LINER LTC4065L Standalone 250ma li-ion battery charger in 2 x 2 dfn Datasheet

LTC4065L/LTC4065LX
Standalone 250mA Li-Ion
Battery Charger in 2 × 2 DFN
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FEATURES
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Charge Current Programmable up to 250mA with
5% Accuracy
Complete Linear Charger in 2mm × 2mm DFN
Package
C/10 Charge Current Detection Output
Timer Termination
No External MOSFET, Sense Resistor or Blocking
Diode Required
Preset 4.2V Float Voltage with 0.6% Accuracy
Constant-Current/Constant-Voltage Operation with
Thermal Feedback to Maximize Charging Rate
Without Risk of Overheating
Charge Current Monitor Output for Gas Gauging
Automatic Recharge
Charges Single Cell Li-Ion Batteries Directly from
USB Port
20µA Supply Current in Shutdown Mode
Soft-Start Limits Inrush Current
Available Without Trickle Charge (LTC4065LX)
Tiny 6-Lead (2mm × 2mm) DFN Package
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APPLICATIO S
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Charger for Li-Ion Coin Cell Batteries
Portable MP3 Players, Wireless Headsets
Bluetooth Applications
Multifunction Wristwatches
The LTC®4065L is a complete constant-current/constantvoltage linear charger for single-cell lithium-ion batteries.
Its small size and ability to accurately regulate low charge
currents make the LTC4065L especially well-suited for
portable applications using low capacity rechargeable
lithium-ion cells. Furthermore, LTC4065L is specifically
designed to work within USB power specifications.
The CHRG pin indicates when charge current has dropped
to ten percent of its programmed value (C/10). An internal
timer terminates charging according to battery manufacturer specifications.
No external sense resistor or blocking diode is required
due to the internal MOSFET architecture. Thermal feedback regulates charge current to limit the die temperature
during high power operation or high ambient temperature
conditions.
When the input supply (wall adapter or USB supply) is
removed, the LTC4065L automatically enters a low current state, dropping battery drain current to less than 1µA.
With power applied, LTC4065L can be put into shutdown
mode, reducing the supply current to less than 20µA.
The full-featured LTC4065L also includes automatic recharge, low-battery charge conditioning (trickle charging)
and soft-start (to limit inrush current).
The LTC4065L is available in a tiny 6-lead, low profile
(0.75mm) 2mm × 2mm DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6522118, 6700364.
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TYPICAL APPLICATIO
Complete Charge Cycle (180mAh Battery)
110
Standalone Li-Ion Battery Charger
100
C1
1µF
VCC
R1
510Ω
BAT
LTC4065L
+
CHRG PROG
EN
GND
R3
2k
4.2V
Li-Ion
BATTERY
4.3
90 CONSTANT
CURRENT
80
CONSTANT
VOLTAGE
60
3.9
CHRG
TRANSITION
50
40
3.7
30
CHARGE
TERMINATION
20
4065L TA01
4.1
70
3.5
VCC = 5V
RPROG = 2k
10
0
0
0.5
1
1.5 2 2.5 3
TIME (HOURS)
BATTERY VOLTAGE (V)
100mA
VIN
4.3V TO 5.5V
CHARGE CURRENT (mA)
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DESCRIPTIO
3.3
3.5
4
4.5
4065 TA02
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LTC4065L/LTC4065LX
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ABSOLUTE
RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
VCC
t < 1ms and Duty Cycle < 1% ................. – 0.3V to 7V
Steady State ........................................... – 0.3V to 6V
BAT, CHRG ................................................. –0.3V to 6V
EN, PROG ....................................... –0.3V to VCC + 0.3V
BAT Short-Circuit Duration ...........................Continuous
