Galaxy ICS1712MT Charge controller for nickel-cadmium and nickel-metal hydride battery Datasheet

ICS1712
QuickSaver® Charge Controller for Nickel-Cadmium
and Nickel-Metal Hydride Batteries
General Description
Features
•
The ICS1712 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 and/or temperature slope
termination. The ICS1712 employs a four stage charge sequence
that provides a complete recharge without overcharging. The
controller has four user-selectable charge rates available for
customized charging systems.
•
The ICS1712 monitors for the presence of a battery and begins
charging if a battery is installed within the first 10 seconds after a
reset. Voltage and temperature are measured to ensure a battery is
within fast charge conditions before charge is initiated.
•
•
Applications
•
Battery charging systems for:
Portable consumer electronics
Power tools
- Audio/video equipment
- Communications equipment
- Wireless handsets
•
•
Multiple charge termination methods include:
Voltage slope
Temperature slope
Maximum temperature
Charge timer
Four stage charge sequence:
Soft start charge
Fast charge
Topping charge
Maintenance charge
Reverse-pulse charging available in all charge stages
Four programmable charge rates between 15 minutes (4C) and
two hours (C/2)
Out-of-temperature range detection
Hot battery: charger shutdown
Cold battery: low current charge
Ten second polling mode for battery detection
Battery fault with shutdown protection
Block Diagram
CHARGE
SELECT
POLLING/
FAULT LED
2.0V
MICROCODE CONTROL
0.5V
VOLTAGE
SENSE
ADC
PROCESSOR
TERMINATION
SELECT
COLD
TEMPERATURE
SENSE
HOT
OUTPUT
CONTROL
TEMPERATURE
STATUS LED
CHARGE
CONTROL
RAM
ROM
RESET
RC
CHARGE
MODE LED
DISCHARGE
CONTROL
OSCILLATOR
QuickSaver  is a registered trademark of Galaxy Power, Inc.
ICS1712
Pin Configuration
CHG
1
16
VDD
DCHG
2
15
unused
PFN
3
14
VIN
CMN
4
13
THERM
OTN
5
12
DTSEL
SEL0
6
11
RC
VSS
7
10
MRN
AVSS
8
9
SEL1
ICS1712
16-Pin DIP or SOIC
Pin Definitions
Pin
Number
1
Pin Name
Type
CHG
OUT
2
3
DCHG
PFN
OUT
OUT
4
CMN
OUT
5
OTN
OUT
6
7
8
9
10
11
12
13
14
15
16
SEL0
VSS
AVSS
SEL1
MRN
RC
DTSEL
THERM
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 fault indicator. An active low turns on an external indicator to show the controller is either
polling for the presence of the battery or has determined the battery has been removed.
Charge mode indicator. A continuous low shows the controller is in a soft start or fast charge. The
indicator flashes during the topping and maintenance charges.
Out-of-temperature range indicator. An active low turns on an external indicator showing the battery is
out of the normal fast charge temperature range.
Input used with the SEL1 pin to program the device for the desired charge rate.
Ground.
Ground.
IN
IN
IN
IN
IN
IN
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.
Selects temperature slope and/or voltage slope termination
Thermistor or thermal switch input for temperature sensing.
Battery voltage normalized to one cell with an external resistor divider.
Ground.
Device supply =+5.0 VDC
Pins 6, 9, 10 and 13 have an internal pull-up.
Pin 12 has an internal pull-down.
2
ICS1712
Controller Operation
Soft Start Charge
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)
Soft-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
ICS1712
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
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 ICS1712 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.
Fast Charge
In the second stage, the ICS1712 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
ICS1712
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.
Topping Charge
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 CMN indicator flashes at a one
second rate 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 ICS1712 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 ICS1712 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. The
CMN indicator flashes at a one second rate during this stage.
delay time
cycle
time
Figure 5: Representative timing diagram for topping and maintenance charge
5
ICS1712
Charge Termination Methods
Cells that are not thoroughly conditioned or possess an unusual cell
construction may not have a normal voltage profile. The ICS1712
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.
Several charge termination schemes, including voltage slope,
temperature slope, maximum temperature and two overall charge
timers are available. The voltage slope and negative voltage slope
methods may be used with or without the temperature slope and the
maximum temperature method. Maximum temperature and the fast
charge timer are available as backup methods.
