LT3652HVEMSE-TRPBF [Linear]
Power Tracking 2A Battery Charger; 功率跟踪2A电池充电器型号: | LT3652HVEMSE-TRPBF |
厂家: | Linear |
描述: | Power Tracking 2A Battery Charger |
文件: | 总24页 (文件大小:250K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LT3652HV
Power Tracking 2A Battery
Charger
FEATURES
DESCRIPTION
The LT®3652HV is a complete monolithic step-down bat-
tery charger that operates over a 4.95V to 34V input range.
The LT3652HV provides a constant-current/constant-voltage
charge characteristic, with maximum charge current
externally programmable up to 2A. The charger employs
a 3.3V float voltage feedback reference, so any desired
battery float voltage up to 18V can be programmed with a
resistor divider.
n
Input Supply Voltage Regulation Loop for Peak
Power Tracking in (MPPT) Solar Applications
n
Wide Input Voltage Range: 4.95V to 34V (40V Abs Max)
n
Programmable Charge Rate Up to 2A
n
User Selectable Termination: C/10 or On-Board
Termination Timer
n
Resistor Programmable Float Voltage Up to 18V
Accommodates 4-Cell Li-Ion/Polymer, 5-Cell
LiFePO , Lead-Acid Chemistries
4
The LT3652HV employs an input voltage regulation loop,
whichreduceschargecurrentiftheinputvoltagefallsbelow
a programmed level, set with a resistor divider. When the
LT3652HV is powered by a solar panel, the input regulation
loop is used to maintain the panel at peak output power.
n
n
n
n
n
n
Parallelable for Higher Output Current
1MHz Fixed Frequency
0.5% Float Voltage Reference Accuracy
5% Charge Current Accuracy
2.5% C/10 Detection Accuracy
Binary-Coded Open-Collector Status Pins
TheLT3652HVcanbeconfiguredtoterminatechargingwhen
chargecurrentfallsbelow1/10oftheprogrammedmaximum
(C/10). Once charging is terminated, the LT3652HV enters a
low-current(85μA)standbymode.Anauto-rechargefeature
starts a new charging cycle if the battery voltage falls 2.5%
below the programmed float voltage. The LT3652HV also
contains a programmable safety timer, used to terminate
charging after a desired time is reached. This allows top-off
charging at currents less than C/10.
APPLICATIONS
n
Solar Powered Applications
n
Remote Monitoring Stations
n
Portable Handheld Instruments
12V to 24V Automotive Systems
Battery Charging from Current Limited Adapter
n
n
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
VIN_REG Loop Servos Maximum Charge Current to Prevent AC Adapter Output from
Drooping Lower Than 24V 5-Cell LiFePO4 Charger (18V at 1.5A) with C/10 Termination
Powered by Inexpensive 24VDC/1A Unregulated Wall Adapter.
1A/24VDC Unregulated Adapter
I vs V Characteristic
36
33
30
27
D3
MBRS340
MBRS340
AC ADAPTER
INPUT
24VDC AT 1A
SW
V
V
IN
LT3652HV
10V
750k
10μF
1μF
1N4148
20μH
0.068
IN_REG
BOOST
SENSE
BAT
44.2k
24
21
18
15
12
SHDN
SYSTEM
LOAD
51.1k
CHRG
FAULT
TIMER
665k
150k
NTC
+
127k
10μF
V
FB
3652 TA01a
0
0.2
0.6 0.8
1
1.2 1.4 1.6 1.8
2
0.4
R1
10K
ADAPTER OUTPUT CURRENT (A)
5-Cell LiFePO PACK
4
(18V FLOAT)
B = 3380
3652 TA01b
3652hvf
1
LT3652HV
ABSOLUTE MAXIMUM RATINGS
(Note 1)
BAT-SENSE ......................................... –0.5V to +0.5V
NTC, TIMER,........................................................2.5V
FB
Voltages:
V ........................................................................40V
IN
IN_REG
V ..........................................................................5V
V
, SHDN, CHRG, FAULT ............ V + 0.5V, 40V
IN
Operating Junction Temperature Range
(Note 2) ............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
SW........................................................................40V
SW-V .................................................................4.5V
IN
BOOST...................................................SW+10V, 50V
BAT, SENSE...........................................................20V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
1
2
3
4
5
6
12 SW
V
IN
1
2
3
4
5
6
V
12 SW
11 BOOST
10 SENSE
IN
11 BOOST
10 SENSE
V
IN_REG
V
IN_REG
SHDN
CHRG
FAULT
TIMER
SHDN
13
13
9
8
7
BAT
NTC
CHRG
FAULT
TIMER
9
8
7
BAT
NTC
V
FB
V
FB
MSE PACKAGE
12-LEAD PLASTIC MSOP
DD PACKAGE
12-LEAD (3mm × 3mm) PLASTIC DFN
T
= 125°C, θ = 43°C/W, θ = 3°C/W
T
= 125°C, θ = 43°C/W, θ = 3°C/W
JMAX
JA
JC
JMAX JA JC
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3652HVEDD#PBF
LT3652HVIDD#PBF
LT3652HVEMSE#PBF
LT3652HVIMSE#PBF
TAPE AND REEL
PART MARKING*
LFRG
