PHILIPS NE57610BDH Li-ion battery charger control with adjustable threshold Datasheet

INTEGRATED CIRCUITS
NE57610
Li-ion battery charger control
with adjustable thresholds
Product data
2002 Nov 05
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
DESCRIPTION
The NE57610 is a one- or two-cell, Li-ion battery charger controller
which includes: constant-current and constant-voltage charging, a
precise charge termination, pre-charging of undervoltage cells,
overcharge timer, and under- and over-temperature detection.
The NE57610 is available in the very small TSOP-24A package.
FEATURES
APPLICATIONS
• 30 mV per cell charging accuracy from 0 °C to +50 °C
• Low quiescent current
• Undervoltage pre-charge conditioning and timer
• Battery overtemperature detection and protection
• Input voltage OK detection
• Self-discharge maintenance charging
• Overcharge timer
• LED drivers
• Controls charging of Lithium-ion batteries
SIMPLIFIED SYSTEM DIAGRAM
BCP51
+Vin
PBYR
240CT
RCS
V+
BATTERY PACK
150 Ω
18
RED
VCC
GRN
17
15
DRV
CS
BAT1
BAT2
22
RED
TP1
GRN
TP2
21
10 µF
NE57610
23
OSC1
VREF
OSC2
TMP
13
14
3
4
CELL 2
TP1
TP2
5
CDLL 1
ROSC
24
12
THERM
ON/OFF RESET GND PGND
CT
2
1
6
7
–Vin
V–
SL01863
Figure 1. Simplified system diagram.
2002 Nov 05
2
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
ORDERING INFORMATION
PACKAGE
NAME
DESCRIPTION
TEMPERATURE
RANGE
NE57610BDH
TSOP24A
24-pin thin small outline
–20 °C to +70 °C
NE57610EDH
TSOP24A
24-pin thin small outline
–20 °C to +70 °C
NE57610YDH
TSOP24A
24-pin thin small outline
–20 °C to +70 °C
TYPE NUMBER
Voltage options
Part number
Output voltage
Over-voltage detection threshold
Cells
NE57610BDH
8.4 V
8.7 V
2-cell
NE57610EDH
4.2 V
4.35 V
1-cell
NE57610YDH
4.1 V
4.35 V
1-cell
MAXIMUM RATINGS
SYMBOL
PARAMETER
Min.
Max.
UNIT
VCC(max)
Power supply voltage
–0.3
15
V
Tamb
Ambient temperature
–20
+70
°C
Tstg
Storage temperature
–40
+125
°C
PD
Power dissipation
–
250
mW
PIN CONFIGURATION
ON/OFF
1
24 OSC2
RESET
2
23 OSC1
TP1
3
22 R_LED
TP2
4
21 G_LED
VREF
5
20 VINOK
GND1
6
GND2
7
18 VCC
ADJ1
8
17 DRV
ADJ2
9
16 COMP
19 ADJ5
NE57610
ADJ3 10
15 CS
ADJ4 11
14 BAT2
TEMP 12
13 BAT1
SL01846
Figure 2. Pin configuration.
2002 Nov 05
3
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
PIN DESCRIPTION
PIN
SYMBOL
I/O
1
ON/OFF
I
ON/OFF: When LOW, the charger operates. When HIGH, it inhibits all functions of the charger.
2
RESET
I
RESET: In a LOW state all charger functions are enabled. When the pin is brought HIGH, all of the charger
functions are inhibited and when brought to a LOW state again, all of the timers are initialized and the start-up
functions are enabled.
3
TP1
O
Test Point 1: This pin is the output of the center counter of the pre-charger timer counter. This pin will slowly
toggle between a HIGH state and a LOW state during the pre-charge period.
4
TP2
O
Test Point 2: This pin is the output of the center counter in the high-rate charger counter. This pin will slowly
toggle between a HIGH state and a LOW state during the high-rate charging period.
5
VREF
O
Reference voltage: This is an output of a temperature stabilized 1.2 V reference. It is used in the bias of the
thermocouple and for adjustment of the ADJ1–ADJ4 pins.
6
GND1
–
Ground.
7
GND2
–
Ground.
8
ADJ1
I
Overcurrent threshold adjustment pin: This pin is internally set to 1.16 V. The overvoltage trip point is set
too high at this voltage to become active. This is useful where the input power source is a current-limited wall
transformer. It may be adjusted by referring to ‘Use of the ADJ1–ADJ4 pins’.