BAT Pin Current ................................................. 275mA
PROG Pin Current ........................................... 1.342mA
Junction Temperature (Note 6) ............................ 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 125°C
TOP VIEW
GND 1
6 PROG
CHRG 2
7
BAT 3
5 EN
4 VCC
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 60°C/W (NOTE 3)
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER
DC PART MARKING
LTC4065LEDC
LTC4065LXEDC
LCBD
LCKS
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VCC = 5V, VBAT = 3.8V, VEN = 0V unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
VCC
VCC Supply Voltage
(Note 4)
●
MIN
ICC
Quiescent VCC Supply Current
VBAT = 4.5V (Forces IBAT and IPROG = 0)
●
ICCMS
VCC Supply Current in Shutdown
VEN = 5V
●
ICCUV
VCC Supply Current in Undervoltage
Lockout
VCC < VBAT, VCC = 3.5V, VBAT = 4V
●
VFLOAT
VBAT Regulated Output Voltage
IBAT = 2mA
IBAT = 2mA, 0°C < TA < 85°C
IBAT
BAT Pin Current
RPROG = 13.3k (0.1%), Current Mode
RPROG = 1.33k (0.1%), Current Mode
IBMS
Battery Drain Current in Shutdown
Mode
VEN = VCC
IBUV
TYP
3.75
MAX
UNITS
5.5
V
120
250
µA
20
40
µA
6
11
µA
4.175
4.158
4.2
4.2
4.225
4.242
V
V
●
●
13.5
148
15.5
155
17.5
162
mA
mA
●
–1
0
1
µA
Battery Drain Current in Undervoltage VCC = 3.5V, VBAT = 4V
Lockout
●
0
1
4
µA
VUVLO
VCC Undervoltage Lockout Voltage
VCC Rising
VCC Falling
●
●
3.4
2.8
3.6
3.0
3.8
3.2
V
V
VPROG
PROG Pin Voltage
RPROG = 1.33k, IPROG = 0.75mA
RPROG = 13.3k, IPROG = 75µA
●
●
0.98
0.98
1
1
1.02
1.02
V
V
VASD
Automatic Shutdown Threshold
Voltage
(VCC – VBAT), VCC Low to High
(VCC – VBAT), VCC High to Low
60
15
80
30
100
45
mV
mV
VMSH
Manual Shutdown High Voltage
VEN Rising
VMSL
Manual Shutdown Low Voltage
VEN Falling
REN
EN Pin Input Resistance
1
0.6
●
0.9
V
V
1.5
3.3
MΩ
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LTC4065L/LTC4065LX
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VCC = 5V, VBAT = 3.8V, VEN = 0V unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
tSS
Soft-Start Time
CONDITIONS
MIN
TYP
MAX
ITRKL
Trickle Charge Current
VTRKL
Trickle Charge Threshold Voltage
VBAT Rising (Note 7)
VTRHYS
Trickle Charge Hysteresis Voltage
(Note 7)
∆VRECHRG
Recharge Battery Threshold Voltage
VFLOAT – VRECHRG, 0°C < TA < 85°C
70
100
130
mV
∆VUVCL1
∆VUVCL2
(VCC – VBAT) Undervoltage Current
Limit
IBAT = 90%, RPROG = 2k, Programmed Charge Current
IBAT = 10%, RPROG = 2k, Programmed Charge Current
150
80
190
125
300
150
mV
mV
tTIMER
Termination Timer
3
4.5
6
Hrs
VBAT = 2V, RPROG = 1.33k (0.1%) (Note 7)
●
13
15.5
18
2.7
2.9
3.05
90
●
UNITS
µs
170
mA
V
mV
●
1.5
2.25
3
Hrs
Low-Battery Trickle Charge Time
VBAT = 2.5V
●
0.75
1.125
1.5
Hrs
VCHRG
CHRG Pin Output Low Voltage
ICHRG = 5mA
●
60
105
mV
ICHRG
CHRG Pin Input Current
VBAT = 4.5V, VCHRG = 5V
●
IC/10
End of Charge Indication Current
Level
RPROG = 1.33k (Note 5)
●
TLIM
Junction Temperature in Constant
Temperature Mode
RON
Power FET “ON” Resistance
(Between VCC and BAT)
fBADBAT
DBADBAT
Recharge Time
0.08
0
1
0.095
0.11
µA
mA/mA
115
°C
1.5
Ω
Defective Battery Detection CHRG
Pulse Frequency
2
Hz
Defective Battery Detection CHRG
Pulse Frequency Duty Ratio
75
%
IBAT = 150mA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC4065L is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
rated.
Note 4: Although the LTC4065L functions properly at 3.75V input, full
charge current requires an input voltage greater than the desired final
battery voltage per the ∆VUVCL1 specification.
Note 5: IC/10 is expressed as a fraction of measured full charge current
with indicated PROG resistor.
Note 6: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 7: This parameter is not applicable to the LTC4065LX.
