ICS1700A
QuickSaver® Charge Controller for Nickel-Cadmium
and Nickel-Metal Hydride Batteries
General Description
The ICS1700A 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
ICS1700A 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 ICS1700A is a pin-for-pin replacement for the
original ICS1700 controller.
The ICS1700A 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
Features
• Multiple charge termination methods include:
- Voltage 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
DISCHARGE
TEMPERATURE
SENSE
SELECT
CHARGE
VOLTAGE
SENSE
PROCESSOR
MICROCODE CONTROL
ADC
RAM ROM
OUTPUT
CONTROL
RESET
2.0V 0.5V
HOT
COLD
CHARGE
MODE LED
CONTROL
CONTROL
POLLING/
FAULT LED
TEMPERATURE
STATUS LED
OSCILLATORRC
2
ICS1700A
Pin Configuration
Pin Definitions
ICS1700A
CHG
DCHG
PFN
OTN
CMN
AVSS
RC
THERM
VREF
VIN
VDD
SEL0
VSS MRN
SEL1
1
2
3
4
5
6
7
89
10
11
12
13
14
15
16
unused
16-Pin DIP 20-Pin SOIC
Pin Number
DIP SOIC Pin Name Type Definition
1 1 CHG OUT Active high TTL compatible signal used to turn on an external current source to provide current to charge
the battery.
2 2 DCHG OUT Active high TTL compatible signal available to turn on a discharge circuit.
33PFN OUT 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.
4 5 CMN OUT 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.
5 7 OTN OUT 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.
6 8 SEL0 IN Input used with the SEL1 pin to program the device for the desired charge rate.
79VSS Ground.
8 10 AVSS Ground.
9 11 SEL1 IN Input used with the SEL0 pin to program the device for the desired charge rate.
10 12 MRN IN Master reset signal. A logic low pulse greater than 700 ms initiates a device reset.
11 13 RC IN An external resistor and capacitor sets the frequency of the internal clock.
12 14 THERM IN Thermistor or thermal switch input for temperature sensing.
13 16 VREF 1.26V voltage reference.
14 18 VIN IN Battery voltage normalized to one cell with an external resistor divider.
15 19 unused Ground.
16 20 VDD Device supply =+5.0 VDC
Note: (DIP/SOIC)
Pin 6/8 has an internal pull-up.
Pin 9/11 has an internal pull-up.
Pin 10/12 has an internal pull-up.
Pin 12/14 has an internal pull-up.
Pins 4, 6, 15, and 17 are unconnected in the SOIC package.
3
ICS1700A
Controller Operation
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.
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.
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
Figure 1: Graphical representation of average current levels during the four charging stages
Figure 2: High impedance voltage spike at the beginning of charge
Soft-StartFastCharge Topping Charge MaintenanceCharge
Current
Time(not toscale)
(not toscale)
Stage 3 Stage 4Stage 2Stage 1
0 2 mintermination termination +2 hours
Average
4
ICS1700A
Figure 3: Cycle-to-cycle increase of the soft-start current pulse widths
Fast Charge
In the second stage, the ICS1700A 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.
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 ICS1700A can be set for four
user-selectable fast charge rates from 15 minutes (4C) to two hours
(C/2). Charge pulses occur approximately every second. The CMN
indicator is activated continuously during this stage.
Figure 4: Charge cycle showing charge and discharge current pulses
Initial Pulse
Width
cycle time cycle time cycle time
Initial Pulse
Width Initial Pulse
Width
increment
time 2 x increment
time
fastcharge pulsewidth
acquisition time
r
e
s
t
time
r
e
s
t
time
discharge pulsewidth
v
o
l
t
a
g
e
cycletime
5
ICS1700AICS1700A
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.
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 ICS1700A 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.
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.
Maintenance Charge
The maintenance charge is intended to offset the natural self-
discharge of NiCd or NiMH batteries by keeping the cells primed
at peak charge. After the topping charge ends, the ICS1700A
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.
Figure 5: Representative timing diagram for topping and maintenance charge
delaytimetime
c
y
c
l
e
time
c
y
c
l
e
6
ICS1700A
Maximum Temperature Termination
Maximum temperature can be sensed using either a NTC
thermistoror 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.
