AD ADP3820ART-42

a
Lithium-Ion
Battery Charger
ADP3820
FUNCTIONAL BLOCK DIAGRAM
FEATURES
ⴞ1% Total Accuracy
630 ␮A Typical Quiescent Current
Shutdown Current: 1 ␮A (Typical)
Stable with 10 ␮F Load Capacitor
4.5 V to 15 V Input Operating Range
Integrated Reverse Leakage Protection
6-Lead SOT-23-6 and 8-Lead SO-8 Packages
Programmable Charge Current
–20ⴗC to +85ⴗC Ambient Temperature Range
Internal Gate-to-Source Protective Clamp
+
BIAS
SD
VIN
–
50mV
IS
VREF
GATE
APPLICATIONS
Li-Ion Battery Chargers
Desktop Computers
Hand-Held Instruments
Cellular Telephones
Battery Operated Devices
VOUT
ADP3820
GND
GENERAL DESCRIPTION
The ADP3820 is a precision single cell Li-Ion battery charge
controller that can be used with an external Power PMOS device to form a two-chip, low cost, low dropout linear battery
charger. It is available in two voltage options to accommodate
Li-Ion batteries with coke or graphite anodes. The ADP3820’s
high accuracy (± 1%) low shutdown current (1 µA) and easy
charge current programming make this device especially attractive as a battery charge controller.
Charge current can be set by an external resistor. For example,
50 mΩ of resistance can be used to set the charge current to
1 A. Additional features of this device include foldback current
limit, overload recovery, and a gate-to-source voltage clamp to
protect the external MOSFET. The proprietary circuit also
minimizes the reverse leakage current from the battery if the
input voltage of the charger is disconnected. This feature eliminates the need for an external serial blocking diode.
RS
50mV
VIN
+5V
C1
10mF
R1
10kV
NDP6020P
IO = 1A
VOUT
+
–
Li-Ion
BATTERY
IS
GATE
VIN
VOUT
ADP3820-xx
22mF
SD
GND
Figure 1. Li-Ion Charger Application Circuit
The ADP3820 operates with a wide input voltage range from
4.5 V to 15 V. It is specified over the industrial temperature
range of –20°C to +85°C and is available in the ultrasmall
6-lead surface mount SOT-23-6 and 8-lead SOIC packages.
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
ADP3820–SPECIFICATIONS1(V
Parameter
IN
= [VOUT + 1 V] TA = –20ⴗC to +85ⴗC, unless otherwise noted)
Conditions
Symbol
Min
VIN
VIN = VOUT + 1 V to 15 V
VSD = 2 V
VOUT
VSD = 0 V
VSD = 2 V
IGND
IGND
INPUT VOLTAGE
OUTPUT VOLTAGE ACCURACY
QUIESCENT CURRENT
Shutdown Mode
Normal Mode
Max
Units
4.5
15
V
–1
+1
%
1
630
15
800
µA
µA
6
10
V
GATE TO SOURCE CLAMP VOLTAGE
2
GATE DRIVE MINIMUM VOLTAGE
Typ
0.7
GATE DRIVE CURRENT (SINK/SOURCE)
V
1
mA
 ∆VGS 
GAIN  ∆V

 OUT 
80
dB
CURRENT LIMIT THRESHOLD VOLTAGE
VIN – VIS
40
75
mV
LOAD REGULATION
IOUT = 10 mA to 1 A,
Circuit of Figure 1
–10
+10
mV
VIN = VOUT + 1 V to 15 V
IOUT = 0.1 A
Circuit of Figure 1 (No Battery)
–10
+10
mV
0.4
V
V
+15
µA
5
µA
LINE REGULATION
SD INPUT VOLTAGE
VIH
VIL
VSD
SD INPUT CURRENT
VSD = 0 V to 5 V
ISD
OUTPUT REVERSE LEAKAGE CURRENT
VIN = Floating
IDISCH
2.0
–15
3
NOTES
1
All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC).
2
Provided gate-to-source clamp voltage is not exceeded.
Specifications subject to change without notice.
