AD ADP2291ACPZ-R7 Compact, 1.5 a linear charger for single-cell li battery Datasheet

Compact, 1.5 A Linear Charger
for Single-Cell Li+ Battery
ADP2291
FEATURES
GENERAL DESCRIPTION
Simple, safe linear charger for single cell lithium battery
4.5 V to 12 V input voltage range
Adjustable charging current up to 1.5 A
Low cost PNP external pass element
Automatic reverse isolation with no external blocking diode
Output overshoot protection
Deep discharge precharge mode
Thermal shutdown
Automatic recharge
Programmable termination timer
LED charging status indicator
4.2 V output voltage with ±1% accuracy over line and
temperature
1 µA shutdown supply current
Small, 8-pin MSOP and 3 × 3 mm LFCSP packages
The ADP2291 is a constant-current/constant-voltage linear
charger for a single cell lithium ion battery, requiring just a few
components to provide a simple and safe charging system that
operates from a wide 4.5 V to 12 V input voltage range. It
features an internally controlled, multistep charging cycle that
improves battery life.
An external, low cost, PNP provides the charging current to the
battery and an external resistor sets the maximum charge
current. A small external capacitor programs the maximum
charge time. The controller includes an LED driver to indicate
the battery charging status.
Safety features include charging stop mode for battery faults,
output overshoot protection, and thermal shutdown. The
ADP2291 also features automatic reverse isolation, which does
not require an additional blocking diode.
APPLICATIONS
The multistep charge cycle optimizes the battery charging time
in a safe manner. It features a trickle charge mode for a deeply
discharged cell and a fast charging mode with a maximum
current of 1.5 A. The ADP2291 controls the end of charge with
a 4.2 V output voltage that is 1% accurate over line and temperature. It automatically recharges the battery if the cell voltage
drops. When the input supply is removed, the part enters a low
current state and reduces the current drawn from the battery to
below 1 µA.
Wireless handsets
Smart handhelds and PDAs
Digital cameras
Single cell lithium ion-powered systems
Cradle chargers
The ADP2291 is available in both a small, 8-pin MSOP package
and a 3 × 3 mm LFCSP package that is ideally suited for small,
portable applications.
TYPICAL OPERATING CIRCUIT
RS
INPUT
4.6V–12V
Q1
+
COUT
CIN
CS
DRV
IN
BAT
ADP2291
CHG
GND
ADJ
CTIMER
SHUTDOWN
04873-0-001
TIMER
Figure 1. Basic Circuit Configuration
Rev. 0
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Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
ADP2291
TABLE OF CONTENTS
Specifications..................................................................................... 3
Thermal Shutdown .................................................................... 11
Absolute Maximum Ratings............................................................ 5
Application Information................................................................ 12
ESD Caution.................................................................................. 5
Setting the Maximum Charge Current.................................... 12
Pin Configuration And Functional Descriptions......................... 6
Setting the Maximum Charge Time ........................................ 12
Typical Performance Characteristics ............................................. 7
External Capacitors.................................................................... 12
Theory of Operation ...................................................................... 10
Reverse Input Protection........................................................... 12
Precharge Mode.......................................................................... 10
External Pass Transistor ............................................................ 13
End-of-Charge Mode................................................................. 10
Typical Application Circuit ....................................................... 14
Shutdown Mode.......................................................................... 10
EOC Terminates Charging........................................................ 14
Charge Restart............................................................................. 10
Selectable Charge Current......................................................... 14
Programmable Timer................................................................. 10
Thermal Protection.................................................................... 14
Charge Status Indicator ............................................................. 10
