Philips Semiconductors
Product data
One-cell Lithium-ion battery protection with
over/undercharge and overcurrent protection
SA57608
GENERAL DESCRIPTION
The SA57608 is a single-cell Li-ion protection IC, and is an improved
version of the NE57600, with different pinout. Its over and under
voltage accuracies are trimmed to within
±
25 mV (5%) over the
entire battery pack operating temperature range. The SA57608 is
available in various over and undervoltage limits.
There is a discharge overcurrent protection circuit which can protect
the battery pack against an accidental short-circuit. The overcharge
trip point has a time delay which can be programmed externally. It is
packaged in a space-saving SOT-26A and requires two external
N-channel MOSFETs and a minimum of passive parts.
FEATURES
•
Trimmed overvoltage trip point to within
±25
mV
•
Programmable overvoltage trip time delay
•
Trimmed undervoltage trip point to within
±25
mV
•
Very Low undervoltage quiescent sleep current 0.05 mA
•
Discharge overcurrent cutoff
•
Low operating current (10
mA)
•
Very small SOT-26A package
SIMPLIFIED SYSTEM DIAGRAM
APPLICATIONS
•
Cellular phones
•
Personal digital assistants
•
Palmtop computers
V+
100
Ω
V
CC
5
0.01
µF
0.1
µF
Li-ION CELL
GND
6
DF
1
CF
3
C
DLY
4
SA57608
2
VM
0.1
µF
1 kΩ
V–
DISCHARGE
FET
CHARGE
FET
SL01568
Figure 1. Simplified system diagram.
2001 Oct 03
2
853-2298 27198
Philips Semiconductors
Product data
One-cell Lithium-ion battery protection with
over/undercharge and overcurrent protection
SA57608
ORDERING INFORMATION
PACKAGE
TYPE NUMBER
SA57608XD
NAME
SOT-26A
DESCRIPTION
small outline plastic surface mount, 6-pin
TEMPERATURE
RANGE
–20 to +85
°C
NOTE:
The device has six protection parameter options, indicated by the
X
on the order code, and defined in the following table.
TYPICAL PROTECTION PARAMETERS
Part Number
SA57608Y
SA57608B
SA57608C
SA57608D
SA57608E
SA57608G
Overcharge
detection voltage (V)
4.350
±0.050
4.280
±0.025
4.295
±0.025
4.350
±0.050
4.275
±0.025
4.280
±0.025
Overcharge detection
hysteresis voltage (mV)
180
180
150
180
200
200
Over-discharge
detection voltage (V)
2.30
±0.070
2.30
±0.058
2.30
±0.058
2.30
±0.070
2.30
±0.058
2.30
±0.058
Overcurrent
detection voltage (mV)
150
±30
75
±30
200
±30
200
±30
100
±30
100
±30
Part number marking
Each device is marked with a four letter code. The first three letters
designate the product. The fourth letter, represented by ‘x’, is a date
tracking code.
Part number
SA57608YD
SA57608BD
SA57608CD
SA57608DD
SA57608ED
SA57608GD
Marking
AGXx
AGYx
AGZx
AHAx
AHBx
AHDx
PIN CONFIGURATION
DF
VM
CF
1
2
3
6
5
4
GND
V
CC
C
DLY
SL01569
Figure 2. Pin configuration.
PIN DESCRIPTION
PIN
1
2
3
4
5
6
SYMBOL
DF
VM
CF
C
DLY
V
CC
GND
DESCRIPTION
Discharge detection pin. This drives the gate of the discharge N-ch FET
Monitor pin. Detects overcurrent and the presence of a charger.
Charge FET pin. This drives the gate of the charge control N-ch FET
Charge Time Delay pin. The capacitor connected to this pin sets the delay
Positive supply voltage input pin. Connect to positive terminal of the cell.
Ground pin. Connect to negative terminal of the cell
MAXIMUM RATINGS
SYMBOL
V
IN
V
CF(max)
V
VM(max)
T
opr
T
stg
P
D
Input voltage
CF pin voltage
VM pin voltage
Operating ambient temperature range
Storage temperature
Power dissipation
PARAMETER
MIN.
–0.3
V
CC
– 28
V
CC
– 28
–40
–40
–
MAX.
+12
V
CC
+ 0.3
V
CC
+ 0.3
+85
+125
150
UNIT
V
V
V
°C
°C
mW
2001 Oct 03
3
Philips Semiconductors
Product data
One-cell Lithium-ion battery protection with
over/undercharge and overcurrent protection
SA57608
ELECTRICAL CHARACTERISTICS
Characteristics measured with T
amb
= 25
°C,
unless otherwise specified.