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 thresh-old. If the
thermistor voltage drops below the internal thresh-old, 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.
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 can be disabled by grounding
the THERM pin. See the section on Temperature Sensing for more
information.
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 2 for more information.
Charge Termination Methods
Several charge termination schemes, including voltage slope,
maximum temperature and a fast charge timer are available. The
voltage slope method may be used with or without 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
ICS1700A 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.
Cells that are not thoroughly conditioned or possess an unusual cell
construction may not have a normal voltage profile. The
ICS1700A 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.
Figure 6: Voltage and slope curves showing inflection and zero slope points
7
ICS1700A
Battery Fault Detection
The ICS1700A 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 ICS1700A
assumes the battery has been removed, a fault condition is
indicated by the PFN fault indicator, and the controller shuts down.
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
ICS1700A checks for a cold battery before initiating fast charge. If
a cold battery is present before fast charging begins, the ICS1700A
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 ICS1700A 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 ICS1700A 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 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.
Battery Polling
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
ICS1700A assumes no battery is attached and initiates a polling
sequence.
The ICS1700A then applies a 100ms charge pulse. During the
pulse, the ICS1700A monitors the VIN pin to determine if the
divided down terminal voltage is greater than the internal 2.0V
reference. If the battery is present, the voltage is clamped below the
2.0V reference when the current pulse is applied and the fast
charge stage begins immediately. If a battery is not present, the
voltage at VIN rises above the 2.0V reference and the PFN fault
indicator is activated.
The charge pulses repeat for 10 seconds. If the battery is installed
within 10 seconds, the ICS1700A 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
ICS1700A shuts down. A reset must be issued to restart the
controller after installing the battery.
8
ICS1700A
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 1.
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 ICS1700A is applying a topping or
maintenance charge.
The polling fault (PFN) indicator is on when the ICS1700A 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.
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.
Pin Descriptions
The ICS1700A 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.
Care must be taken to control wiring resistance and inductance.
The load resistor must be capable of handling this short duration
high-amplitude pulse.
Table 1: Indicator Description List
PFN CMN OTN Description
On Polling mode or battery fault
Flash Maintenance and topping charge
On Fast charge
On Hot battery shutdown
Flash On Cold battery charge
On on See Applications Information
On One flash See Applications Information
9
ICS1700A
Charge Rate Selection: SEL0, SEL1 Pins
The SEL0 and SEL1 inputs must be programmed by the user to
inform the ICS1700A 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 pull-up to VDD. The voltage ranges for low (L) 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 2.
The ICS1700A 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.
Table 2: Charge Rate List
SEL0 SEL1
Charge Rate Topping Charge
pulse Rate Maintenance Charge Pulse
Rate Fast Charge Timer
Duration (after reset)
L L 4C (15 min) one every 40 sec one every 160 sec 30 min
LH2C (30 min) one every 20 sec one every 80 sec 60 min
HL1C (60 min) one every 10 sec one every 40 sec 90 min
H H C/2 (120 min) one every 5 sec one every 20 sec 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.
10
ICS1700A
Figure 7: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 ICS1700A 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 7. At 25°C the voltage
at the THERM pin is set at the midpoint of the thresholds:
0.93V + 2.40V - 0.93V =1.67V.
2
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:
Master Reset: MRN Pin
The MRN pin is provided to re-program the controller for a new
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 change charge
rates or clear a temperature fault condition. Upon power-up, the
controller automatically re-sets itself.
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.
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
The THERM pin is provided for hot and cold battery detection and
for maximum temperature 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 7 shows the internal thresholds over laid on a typical
thermistor curve.
• Using an NTC thermistor for hot and cold battery
detection:
Figure 8: Voltage divider at the THERM pin
at 25°C
11
ICS1700A
To set the voltage at the THERM pin for 1.67V at 25°C, the
equivalent divider looks like Figure 9. Table 3: Thermistor Voltage Thresholds
•Using a thermal switch for hot battery detection:
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 10), the internal pull-up at the
THERM pin will raise the voltage above 4.2V and the ICS1700A
will shut down and will not restart unless reset. Table 4 contains
the internal voltage thresholds used with a thermal switch.