PACKAGE DESCRIPTION
12-Lead Plastic DFN 3mm × 3mm
TEMPERATURE RANGE
–40°C to 125°C
LT3652HVEDD#TRPBF
LT3652HVIDD#TRPBF
LFRG
12-Lead Plastic DFN 3mm × 3mm
12-Lead Plastic MSOP
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LT3652HVEMSE#TRPBF 3652HV
LT3652HVIMSE#TRPBF 3652HV
12-Lead Plastic MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
3652hvf
2
LT3652HV
The l denotes the specifications which apply over the full operating junction
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68μF.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
V
V
V
V
V
V
Operating Range
Start Voltage
V
V
= 4.2 (Notes 3, 4)
= 4.2 (Note 4)
4.95
7.5
34
V
V
IN
IN
IN
BAT
BAT
l
OVLO Threshold
OVLO Hysteresis
V
Rising
34
35
1
40
V
V
IN(OVLO)
IN(UVLO)
FB(FLT)
IN
UVLO Threshold
UVLO Hysteresis
V
Rising
4.6
0.2
4.95
V
V
IN
Float Voltage Reference
(Note 6)
3.282
3.26
3.3
3.318
3.34
V
V
l
ΔV
Recharge Reference Threshold
Voltage Relative to V
(Note 6)
(Note 6)
82.5
2.3
70
mV
V
RECHARGE
FB(FLT)
V
V
Reference Precondition Threshold
V
FB
Rising (Note 6)
FB(PRE)
Reference Precondition Threshold
Hysteresis
Voltage Relative to V
mV
FB(PREHYST)
FB(PRE)
l
l
l
V
Input Regulation Reference
V
V
= 3V; V
– V = 50mV
2.65
2.7
35
2.75
100
3.5
V
IN_REG(TH)
IN_REG
VIN
FB
SENSE
BAT
I
I
Input Regulation Reference Bias Current
Operating Input Supply Current
= V
nA
IN_REG
IN_REG(TH)
CC/CV Mode, I = 0
2.5
85
15
mA
μA
μA
SW
Standby Mode
Shutdown (SHDN = 0)
I
I
BOOST Supply Current
Switch On, I = 0,
20
mA
BOOST
SW
(BOOST – SW)
2.5 < V
< 8.5
I
BOOST Switch Drive
I
SW
= 2A
30
350
3
mA/A
mV
A
BOOST/ SW
V
Switch-On Voltage Drop
Switch Current Limit
V
IN
– V , I = 2A
SW SW
SW(ON)
l
I
2.5
SW(MAX)
V
V
V
Precondition Sense Voltage
Maximum Sense Voltage
C/10 Trigger Sense Voltage
BAT Input Bias Current
SENSE Input Bias Current
V
V
V
– V ; V = 2V
15
mV
mV
mV
μA
μA
nA
nA
V
SENSE(PRE)
SENSE(DC)
SENSE(C/10)
BAT
SENSE
SENSE
SENSE
BAT FB
l
l
– V ; V = 3V (Note 7)
95
100
10
105
12.5
1
BAT FB
– V , Falling
7.5
BAT
I
I
I
I
Charging Terminated
Charging Terminated
Charging Terminated
CV Operation (Note 5)
0.1
0.1
65
1
SENSE
V
V
Input Bias Current
Input Bias Current
VFB
FB
FB
110
1.36
0.29
20
VFB
l
l
V
V
V
NTC Range Limit (High)
NTC Range Limit (Low)
NTC Threshold Hysteresis
NTC Disable Impedance
NTC Bias Current
V
NTC
V
NTC
Rising
Falling
1.25
0.27
1.45
NTC(H)
0.315
V
NTC(L)
% of threshold
%
NTC(HYST)
l
l
l
R
Impedance to ground
250
47.5
1.15
500
50
kΩ
μA
V
NTC(DIS)
NTC
I
V
NTC
= 0.8V
52.5
1.25
V
SHDN
Shutdown Threshold
Shutdown Hysteresis
SHDN Input Bias Current
Status Low Voltage
Rising
1.2
120
–10
V
mV
nA
V
SHDN(HYST)
SHDN
I
l
l
V
, V
10mA Load
0.4
CHRG FAULT
I
Charge/Discharge Current
Timer Disable Threshold
25
μA
V
TIMER
V
0.1
0.25
TIMER(DIS)
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3
LT3652HV
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68μF.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
3
MAX
UNITS
hr
t
Full Charge Cycle Timeout
Precondition Timeout
Timer Accuracy
TIMER
22.5
min
%
l
l
–10
15
10
90
f
Operating Frequency
Duty Cycle Range
1
MHz
%
O
DC
Continuous Operation
Note 3: V minimum voltages below the start threshold are only
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.
IN
supported if (V
-V ) > 2V.
BOOST SW
Note 4: This parameter is valid for programmed output battery float
voltages ≤ 4.2V. V operating range minimum is 0.75V above the
IN
programmed output battery float voltage (V
+ 0.75V). V Start
Note 2: The LT3652HV is tested under pulsed load conditions such that
BAT(FLT)
IN
Voltage is 3.3V above the programmed output battery float voltage
(V + 3.3V).
T ≅ T . The LT3652HVE is guaranteed to meet performance specifications
J
A
from 0°C to 85°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization, and correlation with statistical process controls. The
LT3652HVI specifications are guaranteed over the full –40°C to 125°C
operating junction temperature range. High junction temperatures degrade
operating lifetimes; operating lifetime is derated for junction temperatures
greater than 125°C.
BAT(FLT)
Note 5: Output battery float voltage (V ) programming resistor
BAT(FLT)
divider equivalent resistance = 250k compensates for input bias current.
Note 6: All V voltages measured through 250k series resistance.
FB
SENSE(DC)
Note 7: V
approaches 125°C.
