LTC4064
Monolithic Linear Charger
for Back-Up Li-Ion Batteries
U
FEATURES
DESCRIPTIO
■
The LTC4064 is a standalone linear charger optimized for
prolonging the life of 1-cell Li-ion batteries in battery backup applications. By charging to a float voltage of 4V
instead of 4.2V or 4.1V, the LTC4064 decelerates the aging
process and capacity degradation when the battery is
unused for long periods of time but must be in a ready
state.
■
■
■
■
■
■
■
■
■
■
■
Preset 4V Charge Voltage with 1% Accuracy
Prolongs 4.2V Li-Ion Battery Lifetime
Automatic Recharge
Thermal Regulation Maximizes Charging Rate
without Risk of Overheating*
No MOSFET, Sense Resistor or Blocking Diode
Required
Programmable Charge Termination Timer
Thermistor Input for Temperature Qualified Charging
Programmable Charge Current with 7% Accuracy
C/10 Charge Current Detection Output
25µA Supply Current in Shutdown Mode
Charge Current Monitor Useful for Gas Gauging*
Charges Directly from USB Port
Tiny Thermally Enhanced 10-pin MSOP Package
An external capacitor programs a safety timer to terminate
the charge cycle while the charge current is set externally
with a single resistor. When the input supply is removed,
the LTC4064 automatically enters a low current sleep
mode, dropping the battery drain current to less than 3µA.
Additional safety features designed to maximize battery
lifetime and reliability include NTC temperature sensing
and low battery charge conditioning (trickle charging).
U
APPLICATIO S
■
■
File Servers, RAID Systems
Storage Products
Li-Ion Battery Back-Up
, LTC and LT are registered trademarks of Linear Technology Corporation.
*US Patent No. 6522118
U
■
The IC contains an on-chip power MOSFET and eliminates
the need for an external sense resistor and blocking diode.
The LTC4064 also includes C/10 detection circuitry, AC
present logic, and fault detection circuitry.
TYPICAL APPLICATIO
Standalone Back-Up Li-Ion Battery Charger
VIN = 5V
8
SHDN
2
VCC
BAT
4.7µF
9
IBAT = 1A
VFLOAT = 4V
LTC4064
4
7
PROG
TIMER
GND
0.1µF
5, 11
NTC
6
1.5k
1%
1-CELL
Li-Ion
BATTERY*
4064TA01
*AN OUTPUT CAPACITOR MAY BE REQUIRED
DEPENDING ON BATTERY LEAD LENGTH
sn4064 4064fs
1
LTC4064
U
W W
W
ABSOLUTE
AXI U RATI GS
U
W
U
PACKAGE/ORDER I FOR ATIO
(Note 1)
Input Supply Voltage (VCC) ..................................... 10V
BAT ......................................................................... 10V
NTC, SHDN, TIMER, PROG ............ –0.3V to VCC + 0.3V
CHRG, FAULT, ACPR ................................ –0.3V to 10V
BAT Short-Circuit Duration .......................... Continuous
BAT Current (Note 2) ............................................. 1.3A
PROG Current (Note 2) ....................................... 1.3mA
Junction Temperature .......................................... 125°C
Operating Temperature Range (Note 3) ...–40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
TOP VIEW
CHRG
VCC
FAULT
TIMER
GND
1
2
3
4
5
11
10
9
8
7
6
ACPR
BAT
SHDN
PROG
NTC
LTC4064EMSE
MSE EXPOSED PAD PACKAGE
10-LEAD PLASTIC MSOP
MSE PART MARKING
TJMAX = 125°C, θJA = 40°C/W (Note 4)
EXPOSED PAD IS GND, (PIN 11)
MUST BE SOLDERED TO PCB
LTAHQ
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V
SYMBOL
PARAMETER
VCC
VCC Supply Voltage
CONDITIONS
ICC
VCC Supply Current
VFLOAT
VBAT Regulated Float Voltage
IBAT
Battery Pin Current
ITRIKL
VTRIKL
∆VTRIKL
Trickle Charge Trip Hysteresis Voltage
VUV
VCC Undervoltage Lockout Voltage
∆VUV
VCC Undervoltage Lockout Hysteresis
VMSD
Manual Shutdown Threshold Voltage
VASD