9
ADJ2
I
Charge termination current threshold adjustment pin: At the top-of-charge, when the charge current falls
below this level, the charging cycle is terminated. This pin is internally set to 62 mV. It may be adjusted by
referring to ‘Use of the ADJ1–ADJ4 Pins’.
10
ADJ3
I
Pre-charge current adjustment pin: This adjusts the amount of current entering the battery during the
pre-charge period. It is internally set to 120 mV. It may be adjusted by referring to ‘Use of the ADJ1–ADJ4 Pins’.
11
ADJ4
I
High-rate current adjustment pin: This pin controls the amount of charge current during the high-rate of
charge period. The pin is internally set to 89 mV. It may be adjusted by referring to ‘Use of the ADJ1–ADJ4
Pins’.
12
TEMP
I
Battery temperature sensing pin: This pin inhibits the charging process if the voltage presented to this pin
falls outside an acceptable temperature range. The external voltage is created by resistor network that includes
a thermocouple.
13
BAT1
I
Battery voltage sensing pin: This pin senses the battery voltage.
14
BAT2
I
Battery voltage and current sensing pin: This pin senses battery voltage but also is one of the two leads
for sensing charging current. (CS is the other current sensing pin.)
15
CS
I
Current sensing pin: This pin is one of the two current sensing pins. (BAT2 is the other pin.)
16
COMP
I
Current regulation amplifier compensation pin: It is recommended that around 100 pF be connected
between this pin and the DRV pin. This capacitor improves the phase margin of the system.
17
DRV
O
External PNP transistor base drive pin: This pin directly drives the base of an external PNP bipolar
transistor.
18
VCC
I
The positive voltage supply pin.
19
ADJ5
I
Full charge termination voltage adjust pin:
by 15 mV.
20
VINOK
I
Input voltage overvoltage indicator: This pin is LOW if the input voltage is over the maximum input voltage.
The pin is HIGH when the input voltage is not above the maximum input voltage.
21
G_LED
O
Green LED driver pin. This is an open collector output which is connected to a green LED though a series
resistor to limit the current to less than 20 mA to the input voltage.
22
R_LED
O
Red LED driver pin. This is an open collector output which is connected to a red LED though a series resistor
to limit the current to less than 20 mA to the input voltage.
23
OSC1
O
Oscillator out pin: This pin is connected through a timing resistor to the OSC2 pin to set the frequency of the
oscillator and the period of the timers.
24
OSC2
I
Oscillator in pin: This pin is connected through a timing resistor to the OSC1 pin and a timing capacitor to
VSS. This sets the frequency of the oscillator and the period of the timers.
2002 Nov 05
DESCRIPTION
4
This pin, when grounded will increase the termination voltage
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
DC ELECTRICAL CHARACTERISTICS
Characteristic of the NE57610Y.
SYMBOL
PARAMETER
CONDITIONS
Pin
Min.
Typ.
Max.
UNIT
ICC
Supply current
18
–
5.0
7.0
mA
VREF
Reference voltage
5
–
1.207
–
V
VADPL
AC Adaptor detection voltage L
20
2.35
2.45
2.55
V
VADPL(hys)
AC Adaptor detection voltage L
Hysteresis voltage
20
50
100
150
mV
VADPH
AC Adaptor detection voltage H
20
6.1
6.3
6.5
V
VADPH(hys)
AC Adaptor detection voltage H
Hysteresis voltage
20
50
100
150
mV
ZADPL
Impedance for AC Adaptor detection
output L
20
–
30
–
kΩ
IBAT
BAT pin leakage current
13, 14,
15
–
–
1
µA
VBAT
BAT pin output voltage
Tamb = 0 ∼ +50 °C
13
4.070
4.100