is reduced by thermal foldback as junction temperature
3652hvf
4
LT3652HV
TJ = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
VIN Standby Mode Current
vs Temperature
VIN_REG Threshold
VFB Reference Voltage
vs Temperature
vs Temperature: ICHG at 50%
2.720
2.715
2.710
2.705
2.700
2.695
2.690
2.685
2.680
100
95
90
85
80
75
70
65
3.304
3.302
3.300
3.298
3.296
–50
0
25
50
75 100 125
–50
–25
0
25
50
75 100 125
–25
50
–50
0
25
75
100
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3652 G01
3652 G01a
3652 G02
Switch Forward Drop (VIN – VSW
vs Temperature
)
Switch Drive (ISW/IBOOST
vs Switch Current
)
480
36
33
30
27
24
21
18
15
12
9
I
= 2A
SW
460
440
420
400
380
360
340
320
6
3
0
–50
0
25
50
75 100 125
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
–25
TEMPERATURE (°C)
SWITCH CURRENT (A)
3652 G03
3652 G04
C/10 Threshold (VSENSE–VBAT
vs Temperature
)
CC/CV Charging; SENSE Pin Bias
Current vs VSENSE
12
11
10
9
100
50
V
= V
BAT(PRE)
BAT
0
V
= V
BAT(FLT)
–50
BAT
–100
–150
–200
–250
–300
–350
8
–50
0
25
50
75 100 125
–25
0
0.5
1
1.5
2
2.5
(V)
TEMPERATURE (°C)
V
SENSE
3652 G05
3652 G06
3652hvf
5
LT3652HV
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Thermal Foldback – Maximum
Maximum Charge Current
(VSENSE–VBAT) vs Temperature
CC/CV Charging; BAT Pin Bias
Current vs VBAT
Charge Current (VSENSE–VBAT
vs Temperature
)
120
100
80
60
40
20
0
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
101.0
100.8
100.6
100.4
100.2
100.0
99.8
V
= 3V
FB
99.6
99.4
99.2
V
BAT(FLT)
3
99.0
25 35 45 55 65 75 85 95 105 115 125 135
0
0.5
1
1.5
2
2.5
(V)
–50
0
25
50
75 100 125
–25
TEMPERATURE (°C)
V
TEMPERATURE (°C)
BAT
3652 G08
3652 G09
3652 G07
VFLOAT Programming Resistor
Current vs VFLOAT for 2-Resistor
Network
Maximum Charge Current
(VSENSE–VBAT) vs VIN_REG Voltage
12
10
8
100
80
60
40
20
0
6
4
2
0
2.65 2.66 2.67 2.68 2.69 2.7 2.71 2.72 2.73 2.74 2.75
(V)
0
2
4
6
8
10 12 14 16 18
(V)
V
V
IN_REG
BAT(FLT)
3652 G10
3652 G11
Charge Current, Efficiency, and
Power Loss vs Time
(ICHG(MAX) = 2A; VFLOAT = 8.2V)
Charger Efficiency vs Battery
Voltage (ICHG = 2A)
95
85
75
65
55
3.0
2.5
2.0
1.5
1.0
0.5
0
90
88
86
84
82
80
78
76
74
72
70
V
= 20V
IN
EFFICIENCY
POWER
LOSS
CHARGE
CURRENT
45
35
V
= 20V WITH INPUT BLOCKING DIODE
IN
0
20 40 60 80 100 120 140 160 180 200
TIME (MINUTES)
3
4
5
6
7
8
V
9
10 11 12 13 14 15
(V)
BAT
3652 G13
3652 G12
3652hvf
6
LT3652HV
PIN FUNCTIONS
V
(Pin 1): Charger Input Supply. V operating range
batterychargingcycle. Atemperaturefaultcausesthispin
to be pulled low. If the internal timer is used for termina-
tion, a bad battery fault also causes this pin to be pulled
low. If no fault conditions exist, the FAULT pin remains
high-impedance.
IN
IN
is 4.95V to 34V. V must be 3.3V greater than the pro-
IN
grammed output battery float voltage (V
able start-up. (V – V
) for reli-
BAT(FLT)
) ≥ 0.75V is the minimum
IN
BAT(FLT)
operating voltage, provided (V
– V ) ≥ 2V. I
~
VIN
BOOST
SW
85μA after charge termination. This pin is typically con-
nected to the cathode of a blocking diode.
TIMER (Pin 6): End-Of-Cycle Timer Programming Pin.
If a timer-based charge termination is desired, connect
a capacitor from this pin to ground. Full charge end-of-
cycle time (in hours) is programmed with this capacitor
following the equation:
V
(Pin2):InputVoltageRegulationReference.Maxi-
IN_REG
mumchargecurrentisreducedwhenthispinisbelow2.7V.
Connecting a resistor divider from V to this pin enables
programming of minimum operational V voltage. This
IN
6
IN
t
= C
• 4.4 • 10
TIMER
EOC
is typically used to program the peak power voltage for a
solar panel. The LT3652HV servos the maximum charge
current required to maintain the programmed operational
V voltage, through maintaining the voltage on V
A bad battery fault is generated if the battery does not
achieve the precondition threshold voltage within one-
eighth of t , or:
EOC
IN
IN_REG
5
at or above 2.7V. If the voltage regulation feature is not
t
= C
• 5.5 • 10
TIMER
PRE
used, connect the pin to V .
IN
A 0.68μF capacitor is typically used, which generates a
timer EOC at three hours, and a precondition limit time of
22.5 minutes. If a timer-based termination is not desired,
the timer function is disabled by connecting the TIMER
pin to ground. With the timer function disabled, charging
terminates when the charge current drops below a C/10
SHDN (Pin 3): Precision Threshold Shutdown Pin. The
enable threshold is 1.2V (rising), with 120mV of input
hysteresis.Wheninshutdownmode,allchargingfunctions
are disabled. The precision threshold allows use of the
SHDN pin to incorporate UVLO functions. If the SHDN pin
is pulled below 0.4V, the IC enters a low current shutdown
threshold, or I
/10
CHG(MAX)
mode where V currentisreducedto15μA. Typical SHDN
IN
V (Pin7):BatteryFloatVoltageFeedbackReference. The
FB
pin input bias current is 10nA. If the shutdown function
charge function operates to achieve a final float voltage of
is not desired, connect the pin to V .
IN
3.3V on this pin. Output battery float voltage (V
)
BAT(FLT)
can be
CHRG (Pin 4): Open-Collector Charger Status Output;
typically pulled up through a resistor to a reference volt-
age. This status pin can be pulled up to voltages as high
is programmed using a resistor divider. V
programmed up to 18V.
BAT(FLT)
The auto-restart feature initiates a new charging cycle
as V when disabled, and can sink currents up to 10mA
IN
when the voltage at the V pin falls 2.5% below the float
FB
when enabled. During a battery charging cycle, if required
charge current is greater than 1/10 of the programmed
maximum current (C/10), CHRG is pulled low. A tem-
perature fault also causes this pin to be pulled low. After
C/10 charge termination or, if the internal timer is used
for termination and charge current is less than C/10, the
CHRG pin remains high-impedance.
voltage reference.
The V pin input bias current is 110nA. Using a resistor
FB
divider with an equivalent input resistance at the V pin
FB
of 250k compensates for input bias current error.
Required resistor values to program desired V
follow the equations:
BAT(FLT)
FAULT (Pin 5): Open-Collector Charger Status Output;
typically pulled up through a resistor to a reference volt-
age. This status pin can be pulled up to voltages as high
5
R1 = (V
• 2.5 • 10 )/3.3
(Ω)
(Ω)
BAT(FLT)
5
5
R2 = (R1 • 2.5 • 10 )/(R1 - (2.5 • 10 ))
as V when disabled, and can sink currents up to 10mA
IN
R1 is connected from BAT to V , and R2 is connected
FB
when enabled. This pin indicates fault conditions during a
from V to ground.
