ICS1722
QuickSaver® Charge Controller for Nickel-Cadmium
and Nickel-Metal Hydride Batteries
General Description
Features
•
The ICS1722 is a CMOS device designed for the intelligent charge
control of either nickel-cadmium (NiCd) or nickel-metal hydride
(NiMH) batteries. The controller uses a pulsed-current charging
technique together with voltage slope termination. The ICS1722
employs a four stage charge sequence that provides a complete
recharge without overcharging. The controller has nine userselectable charge rates and six user-selectable auxiliary modes
available for customized charging systems.
•
•
•
•
•
•
The ICS1722 monitors for the presence of a battery and begins
charging when a battery is installed. The ICS1722 is for
applications where temperature sensing is not required by the
charge controller.
Applications
Battery charging systems for:
- Portable consumer electronics
- Power tools
- Audio/video equipment
- Communications equipment
•
Charge termination methods include:
Voltage slope
Charge timers
Four stage charge sequence:
Soft start charge
Fast charge
Topping charge
Maintenance charge
Reverse-pulse charging available in all charge stages
Nine programmable charge rates between 15 minutes (4C)
and four hours (C/4)
Continuous polling mode for battery detection
Six auxiliary modes include:
Discharge-before-charge
Ten hour C/10 conditioning charge
Direct to C/40 maintenance charge
Charging system test provided through controller
Adjustable open circuit (no battery) voltage reference
Block Diagram
RESET
OPEN CIRCUIT
REFERENCE
POLLING
MODE LED
MICROCODE CONTROL
CHARGE
MODE LED
0.5V
VOLTAGE
SENSE
ADC
PROCESSOR
MODE SELECT
CHARGE
SELECT
RC
RAM
ROM
OSCILLATOR
OUTPUT
CONTROL
MAINTENANCE
MODE LED
CHARGE
CONTROL
DISCHARGE
CONTROL
ICS1722
Pin Configuration
CHG
1
16
VDD
DCHG
2
15
unused
PFN
3
14
VIN
MMN
4
13
OPREF
CMN
5
12
AUX1
SEL0
6
11
AUX0
VSS
7
10
RC
SEL1
8
9
ICS1722
MRN
16-Pin DIP or SOIC
Pin Definitions
Pin Number
1
Pin Name
CHG
Type
OUT
2
3
DCHG
PFN
OUT
OUT
4
MMN
OUT
5
CMN
OUT
6
7
8
9
10
11
12
13
SEL0
VSS
SEL1
MRN
RC
AUX0
AUX1
OPREF
IN
14
15
16
VIN
unused
VDD
IN
Note:
Definition
Active high TTL compatible signal used to turn on an external current source to provide current to charge
the battery.
Active high TTL compatible signal available to turn on a discharge circuit.
Polling detect indicator. An active low turns on an external indicator to show the controller is polling for
the presence of the battery.
Maintenance mode indicator. An active low turns on an external indicator showing the battery is either in
the topping charge, maintenance charge or auxiliary condition mode. The indicator flashes during the
auxiliary discharge mode.
Charge mode indicator. An active low turns on an external indicator to show the controller is either in a
soft start charge or fast charge.
Tri-level input used with the SEL1 pin to program the device for the desired charge rate.
Ground.
IN
IN
IN
IN
IN
IN
Tri-level input used with the SEL0 pin to program the device for the desired charge rate.
Master reset signal. A logic low pulse greater than 700 ms initiates a device reset.
An external resistor and capacitor sets the frequency of the internal clock.
Tri-level input used with the AUX1 pin to program the device for an auxiliary operating mode.
Tri-level input used with the AUX0 pin to program the device for an auxiliary operating mode.
Open circuit (no battery) voltage reference. An external resistor divider on this pin sets the open circuit
voltage reference used to detect the presence of a battery.
Battery voltage normalized to one cell with an external resistor divider.
Ground.
Device supply =+5.0 VDC
Pins 9 and 13 have an internal pull-up.
Pins 6,8,11,12 float to 2.3V when unconnected.
2
ICS1722
Soft Start Charge
Controller Operation
Some batteries may exhibit an unusual high impedance condition
while accepting the initial charging current, as shown in Figure 2.
Unless dealt with, this high impedance condition can cause a
voltage peak at the beginning of the charge cycle that would be
misinterpreted as a fully charged battery by the voltage termination
methods.
Charging Stages
The charging sequence consists of four stages. The application of
current is shown graphically in Figure 1. The soft start stage
gradually increases current levels up to the user selected fast
charge rate during the first two minutes. The soft start stage is
followed by the fast charge stage, which continues until
termination. After termination, a two hour C/10 topping charge is
applied. The topping charge is followed by a C/40 maintenance
charge.
