MICROCHIP MCP73828

M
MCP73828
Single Cell Lithium-Ion Charge Management Controller
with Charge Complete Indicator and Temperature Monitor
Features
Description
• Linear Charge Management Controller for Single
Lithium-Ion Cells
• High Accuracy Preset Voltage Regulation:
+1% (max)
• Two Preset Voltage Regulation Options:
- 4.1V - MCP73828-4.1
- 4.2V - MCP73828-4.2
• Programmable Charge Current
• Automatic Cell Preconditioning of Deeply
Depleted Cells, Minimizing Heat Dissipation
During Initial Charge Cycle
• Charge Complete Output CD10 for LED or
Microcontroller Interface
• Continuous Temperature Monitoring
• Automatic Power-Down when Input Power
Removed
• Temperature Range: -20°C to +85°C
• Packaging: 8-Pin MSOP
The MCP73828 is a linear charge management controller for use in space-limited, cost sensitive applications. The MCP73828 combines high accuracy
constant voltage, controlled current regulation, cell preconditioning, cell temperature monitoring, and charge
complete indication in a space saving 8-pin MSOP
package. The MCP73828 provides a stand-alone
charge management solution.
Applications
•
•
•
•
•
•
Single Cell Lithium-Ion Battery Chargers
Personal Data Assistants
Cellular Telephones
Hand Held Instruments
Cradle Chargers
Digital Cameras
500 mA Lithium-Ion Battery Charger
100 mΩ NDS8434
MA2Q705
10 µF
332 Ω
8
100 kΩ
1
4
7
6
VSNS VDRV
VIN
SHDN
VBAT
GND
CD10 THERM
MCP73828
Following the preconditioning phase, the MCP73828
enters the controlled current phase. The MCP73828
allows for design flexibility with a programmable charge
current set by an external sense resistor. The charge
current is ramped up, based on the cell voltage, from
the foldback current to the peak charge current established by the sense resistor. This phase is maintained
until the battery reaches the charge-regulation voltage.
Then, the MCP73828 enters the final phase, constant
voltage. The accuracy of the voltage regulation is better
than ±1% over the entire operating temperature range
and supply voltage range. The MCP73828-4.1 is preset
to a regulation voltage of 4.1V, while the MCP738284.2 is preset to 4.2V. The charge complete output,
CD10, indicates when the charge current has diminished to approximately 10% of the peak charge current
established by the sense resistor.
Typical Application Circuit
VIN
5V
The MCP73828 charges the battery in three phases:
preconditioning, controlled current, and constant voltage. If the battery voltage is below the internal low-voltage threshold, the battery is preconditioned with a
foldback current. The preconditioning phase protects
the lithium-ion cell and minimizes heat dissipation.
Thermistor
+ Single
- Lithium-Ion
Cell
The MCP73828 operates with an input voltage range
from 4.5V to 5.5V. The MCP73828 is fully specified
over the ambient temperature range of -20°C to +85°C.
Package Type
5
2
3
10 µF
MSOP
GND 2
THERM 3
CD10 4
 2002 Microchip Technology Inc.
8 VIN
SHDN 1
MCP73828
7 VSNS
6 VDRV
5 VBAT
DS21706A-page 1
SHDN
VSNS
VIN
VIN
0.3V CLAMP
CHARGE CURRENT
FOLDBACK AMPLIFIER
–
+
12 kΩ
VREF (1.2V)
CHARGE
CURRENT
AMPLIFIER
SHUTDOWN,
REFERENCE
GENERATOR
+
–
Value = 352.5KΩ For MCP73828-4.2
NOTE 1: Value = 340.5KΩ For MCP73828-4.1
37.5 kΩ
112.5 kΩ
VREF
1.1 kΩ
500 kΩ
100 kΩ
CHARGE CURRENT
CONTROL AMPLIFIER
–
+
113 mV
839 mV
VIN
25 mA
ITHERM
75 kΩ
75 kΩ
352.5 kΩ
(NOTE 1)
21 kΩ
5 kΩ
130 kΩ
140 mV
67 kΩ
VREF
VOLTAGE CONTROL
AMPLIFIER
VREF
CHARGE COMPLETE
COMPARATOR
-
+
THERMISTOR VOLTAGE
COMPARATORS
V IN
156 kΩ
CHARGE COMPLETE
AMPLIFIER
140 mV
-
+
-
+
–
–
DS21706A-page 2
+
+
THERM
GND
VBAT
VDRV
CD10
MCP73828
Functional Block Diagram
 2002 Microchip Technology Inc.
MCP73828
1.0
ELECTRICAL
CHARACTERISTICS
1.1
Maximum Ratings*
PIN FUNCTION TABLE
Pin
Name
1
SHDN
2
GND
Current at CD10 Pin ................................................ +/-30 mA
3
THERM
Cell Temperature Monitor
Current at VDRV .......................................................... +/-1 mA
4
CD10
Charge Complete Output
5
VBAT
Cell Voltage Monitor Input
ESD protection on all pins ..................................................≥ 4 kV
6
VDRV
Drive Output
*Notice: Stresses above those listed under “Maximum Ratings” may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at
those or any other conditions above those indicated in the
operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may
affect device reliability.
