continued on next page)

FEATURES & BENEFITS
• Simple and economical to use
• Precision factory trimmed
• Automatically regulates and balances leakage currents
• Effective for supercapacitor charge-balancing
• Balances up to 4 supercaps with a single IC package
• Balances 2-cell, 3-cell, 4-cell series-connected supercaps
• Scalable to larger supercap stacks and arrays
• Near zero additional leakage currents
• Zero leakage at 0.3V below rated voltages
• Balances series and/or parallel-connected supercaps
• Leakage currents are exponential function of cell voltages
• Active current ranges from <0.3nA to >1000μA
• Always active, always fast response time
• Minimizes leakage currents and power dissipation

VAPPLICATIONS
• Series-connected supercapacitor cell leakage balancing
• Energy harvesting
• Long term backup battery with supercapacitor outputs
• Zero-power voltage divider at selected voltages
• Matched current mirrors and current sources
• Zero-power mode maximum voltage limiter
• Scaled supercapacitor stacks and arrays