LINER LTC4065LXEDC Standalone 750ma li-ion battery charger in 2 x 2 dfn Datasheet

LTC4065/LTC4065A
Standalone 750mA Li-Ion
Battery Charger in 2 × 2 DFN
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FEATURES
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DESCRIPTIO
Complete Linear Charger in 2mm × 2mm DFN
Package
C/10 Charge Current Detection Output
Timer Termination
Charge Current Programmable up to 750mA with
5% Accuracy
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
ACPR Pin Indicates Presence of Input Supply
(LTC4065A Only)
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
Tiny 6-Lead (2mm × 2mm) DFN Package
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APPLICATIO S
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Wireless PDAs
Cellular Phones
Portable Electronics
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
The LTC®4065 is a complete constant-current/constantvoltage linear charger for single-cell lithium-ion batteries.
Its 2mm × 2mm DFN package and low external component
count make the LTC4065 especially well-suited for portable applications. Furthermore, LTC4065 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 LTC4065 automatically enters a low current
state, dropping battery drain current to less than 1µA. With
power applied, LTC4065 can be put into shutdown mode,
reducing the supply current to less than 20µA.
The full-featured LTC4065 also includes automatic recharge, low-battery charge conditioning (trickle charging), soft-start (to limit inrush current) and an open-drain
status pin to indicate the presence of an adequate input
voltage (LTC4065A only).
The LTC4065 is available in a tiny 6-lead, low profile
(0.75mm) 2mm × 2mm DFN package.
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TYPICAL APPLICATIO
Standalone Li-Ion Battery Charger
500mA
VIN
4.3V TO 5.5V
C1
1µF
R2*
1Ω
VCC
R1
510Ω
BAT
LTC4065
CHRG PROG
EN
GND
+
R3
2k
4.2V
Li-Ion
BATTERY
4065 TA01
*SERIES 1Ω RESISTOR ONLY NEEDED FOR INDUCTIVE INPUT SUPPLIES
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LTC4065/LTC4065A
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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 (LTC4065), ACPR (LTC4065A) .. –0.3V to VCC + 0.3V
PROG.............................................. –0.3V to VCC + 0.3V
BAT Short-Circuit Duration ...........................Continuous
BAT Pin Current ................................................. 800mA
PROG Pin Current ............................................... 800µA
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/ACPR*
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
*EN PIN 5 ON LTC4065EDC, ACPR PIN 5 ON LTC4065AEDC
DC PART MARKING
LBPG
LBVJ
ORDER PART NUMBER
LTC4065EDC
LTC4065AEDC
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 (LTC4065 only) 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 (LTC4065) or Float PROG (LTC4065A)
●
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 = 10k (0.1%), Current Mode
RPROG = 2k (0.1%), Current Mode
IBMS
Battery Drain Current in Shutdown
Mode
VEN = VCC (LTC4065),
VPROG > VMS,PROG (LTC4065A)
IBUV
TYP
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
●
●
88
475
100
500
112
525
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 = 2k, IPROG = 500µA
RPROG = 10k, IPROG = 100µA
●
●
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
82
32
100
45
mV
mV
VMSH
Manual Shutdown High Voltage
(LTC4065)
VEN Rising
VMSL
Manual Shutdown Low Voltage
(LTC4065)
VEN Falling
REN
EN Pin Input Resistance
3.75
1
0.6
●
0.95
V
V
1.5
3.3
MΩ
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LTC4065/LTC4065A
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 (LTC4065 only) unless otherwise specified. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
IPROG
PROG Pin Pull-Up Current
(LTC4065A)
VPROG > 1V
MIN
VMS,PROG
PROG Shutdown Threshold Voltage
(LTC4065A Only)
VPROG Rising
tSS
Soft-Start Time
ITRKL
Trickle Charge Current
VBAT = 2V, RPROG = 2k (0.1%)
VTRKL
Trickle Charge Threshold Voltage
VBAT Rising
VTRHYS
Trickle Charge Hysteresis Voltage
∆VRECHRG
Recharge Battery Threshold Voltage
∆VUVCL1
∆VUVCL2
(VCC – VBAT) Undervoltage Current
Limit
tTIMER
Termination Timer
TYP
MAX
●
3.7
4
UNITS
µA
3
4.3
V
µs
180
35
50
65
2.7
2.9
3.05
V
VFLOAT – VRECHRG, 0°C < TA < 85°C
70
100
130
mV
IBAT = 90% Programmed Charge Current
IBAT = 10% Programmed Charge Current
180
90
220
125
330
150
mV
mV
3
4.5
6
Hrs
●
90
●
mA
mV
●
1.5
2.25
3
Hrs
Low-Battery Trickle Charge Time
VBAT = 2.5V
●
0.75
1.125
1.5
Hrs
VACPR
ACPR Pin Output Low Voltage
(LTC4065A)
IACPR = 5mA
●
60
105
mV
IACPR
ACPR Pin Input Current (LTC4065A)
VCC = 4V, VACPR = 4V, VBAT = 4.5V
●
0
1
µA
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 = 2k (Note 5)
●
TLIM
Junction Temperature in Constant
Temperature Mode
RON
Power FET “ON” Resistance
(Between VCC and BAT)
fBADBAT
DBADBAT
Recharge Time
0.085
0
1
0.1
0.115
µA
mA/mA
115
°C
450
mΩ
Defective Battery Detection CHRG
Pulse Frequency
2
Hz
Defective Battery Detection CHRG
Pulse Frequency Duty Ratio
75
%
IBAT = 200mA
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 LTC4065/LTC4065A are 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 LTC4065 functions properly at 3.75V, 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.