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
ICS1712 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.
Figure 6: Voltage and slope curves showing inflection and zero slope points
6
ICS1712
Temperature Slope Termination
Temperature slope termination is based on the battery producing an
accelerated rate of heating as the amount of readily chargeable
material diminishes at full charge. An increase in battery (cell)
heating due to the charging reaction will occur at a much faster rate
than a change due to a warming ambient temperature. Note the
effect of 0.5°C fluctuations in ambient temperatures resulting in
slight variations in the temperature slope as shown in Figure 7.
However, the increase in cell temperature near the end of charge
causes a much larger change in the temperature slope that can be
easily detected and used as a trigger for fast charge termination.
Figure 8: Cell temperature and
thermistor voltage slope
Table 1 shows the decrease in thermistor voltage the last minute
before full charge required by the ICS1712 at various charge rates.
The thermistor voltage slope should exceed the listed value to
ensure charge termination. Note that changes in thermistor
location, cell size or large ambient temperature fluctuations can
affect the slope to some degree. Refer to the Applications
Information section and Temperature Slope and Maximum
Temperature section for more information on thermistor mounting.
Figure 7: Cell temperature and
temperature slope
Table 1: Slope vs. Charge Rate
Charge Rate
The rate of change in cell temperature can be determined by
measuring the change in voltage across a negative temperature
coefficient thermistor as shown in Figure 8. The resistance of an
NTC thermistor changes in proportion in the change in temperature
of the thermistor. The ICS1712 measures the decreasing resistance
as a drop in voltage and calculates the thermistor voltage slope,
shown in Figure 8. The controller terminates fast charge based on
the selected charge rate and the calculated slope.
>C/2
C/2
7
Thermistor Voltage Slope
(-V/min.)
0.040
0.028
ICS1712
To determine the required thermistor characteristics for proper
temperature slope termination, the battery temperature rise must be
known or determined for the last minute prior to full charge.
If a thermal switch is used, a 45°C open circuit switch is
recommended. When the thermal switch opens, an internal pull-up
at the THERM pin results in a logic high which shuts down the
controller and activates the OTN indicator. The controller must be
reset once the hot battery fault condition has cleared to restart the
charge sequence.
Maximum temperature termination is also enabled when
temperature slope termination is used. Care must be taken to keep
voltage levels at the THERM pin within the fast charge range
(between 2.4V and 0.93V), as shown in Figure 9.
Maximum temperature termination can be disabled by grounding
the THERM pin. See the section on Temperature Sensing for more
information.
Maximum Temperature Termination
Maximum temperature can be sensed using either a NTC
thermistor or a thermal switch. Maximum temperature termination
can also be bypassed if desired, although it is strongly
recommended that some form of temperature termination be used.
Fast 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 best suited as 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.
If an NTC thermistor is used, an internal voltage threshold
determines when the battery is too hot to charge. As temperature
increases, the voltage across the thermistor will drop. This voltage
is continually compared to the internal voltage threshold. If the
thermistor voltage drops below the internal threshold, the OTN
indicator is activated and the controller shuts down. The controller
must be reset once the hot battery fault condition has cleared to
restart the charge sequence.
8
ICS1712
Battery Polling
Battery Fault Detection
Upon power-up or after a reset is issued, any excess charge from
filter capacitors at the charging system 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
ICS1712 assumes no battery is attached and initiates a polling
sequence.
The ICS1712 will turn on the PFN fault indicator 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 ICS1712 assumes the battery has been removed, a fault
condition is indicated by the PFN fault indicator, and the controller
shuts down.
The ICS1712 then applies a 100ms charge pulse. During the pulse,
the ICS1712 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 PFN fault indicator is
activated.
Cold Battery Charging
Cold battery charging is activated if a voltage at the THERM pin is
in the cold battery voltage range, as shown in Figure 7.
The ICS1712 checks for a cold battery before initiating fast charge.
