LM3420 [TI]
8.4-V Li-Ion Battery Charge Controller;
| 型号： | LM3420 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 8.4-V Li-Ion Battery Charge Controller 电池 |
| 文件： | 总27页 (文件大小：1268K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LM3420
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SNVS116D –MAY 1998–REVISED MAY 2013
LM3420-4.2, -8.2, -8.4, -12.6, -16.8 Lithium-Ion Battery Charge Controller
Check for Samples: LM3420
1
FEATURES
DESCRIPTION
The LM3420 series of controllers are monolithic
integrated circuits designed for charging and end-of-
charge control for Lithium-Ion rechargeable batteries.
The LM3420 is available in five fixed voltage versions
for one through four cell charger applications (4.2V,
8.2V/8.4V, 12.6V and 16.8V respectively).
23
•
Voltage Options for Charging 1, 2, 3 or 4 Cells
Tiny SOT-23-5 Package
•
•
•
•
Precision (0.5%) End-of-Charge Control
Drive Capability for External Power Stage
Low Quiescent Current, 85 μA (Typ.)
Included in a very small package is an (internally
compensated) op amp, a bandgap reference, an NPN
output transistor, and voltage setting resistors. The
amplifier's inverting input is externally accessible for
loop frequency compensation. The output is an open-
emitter NPN transistor capable of driving up to 15 mA
of output current into external circuitry.
APPLICATIONS
•
•
Lithium-Ion Battery Charging
Suitable for Linear and Switching Regulator
Charger Designs
A
trimmed precision bandgap reference utilizes
temperature drift curvature correction for excellent
voltage stability over the operating temperature
range. Available with an initial tolerance of 0.5% for
the A grade version, and 1% for the standard version,
the LM3420 allows for precision end-of-charge control
for Lithium-Ion rechargeable batteries.
The LM3420 is available in a sub-miniature 5-lead
surface mount package thus allowing very compact
designs.
Typical Application and Functional Diagram
Figure 1. Typical Constant Current/Constant Voltage
Li-Ion Battery Charger
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SIMPLE SWITCHER is a trademark of Texas Instruments.
2
3
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1998–2013, Texas Instruments Incorporated
LM3420
SNVS116D –MAY 1998–REVISED MAY 2013
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Figure 2. LM3420 Functional Diagram
Connection Diagrams
5-Lead Small Outline Package
Top View
Actual Size
*No internal connection, but should be soldered to PC board for best
heat transfer.
Figure 3. SOT-23 Package
See Package DBV0005A
Figure 4. SOT-23 Package
See Package DBV0005A
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS(1)(2)
Input Voltage V(IN)
20V
20 mA
Output Current
Junction Temperature
Storage Temperature
150°C
−65°C to +150°C
+215°C
Vapor Phase (60 seconds)
Infrared (15 seconds)
Lead Temperature
+220°C
Power Dissipation (TA = 25°C)(3)
ESD Susceptibility(4)
300 mW
Human Body Model
1500V
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics. The specified specifications apply only for the test conditions listed. Some performance
characteristics may degrade when the device is not operated under the listed test conditions.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature),
θJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any
temperature is PDmax = (TJmax − TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. The typical thermal
resistance (θJA) when soldered to a printed circuit board is approximately 306°C/W for the DBV0005A package.
(4) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
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OPERATING RATINGS(1)(2)
Ambient Temperature Range
Junction Temperature Range
Output Current
−40°C ≤ TA ≤ +85°C
−40°C ≤ TJ ≤ +125°C
15 mA
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics. The specified specifications apply only for the test conditions listed. Some performance
characteristics may degrade when the device is not operated under the listed test conditions.
(2) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature),
θJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any
temperature is PDmax = (TJmax − TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. The typical thermal
resistance (θJA) when soldered to a printed circuit board is approximately 306°C/W for the DBV0005A package.
LM3420-4.2
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, V(IN) = VREG, VOUT = 1.5V.