Automatic Shutdown Threshold Voltage (VCC - VBAT) High to Low
(VCC - VBAT) Low to High
MIN
●
Charger On; Current Mode; RPROG = 30k (Note 5)
Shutdown Mode; VSHDN = 0V
Sleep Mode VCC < VBAT or VCC ≤ 4V
TYP
MAX
UNITS
6.5
V
1
25
25
2
50
50
mA
µA
µA
4.25
●
●
●
●
3.96
4.00
4.04
V
RPROG = 3k; Current Mode
RPROG = 15k; Current Mode
Shutdown Mode; VSHDN = 0V
Sleep Mode VCC < VBAT or VCC < (VUV – ∆VUV)
●
●
465
93
500
100
±1
±1
535
107
±3
±3
mA
mA
µA
µA
Trickle Charge Current
VBAT < 2V; RPROG = 3k
●
35
50
65
mA
Trickle Charge Trip Threshold Voltage
VBAT Rising
VCC Rising
●
2.48
V
100
mV
4
4.25
200
SHDN Pin Voltage
0.6
1.3
35
70
V
mV
V
mV
mV
sn4064 4064fs
2
LTC4064
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
VPROG
PROG Pin Voltage
RPROG = 3k, IPROG = 500µA
ICHRG
CHRG Pin Weak Pulldown Current
VCHRG = 1V
30
50
µA
VCHRG
CHRG Pin Output Low Voltage
ICHRG = 5mA
0.35
0.6
V
VACPR
ACPR Pin Output Low Voltage
IACPR = 5mA
0.35
0.6
V
VFAULT
FAULT Pin Output Low Voltage
IFAULT = 5mA
0.35
0.6
V
IC/10
End of Charge Indication Current Level
RPROG = 3k
50
56
mA
tTIMER
TIMER Accuracy
CTIMER = 0.1µF
∆VRECHRG
Recharge Threshold Voltage
VFLOAT - VRECHRG, VBAT > VTRIKL
Charge Termination Timer Expired
VNTC-HOT
NTC Pin Hot Threshold Voltage
VNTC Falling
2.5
V
VHOT-HYS
NTC Pin Hot Hysteresis Voltage
80
mV
VNTC-COLD
NTC Pin Cold Threshold Voltage
VNTC Rising
4.375
VCOLD-HYS
NTC Pin Cold Hystersis Voltage
VNTC-DIS
NTC Pin Disable Threshold Voltage
100
mV
VDIS-HYS
NTC Pin Disable Hystersis Voltage
10
mV
TLIM
Junction Temperature in
Constant-Temperature Mode
105
°C
RON
Power MOSFET “ON” Resistance
375
mΩ
1.5
15
44
●
65
100
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The Absolute Maximum BAT Current Rating of 1.3A is guaranteed
by design and current density calculations. The Absolute Maximum PROG
Current Rating is guaranteed to be 1/1000 of BAT current rating by design.
Note 3: The LTC4064 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
UNITS
V
10
80
VNTC Rising
MAX
%
135
mV
V
mV
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 4: Failure to solder the exposed backside of the package to the PC
board will result in a thermal resistance much higher than 40°C/W.
Note 5: Supply current includes PROG pin current (approximately 50µA)
but does not include any current delivered to the battery through the BAT
pin (approximately 50mA).
sn4064 4064fs
3
LTC4064
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Battery Regulation Voltage
vs Battery Charge Current
4.02
Battery Regulation Voltage
vs Temperature
VCC = 5V
TA = 25°C
RPROG = 3k
4.01
4.010
4.02
4.008
4.00
4.006
3.99
3.96
3.94
3.92
3.98
3.88
50 100 150 200 250 300 350 400 450 500
IBAT (mA)
4.000
3.998
3.994
VCC = 5V
RPROG = 3k
IBAT = 10mA
3.97
0
4.002
3.996
3.90
3.96
3.86
–50
3.992
3.990
0
25
50
75
TEMPERATURE (°C)
–25
100
4064 G01
4
125
TA = 25°C
200
100
700
IBAT (mA)
250
400
150
300
100
200
50
100
0
0
0.5
1
VCC (V)
1.5
2 2.5
VBAT (V)
3
3.5
4064 G04
4
30
4.04
100
4064 G06
1.20
VCC = 6V
1.15
VCC = 5.5V
1.10
15
VMSD (V)
ICC (µA)
VUV (V)
75
1.25
VCC = 6.5V
20
1.05
VCC = 4.5V
1.00
10
3.97
25
50
0
TEMPERATURE (°C)
1.30
VCC = 5.5V
4.02
3.98
–25
Manual Shutdown Threshold
Voltage vs Temperature and VCC
VSHDN = 0V
25
4.03
3.99
VCC = 5V
VBAT = 3.5V
RPROG = 1.5k
0
–50
4.5
Shutdown Supply Current
vs Temperature and VCC
4.00
THERMAL CONTROL
LOOP IN OPERATION
4064 G05
4.05
0.95
VCC = 5V
0.90
5
3.96
3.95
–50 –25
600
500
200
Undervoltage Lockout Voltage
vs Temperature
7
800
300
5.5
4.01
6.5
900
350
IBAT (mA)
IBAT (mA)
400
5.0