SYMBOL
V
DD1
I
DD
I
SLP
V
DD(min)
PARAMETER
Operating input voltage
Supply current
Sleep current
Minimum operating voltage for 0 V
charging
CONDITIONS
V
CC
– GND; Voltage defined as V
DD
to VM
V
CC
= 3.9 V; VM = 0 V
V
CC
= 2.0 V
V
CC
– GND
SA57608Y
SA57608B
V
O ( )
OV1(th)
Over-charge
Over charge voltage threshold
T
amb
= 0
°C ∼
50
°C;
V
BATT
: L
→
H
SA57608C
SA57608D
SA57608E
SA57608G
SA57608Y
SA57608B
V
O (
OV1(hyst)
)
Over-charge
Over charge hysteresis
V
CC
: H
→
L
SA57608C
SA57608D
SA57608E
SA57608G
SA57608Y
SA57608B
V
UV(th
)
(
Over-discharge
Over discharge threshold voltage
V
CC
: H
→
L
SA57608C
SA57608D
SA57608E
SA57608G
SA57608Y
SA57608B
V
OC (
)
OC1(th
Overcurrent threshold
V
VM
: L
→
H
SA57608C
SA57608D
SA57608E
SA57608G
V
OV(rel)
t
OV(DLY)
t
OV
t
OC(DLY
)
V
OC2
t
DLY(SC)
R
SC
V
CFET(off)
V
CFET(on)
V
DFET(off)
V
DFET(on)
Release voltage for over-discharge
Over-charge delay time
Over-discharge delay time
Over-current delay time
Short protection voltage
Short detect delay time
Reset resistance for excess current
protection
Nch ON voltage of CFET
Pch ON voltage of CFET
Nch ON voltage of DFET
Pch ON voltage of DFET
C
TD
= 0.01
µF;
V
CC
= 4.0 V to 4.4 V
V
CC
= 3.6 V to 2.2 V
VM : 0 V
→
0.5 V
V
CC
= 3.0 V
V
CC
= 3.0 V
V
CC
= 3.6 V; VM = 1.0 V
I
OL
= 50 mA; V
CC
= 4.4 V
I
OH
= 50 mA; V
CC
= 3.9 V
I
OL
= 50 mA; V
CC
= 2.2 V
I
OH
= 50 mA; V
CC
= 3.9 V
MIN.
1.5
–
–
–
4.30
4.255
4.27
4.30
4.25
4.255
–
–
–
–
–
–
2.23
2.242
2.242
2.23
2.242
2.242
120
45
170
170
70
70
4.12
61
5
9
V
CC
–1.2
–
50
–
3.4
–
3.4
TYP.
–
3.0
0.3
–
4.35
4.280
4.295
4.350
4.275
4.280
180
180
150
180
200
200
2.30
2.30
2.30
2.30
2.30
2.30
150
75
200
200
100
100
4.17
77
8
13
V
CC
–0.9
5
100
0.35
3.7
0.2
3.7
MAX.
10
8.0
0.6
1.2
4.40
4.305
4.32
4.40
4.3
4.305
–
–
–
–
–
–
2.37
2.358
2.358
2.37
2.358
2.358
180
105
230
230
130
130
4.22
93
11
17
V
CC
–0.6
50
150
0.5
–
0.5
–
UNIT
V
mA
mA
V
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
V
ms
ms
ms
V
ms
kW
V
V
V
V
2001 Oct 03
4
Philips Semiconductors
Product data
One-cell Lithium-ion battery protection with
over/undercharge and overcurrent protection
SA57608
TECHNICAL DISCUSSION
Lithium cell safety
Lithium-ion and lithium-polymer cells have a higher energy density
than that of nickel-cadmium or nickel metal hydride cells and have a
much lighter weight. This makes the lithium cells attractive for use in
portable products. However, lithium cells require a protection circuit
within the battery pack because certain operating conditions can be
hazardous to the battery or the operator, if allowed to continue.
Lithium cells have a porous carbon or graphite anode where lithium
ions can lodge themselves in the pores. The lithium ions are
separated, which avoids the hazards of metallic lithium.
If the lithium cell is allowed to become overcharged, metallic lithium
plates out onto the surface of the anode and volatile gas is
generated within the cell. This creates a
rapid-disassembly hazard
(the battery ruptures). If the cell is allowed to over-discharge (V
cell
less than approximately 2.3 V), then the copper metal from the
cathode goes into the electrolyte solution. This shortens the cycle
life of the cell, but presents no safety hazard. If the cell experiences
excessive charge or discharge currents, as happens if the wrong
charger is used, or if the terminals short circuit, the internal series
resistance of the cell creates heating and generates the volatile gas
which could rupture the battery.
The protection circuit continuously monitors the cell voltage for an
overcharged condition
or an
overdischarged condition.
It also
continuously monitors the output for an
overcurrent condition.
If
any of these conditions are encountered, the protection circuit opens
a series MOSFET switch to terminate the abnormal condition. The
lithium cell protection circuit is placed within the battery pack very
close to the cell.
Charging control versus battery protection
The battery pack industry does not recommend using the pack’s
internal protection circuit to end the charging process. The external
battery charger should have a charge termination circuit in it, such
as that provided by the SA57611. This provides two levels of
overcharge protection, with the primary protection of the external
charge control circuit and the backup protection from the battery
pack’s protection circuit. The charge termination circuit will be set to
stop charging at a level around 50 mV less than the overvoltage
threshold voltage of the battery pack’s own protection circuit.
Lithium cell operating characteristics
The internal resistance of lithium cells is in the 100 mΩ range,
compared to the 5–20 mΩ of the nickel-based batteries. This makes
the Lithium-ion and polymer cells better for lower battery current
applications (less than 1 ampere) as found in cellular and wireless
telephones, palmtop and laptop computers, etc.
The average operating voltage of a lithium-ion or polymer cell is
3.6 V as compared to the 1.2 V of NiCd and NiMH cells. The typical
discharge curve for Lithium cell is shown in Figure 3.
OPEN-CIRCUIT CELL VOLTAGE (V)
4.0
V
OV
3.0
V
UV
2.0
50
NORMALIZED CELL CAPACITY (%)
100
SL01553
Figure 3. Lithium discharge curve.
2001 Oct 03
5
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