Average
Current
(not to scale)
S oft-Start
Fast Charge
Stage 1
0
2 min
The soft start charge eases batteries into the fast charge stage by
gradually increasing the current to the selected fast charge rate. The
gradual increase in current alleviates the voltage peak. During this
stage, only positive current pulses are applied to the battery. The
duty cycle of the applied current is increased to the selected fast
charge rate, as shown in Figure 3, by extending the current pulse
on every cycle until the pulse is about one second in duration. The
initial current pulse is approximately 200ms. The CMN indicator is
activated continuously during this stage
Topping Charge
Stage 2
Maintenance Charge
Stage 3
termination
Stage 4
termination + 2 hours
Time (not to scale)
Figure 1: Graphical representation of average current levels during the four charging stages
Figure 2: High impedance voltage spike at the beginning of charge
3
ICS1722
Initial Pulse
Width
Initial Pulse
Width
Initial Pulse
Width
2 x increment
time
increment
time
cycle time
cycle time
cycle time
Figure 3: Cycle-to-cycle increase of the soft-start current pulse widths
Fast Charge
The amplitude of the current pulse is determined by system
parameters such as the current capability of the charging system,
the desired charge rate, the cell capacity and the ability of that cell
to accept the charge current. The ICS1722 can be set for nine userselectable fast charge rates from 15 minutes (4C) to four hours
(C/4). Charge pulses occur approximately every second. The CMN
indicator is activated continuously during this stage.
In the second stage, the ICS1722 applies the charging current in a
series of charge and discharge pulses. The technique consists of a
positive current charging pulse followed by a high current, short
duration discharge pulse. The cycle, shown with charge, discharge,
rest and data acquisition periods in Figure 4, repeats every second
until the batteries are fully charged.
rest
time
rest
time
voltage
acquisition time
fast charge pulse width
discharge pulse width
cycle time
Figure 4: Charge cycle showing charge and discharge current pulses
4
ICS1722
Topping Charge
The discharge current pulse amplitude is typically set to about 2.5
times the amplitude of the charging current based on 1.4V/cell. For
example, if the charge current is 4 amps, then the discharge current
is set at about 10 amps. The energy removed during the discharge
pulse is a fixed ratio to the positive charge rate. The amplitude of
the discharge pulse does not affect the operation of the part as
described in this section.
The third stage is a topping charge that applies current at a rate low
enough to prevent cell heating but high enough to ensure a full
charge.
The topping charge applies a C/10 charging current for two hours.
The current consists of the same pulse technique used during the
fast charge stage; however, the duty cycle of the pulse sequence
has been extended as shown in Figure 5. Extending the time
between charge pulses allows the same charging current used in the
fast charge stage so that no changes to the current source are
necessary. For example, the same charge pulse that occurs every
second at a 2C fast charge rate will occur every 20 seconds for a
topping charge rate of C/10. The MMN indicator is activated
continuously during this stage.
A voltage acquisition window immediately follows a brief rest time
after the discharge pulse. No charge is applied during the rest time
or during the acquisition window to allow the cell chemistry to
settle. Since no current is flowing, the measured cell voltage is not
obscured by any internal or external IR drops or distortions caused
by excess plate surface charge. The ICS1722 makes one
continuous reading of the no-load battery voltage during the entire
acquisition window. The voltage that is measured during this
window contains less noise and is a more accurate representation
of the true state of charge of the battery.
cycle
time
Maintenance Charge
The maintenance charge is intended to offset the natural selfdischarge of NiCd or NiMH batteries by keeping the cells primed
at peak charge. After the topping charge ends, the ICS1722 begins
this charge stage by extending the duty cycle of the applied current
pulses to a C/40 rate. The maintenance charge will last for as long
as the battery voltage is greater than 0.5V at the VIN pin, or, if the
ten hour timer mode is enabled, until the timer stops the controller.
The MMN indicator is activated continuously during this stage.
delay time
cycle
time
Figure 5: Representative timing diagram for topping and maintenance charge
5
ICS1722
Cells that are not thoroughly conditioned or possess an unusual cell
construction may not have a normal voltage profile. The ICS1722
uses an alternate method of charge termination based on a slight
decrease in the voltage slope to stop charge to cells whose voltage
profile is very shallow. This method looks for a flattening of the
voltage slope which may indicate a shallow peak in the voltage
profile. The zero slope point occurs slightly beyond the peak
voltage and is shown on the voltage curve graph.
Charge Termination Methods
Charge termination schemes include voltage slope, fast charge
timer and, if desired, a ten hour timer to limit total charge time.
Voltage Slope Termination
The most distinctive point on the voltage curve of a charging
battery in response to a constant current is the voltage peak that
occurs as the cell approaches full charge. By mathematically
calculating the first derivative of the voltage, a second curve can be
generated showing the change in voltage with respect to time as
shown in Figure 6. The slope will reach a maximum just before the
actual peak in the cell voltage. Using the voltage slope data, the
ICS1722 calculates the point of full charge and accurately
terminates the applied current as the battery reaches that point. The
actual termination point depends on the charging characteristics of
the particular battery.
Charge Timer Termination
The controller uses a timer to limit the fast charge duration.