4.130
V
VDRV
DRV pin output voltage
IDRV = 20 mA
17
–
–
0.5
V
ION/OFF
ON/OFF pin input current
1
40
60
80
µA
VON/OFF
ON/OFF pin input voltage H
ON/OFF: OFF
1
0.6
–
1.20
V
VON/OFF
ON/OFF pin input voltage L
ON/OFF: ON
1
–
–
0.25
V
60
VCC: H → L
VCC: L → H
80
µA
1.20
V
0.25
V
0.24
V
26
31
mV
13
18
23
mV
1.90
2.00
2.10
V
13
25
50
100
mV
13
2.80
2.90
3.00
V
13
25
50
100
mV
VBAT: H → L
13
3.85
3.90
3.95
V
VBAT: L → H
13
4.30
4.35
4.40
V
Battery temperature detection voltage H
Low temperature 3 °C ± 3 °C
detection
12
0.835
0.860
0.885
V
VTL1
Battery temperature detection voltage L1
High temperature 43 °C ± 3 °C
detection (charging start)
12
0.390
0.413
0.435
V
VTL2
Battery temperature detection voltage L2
High temperature 50 °C ± 3 °C
detection (during charging)
12
0.335
0.353
0.370
V
IT
TDET input bias current
12
–
30
150
nA
VLEDR
R_LED pin output voltage
ILEDR = 10 mA
22
–
–
0.4
V
VLEDG
G_LED pin output voltage
ILEDG = 10 mA
21
–
–
0.4
V
∆T
Timer error time
Not including external
deviation (Note 2)
21, 22
–10
–
10
%
Ireset
RESET pin input current
2
40
Vreset(high)
RESET pin input voltage H
Charge control circuit: OFF
2
0.6
Vreset(low)
RESET pin input voltage L
Charge control circuit: ON
2
VL1
Current limit 1
Quick charge
14, 15
0.20
0.22
VL2
Current limit 2
Pre-charge
14, 15
21
VF
Full charge detection
RCS ⋅ Icharge
14, 15
VLV
Undervoltage voltage detection voltage
VBAT: L → H
13
VLV(hys)
Low voltage detection voltage Hysteresis
voltage
VP
Pre-charge detection voltage
VP(hys)
Pre-charge detection voltage Hysteresis
voltage
VR
Re-charge detection voltage
VOV
Overvoltage detection voltage
VTH
VBAT: L → H
NOTES:
1. Current limits 1 and 2 and full charge detection are specified as current detection resistor voltage drop.
2. Use a capacitor with good temperature characteristics in the oscillator. Capacitor deviation will contribute to timer error.
2002 Nov 05
5
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
TIMING DIAGRAMS
Typical timing for the NE57610Y.
5.5 V
VCC
0V
5.5 V
VCC
4.1 V
BAT PIN
VOLTAGE
0V
3.9 V
2.9 V
2V
BAT PIN
VOLTAGE
CHARGING
CURRENT
PRE–
CHARGE
CHARGING
CURRENT
SUSTAINING
CHARGE
CHARGING
FULLY
CHARGED
R_LED
ON
4.35 V
VOLTAGE AT BAT PIN
OVERVOLTAGE
FOR 0.5 s OR LONGER
0A
R_LED
OFF
ON
G_LED
OFF
SL01848
G_LED
OFF
ON
OFF
SL01847
Figure 3. Normal charging.
Figure 4. Battery overcharge detection.
5.5 V
5.5 V
VCC
BAT PIN
VOLTAGE
CHARGING
CURRENT
VCC
2 V OR LESS
0V
NO BATTERY
VOLTAGE CHANGE
BATTERY VOLTAGE
2.9 V OR MORE
14 s
0V
BAT PIN
VOLTAGE
1 mA CHARGING
0A
CHARGING
CURRENT
4 HOURS
R_LED
R_LED
FULL CHARGE
ON/OFF0.57 Hz
OFF
G_LED
SL01849
OFF
SL01850
Figure 5. Battery overdischarge detection.
2002 Nov 05
0A
ON
ON/OFF 0.57 Hz
G_LED
0V
BATTERY VOLTAGE
BELOW FULL CHARGE
Figure 6. Battery charge time-out.
6
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
TIMING DIAGRAMS (continued)
Typical timing for the NE57610Y.
5.5 V
5.5 V
VCC
VCC
BATTERY VOLTAGE
2 V OR LESS
0V
BATTERY VOLTAGE
2.9 V OR LESS
0V
BAT PIN
VOLTAGE
4.1 V
BAT PIN
VOLTAGE
15 MINUTES
CHARGING
CURRENT
0.11 SECONDS
12% OF
FULL CHARGE
R_LED
CHARGING
CURRENT
0A
ON
0A
R_LED
ON
OFF
G_LED
OFF
ON
ON/OFF0.57 Hz
G_LED
OFF
SL01851
SL01852
Figure 7. Conditioning charge failure.
Figure 8. Battery full charge detection.
7V
5.5 V
VCC
VCC
0V
0V
BAT PIN
VOLTAGE
3.9 V
BAT PIN
VOLTAGE
3V
CHARGING
CURRENT
0A
56 ms
FULL CHARGE
0A
CHARGING
CURRENT
R_LED
OFF
ON
R_LED
OFF
G_LED
ON
OFF
G_LED
OFF
SL01854
SL01853
Figure 9. Battery topping-off charge.