LM3420A-4.2
Limit(2)
LM3 Limit(2)
420-4.2
Symbol
Parameter
Conditions
Typical(1)
Units (Limits)
VREG
IOUT = 1 mA
4.2
V
Regulation Voltage
4.221/4.242
4.179/4.158
4.242/4.284
4.158/4.116
V(max)
V(min)
Regulation Voltage
Tolerance
IOUT = 1 mA
IOUT = 1 mA
±0.5/±1
±1/±2
%(max)
Iq
85
3.3
μA
μA(max)
mA/mV
mA/mV(min)
mA/mV
mA/mV(min)
V/V
Quiescent Current
110/115
1.3/0.75
3.0/1.5
125/150
1.0/0.50
2.5/1.4
Gm
20 μA ≤ IOUT ≤ 1 mA
VOUT = 2V
Transconductance
ΔIOUT/ΔVREG
1 mA ≤ IOUT ≤ 15 mA
VOUT = 2V
6.0
AV
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
1000
3500
1.0
(3)
RL = 200Ω
550/250
1500/900
1.2/1.3
450/200
1000/700
1.2/1.3
V/V(min)
V/V
Voltage Gain
ΔVOUT/ΔVREG
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 2 kΩ
V/V(min)
V
VSAT
V(IN) = VREG +100 mV
IOUT = 15 mA
Output Saturation(4)
V(max)
μA
IL
V(IN) = VREG −100 mV
VOUT = 0V
0.1
Output Leakage
Current
0.5/1.0
0.5/1.0
μA(max)
kΩ
Rf
75
Internal Feedback
Resistor(5)
94
56
94
56
kΩ(max)
kΩ(min)
μVRMS
En
Output Noise Voltage IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
70
(1) Typical numbers are at 25°C and represent the most likely parametric norm.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlation using
Statistical Quality Control (SQC) methods. The limits are used to calculate Averaging Outgoing Quality Level (AOQL).
(3) Actual test is done using equivalent current sink instead of a resistor load.
(4) VSAT = V(IN) − VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
(5) See Applications and Typical Performance Characteristics sections for information on this resistor.
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LM3420-8.2
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, V(IN) = VREG, VOUT = 1.5V.
LM3420A-8.2
Limit(2)
LM3420-8.2
Limit(2)
Symbol
Parameter
Conditions
Typical(1)
Units (Limits)
VREG
IOUT = 1 mA
8.2
V
Regulation Voltage
8.241/8.282
8.159/8.118
8.282/8.364
8.118/8.036
V(max)
V(min)
Regulation Voltage
Tolerance
IOUT = 1 mA
IOUT = 1 mA
±0.5/±1
±1/±2
%(max)
Iq
85
3.3
μA
μA(max)
mA/mV
mA/mV(min)
mA/mV
mA/mV(min)
V/V
Quiescent Current
110/115
1.3/0.75
3.0/1.5
125/150
1.0/0.50
2.5/1.4
Gm
20 μA ≤ IOUT ≤ 1 mA
VOUT = 6V
Transconductance
ΔIOUT/ΔVREG
1 mA ≤ IOUT ≤ 15 mA
VOUT = 6V
6.0
AV
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 470Ω(3)
1000
3500
1.0
550/250
1500/900
1.2/1.3
450/200
1000/700
1.2/1.3
V/V(min)
V/V
Voltage Gain
ΔVOUT/ΔVREG
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 5 kΩ
V/V(min)
V
VSAT
V(IN) = VREG +100 mV
IOUT = 15 mA
Output Saturation(4)
V(max)
μA
IL
V(IN) = VREG −100 mV
VOUT = 0V
0.1
Output Leakage
Current
0.5/1.0
0.5/1.0
μA(max)
kΩ
Rf
176
Internal Feedback
Resistor(5)
220
132
220
132
kΩ(max)
kΩ(min)
μVRMS
En
Output Noise Voltage IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
140
(1) Typical numbers are at 25°C and represent the most likely parametric norm.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlation using
Statistical Quality Control (SQC) methods. The limits are used to calculate Averaging Outgoing Quality Level (AOQL).
(3) Actual test is done using equivalent current sink instead of a resistor load.
(4) VSAT = V(IN) − VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
(5) See Applications and Typical Performance Characteristics sections for information on this resistor.
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LM3420-8.4
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, V(IN) = VREG, VOUT = 1.5V.