ORDERING GUIDE
ABSOLUTE MAXIMUM RATINGS*
Input Voltage, VIN ␣ . . . . . . . . . . . . . . . . . . . . . . . . . . . . ⴙ20 V
Enable Input Voltage . . . . . . . . . . . . . . . 0.3 V to (VIN + 0.3 V)
Operating Ambient Temperature Range . . . . –20°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
θJA, SO-8 Package . . . . . . . . . . . . . . . . . . . . . . . . 150°C/W
θJA, SOT-23-6 Package . . . . . . . . . . . . . . . . . . . . 230°C/W
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . +300°C
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . .+215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . .+220°C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 kV
Model
Voltage
Output
Package
Option*
Marking
Code
ADP3820ART-4.1
ADP3820ART-4.2
ADP3820AR-4.1
ADP3820AR-4.2
4.1 V
4.2 V
4.1 V
4.2 V
RT-6 (SOT-23-6) BAC
RT-6 (SOT-23-6) BBC
SO-8
SO-8
*SOT = Surface Mount Package. SO = Small Outline.
Contact the factory for availability of other output voltage options.
*This is a stress rating only; operation beyond these limits can cause the device
to be permanently damaged.
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 the ADP3820 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.
–2–
WARNING!
ESD SENSITIVE DEVICE
REV. A
ADP3820
PIN FUNCTION DESCRIPTIONS
Pin
Pin
SOT-23-6 SO-8
Name
Function
1
SD
Shutdown. Pulling this pin low
will disable the output.
Device Ground. This pin should
be tied to system ground closest
to the load.
Output Voltage Sense. This pin
is connected to the MOSFET’s
drain and directly to the load for
optimal load regulation. Bypass
to ground with a 10 µF or larger
capacitor.
Gate drive for the external
MOSFET.
Input Voltage. This is also the
positive terminal connection of
the current sense resistor.
Current Sense. Used to sense the
input current by monitoring the
voltage across the current sense
resistor. It is connected to the
more negative terminal of the
resistor as well as the power
MOSFET’s source pin. IS pin
should be tied to the VIN pin if
the current limit feature is not
used.
No Connect.
2
8
7
GND
3
5
VOUT
4
3
GATE
5
4
VIN
6
1
IS
2, 6
NC
REV. A
PIN CONFIGURATIONS
SO-8
IS 1
NC 2
ADP3820
RT-6 (SOT-23-6)
8
SD
7
GND
TOP VIEW
GATE 3 (Not to Scale) 6 NC
VIN 4
5
NC = NO CONNECT
–3–
VOUT
SD 1
GND 2
6
ADP3820
IS
VIN
TOP VIEW
VOUT 3 (Not to Scale) 4 GATE
5
ADP3820 –Typical Performance Characteristics
4.110
0.760
VIN = 5.1V
I LOAD = 10mA
4.105
0.720
IGND – mA
OUTPUT VOLTAGE – V
0.740
4.100
0.700
0.680
0.660
4.095
0.640
4.090
0
200
400
600
ILOAD – mA
800
0.620
1000
5
7
4.110
15
0.900
I LOAD = 1A
ILOAD = 1A
4.105
0.850
IGND – mA
OUTPUT VOLTAGE – V
13
Figure 5. IGND vs. VIN (I LOAD = 10 mA)*
Figure 2. V OUT vs. ILOAD (VIN = 5.1 V)*
4.100
4.095
4.090
9
11
INPUT VOLTAGE – V
0.800
0.750
5
7
9
11
13
0.700
15
5
7
INPUT VOLTAGE – V
9
11
INPUT VOLTAGE – V
13
15
Figure 6. IGND vs. VIN (I LOAD = 1 A)*
Figure 3. VOUT vs. VIN (ILOAD = 1 A)*
1.200
4.110
VIN = 5.1V
I LOAD = 10mA
4.105
1.000
IGND – mA
OUTPUT VOLTAGE – V
1.100
4.100
0.900
0.800
0.700
4.095
0.600
4.090
5
7
9
11
13
0.500
0.001
15
0.1
10
1000
ILOAD – mA
INPUT VOLTAGE – V
Figure 4. VOUT vs. VIN (I LOAD = 10 mA)*
Figure 7. I GND vs. ILOAD (VIN = 5.1 V)*
*Reference Figure 1.