Printed Circuit Board Layout Considerations........................ 16
Automatic Reverse Isolation ..................................................... 10
LFSCP Layout Considerations.................................................. 16
Overshoot Protection................................................................. 10
Outline Dimensions ....................................................................... 18
Power Supply Checks ................................................................. 10
Ordering Guide .......................................................................... 18
REVISION HISTORY
10/04—Initial Version: Revision 0
Rev. 0 | Page 2 of 20
ADP2291
SPECIFICATIONS
VIN = 5.5 V, VBAT = 4.2 V, RADJ open, TA = –40°C to +85°C, typical values are at 25°C unless otherwise noted.1
Table 1. Electrical Characteristics
Parameter
Power Supply, IN
Input Voltage
Current Draw
Battery Voltage, BAT
Voltage Accuracy, End-of-charge (VBAT, EOC)
Load Regulation, No Battery
Current Draw
Current Draw
Reverse Leakage Current
Fast Charge Mode
Sense Voltage Setpoint (VRS)
Sense Voltage Setpoint (VRS)
Current Regulation Adjustment
Precharge Mode
Sense Voltage Setpoint (VRS)
Sense Voltage Setpoint (VRS)
BAT Precharge Threshold
Hysteresis
Shutdown Mode
ADJ Shutdown Threshold
Hysteresis
Pullup current from ADJ
Power-Down Mode
VIN Powerdown Threshold
Hysteresis
VIN_Good Comparator
Threshold (VIN > VBAT)
Hysteresis
EOC Comparator
Current Threshold
Current Threshold
Hysteresis
Restart Comparator
BAT Restart Threshold
Conditions
Min
Typ
Max
Unit
6
1.4
12
9
1.8
V
mA
mA
4.2
4.242
V
45
mV
µA
1
µA
4.5
Fast charge/precharge/end-of-charge modes
Timeout/shutdown/battery fault
TA = 0°C to +50°C
VIN = 4.5 V to 12 V
VIN – VCS = VRS/10
VIN – VCS = 0 to VRS
Timeout mode
VIN = 4.5 V to 12 V
Battery fault/shutdown mode
VIN = 4.5 V to 12 V
Power-down mode
VIN = float, VBAT = 4.2 V
4.158
VIN – VCS, RADJ = open
VIN = 4.5 V to 12 V
VBAT = 3.6 V
VIN – VCS, RADJ = 100 kΩ
VIN = 4.5 V to 12 V
VBAT = 3.6 V
per V of (3 V – VADJ)
140
150
160
mV
40
50
60
mV
VIN – VCS, RADJ = open
VIN = 4.5 V to 12 V
VBAT = 2 V
VIN – VCS, RADJ = 100 kΩ
VIN = 4.5 V to 12 V
VBAT = 2 V
VBAT rising
10
15
20
mV
5
10
15
mV
2.85
V
mV
0.45
V
mV
µA
4
V
mV
–80
0.1
0.1
µA
67
2.65
mV/V
70
VADJ falling, VIN = 4.5 V
0.30
40
40
VADJ = 0
VIN rising
3.6
220
VIN rising
125
170
110
220
mV
mV
VIN – VCS falling, RADJ = open, relative to VRS
VIN – VCS falling, RADJ = 100 kΩ, relative to VRS
7
6
10
10
12
13
16
%
%
mV
VIN > 4.5 V, VBAT falling, relative to VBAT, EOC
–170
Rev. 0 | Page 3 of 20
mV
ADP2291
Parameter
Battery Charge Timer
Charge/Discharge TIMER Current
Low Threshold
High Threshold
High-Low Threshold Delta2
Overshoot Protection
BAT Threshold
Current Sink
CHG Output
Output Voltage Low
Output Leakage Current
Base Drive Capability
Max Base Drive Current
Thermal Shutdown
Shutdown Threshold
Hysteresis
1
2
Conditions
Min
Typ
Max
Unit
21.0
24.0
1.2
2.0
27.0
µA
V
V
mV
750
4.7
850
<2 ms duration
5
1.5
Current = 20 mA
VCHG = 5 V
0.1
40
TA rising
V
A
0.45
1
V
µA
mA
135
35
All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC). Typical values are at TA = 25° C.
Guaranteed by design, not tested in production.
Rev. 0 | Page 4 of 20
5.3
°C
°C
ADP2291
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
IN, DRV1, CS, CHG, to GND
BAT, ADJ, TIMER to GND
Operating Ambient Temperature
Operating Junction Temperature
θJA, 2-layer MSOP-8
θJA, 4-layer MSOP-8
θJA, 2-layer LFCSP-8
θJA, 4-layer LFCSP-8
Storage Temperature
Lead Temperature Range Soldering
(10 sec)
Rating
−0.3 V to +13.5 V
−0.3 V to (VIN + 0.3 V)
−40°C to +85°C
−40°C to +125°C
220ºC/W
158ºC/W
62ºC/W
48ºC/W
−65°C to +150°C
300°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other condition s above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability. Absolute maximum ratings apply individually
only, not in combination. Unless otherwise specified all other
voltages referenced to GND.
1
Pulling current from the DRV pin by driving it below ground, while VIN is
applied, may cause permanent damage to the device.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. 0 | Page 5 of 20
ADP2291
PIN CONFIGURATION AND FUNCTIONAL DESCRIPTIONS
CS 4
TOP VIEW
(Not to Scale)
8
CHG
7
TIMER
6
IN
5
ADJ
DRV 1
GND 2
BAT 3
CS 4
PIN 1
INDICATOR
ADP2291
TOP VIEW
(Not to Scale)
8 CHG
7 TIMER
6 IN
5 ADJ
Figure 2. 8-Lead MSOP
Figure 3. 8-Lead LFCSP
Table 3. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
Mnemonic
DRV
GND
BAT
CS
ADJ
IN
TIMER
CHG
Description
Base Driver Output. Controls the base of an external PNP pass transistor.