LM3420A-8.4
Limit(2)
LM3420-8.4
Limit(2)
Symbol
Parameter
Conditions
Typical(1)
Units (Limits)
VREG
IOUT = 1 mA
8.4
V
Regulation Voltage
8.442/8.484
8.358/8.316
8.484/8.568
8.316/8.232
V(max)
V(min)
Regulation Voltage
Tolerance
IOUT = 1 mA
IOUT = 1 mA
±0.5/±1
±1/±2
%(max)
Iq
85
3.3
μA
μA(max)
mA/mV
mA/mV(min)
mA/mV
mA/mV(min)
V/V
Quiescent Current
110/115
1.3/0.75
3.0/1.5
125/150
1.0/0.50
2.5/1.4
Gm
20 μA ≤ IOUT ≤ 1 mA
VOUT = 6V
Transconductance
ΔIOUT/ΔVREG
1 mA ≤ IOUT ≤ 15 mA
VOUT = 6V
6.0
AV
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 470Ω(3)
1000
3500
1.0
550/250
1500/900
1.2/1.3
450/200
1000/700
1.2/1.3
V/V(min)
V/V
Voltage Gain
ΔVOUT/ΔVREG
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 5 kΩ
V/V(min)
V
VSAT
V(IN) = VREG +100 mV
IOUT = 15 mA
Output Saturation(4)
V(max)
μA
IL
V(IN) = VREG −100 mV
VOUT = 0V
0.1
Output Leakage
Current
0.5/1.0
0.5/1.0
μA(max)
kΩ
Rf
181
Internal Feedback
Resistor(5)
227
135
227
135
kΩ(max)
kΩ(min)
μVRMS
En
Output Noise Voltage IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
140
(1) Typical numbers are at 25°C and represent the most likely parametric norm.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlation using
Statistical Quality Control (SQC) methods. The limits are used to calculate Averaging Outgoing Quality Level (AOQL).
(3) Actual test is done using equivalent current sink instead of a resistor load.
(4) VSAT = V(IN) − VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
(5) See Applications and Typical Performance Characteristics sections for information on this resistor.
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LM3420-12.6
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, V(IN) = VREG, VOUT = 1.5V.
LM3420A-12.6
Limit(2)
LM3420-12.6
Limit(2)
Symbol
Parameter
Conditions
Typical(1)
Units (Limits)
VREG
IOUT = 1 mA
12.6
V
Regulation Voltage
12.663/12.726
12.537/12.474
12.726/12.852
12.474/12.348
V(max)
V(min)
Regulation Voltage
Tolerance
IOUT = 1 mA
IOUT = 1 mA
±0.5/±1
±1/±2
%(max)
Iq
85
3.3
μA
μA(max)
mA/mV
mA/mV(min)
mA/mV
mA/mV(min)
V/V
Quiescent Current
110/115
1.3/0.75
3.0/1.5
125/150
1.0/0.5
Gm
20 μA ≤ IOUT ≤ 1 mA
VOUT = 10V
Transconductance
ΔIOUT/ΔVREG
1 mA ≤ IOUT ≤ 15 mA
VOUT = 10V
6.0
2.5/1.4
AV
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 750Ω(3)
1000
3500
1.0
550/250
1500/900
1.2/1.3
450/200
1000/700
1.2/1.3
V/V(min)
V/V
Voltage Gain
ΔVOUT/ΔVREG
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 10 kΩ
V/V(min)
V
VSAT
V(IN) = VREG +100 mV
IOUT = 15 mA
Output Saturation(4)
V(max)
μA
IL
V(IN) = VREG −100 mV
VOUT = 0V
0.1
Output Leakage
Current
0.5/1.0
0.5/1.0
μA(max)
kΩ
Rf
287
Internal Feedback
Resistor(5)
359
215
359
215
kΩ(max)
kΩ(min)
μVRMS
En
Output Noise Voltage IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
210
(1) Typical numbers are at 25°C and represent the most likely parametric norm.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlation using
Statistical Quality Control (SQC) methods. The limits are used to calculate Averaging Outgoing Quality Level (AOQL).
(3) Actual test is done using equivalent current sink instead of a resistor load.
(4) VSAT = V(IN) − VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
(5) See Applications and Typical Performance Characteristics sections for information on this resistor.