7
VSNS
Charge Current Sense Input
8
VIN
VIN ...................................................................... -0.3V to 6.0V
Description
Logic Shutdown
Battery Management
0V Reference
All inputs and outputs w.r.t. GND ................-0.3 to (VIN+0.3)V
Maximum Junction Temperature, TJ.............................. 150°C
Storage temperature .....................................-65°C to +150°C
Battery Management
Input Supply
DC CHARACTERISTICS: MCP73828-4.1, MCP73828-4.2
Unless otherwise specified, all limits apply for V IN = [VREG(typ)+1V], RSENSE = 500 mΩ, TA = -20°C to +85°C.
Typical values are at +25°C. Refer to Figure 1-1 for test circuit.
Sym
Min
Typ
Max
Units
Supply Voltage
Parameter
VIN
4.5
—
5.5
V
Conditions
Supply Current
IIN
—
—
0.7
265
15
560
µA
Shutdown, VSHDN = 0V
Constant Voltage Mode
Regulated Output Voltage
VREG
4.059
4.158
4.1
4.2
4.141
4.242
V
V
MCP73828-4.1 only
MCP73828-4.2 only
Line Regulation
∆VBAT
-10
—
10
mV
VIN = 4.5V to 5.5V,
IOUT = 75 mA
Load Regulation
∆VBAT
-1
+0.2
+1
mV
IOUT=10 mA to 75 mA
ILK
—
10
—
µA
VIN=Floating, VBAT =VREG
Gate Drive Current
IDRV
—
0.08
—
—
1
—
mA
mA
Sink, CV Mode
Source, CV Mode
Gate Drive Minimum Voltage
VDRV
—
1.6
—
V
Voltage Regulation (Constant Voltage Mode)
Output Reverse Leakage Current
External MOSFET Gate Drive
Current Regulation (Controlled Current Mode)
Current Sense Gain
ACS
—
100
—
dB
∆(VSNS-VDRV) / ∆VBAT
Current Limit Threshold
VCS
40
53
75
mV
(VIN-V SNS) at IOUT
K
—
0.43
—
A/A
Current Threshold
ITH
—
10
—
%IOUT(PEAK)
Low Output Voltage
VOL
—
—
400
mV
ISINK = 10 mA
Leakage Current
ILK
—
—
1
µA
ISINK=0 mA, VCD10=5.5V
Input High Voltage Level
VIH
40
—
—
%VIN
Input Low Voltage Level
VIL
—
—
25
%VIN
Input Leakage Current
ILK
—
—
1
µA
Foldback Current Scale Factor
Charge Complete Indicator - CD10
Shutdown Input - SHDN
 2002 Microchip Technology Inc.
VSHDN = 0V to 5.5V
DS21706A-page 3
MCP73828
Unless otherwise specified, all limits apply for V IN = [VREG(typ)+1V], RSENSE = 500 mΩ, TA = -20°C to +85°C.
Typical values are at +25°C. Refer to Figure 1-1 for test circuit.
Parameter
Sym
Min
Typ
Max
Units
ITHERM
22.5
25.0
27.5
µA
VTH
—
—
113
839
—
—
mV
Conditions
Temperature Monitor - THERM
Thermistor Bias Current
THERM Threshold Voltages
Lower Threshold Voltage
Upper Threshold Voltage
TEMPERATURE SPECIFICATIONS
Unless otherwise specified, all limits apply for V IN = 4.5V-5.5V
Parameters
Sym
Min
Typ
Max
Units
Specified Temperature Range
TA
-20
—
+85
°C
Operating Temperature Range
TA
-40
—
+125
°C
Storage Temperature Range
TA
-65
—
+150
°C
θJA
—
206
—
°C/W
Conditions
Temperature Ranges
Package Thermal Resistance
Thermal Resistance, 8L-MSOP
VIN = 5.1V
NDS8434
RSENSE
(MCP73828-4.1)
Single Layer SEMI
G42-88 Standard
Board, Natural Convection
IOUT
VIN = 5.2V
(MCP73828-4.2)
22 µF
7
VSNS
8
100 kΩ
100 kΩ
1
4
VOUT
6
VIN
VDRV
VBAT
SHDN
CD10
GND
THERM
5
22 µF
2
3
10 kΩ
MCP73828
FIGURE 1-1:
MCP73828 Test Circuit.
DS21706A-page 4
 2002 Microchip Technology Inc.
MCP73828
2.0
TYPICAL PERFORMANCE CHARACTERISTICS
Note:
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
Note: Unless otherwise indicated, IOUT= 10 mA, Constant Voltage Mode, TA=25°C. Refer to Figure 1-1 for test circuit.