FB
3652hvf
7
LT3652HV
PIN FUNCTIONS
NTC (Pin 8): Battery Temperature Monitor Pin. This pin is
the input to the NTC (Negative Temperature Coefficient)
thermistortemperaturemonitoringcircuit.Thisfunctionis
enabled by connecting a 10kΩ, B = 3380 NTC thermistor
from the NTC pin to ground. The pin sources 50μA, and
monitors the voltage across the 10kΩ thermistor. When
the voltage on this pin is above 1.36 (T < 0°C) or below
0.29V (T > 40°C), charging is disabled and the CHRG and
FAULT pins are both pulled low. If internal timer termina-
tion is being used, the timer is paused, suspending the
chargingcycle.ChargingresumeswhenthevoltageonNTC
returns to within the 0.29V to 1.36V active region. There
isapproximately5°Coftemperaturehysteresisassociated
with each of the temperature thresholds. The temperature
monitoring function remains enabled while the thermistor
resistance to ground is less than 250k, so if this function
is not desired, leave the NTC pin unconnected.
charge current. The maximum charge current (I
)
CHG(MAX)
corresponds to 100mV across the sense resistor. This
resistor can be set to program maximum charge cur-
rent as high as 2A. The sense resistor value follows the
relation:
R
SENSE
= 0.1/I
(Ω)
CHG(MAX)
Onceachargecycleisterminated, theinputbiascurrentof
the SENSE pin is reduced to < 0.1μA, to minimize battery
discharge while the charger remains connected.
BOOST (Pin 11): Bootstrapped Supply Rail for Switch
Drive.Thispinfacilitatessaturationoftheswitchtransistor.
Connect a 1μF or greater capacitor from the BOOST pin
to the SW pin. Operating range of this pin is 0V to 8.5V,
referenced to the SW pin. The voltage on the decoupling
capacitor is refreshed through a rectifying diode, with
the anode connected to either the battery output voltage
or an external source, and the cathode connected to the
BOOST pin.
BAT (Pin 9): Charger Output Monitor Pin. Connect a
10μF decoupling capacitance (C ) to ground. Depend-
BAT
ing on application requirements, larger value decoupling
capacitors may be required. The charge function operates
to achieve the programmed output battery float voltage
SW (Pin 12): Switch Output Pin. This pin is the output
of the charger switch, and corresponds to the emitter of
the switch transistor. When enabled, the switch shorts
(V
) at this pin. This pin is also the reference for
BAT(FLT)
the SW pin to the V supply. The drive circuitry for this
IN
the current sense voltage. Once a charge cycle is termi-
nated, the input bias current of the BAT pin is reduced to
< 0.1μA, to minimize battery discharge while the charger
remains connected.
switch is bootstrapped above the V supply using the
IN
BOOST supply pin, allowing saturation of the switch for
maximum efficiency. The effective on-resistance of the
boosted switch is 0.175Ω.
SENSE (Pin 10): Charge Current Sense Pin. Connect the
SGND (Pin 13): Ground Reference and Backside Exposed
Lead Frame Thermal Connection. Solder the exposed lead
frame to the PCB ground plane.
inductorsenseresistor(R
)fromtheSENSEpintothe
SENSE
BAT pin. The voltage across this resistor sets the average
3652hvf
8
LT3652HV
BLOCK DIAGRAM
V
+
–
IN_REG
125°C
+
–
STANDBY
UVLO
+
–
T
2.7V
DIE
4.6V
BOOST
+
–
OVLO
V
IN
35V
10mΩ
+
–
R
0.2V
TIMER
LATCH
S
Q
30mV
–
+
OSC
1MHz
+
–
TIMER
OSC.
SW
SENSE
BAT
V
C
R
R
S
S
–
C-EA
STANDBY
+
RIPPLE
COUNTER
OFFSET
COUNT
V
+
–
FB
RESET
–
COUNT
0.3V
V-EA
+
COUNT
MODE
RESET
ENABLE
I
TH
10 × R
S
(TIMER OR C/10)
CHRG
FAULT
CONTROL LOGIC
TERMINATE
STATUS
–
+
C/10
0.1V
–
+
1V
0.15V
PRECONDITION
2.3V
NTC
–
+
SHDN
V
INT
2.7V
x2.25
+
–
–
+
STANDBY
1.2V 3.3V
3.218V
1.36V
TERMINATE
50μA
–
+
0.29V
NTC
3652 BD
+
–
1.3V
0.7V
46μA
3652hvf
9
LT3652HV
APPLICATIONS INFORMATION
Overview
monitor the battery voltage while in standby, and if that
voltage falls 2.5% from the full-charge float voltage, the
LT3652HVengagesanautomaticchargecyclerestart. The
IC also automatically restarts a new charge cycle after a
bad battery fault once the failed battery is removed and
replaced with another battery.
LT3652HV is a complete monolithic, mid-power, multi-
chemistry buck battery charger, addressing high input
voltageapplicationswithsolutionsthatrequireaminimum
of external components. The IC uses a 1MHz constant fre-
quency, average-current mode step-down architecture.
The LT3652HV contains provisions for a battery tem-
perature monitoring circuit. This feature monitors battery
temperature using a thermistor during the charging cycle.
If the battery temperature moves outside a safe charg-
ing range of 0°C to 40°C, the IC suspends charging and
signals a fault condition until the temperature returns to
the safe charging range.
The LT3652HV incorporates a 2A switch that is driven
by a bootstrapped supply to maximize efficiency during
charging cycles. Wide input range allows operation to full
chargefromvoltagesashighas34V. Aprecisionthreshold
shutdown pin allows incorporation of UVLO functionality
using a simple resistor divider. The IC can also be put into
a low-current shutdown mode, in which the input supply
bias is reduced to only 15μA.
TheLT3652HVcontainstwodigitalopen-collectoroutputs,
which provide charger status and signal fault conditions.
These binary-coded pins signal battery charging, standby
or shutdown modes, battery temperature faults, and bad
battery faults.
The LT3652HV employs an input voltage regulation loop,
which reduces charge current if a monitored input voltage
falls below a programmed level. When the LT3652HV is
powered by a solar panel, the input regulation loop is used
to maintain the panel at peak output power.
General Operation (See Block Diagram)
TheLT3652HVautomaticallyentersabatteryprecondition
modeifthesensedbatteryvoltageisverylow.Inthismode,
the charge current is reduced to 15% of the programmed
The LT3652HV uses average current mode control loop
architecture, such that the IC servos directly to average
charge current. The LT3652HV senses charger output
maximum, as set by the inductor sense resistor, R
.
