LM3647
Universal Battery Charger for Li-Ion, Ni-MH and Ni-Cd
Batteries
General Description
The LM3647 is a charge controller for Lithium-Ion (Li-Ion),
Nickel-Metal Hydride (Ni-MH) and Nickel-Cadmium (Ni-Cd)
batteries. The device can use either a pulsed-current
charging or a constant-current charging technique. The
device can also be configured to discharge before charging.
Throughout the charging sequence the LM3647 monitors
voltage and/or temperature and time in order to terminate
charging.
Charge termination methods are:
Negative delta voltage (-
V)
Optional: Delta temperature/delta time (
T/
t)
Backup: Maximum temperature
Backup: Maximum time
Backup: Maximum voltage
If both voltage and temperature fail to trigger the termination
requirements, then the maximum time (configured by
external hardware) steps in which terminates the charging.
In Ni-Cd/Ni-MH mode, four different charging stages are
used:
Soft-start charge
Fast charge
Topping charge
Maintenance charge
In Li-Ion mode, four different charging stages are used:
Qualification
Fast Charge Phase 1, Constant Current
Fast Charge Phase 2, Constant Voltage
Maintenance charge
The charge current of the LM3647 is configured via external
resistors, which in turn controls the duty cycle of the PWM
switching control output. For cost-sensitive applications, the
LM3647 charge controller cab be configured to use an
external current source and no temperature sensor.
When using an external current source, the current is
controlled by the LM3647 which turns the current source on
and off. The LM3647 automatically detects the presence of a
battery and starts the charging procedure when the battery is
installed. Whenever an error occurs (e.g., short circuit,
temperature too high, temperature too low, bad battery,
charge time over, etc.) the LM3647 will stay in error mode
until the battery is removed or it gets within the allowed
charging temperature range. The LM3647 is available in a
standard 20-lead SOIC surface mount package.
Features
n
Auto-adaptive fast charge
n
High-resolution, accurate voltage monitoring prevents
Li-Ion undercharge or overcharge
n
Fast charge, pre-charge and maintenance currents are
provided. Different currents are selectable via external
resistors.
n
Fast-charge termination by
temperature/
time,
maximum voltage, maximum temperature, negative
voltage and maximum time
n
Dynamically detects battery insertion, removal, short
circuit and bad battery without additional hardware
n
Supports charging of battery packs with 28 cells of
Ni-Cd/Ni-MH or 14 cells of Li-Ion (1 cell of NiCd/NiMH
can be supported by added external 2x voltage
amplifier)
n
Three optional LED indicators and Buzzer output
indicate operational modes
n
Ni-MH/Ni-Cd charge mode, Li-Ion charge mode or
discharge mode can be selected manually
n
Supports control of current feedback power supply and
constant current power supply
Applications
n
Battery charging systems for:
-- Portable consumer electronics
-- Audio/video equipment
-- Communications equipment
-- Point of sale devices
-- Power tools
-- Personal convenience products
March 2001
LM3647
Universal
Battery
Charger
for
Li-Ion,
Ni-MH
and
Ni-Cd
Batteries
2001 National Semiconductor Corporation
DS101318
www.national.com
2.0 Connection Diagram
2.1 PIN DESCRIPTIONS
Pin No.
Name
I/O
Description
1
SEL3
I
Input to Select Power Source or Li-Ion Cell Voltage
2
SEL4
I
Input to Select Maintenance Charge Time Out, Connected to an
RC-Network
3
RCIN
RC-Timing Pin
4
GND
Ground
5
V
CC
5V, Power Supply
6
RESET
I
Reset Pin, Active Low
7
LED1
O
LED Output
8
LED2
O
LED Output
9
LED3
O
LED Output
10
V
REF
I
Voltage Reference Analog Input
11
CEXT
External Capacitor
12
CEL
I
Battery Voltage Input (through resistor divider)
13
CS
I
Current Sense Input
14
TEMP
I
NTC-Temperature Sensor Input
15
DISCHG
O
High when Discharging, Else Low
16
SYSOK
O
System Monitor Output
17
BUZZER
O
Buzzer Output
18
PWM
O
Charge Control Output
19
SEL1
I
Tri-Level Input, Discharge/Maintenance Charge Select
20
SEL2
I
Tri-Level Input, Battery Type Select (NiCd, NiMH, Li-Ion)
2.2 ORDERING INFORMATION
Device
Package
Temperature
LM3647
20 SOIC
-40C to +85C
DS101318-2
Top View
Order Number LM3647IM
See NS Package Number M20B
LM3647
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2
Typical Application
DS101318-1
LM3647
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3
3.0 Electrical Characteristics
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Voltage
(V
CC
)
7V
Voltage at Any Pin
-0.3V to V
CC
+0.3V
Total Current into
V
CC
Pin (Source)
100 mA
Total Current out of
GND Pin (Sink)
110 mA
Storage Temperature
Range
-65C to +140C
Note 1: Note: Absolute Maximum Ratings indicate limits beyond which
damage to the device may occur. DC and AC Electrical Specifications are not
ensured when operating the device at absolute maximum ratings.
DC Electrical Characteristics
-40C
T
A
+85C unless otherwise specified.