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LTC4065/LTC4065A
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TYPICAL PERFOR A CE CHARACTERISTICS
Battery Regulation (Float) Voltage
vs Battery Charge Current
Regulated Output (Float) Voltage
vs Supply Voltage
4.24
4.23
4.23
4.22
4.22
4.22
4.21
4.21
4.21
VCC = 5V
TA = 25°C
RPROG = 2k
VFLOAT (V)
4.23
4.20
4.19
VFLOAT (V)
4.24
4.24
VFLOAT (V)
Battery Regulation (Float) Voltage
vs Temperature
4.20
4.19
4.20
4.19
4.18
4.18
4.18
4.17
4.17
4.17
4.16
100
0
200
300
IBAT (mA)
400
4.16
–50
500
– 25
0
50
25
TEMPERATURE (°C)
75
4065 G01
5
4.5
5.5
SUPPLY VOLTAGE (V)
4
6
4065 G03
Charge Current vs Temperature
with Thermal Regulation
(Constant Current Mode)
Charge Current vs Battery Voltage
600
RPROG = 10k
VBAT = 3.8V
TA = 25°C
175
4.16
100
4065 G02
Charge Current vs Supply Voltage
(Constant Current Mode)
200
TA = 25°C
IBAT = 2mA
RPROG = 2k
600
VCC = 5V
TA = 25°C
RPROG = 2k
500
500
400
100
75
IBAT (mA)
400
125
IBAT (mA)
IBAT (mA)
150
300
THERMAL CONTROL
LOOP IN OPERATION
300
200
200
100
100
50
25
0
0
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
6
0
1
2
3
VBAT (V)
4
4065 G04
VCC = 5V
VBAT = 3.8V
RPROG = 2k
0
–50
5
0
100
50
TEMPERATURE (°C)
150
4065 G05
PROG Pin Voltage vs Temperature
(Constant Current Mode)
4065 G06
Power FET On Resistance
vs Temperature
PROG Pin Voltage
vs Charge Current
1.2
1.02
VCC = 5V
VBAT = 3.8V
RPROG = 10k
550
VCC = 5V
TA = 25°C
RPROG = 2k
1.0
VCC = 4V
IBAT = 400mA
500
1.01
1.00
RDS (mΩ)
VPROG (V)
VPROG (V)
0.8
0.6
450
400
0.4
0.99
350
0.2
0.98
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
4065 G07
0
0
100
200
300
IBAT (mA)
400
500
4065 G08
300
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4065 G09
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LTC4065/LTC4065A
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TYPICAL PERFOR A CE CHARACTERISTICS
Manual Shutdown Threshold
Voltage vs Temperature (LTC4065)
Undervoltage Lockout Threshold
Voltage vs Temperature
Manual Shutdown Supply Current
vs Temperature
1.0
4.0
3.8
40
0.9
30
RISE
RISE
3.3
FALL
3.0
0.8
ICCMS (µA)
VMS (V)
3.5
VCC (V)
VCC = 5V
VEN = 5V
FALL
0.7
20
10
0.6
2.8
2.5
–50
–25
50
0
25
TEMPERATURE (°C)
75
0.5
–50
100
50
25
0
TEMPERATURE (°C)
–25
75
4065 G16
60
50
60
IBAT (mA)
30
20
20
10
2.5
3
3.5
VEN (V)
4
4.5
4.5
5
5.5
SUPPLY VOLTAGE (V)
4
5
50
25
0
TEMPERATURE (°C)
75
100
4065 G15
ACPR Pin Output Low Voltage vs
Temperature (LTC4065A Only)
140
VCC = 5V
ICHRG = 5mA
120
100
VCC = 5V
IACPR = 5mA
VACPR (mV)
100
80
60
80
60
40
40
20
20
0
–50
–25
4065 G14
CHRG Pin Output Low Voltage
vs Temperature
120
0
–50
6
4065 G13
140
RPROG = 10k
10
0
2
30
RPROG = 10k
0.5
0
RPROG = 2k
40
1.0
VCHRG (mV)
IEN (µA)
IBAT (mA)
1.5
100
VCC = 5V
VBAT = 2V
50
RPROG = 2k
40
2.0
75
Trickle Charge Current
vs Temperature
VBAT = 2V
TA = 25°C
3.0
2.5
0
25
50
TEMPERATURE (°C)
4065 G12
Trickle Charge Current
vs Supply Voltage
VCC = 5V
TA = 25°C
3.5
–25
4065 G11
EN Pin Current (LTC4065)
4.0
0
–50
100
–25
50
25
0
TEMPERATURE (°C)
75
100
4065 G10
0
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
4065 G17
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LTC4065/LTC4065A
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TYPICAL PERFOR A CE CHARACTERISTICS
Timer Accuracy vs Temperature
Timer Accuracy vs Supply Voltage
2.0
VCC = 5V
0
1.5
–1
1.0
TIMER ACCURACY (%)
TIMER ACCURACY (%)
1
–2
–3
–4
–5
TA = 25°C
0.5
0
–0.5
–1.0
–1.5
–6
–7
–50
–2.0
–25
0
50
25
TEMPERATURE (°C)
75
100
4
5
4.5
5.5