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LTC4065L/LTC4065LX
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TYPICAL PERFOR A CE CHARACTERISTICS
Battery Regulation (Float) Voltage
vs Battery Charge Current
4.24
VCC = 5V
TA = 25°C
RPROG = 800Ω
4.24
4.24
4.22
4.22
4.21
4.21
4.21
VFLOAT (V)
4.20
VFLOAT (V)
4.23
4.22
4.20
4.19
4.18
4.18
4.18
4.17
4.17
4.17
50
0
100
150
IBAT (mA)
200
4.16
–50
250
4.16
– 25
0
50
25
TEMPERATURE (°C)
75
4065L G01
300
300
250
200
IBAT (mA)
IBAT (mA)
200
20
150
100
100
5
50
50
4.5
5
5.5
SUPPLY VOLTAGE (V)
0
6
1
2
3
VBAT (V)
4
VCC = 5V
VBAT = 3.8V
RPROG = 800Ω
0
–50
0
4
THERMAL CONTROL
LOOP IN OPERATION
150
10
0
6
Charge Current vs Temperature
with Thermal Regulation
(Constant Current Mode)
VCC = 5V
TA = 25°C
RPROG = 800Ω
250
15
5
4.5
5.5
SUPPLY VOLTAGE (V)
4
4065L G03
Charge Current vs Battery Voltage
(LTC4065L)
RPROG = 13.3k
VBAT = 3.8V
TA = 25°C
25
100
4065L G02
Charge Current vs Supply Voltage
(Constant Current Mode)
30
TA = 25°C
IBAT = 2mA
RPROG = 800Ω
4.20
4.19
4.19
4.16
IBAT (mA)
Battery Regulation (Float) Voltage
vs Supply Voltage
4.23
4.23
VFLOAT (V)
Battery Regulation (Float) Voltage
vs Temperature
5
0
100
50
TEMPERATURE (°C)
150
4065L G06
4065L G05
4065L G04
PROG Pin Voltage vs Temperature
(Constant Current Mode)
Power FET On Resistance
vs Temperature
PROG Pin Voltage
vs Charge Current
1.02
1.2
VCC = 5V
VBAT = 3.8V
RPROG = 13.3k
2.0
VCC = 5V
TA = 25°C
RPROG = 800Ω
1.0
VCC = 4V
IBAT = 150mA
1.8
1.01
1.00
RDS (Ω)
VPROG (V)
VPROG (V)
0.8
0.6
1.6
1.4
0.4
0.99
1.2
0.2
0.98
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
4065L G07
0
0
50
100
150
IBAT (mA)
200
250
4065L G08
1.0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4065L G09
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LTC4065L/LTC4065LX
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TYPICAL PERFOR A CE CHARACTERISTICS
Manual Shutdown Threshold
Voltage vs Temperature
Undervoltage Lockout Threshold
Voltage vs Temperature
Manual Shutdown Supply Current
vs Temperature
1.0
4.00
3.75
40
0.9
30
RISE
RISE
3.25
FALL
3.00
0.8
ICCMS (µA)
VMS (V)
3.50
VCC (V)
VCC = 5V
VEN = 5V
FALL
0.7
20
10
0.6
2.75
2.50
–50
–25
50
0
25
TEMPERATURE (°C)
75
0.5
–50
100
50
25
0
TEMPERATURE (°C)
–25
30
VCC = 5V
TA = 25°C
25
1.5
100
VCC = 5V
VBAT = 2V
25
RPROG = 800Ω
RPROG = 800Ω
20
IBAT (mA)
IBAT (mA)
IEN (µA)
30
20
2.0
75
Trickle Charge Current
vs Temperature (4065L)
VBAT = 2V
TA = 25°C
3.0
2.5
0
25
50
TEMPERATURE (°C)
4065L G12
Trickle Charge Current
vs Supply Voltage (4065L)
EN Pin Current
3.5
–25
4065L G11
4065L G16
4.0
0
–50
100
75
15
10
15
10
1.0
0
5
5
0.5
RPROG = 13.3k
RPROG = 13.3k
2.5
2
3
3.5
VEN (V)
4
4.5
4
5
4.5
5
5.5
SUPPLY VOLTAGE (V)
6
CHRG Pin Output Low Voltage
vs Temperature
VCHRG (mV)
100
80
60
40
20
0
–50
2.0
VCC = 5V
0
1.5
–1
1.0
–2
–3
–4
–5
–6
–25
50
25
0
TEMPERATURE (°C)
75
100
4065L G10
–7
–50
100
Timer Accuracy vs Supply Voltage
TIMER ACCURACY (%)
VCC = 5V
ICHRG = 5mA
75
4065L G15
Timer Accuracy vs Temperature
1
TIMER ACCURACY (%)
120
50
25
0
TEMPERATURE (°C)
–25
4065L G14
4065L G13
140
0
–50
0
TA = 25°C
0.5
0
–0.5
–1.0
–1.5
–25
0
50
25
TEMPERATURE (°C)
75
100
4065L G18
–2.0
4
5
4.5
5.5
SUPPLY VOLTAGE (V)
6
4065L G19
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LTC4065L/LTC4065LX
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PI FU CTIO S
GND (Pin 1): Ground.
