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SABMB2/SABMB2XX
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EPAD
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2-CHANNEL SUPERCAPACITOR AUTO BALANCING PCB
GENERAL DESCRIPTION
The SABMB2 is a 2-channel Printed Circuit Board (PCB) designed
to be used with any member of the ALD9100XX family of
SAB™
MOSFETs
for system designers and application developers. SAB
MOSFETs are exclusive EPAD MOSFETs that address leakage
and voltage balance of supercapacitor cells connected in series.
Imbalance of leakage currents, although much smaller in
magnitude than charging or discharging currents, need to be
balanced, as leakage currents are long-term DC values that
integrate and accumulate over time. SAB MOSFETs and the
SABMB2 boards are compact, economical and effective in
balancing any size supercapacitors with little or no additional power
dissipation. Each SABMB2 can balance two supercapacitors in a
series stack. It is the newest board to join the popular SABMB16,
which can balance two to four supercapacitors in a series stack.
These boards can be cascaded to balance multiple series stacks
of two supercapacitors each.
®
The SABMB2 is a blank PCB, ready for an ALD9100XX to be
installed. For example, the SABMB225 is an SABMB2 board with
an ALD910025SALI installed and tested. These are rated for
industrial tempurature of
-40°C to +85°C.
The SABMB2 board includes the following features for flexibility
in a variety of different applications:
1)
2)
One ALD9100XX Dual SAB MOSFET unit installed per
board.
Optional reverse biased external clamping power diodes
(schottky rectifiers) can be installed, on board where
necessary, across each SAB MOSFET.
Multiple SABMB2 PCBs can be cascaded to form a series
chain, paralleling a series-connected chain of
supercapacitor cells.
Compact size of 0.6 in. by 1.0 in. with mounting holes
Rated for RoHS compatible/industrial temperature range
of
-40°C to +85°C
3)
The SABMB2 is a simple, out-of-the-box plug-and-play PCB
solution for development, prototyping, demonstration and
evaluation, or production deployment. It is suited for balancing
supercapacitor stacks ranging from two in series to hundreds in
series, and for supercapacitors of 0.1F to 3000F and beyond. The
average additional power dissipation due to use of SABMB boards
is zero, which makes this method of supercapacitor balancing
very energy efficient. It is especially suited for low loss energy
harvesting and long life battery operated applications.
Supercapacitors, also known as ultracapacitors, when connected
two cells in series can be balanced with a single ALD9100XX
package installed. Supercapacitors, when connected more than
two cells in series, can be balanced with more than one SABMBXX
board (each with ALD9100XX packages installed).
4)
5)
MECHANICAL DRAWING
V+
A
SABMB2
ORDERING INFORMATION
Part Number
SABMB2
SABMB2XX
Example:
SABMB225
Description
Blank Universal PCB ready for one
ALD9100xx Dual SAB MOSFET
SABMB2 Board with one
ALD9100XXSALI
SABMB2 Board with one
ALD910025SALI
A
1000 mil
B
B
C
U1
V-
C
Note: SABMB2XX is optional with a specific
ALD9100XXSALI unit installed. XX = 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28.
See page 4 for full listing of part numbers.
600 mil
* Magnified, not to scale
©2018 Advanced Linear Devices, Inc., Vers. 1.0
www.aldinc.com
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SUPERCAPACITOR AUTO BALANCING PCB
The ALD9100XX SAB MOSFET family offers the user a selection
of different threshold voltages for various supercapacitor nominal
operating voltage values and desired leakage balancing
characteristics. Each SAB MOSFET generally requires connecting
its V+ pin to the most positive voltage and its V- and IC pins to the
most negative voltage within the package. Note that each Drain
pin has an internal reverse biased diode to its Source pin, and
each Gate pin has an internal reverse biased diode to V-. All
other pins must have voltages within V+ and V- voltage limits within
the same package unit.
Standard ESD protection facilities and handling procedures for
static sensitive devices must also be used while installing the
ALD9100XX units. Once installed, the connection configuration
will protect the ALD9100XX units from ESD damage. When
connected to a supercapacitor stack, the ALD9100XX is further
protected from virtually any ESD damage due to the large
capacitance of the supercapacitors, which sinks any ESD charge
and thereby reduces any of the terminal voltages to minimal
harmless values.
temperature and heat dissipation considerations, when selecting
a suitable component for such purpose. The appropriate level of
derating and margin allowance must also be added to assure long
term reliability of the PCB board.