Figure 9: Equivalent voltage divider
The parallel resistance R|| is calculated:
R|| = 5V - 1.67V =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||
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:
Rth (5V)
Vth = __________ (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
ICS1700A 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
ICS1700A will begin a reduced current charge. See the Cold
Battery Charging section for more information.
Figure 10: Thermal switch to connection to
ground at the THERM pin
Table 4: Thermal Switch Voltage Thresholds
THERM pin
R = 75k
normally closed thermal switch
opens at 45ºC
VDD
pu
Parameter Voltage Battery
Temperature
Cold Battery Thermistor
Voltage >2.4 <10°C
Hot Battery Thermistor
Voltage <0.93 >45°C
Parameter Voltage Battery
Temperature
Open Thermal Switch
Voltage >4.2 >45°C
Closed Thermal Switch
Voltage <0.5 <45°C
12
ICS1700A
Voltage Reference: VREF Pin
A 1.26V reference is present at this pin. The reference sets internal
voltage references such as the 0.5V and 2.0V internal thresholds
used by the controller for battery polling/fault detection and the
analog/digital converter range.
The reference provides a fast way of checking the internal
thresholds. Measuring VREF with a high input impedance volt
meter (>1MΩ) is required. The reference can only be used if it is
buffered with a high impedance device having an input impedance
greater than 1MΩ. Buffering is essential to ensure that the internal
voltage thresholds and analog/digital converter range and
resolution are not altered.
The reference may be overridden by an external 1.2V to 1.3V
reference.
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.
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.
• Using no temperature sensor:
If a temperature sensor is not used, the THERM pin must be
grounded.
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 11. 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 = R1
(# of cells -1)
Figure 11: Resistor divider network
at the VIN pin
R1 R2
VIN pin
# of cells
13
ICS1700A
Data Tables
Table 5: Absolute Maximum Ratings
Table 6: DC Characteristics
Table 7: DC Voltage Thresholds
Supply Voltage 6.5 V
Logic Input Levels -0.5 to VDD + 0.5 V
Ambient Operating Temperature 0 to 70 °C
Storage Temperature -55 to 150 °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.
TAMB=25°CPARAMETER TYP UNITS
Minimum Battery Voltage 0.5 V
Maximum Battery Voltage 2.0 V
Thermistor - Cold Temperature 2.4 V
Thermistor - Hot Temperature 0.93 V
Thermal Switch - Open 4.2 V
Thermal Switch - Closed 0.5 V
Tamb=25°C. All values given are typical at specified VDD.
Parameter Symbol Test Conditions MIN TYP MAX UNITS
Supply Voltage VDD 4.5 5.0 5.5 V
Supply Current IDD 7.3 mA
High Level Input Voltage
SEL0, SEL1 VIH 3.6 4.1 4.5 V
Low Level Input Voltage
SEL0, SEL1 VIL 0.73 0.75 0.8 V
Low Level Input Current, pull-up
THERM, MRN IIL V=0.4V 74 µA
High Level Source Current
CHG, DCHG IOH V= VDD - 0.4V 28 mA
Low Level Sink Current
CHG, DCHG IOL V=0.4V 25 mA
Low Level Sink Current, indicator
PFN, CMN IOL V=0.4V 40 mA
Low Level Sink Current, indicator
OTN IOL V=0.4V 28 mA
Input Impedance 1.0 MΩ
Analog/Digital Converter Range 0-2.2 0-2.7 0-2.7 V
Voltage Reference VREF 1.20 1.26 1.31 V
14
ICS1700A
Table 8: Timing Characteristics
Timing Diagrams
Figure A:
Figure B:
R≈16kΩ, C≈100pFPARAMETER SYMBOL REFERENCE TYP UNITS
Clock Frequency 1.0 MHz
Reset Pulse Duration tRESET see Figure B 700 ms
Charge Pulse Width tCHG see Figure A 1048 ms
Discharge Pulse Width tDCHG see Figure A 5.0 ms
Rest Time tRsee Figure A 4.0 ms
Data Acquisition Time tDA see Figure A 16.4 ms
Cycle Time tCYCLE see Figure A 1077 ms
Capacitor Discharge Pulse Width 5.0 ms
Capacitor Discharge Pulse Period 100 ms
Polling Detect Pulse Width 100 ms
Polling Detect Pulse Period 624 ms
Soft Start Initial Pulse Width 200 ms
Soft Start Incremental Pulse Width 7.0 ms
RESET to SEL Dynamic Reprogram Period tRSA see Figure B 1160 ms
15
ICS1700A
Voltage Slope Termination
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
voltage slope termination method works best with a constant
current flow into the battery during fast charge. If equipment draws
a known constant current while the battery is charging, this current
should be added to the fast charge cur-rent. Equipment that
randomly or periodically requires current from the battery during
fast charge needs evaluation to ensure it does not interfere with the
proper operation of the voltage slope termination method.