4.205
350
4.204
325
Supply Current (µA)
Output Voltage (V)
4.203
4.202
4.201
4.200
4.199
4.198
4.197
300
275
250
225
4.196
4.195
200
0
200
400
600
800
1000
0
200
400
Output Current (mA)
FIGURE 2-1: Output Voltage vs. Output Current
(MCP73828-4.2).
FIGURE 2-4:
800
1000
Supply Current vs. Output Current.
350
4.205
IOUT = 1000 mA
IOUT = 1000 mA
4.204
325
Supply Current (µA)
4.203
Output Voltage (V)
600
Output Current (mA)
4.202
4.201
4.200
4.199
4.198
4.197
300
275
250
225
4.196
4.195
200
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
4.5
5.5
4.6
4.7
4.8
Input Voltage (V)
FIGURE 2-2: Output Voltage vs. Input Voltage
(MCP73828-4.2).
4.205
FIGURE 2-5:
5.0
5.1
5.2
5.3
5.4
5.5
Supply Current vs. Input Voltage.
350
IOUT = 10 mA
4.204
IOUT = 10 mA
325
Supply Current (µA)
4.203
Output Voltage (V)
4.9
Input Voltage (V)
4.202
4.201
4.200
4.199
4.198
4.197
300
275
250
225
4.196
4.195
200
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
5.5
4.5
4.6
Input Voltage (V)
FIGURE 2-3: Output Voltage vs. Input Voltage
(MCP73828-4.2).
 2002 Microchip Technology Inc.
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
5.5
Input Voltage (V)
FIGURE 2-6:
Supply Current vs. Input Voltage.
DS21706A-page 5
MCP73828
16
350
VIN = Floating
VSHDN = V OUT
14
o
85 C
12
o
25 C
10
o
-20 C
8
6
4
325
Supply Current (µA)
Ouput Reverse Leakage Current ( µA)
Note: Unless otherwise indicated, IOUT= 10 mA, Constant Voltage Mode, TA=25°C. Refer to Figure 1-1 for test circuit.
300
275
250
225
2
200
0
2.0
2.5
3.0
3.5
4.0
-20
4.5
-10
0
10
20
70
80
4.204
o
o
25 C
1.0
o
-20 C
0.8
0.6
0.4
Output Voltage (V)
Output Reverse Leakage Current ( µA)
60
FIGURE 2-10: Supply Current vs. Temperature.
85 C
1.2
4.202
4.200
4.198
4.196
4.194
4.192
0.2
4.190
0.0
2.0
2.5
3.0
3.5
4.0
-20
4.5
-10
0
10
20
30
40
50
60
70
80
o
Temperature ( C)
Output Voltage (V)
FIGURE 2-8: Output Reverse Leakage Current vs.
Output Voltage.
FIGURE 2-11: Output
(MCP73828-4.2).
4.500
4.5
4.000
4.0
3.500
3.5
Output Voltage (V)
Output Voltage (V)
50
4.206
VIN = Floating
VSHDN = GND
1.4
40
o
FIGURE 2-7: Output Reverse Leakage Current vs.
Output Voltage.
1.6
30
Temperature ( C)
Output Voltage (V)
3.000
2.500
2.000
1.500
1.000
Voltage
vs.
Temperature
3.0
2.5
2.0
1.5
1.0
0.500
0
20
40
60
80
Output Current (mA)
FIGURE 2-9:
Current Limit Foldback.
DS21706A-page 6
100
120
Power Down
Power Up
0.5
0.000
0.0
0
1
2
3
4
5
64
73
8
2
9
1
10
0
Input Voltage (V)
FIGURE 2-12: Power-Up / Power-Down.
 2002 Microchip Technology Inc.
MCP73828
Note: Unless otherwise indicated, IOUT= 10 mA, Constant Voltage Mode, TA=25°C. Refer to Figure 1-1 for test circuit.
FIGURE 2-13: Line Transient Response.
FIGURE 2-15: Load Transient Response.
FIGURE 2-14: Line Transient Response.
FIGURE 2-16: Load Transient Response.
 2002 Microchip Technology Inc.
DS21706A-page 7
MCP73828
3.0
PIN DESCRIPTION
The descriptions of the pins are listed in Table 3-1.
Pin
Name
1
SHDN
2
GND
3
THERM
Cell Temperature Monitor
4
CD10
Charge Complete Output
5
VBAT
Cell Voltage Monitor Input
6
VDRV
Drive Output
7
VSNS
Charge Current Sense Input
8
VIN
TABLE 3-1:
3.1
Description
Logic Shutdown
Battery Management
0V Reference
Battery Management
Input Supply
3.6
Drive Output (VDRV)
Direct output drive of an external P-channel MOSFET
pass transistor for current and voltage regulation.
3.7
Charge Current Sense Input VSNS)
Charge current is sensed via the voltage developed
across an external precision sense resistor. The sense
resistor must be placed between the supply voltage
(VIN) and the source of the external pass transistor. A
50 mΩ sense resistor produces a fast charge current of
1 A, typically.
3.8
Battery Management Input Supply
(VIN)
A supply voltage of 4.5V to 5.5V is recommended.
