ICS1700AEB
ICS1700A Evaluation Board
General Description
The ICS1700A Evaluation Board allows quick evaluation of the
ICS1700A Charge Controller for Nickel-Cadmium and Nickel-
Metal Hydride Batteries. The evaluation board provides the
designer an opportunity to both test the ICS1700A and a fast
charge battery charger. The board is self-contained and has
provisions for interfacing with an external constant current source
to charge a battery.
The board includes resistors that are user-installed to customize
operation for the desired charge rate, discharge pulse current, and
number of cells in the battery pack. The board has a 5V regulator
that provides power to the ICS1700A and the LED display. The
board also has a breadboarding area consisting of a matrix of holes
for user added components.
Before using the ICS1700A Evaluation Board, GPI recommends
the user review the ICS1700A data sheet to become familiar with
the operation of the controller.
Setting-up the Board for your
Application
Refer to the evaluation board schematic diagram. The ICS1700A
requires that the battery voltage is normalized to the voltage of one
cell, or about 1.2V. To do this, resistors must be installed in the
locations marked R6 and R8. The appropriate values can be
selected from Table 1. An assortment of resistors is provided with
the board.
Table 1
Cells
R6
R8
1
Open
Short
2
2.0k
2.0k
3
1.0k
2.0k
4
1.0k
3.0k
5
3.0k
12k
6
2.0k
10k
7
2.0k
12k
8
1.3k
9.1k
If the evaluation board is used with battery packs containing more
than eight cells, the resistors can be determined by counting the
number of cells to be charged in series. Then choose either R6 or
R8 and solve for the other resistor using:
R8 = R6* (# of cells -1) or R6 = R8
(# of cells -1)
The ICS1700A controller has an internal 2.0V reference used to
detect the removal of the battery from the charging system. For
most batteries, the maximum normalized battery voltage at the VIN
pin at full charge is 1.7 to 1.8V. The voltage at VIN is compared to
the 2.0V reference voltage when the current source is turned on. If
the voltage at VIN is greater than the 2.0V reference, the
ICS1700A assumes the battery has been removed and the
ICS1700A indicates a fault condition by turning on the BF LED,
and shuts down.
When power is applied to the board, the controller will start a
charge sequence unless a logic low is applied to the RESET
terminal. When RESET is removed by a logic high or open, a
charge sequence will begin.
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ICS1700A Evaluation Board
The board provides several low value resistors that may be used to
set the amplitude of the discharge pulse. The resistors can be
installed in any or all of the locations labeled R1, R2, or R3. The
resistor value is calculated by setting the amplitude of the
discharge pulse. The discharge pulse amplitude is typically 2.5
times the charge current based on 1.4V/cell. The resistor locations
R1, R2, and R3 are connected in series. The unused locations must
have a jumper to complete the circuit. Not using the discharge
pulse feature will not affect the performance of the ICS1700A.
The ICS1700A is capable of operating at four different charge
rates; 4C (15 minutes), 2C (30 minutes), 1C (60 minutes) and C/2
(120 minutes). The charge rate is selected by SW1 dip switch
settings. Table 2 shows the proper settings to use for the desired
charge rate.
Power Requirements
The evaluation board uses a regulator to provide +5 volts for the
controller. The regulator allows operation from a DC supply of 8 to
32 volts when the supply is connected to the +V terminal. The
board may also be operated from an external 5 volt supply by
removing the regulator (VR1), wiring a jumper between regulator
pins 1 and 3, and by connecting 5 volts directly to the +5V
terminal.
Connections To External Circuitry
A normally closed thermal switch or a thermistor should be
connected to the TS terminal. If a thermal protection device is not
used, the TS terminal must be grounded.
Connect the battery between the +BAT and GND terminals.
Connect the external charging current source and its return between
the +CUR and GND terminals.
Two charge signals are provided to control external charging
circuitry. CHARGE is high when the charging current is on. The
other signal CHARGE is low when the charging current is on.
The charging circuitry should provide a current at an amplitude
that is equal to the product of the battery capacity and the desired
charge rate. For example, to charge a 1.2 ampere hour battery in 30
minutes, the current required would be 2.4 amps or 2C where `C' is
the battery capacity.
It is important to note that the ICS1700A does not control the
current flowing into the battery in any way other than turning it on
and off. The charging source should be a constant current type.
Table 2: Charge Rate List
Charge Rate
SW1-1
(S0)
SW1-2
(S1)
Topping Charge pulse
Rate
Maintenance Charge
Pulse Rate
Fast Charge Timer
Duration (after reset)
4C (15 min)
ON
ON
one every 40 sec
one every 160 sec
30 min
2C (30 min)
ON
OFF
one every 20 sec
one every 80 sec
60 min
1C (60 min)
OFF
ON
one every 10 sec
one every 40 sec
90 min
C/2 (120 min)
OFF
OFF
one every 5 sec
one every 20 sec
210 min
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ICS1700A Evaluation Board
The charge pulses repeat for 10 seconds. If the battery is installed
within 10 seconds, the ICS1700A will turn off the BF LED and
enter the fast charge stage. If the battery is not installed within 10
seconds, the BF LED remains on and the
ICS1700A shuts down. A reset must be issued to restart the
controller after installing the battery.