CHRG (Pin 2): Open-Drain Charge Status Output. The
charge status indicator pin has three states: pull-down,
pulse at 2Hz and high impedance state. This output can be
used as a logic interface or as an LED driver. When the
battery is being charged, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge current
drops to 10% of the full-scale current, the CHRG pin is
forced to a high impedance state. If the battery voltage
remains below 2.9V for one quarter of the charge time, the
battery is considered defective and the CHRG pin pulses at
a frequency of 2Hz.
BAT (Pin 3): Charge Current Output. Provides charge
current to the battery and regulates the final float voltage
to 4.2V. An internal precision resistor divider on this pin
sets the float voltage and is disconnected in shutdown
mode.
VCC (Pin 4): Positive Input Supply Voltage. This pin
provides power to the charger. VCC can range from 3.75V
to 5.5V. This pin should be bypassed with at least a 1µF
capacitor. When VCC is within 32mV of the BAT pin
voltage, the LTC4065L enters shutdown mode, dropping
IBAT to about 1µA.
EN (Pin 5): Enable Input Pin. Pulling this pin above the
manual shutdown threshold (VMS is typically 0.82V) puts
the LTC4065L in shutdown mode. In shutdown mode, the
LTC4065L has less than 20µA supply current and less than
1µA battery drain current. Enable is the default state, but
the pin should be tied to GND if unused.
PROG (Pin 6): Charge Current Program and Charge Current Monitor Pin. Connecting a 1% resistor, RPROG, to
ground programs the charge current. When charging in
constant-current mode, this pin servos to 1V. In all modes,
the voltage on this pin can be used to measure the charge
current using the following formula:
IBAT =
VPROG
• 205
RPROG
Floating the PROG pin sets the charge current to zero.
Exposed Pad (Pin 7): Ground. The Exposed Pad must be
soldered to the PCB ground to provide both electrical contact and rated thermal performance.
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LTC4065L/LTC4065LX
W
W
SI PLIFIED BLOCK DIAGRA
VCC
4
VCC
+
TDIE
D3
TA
M2
1×
EN
UVLO
–
3.6V
+
RENB
SHUTDOWN
C1
D1
D2
–
0.82V
BAT
–
0.1V
+
–
R1
CA
–
R3
+
+
1V
C/10
1.2V
MP
R4
0.1V
R2
CHRG
VA
+
PROG
3
+
MA
1.2V
REF
2
C2
M1
205×
–
5
+
–
115°C
CHARGE CONTROL
R5
2.9V
BAT
+
LOGIC
ENABLE
–
COUNTER
LOBAT
SHUTDOWN
PROG
6
GND
1
TRICKLE CHARGE DISABLED ON THE LTC4065LX
OSCILLATOR
4056L F01
RPROG
Figure 1. LTC4065L Block Diagram
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LTC4065L/LTC4065LX
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OPERATIO
The LTC4065L is a linear battery charger designed primarily for charging single cell lithium-ion batteries. Featuring
an internal P-channel power MOSFET, the charger uses a
constant-current/constant-voltage charge algorithm with
programmable current. Charge current can be programmed
up to 250mA with a final float voltage accuracy of ±0.6%.
The CHRG open-drain status output indicates if C/10 has
been reached. No blocking diode or external sense resistor
is required; thus, the basic charger circuit requires only
two external components. An internal termination timer
and trickle charge low-battery conditioning adhere to
battery manufacturer safety guidelines (Note: The
LTC4065LX does not include this trickle charge feature).
Furthermore, the LTC4065L is capable of operating from
a USB power source.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 115°C. This feature protects
the LTC4065L from excessive temperature and allows the
user to push the limits of the power handling capability of
a given circuit board without risk of damaging the LTC4065L
or external components. Another benefit of the LTC4065L
thermal limit is that charge current can be set according to
typical, not worst-case, ambient temperatures for a given
application with the assurance that the charger will automatically reduce the current in worst-case conditions.