6
Charge Current vs Ambient
Temperature with Thermal
Regulation
400
4.5
5.5
VCC (V)
1000
VCC = 5V
TA = 25°C
RPROG = 3k
500
450
4.0
5
4064 G03
Charge Current vs Battery Voltage
550
500
0
4.5
4064 G02
Charge Current vs Input Voltage
300
VCC = 5V
TA = 25°C
RPROG = 3k
IBAT = 10mA
4.004
VBAT (V)
VBAT (V)
VBAT (V)
4.04
3.98
4.00
600
Battery Regulation Voltage
vs VCC
VCC = 4.5V
0.85
50
25
0
75
TEMPERATURE (°C)
100
125
4064 G07
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
4064 G08
0.80
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
4064 G09
sn4064 4064fs
4
LTC4064
U W
TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage
vs Charge Current
1.515
1.515
1.6
VCC = 5V
TA = 25°C
RPROG = 3k
1.4
PROG Pin Voltage vs Temperature
Constant Current Mode
PROG Pin Voltage vs VCC
Constant Current Mode
VBAT = 3.5V
TA = 25°C
RPROG = 3k
1.510
VCC = 5V
VBAT = 4V
RPROG = 3k
1.510
1.505
0.8
0.6
VPROG (V)
1.505
1.0
VPROG (V)
VPROG (V)
1.2
1.500
1.500
1.495
1.495
1.490
1.490
0.4
0.2
1.485
0
0
50 100 150 200 250 300 350 400 450 500
CHARGE CURRENT (mA)
4
4.5
5
5.5
VCC (V)
6.5
6
Trickle Charge Current
vs Temperature
0.6
VCC = 5V
34 IBAT < C/10
32
VCHRG (V)
ICHRG (µA)
VCC = 5V
ICHRG = 5mA
0.4
31
30
29
0.3
0.2
28
27
8
100
0.5
33
9
75
CHRG Pin Output Low Voltage
vs Temperature
35
10
0
25
50
TEMPERATURE (°C)
4064 G12
CHRG Pin Weak Pull-Down
Current vs Temperature
VBAT = 2V
TA = 25°C
RPROG = 3k
0.1
26
50
25
0
75
TEMPERATURE (°C)
100
125
25
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
Timer Error vs Temperature
5
4
50
25
75
0
TEMPERATURE (°C)
100
125
4064 G15
Timer Error vs VCC
5
VCC = 5V
CTIMER = 0.1µF
TA = 25°C
CTIMER = 0.1µF
4
3
3
2
2
1
0
–1
–2
1
0
–1
–2
–3
–3
–4
–4
–5
–50 –25
0
–50 –25
125
4064 G14
4064 G13
tTIMER (%)
7
–50 –25
tTIMER (%)
IBAT (% OF PROGRAMMED CURRENT)
11
–25
4064 G11
4064 G10
12
1.485
–50
7
–5
50
25
0
75
TEMPERATURE (°C)
100
125
4064 G16
4
4.5
5
5.5
VCC (V)
6
6.5
7
4064 G17
sn4064 4064fs
5
LTC4064
U
U
U
PI FU CTIO S
CHRG (Pin 1): Open-Drain Charge Status Output. 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 N-channel
MOSFET latches off and a 30µA current source is connected from the CHRG pin to ground. The C/10 latch can
be cleared by grounding the SHDN pin, momentarily, or
toggling VCC. When the timer runs out or the input supply
is removed, the current source is disconnected and the
CHRG pin is forced high impedance.
VCC (Pin 2): Positive Input Supply Voltage. When VCC is
within 35mV of VBAT or less than the undervoltage lockout
threshold, the LTC4064 enters sleep mode, dropping IBAT
to less than 3µA. VCC can range from 4.25V to 6.5V.
Bypass this pin with at least a 4.7µF ceramic capacitor to
ground.
FAULT (Pin 3): Open-Drain Fault Status Output. The
FAULT open-drain logic signal indicates that the charger
has timed out under trickle charge conditions or the NTC
comparator is indicating an out-of-range battery temperature condition. If VBAT is less that 2.48V, trickle charging
begins whereby the charge current drops to one tenth of
its programmed value and the timer period is reduced by
a factor of four. When one fourth of the timing period has
elapsed, if VBAT is still less than 2.48V, trickle charging
stops and the FAULT pin latches to ground. The fault can
be cleared by toggling VCC, momentarily grounding the
SHDN pin or pulling the BAT pin above 2.48V. If the NTC
comparator is indicating an out-of-range battery temperature condition, the FAULT pin will pull to ground until the
temperature returns to the acceptable range.