These times are pre-programmed, and are automatically adjusted in
time duration according to the charge rate selected. Fast charge
timer termination is a safety backup feature to limit the duration of
the fast charge stage. The fast charge timer is always enabled and
cannot be disabled. See Table 3 in the section Charge Rate
Selection for more information. To limit the total charge time to ten
hours, refer to the section Ten Hour Timer Mode for more
information.
Figure 6: Voltage and slope curves showing inflection and zero slope points
6
ICS1722
Battery Detection
Discharge-to-Charge Mode
Upon power-up or after a master reset, excess charge from output
filter capacitors at the charging system terminals is removed with a
series of discharge pulses. After the discharge pulse sequence is
complete, the voltage at VIN must be greater than 0.5V when a
battery is present. If the voltage at the pin is less than 0.5V, the
ICS1722 assumes no battery is present, and the polling detect
mode is initiated. No indicator is active during the discharge
pulses.
The time required for discharge depends on the energy in the battery
and the discharge rate. The discharge is not limited by a timer. This
allows the user to set the discharge rate. The battery is drained to 1
volt/cell as read at the VIN pin under load and then the controller
enters soft start at a charge rate set by the SEL0 and SEL1 inputs. The
discharge load is activated by the DCHG pin which goes low for about
400ms every second. A resistor value selected for a 2.5C discharge
based on
1.4V/cell results in about a 1C discharge rate.
The ICS1722 enters the polling detect mode and applies a
100ms charge pulse. During the pulse, the ICS1722 monitors the
VIN pin to determine if the divided down terminal voltage is above
OPREF. If the battery is present, the voltage will be clamped below
the reference on OPREF while the current pulse is applied. If a
battery is not present, the voltage at VIN will rise above the
reference at OPREF.
The discharge-to-charge mode can be entered by placing the
AUX0 pin high (H) and the AUX1 pin low (L) with the SEL0 and
SEL1 inputs set for the desired fast charge rate. This setting initializes
the discharge sequence. The ICS1722 enters the discharge-to-charge
mode at initial power-up or with a master reset. The discharge mode
occurs first, to be followed by the selected fast charge mode. During
discharge, the MMN indicator flashes at a one second rate, while
during the soft start and fast charge stages the CMN indicator is
activated continuously.
The charge pulse will repeat until the battery is reinstalled. The
polling detect indicator (PFN) is the only indicator active as long as
the ICS1722 is in the polling detect mode. Once a battery is
installed, the ICS1722 will turn off the PFN indicator and enter the
soft start stage. The ICS1722 will automatically re-enter the
polling detect mode if the battery is removed.
Four charge modes are available after the discharge portion is complete
by changing the state of the AUX inputs during the discharge portion
of this mode. The available charge modes are:
Fast Charge: Leave the AUX inputs open (Z).
Battery Removal
During the application of a charge pulse, the voltage at the VIN pin
is compared to the voltage at the OPREF pin. If the voltage at VIN
is greater than the voltage at OPREF during the application of the
current pulse, then the battery is assumed to have been removed
and the ICS1722 enters the polling detect mode. If the voltage at
VIN is below the voltage at OPREF, charging continues.
•
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 must be greater than
0.5V if a battery is attached. If the voltage at VIN is less than 0.5V,
the ICS1722 assumes the battery has been removed, and the
polling detect mode is initiated.
If the battery is removed while in the discharge-to-charge mode, the
ICS1722 will continually reset itself until the battery is reinstalled. See
Application Information for more information.
•
•
•
Direct Maintenance Mode: Set the AUX0 low (L) and AUX1 high
(H).
Condition Mode: Set AUX0 high (H) and AUX1 open (Z).
Ten-Hour Timer Mode: Set AUX0 high (H) and
AUX1 high (H).
Discharge-Only Mode
The time required for discharge depends on the energy in the battery
and the discharge rate. The discharge is not limited by a timer. This
allows the user to set the discharge rate. The battery is drained to 1
volt/cell as read at the VIN pin under load. The ICS1722 shuts down
after the discharge sequence is finished and a master reset must be
performed to reactivate the device. The discharge load is activated by
the DCHG pin which goes low for about 400ms every second. A
resistor value selected for a 2.5C discharge based on 1.4V/cell results
in about a 1C discharge rate. The discharge-only mode can be entered
by placing the AUX0 pin open (Z) and the AUX1 pin low (L). The
ICS1722 enters this mode at initial power-up or with a master reset.
During the discharge portion, the MMN indicator flashes at a one
second rate.
Auxiliary Modes of Operation
The ICS1722 allows six alternate modes of operation to help
customize the charging system for certain applications. The trilevel AUX0 and AUX1 pins are used to select the operating mode.
The AUX0 and AUX1 pins default the ICS1722 into fast charge
operation. Except for the discharge-to-charge mode, another mode
can only be selected by re-programming and resetting the
controller.