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LM3420-16.8
ELECTRICAL CHARACTERISTICS
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range. Unless otherwise specified, V(IN) = VREG, VOUT = 1.5V.
LM3420A-16.8
Limit(2)
LM3420-16.8
Limit(2)
Symbol
Parameter
Conditions
Typical(1)
Units (Limits)
VREG
IOUT = 1 mA
16.8
V
Regulation Voltage
16.884/16.968
16.716/16.632
16.968/17.136
16.632/16.464
V(max)
V(min)
Regulation Voltage
Tolerance
IOUT = 1 mA
IOUT = 1 mA
±0.5/±1
±1/±2
%(max)
Iq
85
3.3
μA
μA(max)
mA/mV
mA/mV(min)
mA/mV
mA/mV(min)
V/V
Quiescent Current
110/115
0.8/0.4
125/150
0.7/0.35
2.5/0.75
450/200
1000/650
1.2/1.3
Gm
20 μA ≤ IOUT ≤ 1 mA
VOUT = 15V
Transconductance
ΔIOUT/ΔVREG
1 mA ≤ IOUT ≤ 15 mA
VOUT = 15V
6.0
2.9/0.9
AV
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 1 kΩ(3)
1000
3500
1.0
550/250
1200/750
1.2/1.3
V/V(min)
V/V
Voltage Gain
ΔVOUT/ΔVREG
1V ≤ VOUT ≤ VREG − 1.2V (−1.3)
RL = 15 kΩ
V/V(min)
V
VSAT
V(IN) = VREG +100 mV
IOUT = 15 mA
Output Saturation(4)
V(max)
μA
IL
V(IN) = VREG −100 mV
VOUT = 0V
0.1
Output Leakage
Current
0.5/1.0
0.5/1.0
μA(max)
kΩ
Rf
392
Internal Feedback
Resistor(5)
490
294
490
294
kΩ(max)
kΩ(min)
μVRMS
En
Output Noise Voltage IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
280
(1) Typical numbers are at 25°C and represent the most likely parametric norm.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlation using
Statistical Quality Control (SQC) methods. The limits are used to calculate Averaging Outgoing Quality Level (AOQL).
(3) Actual test is done using equivalent current sink instead of a resistor load.
(4) VSAT = V(IN) − VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
(5) See Applications and Typical Performance Characteristics sections for information on this resistor.
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TYPICAL PERFORMANCE CHARACTERISTICS
4.2V Bode Plot
Response Time for 4.2V Version
Figure 5.
Figure 6.
Response Time for 4.2V Version
8.2V and 8.4V Bode Plot
Figure 7.
Figure 8.
Response Time for
8.2V, 8.4V Versions
Response Time for
8.2V, 8.4V Versions
Figure 9.
Figure 10.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
12.6V Bode Plot
Response Time for 12.6V Version
Figure 11.
Figure 12.
Response Time for 12.6V Version
16.8V Bode Plot
Figure 13.
Figure 14.
Response Time for 16.8V Version
Response Time for 16.8V Version
Figure 15.
Figure 16.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Regulation Voltage vs
Output Voltage and
Load Resistance
Circuit Used for Bode Plots
Figure 17.
Figure 18.
Regulation Voltage vs
Output Voltage and
Load Resistance
Circuit Used for Response Time
Figure 19.
Figure 20.
Internal Feedback
Resistor (Rf) Tempco
Quiescent Current
Figure 21.
Figure 22.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Regulation Voltage vs
Output Voltage and
Load Resistance
Normalized
Temperature Drift
Figure 23.
Figure 24.
Regulation Voltage vs
Output Voltage and
Load Resistance
Output Saturation
Voltage (VSAT
)
Figure 25.
Figure 26.
PRODUCT DESCRIPTION
The LM3420 is a shunt regulator specifically designed to be the reference and control section in an overall
feedback loop of a Lithium-Ion battery charger. The regulated output voltage is sensed between the IN pin and
GROUND pin of the LM3420. If the voltage at the IN pin is less than the LM3420 regulating voltage (VREG), the
OUT pin sources no current. As the voltage at the IN pin approaches the VREG voltage, the OUT pin begins
sourcing current. This current is then used to drive a feedback device (opto-coupler), or a power device (linear
regulator, switching regulator, etc.), which servos the output voltage to be the same value as VREG
.