SENSE
voltage through a resistor divider via the V pin. The
FB
Once the battery voltage reaches 70% of the fully charged
float voltage, the IC automatically increases maximum
charge current to the full programmed value.
difference between the voltage on this pin and an internal
3.3V voltage reference is integrated by the voltage error
amplifier (V-EA). This amplifier generates an error volt-
The LT3652HV can use a charge-current based C/10
termination scheme, which ends a charge cycle when
the battery charge current falls to one tenth of the pro-
grammed maximum charge current. The LT3652HV also
contains an internal charge cycle control timer, for timer-
based termination. When using the internal timer, the
IC combines C/10 detection with a programmable time
constraint, during which the charging cycle can continue
beyond the C/10 level to top-off a battery. The charge
cycle terminates when a specific time elapses, typically 3
hours. When the timer-based scheme is used, the IC also
supports bad battery detection, which triggers a system
fault if a battery stays in precondition mode for more than
one eighth of the total charge cycle time.
age on its output (I ), which corresponds to the average
TH
current sensed across the inductor current sense resistor,
R
, which is connected between the SENSE and BAT
SENSE
pins. The I voltage is then divided down by a factor of
TH
10, and imposed on the input of the current error amplifier
(C-EA). The difference between this imposed voltage and
the current sense resistor voltage is integrated, with the
resultingvoltage(V )usedasathresholdthatiscompared
C
against an internally generated ramp. The output of this
comparison controls the charger’s switch.
The I error voltage corresponds linearly to average
TH
current sensed across the inductor current sense resistor,
allowing maximum charge current control by limiting the
effective voltage range of I . A clamp limits this voltage
TH
Once charging is terminated, the LT3652HV automati-
cally enters a low-current standby mode where supply
bias currents are reduced to 85μA. The IC continues to
to 1V which, in turn, limits the current sense voltage to
100mV. This sets the maximum charge current, or the
current delivered while the charger is operating in con-
3652hvf
10
LT3652HV
APPLICATIONS INFORMATION
stant-current (CC) mode, which corresponds to 100mV
remains in (or enters) precondition mode after 1/8th of
the programmed charge cycle time. A bad battery fault
halts the charging cycle, the CHRG status pin goes high-
impedance, and the FAULT pin is pulled low.
across R
. The I voltage is pulled down to reduce
SENSE
TH
this maximum charge current should the voltage on the
pin falls below 2.7V (V ) or the die tem-
V
IN_REG
IN_REG(TH)
perature approaches 125°C.
When the LT3652HV terminates a charging cycle, whether
through C/10 detection or by reaching timer EOC, the
average current mode analog loop remains active, but
the internal float voltage reference is reduced by 2.5%.
Because the voltage on a successfully charged battery is
at the full float voltage, the voltage error amp detects an
If the voltage on the V pin is below 2.3V (V
),
FB(PRE)
FB
the LT3652HV engages precondition mode. During the
precondition interval, the charger continues to operate in
constant-current mode, but the maximum charge current
is reduced to 15% of the maximum programmed value
as set by R
.
over-voltage condition and I is pulled low. When the
SENSE
TH
voltage error amp output drops below 0.3V, the IC enters
Whenthechargeroutputvoltageapproachesthefloatvolt-
age,orthevoltageontheV pinapproaches3.3V(V ),
standby mode, where most of the internal circuitry is dis-
FB
FB(FLT)
abled, and the V bias current is reduced to 85μA. When
IN
the charger transitions into constant-voltage (CV) mode
the voltage on the V pin drops below the reduced float
FB
and charge current is reduced from the maximum value.
reference level, the output of the voltage error amp will
climb, at which point the IC comes out of standby mode
and a new charging cycle is initiated.
As this occurs, the I voltage falls from the limit clamp
TH
and servos to lower voltages. The IC monitors the I volt-
TH
age as it is reduced, and detection of C/10 charge current
is achieved when I = 0.1V. If the charger is configured
TH
V Input Supply
IN
for C/10 termination, this threshold is used to terminate
the charge cycle. Once the charge cycle is terminated,
the CHRG status pin becomes high-impedance and the
charger enters low-current standby mode.
The LT3652HV is biased through a reverse-current block-
ing element from the charger input supply to the V pin.
IN
This supply provides large switched currents, so a high-
quality, low ESR decoupling capacitor is recommended
TheLT3652HVcontainsaninternalchargecycletimerthat
terminates a successful charge cycle after a programmed
amount of time. This timer is typically programmed to
achieve end-of-cycle (EOC) in 3 hours, but can be con-
figured for any amount of time by setting an appropriate
to minimize voltage glitches on V . The V decoupling
IN
IN
capacitor (C ) absorbs all input switching ripple current
VIN
in the charger, so it must have an adequate ripple current
rating. RMS ripple current (I
) is:
CVIN(RMS)
timing capacitor value (C ). When timer termination
TIMER
is used, the charge cycle does not terminate when C/10
is achieved. Because the CHRG status pin responds to
the C/10 current level, the IC will indicate a fully-charged
battery status, but the charger continues to source low
currents into the battery until the programmed EOC time
has elapsed, at which time the charge cycle will terminate.
AtEOCwhenthechargingcycleterminates,ifthebatterydid
notachieveatleast97.5%ofthefullfloatvoltage,charging
is deemed unsuccessful, the LT3652HV re-initiates, and
charging continues for another full timer cycle.
1/2
I
≅I
• (V / V )•([V / V ] – 1) ,
CVIN(RMS) CHG(MAX) BAT IN IN BAT
where I
(100mV/R
V = 2 • V , where:
IN
is the maximum average charge current
). The above relation has a maximum at
CHG(MAX)
SENSE
BAT
I
= I
/2.
CHG(MAX)
CVIN(RMS)
Use of the timer function also enables bad-battery detec-
tion. This fault condition is achieved if the battery does
not respond to preconditioning, such that the charger
The simple worst-case of ½ • I
used for design.
is commonly
CHG(MAX)
3652hvf
11
LT3652HV
APPLICATIONS INFORMATION
Bulk capacitance is a function of desired input ripple volt-
The voltage on the decoupling capacitor is refreshed
through a diode, with the anode connected to either the
battery output voltage or an external source, and the
cathode connected to the BOOST pin. Rate the diode
average current greater than 0.1A, and reverse voltage
age (ΔV ), and follows the relation:
IN
C
= I
• (V /V ) / ΔV (μF)
CHG(MAX) BAT IN IN
IN(BULK)
greater than V
.
IN(MAX)
Input ripple voltages above 0.1V are not recommended.
10μF is typically adequate for most charger applica-
tions.
To refresh the decoupling capacitor with a rectifying diode
from the battery with battery float voltages higher than
8.4V, a >100mA Zener diode can be put in series with
the rectifying diode to prevent exceeding the BOOST pin
operating voltage range.