The charge cycle begins when the following conditions are
met: the voltage at the VCC pin exceeds 3.6V and approximately 80mV above the BAT pin voltage, a program
resistor is present from the PROG pin to ground and the EN
pin is pulled below the shutdown threshold (typically
0.82V).
If the BAT pin voltage is below 2.9V, the charger goes into
trickle charge mode, charging the battery at one-tenth the
programmed charge current to bring the cell voltage up to
a safe level for charging (Note: The LTC4065LX does not
include this trickle charge feature). If the BAT pin voltage
is above 4.1V, the charger will not charge the battery as the
cell is near full capacity. Otherwise, the charger goes into
the fast charge constant-current mode.
When the BAT pin approaches the final float voltage
(4.2V), the LTC4065L enters constant-voltage mode and
the charge current begins to decrease. When the current
drops to 10% of the full-scale charge current, an internal
comparator turns off the N-channel MOSFET on the CHRG
pin and the pin assumes a high impedance state.
An internal timer sets the total charge time, tTIMER (typically 4.5 hours). When this time elapses, the charge cycle
terminates and the CHRG pin assumes a high impedance
state. To restart the charge cycle, remove the input voltage
and reapply it or momentarily force the EN pin above VMS
(typically 0.82V). The charge cycle will automatically restart if the BAT pin voltage falls below VRECHRG (typically
4.1V).
When the input voltage is not present, the battery drain
current is reduced to less than 4µA. The LTC4065L can also
be shut down by pulling the EN pin above the shutdown
threshold voltage. This reduces input quiescent current to
less than 20µA and battery drain current to less than 1µA.
Programming Charge Current
The charge current is programmed using a single resistor
from the PROG pin to ground. The battery charge current
is 205 times the current out of the PROG pin. The program
resistor and the charge current are calculated using the
following equations:
RPROG = 205 •
1V
IBAT
, IBAT =
205V
RPROG
The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage and using
the following equation:
IBAT =
VPROG
• 205
RPROG
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LTC4065L/LTC4065LX
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OPERATIO
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in undervoltage lockout
until VCC rises above 3.6V and approximately 80mV above
the BAT pin voltage. The 3.6V UVLO circuit has a built-in
hysteresis of approximately 0.6V and the automatic shutdown threshold has a built-in hysteresis of approximately
50mV. During undervoltage lockout conditions, maximum battery drain current is 4µA and maximum supply
current is 11µA.
Shutdown Mode
The LTC4065L can be disabled by pulling the EN pin above
the shutdown threshold (approximately 0.82V). In shutdown mode, the battery drain current is reduced to less
than 1µA and the supply current to about 20µA.
Timer and Recharge
The LTC4065L has an internal termination timer that
starts when an input voltage greater than the undervoltage
lockout threshold is applied to VCC, or when leaving
shutdown the battery voltage is less than the recharge
threshold.
At power-up or when exiting shutdown, if the battery
voltage is less than the recharge threshold, the charge
time is set to 4.5 hours. If the battery voltage is greater than
the recharge threshold at power-up or when exiting shutdown, the timer will not start and charging is prevented
since the battery is at or near full capacity.
Once the charge cycle terminates, the LTC4065L continuously monitors the BAT pin voltage using a comparator
with a 2ms filter time. When the average battery voltage
falls below 4.1V (which corresponds to 80% to 90%
battery capacity), a new charge cycle is initiated and a 2.25
hour timer begins. This ensures that the battery is kept at,
or near, a fully charged condition and eliminates the need
for periodic charge cycle initiations. The CHRG output
assumes a strong pull-down state during recharge cycles
until C/10 is reached when it transitions to a high
impendance state.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage is
low (below 2.9V), the charger goes into trickle charge,
reducing the charge current to 10% of the full-scale
current (Note: The LTC4065LX has full charge current at
low-battery voltage). If the low-battery voltage persists for
one quarter of the total time (1.125 hour), the battery is
assumed to be defective, the charge cycle is terminated
and the CHRG pin output pulses at a frequency of 2Hz with
a 75% duty cycle. If for any reason the battery voltage rises
above 2.9V, the charge cycle will be restarted. To restart
the charge cycle (i.e., when the defective battery is replaced with a discharged battery), simply remove the input
voltage and reapply it or temporarily pull the EN pin above
the shutdown threshold.