Ground.
Battery Voltage Sense Input.
Current Sense Resistor Negative Input.
Charging Current Adjust and Charger Shutdown Input.
Power Input and Current-Sense Resistor Positive Input.
Timer Programming Input/Disable.
LED Charge-Status Indicator. This is an open-collector output.
Rev. 0 | Page 6 of 20
04873-0-003
BAT 3
ADP2291
04873-0-002
DRV 1
GND 2
ADP2291
TYPICAL PERFORMANCE CHARACTERISTICS
4.21
800.0
700.0
4.205
600.0
ICHG (mA)
VBAT (V)
500.0
4.20
400.0
300.0
04873-0-004
4.19
4
6
8
VIN (V)
10
04873-0-007
200.0
4.195
100.0
0.0
2.50
12
Figure 4. Battery Voltage vs. Input Voltage
3.00
3.50
IBAT (V)
4.00
4.50
Figure 7. Charge Current vs. Battery Voltage,
RS = 200 mΩ, VADJ = 3 V
4.21
250
200
IREVERSE (nA)
VBAT (V)
4.205
4.20
150
100
4.195
–25
0
25
50
TEMPERATURE (°C)
75
100
0
–50
125
Figure 5. Battery Voltage vs. Temperature
04873-0-008
4.19
–50
04873-0-005
50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
Figure 8. Battery Reverse Current vs. Temperature
VIN = float, VBAT = 4.2 V
4.10
4.22
4.09
VRESTART (V)
4.20
4.08
4.07
4.19
4.18
0
200
400
ICHG (mA)
600
4.05
–40
800
Figure 6. Battery Voltage vs. Charge Current,
RS = 200 mΩ, VADJ = 3 V
04873-0-009
4.06
04873-0-006
VBAT (V)
4.21
–20
0
20
40
60
TEMPERATURE (°C)
Figure 9. Restart Threshold
Rev. 0 | Page 7 of 20
80
100
16.0
153
15.8
152
15.6
151
VRS (mV)
15.4
150
04873-0-010
15.0
4
6
8
VIN (V)
10
04873-0-013
149
15.2
148
4
12
15.5
152
15.4
151
15.3
15.2
10
12
150
149
04873-0-011
15.1
–50
8
VIN (V)
Figure 13. Fast Charge VRS vs. Input Voltage
VRS (mV)
VRS (mV)
Figure 10. Precharge VRS vs. Input Voltage
6
–25
0
25
50
75
TEMPERATURE (°C)
100
148
–50
125
Figure 11. Precharge VRS vs. Temperature
04873-0-014
VRS (mV)
ADP2291
–25
0
25
50
75
TEMPERATURE (°C)
100
125
Figure 14. Fast Charge VRS vs. Temperature
160
16
140
14
VRS (mV)
12
100
80
10
1k
RADJ (kΩ)
40
100
10k
Figure 12. Precharge VRS vs. RADJ
04873-0-015
8
100
60
04873-0-012
VRS (mV)
120
1k
RADJ (kΩ)
Figure 15. Fast Charge VRS vs. RADJ
Rev. 0 | Page 8 of 20
10k
ADP2291
135
CH1 = VBAT
4.18V OFFSET
1
BASE DRIVE (mA)
130
125
CH2 = VIN
5V OFFSET
VIN = 5V TO 8V
2
04873-0-016
115
4
6
8
VIN (V)
10
04873-0-018
120
CH1 10.0mV BW CH2 1.00V
12
Figure 16. Base Drive vs. Input Voltage
BW M200µs
CH2
6.18V
Figure 18. Line Transient Response
IBAT = 350 mA
122
120
CH1 = VBAT
4.18V OFFSET
1
116
114
112
110
108
106
104
–40
–20
0
20
40
60
TEMPERATURE (°C)
80
04873-0-019
CH3 = IBAT
200mA/DIV
IBAT = 70mA TO 700mA
04873-0-017
BASE DRIVE (mA)
118
3
CH1 20.0mV BW
CH3 10.0mVΩ
100
M100µs
CH3
Figure 19.Load Transient Response
VIN = 5 V
Figure 17. Base Drive vs. Temperature
VIN = 5 V
Rev. 0 | Page 9 of 20
10.0mV
ADP2291
THEORY OF OPERATION
The ADP2291 is intended to charge a single cell, lithium battery
from a supply voltage or wall adapter providing 4.5 V to 12 V.
The charge controller adjusts the base current of an external
PNP transistor to optimize current and voltage applied to the
battery during charging. A low value resistor placed in series
with the battery charging current provides current measurement for the ADP2291.