–4–
REV. A
ADP3820
1.100
4.230
VIN = 5.1V
I LOAD = 10mA
4.210
1.000
VOUT = 4.2V
OUTPUT VOLTAGE – V
4.190
IGND – mA
0.900
0.800
0.700
4.170
4.150
4.130
VOUT = 4.1V
4.110
0.600
4.090
0.500
–40
0
–20
20
40
TEMPERATURE – 8C
60
4.070
–40
80
Figure 8. Quiescent Current vs. Temperature*
–20
3.5
–30
3.0
PSRR – dB
OUTPUT VOLTAGE – V
80
CLOAD = 10mF
I LOAD = 1mA
–10
4.0
2.5
2.0
1.5
–40
–50
–60
–70
1.0
–80
0.5
–90
–100
0
0
1
2
3
4
5
4
3
INPUT VOLTAGE – V
2
1
100
10
0
Figure 9. Power-Up/Power-Down*
1k
10k
100k
FREQUENCY – Hz
1M
10M
120
140
Figure 12. Ripple Rejection*
5.000
7.0
VIN = 5.1V
RS = 0.5V
5.5
4.000
OUTPUT VOLTAGE – V
INPUT
VOLTAGE – V
60
0
I LOAD = 10mA
ILOAD = 10mA
COUT = 10mF
OUTPUT
VOLTAGE – V
20
40
TEMPERATURE – 8C
Figure 11. VOUT vs. Temperature, VIN = 5.1 V, ILOAD = 10 mA*
4.5
4.2
3.000
2.000
4.1
1.000
4.0
0.000
Figure 10. Line Transient Response (10 µ F Output Cap)*
REV. A
0
–20
0
20
40
60
80
ILOAD – mA
100
Figure 13. Current Limit Foldback*
–5–
ADP3820
ADP3820. This k factor between VO of 0 V to about 2.5 V is:
k ~ 0.65.
APPLICATION INFORMATION
The ADP3820 is very easy to use. A P-channel power MOSFET and a small capacitor on the output is all that is needed to
form an inexpensive Li-Ion battery charger. The advantage of
using the ADP3820 controller is that it can directly drive a
PMOS FET to provide a regulated output current until the
battery is charged. When the specified battery voltage is reached,
the charge current is reduced and the ADP3820 maintains the
maximum specified battery voltage accurately.
θ JA = ∆T/(IO × k × VIN ) = 100/(1 × 0.65 × 5) = 30.7°C/W
This thermal impedance can be realized using the transistor
shown in Figure 1 when surface mounted to a 40 × 40 mm
double-sided PCB with many vias around the tab of the surfacemounted FET to the backplane of the PCB. Alternatively, a
TO-220 packaged FET mounted to a heatsink could be used.
The θ or thermal impedance of a suitable heatsink is calculated
below:
When fully charged, the circuit in Figure 1 works like a well
known linear regulator, holding the output voltage within the
specified accuracy as needed by single cell Li-Ion batteries. The
output is sensed by the VOUT pin. When charging a discharged
battery, the circuit maintains a set charging current determined
by the current sense resistor until the battery is fully charged,
then reduces it to a trickle charge to keep the battery at the
specified voltage. The voltage drop across the RS current sense
resistor is sensed by the IS input of the ADP3820. At minimum
battery voltage or at shorted battery, the circuit reduces this
current (foldback) to limit the dissipation of the FET (see Figure 13). Both the VIN input and VOUT sense pins of the IC need
to be bypassed by a suitable bypass capacitor.
θ < (θ JA – θJC) = 30.7 – 2 = +28.7°C/W
Where the θ JC, or junction-to-case thermal impedance of the
FET can be read from the FET data sheet. A low cost such
heatsink is type PF430 made by Thermalloy, with a θ =
+25.3°C/W.
The current sense resistor for this application can be simply
calculated:
R S = VS /IO = 0.05/1 = 50 mΩ
Where VS is specified on the data sheet as current limit threshold
voltage at 40 mV–75 mV. For battery charging applications, it
is adequate to use the typical 50 mV midvalue.
A 6 V gate-to-source voltage clamp is provided by the ADP3820
to protect the MOSFET gates at higher source voltages. The
ADP3820 also has a TTL SD input, which may be connected to
the input voltage to enable the IC. Pulling it to low or to
ground will disable the FET-drive.
B. Nonpreregulated Input Voltage
If the input voltage source is, for example, a rectified and
capacitor-filtered secondary voltage of a small wall plug-in
transformer, the heatsinking requirement is more demanding.
The VINMIN should be specified 5 V, but at the lowest line voltage and full load current. The required thermal impedance can
be calculated the same way as above, but here we have to use
the maximum output rectified voltage, which can be substantially higher than 5 V, depending on transformer regulation and
line voltage variation. For example, if VINMAX is 10 V
Design Approach
Due to the lower efficiency of Linear Regulator Charging, the
most important factor is the thermal design and cost, which is
the direct function of the input voltage, output current and
thermal impedance between the MOSFET and the ambient
cooling air. The worse-case situation is when the battery is
shorted since the MOSFET has to dissipate the maximum power.