SUPPLY VOLTAGE (V)
4065 G19
4065 G18
PROG Pin Shutdown Threshold vs
Temperature (LTC4065A Only)
5.0
6
PROG Pin Shutdown Voltage vs
Supply Voltage (LTC4065A Only)
5.0
VCC = 5V
TA = 25°C
4.5
VMS(PROG) (V)
VRMS(PROG) (V)
4.5
4.0
4.0
3.5
3.0
3.5
2.5
3.0
–50
2.0
–25
0
25
50
TEMPERATURE (°C)
75
100
4065 G20
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
6
4065 G21
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LTC4065/LTC4065A
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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 LTC4065 enters shutdown mode, dropping
IBAT to about 1µA.
ACPR (Pin 5, LTC4065A Only): Open-Drain Power Supply
Status Output. When VCC is greater than the undervoltage
lockout threshold (3.6V) and VBAT + 80mV (if VBAT > 3.6V),
the ACPR pin will be pulled down to ground; otherwise the
pin is high impedance.
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
• 1000
RPROG
Floating the PROG pin sets the charge current to zero
(LTC4065) or puts the part in shutdown mode (LTC4065A).
In shutdown mode, the LTC4065A has less than 20µA
supply current and about 1µA battery drain current.
Exposed Pad (Pin 7): Ground. The Exposed Pad must be
soldered to the PCB ground to provide both electrical contact and rated thermal performance.
EN (Pin 5, LTC4065 Only): Enable Input Pin. Pulling this
pin above the manual shutdown threshold (VMS is typically 0.82V) puts the LTC4065 in shutdown mode. In
shutdown mode, the LTC4065 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.
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LTC4065/LTC4065A
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SI PLIFIED BLOCK DIAGRA S
VCC
4
VCC
+
TDIE
D3
TA
M2
×1
EN
UVLO
–
3.6V
+
RENB
SHUTDOWN
C1
D1
D2
–
0.82V
BAT
–
+
R1
CA
–
R3
+
+
1V
–
C/10
1.2V
MP
R4
0.1V
R2
CHRG
VA
+
0.1V
3
+
MA
1.2V
REF
PROG
2
C2
M1
×1000
–
5
+
–
115°C
CHARGE CONTROL
R5
2.9V
BAT
+
LOGIC
ENABLE
–
COUNTER
LOBAT
SHUTDOWN
PROG
6
GND
1
OSCILLATOR
4056 F01a
RPROG
Figure 1a. LTC4065 Block Diagram
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LTC4065/LTC4065A
W
W
SI PLIFIED BLOCK DIAGRA S
VCC
4
VCC
+
D3
C2
5
ACPR
–
+
TDIE
–
115°C
TA
3.6V
M2
×1
+
M1
×1000
D1
D2
C3
BAT
–
+
MA
R1
CA
–
R3
+
+
1V
–
C/10
MP
R4
1.2V
0.1V
2
CHRG
R2
R5
2.9V
BAT
CHARGE CONTROL
ENABLE
–
+
VA
+
0.1V
3
+
–
–
1.2V
REF
PROG
VBAT + 80mV
LOGIC
+
LOBAT
SHUTDOWN
C1
4V
–
OSCILLATOR
PROG
6
COUNTER
GND
1
4056 F01b
RPROG
Figure 1b. LTC4065A Block Diagram
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OPERATIO
The LTC4065 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 750mA 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. The ACPR pin (LTC4065A)
monitors the status of the input voltage with an open-drain
output. An internal termination timer and trickle charge
low-battery conditioning adhere to battery manufacturer
safety guidelines. Furthermore, the LTC4065 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 LTC4065 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 LTC4065
or external components. Another benefit of the LTC4065
thermal limit is that charge current can be set according to
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LTC4065/LTC4065A
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OPERATIO
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 (LTC4065 only) 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. 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 LTC4065 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.