Charging sources that produce decreasing current as fast charge
progresses may 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 characteristics that can 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.
The controller soft start stage, built-in noise filtering, and fast
charge timer operate optimally when the constant cur-rent 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.
Applications Information
To ensure proper operation of the ICS1700A, external components
must be properly selected. The external current source used must
meet several important criteria to ensure optimal performance of
the charging system.
VIN Divider Resistors
Figure 12 shows a typical application using the ICS1700A. 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 R1 R2
1Short Open
22.0k 2.0k
32.0k 1.0k
43.0k 1.0k
512k 3.0k
610k 2.0k
712k 2.0k
89.1k 1.3k
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 ICS1700A 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.
16
ICS1700A
Charging System Status by Indicator
The Indicator Description List in Table 1 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.
Enhanced Performance Characteristics
The ICS1700A is an enhanced performance, pin-for-pin re-
placement for the original ICS1700. Improved internal features
provide additional capabilities. The charge sequence, voltage slope
termination method, and analog-to-digital converter resolution
allow the ICS1700A to charge either NiMH or NiCd batteries. The
ICS1700A accepts either a thermal switch or thermistor input for
temperature sensing. The polling mode for battery detection
responds quickly to the removal of the battery throughout the
charge sequence. The reset input debounce eliminates sensitivity to
field effects and ground bounce when the PC board design
recommendations cited in this document are employed. The
temperature sense input debounce eliminates sensitivity to shock
and vibration associated with the use of a thermal switch.
Maximum Temperature Termination
Maximum temperature termination is best suited as a safety back-
up 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 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.
17
ICS1700A
Figure 12: Functional Diagram
+ 5 V
1
2
3
4
5
6
7
89
10
11
12
13
14
15
16
ICS1700A
CHG
DCHG
PFN
CMN
OTN
SEL0
VSS
AVSS SEL1
MRN
RC
THERM
VREF
VIN
VDD
CONSTANT
CURRENT
SOURCE
Vin
+ 5 V (note 5)
4.7µF .047µF
.047µF
10k
@ 25°C open
@ 45°C
+ 5 V
R1
R2
R3 (note 1)
27k (note 4)
100pF
16k
Q1 (note 2)
1k
(note 3)
390
FAULT
CHG
TEMP
Ω
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.
(note 6)
temperature
sense
options
unused
+ 5 V
+ 5 V
390
18
ICS1700A
0.018
0.050
0.008
0.092
0.039
0.504
0.041
0.041
0.406
0.294
0.008
All package dimensions are in inches.
0.289
0.0290.018
QuickSaver
GPI
ICS1700AM
20-Pin SOIC Package (300 mil)
0.016
0.050
0.006
0.064
0.025
0.390
0.031
0.024
0.236
0.155
0.008
All package dimensions are in inches.
QuickSaver
GPI ICS1700AS
0.031
0.029
0.154
16-Pin SOIC Package (150 mil)
0.018
0.100
0.029
0.130
0.355
0.750
0.130
0.300
0.260
All package dimensions are in inches.
0.060
0.010
0.260
0.0180.060
QuickSaver
GPI
ICS1700AN
16-Pin DIP Package
ICS 1700A ST
Package Information
Ordering Information:
ICS1700AM, ICS1700AMT,
ICS1700AS, ICS1700AST, ICS1700AN
Example:
Prefix: ICS = Intelligent Charging Solution
Device type: Consists of 3 to 5 digits or numbers
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
19
ICS1700A
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 nickel-
metal 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
20
ICS1700A
NOTES
21
ICS1700A
NOTES
22
ICS1700A
NOTES
23
ICS1700A
NOTES
24
ICS1700A
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 19, 1999
GPI Sales Representative