Figure 10. Supply (adaptor) overvoltage detection.
5V
VCC
0V
BAT PIN
VOLTAGE
3V
CHARGING
CURRENT
0A
R_LED
OFF
G_LED
OFF
SL01855
Figure 11. Temperature detection pin open.
2002 Nov 05
7
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
4.15
3.95
4.14
3.94
RE-CHARGE DETECTION VOLTAGE (V)
BAT PIN OUTPUT VOLTAGE (V)
TYPICAL PERFORMANCE CURVES
4.13
4.12
4.11
4.10
4.09
4.08
4.07
4.06
4.05
–25
0
25
50
3.93
3.92
3.91
3.90
3.89
3.88
3.87
3.86
3.85
–25
75
AMBIENT TEMPERATURE, Tamb (°C)
0
25
50
SL01856
SL01857
Figure 12. BAT output voltage versus temperature.
Figure 13. Re-charge detection voltage versus temperature.
0.5
0.5
Tamb = 25 °C
Tamb = 25 °C
0.4
LED VOLTAGE (V)
0.4
DRV VOLTAGE (V)
75
AMBIENT TEMPERATURE, Tamb (°C)
0.3
0.2
0.3
G
0.2
R
0.1
0.1
0
0
1
10
100
1
DRV CURRENT (mA)
10
LED CURRENT (mA)
SL01858
SL01859
Figure 14. DRV voltage versus DRV current.
2002 Nov 05
100
Figure 15. LED voltage versus LED current.
8
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
TECHNICAL DISCUSSION
If charging begins with the cell voltage below the overdischarged
voltage rating of the cell (VUV), it is very important to slowly raise the
cell voltage up to this overdischarged voltage level. This is done with
a reconditioning charge. A small amount of current is allowed into
the cell, and the cell voltage is allowed, for a pre-set period of time,
to rise to the overdischarged voltage (VUV). If the cell voltage
recovers, a normal charging sequence can begin as described
above. If the cell does not reach the overdischarged voltage level,
then the cell is considered too damaged to charge and the charge is
discontinued.
Lithium-ion cells: general information
Lithium-ion and polymer cells have higher voltage than nickel
cadmium (NiCd) or nickel metal hydride (NiMH) rechargeable cells.
The average operating voltage of a lithium-ion or polymer cell is
3.6 V compared to the 1.2 V of NiCd and NiMH cells. The internal
resistances of the various types of lithium cells are 50 mΩ to
300 mΩ, compared to the 5 mΩ to 50 mΩ of the nickel chemistries.
This makes Lithium-ion and polymer cells better for lower battery
current applications, less than 1 ampere, such as cellular and
wireless telephones, palmtop and laptop computers, etc.
It is important to allow enough time to charge the cell to take
advantage of the higher energy density of the lithium cells. When the
charger switches from constant current charge to constant voltage
charge (Point B, Figure 16) the cell only contains about 80 percent
of its full-rated capacity. When the cell is 100 mV less than its full
rated charge voltage, the capacity contained within the cell is about
95 percent. Allowing the cell to slowly complete its charge takes
advantage of the larger capacity of the lithium cells. The complete
charging curve can be seen in Figure 16.
Lithium-ion and polymer cells are safe as long as the cell is
maintained within a particular set of operating boundaries. The cells
have a porous carbon, or graphite anode where individual lithium
ions can lodge themselves within the pores. This keeps the lithium
ions separated, and any hazardous condition is avoided, if the cell is
kept within the safe operating boundaries.
A lithium cell protection circuit is placed within the battery pack. It
monitors the level of voltage across each cell for overcharge and
overdischarge conditions, and the discharge current in the event of
an overcurrent or short-circuit condition. If the lithium cell is
overcharged, pure metallic lithium plates out onto the surface of the
anode. Also volatile gas is generated within the cell. This creates a
hazard. Conversely, if the cell were allowed to over-discharge (Vcell
less than typically 2.3 V), the chemistry of the cell changes and the
copper metal used in its construction enters the electrolyte solution.
This severely shortens the cycle life of the cell, but presents no
future safety hazard. When the cell experiences high charge or
discharge currents, then the internal series resistance of the cell
creates heating and generation of the volatile gas which could again
present a hazard.