CHRG Status Output Pin
The charge status indicator pin has three states: pulldown, pulse at 2Hz (see Trickle Charge and Defective
Battery Detection) and high impedance. The pull-down
state indicates that the LTC4065L is in a charge cycle. A
high impedance state indicates that the charge current has
dropped below 10% of the full-scale current or the
LTC4065L is disabled. Figure 2 shows the CHRG status
under various conditions.
4065lxfa
9
LTC4065L/LTC4065LX
U
OPERATIO
Charge Current Soft-Start and Soft-Stop
The LTC4065L includes a soft-start circuit to minimize the
inrush current at the start of a charge cycle. When a charge
cycle is initiated, the charge current ramps from zero to the
full-scale current over a period of approximately 170µs.
Likewise, internal circuitry slowly ramps the charge current from full-scale to zero when the charger is shut off or
self terminates. This has the effect of minimizing the
transient current load on the power supply during start-up
and charge termination.
Constant-Current/Constant-Voltage/
Constant-Temperature
The LTC4065L use a unique architecture to charge a
battery in a constant-current, constant-voltage and constant-temperature fashion. Figure 1 shows a simplified
block diagram of the LTC4065L. Three of the amplifier
feedback loops shown control the constant-current, CA,
constant-voltage, VA, and constant-temperature, TA
modes. A fourth amplifier feedback loop, MA, is used to
increase the output impedance of the current source pair;
M1 and M2 (note that M1 is the internal P-channel power
MOSFET). It ensures that the drain current of M1 is exactly
205 times greater than the drain current of M2.
Amplifiers CA and VA are used in separate feedback loops
to force the charger into constant-current or constantvoltage mode, respectively. Diodes D1 and D2 provide
priority to either the constant-current or constant-voltage
loop, whichever is trying to reduce the charge current the
most. The output of the other amplifier saturates low
which effectively removes its loop from the system. When
in constant-current mode, CA servos the voltage at the
PROG pin to be precisely 1V. VA servos its inverting input
to an internal reference voltage when in constant-voltage
mode and the internal resistor divider, made up of R1 and
R2, ensures that the battery voltage is maintained at 4.2V.
The PROG pin voltage gives an indication of the charge
current during constant-voltage mode as discussed in
“Programming Charge Current”.
The transconductance amplifier, TA, limits the die temperature to approximately 115°C when in constant-temperature mode. Diode D3 ensures that TA does not affect
the charge current when the die temperature is below
approximately 115°C. The PROG pin voltage continues to
give an indication of the charge current.
In typical operation, the charge cycle begins in constantcurrent mode with the current delivered to the battery
equal to 205V/RPROG. If the power dissipation of the
LTC4065L results in the junction temperature approaching 115°C, the amplifier (TA) will begin decreasing the
charge current to limit the die temperature to approximately 115°C. As the battery voltage rises, the LTC4065L
either returns to constant-current mode or enters constant-voltage mode straight from constant-temperature
mode. Regardless of mode, the voltage at the PROG pin is
proportional to the current delivered to the battery.
4065lxfa
10
LTC4065L/LTC4065LX
U
OPERATIO
UVLO
ENABLE
POWER
ON
NO
UVLO MODE
NO
IS EN > SHUTDOWN
THRESHOLD?
IF VCC > 3.6V AND
VCC > VBAT + 80mV?
YES
YES
CHRG HIGH IMPEDANCE
SHUTDOWN MODE
CHRG HIGH IMPEDANCE
VBAT ≤ 2.9V
2.9V < VBAT < 4.1V
TRICKLE CHARGE MODE*
FAST CHARGE MODE
1/10 FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
1/4 CHARGE CYCLE
(1.125 HOURS)
NO
DEFECTIVE BATTERY
STANDBY MODE
NO CHARGE CURRENT
CHRG HIGH IMPEDANCE
NO
CHARGE CYCLE
(4.5 HOURS)
RECHARGE
IS VBAT < 4.1V?
IS VBAT < 2.9V?
YES
BAD BATTERY MODE
NO CHARGE CURRENT
CHRG PULSES (2Hz)
VCC < 3V
OR
EN > SHDN
THRESHOLD
VBAT > 4.1V
YES
RECHARGE MODE
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
1/2 CHARGE CYCLE
(2.25 HOURS)
4065L F02
*LTC4065L ONLY; LTC4065LX HAS FULL CHARGE CURRENT.