CHARGE RESTART
To assure safety and long battery lifetime, the ADP2291 charges
the battery using a simple step-by-step cycle, as shown in the
state diagram of Figure 26. The normal charge cycle begins by
measuring the battery voltage to determine charge level. If the
battery is deeply discharged, then low current precharge is
initiated. Once precharge is complete, normal fast charge at the
maximum current (denoted as IMAX) begins. This maximum
current can be adjusted by varying the sense resistor value or by
varying the voltage at the adjust pin. As the battery approaches
full capacity, the charging current is reduced until the end-ofcharge condition is reached. Batteries that are not deeply
discharged skip the precharge mode and immediately begin fast
charging. Each of these modes and associated fault conditions
are discussed in detail.
PROGRAMMABLE TIMER
PRECHARGE MODE
For deeply-discharged cells, the ADP2291 charges at a reduced
rate when the battery voltage VBAT < 2.8 V. This reduced rate is
IMAX/10 when the ADJ pin voltage is 3 V, and IMAX/5 when the
ADJ pin voltage is 1.5 V. For ADJ pin voltages in between, the
charge current can be interpolated. If the battery voltage does
not increase past 2.8 V before the precharge timer elapses
(typically 30 minutes), a battery fault is assumed and the
ADP2291 shuts down and does not restart until the input
voltage is cycled OFF and then back ON. Note that in this mode
shutdown commands are ignored.
Once charge is complete in end-of-charge or timeout modes,
the ADP2291 continually monitors the cell voltage and charge
current. When the cell voltage falls by 100 mV or the charge
current increases beyond the EOC hysteresis, the ADP2291
initiates another charge cycle to keep the cell fully charged. See
the state diagram in Figure 26.
The on-chip timer, controlled by an external capacitor
CTIMER, determines the timeout intervals of the various
charger modes. For example, a CTIMER value of 0.1 µF results
in a precharge timeout interval of 30 minutes, a fast charge
timeout of 3 hours, and an end-of-charge timeout of 30
minutes. The ratio between precharge and end-of-charge to fast
charge time-out is always 1/6. All these time intervals are
proportional to the CTIMER capacitor value, allowing them to
be adjusted over a wide range. Connecting the TIMER pin to
ground disables the timer.
CHARGE STATUS INDICATOR
The ADP2291 contains a charge status output, CHG, that sinks
current when the ADP2291 is charging the battery. This output
can be used as a visual signal by connecting it to an LED, or it
may be used to generate a logic-level charge status signal by
connecting a resistor between CHG and logic high.
AUTOMATIC REVERSE ISOLATION
When the voltage on the BAT pin is higher than the voltage on
IN, the ADP2291 automatically connects the base of the pass
device to BAT. This removes the necessity of having an external
diode between the pass device and battery, further reducing the
charger’s footprint and component count.
END-OF-CHARGE MODE
OVERSHOOT PROTECTION
Once the voltage loop reduces the charge current to 1/10 of its
nominal value, IMAX (irrespective of the ADJ voltage), the
ADP2291 detects the end-of-charge (EOC) state and the charge
status indicator becomes high-impedance.
In the event of a battery disconnect during charging, a voltage
overshoot condition on BAT could occur. The ADP2291
includes an overshoot protection circuit that activates when
VBAT rises to 5 V and sinks up to 1.5 A to protect the external
components.
Low level charging continues until the timer terminates the
charge (nominally 30 minutes).
POWER SUPPLY CHECKS
SHUTDOWN MODE
When the ADJ input is pulled below 0.4 V, the ADP2291 is put
into shutdown mode. When in this mode, the charger is
disabled, the current drawn from the battery falls to less than
1 µA and the current drawn from IN falls to 0.7 mA.
When the charger is re-enabled, the charger returns to the
START state but quickly sequences through the states until the
proper charge mode is reached.
To assure proper operation, the ADP2291 checks the absolute
voltage level of the input supply and the supply voltage relative
to the battery. When the supply IN is below 3.8 V, the chip is
internally powered down and does not respond to external
control. In this power-down mode, the device draws less than
1 µA from the battery. The VIN good comparator halts operation
if the supply voltage is less than 165 mV above the battery
voltage, insuring that charging only occurs if the supply voltage
is sufficient.
Rev. 0 | Page 10 of 20
ADP2291
included so that the ADP2291 does not return to operation
during thermal shutdown until the on-chip temperature drops
below 100°C.