CHARGE CURRENT (%C)
1.0
0.5
CONSTANT
CURRENT
Charging lithium cells
1.0
An integral part of any Li-ion battery system is a battery charger
specifically designed for the lithium cell being used, with its
particular over and undercharge limits, capacity, etc. The battery
charger should be viewed as a part of the entire lithium battery
system so that safe cell operation can be ensured.
2.0
TIME (HOURS)
OPEN-CIRCUIT CELL VOLTAGE (V)
Vov
Lithium cells must be charged with a dedicated charging controller
such as the NE57610. The charging ICs, in general, can be
described as performing: a current-limited, constant-voltage charge
process. When the cell is very discharged, the charger IC outputs a
constant current into the battery, which limits the internal heating of
the cells. The maximum charge rate is typically the capacity rating of
the cell. That is, the maximum charge current is the mAHr rating of
the cell(s), that is, a 1000 mAHr cell will be charge with a maximum
of 1000 mA. When the cell voltage approaches its full-charged
voltage rating (VOV), the current entering the cell begins to
decrease, and the charger IC provides a constant voltage-mode of
charge. The charge current begins to exponentially decrease over a
long period of time (approximately 1.5 – 2.0 hours). When the
charge current falls below a preset amount, the charge current is
discontinued.
2002 Nov 05
CONSTANT
VOLTAGE
4.0
Point B
3.0
1.0
2.0
TIME (HOURS)
Figure 16. Lithium-ion charging curves.
9
SL01554
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
2.3V (VUV) < Vbatt < 2.9 V (VP): A charge current of approximately
the normal charge current (pre-charge) is placed into the
battery pack. This continues until the cell voltage reaches 2.9 V. If
the pre-charge timer, times out prior to the cell reaching 2.9 V, the
pre-charge is terminated. The charger can be restarted by bringing
RESET momentarily high, or by turning-OFF and then ON the input
voltage.
NE57610 OPERATION
1/ th
8
The typical application schematic is given in Figure 17. Because in
a multiple-cell battery pack, the battery charger cannot access the
connection(s) between the cells within a battery pack, the following
discussion is based upon the calculated value of each cell’s voltage
(Vbatt/number of series cells).
Start of charging
2.9 V (VP) < Vbatt < 4.35 V (VOV): The high-rate charge current is
placed into the battery pack until the cell reaches a full-charge
condition by either reaching VOV or VF. If the cell does not reach the
full-charge level within the period of the charge timer, the charge is
terminated.
The start of the charging process is only permitted when all of the
following conditions are met:
• The DC input voltage is greater than VADPH, which indicates there
is sufficient input voltage.
• The battery voltage is less than the overcharged voltage (Vov)
• The reset and ON/OFF pins are both LOW.
• The battery temperature voltage falls within its recommended
Vbatt > 4.35 V (VOV) (fully charged): The charge current is
completely cut off. If the battery pack is allowed to remain on the
charger for an extended period, and if the pack voltage falls to 3.9 V
per cell due to self-discharge, charging begins again at the full rate
of charge until VOV or VF is reached again. This process repeats as
long as the battery is in the charger.
operating range.
The charging behavior depends on the voltage of the battery. If the
initial cell voltage is:
Overriding conditions
If, under any of the above conditions, the following conditions are
encountered, the charging process will be immediately terminated.
< 2.0 V (VLV) (overdischarged): A 1 mA charge current is sent
into the battery pack and the undervoltage charge timer is set. If the
battery pack voltage does not reach 2.3 V (or VUV) in this preset
period of time, the pack is assumed to be damaged and the
charging process is terminated. The charger can be restarted by
bringing RESET momentarily high, or by turning-OFF and then ON
the input voltage.
• If the temperature sensing input is lower than VTH or higher than
VTL voltages. (remember, a thermocouple’s voltage goes down
with higher temperatures)
• If the timer associated with the presently active function times out.
A State diagram of the various modes of the charger can be seen in
Figure 18.
BCP51
+Vin
PBYR
240CT
RCS
V+
BATTERY PACK
150 Ω
18
RED
VCC
GRN
15
17
CS
DRV
BAT1
BAT2
22
RED
TP1
GRN
TP2
21
10 µF
NE57610
23
OSC1
VREF
OSC2
TMP
13
14
3
4
CELL 2
TP1
TP2
5
CDLL 1
ROSC
24
12
THERM
ON/OFF RESET GND PGND
CT
2
1
6
7
–Vin
V–
SL01863
Figure 17. Typical application circuit (2-cell).