SUPERCAPACITORS
Supercapacitors are typically rated with a nominal recommended
working voltage established for long life at their maximum rated
operating temperature. Excessive supercapacitor voltages that
exceed the supercapacitor’s rated voltage for a prolonged time
period will result in reduced operating life and eventual rupture
and catastrophic failure. To prevent such an occurrence, a means
of automatically adjusting (charge-balancing) and monitoring the
maximum voltage is required in most applications having two or
more supercapacitors connected in series, due to the different
internal leakage currents that vary from one supercapacitor to
another.
Each supercapacitor has a tolerance difference in capacitance,
internal resistance and leakage current. These differences create
imbalance in cell voltages, which must be balanced so that any
individual cell voltage does not exceed its rated max. voltage.
Initially, cell voltage imbalance is caused by capacitance value
differences. Supercapacitors selected from the same manufacturer
make and model batch can be measured and matched to deliver
reasonable initial cell voltages. Next, cell voltage imbalance due
to individual cell leakage currents must be compensated.
The supercapacitor leakage current itself is a variable function of
its many parameters such as aging, initial leakage current at zero
input voltage, the material/construction of the supercapacitor, and
the operating bias voltage. Its leakage is also a function of the
charging voltage, the charging current, operating temperature
range and the rate of change of many of these parameters.
Supercapacitor balancing must accommodate these changing
conditions.
By using the appropriate ALD SAB MOSFET and the appropriate
SABMBXX board, users can compensate for all of these causes
of imbalance and automatically balance supercapacitors.
SABMB2 PRINTED CIRCUIT BOARDS
The SABMB2 Printed Circuit Board is available as a blank PCB
board, made with RoHS compliant FR4 material, ready for
mounting one 8-lead ALD9100XX unit. These units are also
supplied and available with a 2-digit suffix, which denotes the
specific ALD9100XX component mounted and tested on the PCB.
All that is required of the user is to mount the PCB and wire the
appropriate connections from the SABMB2 board to the respective
supercapacitor nodes.
Each SABMB2 Printed Circuit Board has a single 8-lead SOIC
footprint and terminals labeled V+, A, B, C and V-. Each of these
terminals has two wiring holes for easier connection of the same
terminal node to two external connection points. V+ is directly
connected to terminal A, which must be connected to the most
positive voltage for the individual SABMB2 board. V- is directly
connected to terminal C, which must be connected to the most
negative voltage present for the same SABMB2 board. The other
terminal, namely B, must have voltages between V+ and V- for
proper operation of the board.
When two supercapacitors are installed to be balanced by SAB
MOSFETs, a single ALD9100XX unit can be mounted on the
SABMB2. Any number of SABMB2 boards can be daisy-chain
connected in series. For example, three SABMB2 boards, each
with an ALD910025SALI installed, can be connected in series to
a +15V power supply, provided care is taken to insure that each
SABMB2 board V- is connected to the V+ of the next SABMB2
board in series, such that each board would have typical internal
voltages from V+ to V- of +5.0V.
The ALD9100XX is rated for reverse bias diode currents of up to
80mA maximum for each SAB MOSFET on board. Any reverse
bias condition as a result of changing supercapacitor voltages,
especially during fast supercapacitor discharge, could lead to some
internal nodes temporarily reverse biased with surge current in
excess of this limit. The SABMB2 board has additional optional
TO277 footprints for mounting external schottky rectifiers (power
diodes) to clamp such surge current transients. The user is advised
to determine the various power and current limits, including
SABMB2/SABMB2XX
ENERGY HARVESTING APPLICATIONS
Supercapacitors offer an important benefit for energy harvesting
applications using a low energy source, by buffering and storing
such energy to drive a higher power load.
For energy harvesting applications, supercapacitor leakage
currents are a critical factor, as the average energy harvesting
input charge must exceed the average supercapacitor internal
leakage currents in order for any net energy to be harvested and
saved. Often, the input energy is variable, meaning that its input
voltage and current magnitude are not constant and may be
dependent upon a whole set of other parameters such as the
source energy availability, energy sensor conversion efficiency,
changing environmental conditions, etc.