THERMAL SHUTDOWN
In the event that the ADP2291 junction temperature rises above
135°C, thermal shutdown occurs. Extreme junction temperatures may be the result of excessive current operation and/or
high ambient temperatures. A 35°C temperature hysteresis is
IN
CS
DRV
BAT
3V
5V
GM
GM
GM
ADJ
1.2V
VOLTAGE
REFERENCE
TEMP
SHUTDOWN
RESTART
0.4V
IN
4.1V
VIN_GOOD
BAT
IN
BAT
CONTROL
LOGIC
PRECHARGE
BAT
2.5V
POWER_DOWN
3.8V
C/10
CHG
END_OF_CHARGE
TIMER
TIMER
Figure 20. Functional Block Diagram
Rev. 0 | Page 11 of 20
04873-0-020
IPNP
ADP2291
APPLICATION INFORMATION
SETTING THE MAXIMUM CHARGE CURRENT
SETTING THE MAXIMUM CHARGE TIME
The maximum charge current is set by choosing the proper
current sense resistor, RS, and the voltage on the ADJ input. The
charger nominally regulates its output current at the point
where the voltage across the current sense resistor VIN–VCS
(defined as VRS) is 150 mV. This setpoint voltage can be adjusted
by pulling down on the ADJ input, which is internally attached
through a 100 kΩ pull-up resistor to 3 V. Each volt of pull-down
from 3 V will reduce VRS by 67 mV during fast charge. A
minimum of 50 mV is reached when a 100 kΩ resistor is
attached between ADJ and ground. During slow charge the
voltage across the current sense resistor is 15 mV with no
connection to ADJ and drops to 10 mV with a 100 kΩ resistor
attached to ground. Therefore the maximum charge rate IMAX
can be calculated as
The maximum charge time is intended as a safety mechanism to
prevent the charger from trickle charging the cell indefinitely. It
does not terminate charging under normal charging conditions,
but only when there is a failure to reach end-of-charge. A typical
cell charges at a 1 C rate in about 1.5 hours, depending on the
cell type, temperature, and manufacturer. Generally, a three
hour time limit is sufficient to prevent a normal charge cycle
from being interrupted by the charge timer. It is recommended
that the cell manufacturer be consulted for timing details.
I MAX =
VRS (mV)
R S (mΩ)
(1)
where 50 mV ≤ VRS ≤ 150 mV
After determining suitable values for VRS and RS, the value of
VADJ and RADJ can be calculated as
V ADJ =
VRS (mV) + 50 mV
(2)
⎛ VADJ ⎞
RADJ = 100 kΩ × ⎜
⎟
⎝ 3V − VADJ ⎠
(3)
Examples of resistor combinations are shown in Table 4.
Table 4. Examples of RS and RADJ Selection
IMAX
1.5 A
1A
750 mA
500 mA
750 mA
500 mA
375 mA
250 mA
500 mA
333 mA
250 mA
167 mA
RS
100 mΩ
100 mΩ
100 mΩ
100 mΩ
200 mΩ
200 mΩ
200 mΩ
200 mΩ
300 mΩ
300 mΩ
300 mΩ
300 mΩ
CTIMER = tCHG(minutes) ×
1 µF
1800 minutes
(4)
The precharge and end-of-charge periods are 1/6 the duration
of the fast charge time limit. The charge timers are completely
disabled by connecting the TIMER pin to ground. If the timers
are disabled, the FAULT and TIMEOUT states are never
reached, so the timers should only be disabled if charging is
monitored and controlled externally.
EXTERNAL CAPACITORS
V
66.7 mV
The maximum charge time is set by selecting the value of the
CTIMER capacitor. Calculate the timer capacitance using
VRS
150 mV
100 mV
75 mV
50 mV
150 mV
100 mV
75 mV
50 mV
150 mV
100 mV
75 mV
50 mV
VADJ
3V
2.25 V
1.87 V
1.5 V
3V
2.25 V
1.87 V
1.5 V
3V
2.25 V
1.87 V
1.5 V
RADJ
Open
300 K
167 K
100 K
Open
300 K
167 K
100 K
Open
300 K
167 K
100 K
Use an input supply capacitor (CIN) with a value in the
1 µF to 10 µF range and place it close to the ADP2291. This
should provide adequate input bypassing, but the selected
capacitor should be checked in the actual application circuit.
Check that the input voltage does not droop or overshoot
excessively during the start-up transient.
Use a battery output capacitor (COUT) with a value of at least
10 µF. This capacitance provides compensation when no battery
load is present. In addition, the battery and interconnections
appear inductive at high frequencies and must be accounted for
when the charger is operated with a battery load. Therefore, a
small amount of output capacitance is necessary to compensate
for the inductive nature of the battery and connections. Use a
minimum output capacitance value of 1 µF for applications
where the battery cannot be removed.
REVERSE INPUT PROTECTION
The diode, D1, shown in Figure 22 through Figure 25 is
optional. It is only required if the input adapter voltage can
be applied with a reverse polarity.