In some applications, (even under normal operating conditions) the voltage on the IN pin can be forced above
the VREG voltage. In these instances, the maximum voltage applied to the IN pin should not exceed 20V. In
addition, an external resistor may be required on the OUT pin to limit the maximum current to 20 mA.
Compensation
The inverting input of the error amplifier is brought out to allow overall closed-loop compensation. In many of the
applications circuits shown here, compensation is provided by a single capacitor (CC) connected from the
compensation pin to the out pin of the LM3420. The capacitor values shown in the schematics are adequate
under most conditions, but they can be increased or decreased depending on the desired loop response.
Applying a load pulse to the output of a regulator circuit and observing the resultant output voltage response is
an easy method of determining the stability of the control loop.
Analyzing more complex feedback loops requires additional information.
The formula for AC gain at a frequency (f) is as follows;
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where
•
•
•
•
Rf ≈ 75 kΩ for the 4.2V part
Rf ≈ 181 kΩ for the 8.4V part
Rf ≈ 287 kΩ for the 12.6V part
Rf ≈ 392 kΩ for the 16.8V part
(1)
The resistor (Rf) in the formula is an internal resistor located on the die. Since this resistor value will affect the
phase margin, the worst case maximum and minimum values are important when analyzing closed loop stability.
The minimum and maximum room temperature values of this resistor are specified in the Electrical
Characteristics section of this data sheet, and a curve showing the temperature coefficient is shown in the curves
section. Minimum values of Rf result in lower phase margins.
Test Circuit
The test circuit shown in Figure 27 can be used to measure and verify various LM3420 parameters. Test
conditions are set by forcing the appropriate voltage at the VOUT Set test point and selecting the appropriate RL
or IOUT as specified in the Electrical Characteristics section. Use a DVM at the “measure” test points to read the
data.
Figure 27. LM3420 Test Circuit
VREG External Voltage Trim
The regulation voltage (VREG) of the LM3420 can be externally trimmed by adding a single resistor from the
COMP pin to the +IN pin or from the COMP pin to the GND pin, depending on the desired trim direction. Trim
adjustments up to ±10% of VREG can be realized, with only a small increase in the temperature coefficient. (See
temperature coefficient curve shown in Figure 28 below.)
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Figure 28. Normalized Temperature Drift with Output Externally Trimmed
Decreasing VREG
Figure 29. Increasing VREG
Figure 30. Changing VREG
Formulas for selecting trim resistor values are shown below, based on the percent of increase (%incr) or percent
of decrease (%decr) of the output voltage from the nominal voltage.
For LM3420-4.2
Rincrease = 22x105/%incr
Rdecrease = (53x105/%decr) − 75x103
(2)
(3)
For LM3420-8.2
Rincrease = 26x105/%incr
Rdecrease = (150x105/%decr) − 176x103
(4)
(5)
For LM3420-8.4
Rincrease = 26x105/%incr
Rdecrease = (154x105/%decr) − 181x103
(6)
(7)
For LM3420-12.6
Rincrease = 28x105/%incr
Rdecrease = (259x105/%decr) − 287x103
(8)
(9)
For LM3420-16.8
Rincrease = 29x105/%incr
Rdecrease = (364x105/%decr) − 392x103
(10)
(11)
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APPLICATION INFORMATION
The LM3420 regulator/driver provides the reference and feedback drive functions for a Lithium-Ion battery
charger. It can be used in many different charger configurations using both linear and switching topologies to
provide the precision needed for charging Lithium-Ion batteries safely and efficiently. Output voltage tolerances
better than 0.5% are possible without using trim pots or precision resistors. The circuits shown are designed for 2
cell operation, but they can readily be changed for either 1, 3 or 4 cell charging applications.
One item to keep in mind when designing with the LM3420 is that there are parasitic diodes present. In some
designs, under special electrical conditions, unwanted currents may flow. Parasitic diodes exist from OUT to IN,
as well as from GROUND to IN. In both instances the diode arrow is pointed toward the IN pin.