Charge Current Programming
The LT3652HV charger is configurable to charge at aver-
age currents as high as 2A. Maximum charge current is
set by choosing an inductor sense resistor (R
) such
SENSE
that the desired maximum average current through that
sense resistor creates a 100mV drop, or:
SW
LT3652HV
BOOST
SENSE
R
= 0.1 / I
CHG(MAX)
SENSE
BAT
where I
is the maximum average charge current.
CHG(MAX)
3652 F02
A 2A charger, for example, would use a 0.05Ω sense
resistor.
BOOST Supply
Figure 2. Zener Diode Reduces Refresh
Voltage for BOOST Pin
The BOOST bootstrapped supply rail drives the internal
switch and facilitates saturation of the switch transistor.
Operating range of the BOOST pin is 0V to 8.5V, as refer-
enced to the SW pin. Connect a 1μF or greater capacitor
from the BOOST pin to the SW pin.
V / BOOST Start-Up Requirement
IN
The LT3652HV operates with a V range of 4.95V to 34V,
IN
however, a start-up voltage requirement exists due to
the nature of the non-synchronous step-down switcher
topology used for the charger. If there is no BOOST supply
SW
available, the internal switch requires (V – V ) ≥ 3.3V
IN
SW
LT3652HV
to reliably operate. This requirement does not exist if the
BOOST
SENSE
BOOST supply is available and (V – V ) > 2V.
BOOST
SW
When an LT3652HV charger is not switching, the SW pin
is at the same potential as the battery, which can be as
R
SENSE
BAT
high as V
. As such, for reliable start-up, the V
BAT(FLT)
IN
3652 F01
supplymustbeatleast3.3VaboveV
. Onceswitch-
BAT(FLT)
ing begins and the BOOST supply capacitor gets charged
such that (V – V ) > 2V, the V requirement no
BOOST
longer applies.
SW
IN
Figure 1. Programming Maximum Charge
Current Using RSENSE
3652hvf
12
LT3652HV
APPLICATIONS INFORMATION
InlowV applications, theBOOSTsupplycanbepowered
V is the forward voltage of the rectifying Schottky diode.
IN
F
by an external source for start-up, eliminating the V
start-up requirement.
Ripple current is typically set within a range of 25% to
IN
35% of I
, so an inductor value can be determined
CHG(MAX)
by setting 0.25 < ΔI
< 0.35.
MAX
V
Output Decoupling
BAT
24
22
20
18
16
14
12
10
8
AnLT3652HVchargeroutputrequiresbypasscapacitance
connected from the BAT pin to ground (C ). A 10μF
BAT
ceramiccapacitorisrequiredforallapplications.Insystems
where the battery can be disconnected from the charger
output, additional bypass capacitance may be desired for
visual indication for a no-battery condition (see the Status
Pins section).
If it is desired to operate a system load from the LT3652HV
chargeroutputwhenthebatteryisdisconnected,additional
bypass capacitance is required. In this type of application,
excessive ripple and/or low amplitude oscillations can oc-
cur without additional output bulk capacitance. For these
applications,placea100μFlowESRnon-ceramiccapacitor
(chip tantalum or organic semiconductor capacitors such
as Sanyo OS-CONs or POSCAPs) from BAT to ground,
in parallel with the 10μF ceramic bypass capacitor. This
additional bypass capacitance may also be required in
systems where the battery is connected to the charger
6
4
18 20 22 24 26 28 30 32 34
MAXIMUM OPERATIONAL V VOLTAGE (V)
IN
3652 F03
Figure 3. 14.4V at 1.5A Switched Inductor Values
Magnetics vendors typically specify inductors with
maximum RMS and saturation current ratings. Select an
inductorthathasasaturationcurrentratingatorabove(1+
ΔI
/2) • I
, and an RMS rating above I
.
with long wires. The voltage rating of C must meet or
MAX
CHG(MAX)
CHG(MAX)
BAT
Inductorsmustalsomeetamaximumvolt-secondproduct
requirement. If this specification is not in the data sheet of
aninductor,consultthevendortomakesurethemaximum
volt-secondproductisnotbeingexceededbyyourdesign.
The minimum required volt-second product is:
exceed the battery float voltage.
Inductor Selection
The primary criterion for inductor value selection in an
LT3652HV charger is the ripple current created in that
inductor. Once the inductance value is determined, an
inductor must also have a saturation current equal to or
exceeding the maximum peak current in the inductor. An
inductor value (L), given the desired amount of ripple cur-
V
• (1 – V
/V
) (V • μS)
BAT(FLT)
BAT(FLT) IN(MAX)
Rectifier Selection
TherectifierdiodefromSWtoGND, inaLT3652HVbattery
charger provides a current path for the inductor current
when the main power switch is disabled. The rectifier is
selectedbaseduponforwardvoltage, reversevoltage, and
maximum current. A Schottky diode is required, as low
forward voltage yields the lowest power loss and highest
efficiency. The rectifier diode must be rated to withstand
rent (ΔI
) can be approximated using the relation:
MAX
L = (10 R
[1 – (V
/ ΔI
) • V
•
SENSE
MAX
BAT(FLT)
/ V
)] (μH)
IN(MAX)
BAT(FLT)
reverse voltages greater than the maximum V voltage.
IN
In the above relation, ΔI
is the normalized ripple cur-
MAX
rent, V
is the maximum operational voltage, and
IN(MAX)
3652hvf
13
LT3652HV
APPLICATIONS INFORMATION
The minimum average diode current rating (I
)
),
Because the battery voltage is across the V
pro-
BAT(FLT)
DIODE(MAX)
is calculated with maximum output current (I
gramming resistor divider, this divider will draw a small
amount of current from the battery (I ) at a rate of:
CHG(MAX)
maximum operational V , and output at the precondition
IN
RFB
threshold (V
, or 0.7 • V
):
BAT(PRE)
BAT(FLT)
I
= 3.3 / R
FB2
RFB
I
> I
• (V
– V
) / V
) (A)
DIODE(MAX) CHG(MAX)
IN(MAX)
BAT(PRE)
IN(MAX)
Precision resistors in high values may be hard to ob-
tain, so for some lower V applications, it may be
BAT(FLT)
desirable to use smaller-value feedback resistors with an
For example, a rectifier diode for a 7.2V, 2A charger with
a 25V maximum input voltage would require:
additional resistor (R ) to achieve the required 250k
FB3
equivalent resistance. The resulting 3-resistor network,
as shown in Figure 5, can ease component selection
and/orincreaseoutputvoltageprecision,attheexpenseof
additional current through the feedback divider.