Figure 2. State Diagram of LTC4065L Operation
4065lxfa
11
LTC4065L/LTC4065LX
U
W
U U
APPLICATIO S I FOR ATIO
Undervoltage Charge Current Limiting (UVCL)
USB and Wall Adapter Power
The LTC4065L includes undervoltage charge (∆VUVCL1)
current limiting that prevents full charge current until the
input supply voltage reaches approximately 200mV above
the battery voltage. This feature is particularly useful if the
LTC4065L is powered from a supply with long leads (or
any relatively high output impedance).
Although the LTC4065L allows charging from a USB port,
a wall adapter can also be used to charge Li-Ion batteries.
Figure 3 shows an example of how to combine wall adapter
and USB power inputs. A P-channel MOSFET, MP1, is
used to prevent back conducting into the USB port when
a wall adapter is present and Schottky diode, D1, is used
to prevent USB power loss through the 1k pull-down
resistor.
For example, USB-powered systems tend to have highly
variable source impedances (due primarily to cable quality
and length). A transient load combined with such impedance can easily trip the UVLO threshold and turn the
charger off unless undervoltage charge current limiting is
implemented.
Stability Considerations
The LTC4065L contains two control loops: constantvoltage and constant-current. The constant-voltage loop
is stable without any compensation when a battery is
connected with low impedance leads. Excessive lead
length, however, may add enough series inductance to
require a bypass capacitor of at least 1µF from BAT to
GND. Furthermore, a 4.7µF capacitor with a 0.2Ω to 1Ω
series resistor from BAT to GND is required to keep ripple
voltage low when the battery is disconnected.
Consider a situation where the LTC4065L is operating
under normal conditions and the input supply voltage
begins to droop (e.g., an external load drags the input
supply down). If the input voltage reaches VBAT + ∆VUVCL1
(approximately 220mV above the battery voltage),
undervoltage charge current limiting will begin to reduce
the charge current in an attempt to maintain ∆VUVCL1
between the VCC input and the BAT output of the IC. The
LTC4065L will continue to operate at the reduced charge
current until the input supply voltage is increased or
voltage mode reduces the charge current further.
High value capacitors with very low ESR (especially ceramic) may reduce the constant-voltage loop phase margin. Ceramic capacitors up to 22µF may be used in parallel
with a battery, but larger ceramics should be decoupled
with 0.2Ω to 1Ω of series resistance.
5V WALL
ADAPTER
BAT
D1
USB
POWER
4
MP1
IBAT
SYSTEM
LOAD
LTC4065L
VCC
PROG
1k
3
6
+
Li-Ion
BATTERY
800Ω
4065L F03
Figure 3. Combining Wall Adapter and USB Power
4065lxfa
12
LTC4065L/LTC4065LX
U
W
U U
APPLICATIO S I FOR ATIO
battery current as shown in Figure 4. A 10K resistor has
been added between the PROG pin and the filter capacitor
to ensure stability.
In constant-current mode, the PROG pin is in the feedback
loop, not the battery. Because of the additional pole
created by the PROG pin capacitance, capacitance on this
pin must be kept to a minimum. With no additional
capacitance on the PROG pin, the charger is stable with
program resistor values as high as 25k. However, additional capacitance on this node reduces the maximum
allowed program resistor. The pole frequency at the PROG
pin should be kept above 100kHz. Therefore, if the PROG
pin is loaded with a capacitance, CPROG, the following
equation should be used to calculate the maximum resistance value for RPROG:
RPROG ≤
Power Dissipation
Due to the low charge currents, it is unlikely that the
LTC4065L will reduce charge current through thermal
feedback. Nonetheless, the LTC4065L power dissipation
can be approximated by:
PD = (VCC – VBAT) • IBAT
Where PD is the power dissipated, VCC is the input supply
voltage, VBAT is the battery voltage and IBAT is the charge
current. It is not necessary to perform any worst-case
power dissipation scenarios because the LTC4065L will
automatically reduce the charge current to maintain the
die temperature at approximately 115°C. However, the
approximate ambient temperature at which the thermal
feedback begins to protect the IC is:
1
• CPROG
2π • 105
Average, rather than instantaneous, battery current may
be of interest to the user. For example, if a switching power
supply operating in low current mode is connected in
parallel with the battery, the average current being pulled
out of the BAT pin is typically of more interest than the
instantaneous current pulses. In such a case, a simple RC
filter can be used on the PROG pin to measure the average
LTC4065L
TA = 115°C – PD • θJA
TA = 115°C – (VCC – VBAT) • IBAT • θJA
10k
PROG
GND
RPROG
CFILTER
CHARGE
CURRENT
MONITOR
CIRCUITRY
4065L F04
Figure 4. Isolating Capacitive Load on the PROG Pin and Filtering
4065lxfa
13
LTC4065L/LTC4065LX
U
W
U U
APPLICATIO S I FOR ATIO
Example: Consider an LTC4065L operating from a 5.5V
wall adapter providing 250mA to a 3V Li-Ion battery. The
ambient temperature above which the LTC4065L will
begin to reduce the 250mA charge current is approximately:
TA = 115°C – (5.5V – 3V) • (250mA) • 60°C/W
TA = 115°C – 0.625W • 60°C/W = 115°C – 37.5°C
TA = 77.5°C
Charging at such high ambient temperatures is not recommended by battery manufacturers.