Application Circuits
The circuit shown in Figure 31 performs constant-current, constant-voltage charging of two Li-Ion cells. At the
beginning of the charge cycle, when the battery voltage is less than 8.4V, the LM3420 sources no current from
the OUT pin, keeping Q2 off, thus allowing the LM317 Adjustable voltage regulator to operate as a constant-
current source. (The LM317 is rated for currents up to 1.5A, and the LM350 and LM338 can be used for higher
currents.) The LM317 forces a constant 1.25V across RLIM, thus generating a constant current of
ILIM = 1.25V/RLIM
(12)
Figure 31. Constant Current/Constant Voltage Li-Ion Battery Charger
Figure 32. Low Drop-Out Constant Current/Constant Voltage 2-Cell Charger
Transistor Q1 provides a disconnect between the battery and the LM3420 when the input voltage is removed.
This prevents the 85 μA quiescent current of the LM3420 from eventually discharging the battery. In this
application Q1 is used as a low offset saturated switch, with the majority of the base drive current flowing through
the collector and crossing over to the emitter as the battery becomes fully charged. It provides a very low
collector to emitter saturation voltage (approximately 5 mV). Diode D1 is also used to prevent the battery current
from flowing through the LM317 regulator from the output to the input when the DC input voltage is removed.
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As the battery charges, its voltage begins to rise, and is sensed at the IN pin of the LM3420. Once the battery
voltage reaches 8.4V, the LM3420 begins to regulate and starts sourcing current to the base of Q2. Transistor
Q2 begins controlling the ADJ. pin of the LM317 which begins to regulate the voltage across the battery and the
constant voltage portion of the charging cycle starts. Once the charger is in the constant voltage mode, the
charger maintains a regulated 8.4V across the battery and the charging current is dependent on the state of
charge of the battery. As the cells approach a fully charged condition, the charge current falls to a very low value.
Figure 32 shows a Li-Ion battery charger that features a dropout voltage of less than one volt. This charger is a
constant-current, constant-voltage charger (it operates in constant-current mode at the beginning of the charge
cycle and switches over to a constant-voltage mode near the end of the charging cycle). The circuit consists of
two basic feedback loops. The first loop controls the constant charge current delivered to the battery, and the
second determines the final voltage across the battery.
With a discharged battery connected to the charger, (battery voltage is less than 8.4V) the circuit begins the
charge cycle with a constant charge current. The value of this current is set by using the reference section of the
LM10C to force 200 mV across R7 thus causing approximately 100 μA of emitter current to flow through Q1, and
approximately 1 mA of emitter current to flow through Q2. The collector current of Q1 is also approximately 100
μA, and this current flows through R2 developing 50 mV across it. This 50 mV is used as a reference to develop
the constant charge current through the current sense resistor R1.
The constant current feedback loop operates as follows. Initially, the emitter and collector current of Q2 are both
approximately 1 mA, thus providing gate drive to the MOSFET Q3, turning it on. The output of the LM301A op-
amp is low. As Q3's current reaches 1A, the voltage across R1 approaches 50 mV, thus canceling the 50 mV
drop across R2, and causing the op-amp's output to start going positive, and begin sourcing current into R8. As
more current is forced into R8 from the op-amp, the collector current of Q2 is reduced by the same amount,
which decreases the gate drive to Q3, to maintain a constant 50 mV across the 0.05Ω current sensing resistor,
thus maintaining a constant 1A of charge current.
The current limit loop is stabilized by compensating the LM301A with C1 (the standard frequency compensation
used with this op-amp) and C2, which is additional compensation needed when D3 is forward biased. This helps
speed up the response time during the reverse bias of D3. When the LM301A output is low, diode D3 reverse
biases and prevents the op-amp from pulling more current through the emitter of Q2. This is important when the
battery voltage reaches 8.4V, and the 1A charge current is no longer needed. Resistor R5 isolates the LM301A
feedback node at the emitter of Q2.
The battery voltage is sensed and buffered by the op-amp section of the LM10C, connected as a voltage follower
driving the LM3420. When the battery voltage reaches 8.4V, the LM3420 will begin regulating by sourcing current
into R8, which controls the collector current of Q2, which in turn reduces the gate voltage of Q3 and becomes a
constant voltage regulator for charging the battery. Resistor R6 isolates the LM3420 from the common feedback
node at the emitter of Q2. If R5 and R6 are omitted, oscillations could occur during the transition from the
constant-current to the constant-voltage mode. D2 and the PNP transistor input stage of the LM10C will
disconnect the battery from the charger circuit when the input supply voltage is removed to prevent the battery
from discharging.