Bypass to GND with a minimum of 10 µF.
Pin Function Table.
Logic Shutdown (SHDN)
Input to force charge termination, initiate charge, or initiate recharge.
3.2
Battery Management 0V Reference
(GND)
Connect to negative terminal of battery.
3.3
Cell Temperature Monitor (THERM)
Charging is inhibited when the input is outside the
upper and lower threshold limits. Connection of a
10 kΩ resistor between THERM and GND disables the
function when cell temperature monitoring is not
required.
3.4
Charge Complete Output (CD10)
Open-drain drive for connection to an LED for charge
complete indication. Alternatively, a pull-up resistor can
be applied for interfacing to a microcontroller. A low
impedance state indicates charging. A high impedance
indicates that the charge current has diminished below
10% of the peak charge current.
3.5
Cell Voltage Monitor Input (VBAT)
Voltage sense input. Connect to positive terminal of
battery. Bypass to GND with a minimum of 10 µF to
ensure loop stability when the battery is disconnected.
A precision internal resistor divider regulates the final
voltage on this pin to VREG.
DS21706A-page 8
 2002 Microchip Technology Inc.
MCP73828
4.0
DEVICE OVERVIEW
The MCP73828 is a linear charge management controller. Refer to the functional block diagram on page 2
and the typical application circuit, Figure 6-1.
4.1
Charge Qualification and
Preconditioning
Upon insertion of a battery or application of an external
supply, the MCP73828 automatically performs a series
of safety checks to qualify the charge. The SHDN pin
must be above the logic high level, and the cell temperature monitor must be within the upper and lower
threshold limits. The qualification parameters are continuously monitored. Deviation beyond the limits, automatically suspends the charge cycle.
After the qualification parameters have been met, the
MCP73828 initiates a charge cycle. The charge complete output, CD10, is pulled low throughout the preconditioning and controlled current phases (see
Table 5-1 for charge complete outputs). If the cell voltage is below the preconditioning threshold, 2.4V typically, the MCP73828 preconditions the cell with a
scaled back current. The preconditioning current is set
to approximately 43% of the fast charge peak current.
The preconditioning safely replenishes deeply
depleted cells and minimizes heat dissipation in the
external pass transistor during the initial charge cycle.
4.2
4.3
Constant Voltage Regulation
When the cell voltage reaches the regulation voltage,
VREG, constant voltage regulation begins. The
MCP73828 monitors the cell voltage at the VOUT pin.
This input is tied directly to the positive terminal of the
battery. The MCP73828 is offered in two fixed-voltage
versions for battery packs with either coke or graphite
anodes:
4.1V
(MCP73828-4.1)
and
4.2V
(MCP73828-4.2).
4.4
Charge Cycle Completion
The charge cycle can be terminated by a host microcontroller when the charge current has diminished
below approximately 10% of the peak output voltage
level. The charge complete output will go to a high
impedance state signaling when the charge can be terminated. The charge is terminated by pulling the shutdown pin, SHDN, to a logic Low level.
Controlled Current Regulation - Fast
Charge
Preconditioning ends and fast charging begins when
the cell voltage exceeds the preconditioning threshold.
Fast charge utilizes a foldback current scheme based
on the voltage at the VSNS input developed by the drop
across an external sense resistor, RSENSE, and the output voltage, VBAT. Fast charge continues until the cell
voltage reaches the regulation voltage, VREG.
 2002 Microchip Technology Inc.
DS21706A-page 9
MCP73828
5.0
DETAILED DESCRIPTION
Refer to the typical application circuit, Figure 6-1.
5.1
Analog Circuitry
5.1.1
CELL TEMPERATURE MONITOR (THERM)
The cell temperature monitor, THERM, input is used to
inhibit charging when the battery temperature exceeds
a predetermined temperature range. This temperature
range is programmed externally with either a single
Thermistor or a resistor/Thermistor network. An example of this type of network is illustrated in Figure 6-1.
The MCP73828 internally generates a current source
out of the THERM pin (shown in the Functional Block
Diagram). The nominal value of the current source
(ITHERM) is 25 µA. This current flows through the thermistor network to ground. The factory programmed
voltage range of the THERM input (VTH) is 113 mV
(typ) to 839 mV (typ). Dependent on the type of Thermistor used and the resistive network, the temperature
trip points can be controlled. If the THERM pin is lower
that 113 mV or higher than 839 mV the device will shutdown operation. This condition can be corrected by
bringing the THERM pin back between these threshold
voltages.
As an application example, if a 10 kΩ NTC Thermistor
with a sensitivity index (b) of 3982 is connected from
THERM to ground, the operational temperature range
is from –0.5°C to 44.2°C. See Section 6.1.1.6 for more
details concerning using the resistive network.
Alternatively, a positive temperature coefficient, PTC,
thermistor can be utilized. Connect the thermistor from
the THERM input to GND. If temperature monitoring is
not required, replace the thermistor with a standard
10 kΩ resistor.