θJA = ∆T/(IO × k × VINMAX) = 100/(1 × 0.65 × 10) = +15.3°C/W
A tradeoff must be made between the charge current, cost and
thermal requirements of the charger. Higher current requires a
larger FET with more effective heat dissipation leading to a
more expensive design. Lowering the charge current reduces
cost by lowering the size of the FET, possibly allowing a smaller
package such as SOT-23-6. The following designs consider both
options. Furthermore, each design is evaluated under two input
source voltage conditions.
The θ suitable heatsink thermal impedance:
θ < θJA – θJC = 15.3 – 2 = 13.3°C/W
A low cost heatsink is Type 6030B made by Thermalloy, with a
θ = +12.5°C/W.
Lower Current Option
A. Preregulated Input Voltage (5 V ⴞ 10%)
If lower charging current is allowed, the θJA value can be increased,
and the system cost decreased. The lower cost is assured by
using an inexpensive MOSFET with, for example, a NDT452P
in a SOT-23-6 package mounted on a small 40 × 40 mm area
on double-sided PCB. This provides a convection cooled thermal impedance of θ JA = +55°C/W, presuming many vias are
used around the FET to the backplane. Allowing a maximum
FET junction temperature of +150°C, at +50°C ambient, and
at convection cooling the maximum allowed heat rise is thus
150°C–50°C = 100°C.
Regarding input voltage, there are two options:
A. The input voltage is preregulated, e.g., 5 V ± 10%
B. The input voltage is not a preregulated source, e.g., a wall
plug-in transformer with a rectifier and capacitive filter.
Higher Current Option
A. Preregulated Input Voltage (5 V ⴞ 10%)
For the circuit shown in Figure 1, the required θJA thermal
impedance can be calculated as follows: if the FET data sheet
allows a max FET junction temperature of TJMAX = 150°C, then
at 50°C ambient and at convection cooling, the maximum allowed ∆T junction temperature rise is thus, TJMAX – TAMAX =
150°C – 50°C = 100°C.
The maximum foldback current allowed:
IFB = ∆T/(θ × VIN ) = 100/(55 × 5) = 0.33 A
Thus the full charging current:
The maximum current for a shorted or discharged battery is
reduced from the set charge current by a multiplier factor shown
in Figure 13 due to the foldback current limiting feature of the
IOUTMAX = IFB/k = 0.5 A
k is calculated in the above example.
–6–
REV. A
ADP3820
The current sense resistor for this application:
Gate-to-Source Clamp
A 6 V gate-to-source voltage clamp is provided by the ADP3820 to
protect most MOSFET gates in the event the VIN > VGS allowed
and the output is suddenly shorted to ground. This allows use of
the new, low RDS(ON) MOSFETs.
R S = VS/IO = 0.05/0.5 = 100 mΩ
FET Selection
The type and size of the pass transistor are determined by the
threshold voltage, input-output voltage differential and load
current. The selected PMOS must satisfy the physical and thermal design requirements. To ensure that the maximum VGS
provided by the controller will turn on the FET at worst case
conditions, (i.e., temperature and manufacturing tolerances) the
maximum available VGS must be determined. Maximum VGS is
calculated as follows:
Short Circuit Protection
The power FET is protected during short circuit conditions
with a foldback type of current limiting that significantly reduces the current. See Figure 13 for foldback current limit
information.
Current Sense Resistor
Current limit is achieved by setting an appropriate current sense
resistor (RS) across the current limit threshold voltage. Current
limit sense resistor, RS, is calculated as shown above. Proper
derating is advised to select the power dissipation rating of the
resistor.
VGS = VIN – VBE – IOUTMAX × RS
where
IOUTMAX = Maximum Output Current
= Current Sense Resistor
RS
~ 0.7 V (Room Temperature)
VBE
~ 0.5 V (Hot)
~ 0.9 V (Cold)
The simplest and cheapest sense resistor for high current applications, (i.e., Figure 1) is a PCB trace. However, the temperature dependence of the copper trace and the thickness tolerances of
the trace must be considered in the design. The resistivity of
copper has a positive temperature coefficient of +0.39%/°C.
Copper’s Tempco, in conjunction with the proportional-toabsolute temperature (± 0.3%) current limit voltage, can provide
an accurate current limit. Table I provides the typical resistance
values for PCB copper traces. Alternately, an appropriate sense
resistor, such as surface mount sense resistors, available from
KRL, can be used.