SAB MOSFETs used for charge balancing, due to their high input
threshold voltages, are completely turned off initially, consuming
zero drain current while the supercapacitor is being charged,
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Advanced Linear Devices, Inc.
SUPERCAPACITOR AUTO BALANCING PCB
maximizing any energy harvesting gathering efforts. The SAB
MOSFET does 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.
CAUTION:
Users must limit the voltage across any ALD9100XX chip to
15.0V max.
SABMB2 PCB CONNECTION TO
SUPERCAPACITORS C1, C2
V+
V+
A
SABMB2
VA
C1
VB
C2
VC
A
B
B
C
U1
V-
C
BATTERY POWERED APPLICATIONS
Many battery powered circuits requiring a supercapacitor to boost
power output can benefit from using SAB MOSFETs for
supercapacitor balancing. The additional power burn by using
SAB MOSFETs for supercapacitor stack balancing can actually
be negative, as adding SAB MOSFETs can save supercapacitor
leakage current and associated power dissipation by lowering the
operating bias voltage of the leakier supercapacitor. 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 added power dissipation with the addition
of the SABMB2 board is zero, provided the selection of the
operating voltages and SAB MOSFETs are appropriate for the
leakage currents of the supercapacitors specified.
V- TO NEXT BOARD V+
V+ TO NEXT BOARD V-
V+
A
SABMB2
VA
C1
VB
C2
VC
A
B
B
C
U1
V-
C
CONNECTION TO OTHER SABMBXX PCBs
V- TO NEXT BOARD V+
The SABMB2 is compatible with other SABMBXX boards and is
designed to be used along with other SABMBXX boards connected
in series to achieve balancing the corresponding number of
supercapacitors installed in a series stack. For example, five
supercapacitors in series can be balanced with one SABMB2 PCB
and one SABMB16 PCB connected in series.
For more information on the CHARACTERISTICS OF
SUPERCAPACITOR AUTO BALANCING (SAB
TM
) MOSFETS,
please refer to the following documents:
* ALD8100XX/ALD9100XX FAMILY of SUPERCAPACITOR
AUTO BALANCING (SAB
TM
) MOSFET ARRAYS
* Individual datasheet for chosen SAB MOSFET.
V+ TO NEXT BOARD V-
V+
A
SABMB2
VA
C1
VB
C2
VC
A
B
B
C
U1
V
* Magnified, not to scale
C
SABMB2/SABMB2XX
Advanced Linear Devices, Inc.
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SUPERCAPACITOR AUTO BALANCING PCB
SABMB2 SCHEMATIC DIAGRAM
< +15.0V
IDS(ON) < 80 mA
ALD9100XX
U1
3, 8
2
V+
OPTIONAL
VA
+
D1
C1
VB
+
D2
C2
VC
V-
M1
4
6
7
M2
1, 5
NOTES
1. U1: 8L SOIC ALD9100XXSALI
2. D1, D2: OPTIONAL SCHOTTKY
RECTIFIER FOR REVERSE CURRENT
CLAMPING (TO277 FOOTPRINT)
3. C1, C2: SUPERCAPACITORS
EXTERNAL TO THE SABMB2 PCB
PCB PRODUCT PART NUMBERS
SABMB2
SABMB216
SABMB217
SABMB218
SABMB219
SABMB220
SABMB221
SABMB222
SABMB223
SABMB224
SABMB225
SABMB226
SABMB227
SABMB228
(blank PC Board)
(SAMB2 with one ALD910016SALI)
(SAMB2 with one ALD910017SALI)
(SAMB2 with one ALD910018SALI)
(SAMB2 with one ALD910019SALI)
(SAMB2 with one ALD910020SALI)
(SAMB2 with one ALD910021SALI)
(SAMB2 with one ALD910022SALI)
(SAMB2 with one ALD910023SALI)
(SAMB2 with one ALD910024SALI)
(SAMB2 with one ALD910025SALI)
(SAMB2 with one ALD910026SALI)
(SAMB2 with one ALD910027SALI)
(SAMB2 with one ALD910028SALI)
SABMB2/SABMB2XX
Advanced Linear Devices, Inc.
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