5.1.2
CELL VOLTAGE MONITOR INPUT (VBAT)
The MCP73828 monitors the cell voltage at the VBAT
pin. This input is tied directly to the positive terminal of
the battery. The MCP73828 is offered in two fixed-voltage versions for single cells with either coke or graphite
anodes:
4.1V
(MCP73828-4.1)
and
4.2V
(MCP73828-4.2).
5.1.3
GATE DRIVE OUTPUT (V DRV)
The MCP73828 controls the gate drive to an external
P-channel MOSFET, Q1. The P-channel MOSFET is
controlled in the linear region, regulating current and
voltage supplied to the cell. The drive output is automatically turned off when the input supply falls below
the voltage sensed on the VBAT input.
CURRENT SENSE INPUT (VSNS)
5.1.4
Fast charge current regulation is maintained by the
voltage drop developed across an external sense resistor, RSENSE, applied to the VSNS input pin. The following formula calculates the value for R SENSE:
V CS
R SENSE = -----------I O UT
Where:
VCS is the current limit threshold.
IOUT is the desired peak fast charge current in
amps. The preconditioning current is scaled to
approximately 43% of IOUT.
5.1.5
SUPPLY VOLTAGE (VIN)
The V IN input is the input supply to the MCP73828. The
MCP73828 automatically enters a power-down mode if
the voltage on the VIN input falls below the voltage on
the VBAT pin. This feature prevents draining the battery
pack when the VIN supply is not present.
5.2
Digital Circuitry
5.2.1
SHUTDOWN INPUT (SHDN)
The shutdown input pin, SHDN, can be used to terminate a charge anytime during the charge cycle, initiate
a charge cycle, or initiate a recharge cycle.
Applying a logic High input signal to the SHDN pin, or
tying it to the input source, enables the device. Applying a logic Low input signal disables the device and terminates a charge cycle. In shutdown mode, the
device’s supply current is reduced to 0.7 µA, typically.
5.2.2
CHARGE COMPLETE OUTPUT (CD10)
A charge complete indicator, CD10, provides information on the state of charge. The open-drain output can
be used to illuminate an external LED. Optionally, a
pull-up resistor can be used on the output for communication with a microcontroller. Table 5-1 summarizes
the state of this output during a charge cycle.
Charge Cycle State
Qualification
OFF
Preconditioning
ON
Controlled Current Fast Charge
ON
Constant Voltage
ON
Charge Complete
OFF
Temperature Monitor Invalid
OFF
Disabled - Sleep mode
OFF
Battery Disconnected
OFF
TABLE 5-1:
DS21706A-page 10
Mode
Charge Complete Output.
 2002 Microchip Technology Inc.
MCP73828
6.0
APPLICATIONS
lowed by constant voltage. Figure 6-1 depicts a typical
stand-alone application circuit and Figure 6-2 depicts
the accompanying charge profile.
The MCP73828 is designed to operate in conjunction
with a host microcontroller or in stand-alone applications. The MCP73828 provides the preferred charge
algorithm for Lithium-Ion cells, controlled current fol-
Q1
RSENSE NDS8434
MA2Q705
IOUT
PACK+
22 kΩ
10 µF
100 mΩ
332 Ω
VOLTAGE
REGULATED
WALL CUBE
SHDN
GND
100 kΩ
RS
1
2
THERM 3
CD10 4
8
MCP73828
7
6
5
10 µF
VIN
VSNS
+
VDRV
-
VBAT
RP
PACK-
RTHERMISTOR
TEMP
SINGLE CELL
LITHIUM-ION
BATTERY PACK
FIGURE 6-1:
Typical Application Circuit.
PRECONDITIONING
PHASE
REGULATION
VOLTAGE
(VREG)
CONTROLLED CURRENT
PHASE
CONSTANT VOLTAGE
PHASE
CHARGE
VOLTAGE
REGULATION
CURRENT
(IOUT(PEAK))
TRANSITION
THRESHOLD
PRECONDITION
CURRENT
CHARGE COMPLETE
CURRENT
(10% IOUT(PEAK))
CHARGE
CURRENT
5V
CD10 - CHARGE
COMPLETE OUTPUT
0V
FIGURE 6-2:
Typical Charge Profile.
 2002 Microchip Technology Inc.
DS21706A-page 11
MCP73828
6.1
Application Circuit Design
Due to the low efficiency of linear charging, the most
important factors are thermal design and cost, which
are a direct function of the input voltage, output current
and thermal impedance between the external P-channel pass transistor, Q1, and the ambient cooling air.
The worst-case situation is when the output is shorted.
In this situation, the P-channel pass transistor has to
dissipate the maximum power. A trade-off must be
made between the charge current, cost and thermal
requirements of the charger.
6.1.1
EXTERNAL PASS TRANSISTOR
The external P-channel MOSFET is determined by the
gate to source threshold voltage, input voltage, output
voltage, and peak fast charge current. The selected Pchannel MOSFET must satisfy the thermal and electrical design requirements.