7
ICS1722
Direct Maintenance Mode
Ten Hour Timer Mode
The ICS1722 can enter directly into the C/40 maintenance mode
for cells that require a maintenance charge only. The direct
maintenance mode is activated by setting the AUX0 pin low (L)
and the AUX1 pin high (H), and resetting the device. The SEL0
and SEL1 pins must be set based on the charging current and the
battery capacity. The formula
Placing the AUX0 and AUX1 pins both high (H) enables a ten
hour timer. This timer limits the total charge, including the
maintenance charge, to approximately ten hours for a battery that is
completely discharged before fast charge is initiated. The ten hour
limit is based on the assumption that the charge terminates due to
the fast charge timer as shown in Table 1.
Charging System Test
Charging Current (Amps)
Battery Capacity (Amp • hr)
The system test mode is intended for use in applications where the
charging system functionality needs to be tested. The system test
sequence consists of a one second activation of the CMN, MMN
and PFN indicator pins as well as the CHG and DCHG lines. The
system test mode is entered by placing both the AUX0 and AUX1
pins low (L). The ICS1722 shuts down after the test sequence is
finished and a master reset must be performed to reactivate the
device.
gives the charge rate. Use Table 4 to find the correct SEL0 and
SEL1 settings. The maintenance charge is applied until the battery
is removed, upon which the ICS1722 will enter the polling detect
mode. The ICS1722 will enter the direct maintenance mode upon
initial power-up or after a master reset. The MMN indicator will be
active during this mode.
Conditioning Mode
The ICS1722 can enter a conditioning mode which applies a C/10
charge for a timed 10 hour period, followed by an indefinite C/40
maintenance charge until the batteries are removed.
The conditioning mode can be entered by setting the AUX0 pin
high (H) and the AUX1 pin open (Z). The SEL0 and SEL1 pins
must be set based on the charging current and the battery capacity.
The formula
Charging Current (Amps)
Battery Capacity (Amp • hr)
gives the charge rate. Use Table 3 to find the correct SEL0 and
SEL1 settings. The MMN indicator will be active during the 10
hour conditioning charge and the maintenance charge that follows.
The ICS1722 enters the polling detect mode if the battery is
removed.
Table 1: Ten Hour Timer Information
Charge Rate
4C
2C
1.3 C
1C
C/1.5
C/2
C/2.5
C/3
C/4
Maintenance Timer Cutoff
(after fast charge termination)
9.7 hrs
9.4 hrs
9.1 hrs
8.8 hrs
8.2 hrs
7.6 hrs
6.5 hrs
6.0 hrs
5.4 hrs
Fast Charge Timer Cutoff
0.3
0.6
0.9
1.2
1.8
2.4
3.5
4.0
4.6
hrs
hrs
hrs
hrs
hrs
hrs
hrs
hrs
hrs
8
Charge Time Limit
(from reset)
10 hrs
10 hrs
10 hrs
10 hrs
10 hrs
10 hrs
10 hrs
10 hrs
10 hrs
ICS1722
Pin Descriptions
The maintenance mode (MMN) indicator is on when the
ICS1722 is either in the topping charge, maintenance charge, direct
maintenance mode, or the condition mode. The maintenance mode
indicator flashes at a one second rate when the ICS1702 is
controlling the discharge portion of the discharge-to-charge or the
discharge-only mode.
The polling detect (PFN) indicator is on when the ICS1722 polls
for a battery. The controller applies periodic charge pulses to detect
the presence of a battery. The indicator is a warning that these
charge pulses are appearing at the charging system terminals at
regular intervals. When a battery is detected, the indicator is turned
off.
The ICS1722 requires some external components to control the
clock rate and provide an indicator display. The controller must be
interfaced to an external power source that will provide the current
required to charge a battery pack and, if desired, a circuit that will
sink discharge current.
Output Logic Signals: CHG, DCHG Pins
The CHG and DCHG pins are active high, TTL compatible
outputs. In addition to being TTL compatible, the CMOS outputs
are capable of sourcing current which adds flexibility when
interfacing to other circuitry. A logic high on the CHG pin
indicates that the charging current supply should be activated. If
applicable, a logic high on the DCHG pin indicates that the
discharge circuit should be activated.
Charge Rate Selection: SEL0, SEL1 Pins
The SEL0 and SEL1 inputs must be programmed by the user to
inform the ICS1722 of the desired charge rate. When left
unconnected (open), these tri-level pins will float to about 2.3V.
When a low level is required, the pin must be grounded. When a
high level is required, the pin must be tied to VDD . The voltage
ranges for low (L), open (Z) and high (H) are listed in Table 6, DC
Characteristics. To program the SEL0 and SEL1 inputs, refer to
the Charge Rate List in Table 3.
Care must be taken to control wiring resistance and inductance.
The load resistor must be capable of handling this short duration
high-amplitude pulse. If the auxiliary discharge-to-charge mode is
selected, the power dissipation of the load resistor must be properly
selected to accept the extended length of the discharge pulse.
Indicators: CMN, MMN, PFN Pins
The ICS1722 does not control the current flowing into the battery
in any way other than turning it on and off. The required current
for the selected charge rate must be provided by the user’s power
source. The external charging circuitry should provide current at
the selected charge rate. For example, to charge a 1.2 ampere hour
battery in 30 minutes (2C), approximately 2.4 amperes of current is
required.