If a cold battery is present before fast charging begins, the
ICS1712 begins a two hour C/10 topping charge (the pulsed duty
cycle is based on the selected charge rate). If the battery is still cold
after the two hour topping charge is complete, the ICS1712 begins
a C/40 maintenance charge. The maintenance charge will continue
for as long as the battery remains cold. The thermistor voltage at
the THERM pin is checked every second to see if the battery has
warmed up. If so, the ICS1712 stops the topping charge or
maintenance charge and begins a fast charge at a rate selected by
the SEL0 and SEL1 inputs. See the section on Temperature
Sensing for more information.
The charge pulses repeat for 10 seconds. If the battery is installed
within 10 seconds, the ICS1712 will turn off the PFN fault
indicator and enter the soft start stage. If the battery is not installed
within 10 seconds, the PFN fault indicator remains active and the
ICS1712 shuts down. A reset must be issued to restart the
controller after installing the battery.
The CMN will flash at a one second rate, and the OTN indicator
will be active, indicating that a low current charge is being applied
to a battery that is outside the specified temperature range for fast
charging.
9
ICS1712
Pin Descriptions
Indicators: CMN, PFN, OTN Pins
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 or
battery fault and out-of-temperature range modes as shown in
Table 2.
The ICS1712 requires some external components to control the
clock rate, sense temperature 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.
The charge mode (CMN) indicator is activated continuously during
the soft start and fast charge stages. The CMN indicator flashes at a
one-second rate when the ICS1712 is applying a topping or
maintenance charge.
The polling fault (PFN) indicator is on when the ICS1712 polls for
a battery for the first 10 seconds. 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 indicator is also active if the battery
is removed from the system, warning that a fault has occurred.
Care must be taken to control wiring resistance and inductance.
The load resistor must be capable of handling this short duration
high-amplitude pulse.
The out-of-temperature range (OTN) indicator is active whenever
the voltage at the temperature sense (THERM) input enters a range
that indicates that the attached battery is too hot to charge. The
OTN indicator is also activated with the CMN indicator if the
controller is initialized with the battery in the cold battery charge
region.
Table 2: Indicator Description List
PFN
On
CMN
OTN
Flash
On
On
Flash
On
One flash
On
On
on
Description
Polling mode or battery fault
Maintenance and topping charge
Fast charge
Hot battery shutdown
Cold battery charge
See Applications Information
See Applications Information
10
ICS1712
The ICS1712 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.
Charge Rate Selection: SEL0, SEL1 Pins
The SEL0 and SEL1 inputs must be programmed by the user to
inform the ICS1702 of the desired charge rate. When a low level is
required, the pin must be grounded. When a high level is required,
no connection is required since each pin has an internal 75kΩ pullup to VDD. The voltage ranges for low (L) and high (H) are listed in
Table 8, DC Characteristics. To program the SEL0 and SEL1
inputs, refer to the Charge Rate List in Table 3.
Table 3: Charge Rate List
SEL0
SEL1
Charge Rate
Topping Charge
pulse Rate
Maintenance Charge Pulse
Rate
L
L
H
H
L
H
L
H
4C (15 min)
2C (30 min)
1C (60 min)
C/2 (120 min)
one every 40 sec
one every 20 sec
one every 10 sec
one every 5 sec
one every 160 sec
one every 80 sec
one every 40 sec
one every 20 sec
Fast Charge Timer
Duration (after reset)
30 min
60 min
90 min
210 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.
11
ICS1712
•
Master Reset: MRN 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 a temperature fault condition, clear the charging system test,
reset the ten hour timer or change charge rates or auxiliary modes.
Upon power-up, the controller automatically resets itself.
Using an NTC thermistor for hot and cold battery
detection:
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 9:Voltage levels for temperature
sensing with a thermistor or thermal switch
The THERM pin requires some thought if a thermistor is going to
be used for hot and cold battery detection. The example below
works for a typical 10kΩ @ 25°C NTC thermistor. Consider using
the controller to prevent charging above 45°C and reducing the
current below 10°C. At 10°C the resistance of the thermistor is
18kΩ. At 45°C, the resistance drops to 4.7kΩ. The ICS1712 has
an internal voltage threshold at 10°C at 2.4V, and an internal
voltage at 45°C at 0.93V as shown in Figure 9. At 25°C the voltage
at the THERM pin is set at the midpoint of the thresholds:
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.