Thermal Considerations
The worst case power dissipation in the external pass
transistor occurs when the input voltage is at the maximum and the output is shorted. In this case, the power
dissipation is:
COMPONENT SELECTION
Selection of the external components in Figure 6-1 is
crucial to the integrity and reliability of the charging system. The following discussion is intended as a guide for
the component selection process.
6.1.1.1
6.1.1.2
PowerDissipation = V INMAX × I OU T × K
Where:
VINMAX is the maximum input voltage
SENSE RESISTOR
IOUT is the maximum peak fast charge current
The preferred fast charge current for Lithium-Ion cells
is at the 1C rate with an absolute maximum current at
the 2C rate. For example, a 500 mAH battery pack has
a preferred fast charge current of 500 mA. Charging at
this rate provides the shortest charge cycle times without degradation to the battery pack performance or life.
The current sense resistor, RSENSE, is calculated by:
V CS
R SENSE = -----------I O UT
Where:
VCS is the current limit threshold voltage
IOUT is the desired fast charge current
For the 500 mAH battery pack example, a standard
value 100 mΩ, 1% resistor provides a typical peak fast
charge current of 530 mA and a maximum peak fast
charge current of 758 mA. Worst case power dissipation in the sense resistor is:
2
PowerDissipation = 100mΩ × 758mA = 57.5mW
A Panasonic ERJ-L1WKF100U 100 mΩ, 1%, 1 W
resistor is more than sufficient for this application.
A larger value sense resistor will decrease the peak
fast charge current and power dissipation in both the
sense resistor and external pass transistor, but will
increase charge cycle times. Design trade-offs must be
considered to minimize space while maintaining the
desired performance.
K is the foldback current scale factor
Power dissipation with a 5V, +/-10% input voltage
source, 100 mΩ, 1% sense resistor, and a scale factor
of 0.43 is:
PowerDissipation = 5.5V × 758mA × 0.43 = 1.8W
Utilizing a Fairchild NDS8434 or an International Rectifier IRF7404 mounted on a 1in2 pad of 2 oz. copper, the
junction temperature rise is 90°C, approximately. This
would allow for a maximum operating ambient temperature of 60°C.
By increasing the size of the copper pad, a higher
ambient temperature can be realized or a lower value
sense resistor could be utilized.
Alternatively, different package options can be utilized
for more or less power dissipation. Again, design tradeoffs should be considered to minimize size while maintaining the desired performance.
Electrical Considerations
The gate to source threshold voltage and RDSON of the
external P-channel MOSFET must be considered in the
design phase.
The worst case, VGS provided by the controller occurs
when the input voltage is at the minimum and the
charge current is at the maximum. The worst case, VGS
is:
V GS = V DRVMAX – ( V INMIN – I OUT × R SENSE )
Where:
VDRVMAX is the maximum sink voltage at the VDRV
output
DS21706A-page 12
 2002 Microchip Technology Inc.
MCP73828
VINMIN is the minimum input voltage source
IOUT is the maximum peak fast charge current
R SENSE is the sense resistor
Worst case, VGS with a 5V, +/-10% input voltage
source, 100 mΩ, 1% sense resistor, and a maximum
sink voltage of 1.6V is:
V GS = 1.6V – ( 4.5V – 758mA × 99mΩ ) = – 2.8 V
At this worst case VGS, the RDSON of the MOSFET
must be low enough as to not impede the performance
of the charging system. The maximum allowable
RDSON at the worst case VGS is:
V INMIN – I PEAK × R SENSE – V BATMAX
R D SON = ---------------------------------------------------------------------------------------------I OU T
R DSON
4.5V – 758mA × 99mΩ – 4.242V
= -------------------------------------------------------------------------------- = 242mΩ
758mA
The Fairchild NDS8434 and International Rectifier
IRF7404 both satisfy these requirements.
6.1.1.3
EXTERNAL CAPACITORS
The MCP73828 is stable with or without a battery load.
In order to maintain good AC stability in the constant
voltage mode, a minimum capacitance of 10 µF is recommended to bypass the V BAT pin to GND. This capacitance provides compensation when there is no battery
load. In addition, the battery and interconnections
appear inductive at high frequencies. These elements
are in the control feedback loop during constant voltage
mode. Therefore, the bypass capacitance may be necessary to compensate for the inductive nature of the
battery pack.
Virtually any good quality output filter capacitor can be
used, independent of the capacitor’s minimum ESR
(Effective Series Resistance) value. The actual value of
the capacitor and its associated ESR depends on the
forward trans conductance, gm, and capacitance of the
external pass transistor. A 10 µF tantalum or aluminum
electrolytic capacitor at the output is usually sufficient
to ensure stability for up to a 1 A output current.
6.1.1.4
REVERSE BLOCKING PROTECTION
The optional reverse blocking protection diode
depicted in Figure 6-1 provides protection from a
faulted or shorted input or from a reversed polarity input
source. Without the protection diode, a faulted or
shorted input would discharge the battery pack through
the body diode of the external pass transistor.