Battery Fault Detection
The ICS1700A will turn on the BF LED and shut down if the
battery is removed or if an open circuit occurs in the current path
anytime after fast charge has been initiated. When in the topping
charge or maintenance charge stages, a charge pulse may not occur
for several seconds. During the period between charge pulses, the
voltage at VIN should be greater than 0.5V if a battery is attached.
If the voltage at VIN is less than 0.5V, the ICS1700A assumes the
battery has been removed, a fault condition is indicated by the BF
LED, and the controller shuts down.
Out-of-Temperature Range
The OT LED activates if the battery is either too hot or too cold to
fast charge. If a thermistor is used, the ICS1700A employs internal
voltage references to determine if a battery is hot or cold. Note:
Remove R9 and replace with a jumper when using a thermistor. A
10k
@ 25
C thermistor with an external pull-up resistor is
typically used. See the ICS1700A data sheet for additional
information.
If a thermal switch is used, choose a switch that opens at 45
C or
lower. If a thermal protection device is not used, the TS terminal
must be grounded.
ICS strongly recommends the use of a thermal safety device in the
battery pack. One source of thermal switches is Portage Electric
Products, Inc., in North Canton, Ohio; (216) 499-2727. A source of
thermistors is Semetic USA (Ishizuka Electronics Corp.), Babylon,
NY; (516) 587-4086.
Operation
Before applying power to the board, ensure that the board is
properly initialized.
Set SW1-1 and SW1-2 for the correct charge rate.
Check to make sure the divider resistors R6 and R8 are of the
correct value to normalize the battery pack voltage to one cell.
If applicable, choose resistors R1, R2 and R3 to obtain the
required discharge current.
After applying power to the board:
Set the external charging current source for the amplitude
required by SW1 settings.
Push and hold the reset switch SW2 for at least 700ms. All LEDs
should turn off while the switch is depressed. The green CM LED
will light and will remain lit until full charge is detected by the
ICS1700A. At that moment, the CM LED will start flashing at a 1
Hz rate, indicating that the topping charge stage has begun. The
CM LED will flash until a reset is issued either by interrupting the
power, removing the batteries or depressing the reset switch SW2.
Battery Polling
Upon power-up or after a reset is issued, any excess charge from
filter capacitors at the +BAT and +CUR terminals is removed with
a series of discharge pulses. After the discharge pulse series is
complete, the voltage at VIN must be greater than 0.5V when a
battery is present. If the voltage at VIN is less than 0.5V, the
ICS1700A assumes no battery is attached and initiates a polling
sequence.
The ICS1700A then applies a 100ms charge pulse. During the
pulse, the ICS1700A monitors the VIN pin to determine if the
divided down terminal voltage is greater than the internal 2.0V
reference. If the battery is present, the voltage is clamped below the
2.0V reference when the current pulse is applied and the fast
charge stage begins immediately. If a battery is not present, the
voltage at VIN rises above the 2.0V reference and the BF LED
lights immediately.
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ICS1700A Evaluation Board
Design Considerations
When designing external current source circuitry for use with the
ICS1700A, there are several important considerations to make
before starting the design and the PC board layout.
For the 2C and 4C charge rates, consideration has to be given to
the use of a pulse-width modulated switch mode current source in
order to reduce size and power dissipation. Switch mode current
sources can provide the ability to charge battery packs that require
voltages higher than the primary supply. For instance, to charge a
24 volt battery from a 12 volt vehicle battery, a switch mode boost
converter could be used.
In general, linear chargers are less complex and more cost
effective, but less efficient than switch mode chargers. For the 1C
and C/2 charge rates, consideration should be given to using a
linear charger unless the size and ability to dissipate heat are not
available.
It is very important that care be taken to minimize noise coupling
and ground bounce. In addition, wires and connectors can add
significant resistance and inductance to the charge and discharge
circuits.
When designing the printed circuit board, make sure ground and
power traces are wide and bypass capacitors are used right at the
controller pins. Use separate grounds for the signal, charge, and
discharge circuits. Separate ground planes on the component side
of the PC board are recommended. Be sure to connect these
grounds together at the negative lead of the battery only.
For the discharge circuit, keep the physical separation between
power and return (ground) to a minimum to minimize field
radiation effects. This precaution is also applicable to the constant
current source, particularly if it is a switch mode type. Keep the
ICS1700A and the constant current source control circuits outside
the power and return loops described above. These precautions
prevent high circulating currents and coupled noise from disturbing
proper operation.
Galaxy Power, Incorporated wants to help create a successful
battery charging solution using the ICS1700A. If you need
technical advice or applications information, call the Intelligent
Charging Solutions hotline at GPI, (610) 676-0188 x-277.
Device type:
ICS1700A Evaluation Board
Ordering Information
ICS1700AEB
5
ICS1700A Evaluation Board
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ICS1700A Evaluation Board
NOTES
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ICS1700A Evaluation Board
NOTES
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