The controller has three outputs for driving external indicators.
These pins are active low. The three indicator outputs have open
drains and are designed to be used with LEDs. Each output can
sink over 20mA which requires the use of an external current
limiting resistor. The three indicator signals denote fast charge
stage, topping and maintenance stages, and the polling detect mode
as shown in Table 2.
The charge mode (CMN) indicator is activated continuously during
the soft start and fast charge stages. When the controller enters the
topping charge stage, the output goes high and the indicator turns
off.
Table 2: Indicator Description List
PFN
On
MMN
CMN
On
On
Flash
Flash
On
Flash
Flash
Description
Polling mode or battery fault
Maintenance or topping charge, direct maintenance or condition mode
Fast charge
Discharge portion of the discharge-to-charge or discharge-only mode
See Applications Information
See Applications Information
Fast Charge (See Applications Information)
9
ICS1722
Table 3: Charge Rate List
SEL0
SEL1
Charge Rate
Topping Charge
pulse Rate
Maintenance Charge Pulse
Rate
L
L
L
H
H
H
Z
Z
Z
L
H
Z
L
Z
H
L
Z
H
4C (15 min)
2C (30 min)
1.3C (45 min)
1C (60 min)
C/1.5 (90 min)
C/2 (120 min)
C/2.5 (150 min)
C/3 (180 min)
C/4 (240 min)
one every 40 sec
one every 20 sec
one every 13 sec
one every 10 sec
one every 7 sec
one every 5 sec
one every 4 sec
one every 3 sec
one every 2 sec
one every 160 sec
one every 80 sec
one every 53 sec
one every 40 sec
one every 27 sec
one every 20 sec
one every 16 sec
one every 13 sec
one every 10 sec
Fast Charge Timer
Duration (after reset)
21 min
39 min
57 min
75 min
110 min
144 min
212 min
244 min
275 min
See the section on Controller Operation for additional information on the topping charge and maintenance charge. See the section on Charge Termination
Methods for additional information on the charge timer.
Mode Selection: AUX0, AUX1 Pins
When a high level is required, the pin must be tied to VDD . The
voltage ranges for low (L), open (Z) and high (H) are listed in
Table 6, DC Characteristics. To program the AUX0 and AUX1
inputs, refer to the Mode Select List in Table 4. See the section on
Auxiliary Modes of Operation for additional information.
The AUX0 and AUX1 inputs must be programmed by the user to
inform the ICS1722 of the desired auxiliary mode. When left
unconnected (open) these tri-level pins will float to about 2.3V.
When a low level is required, the pin must be grounded.
Table 4: Mode Select List
AUX0
L
L
Z
Z
H
H
H
AUX1
L
H
Z
L
L
Z
H
Mode Selected
Charging System Test
Direct Maintenance
Fast Charge
Discharge-Only
Discharge-to-Charge
Condition
Ten Hour Timer
Mode Operation
Charging system test for embedded applications
Indefinite C/40 maintenance charge
Default
Battery discharge to 1V/cell
Battery discharge to 1V/cell followed by the selected charge mode
Timed C/10 topping charge followed by a C/40 maintenance charge
Limits total charge including the maintenance charge to 10 hours
10
ICS1722
Master Reset: MRN Pin
VIN pin
The MRN pin is provided to re-program the controller for a new
mode or charging sequence. This pin has an internal pull-up of
about 75kΩ . A logic low on the MRN pin must be present for more
than 700ms for a reset to occur. As long as the pin is low, the
controller is held in a reset condition. A master reset is required to
clear the charging system test, reset the ten hour timer, change
charge rates or auxiliary modes. Upon power-up, the controller
automatically resets itself.
R1
# of cells
R2
Clock Input: RC Pin
The RC pin is used to set the frequency of the internal clock when
an external 1 MHz clock is not available. An external resistor must
be connected between this pin and VDD . An external capacitor
must be connected between this pin and ground. The frequency of
the internal clock will be about 1 MHz with a 16kΩ resistor and a
100pF capacitor. All time durations noted in this document are
based on a 1 MHz clock. Operating the clock at a lower frequency
will proportionally change all time
durations. Operating the clock at a frequency significantly lower
than 1 MHz, without adjusting the charge current accordingly, will
lessen the effectiveness of the fast charge timer and lower the
accuracy of the controller. Operating the clock at a frequency
greater than 1 MHz will also change all time durations and, without
adjusting the charge current accordingly, may cause termination to
occur due to the fast charge timer expiring rather than by the
battery reaching full charge.
Figure 7: Resistor divider network
at the VIN pin
Open Circuit Voltage Reference: OPREF Pin
The OPREF pin has an internal 75kΩ pull-up resistor to VDD .
OPREF requires an external pull-down resistor to establish the
open circuit (no battery) voltage reference. The purpose of this
voltage reference is to detect the removal of the battery from the
charging system. The voltage at this pin is compared to the voltage
at the VIN pin when the current source is turned on. If the voltage
at VIN is greater than the voltage at OPREF, the ICS1722 assumes
the battery has been removed and the ICS1722 enters the polling
detect mode.