program resistor and the charge current are calculated
using the following equations:
RPROG = 1000 •
1V
ICHG
, ICHG =
1000 V
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
• 1000
RPROG
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.
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, momentarily force the EN pin above VMS
(typically 0.82V) for LTC4065, or momentarily float the
PROG pin and reconnect it (LTC4065A). The charge cycle
will automatically restart if the BAT pin voltage falls below
VRECHRG (typically 4.1V).
Shutdown Mode
When the input voltage is not present, the battery drain
current is reduced to less than 4µA. The LTC4065 can also
be shut down by pulling the EN pin above the shutdown
threshold voltage. To put LTC4065A in shutdown mode,
float the PROG pin. This reduces input quiescent current
to less than 20µA and battery drain current to less than 1µA.
The LTC4065 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.
Programming Charge Current
The charge current is programmed using a single resistor
from the PROG pin to ground. The battery charge current
is 1000 times the current out of the PROG pin. The
The LTC4065 can be disabled by pulling the EN pin above
the shutdown threshold (approximately 0.82V). The
LTC4065A can be disabled by floating the PROG pin. In
shutdown mode, the battery drain current is reduced to
less than 1µA and the supply current to about 20µA.
Timer and Recharge
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.
4065fb
10
LTC4065/LTC4065A
U
OPERATIO
Once the charge cycle terminates, the LTC4065 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. 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, temporarily pull the EN pin above the shutdown
threshold (LTC4065), or momentarily float the PROG pin
and reconnect it (LTC4065A).
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 LTC4065 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 LTC4065
is disabled. Figure 2 shows the CHRG status under various
conditions.
Power Supply Status Indicator
(ACPR, LTC4065A Only)
The power supply status output has two states: pull-down
and high impedance. The pull-down state indicates that
VCC is above the undervoltage lockout threshold (see
Undervoltage Lockout). When this condition is not met,
the ACPR pin is high impedance indicating that the
LTC4065A is unable to charge the battery.
Charge Current Soft-Start and Soft-Stop
The LTC4065 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 180µs.
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 LTC4065/LTC4065A use a unique architecture to
charge a battery in a constant-current, constant-voltage
and constant-temperature fashion. Figures 1a and 1b
show simplified block diagrams of the LTC4065 and
LTC4065A, respectively. Three of the amplifier feedback
loops shown control the constant-current, CA, constantvoltage, 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 1000 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”.
4065fb
11
LTC4065/LTC4065A
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
RECHARGE
IS VBAT < 4.1V?
IS VBAT < 2.9V?
YES
YES
BAD BATTERY MODE
NO CHARGE CURRENT
CHRG PULSES (2Hz)
VCC < 3V
OR
EN > SHDN
THRESHOLD
STANDBY MODE
NO CHARGE CURRENT
CHRG HIGH IMPEDANCE
NO
CHARGE CYCLE
(4.5 HOURS)
DEFECTIVE BATTERY
VBAT > 4.1V
RECHARGE MODE
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
1/2 CHARGE CYCLE
(2.25 HOURS)
4065 F02
Figure 2. State Diagram of LTC4065 Operation
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 1000V/RPROG. If the power dissipation of the
LTC4065/LTC4065A 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
LTC4065/LTC4065A either return to constant-current mode
or enter constant-voltage mode straight from constanttemperature mode. Regardless of mode, the voltage at
the PROG pin is proportional to the current delivered to
the battery.
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12
LTC4065/LTC4065A
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APPLICATIO S I FOR ATIO
Undervoltage Charge Current Limiting (UVCL)
The LTC4065/LTC4065A 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 LTC4065 is powered from a supply with
long leads (or any relatively high output impedance).
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.
Consider a situation where the LTC4065 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
LTC4065 will continue to operate at the reduced charge
current until the input supply voltage is increased or
voltage mode reduces the charge current further.