If the adapter voltage is high enough, a Schottky diode is recommended to minimize the voltage difference from the adapter to
the charger input and the power dissipation. Choose a diode
with a continuous current rating high enough to handle battery
charging current at the maximum ambient temperature. Use a
diode whose voltage rating is greater than the maximum
adapter voltage.
Rev. 0 | Page 12 of 20
ADP2291
In cases where the voltage drop across the protection device
must be kept low, a P MOSFET is recommended. Connect the
MOSFET as shown in Figure 21.
The power handling capabilities of the PNP pass transistor is
another important parameter. The maximum power dissipation
of the pass transistor is estimated using
RS
INPUT
4.6V–12V
PDISS (W) = IMAX × (VADAPTER(MAX) − VPROTECT − VRS − VBAT) (7)
CIN
CS
DRV
where VRS = 150 mV at VADJ = 3.0 V
= 50 mV at VADJ = 1.5 V
VBAT = 2.8 V, the lowest cell voltage where fast charge can occur
IN
04873-0-021
ADP2291
CHG
Figure 21. Reverse Input Protection
EXTERNAL PASS TRANSISTOR
Choose the external PNP pass transistor based on the given
operating conditions and power handling capabilities. The pass
device is determined by the base drive available, the input and
output voltage, and the maximum charge current.
Select the pass transistor with a collector-emitter breakdown
voltage that exceeds the maximum adapter voltage. A VCEO
rating of at least 15 V is recommended.
To provide a charge current of IMAX with a minimum base drive
of 40 mA requires a PNP beta of at least
βMIN =
IMAX
IMAX
=
40mA
IΒ
It should be noted that the adapter voltage can be either preregulated or unregulated. In the preregulated case the difference
between the maximum and minimum adapter voltage is small.
In this case use the maximum regulated adapter voltage to
determine the maximum power dissipation. In the unregulated
case, the adapter voltage can have a wide range specified. However, the maximum voltage specified is usually with no load
applied. Therefore, the worst-case power dissipation calculation
often leads to an over-specified pass device. In either case, it is
best to determine the load characteristics of the adapter to
optimize the charger design.
For example:
VADAPTER(MIN) = 5.0 V
VADAPTER(MAX) = 6.0 V
IMAX = 500 mA
VPROTECT = 0.2 V at 500 mA
VADJ = 3 V
VRS = 150 mV
(5)
Note that the beta of a transistor drops off with collector
current. Therefore, make sure the beta at IMAX meets the
minimum requirement.
βMIN =
For cases where the adapter voltage is low (less than 5.5 V)
calculate the saturation voltage using the following equation:
VCE(SAT) = VADAPTER(MIN) − VPROTECT − VRS − VBAT
IMAX 500mA
=
= 12.5
40mA
IΒ
VCE(SAT) = VADAPTER(MIN) − VPROTECT − VRS − VBAT
= 5.0 V − 0.2 V − 0.15 V − 4.2 V
= 0.45 V
(6)
where VPROTECT = the forward drop of the reverse input
protection.
PDISS (W) = IMAX × (VADAPTER(MAX) − VPROTECT − VRS − VBAT)
= 0.50 A × (6.0 V − 0.2 V − 0.15 V − 2.8 V)
= 1.4 W
A guide for selecting the PNP transistor is given in Table 5.
Table 5. PNP Pass Transistor Selection Guide
Vendor
Fairchild
ON Semi
Philips
ZETEX
Part Number
FSB6726
NZT45H8
MTB35200
BCP53T1
MMJT9435
BCP51
ZXT10P20DE6
ZXT2M322
FZT549
FMMT549
Package
SuperSOT
SOT223
TSOP-6
SOT223
SOT223
SOT223
SOT23-6
2 mm × 2 mm MLP
SOT223
SOT23
Rev. 0 | Page 13 of 20
Max PD@ 25°C
0.5 W
1.5 W
0.625 W
1.5 W
1.6 W
1.3 W
1.1 W
1.5 W
2W
0.5 W
Beta @1A
150
110
200
35
200
50
270
270
130
130
VCE (SAT)
0.5 V
0.1 V
0.175 V
0.3 V
0.18 V
0.5 V
0.17 V
0.17 V
0.25 V
0.25 V
ADP2291
TYPICAL APPLICATION CIRCUIT
D1
BAT1000
RS
200mΩ
Q1
FZT549
+
CIN
2.2µF
CS
IN
BAT
CHG
GND
RS
200mΩ
Q1
FZT549
CS
BAT
ADP2291
CHG
Figure 24. Selectable Charge Current Circuit
GND
ADJ
04873-0-022
TIMER
CTIMER
100nF
Figure 22. Typical Application Circuit
EOC TERMINATES CHARGING
In some applications, the charger is required to terminate
charging when the EOC threshold is reached. Automatic
charger restart is not desired. Adding components R1, C1, and
Q2 terminates charging when the CHG pin opens and prevents
further charging until the adapter is removed and reasserted.