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Figure 33. High Efficiency Switching Regulator Constant Current/Constant Voltage 2-Cell Charger
Figure 34. Low Dropout Constant Current/Constant Voltage Li-Ion Battery Charger
A switching regulator, constant-current, constant-voltage two-cell Li-Ion battery charging circuit is shown in
Figure 33. This circuit provides much better efficiency, especially over a wide input voltage range than the linear
topologies. For a 1A charger an LM2575-ADJ. switching regulator IC is used in a standard buck topology. For
other currents, or other packages, other members of the SIMPLE SWITCHER™ buck regulator family may be
used.
Circuit operation is as follows. With a discharged battery connected to the charger, the circuit operates as a
constant current source. The constant-current portion of the charger is formed by the loop consisting of one half
of the LM358 op amp along with gain setting resistors R3 and R4, current sensing resistor R5, and the feedback
reference voltage of 1.23V. Initially the LM358's output is low causing the output of the LM2575-ADJ. to rise thus
causing some charging current to flow into the battery. When the current reaches 1A, it is sensed by resistor R5
(50 mΩ), and produces 50 mV. This 50 mV is amplified by the op-amps gain of 25 to produce 1.23V, which is
applied to the feedback pin of the LM2575-ADJ. to satisfy the feedback loop.
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Once the battery voltage reaches 8.4V, the LM3420 takes over and begins to control the feedback pin of the
LM2575-ADJ. The LM3420 now regulates the voltage across the battery, and the charger becomes a constant-
voltage charger. Loop compensation network R6 and C3 ensure stable operation of the charger circuit under
both constant-current and constant-voltage conditions. If the input supply voltage is removed, diode D2 and the
PNP input stage of the LM358 become reversed biased and disconnects the battery to ensure that the battery is
not discharged. Diode D3 reverse biases to prevent the op-amp from sinking current when the charger changes
to constant voltage mode.
The minimum supply voltage for this charger is approximately 11V, and the maximum is around 30V (limited by
the 32V maximum operating voltage of the LM358). If another op-amp is substituted for the LM358, make sure
that the input common-mode range of the op-amp extends down to ground so that it can accurately sense 50
mV. R1 is included to provide a minimum load for the switching regulator to assure that switch leakage current
will not cause the output to rise when the battery is removed.
The circuit in Figure 34 is very similar to Figure 33, except the switching regulator has been replaced with a low
dropout linear regulator, allowing the input voltage to be as low as 10V. The constant current and constant
voltage control loops are the same as the previous circuit. Diode D2 has been changed to a Schottky diode to
provide a reduction in the overall dropout voltage of this circuit, but Schottky diodes typically have higher leakage
currents than a standard silicon diode. This leakage current could discharge the battery if the input voltage is
removed for an extended period of time.
Another variation of a constant current/constant voltage switch mode charger is shown in Figure 35. The basic
feedback loops for current and voltage are similar to the previous circuits. This circuit has the current sensing
resistor, for the constant current part of the feedback loop, on the positive side of the battery, thus allowing a
common ground between the input supply and the battery. Also, the LMC7101 op-amp is available in a very
small SOT-23-5 package thus allowing a very compact pc board design. Diode D4 prevents the battery from
discharging through the charger circuitry if the input voltage is removed, although the quiescent current of the
LM3420 will still be present (approximately 85 μA).
Figure 35. High Efficiency Switching Charger
with High Side Current Sensing
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Figure 36. (Fast) Pulsed Constant Current 2-Cell Charger
A rapid charge Lithium-Ion battery charging circuit is shown in Figure 36. This configuration uses a switching
regulator to deliver the charging current in a series of constant current pulses. At the beginning of the charge
cycle (constant-current mode), this circuit performs identically to the previous LM2575 charger by charging the
battery at a constant current of 1A. As the battery voltage reaches 8.4V, this charger changes from a constant
continuous current of 1A to a 5 second pulsed 1A. This allows the total battery charge time to be reduced
considerably. This is different from the other charging circuits that switch from a constant current charge to a
constant voltage charge once the battery voltage reaches 8.4V. After charging the battery with 1A for 5 seconds,
the charge stops, and the battery voltage begins to drop. When it drops below 8.4V, the LM555 timer again starts
the timing cycle and charges the battery with 1A for another 5 seconds. This cycling continues with a constant 5
second charge time, and a variable off time. In this manner, the battery will be charged with 1A for 5 seconds,
followed by an off period (determined by the battery's state of charge), setting up a periodic 1A charge current.