The clock may be driven by a 1 MHz external 0 to 5V pulse
provided the duty cycle is between 10% and 60%. The clock input
impedance is about 1kΩ .
For proper operation, the voltage at OPREF must be set below the
(divided down) open circuit voltage produced by the current source
and above the maximum normalized battery voltage. The OPREF
pin voltage must not exceed 2.3V or it will prevent the start of fast
charge. If the voltage on OPREF exceeds 4V, the controller will
shutdown and must be reset.
Voltage Input: VIN Pin
The battery voltage must be normalized by an external resistor
divider network to one cell. The electrochemical potential of one
cell is about 1.2V. For example, if the battery consists of six cells
in series, the voltage at the VIN pin must be equal to the total
battery voltage divided by six. This can be accomplished with two
resistors, as shown in Figure 7. To determine the correct resistor
values, count the number of cells to be charged in series. Then
choose either R1 or R2 and solve for the other resistor using:
R1 = R2 * (# of cells -1) or R2 =
As an example, suppose that a current source has an open circuit
voltage of 12V as shown in Figure 8. The maximum expected
battery voltage of a six-cell pack is determined to be 9.6V. The
voltage at OPREF should be set at a point between 1.6V (9.6V/6
cells=1.6V) and 2V (12V/6=2V). This is accomplished with a pulldown resistor. Refer to the VIN and OPREF resistor tables in the
Applications Information section. From the VIN table, the divider
resistors are 10kΩ and 2kΩ for R1 and R2. From the OPREF
table, the pull-down resistor is 43kΩ for R3. If R3 is 43kΩ , the
voltage at OPREF is 1.82V since the internal pull-up at the OPREF
pin is 75kΩ .
R1
(# of cells -1)
11
ICS1722
current source
(open circuit voltage = 12V)
+5V
+
R1 = 10k
R3 = 2.2k
OPREF = 1.86V
6 cells
(9.6 V)
VIN =
1.60V (battery present)
(no battery)
{ 2.00V
R2 = 2k
R4 = 1.3k
-
Resistor divider at the OPREF pin
Resistor divider at the VIN pin
Figure 8: Open Circuit Reference Example
Power: VDD Pin
Grounding: VSS Pin
The power supply for the device must be connected to the VDD
pin. The voltage should be +5 VDC and should be supplied to the
part through a regulator that has good noise rejection and an
adequate current rating. The controller requires up to a maximum
of 11mA with VDD =5.00V.
This pin must have a direct connection to a solid ground plane.
Data Tables
Table 5: Absolute Maximum Ratings
Supply Voltage
Logic Input Levels
Ambient Operating Temperature
Storage Temperature
6.5
-0.5 to VDD + 0.5
0 to 70
-55 to 150
V
V
°C
°C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only.
Functional operation of the device at the Absolute Maximum Ratings or other conditions not consistent with the characteristics shown in this
document is not recommended. Exposure to absolute maximum rating conditions for extended periods may affect product reliability.
12
ICS1722
Table 6: DC Characteristics
T amb=25°C. All values given are typical at specified VDD.
Parameter
Supply Voltage
Supply Current
High Level Input Voltage
SEL0, SEL1, AUX0, AUX1
Low Level Input Voltage
SEL0, SEL1, AUX0, AUX1
Open Input Voltage
SEL0, SEL1, AUX0, AUX1
Low Level Input Current, pull-up MRN,
OPREF
High Level Source Current
CHG, DCHG
Low Level Sink Current
CHG, DCHG
Low Level Sink Current, indicator
PFN, CMN, MMN
Symbol
Test Conditions
VDD
IDD
VIH
VIL
MIN
4.5
MAX
5.5
3.6
TYP
5.0
7.3
4.1
4.5
UNITS
V
mA
V
0.73
0.75
0.8
V
open
2.3
V
IIL
V=0.4V
74
µA
IOH
V= VDD - 0.4V
28
mA
IOL
V=0.4V
25
mA
IOL
V=0.4V
40
mA
Input Impedance
Analog/Digital Converter Range
Minimum Battery Threshold
0-2.2
13
1.0
0-2.7
0.5
0-2.7
MΩ
V
V
ICS1722
Table 8: Timing Characteristics
R≈16kΩ , C≈100pF
PARAMETER
Clock Frequency
Reset Pulse Duration
Charge Pulse Width
Discharge Pulse Width
Rest Time
Data Acquisition Time
Cycle Time
Capacitor Discharge Pulse Width
Capacitor Discharge Pulse Period
Polling Detect Pulse Width
Polling Detect Pulse Period
Soft Start Initial Pulse Width
Soft Start Incremental Pulse Width
Discharge Mode Pulse Width
Discharge Mode Pulse Period
RESET to SEL Dynamic Reprogram Period
SYMBOL
REFERENCE
t RESET
t CHG
t DCHG
tR
t DA
t CYCLE
see Figure B
see Figure A
see Figure A
see Figure A
see Figure A
see Figure A
t RSA
see Figure B
TYP
1.0
700
1048
5.0
4.0
16.4
1077
5.0
100
100
624
200
7.0
400
1050
1160
Timing Diagrams
Figure A:
tCHG
tR
CHG
DCHG
voltage
t DCHG
tCYCLE
Figure B:
t RE S E T
R ES E T
SEL0
SEL1
AU X 0
AU X 1
t RS A
14
tR
tDA
UNITS
MHz
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ICS1722
Applications Information
With the batteries removed, the current source must be capable of
raising the voltage at the VIN pin above the voltage at the OPREF
pin to ensure proper polling. With the batteries in-stalled, the
current source overshoot characteristics when turned on and off
must not cause the voltage at the VIN pin to exceed the voltage at
the OPREF pin. If the voltage at OPREF exceeds the voltage at
VIN when a charge pulse is applied or removed, the polling feature
will be activated.