INPUT
4.6V–12V
THERMAL PROTECTION
In applications where the overall size must be small or the input
voltage range is wide, adding thermal regulation is suggested.
This allows the charger to monitor the temperature of the pass
device and decrease the charge current as the temperature
increases. By adding a NTC thermistor to the ADJ pin it is
possible to accomplish this; however, care is still required to
ensure that the power dissipation of the pass device is not
exceeded.
INPUT
4.6V–12V
D1
BAT1000
RS
200mΩ
D1
BAT1000
CS
R1
500kΩ
COUT
10µF
DRV
IN
Q1
FZT549
+
CS
BAT
CHG
GND
TIMER
GND
CTIMER
100nF
ADJ
CTIMER
100nF
ADJ
R1
470k
NTC LOCATED
NEAR Q1
R2
100k
04873-0-023
C1
100nF
Q2
2N7002
LI-ION
CELL
ADP2291
BAT
CHG
COUT
10µF
DRV
IN
LI-ION
CELL
ADP2291
TIMER
RS
200mΩ
CIN
2.2µF
Q1
FZT549
+
CIN
2.2µF
Q2
2N7002
LOW/HIGH
COUT
10µF
DRV
IN
R2
100kΩ
CTIMER
100nF
+
CIN
2.2µF
ADJ
04873-0-025
D1
BAT1000
LI-ION
CELL
ADP2291
TIMER
INPUT
4.6V–12V
COUT
10µF
DRV
04873-0-024
A typical application circuit is shown in Figure 22. The circuit is
capable of a 750 mA charge current for an input voltage of 4.5 V
to 6 V. Higher input voltages can be used, but the increased
power dissipation of the pass device must be taken into account.
INPUT
4.6V–12V
Figure 25. Thermal Regulation Circuit
Some suggested NTC thermistor suppliers are listed in Table 6.
Figure 23. Self-Termination Circuit
Table 6. NTC Thermistor Manufacturers
SELECTABLE CHARGE CURRENT
In applications where the charge current needs to be selectable,
use the circuit shown in Figure 24. This circuit allows a
processor to determine if the charge current needs to be
reduced due to an input source limitation or a different battery
capacity option, or simply to reduce the stress on the pass
transistor. R2 and Q2 allow the charge current to be selected
between HIGH—750 mA, and LOW—250 mA.
Vendor
BetaTherm
Murata
Panasonic
Vishay
Rev. 0 | Page 14 of 20
Part Number
SMD2500KJ435J
NCP18WM474J
ERTJ0EV474J
2322 615 1.474
Website
www.betatherm.com
www.murata .com
www.panasonic.com
www.vishay.com
ADP2291
VIN < 3.8V
FROM ANYWHERE
ASYNCHRONOUSLY
POWER-DOWN
VRS = 0mV
CHG = OPEN
VIN > 3.8V
START
VRS = 0mV
CHG = OPEN
START SEQUENCE ENDS
VBAT > 2.8V
PRECHARGE
VRS = 15mV
CHG = LOW
VBAT < 2.8V
FAST CHARGE
VRS = 150mV
CHG = LOW
IPNP < C/10 AND
VBAT > 4.1V
T = 30 MIN
VBAT < 4.1V OR
IPNP > C/10
VADJ < 0.4V
BATTERY
FAULT
VRS = 0mV
CHG = OPEN
END OF
CHARGE
VRS = 150mV
CHG = OPEN
T = 3 HOUR
T = 30 MIN
VADJ < 0.4V
SHUTDOWN
VRS = 0mV
CHG = OPEN
VADJ < 0.4V
TIME OUT
VRS = 0mV
CHG = OPEN
TEMP > 135°C
FROM ANYWHERE
ASYNCHRONOUSLY
Figure 26. State Diagram for the ADP2291,
CTIMER = 0.1µF
Rev. 0 | Page 15 of 20
VBAT < 4.1V
04873-0-026
VADJ > 0.4V AND TEMP < 100°C
ADP2291
PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS
Use the following general guidelines when designing printed
circuit boards:
•
Keep the output capacitor as close to the BAT and GND
pins as possible.
•
Keep the input capacitor as close to the IN and GND pins
as possible.
•
PC board traces with larger cross-sectional areas remove
more heat from the pass transistor. For optimum heat
transfer, specify thick copper and use wide traces.
•
Use additional copper layers or planes to reduce the
thermal resistance. When connecting to other layers, use
multiple vias if possible.
Note that the thermal pad is attached to the die substrate,
so the thermal planes that the vias attach the package to
must be electrically isolated or connected to GND.