2002 Nov 05
10
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
1 mA
CHARGE
RATE
1 mA CHARGE
TIMER TIME-OUT
PACK VOLTAGE
> VUV
PREPARATORY
CHARGE
PACK
VOLTAGE
< VUV
PACK
VOLTAGE
> VUV
PACK
VOLTAGE
> VP
CHARGE
AT NORMAL
RATE
START
CHARGE
PREP
TIMER
TIME-OUT
PACK VOLTAGE
> VUV, < VOV
VOV HYSTERESIS
Vpack < VOV – VOV(hys)
Vpack > VOV
TERMINATE
CHARGE
Vpack > VOV
SL01860
Figure 18. State diagram of charging process.
Charge-mode indicators
Programming the total charge timer
Determining which state the battery charger is operating is easily
done by viewing the red and green LEDs which should be wired
between pins 22 and 21, respectively, and the input voltage source.
Each LED should have a 150 Ω resistor in series. Table 1 shows the
states of these LEDs and the two test pins (TP1 (pin3) and TP2
(pin4)).
To set the total charge time, place a timing capacitor (CT) between
pin 24 and the ground pins (pins 6 and 7) and a resistor (ROSC)
between pins 23 and 24. The typical Li-ion cell requires 3 hours to
totally recharge from VUV and VOV, so a charge period of greater
than or equal to 3 hours should be allowed. The total charge time
can be set by referring to Figure 19.
Table 1. Charge mode indicators versus charger activity
OSCILLATOR CAPACITOR
200 k
Pin 22
(Red)
Pin 21
(Green)
Pin 3
TP1
Pin 4
TP2
Reconditioning
charge
Blink
OFF
Hi Low
Low
Preparatory
charge
ON
OFF
Hi Low
Low
Normal charge
ON
OFF
Hi Low
Low
Charge done
OFF
Blink
Low
Charge timer
time-out
Blink
OFF
Low
Low
Fault: VOV, VLV
VLV, VIN(min)
OFF
OFF
Low
Low
OSCILLATOR RESISTOR (Ω )
Condition
Hi Low
0.0047 µF
0.01 µF
100 k
0.022 µF
1
2
3
4
5
CHARGE TIME-OUT (HOURS)
5
6
10
15
20
PRECHARGE TIME-OUT (MINUTES)
5
10
15
1 mA TIME-OUT (SECONDS)
20
SL01864
Figure 19. Total charge time versus CT.
2002 Nov 05
11
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
Setting the charge currents and detection
thresholds
CS
BAT1
A=4
The NE57610 has a preset charge termination voltage which is set
during manufacture. The remaining charge currents and detection
thresholds involved during the charging process must be set with
the value of certain resistors and optionally by using the ADJ pins 1
through 4. Setting the thresholds is very important because the
charge termination voltage alone is a state of overcharge for the
lithium cell. If ignored, this can be very hazardous.
VREF
Figure 16 shows some of the terms and charging periods.
R1
ADJ1
OR
ADJ2
Setting the high-rate charge current
The second most important parameter is the adjustable high-rate
charge current. First, determine the highest rate of charge of the
chosen lithium cell from the cell’s datasheet. This rate must not be
exceeded because it would cause excessive heating of the cell
during charging. The maximum charge rate will typically charge a
completely discharged cell in under 3 hours.
HYST
R2
CS
BAT1
A=4
Then, calculate the required value of the current sensing resistor
(RCS). This resistor also controls the rate of the other charge
currents (pre-charge and reconditioning charge). All of these charge
rates can be individually lowered by adding adjustment resistors to
the ADJ1–ADJ4 pins. (See ‘Using the ADJ1–ADJ4 pins’.)
COMP
The high-rate charging current is set by the value of RCS and can be
found by the following equation:
R CS +
0.22V
I chg(high*rate)
VREF
R1
Eqn. (1)
ADJ3
OR
ADJ4
The typical value is around 0.3 Ω, which yields a 660 mA for the
high-rate charge. If a current-limited wall transformer is used, this
current may never be reached.
R2
SL01861
The pre-charge rate is set internally at around 1/8th of the high-rate
of charge. This value may also be lowered by adding a resistor to
VSS from the ADJ3 pin. (See ‘Using the ADJ1- ADJ4 pins’.)
Figure 20. Equivalent circuits for ADJ1–ADJ4.
Table 2. ADJ1–ADJ4 internal resistor divider values
Using the ADJ1–ADJ5 pins
Using the ADJ1–ADJ5 pins is optional. The NE57610 will operate as
specified when the pins are left unconnected.