Temperature Sensing: THERM Pin
0.93V + 2.40V - 0.93V
2
The THERM pin is provided for hot and cold battery detection and
for temperature slope termination of fast charge when used in
conjunction with an NTC thermistor. The THERM pin also
provides for hot battery and maximum temperature termination
when used in conjunction with a normally closed thermal switch.
Several internal voltage thresholds are used by the controller
depending on whether a thermistor or a thermal switch is used.
Figure 9 shows the internal thresholds over laid on a typical
thermistor curve.
=1.67V.
The THERM pin has a 75kΩ internal pull-up (Rpu). Using a
resistor divider with 10kΩ for the thermistor (Rth) and a external
fixed resistor (Rfix), the divider looks like Figure 8 at 25°C:
Figure 10: Voltage divider at the THERM pin
at 25°C
12
ICS1712
To set the voltage at the THERM pin for 1.67V at 25°C, the
equivalent divider looks like Figure 11.
Table 4: Thermistor Voltage Thresholds
Parameter
Cold Battery Thermistor
Voltage
Hot Battery Thermistor
Voltage
•
The parallel resistance R|| is calculated:
=20kΩ.
1.67V/10kΩ
The internal pull-up resistance Rpu and the parallel resistance R|| are
known so the external fixed resistor can be calculated from:
Rpu R||
<0.93
>45°C
Using an NTC thermistor for temperature slope
termination:
These thresholds correspond to a set change in thermistor
resistance when an external pull-up to 5V is used as shown in
Figure 11. Using the values calculated from the hot and cold
battery detection example, the percent change in the thermistor
resistance per minute for selected charge rates are provided. For
selected charge rates greater than C/2, the thermistor resistance
must decrease 4%/min. to terminate charge. For selected charge
rate C/2, the thermistor resistance must decrease 3%/min. to
terminate charge.
Rfix = __________ .
Rpu - R||
Substituting in known values: Rfix = 27.27kΩ. A 27kΩ standard
value is used for Rfix.
Since the thermistor resistance Rth is specified by manufacturers at
a particular temperature, the voltage across the thermistor Vth at
that temperature can be calculated from:
Vth =
>2.4
Battery
Temperature
<10°C
As a battery approaches full charge, its accelerated rate of heating
can be used to terminate fast charge by detecting the large change
in the temperature slope. The large change in temperature slope is
proportional to the thermistor voltage change per unit of time. If
the DTSEL pin is programmed for temperature slope termination,
the controller will calculate the thermistor voltage slope and
terminate based on internally set thresholds as listed in Table 1.
The threshold is 40mV per minute for selected charge rates greater
than C/2 and 28mV per minute for selected charge rate C/2. The
voltage across the thermistor must change at these rates or greater
to terminate the selected charge rate.
Figure 11: Equivalent voltage divider
R|| = 5V - 1.67V
Voltage
Rth (5V)
__________ (5V),
Rpu + R||
with the drop across the resistor divider equal to 5V. For this
example, the calculated voltage with Rth=18kΩ at 10°C is 2.37V
and with Rth =4.7kΩ at 45°C the voltage is 0.95V. Table 3 lists the
internal thresholds for hot and cold battery detection. If the voltage
across the thermistor (at the THERM pin) drops below 0.93V, the
ICS1712 will shut down due to a hot battery fault condition and
will not restart unless reset. If the voltage dropped across the
thermistor is above 2.4V before fast charge is initiated, the
ICS17012 will begin a reduced current charge. See the Cold
Battery Charging section for more information.
13
ICS1712
For example, a battery was monitored as it charged at a 1C rate in
25°C ambient. In the final minute of charge, the battery
temperature rose from 29.8°C to 31°C where full charge was
detected. With this data, the typical 10kΩ @ 25°C thermistor used
in the example above is checked to determine if its characteristics
satisfy the 4% decrease in resistance required for the last minute of
charge. The thermistor measures 8.37kΩ @ 29.8°C and 8.01kΩ at
31°C. For a 1C charge rate, the resistance must decrease at least
4%/min. or more between 29.8°C and 31°C. The percent decrease
in resistance for the thermistor is calculated as:
8.37kΩ - 8.01kΩ (100)
8.37kΩ
The 4%/min., 3%/min. and 2%/min. decrease in thermistor
resistance for the last minute of charge for the selected charge rate
are applicable for NTC thermistors other than 10kΩ @ 25°C
provided that the following requirements are met:
• An external pull-up resistor to 5V is used to provide a
• thermistor voltage of 1.67V @ 25°C.