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in the
Programming Charge Current section.
It is important to remember that LTC4065L applications
do not need to be designed for worst-case thermal conditions since the IC will automatically reduce power dissipation when the junction temperature reaches approximately
115°C.
Board Layout Considerations
In order to deliver maximum charge current under all
conditions, it is critical that the exposed metal pad on the
backside of the LTC4065L package is soldered to the PC
board ground. Correctly soldered to a 2500mm2 doublesided 1 oz. copper board the LTC4065L has a thermal
resistance of approximately 60°C/W. Failure to make
thermal contact between the Exposed Pad on the backside
of the package and the copper board will result in thermal
resistances far greater than 60°C/W.
VCC Bypass Capacitor
Many types of capacitors can be used for input bypassing;
however, caution must be exercised when using multilayer ceramic capacitors. Because of the self-resonant and
high Q characteristics of some types of ceramic capacitors, high voltage transients can be generated under some
start-up conditions, such as connecting the charger input
to a live power source. For more information, refer to
Application Note 88.
4065lxfa
14
LTC4065L/LTC4065LX
U
PACKAGE DESCRIPTIO
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
R = 0.115
TYP
0.56 ± 0.05
(2 SIDES)
0.675 ±0.05
2.50 ±0.05
1.15 ±0.05 0.61 ±0.05
(2 SIDES)
PACKAGE
OUTLINE
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.38 ± 0.05
4
2.00 ±0.10
(4 SIDES)
PIN 1
CHAMFER OF
EXPOSED PAD
3
0.25 ± 0.05
0.50 BSC
1.42 ±0.05
(2 SIDES)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
6
0.75 ±0.05
1
(DC6) DFN 1103
0.25 ± 0.05
0.50 BSC
1.37 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
4065lxfa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC4065L/LTC4065LX
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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LTC4054
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LTC4057
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LTC4059/LTC4059A
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LTC4061
Standalone Li-Ion Charger with Thermistor Interface
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LTC4061-4.4
Standalone Li-Ion Charger with Thermistor Interface
4.4V (Max), ±0.4% Float Voltage, Up to 1A Charge Current,
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LTC4062
Standalone Linear Li-Ion Battery Charger with
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LTC4063
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Up to 1A Charge Current, 100mA, 125mV LDO, 3mm × 3mm DFN
LTC4065/LTC4065A
Standalone Li-Ion Battery Chargers
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LTC3405/LTC3405A
300mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.7V to 6V, VOUT = 0.8V, IQ = 20µA, ISD < 1µA,
ThinSOT Package
LTC3406/LTC3406A
600mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.6V, IQ = 20µA, ISD < 1µA,
ThinSOT Package
LTC3411
1.25A (IOUT), 4MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 0.8V, IQ = 60µA, ISD < 1µA,
MS Package
LTC3440
600mA (IOUT), 2MHz, Synchronous Buck-Boost
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT = 2.5V, IQ = 25µA, ISD < 1µA,
MS Package
LTC4411/LTC4412
Low Loss PowerPathTM Controller in ThinSOT
Automatic Switching Between DC Sources, Load Sharing,
Replaces ORing Diodes
LTC4413
Dual Ideal Diode in DFN
2-Channel Ideal Diode ORing, Low Forward ON Resistance, Low Regulated
Forward Voltage, 2.5V ≤ VIN ≤ 5.5V
Power Management
ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4065lxfa
16
Linear Technology Corporation
LT 0506 REV A • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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© LINEAR TECHNOLOGY CORPORATION 2005