Operation from Current Limited Wall Adapter
By using a current limited wall adapter as the input
supply, the LTC4065 dissipates significantly less power
when programmed for a current higher than the limit of
the supply as compared to using a non-current limited
supply at the same charge current.
Consider a situation where an application demands a
600mA charge current for an 800mAh Li-Ion battery. If a
typical 5V (non-current limited) input supply is available
then the peak power dissipation inside the part can
exceed 1W.
Now consider the same scenario, but with a 5V input
supply with a 600mA current limit. To take advantage of
the supply, it is necessary to program the LTC4065 to
charge at a current above 600mA. Assume that the LTC4065
is programmed for 650mA (i.e., RPROG = 1.54k) to ensure
that part tolerances maintain a programmed current higher
than 600mA. Since the LTC4065 will demand a charge
current higher than the current limit of the voltage supply,
the supply voltage will drop to the battery voltage plus
600mA times the “on” resistance of the internal PFET. The
“on” resistance of the LTC4065 power device is approximately 450mΩ with a 5V supply. The actual “on” resistance will be slightly higher due to the fact that the input
supply will drop to less than 5V. The power dissipated
during this phase of charging is less than 240mW. That is
a 76% improvement over the non-current limited supply
power dissipation.
USB and Wall Adapter Power
Although the LTC4065/LTC4065A allow 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.
Typically a wall adapter can supply significantly more
current than the 500mA-limited USB port. Therefore, an
N-channel MOSFET, MN1, and an extra program resistor
are used to increase the charge current to 750mA when the
wall adapter is present.
5V WALL
ADAPTER
750mA
ICHG
USB
POWER
500mA
ICHG
BAT
D1
4
MP1
3
ICHG
SYSTEM
LOAD
LTC4065
VCC
PROG
MN1 4.02k
+
6
Li-Ion
BATTERY
2k
1k
4065 F03
Figure 3. Combining Wall Adapter and USB Power
Stability Considerations
The LTC4065/LTC4065A contain two control loops: constant-voltage and constant-current. The constant-voltage
loop is stable without any compensation when a battery is
connected with low impedance leads. Excessive lead
4065fb
13
LTC4065/LTC4065A
U
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APPLICATIO S I FOR ATIO
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.
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.
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 ≤
1
• CPROG
2π • 105
10k
PROG
GND
RPROG
The conditions that cause the LTC4065/LTC4065A to
reduce charge current through thermal feedback can be
approximated by considering the power dissipated in the
IC. For high charge currents, the LTC4065/LTC4065A
power dissipation is approximately:
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 LTC4065 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:
TA = 115°C – PD • θJA
TA = 115°C – (VCC – VBAT) • IBAT • θJA
Example: Consider an LTC4065/LTC4065A operating from
a 5V wall adapter providing 750mA to a 3.6V Li-Ion
battery. The ambient temperature above which the
LTC4065/LTC4065A will begin to reduce the 750mA charge
current is approximately:
TA = 115°C – (5V – 3.6V) • (750mA) • 60°C/W
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
battery current as shown in Figure 4. A 10K resistor has
been added between the PROG pin and the filter capacitor
to ensure stability.
LTC4065
Power Dissipation
CFILTER
CHARGE
CURRENT
MONITOR
CIRCUITRY
4065 F04
TA = 115°C – 1.05W • 60°C/W = 115°C – 63°C
TA = 52°C
The LTC4065/LTC4065A can be used above 70°C, but the
charge current will be reduced from 750mA. The approximate current at a given ambient temperature can be
calculated:
IBAT =
115°C – TA
( VCC – VBAT ) • θJA
Using the previous example with an ambient temperature
of 73°C, the charge current will be reduced to approximately:
IBAT =
115°C – 73°C
42°C
=
= 500mA
(5V – 3.6V ) • 60°C/W 84°C/A
Figure 4. Isolating Capacitive Load on the PROG Pin and Filtering
4065fb
14
LTC4065/LTC4065A
U
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APPLICATIO S I FOR ATIO
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 LTC4065/LTC4065A
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 LTC4065/LTC4065A package is soldered
to the PC board ground. Correctly soldered to a 2500mm2
double-sided 1 oz. copper board the LTC4065/LTC4065A
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. As an
example, a correctly soldered LTC4065/LTC4065A can
deliver over 750mA to a battery from a 5V supply at room
temperature. Without a backside thermal connection, this
number could drop to less than 500mA.
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.
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
4065fb
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
LTC4065/LTC4065A
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ThinSOT and PowerPath are trademarks of Linear Technology Corporation.
4065fb
16
Linear Technology Corporation
LT 0406 REV B • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2005