• The thermistor resistance at 25°C does not exceed 20kΩ so
that accuracy and adequate noise immunity are maintained.
• The thermistor resistance increases by a factor of about 1.8
from 25°C to 10°C and the thermistor resistance decreases by
a factor of about 2.1 from 25°C to 45°C.
=4.30%
•
This thermistor meets the 4%/min. requirement and will result in
termination at full charge at 31°C. The thermistor must be checked
for a 4%/min. decrease in resistance for the last minute of charge
near the hot and cold battery thresholds.
A thermal switch that opens at about 45°C is recommended. The
thermal switch must be connected between the THERM pin and
ground. When the thermal switch is closed, the voltage at the
THERM pin must be below 0.5V for normal operation. When the
thermal switch opens (see Figure 12), the internal pull-up at the
THERM pin will raise the voltage above 4.2V and the ICS1712
will shut down and will not restart unless reset. Table 5 contains
the internal voltage thresholds used with a thermal switch.
The battery in the example above was charged in a 25°C ambient
with its temperature rising 31°C - 25°C or 6°C. The temperature
rise was 31°C - 29.8°C or 1.2°C in the last minute before full
charge occurred. This information is used to check the thermistor
characteristics at the ambient extremes. If the selected 1C charge
rate is initiated at 12°C, the thermistor resistance change must
decrease 4%/min. between 16.8°C and 18°C. The thermistor
resistance at 16.8°C is 13.68kΩ and at 18°C the thermistor
resistance is 13.06kΩ.
13.68kΩ - 13.06kΩ
13.68kΩ
(100)
=4.53%
VDD
The thermistor meets the 4%/min. requirement and will result in
termination of fast charge at 18°C. If the selected 1C charge rate is
initiated at 37°C, the thermistor resistance change must decrease
4%/min. between 41.8°C and 43°C. The thermistor resistance at
41.8°C is 5.48kΩ and at 43°C the thermistor resistance is 5.25kΩ.
5.48kΩ -5.25kΩ (100)
5.48kΩ
Using a thermal switch for hot battery detection:
Rpu= 75k
THERM pin
normally closed thermal switch
opens at 45ºC
=4.19%
Figure 12: Thermal switch to connection to
ground at the THERM pin
The thermistor meets the 4%/min. requirement and will result in
termination of fast charge at 43°C.
Table 5: Thermal Switch Voltage Thresholds
Parameter
Open Thermal Switch
Voltage
Closed Thermal Switch
Voltage
14
Voltage
>4.2
Battery
Temperature
>45°C
<0.5
<45°C
ICS1712
•Using no temperature sensor:
VIN pin
If a temperature sensor is not used, the THERM pin must be
grounded.
R1
Termination Selection: DTSEL Pin
The ICS1712 has the capability of either temperature slope
termination, voltage slope termination or both methods
simultaneously. The DTSEL pin has an internal 75kΩ pull-down
resistor that enables voltage slope termination as the primary
method and is the default condition. Tying the pin high enables
both temperature slope and voltage slope termination methods.
Temperature slope termination as the primary method is enabled by
tying the DTSEL pin to the CMN output (pin 4). CMN must have
an external 15kΩ or lower value pull-up resistor to VDD for proper
activation of temperature slope termination. The ICS1702 must be
reset if a new termination method is desired. Table 6 summarizes
the DTSEL pin settings. NOTE: Maximum temperature and fast
charge timer termination methods are always enabled when using
temperature slope termination. Refer to the sections on Fast
Charge Timer Termination and Maximum Temperature
Termination for more information.
# of cells
Figure 13: Resistor divider network
at the VIN pin
Power: VDD 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.
Table 6: Termination Select List
Tie DTSEL
Pin to ...
Low
(No Connect)
High
CMN
Grounding: VSS, AVSS Pins
There are two ground pins. Both pins must be connected together
at the device. This point must have a direct connection to a solid
ground plane.
Result
Voltage slope termination only
Voltage slope and temperature slope
termination
Temperature slope termination only
(CMN with external pull-up to VDD)
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 13. 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 =
R2
R1
(# of cells -1)
15
ICS1712
Data Tables
Table 7: 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.