For example:
VIN = 5 V, and IOUTMAX = 1 A,
VGS = 5 V – 0.7 V – 1 A × 50 mΩ = 4.25 V
If VGS < 5 V, logic level FET should be considered.
If VGS > 5 V, either logic level or standard MOSFET can be
used.
The difference between VIN and VO (VDS) must exceed the
voltage drop due to the sense resistor plus the ON-resistance
of the FET at the maximum charge current. The selected
MOSFET must satisfy these criteria; otherwise, a different pass
device should be used.
Table I. Printed Circuit Copper Resistance
Conductor
Thickness
VDS = VIN – VO = 5 V – 4.2 V = 0.8 V
1/2oz/ft2
(18 µm)
The maximum RDS(ON) required at the available gate drive (VDR)
and Drain-to-Source voltage (VDS) is:
RDS(ON) = VDS/IOUTMAX
From the Drain-to Source current vs. Drain-to-Source voltage
vs. gate drive graph off the MOSFET data sheet, it can be determined if the above calculated RDS(ON) is higher than the graph
indicates. However, the value read from the MOSFET data
sheet graph must be adjusted based on the junction temperature
of the MOSFET. This adjustment factor can be obtained from
the normalized RDS(ON) vs. junction temperature graph in the
MOSFET data sheet.
1oz/ft2
(35 µm)
2oz/ft2
(70 µm)
External Capacitors
The ADP3820 is stable with or without a battery load, and
virtually any good quality output filter capacitors can be used
(anyCAP™), independent of the capacitor’s minimum ESR
(Effective Series Resistance) value. The actual value of the
capacitor and its associated ESR depends on the gm and capacitance of the external PMOS device. A 10 µF tantalum or aluminum electrolytic capacitor at the output is sufficient to ensure
stability for up to a 10 A output current.
3oz/ft2
(106 µm)
Shutdown Mode
Applying a TTL high signal to the SD pin or tying it to the
input pin will enable the output. Pulling this pin low or tying
it to ground will disable the output. In shutdown mode, the
controller’s quiescent current is reduced to less than 1 µA.
anyCAP is a trademark of Analog Devices, Inc.
REV. A
–7–
Conductor
Width/Inch
Resistance
m⍀/In
0.025
0.050
0.100
0.200
0.500
39.3
19.7
9.83
4.91
1.97
0.025
0.050
0.100
0.200
0.500
19.7
9.83
4.91
2.46
0.98
0.025
0.050
0.100
0.200
0.500
9.83
4.91
2.46
1.23
0.49
0.025
0.050
0.100
0.200
0.500
6.5
3.25
1.63
0.81
0.325
ADP3820
For optimum voltage regulation, place the load as close as possible to the device’s VOUT and GND pins. It is recommended to
use dedicated PCB traces to connect the MOSFET’s drain to
the positive terminal and GND to the negative terminal of the
load to avoid voltage drops along the high current carrying PCB
traces.
C2986a–2–9/99
If PCB layout is used as heatsink, adding many vias around the
power FET helps conduct more heat from the FET to the backplane of the PCB, thus reducing the maximum FET junction
temperature.
PCB Layout Issues
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
6-Lead Plastic Surface Mount Package
RT-6 (SOT-23-6)
0.122 (3.10)
0.106 (2.70)
0.071 (1.80)
0.059 (1.50)
6
5
4
1
2
3
0.118 (3.00)
0.098 (2.50)
PIN 1
0.037 (0.95) BSC
0.075 (1.90)
BSC
0.051 (1.30)
0.035 (0.90)
0.057 (1.45)
0.035 (0.90)
0.020 (0.50) SEATING
0.010 (0.25) PLANE
0.006 (0.15)
0.000 (0.00)
108
0.009 (0.23) 08
0.003 (0.08)
0.022 (0.55)
0.014 (0.35)
8-Lead Narrow Body Package
SO-8
0.1968 (5.00)
0.1890 (4.80)
0.1574 (4.00)
0.1497 (3.80)
8
5
1
4
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.0196 (0.50)
3 458
0.0099 (0.25)
0.0500 (1.27)
BSC
SEATING
PLANE
0.0688 (1.75)
0.0532 (1.35)
88
0.0500 (1.27)
0.0098 (0.25) 08
0.0160 (0.41)
0.0075 (0.19)
0.0192 (0.49)
0.0138 (0.35)
PRINTED IN U.S.A.
0.0098 (0.25)
0.0040 (0.10)
–8–
REV. A