Pin
name
Pin
Pin
voltage
R1
R2
VOS
The ADJ pins are the center-node voltage of an internal resistor
divider which are preset to the values given in the datasheet. Each
of the parameters may be modified by placing an external resistor to
ground or to Vref. The ADJx voltages are directly related to the
voltage measured across the current sense resistor (RCS) between
CS and the BAT1 & BAT2 pins.
ADJ1
8
1.16 V
5.8 kΩ
105 kΩ
–
ADJ2
9
62 mV
128 kΩ
10.5 kΩ
4.5 mV
ADJ3
10
120 mV
146 kΩ
16 Ω
3.1 mV
ADJ4
11
0.89 V
20 kΩ
58 Ω
–
The equation relating the values of ADJ pins to the voltage between
the CS pin and the BAT1 and BAT2 pins is given by Equation (2):
The ADJ5 pin will increase the full-charge voltage (VOV) by 15 mV if
the pin is connected to ground.
V ADJx + 4(I x (R CS) ) V OS)
ADJ1 through ADJ4 are ground-referenced voltages which can
lower the preset values of the overcurrent cutoff (ADJ1), the
top-off-charge minimum current threshold (ADJ2), the pre-charge
charge current (ADJ3), and the high-rate charging current (ADJ4).
The VOS term is the input offset voltage of the current-sense
amplifier, which varies with the battery voltage. The offset term is
only significant while low levels of current are being sensed, such as
during the pre-charge period and the end-of-charge current
threshold. During the high-rate charge and overcurrent conditions
the contribution of the input offset voltage is negligible.
The overcurrent cutoff current is normally not used because there is
usually a current-limited wall transformer providing the input power
for the charger, and the transformer’s current limit is usually within
the safe range of the cell(s). This cutoff voltage can be lowered by
lowering the ADJ1 voltage.
The equivalent circuits for the ADJ1–ADJ4 circuits are shown in
Figure 20.
2002 Nov 05
Eqn. (2)
12
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
Adjusting current levels with ADJ1–ADJ4
First, calculate the desired voltage of the ADJ pin in question. This is
done by executing Equation (2), and using the value of the input
offset voltage (VOS) if applicable. It becomes a matter of solving a
resistor divider problem with a parallel resistor on the lower branch.
The equation becomes (referring to the resistor designators in
Figure 16 and the values from Table 2):
ǒ V ADJx(R1R2) Ǔ
ǒ V REF R2 * V ADJx (R1 ) R2) Ǔ
D2PAK (SOT404)
MAXIMUM POWER (WATTS)
R ext +
2
Eqn. (3)
where Rext is the external resistor from the respective ADJ pin to
VSS.
DPAK (SOT428)
1
SOT223 (SC-73)
DESIGNING THE POWER SECTION OF THE
BATTERY CHARGER
SOT23 (SST3)
There are several factors that are important to the design of a
reliable Li-ion battery charger system. These major factors are:
25
• The input voltage must not fall below the cell voltage plus the
This chart gives the package to use the minimum recommended pad
size is used under the power part. Making the pad size larger can
increase the power handling capacity of the part without sacrificing
its reliability. Table 3 shows how to dissipate more power in a
smaller package.
of the components contained within the charging circuit.
• The power rating and the thermal design of the linear pass
transistor must be able to withstand the maximum experienced
headroom voltage at the high-rate charge current. The worst case
condition can be calculated by assuming the cell is at its lowest
typical voltage (2.9 V) and the input voltage is at its highest point
in its range (typically the DC voltage created at the highest AC
input) times the high-rate charge current. The power can then be
calculated by Equation (4):
Table 3.
Eqn. (4)
The criteria for the selection of the PNP power transistor should be:
Pad size
Rth(j–a)
Power increase
2X
0.88 °C/W
14%
3X
0.80 °C/W
25%
4X
0.74 °C/W
35%
5X
0.70 °C/W
43%
NOTES:
1. Going beyond five times the minimum recommended footprint
yields diminishing improvements to the thermal performance.
2. Given for an F4 fiberglass PCB with 2 oz. copper
VCEO > 1.5 Vin(max)
IC > 1.5 Icharge
hFE > 50 @ 1 Amp
PD > PD(max)
The choice of power transistor package should be done with the
highest possible power dissipation and at the highest expected
ambient temperature. Choose a surface mount package by referring
to Figure 21 and drawing two intersecting lines from the appropriate
points on the X and Y axis.
2002 Nov 05
100
Figure 21. Maximum power dissipation versus ambient
temperature versus package.