Table 8: DC Characteristics
Parameter
Supply Voltage
Supply Current
High Level Input Voltage
SEL0, SEL1
Low Level Input Voltage
SEL0, SEL1
Low Level Input Current, pull-up
THERM, MRN
High Level Input Current, pull-down
DTSEL
High Level Source Current
CHG, DCHG
Low Level Sink Current
CHG, DCHG
Low Level Sink Current, indicator
PFN, CMN
Low Level Sink Current, indicator
OTN
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
IIL
V=0.4V
74
µA
IIH
V= VDD - 0.4V
75
µA
IOH
V= VDD - 0.4V
28
mA
IOL
V=0.4V
25
mA
IOL
V=0.4V
40
mA
IOL
V=0.4V
28
mA
Input Impedance
Analog/Digital Converter Range
0-2.2
1.0
0-2.7
0-2.7
Table 9: DC Voltage Thresholds
TAMB=25°C
PARAMETER
Minimum Battery Voltage
Maximum Battery Voltage
Thermistor - Cold Temperature
Thermistor - Hot Temperature
Thermal Switch - Open
Thermal Switch - Closed
TYP
0.5
2.0
2.4
0.93
4.2
0.5
16
UNITS
V
V
V
V
V
V
MΩ
V
ICS1712
Table 10: 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
RESET to SEL Dynamic Reprogram Period
SYMBOL
REFERENCE
tRESET
tCHG
tDCHG
tR
tDA
tCYCLE
see Figure B
see Figure A
see Figure A
see Figure A
see Figure A
see Figure A
tRSA
see Figure B
Timing Diagrams
Figure A:
Figure B:
17
TYP
1.0
700
1048
5.0
4.0
16.4
1077
5.0
100
100
624
200
7.0
1160
UNITS
MHz
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ms
ICS1712
Applications Information
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.
To ensure proper operation of the ICS1712, 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. The current may vary when using
temperature slope termination
.
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 ICS1712 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.
VIN Divider Resistors
Figure 14 shows a typical application using the ICS1712. R1 and
R2 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
R2
Open
2.0k
1.0k
1.0k
3.0k
2.0k
2.0k
1.3k
Selecting the Appropriate 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. The
temperature slope and maximum temperature termination methods
are for equipment that must remain operative while the battery is
fast charged.
If using voltage slope termination, 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
when using the voltage slope method.
18
ICS1712
•Voltage Slope Termination
•Temperature Slope and Maximum Temperature
The voltage slope termination method used by the ICS1712
requires a nearly constant current flow into the battery during fast
charge. Equipment that draws a known constant current while the
battery is charging may use the voltage slope termination method.
This constant current draw must be added to the fast charge
current. Using the voltage slope termination method for 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.
Temperature slope and/or maximum temperature termination may
have to be used for equipment that has high dynamic current
demands while operating from the battery during fast charge. Also,
users who do not have a well regulated constant current source
available may have to use temperature termination. In general,
utilizing temperature slope as the primary termination method with
maximum temperature termination as a safety back-up feature is
the best approach. When using temperature slope termination, the
actual current should not be appreciably lower than the selected
rate in order that termination of fast charge occurs due to the
battery reaching full charge rather than by the timer expiring.
Temperature termination methods require that the thermal sensor
be in intimate contact with the battery. A low thermal impedance
contact area is required for accurate temperature sensing. The area
and quality of the contact surface between the sensor and the
battery directly affects the accuracy of temperature sensing.
Thermally conductive adhesives may have to be considered in
some applications to ensure good thermal transfer from the battery
case to the sensor.
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 attentuation 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.
The thermal sensor should be placed on the largest surface of the
battery for the best accuracy. The size of the battery is also a
consideration when using temperature termination. The larger the
battery the lower the surface area to volume ratio. Because of this,
larger batteries are less capable in dissipating internal heat.
Additional considerations beyond the basics mentioned above may
be involved when using temperature slope termination where
sudden changes in ambient temperature occur or where forced air
cooling is used. For these applications, the surface area of the
thermal sensor in contact with the battery compared to the surface
area of the thermal sensor in contact with the ambient air may be
significant. For example, bead type thermistors are relatively small
devices which have far less thermal capacity compared to most
batteries. Insulating the surface of the thermistor that is in contact
with the ambient air should help minimize heat loss by the
thermistor and maintain accuracy.