TIMER (Pin 4): Timer Capacitor. The timer period is set by
placing a capacitor, CTIMER, to ground. The timer period is:
Time (Hours) = (CTIMER • 3 hr)/(0.1µF)
Short the TIMER pin to ground to disable the internal timer
function.
NTC (Pin 6): Input to the NTC (Negative Temperature
Coefficient) Thermistor Temperature Monitoring Circuit.
With an external 10kΩ NTC thermistor to ground and a 1%
resistor to VCC, this pin can sense the temperature of the
battery pack and stop charging when it is out of range.
When the voltage at this pin drops below (0.5)•(VCC) at hot
temperatures or rises above (0.875)•(VCC) at cold, charging is suspended and the internal timer is frozen. The
CHRG pin output status is not affected in this hold state.
The FAULT pin will be pulled to ground, but not latched.
When the temperature returns to an acceptable range,
charging will resume and the FAULT pin is released. The
NTC feature can be disabled by grounding the NTC pin.
PROG (Pin 7): Charge Current Program and Charge Current Monitor Pin. The charge current is programmed by
connecting a resistor, RPROG to ground. When in constant-current mode, the LTC4064 servos the PROG pin
voltage to 1.5V. In all modes the voltage on the PROG pin
can be used to measure the charge current as follows:
IBAT = (VPROG/RPROG) • 1000.
SHDN (Pin 8): Shutdown Input Pin. Pulling the SHDN pin
to ground will put the LTC4064 into standby mode where
the BAT drain current is reduced to less than 3µA, and the
supply current is reduced to less than 25µA. For normal
operation, pull the SHDN pin up to VCC.
BAT (Pin 9): Charge Current Output. A bypass capacitor of
at least 1µF with a 1Ω series resistor is required to keep the
loop stable when the battery is not present. A precision
internal resistor divider sets the final float potential on this
pin. The internal resistor divider is disconnected in sleep
and shutdown mode.
ACPR (Pin 10): Open-Drain Power Supply Status Output.
When VCC is greater than the undervoltage lockout threshold and at least 35mV above VBAT, the ACPR pin will pull
to ground. Otherwise, the pin is high impedance.
GND (Pins 5, 11): Ground. The exposed backside of the
package is also ground and must be soldered to the PC
board for maximum heat transfer.
sn4064 4064fs
6
LTC4064
W
W
SI PLIFIED BLOCK DIAGRA
VCC
2
–
105°C
D1
TA
D2
+
TDIE
M2
×1
D3
M1
×1000
+
–
MA
9
30µA
NTC 6
BAT
R1
NTC
MP
+
VA
–
CA
R2
+
–
2.485V
REF
HOT COLD DISABLE
CHRG 1
STOP
SHDN
8 SHDN
C/10
R3
30µA
1.5V
LOGIC
ACPR 10
R4
ACPR
0.15V
+
C2
C/10
FAULT 3
R5
–
FAULT
CHARGE
COUNTER
C3
OSCILLATOR
–
2.485V
4
+
TO BAT
7
TIMER
PROG
5, 11
GND
4064 BD
RPROG
CTIMER
Figure 1
sn4064 4064fs
7
LTC4064
U
OPERATIO
The LTC4064 is a linear battery charger designed primarily
for charging single cell lithium-ion batteries used in backup applications. With a 4V final float voltage accuracy of
±1%, the LTC4064 maximizes the lifetime of 4.2V chemistry lithium-ion batteries. A precision, automatic recharge
feature ensures that the battery voltage remains within
100mV of this 4V float voltage at all times.
Featuring an internal P-channel power MOSFET, the charger
uses a constant-current/constant-voltage charge algorithm with programmable current and a programmable
timer for charge termination. Charge current can be
programmed up to 1.25A with an accuracy of ±7%. No
blocking diode or sense resistor is required thus dropping
the external component count to three for the basic
charger circuit. The CHRG, ACPR, and FAULT open-drain
status outputs provide information regarding the status of
the LTC4064 at all times. An NTC thermistor input
provides the option of charge qualification using battery
temperature.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 105°C. This feature protects
the LTC4064 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 LTC4064
or the external components. Another benefit of the LTC4064
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 voltage at the VCC pin
rises above the UVLO level, a program resistor is connected from the PROG pin to ground, and the SHDN pin is
pulled above the shutdown threshold. At the beginning of
the charge cycle, if the battery voltage is below 2.48V, the
charger goes into trickle charge mode to bring the cell
voltage up to a safe level for charging. The charger goes
into the fast charge constant-current mode once the
voltage on the BAT pin rises above 2.48V. In constantcurrent mode, the charge current is set by RPROG.