• The maximum input voltage must not exceed the voltage ratings
ǒIchargeǓ
75
SL01865
headroom voltage of the charger circuit. The headroom voltage for
the charger circuit is 1.6 V which would make the minimum input
voltage about 5.6 V. This requirement also includes the troughs of
any ripple voltage riding atop the DC input voltage from a poorly
filtered wall transformer.
P D(max) + ǒV in(max) * V cell(min)Ǔ
50
MAXIMUM AMBIENT TEMPERATURE (°C)
13
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
dealt with by examining how the circuit powers-up and making sure
there are no power-up sequences that can lead to a component
failure or hazardous operating conditions.
DESIGN-RELATED SAFETY ISSUES
In designing charging circuits for lithium-ion and polymer cells, the
designer should provide for user mishandling, common
environmental hazards and for random component failures.
A common adverse operating condition at the input is
lightning-caused transients. A simple 500 mW zener diode across
the input terminals handles positive and negative transients caused
by lightning. The zener will fail short-circuited, if the energy exceeds
its surge energy ratings. To help protect the protection zener, place a
small inductor or low value resistor in series from the input source.
This will lower the peak voltage and energy entering the zener diode
and will distribute the energy over a longer period.
Some of the user-related issues are: plugging the battery pack into
the charger backwards, inserting of the battery into the live charger,
and plugging the charger into an unexpected input voltage source.
A series diode is typically used for reversed battery protection. This
prevents reverse currents from flowing into the device, protecting
the functionality of the charger. Protecting against live insertion of
the battery and the wrong type of input power to the charger must be
PACKING METHOD
The NE57610 is packed in reels, as shown in Figure 22.
GUARD
BAND
TAPE
REEL
ASSEMBLY
TAPE DETAIL
COVER TAPE
CARRIER TAPE
BARCODE
LABEL
BOX
SL01305
Figure 22. Tape and reel packing method
2002 Nov 05
14
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
TSOP-24: plastic thin shrink small outline package; 24 leads; body width 4.4 mm
0.2
0.1
2002 Nov 05
0.25
0.1
6.8
6.37
0.5
15
6.7
6.1
0.8
0.2
10°
0°
Philips Semiconductors
Product data
Li-ion battery charger control
with adjustable thresholds
NE57610
REVISION HISTORY
Rev
Date
Description
_1
20021105
Product data; initial version.
Engineering Change Notice 853–2351 28505 (date: 20020620).
Data sheet status
Level
Data sheet status [1]
Product
status [2] [3]
Definitions
I
Objective data
Development
This data sheet contains data from the objective specification for product development.
Philips Semiconductors reserves the right to change the specification in any manner without notice.
II
Preliminary data
Qualification
This data sheet contains data from the preliminary specification. Supplementary data will be published
at a later date. Philips Semiconductors reserves the right to change the specification without notice, in
order to improve the design and supply the best possible product.
III
Product data
Production
This data sheet contains data from the product specification. Philips Semiconductors reserves the
right to make changes at any time in order to improve the design, manufacturing and supply. Relevant
changes will be communicated via a Customer Product/Process Change Notification (CPCN).
[1] Please consult the most recently issued data sheet before initiating or completing a design.
[2] The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at URL
http://www.semiconductors.philips.com.
[3] For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.
Definitions
Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see
the relevant data sheet or data handbook.
Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting
values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given
in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability.
Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips Semiconductors make no
representation or warranty that such applications will be suitable for the specified use without further testing or modification.
Disclaimers
Life support — These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be
expected to result in personal injury. Philips Semiconductors customers using or selling these products for use in such applications do so at their own risk and agree
to fully indemnify Philips Semiconductors for any damages resulting from such application.
Right to make changes — Philips Semiconductors reserves the right to make changes in the products—including circuits, standard cells, and/or software—described
or contained herein in order to improve design and/or performance. When the product is in full production (status ‘Production’), relevant changes will be communicated
via a Customer Product/Process Change Notification (CPCN). Philips Semiconductors assumes no responsibility or liability for the use of any of these products, conveys
no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranties that these products are free from patent,
copyright, or mask work right infringement, unless otherwise specified.
 Koninklijke Philips Electronics N.V. 2002
All rights reserved. Printed in U.S.A.
Contact information
For additional information please visit
http://www.semiconductors.philips.com.
Fax: +31 40 27 24825
Date of release: 11-02
For sales offices addresses send e-mail to:
[email protected].
2002 Nov 05
Document order number:
16
9397 750 10465