When using voltage slope termination, 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.
19
ICS1712
Maximum Temperature Termination
Charging System Status by Indicator
Maximum temperature termination is best suited as a safety backup feature. Maximum temperature termination requires that the
thermal sensor be in intimate contact with the battery. A low
thermal impedance contact area is required for accurate
temperature sensing. The area and quality of the contact surface
between the sensor and the battery directly affects the accuracy of
temperature sensing. Thermally conductive adhesives may have to
be considered in some applications to ensure good thermal transfer
from the battery case to the sensor.
The Indicator Description List in Table 2 contains displays that are
caused by charging system abnormalities. At power-up or after a
reset is issued, one flash of the CMN indicator followed by a
continuous PFN indication results from a 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 a PFN fault 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
PFN fault indicator is active immediately after power-up or after a
reset is issued 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
.
If the CMN and OTN indicators are active together, this is an
indication that the battery temperature has dropped to below 10°C
after a fast charge was initiated with the battery temperature
normal. If this condition is observed and the battery temperature
did not drop after fast charge was initiated, check the thermistor
circuit mechanically for poor contact and electrically for excessive
noise.
The thermal sensor should be placed on the largest surface of the
battery for the best accuracy. The size of the battery is also a
consideration when using temperature termination. The larger the
battery, lower the surface area to volume ratio. Because of this,
larger batteries are less capable in dissipating internal heat.
Additional considerations beyond the basics mentioned above may
be involved when using maximum temperature termination where
sudden changes in ambient temperature occur or where forced air
cooling is used. For these applications, the surface area of the
thermal sensor in contact with the battery compared to the surface
area of the thermal sensor in contact with the ambient air may be
significant. For example, bead type thermistors are relatively small
devices which have far less thermal capacity compared to most
batteries. Insulating the surface of the thermistor that is in contact
with the ambient air should help minimize heat loss by the
thermistor and maintain accuracy.
20
ICS1712
V
CONSTANT
CURRENT
SOURCE
in
R3 (note 1)
+5V +5V
Q1 (note 2)
+ 5 V (note 5)
ICS1712
390
390
1k
(note 3)
+5V
CHG
VDD
unused
DCHG
16
15
PFN
6
VIN
CMN THERM
OTN DTSEL
RC
SEL0
14
7
VSS
MRN
10
8
AVSS
SEL1
9
1
2
FAULT 3
CHG 4
TEMP 5
4.7µF
.047µF
R1
27k (note 4)
13
12
11
+5V
R2
16k
.047µF
10k Ω
@ 25°C
100pF
(note 6)
Notes:
1) Value of R3 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) Resistor is needed only if a thermistor is used. Value may change depending on thermistor.
5) Regulated supply
6) Power ground; others are signal ground. Connect signal ground to power ground
at negative battery terminal only.
Figure 14: Functional Diagram
21
temperature
sense
options
open
@ 45°C
ICS1712
Package Information
0.016
0.039
0.016
QuickSaver
GPI
ICS1712S
QuickSaver
R
0.155
0.296
GPI
0.236
0.390
ICS1712M
0.404
0.041
0.405
0.031
0.058
0.094
0.024
0.154
0.008
0.006
0.016
0.041
0.008
0.050
0.025
All package dimensions are in inches.
0.296
0.016
0.008
0.008
0.050
0.033
All package dimensions are in inches.
16-Pin SOIC Package (150 mil)
16-Pin SOIC Package (300 mil)
0.060
0.018
QuickSaver
0.250
GPI
ICS1712N
0.310
0.750
0.250
0.130
0.130
0.010
0.015
0.350
0.018
0.100
0.060
All package dimensions are in inches.
Ordering Information:
ICS1712M, ICS1712MT,
ICS1712S, ICS1712ST, ICS1712N
16-Pin DIP package (300 mil)
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
22
ICS1712
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
23
ICS1712
NOTES
24
NOTES
25
ICS1712
ICS1712
NOTES
26
NOTES
27
ICS1712
ICS1712
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
March 3, 1999
GPI Sales Representative
28