 2002 Microchip Technology Inc.
If a reverse protection diode is incorporated in the
design, it should be chosen to handle the peak fast
charge current continuously at the maximum ambient
temperature. In addition, the reverse leakage current of
the diode should be kept as small as possible.
6.1.1.5
SHUTDOWN INTERFACE
In the stand-alone configuration, the shutdown pin is
generally tied to the input voltage. The MCP73828 will
automatically enter a low power mode when the input
voltage is less than the output voltage reducing the battery drain current to 10 µA, typically.
By connecting the shutdown pin as depicted in
Figure 6-1, the battery drain current may be further
reduced. In this application, the battery drain current
becomes a function of the reverse leakage current of
the reverse protection diode.
6.1.1.6
CELL TEMPERATURE MONITOR
As discussed in Section 5.1.1, the MCP73828 can
monitor a temperature range for –0.5°C to 44.2°C. This
temperature range can be expanded or shifted by placing fixed value resistors in series/parallel combinations
with the thermistor (see Figure 6-1). Given that the
nominal output current of the THERM pin is 25 µA, the
resistor values must satisfy the following equations:
R P × R TH ERMISTO R – H
R S + -------------------------------------------------------- = 4520Ω ( typ )
R P + R THERMISTOR – H
R P × R THERMISTOR – C
R S + -------------------------------------------------------- = 33560Ω ( typ )
R P + R THER MISTOR – C
Where:
RS is the fixed series resistance
RP is the fixed parallel resistance
RTHERMISTOR-H is the NTC thermistor resistance
at the upper temperature of interest
RTHERMISTOR-C is the NTC thermistor resistance
at the lower temperature of interest.
For example, by utilizing a 931 Ω resistor in series with
the typical NTC thermistor described previously, the
monitored temperature window will shift to 0°C to
+50°C, typically. Again, with the same thermistor, a
1 kΩ series resistor and a 140 kΩ parallel resistor will
produce a monitored window of -5°C to +50°C, typically.
DS21706A-page 13
MCP73828
6.1.1.7
CHARGE COMPLETE INTERFACE
The charge complete indicator, CD10, can be utilized to
illuminate an LED when the MCP73828 is charging the
battery. When the MCP73828 is in constant voltage
mode and the charge current has diminished below
10% of IOUT(PEAK), the CD10 pin will transition to a high
impedance state. A current limit resistor should be
used in series with the LED to establish a nominal LED
bias current of 10 mA. The maximum allowable sink
current of the CD10 pin is 30 mA.
6.2
PCB Layout Issues
For optimum voltage regulation, place the battery pack
as close as possible to the device’s V OUT and GND
pins. It is recommended to minimize voltage drops
along the high current carrying PCB traces.
If the PCB layout is used as a heatsink, adding many
vias around the external pass transistor can help conduct more heat to the back-plane of the PCB, thus
reducing the maximum junction temperature.
DS21706A-page 14
 2002 Microchip Technology Inc.
MCP73828
7.0
PACKAGING INFORMATION
7.1
Package Marking Information
Example:
8-Lead MSOP
XXXXXX
738281
YWWNNN
YWWNNN
Legend:
Part Number
Code
MCP73828-4.1VUA
738281
MCP73828-4.2VUA
738282
XX...X Part Number code + temperature range + voltage (two letter code)*
Y
Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
Note:
In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line thus limiting the number of available characters for customer specific information.
* Standard OTP marking consists of Microchip part number, year code, week code, and traceability code.
 2002 Microchip Technology Inc.
DS21706A-page 15
MCP73828
8-Lead Plastic Micro Small Outline Package (MSOP)
E
E1
D
2
B
n
1
α
c
φ
(F)
L
β
Units
Number of Pins
Pitch
Dimension Limits
n
p
Overall Height
NOM
MAX
8
0.65
.026
A
.044
.030
Standoff
A1
.002
E
.184
Molded Package Width
MIN
8
A2
Overall Width
MAX
NOM
Molded Package Thickness
§
MILLIMETERS*
INCHES
MIN
.034
1.18
.038
0.76
.006
0.05
.193
.200
0.86
0.97
4.67
4.90
.5.08
0.15
E1
.114
.118
.122
2.90
3.00
3.10
Overall Length
D
.114
.118
.122
2.90
3.00
3.10
Foot Length
L
.016
.022
.028
0.40
0.55
0.70
Footprint (Reference)
.035
.037
.039
0.90
0.95
1.00
Foot Angle
F
φ
6
0
Lead Thickness
c
.004
.006
.008
0.10
0.15
0.20
Lead Width
B
α
.010
.012
.016
0.25
0.30
0.40
Mold Draft Angle Top
Mold Draft Angle Bottom
β
0
6
7
7
7
7
*Controlling Parameter
§ Significant Characteristic
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not
exceed. 010” (0.254mm) per side.