To ensure proper operation of the ICS1722, external components
must be properly selected. The external current source used must
meet several important criteria to ensure optimal performance of
the charging system. The charging current should be constant when
using voltage slope termination.
VIN and OPREF Divider Resistors
Figure 9 shows a typical application using the ICS1722. R1
through R3 must be carefully selected to ensure that battery
detection and voltage termination methods operate properly.
R1 and R2 are selected to scale the battery voltage down to the
voltage of one cell. The following table shows some typical values.
Additional information is available in the Voltage Input section.
Cells
1
2
3
4
5
6
7
8
R1
Short
2.0k
2.0k
3.0k
12k
10k
12k
9.1k
PC Board Design Considerations
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. 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 ICS1722 and the
constant current source control circuits outside the power and
return loop described above. These precautions will prevent high
circulating currents and coupled noise from disturbing normal
operation.
R2
Open
2.0k
1.0k
1.0k
3.0k
2.0k
2.0k
1.3k
The current source should prevent ripple voltage from appearing on
the battery. The effects of ripple on the battery voltage may
interfere with proper operation.
Using the Voltage Slope Termination Method
In general, the voltage slope termination method works best
for equipment where the battery is fast charged with the equipment
off or the battery is removed from the equipment for fast charge.
R3 is used to set the open circuit (no battery) reference voltage on
the OPREF pin. The function of this pin is discussed in the Open
Circuit Reference section.
VOPREF
1.82 V
1.93 V
2.02 V
2.14 V
R3
43k
47k
51k
56k
15
ICS1722
Charging System Status by Indicator
The voltage slope termination method used by the ICS1722
requires a nearly constant current flow into the battery during fast
charge. Charging the battery in equipment that draws a known
constant current while the battery is charging should have this
current draw added to the fast charge current. Using the ICS1722
for charging the batteries in equipment that randomly or
periodically requires moderate current from the battery during fast
charge needs evaluation. Equipment that randomly or periodically
requires high current from the battery during fast charge may cause
a voltage inflection that results in termination before full charge. A
voltage inflection can occur due to the charge current decreasing or
fluctuating as the load changes rather than by the battery reaching
full charge. The voltage slope method will terminate charge based
on voltage inflections that are characteristic of a fully charged
battery. The
ICS1702 and ICS1712 charge controllers have temperature
termination methods for equipment that randomly or periodically
draws significant current from the battery during fast charge.
The Indicator Description List in Table 2 contains displays that are
caused by charging system abnormalities. When the CMN
indicator is flashing with no other indicator active, there is voltage
present at the battery terminals with the current source off and no
battery. Check the current source and ensure that it produces no
more than the equivalent of 350mV/cell when turned off with no
battery. If the VIN divider resistors were not properly selected, an
open circuit voltage that is actually less than the equivalent of
350mV/cell with the charger off and no battery will not divide
down this open circuit voltage properly and produce the CMN
flash indication. Check the VIN divider and ensure that it properly
normalizes the battery voltage to the electrochemical potential of
about 1.2V cell. If the CMN flash indication occurs with the
battery installed, then the constant current source is producing
more than the equivalent of 350mV/cell when off and there is an
open connection between the charger terminals and the battery.
Check wires, connections, battery terminals, and the battery itself
for an open circuit condition.
Charging sources that produce decreasing current as fast charge
progresses may also cause a voltage inflection that may result in
termination before full charge. For example, if the charge current is
supplied through a resistor or if the charging source is a constant
current type that has insufficient input voltage, the current will
decrease and may cause a termination before full charge. Other
current source abnormalities that may cause a voltage inflection
that is characteristic of a fully charged battery are inadequate ripple
and noise attenuation capability or charge current decreasing due to
thermal drift. Charging sources that have any of the above
characteristics need evaluation to access their suitability for the
application if the use of the voltage slope termination is desired.
If the MMN and CMN indicators are alternately flashing, the likely
cause is no battery with the ICS1722 programmed in the
discharge-to-charge auxiliary mode. If the battery is present, check
wires, connectors, battery terminals, and the battery itself for an
open circuit condition.