When the battery approaches the final float voltage, the
charge current begins to decrease as the LTC4064 enters
the constant-voltage mode. When the current drops to
10% of the full-scale charge current, an internal comparator latches off the MOSFET on the CHRG pin and connects
a weak current source to ground (30µA) to indicate a near
end-of-charge (C/10) condition. The C/10 latch can be
cleared by grounding the SHDN pin momentarily, or
momentarily removing and reapplying VCC.
An external capacitor on the TIMER pin sets the total
charge time. 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 SHDN pin to 0V.
The charge cycle will also restart if the BAT pin voltage falls
below the recharge threshold.
When the input voltage is not present, the charger goes
into a sleep mode, dropping battery drain current, IBAT, to
less than 3µA. This greatly reduces the current drain on the
battery and increases the standby time. The charger can be
shut down (ICC = 25µA) by forcing the SHDN pin to 0V.
sn4064 4064fs
8
LTC4064
U
W
U
U
APPLICATIO S I FOR ATIO
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until VCC
rises above the undervoltage lockout threshold. The UVLO
circuit has a built-in hysteresis of 200mV. Furthermore, to
protect against reverse current in the power MOSFET, the
UVLO circuit keeps the charger in shutdown mode if VCC
falls to within 35mV of the battery voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown until VCC rises 70mV above the battery voltage.
For example, if 500mA charge current is required,
calculate:
RPROG = 1500V/0.5A = 3kΩ
For best stability over temperature and time, 1% metalfilm resistors are recommended.
If the charger is in constant-temperature or constantvoltage mode, the battery current can be monitored by
measuring the PROG pin voltage as follows:
IBAT = (VPROG / RPROG) • 1000
Trickle Charge And Defective Battery Detection
USB and Wall Adapter Power
At the beginning of a charge cycle, if the battery voltage is
low (below 2.48V) 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 charge time, the battery is assumed to be
defective, the charge cycle is terminated, the CHRG pin
output assumes a high impedance state, and the FAULT
pin pulls low. The fault can be cleared by toggling VCC,
temporarily forcing the SHDN pin to 0V, or temporarily
forcing the BAT pin voltage above 2.48V.
Although the LTC4064 allows charging from a USB port,
a wall adapter can also be used to charge Li-Ion batteries.
Figure 2 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.
Shutdown
The LTC4064 can be shut down (ICC = 25µA) by pulling the
SHDN pin to 0V. For normal operation, pull the SHDN pin
above the manual shutdown threshold voltage level. Do
not leave this pin open. In shutdown the internal linear
regulator is turned off, and the internal timer is reset.
Programming Charge Current
Typically a wall adapter can supply significantly more
current than the 500mA-limited USB port. Therefore, an Nchannel MOSFET, MN1 and an extra 3k program resistor
can be used to increase the charge current to 1A when the
wall adapter is present.
5V WALL
ADAPTER
1A ICHG
USB
POWER
500mA ICHG
LTC4064
D1
2
MP1
BAT
= (1.5V / RPROG) • 1000 or
ICHG
SYSTEM
LOAD
VCC
The formula for the battery charge current (see Figure 1)
is:
ICHG = (IPROG) • 1000
9
PROG
7
+
Li-Ion
BATTERY
3k
1k
MN1
3k
4064 F02
RPROG = 1500V/ICHG
where RPROG is the total resistance from the PROG pin to
ground. Under trickle charge conditions, this current is
reduced to 10% of the full-scale value.
Figure 2. Combining Wall Adapter and USB Power
sn4064 4064fs
9
LTC4064
U
W
U U
APPLICATIO S I FOR ATIO
Programming The Timer
The programmable timer is used to terminate the charge
cycle. The timer duration is programmed by an external
capacitor at the TIMER pin. The total charge time is:
Table 1.
FAULT
CHRG
High
Low
Charge cycle has started, C/10 has not been
reached and charging is proceeding normally.
Low
Low
Charge cycle has started, C/10 has not been
reached, but the charge current and timer
have been paused due to an NTC out-oftemperature condition.
High
30µA
pull-down
C/10 has been reached and charging is
proceeding normally.
Low
30µA
pull-down
C/10 has been reached but the charge current
and timer have paused due to an NTC out-oftemperature condition.
High
High
Normal timeout (charging has terminated).
Low
High
If FAULT goes low and CHRG goes high
impedance simultaneously, then the LTC4064
has timed out due to a bad cell (VBAT
工商网监
湘ICP备2023018690号