I
I
> 2 • (25 – 0.7[7.2]) / 25), or
> 1.6A
DIODE(MAX)
DIODE(MAX)
Battery Float Voltage Programming
BAT
+
Theoutputbatteryfloatvoltage(V
)isprogrammed
LT3652HV
BAT(FLT)
R
R
FB1
FB2
R
FB3
by connecting a resistor divider from the BAT pin to V .
FB
V
FB
V
can be programmed up to 18V.
BAT(FLT)
3652 F05
BAT
+
Figure 5. A Three-Resistor Feedback Network Can
Ease Component Selection
LT3652HV
R
R
FB1
FB2
V
FB
3652 F04
For a three-resistor network, R
relation:
and R
follow the
FB1
FB2
Figure 4. Feedback Resistors from BAT to VFB
Program Float Voltage
R
/R = 3.3/(V
FB2 FB1
– 3.3)
BAT(FLT)
Example:
For V
= 3.6V:
BAT(FLT)
Usingaresistordividerwithanequivalentinputresistance
at the V pin of 250k compensates for input bias current
FB
R
/R = 3.3/(3.6 - 3.3) = 11.
FB2 FB1
error.RequiredresistorvaluestoprogramdesiredV
BAT(FLT)
Setting divider current (I ) = 10μA yields:
RFB
follow the equations:
R
= 3.3/10μA
FB2
R
= 330k
5
FB2
R
R
= (V
• 2.5 • 10 ) / 3.3
(Ω)
(Ω)
FB1
BAT(FLT)
Solving for R
:
5
5
FB1
= (R1 • (2.5 • 10 )) / (R1- (2.5 • 10 ))
FB2
R
= 330k/11
FB1
R
= 30k
FB1
The charge function operates to achieve the final float
voltage of 3.3V on the V pin. The auto-restart feature
The divider equivalent resistance is:
||R = 27.5k
FB
initiates a new charging cycle when the voltage at the V
pin falls 2.5% below that float voltage.
FB
R
FB1 FB2
3652hvf
14
LT3652HV
APPLICATIONS INFORMATION
To satisfy the 250k equivalent resistance to the V
pin:
If the voltage regulation feature is not used, connect the
FB
V
pin to V .
IN_REG
IN
R
= 250k − 27.5k
FB3
INPUT
SUPPLY
V
IN
R
= 223k.
FB3
LT3652HV
R
R
IN1
IN2
Because the V pin is a relatively high impedance node,
FB
V
IN_REG
stray capacitances at this pin must be minimized. Special
attention should be given to any stray capacitances that
can couple external signals onto the pin, which can pro-
duce undesirable output transients or ripple. Effects of
parasitic capacitance can typically be reduced by adding
a small-value (20pF to 50pF) feedforward capacitor from
3652 F06
Figure 6. Resistor Divider Sets Minimum VIN
MPPT Temperature Compensation
the BAT pin to the V pin.
FB
Atypicalsolarpaneliscomprisedofanumberofseries-con-
nectedcells,eachcellbeingaforward-biasedp-njunction.
Extra care should be taken during board assembly. Small
amounts of board contamination can lead to significant
shifts in output voltage. Appropriate post-assembly board
cleaning measures should be implemented to prevent
board contamination, and low-leakage solder flux is
recommended.
As such, the open-circuit voltage (V ) of a solar cell has
OC
a temperature coefficient that is similar to a common p-n
diode, or about –2mV/°C. The peak power point voltage
(V ) for a crystalline solar panel can be approximated as
MP
a fixed voltage below V , so the temperature coefficient
OC
for the peak power point is similar to that of V .
OC
Input Supply Voltage Regulation
Panel manufacturers typically specify the 25°C values for
TheLT3652HVcontainsavoltagemonitorpinthatenables
programming a minimum operational voltage. Connect-
V , V , and the temperature coefficient for V , making
OC MP
OC
determination of the temperature coefficient for V of a
MP
ing a resistor divider from V to the V
pin enables
IN
IN_REG
typical panel straight forward.
programming of minimum input supply voltage, typically
The LT3652HV employs a feedback network to program
used to program the peak power voltage for a solar panel.
Maximum charge current is reduced when the V
is below the regulation threshold of 2.7V.
the V input regulation voltage. Manipulation of the
IN
pin
IN_REG
network makes for efficient implementation of various
temperature compensation schemes for a maximum peak
If an input supply cannot provide enough power to satisfy
therequirementsofanLT3652HVcharger, thesupplyvolt-
agewillcollapse.Aminimumoperatingsupplyvoltagecan
thus be programmed by monitoring the supply through
a resistor divider, such that the desired minimum voltage
V
TEMP CO.
OC
V
OC
V
OC(25°C)
corresponds to 2.7V at the V
pin. The LT3652HV
IN_REG
servos the maximum output charge current to maintain
the voltage on V at or above 2.7V.
V
MP(25°C)
V
– V
MP
V
IN_REG
OC
MP
Programming of the desired minimum voltage is ac-
complished by connecting a resistor divider as shown in
Figure 6. The ratio of R /R for a desired minimum
IN1 IN2
5
15
25
35
45
55
voltage (V
) is:
TEMPERATURE (°C)
IN(MIN)
3652 F07
R
/R = (V
/2.7) – 1
Figure 7. Temperature Characteristics for Solar Panel
Output Voltage
IN1 IN2
IN(MIN)
3652hvf
15
LT3652HV
APPLICATIONS INFORMATION
Battery Voltage Temperature Compensation
power tracking (MPPT) application. As the temperature
characteristicforatypicalsolarpanelV voltageishighly
MP
Some battery chemistries have charge voltage require-
ments that vary with temperature. Lead-acid batteries in
particular experience a significant change in charge volt-
age requirements as temperature changes. For example,
manufacturers of large lead-acid batteries recommend
a float charge of 2.25V/cell at 25°C. This battery float
voltage, however, has a temperature coefficient which is
typically specified at –3.3mV/°C per cell.
linear, asimplesolutionfortrackingthatcharacteristiccan
be implemented using an LM234 3-terminal temperature
sensor. This creates an easily programmable, linear tem-
perature dependent characteristic.