Drawing No. C04-111
DS21706A-page 16
 2002 Microchip Technology Inc.
MCP73828
ON-LINE SUPPORT
Microchip provides on-line support on the Microchip
World Wide Web (WWW) site.
The web site is used by Microchip as a means to make
files and information easily available to customers. To
view the site, the user must have access to the Internet
and a web browser, such as Netscape or Microsoft
Explorer. Files are also available for FTP download
from our FTP site.
Connecting to the Microchip Internet Web Site
Systems Information and Upgrade Hot Line
The Systems Information and Upgrade Line provides
system users a listing of the latest versions of all of
Microchip's development systems software products.
Plus, this line provides information on how customers
can receive any currently available upgrade kits.The
Hot Line Numbers are:
1-800-755-2345 for U.S. and most of Canada, and
1-480-792-7302 for the rest of the world.
013001
The Microchip web site is available by using your
favorite Internet browser to attach to:
www.microchip.com
The file transfer site is available by using an FTP service to connect to:
ftp://ftp.microchip.com
The web site and file transfer site provide a variety of
services. Users may download files for the latest
Development Tools, Data Sheets, Application Notes,
User's Guides, Articles and Sample Programs. A variety of Microchip specific business information is also
available, including listings of Microchip sales offices,
distributors and factory representatives. Other data
available for consideration is:
• Latest Microchip Press Releases
• Technical Support Section with Frequently Asked
Questions
• Design Tips
• Device Errata
• Job Postings
• Microchip Consultant Program Member Listing
• Links to other useful web sites related to
Microchip Products
• Conferences for products, Development Systems,
technical information and more
• Listing of seminars and events
 2002 Microchip Technology Inc.
DS21706A-page 17
MCP73828
READER RESPONSE
It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip product. If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation
can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150.
Please list the following information, and use this outline to provide us with your comments about this Data Sheet.
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Application (optional):
Would you like a reply?
Device: MCP73828
Y
N
Literature Number: DS21706A
Questions:
1. What are the best features of this document?
2. How does this document meet your hardware and software development needs?
3. Do you find the organization of this data sheet easy to follow? If not, why?
4. What additions to the data sheet do you think would enhance the structure and subject?
5. What deletions from the data sheet could be made without affecting the overall usefulness?
6. Is there any incorrect or misleading information (what and where)?
7. How would you improve this document?
8. How would you improve our software, systems, and silicon products?
DS21706A-page 18
 2002 Microchip Technology Inc.
MCP73828
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO.
-X.X
X
XX
Device
Output
Voltage
Temperature
Range
Package
Device:
MCP73828: Linear Charge Management Controller
Output Voltage:
Examples:
a)
MCP73828-4.1VUA: Linear Charge Manage-
b)
MCP73828-4.2VUA: Linear Charge Manage-
ment Controller, 4.1V
ment Controller, 4.2V
c)
MCP73828-4.2VUATR: Linear Charge Management Controller, 4.2V, in tape and reel
4.1 = 4.1V
4.2 = 4.2V
Temperature Range:
V
=
-20°C to +85°C
Package:
UA = Plastic Micro Small Outline (MSOP), 8-lead
Sales and Support
Data Sheets
Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following:
1.
2.
3.
Your local Microchip sales office
The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277
The Microchip Worldwide Site (www.microchip.com)
Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using.
New Customer Notification System
Register on our web site (www.microchip.com/cn) to receive the most current information on our products.
 2002 Microchip Technology Inc.
DS21706A-page19
MCP73828
NOTES:
DS21706A-page 20
 2002 Microchip Technology Inc.
MCP73828
NOTES:
 2002 Microchip Technology Inc.
DS21706A-page21
MCP73828
NOTES:
DS21706A-page 22
 2002 Microchip Technology Inc.
Information contained in this publication regarding device
applications and the like is intended through suggestion only
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
No representation or warranty is given and no liability is
assumed by Microchip Technology Incorporated with respect
to the accuracy or use of such information, or infringement of
patents or other intellectual property rights arising from such
use or otherwise. Use of Microchip’s products as critical components in life support systems is not authorized except with
express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, FilterLab,
KEELOQ, MPLAB, PIC, PICmicro, PICMASTER, PICSTART,
PRO MATE, SEEVAL and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A. and other countries.
dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,
In-Circuit Serial Programming, ICSP, ICEPIC, microID,
microPort, Migratable Memory, MPASM, MPLIB, MPLINK,
MPSIM, MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select
Mode and Total Endurance are trademarks of Microchip
Technology Incorporated in the U.S.A.
Serialized Quick Term Programming (SQTP) is a service mark
of Microchip Technology Incorporated in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2002, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and Tempe, Arizona in July 1999. The
Company’s quality system processes and
procedures are QS-9000 compliant for its
PICmicro ® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs and microperipheral
products. In addition, Microchip’s quality
system for the design and manufacture of
development systems is ISO 9001 certified.
 2002 Microchip Technology Inc.
DS21706A - page 23
M
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03/01/02
*DS21706A*
DS21706A-page 24
 2002 Microchip Technology Inc.