If the MMN indicator is active at the initiation of fast charge, check
the external pull-down resistor from OPREF to ground. A voltage
at OPREF that exceeds 2.3V will prevent the start of fast charge.
The controller soft start stage, built-in noise filtering, and fast
charge timer operate optimally when the constant current source
charges the battery at the rate selected. If the actual charge current
is significantly less than the rate selected, the conditioning effect of
the soft start stage and the controller noise immunity are lessened.
Also, the fast charge timer may cause termination based on time
duration rather than by the battery reaching full charge due to
inadequate charge current.
16
ICS1722
V
CONSTANT
CURRENT
SOURCE
in
R4 (note 1)
+5V +5V
Q1 (note 2)
+ 5 V (note 5)
ICS1722
390
390
1k
(note 3)
+5V
1
2
FAULT 3
MAINT 4
CHG 5
6
7
8
CHG
VDD
unused
DCHG
PFN
VIN
MMN
OPREF
CMN
AUX1
AUX0
SEL0
VSS
RC
SEL1
MRN
16
15
14
13
12
11
10
9
4.7µF
.047µF
R1
.047µF
+5V
R3
open
@ 45°C
R2
16k
(note 6)
100pF
Notes:
1) Value of R4 determined by discharge current and capacity of battery pack.
2) Discharge FET is logic-level compatible in this application.
3) DC return of discharge FET must be connected close to negative battery terminal.
4) Regulated supply
5) Power ground; others are signal ground. Connect signal ground to power ground
at negative battery terminal only.
Figure 9: Functional Diagram
17
ICS1722
Package Information
0.018
0.060
0.016
QuickSaver
0.250
QuickSaver
GPI
ICS1722N
0.296
GPI
ICS1722M
0.310
0.750
0.404
0.041
0.250
0.405
0.130
0.094
0.130
0.041
0.010
0.015
0.296
0.008
0.008
0.016
0.350
0.050
0.018
0.033
All package dimensions are in inches.
0.100
0.060
All package dimensions are in inches.
16-Pin SOIC Package (300 mil)
16-Pin DIP package (300 mil)
0.016
0.039
QuickSaver
GPI
ICS1722S
R
0.155
0.236
0.390
0.031
0.058
0.024
0.154
0.008
0.006
0.016
0.050
All package dimensions are in inches.
16-Pin SOIC Package (150 mil)
Ordering Information:
ICS1722M, ICS1722MT,
ICS1722S, ICS1722ST, ICS1722N
Example:
ICS 1712 ST
Package type:
N=
DIP (Plastic)
M= 300 mil SOIC
S=
150 mil SOIC
MT= 300 mil SOIC Tape and Reel
ST= 150 mil SOIC Tape and Reel
Device type: Consists of 3 to 5 digits or numbers
Prefix: ICS = Intelligent Charging Solution standard device
18
0.008
0.025
ICS1722
IMPORTANT NOTICE
Galaxy Power Incorporated makes no claim about the capability of any particular battery (NiCd or NiMH) to accept a fast charge. GPI
strongly recommends that the battery manufacturer be consulted before fast charging. GPI shall be held harmless for any misapplication of
this device such as: exceeding the rated specifications of the battery manufacturer; charging batteries other than nickel-cadmium or nickelmetal hydride type; personal or product damage caused by the charging device, circuit, or system itself; unsafe use, application, and/or
manufacture of a charging system using this device.
GPI reserves the right to make changes in the device data identified in this publication without further notice. GPI advises its customers to
obtain the latest version of all device data to verify that any information being relied upon by the customer is current and accurate.
GPI does not assume any liability arising out of or associated with the application or use of any product or integrated circuit or component
described herein. GPI does not convey any license under its patent rights or the patent rights of others described herein. In the absence of a
written or prior stated agreement to the contrary, the terms and conditions stated on the back of the GPI order acknowledgment obtain.
GPI makes no warranty of any kind with regard to this material, including, but not limited to, the implied warranties of merchantability and
fitness for a particular purpose.
GPI products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any nuclear facility application, or for any other application in which the failure of the
GPI product(s) could create a situation where personal injury or death may occur. GPI will not knowingly sell its products for use in such
applications, and the buyer shall indemnify and hold harmless GPI and its officers, employees, subsidiaries, affiliates, representatives and
distributors against all claims, costs, damages, expenses, tort and attorney fees arising out of directly or indirectly, any claim of personal
injury or death associated with such unintended or unauthorized use, even if such claim alleges that GPI was negligent regarding the design
or manufacture of the part.
COPYRIGHT © 1998 Galaxy Power Incorporated
19
ICS1722
NOTES
20
NOTES
21
ICS1722
ICS1722
NOTES
22
NOTES
23
ICS1722
ICS1722
GPI Sales Offices
Headquarters
Galaxy Power, Inc.
PO Box 890
2500 Eisenhower Avenue
Valley Forge, PA 19482-0890
Phone:
1-610-676-0188
FAX:
1-610-676-0189
Internet:
www.galaxypower.com
January 20, 1999
GPI Sales Representative
24