The off time is determined by how long it takes the battery voltage to decrease back down to 8.4V. When the
battery first reaches 8.4V, the off time will be very short (1 ms or less), but when the battery approaches full
charge, the off time will begin increasing to tens of seconds, then minutes, and eventually hours.
The constant-current loop for this charger and the method used for programming the 1A constant current is
identical to the previous LM2575-ADJ. charger. In this circuit, a second LM3420-8.4 has its VREG increased by
approximately 400 mV (via R2), and is used to limit the output voltage of the charger to 8.8V in the event of a
bad battery connection, or the battery is removed or possibly damaged.
The LM555 timer is connected as a one-shot, and is used to provide the 5 second charging pulses. As long as
the battery voltage is less than the 8.4V, the output of IC3 will be held low, and the LM555 one-shot will never
fire (the output of the LM555 will be held high) and the one-shot will have no effect on the charger. Once the
battery voltage exceeds the 8.4V regulation voltage of IC3, the trigger pin of the LM555 is pulled high, enabling
the one shot to begin timing. The charge current will now be pulsed into the battery at a 5 second rate, with the
off time determined by the battery's state of charge. The LM555 output will go high for 5 seconds (pulling down
the collector of Q1) which allows the 1A constant-current loop to control the circuit.
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Figure 37. MOSFET Low Dropout Charger
Figure 37 shows a low dropout constant voltage charger using a MOSFET as the pass element, but this circuit
does not include current limiting. This circuit uses Q3 and a Schottky diode to isolate the battery from the
charging circuitry when the input voltage is removed, to prevent the battery from discharging. Q2 should be a
high current (0.2Ω) FET, while Q3 can be a low current (2Ω) device.
Note: Although the application circuits shown here have been built and tested, they should be
thoroughly evaluated with the same type of battery the charger will eventually be used with.
Different battery manufacturers may use a slightly different battery chemistry which may require different
charging characteristics. Always consult the battery manufacturer for information on charging
specifications and battery details, and always observe the manufacturers precautions when using their
batteries. Avoid overcharging or shorting Lithium-Ion batteries.
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REVISION HISTORY
Changes from Revision C (May 2013) to Revision D
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 19
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PACKAGE OPTION ADDENDUM
www.ti.com
1-Nov-2013
PACKAGING INFORMATION
Orderable Device
Status Package Type Package Pins Package
Eco Plan
Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
Device Marking
Samples
Drawing
Qty
1000
1000
(1)
(2)
(6)
(3)
(4/5)
LM3420AM5-8.4
NRND
ACTIVE
SOT-23
SOT-23
DBV
5
5
TBD
Call TI
CU SN
Call TI
-40 to 125
-40 to 125
D03A
D03A
LM3420AM5-8.4/NOPB
DBV
Green (RoHS
& no Sb/Br)
Level-1-260C-UNLIM
LM3420M5X-8.4/NOPB
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-40 to 125
D03B
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
1-Nov-2013
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
LM3420AM5-8.4
SOT-23
DBV
DBV
DBV
5
5
5
1000
1000
3000
178.0
178.0
178.0
8.4
8.4
8.4
3.2
3.2
3.2
3.2
3.2
3.2
1.4
1.4
1.4
4.0
4.0
4.0
8.0
8.0
8.0
Q3
Q3
Q3
LM3420AM5-8.4/NOPB SOT-23
LM3420M5X-8.4/NOPB SOT-23
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
LM3420AM5-8.4
SOT-23
SOT-23
SOT-23
DBV
DBV
DBV
5
5
5
1000
1000
3000
210.0
210.0
210.0
185.0
185.0
185.0
35.0
35.0
35.0
LM3420AM5-8.4/NOPB
LM3420M5X-8.4/NOPB
Pack Materials-Page 2
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