SUPERCAPACITOR AUTO BALANCING PCB
The ALD9100XX SAB MOSFET family offers the user a selection
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.
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.
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.
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.
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.
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
specificALD9100XX 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.
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.
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.
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.
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.
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.
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
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,
SABMB2/SABMB2XX
Advanced Linear Devices, Inc.
2 of 4
5秒后页面跳转
STM32H743技术深度剖析与应用案例探索
LM321中文资料解析：引脚功能介绍、技术特点、技术特性分析
74HC14芯片资料介绍：性能特性分析、引脚介绍
LM1875芯片手册：功放参数分析、引脚说明、电路设计要点
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