•
The solder mask opening should be about 120 microns
(4.7 mils) larger than the pad size, resulting in a minimum
of 60 microns (2.4 mils) clearance between the pad and the
solder mask.
•
The paste mask opening is typically designed to match the
pad size used on the peripheral pads of the LFCSP package.
This should provide a reliable solder joint as long as the
stencil thickness is about 0.125 mm. The paste mask for the
thermal pad needs to be designed for the maximum coverage to effectively remove the heat from the package. However, due to the presence of thermal vias and the size of the
thermal pad, eliminating voids may not be possible.
•
The recommended paste mask stencil thickness is
0.125 mm. Use a laser cut stainless steel stencil with
trapezoidal walls.
•
Use a no clean, Type 3 solder paste for mounting the
LFCSP package. A nitrogen purge during the reflow
process is recommended.
•
The package manufacturer recommends that the reflow
temperature not exceed 220°C and the time above liquidus
is less than 75 seconds. Make sure the preheat ramp is
3°C/second or lower. The actual temperature profile
depends on the board’s density and should be determined
by the assembly house.
LFSCP LAYOUT CONSIDERATIONS
The CSP package has an exposed die paddle on the bottom that
efficiently conducts heat to the PCB. In order to achieve the
optimum performance from the CSP package, give special
consideration to the layout of the PCB. Use the following layout
guidelines for the CSP package:
•
•
The pad pattern is shown in Figure 27. Follow the pad
dimension closely for reliable solder joints while
maintaining reasonable clearances to prevent solder
bridging.
The thermal pad of the CSP package provides a low
thermal impedance path (approximately 20°C/W) to the
PCB. Therefore a properly designed PCB effectively conducts the heat away from the package. This is achieved by
adding thermal vias to the PCB that provide a thermal path
to the inner or bottom layers. Note that the via diameter is
small to prevent the solder from flowing through the via
and leaving voids in the thermal pad solder joint.
Rev. 0 | Page 16 of 20
ADP2291
Table 7. Variables Description
2× VIAS, 0.250∅
35µm PLATING
Variable
Name
VX
VRS
0.73
0.30
1.80
0.90
2.36
VBAT, EOC
0.50
IMAX
1.90
3.36
04873-0-027
1.40
IMAX0
C rate
Figure 27. 3 mm × 3 mm LFCSP Pad Pattern
(Dimensions in mm)
Rev. 0 | Page 17 of 20
Description
The voltage on Pin X
The regulation setpoint for the voltage across the
sense resistor (RS)
The battery voltage at the point charging current is
1/10 the current setpoint
The charge current corresponding to VRS,
including the effects of ADJ pin voltage
The charge current corresponding to the VRS
setpoint, ignoring ADJ effects (i.e. C0 = 150 mV/RS)
The charge current (mA) expressed as a multiple of
the nominal battery capacity (mAh). A 900 mAh
capacity battery charged at a 1/10 C rate, is
equivalent to a 90 mA charge current.
ADP2291
OUTLINE DIMENSIONS
3.00
BSC SQ
0.50
0.40
0.30
0.60 MAX
0.45
1
8
PIN 1
INDICATOR
0.90
0.85
0.80
SEATING
PLANE
2.75
BSC SQ
TOP
VIEW
0.50
BSC
1.50
REF
EXPOSED
PAD
(BOTTOM VIEW)
1.90
1.75
1.60
4
5
0.25
MIN
0.80 MAX
0.65 TYP
12° MAX
PIN 1
INDICATOR
1.60
1.45
1.30
0.05 MAX
0.02 NOM
0.30
0.23
0.18
0.20 REF
Figure 28. 8-lead 3 × 3 LFCSP Package
(CP-8)
Dimensions Shown in Millimeters
3.00
BSC
8
5
4.90
BSC
3.00
BSC
4
PIN 1
0.65 BSC
1.10 MAX
0.15
0.00
0.38
0.22
COPLANARITY
0.10
0.23
0.08
0.80
0.60
0.40
8°
0°
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
Figure 29. 8-Lead MSOP Package
(RM-8)
Dimensions Shown in Millimeters
ORDERING GUIDE
Models
ADP2291ARMZ-R71
ADP2291ACPZ-R71
1
Temperature Range
–40°C to +85°C
–40°C to +85°C
Package Description
8-Lead MSOP
8-Lead LFCSP
Z = Pb-free part.
Rev. 0 | Page 18 of 20
Package Option
RM-8
CP-8
Branding
P08
P08
ADP2291
NOTES
Rev. 0 | Page 19 of 20
ADP2291
NOTES
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04873-0-10/04(0)
Rev. 0 | Page 20 of 20