Parameter
Conditions
Min
Typ
Max
Units
Operating Voltage
4.5
5.5
V
Supply Current
2.5
mA
LED-pin Sink Current
7.5
15
mA
Temperature Input Levels
Ni-Cd/Ni-MH Upper Limit
(Voltage at TEMP-pin)
3.15
V
Li-Ion Upper Limit
(Voltage at TEMP-pin)
3.0
V
Lower Limit
(Voltage at TEMP-pin)
0.5
V
Start Limit
(Voltage at TEMP-pin)
2.2
V
L-Ion (for both 4.1 and 4.2V Cells)
Maintenance Charge Minimum Voltage
(CEL pin)
2.6
V
Maintenance Charge Restart Voltage
(CEL pin)
2.153
V
Good Battery Threshold
(CEL pin)
1.2
V
Maintenance Current
(Voltage at CS-pin)
2.3
V
Maintenance Current Lower Threshold
(Voltage at CS-pin)
2.42
V
Minimum Current Fast Charge
Termination
(Voltage at CS-pin)
2.3
V
Qualification Current
(Voltage at CS-pin)
2.3
V
Maximum Charging Current
(Voltage at CS-pin)
1.5
V
Ni-Cd/Ni-MH
Maximum Battery Voltage
(CEL pin)
3.017
V
Maximum Battery Current
(Voltage at CS-pin)
1.5
V
Battery Presence Limit
(CEL pin)
1.0
V
Discharged Battery Limit
(CEL pin)
1.7
V
Good Battery Threshold
(CEL pin)
1.2
V
Soft Start Current
(Voltage at CS-pin)
2.3
V
Topping Charge Current
(Voltage at CS-pin)
2.3
V
Maintenance Charge Current
(Voltage at CS-pin)
2.425
2.45
V
V
REF
2.5
V
AC Electrical Characteristics
Parameter
Conditions
Min
Typ
Max
Units
RCIN Frequency
R = 3.3 k
, C = 68 pF
2.5
MHz
Fast-PWM Frequency
250
Hz
Slow-PWM Frequency
0.1
Hz
LM3647
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4
4.0 Functional Description
4.1 GENERAL
The LM3647 can be configured to charge three different
types of batteries: Ni-Cd, Ni-MH and Li-Ion. The charger
behavior for Ni-Cd and Ni-MH is similar but the charge
curves will appear slightly different due to the differences
in chemistry. The Ni-Cd/Ni-MH charging algorithm is
divided into four phases:
Soft Start:
The LM3647 detects that a battery is
connected and optionally verifies that the
temperature is within safe operating limits
(approx. -5C to +50C). Charging starts
with a current of 0.2C and switches into
the next phase after approx. 5 minutes.
Error termination will be triggered by
Maximum Battery Voltage (CEL-pin
>
3.017V) or if the battery voltage does not
reach the defective battery level (CEL-pin
<
1.2V).
Fast Charge: Constant current is applied to the battery
and the LM3647 monitors voltage and
temperature (optional). Switching into the
next phase will appear after a voltage drop
in the charging curve: Ni-Cd
50 mV/cell
and Ni-MH
17 mV/cell. Error termination
will be triggered by over-temperature.
Topping
Charge:
A current of 0.2C is applied to the battery
for a user defined time (RC network at
SEL4).
Maintenance
Charge:
Is
user
selectable
and
is
a
fixed
percentage of the Fast Charge rate.
Discharge before charge is user select-
able.
Ni-Cd Charging Curve:
Ni-MH Charging Curve:
The Li-Ion charging algorithm is also divided into four
phases:
Qualification: The LM3647 detects that a battery is
connected and verifies that the temperature (optional
but highly recommended for safety reasons) is within
limit. Charging starts with a current of 0.2C and
switches into next phase after approx. 1 minute. Error
termination will be triggered if the battery voltage does
not reach the Li-Ion battery qualification level (CEL-pin
<
1.2V) within one minute.
Fast Charge Constant Current: Battery voltage will
rise until Maximum Battery Voltage (CEL-pin = 2.675V
or 2.74V depending on SEL3) is reached.
Fast Charge Constant Voltage: Keeps the voltage
constant until the current has decreased below the
threshold (CS at 2.3V).
Maintenance Charge: Is user selectable and is a
fixed percentage of the Fast Charge rate.
4.2 ADVANCED PIN DESCRIPTIONS
SEL1 is a selection pin to control the LM3647 discharge
and maintenance charge modes. The pin has three
states: tied to V
CC
, GND, or unconnected (Hi-Z). When
the charger is configured to charge Ni-Cd or Ni-MH
batteries, this pin determines if the charger discharges
the battery before charging or if the charger shall only
maintenance charge the battery. When the charger is
configured for Li-Ion batteries, this pin determines how
the charger behaves during maintenance charge.
SEL1
Charge mode
condition SEL2 = GND (NiCd) or V
CC
(NiMH)
V
CC
No discharge before charge
GND
Maintenance charge only (no fast charge)
Open
Discharge before charge
SEL1
Charge mode
condition SEL2 = Open (Li-Ion)
V
CC
Maintenance charge indefinite
GND
Maintenance charge indefinite, restart
fast-charge if battery gets discharged (load
connected)
Open
No maintenance charge, restart fast charge
if battery becomes discharged
SEL2 is a selection pin to determine the battery type to be
charged. The pin has three states: tied to V
CC
(Ni-MH), GND
(Ni-Cd), or unconnected (Li-Ion).
SEL2
Battery Type Select
V
CC
Ni-MH
GND
NiCd
Open
Li-Ion
SEL3 is a selection pin used to set charger hardware modes.
The pin has two states: tied to V
CC
or GND. When the
LM3647 is configured for Ni-Cd/Ni-MH batteries, this pin
selects between a power supply with current feedback when
tied to V
CC
(PWM "fast" frequency) or a constant current
DS101318-3
DS101318-4
DS101318-5
LM3647
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