In the circuit shown in figure 8,
V
IN
LM234
R
+
–
V
V
In a manner similar to the MPPT temperature correction
outlined previously, implementation of linear battery
charge voltage temperature compensation can be ac-
complished by incorporating an LM234 into the output
feedback network.
R
IN1
IN2
V
IN
R
SET
V
IN_REG
R
LT3652HV
For example, a 6-cell lead acid battery has a float charge
voltage that is commonly specified at 2.25V/cell at 25°C,
or13.5V,anda–3.3mV/°Cpercelltemperaturecoefficient,
or –19.8mV/°C. Using the feedback network shown in
Figure 9, with the desired temperature coefficient (TC)
3658 F08
Figure 8. MPPT Temperature Compensation Network
R
IN1
= –R • (TC • 4405), and
SET
R
= R /({[V
+ R • (0.0674/R )]/V
} – 1)
IN2
IN1
MP(25°C)
IN1
SET
IN_REG
BAT
Where: TC = temperature coefficient (in V/°C), and
= maximum power voltage at 25°C
LM234
+
V
V
MP(25°C)
R
FB1
R
+
LT3652HV
210k
–
R
SET
V
2.4k
For example, given a common 36-cell solar panel that has
the following specified characteristics:
V
FB
6-CELL
LEAD-ACID
BATTERY
R
FB3
215k
R
FB2
43k
Open Circuit Voltage (V ) = 21.7V
OC
3652 F09a
Maximum Power Voltage (V ) = 17.6V
MP
14.3
14.2
14.0
13.8
13.6
13.4
13.2
13.0
12.8
12.6
Open-Circuit Voltage Temperature Coefficient (V ) =
OC
–78mV/°C
–19.8mV/°C
As the temperature coefficient for V is similar to that
MP
of V , the specified temperature coefficient for V
OC
OC
(TC) of –78mV/°C and the specified peak power voltage
(V ) of 17.6V can be inserted into the equations to
MP(25°C)
calculate the appropriate resistor values for the tempera-
ture compensation network in Figure 8. With R
to 1000Ω, then:
equal
SET
–10
0
10
20
30
40
50
60
R
R
R
= 1k
SET
IN1
IN2
TEMPERATURE (°C)
3652 F09b
= –1k • (–0.078 • 4405 ) = 344k
Figure 9. Lead-Acid 6-Cell Float Charge Voltage vs
= 344k/({[17.6 + 344k • (0.0674/1k)]/2.7} – 1)
= 24.4k
Temperature Has –19.8mV/°C Characteristic Using LM234 with
Feedback Network
3652hvf
16
LT3652HV
APPLICATIONS INFORMATION
and 25°C float voltage (V
) specified, and using
SET
Status Pins
FLOAT(25°C)
a convenient value of 2.4k for R , necessary resistor
The LT3652HV reports charger status through two open
values follow the relations:
collector outputs, the CHRG and FAULT pins. These pins
R
FB1
= –R • (TC • 4405)
can accept voltages as high as V , and can sink up to
SET
IN
10mA when enabled.
= –2.4k • (–0.0198 • 4405) = 210k
The CHRG pin indicates that the charger is delivering
current at greater that a C/10 rate, or 1/10th of the pro-
grammedmaximumchargecurrent.TheFAULT pinsignals
bad battery and NTC faults. These pins are binary coded,
and signal following the table below, where ON indicates
pin pulled low, and OFF indicates pin high-impedance:
R
= R / ({[V
+ R • (0.0674/
FB1
FB2
FB1
R
FLOAT(25°C)
)] / V } – 1)
SET
FB
= 210k/({[13.5 + 210k • (0.0674/2.4k)]/3.3} – 1)
= 43k
R
= 250k - R ||R
FB1 FB2
FB3
= 250k – 210k||43k = 215k (see the Battery Float
Voltage Programming section)
STATUS PINS STATE
CHRG
FAULT
CHARGER STATUS
While the circuit in Figure 9 creates a linear temperature
characteristic that follows a typical –3.3mV/°C per cell
lead-acidspecification,thetheoreticalfloatchargevoltage
characteristic is slightly nonlinear. This nonlinear charac-
OFF
OFF
OFF
ON
Not Charging — Standby or Shutdown Mode
Bad Battery Fault (Precondition Timeout / EOC
Failure)
–5
2
ON
ON
OFF
ON
Normal Charging at C/10 or Greater
NTC Fault (Pause)
teristic follows the relation V
= 4 × 10 (T )
FLOAT(1-CELL)
–3
– 6 × 10 (T) + 2.375 (with a 2.18V minimum), where
T = temperature in °C. A thermistor-based network can
be used to approximate the nonlinear ideal temperature
characteristic across a reasonable operating range, as
shown in Figure 10.
If the battery is removed from an LT3652HV charger that
is configured for C/10 termination, a sawtooth waveform
14.8
14.6
14.4
14.2
BAT
6-CELL
LEAD-ACID
BATTERY
196k
69k
+
LT3652HV
14.0
THEORETICAL V
FLOAT
198k
13.8
13.6
13.4
13.2
22k
B = 3380
V
FB
69k
PROGRAMMED V
BAT(FLOAT)
3652 F10a
13.0
12.8
–10
0
10
20
30
40
50
60
TEMPERATURE (°C)
3652 F10b
Figure 10. Thermistor-Based Temperature Compensation Network Programs VFLOAT to Closely Match Ideal
Lead-Acid Float Charge Voltage for 6-Cell Charger
3652hvf
17
LT3652HV
APPLICATIONS INFORMATION
of approximately 100mV appears at the charger output,
due to cycling between termination and recharge events,
This cycling results in pulsing at the CHRG output. An
LED connected to this pin will exhibit a blinking pattern,
indicating to the user that a battery is not present. The
frequency of this blinking pattern is dependent on the
output capacitance.
on C
C
following the relation:
TIMER
–7
= T
• 2.27 x 10
(Hours)
TIMER
EOC
Timer EOC is typically set to 3 hours, which requires a
0.68μF capacitor.
C/10 Termination
TheCHRGstatuspincontinuestosignalchargingataC/10
rate,regardlessofwhatterminationschemeisused.When
timer termination is used, the CHRG status pin is pulled
lowduringachargingcycleuntilthechargeroutputcurrent
falls below the C/10 threshold. The charger continues to
top-off the battery until timer EOC, when the LT3652HV
terminates the charging cycle and enters standby mode.
The LT3652HV supports a low-current based termination
scheme,whereabatterychargecycleterminateswhenthe
current output from the charger falls to below one-tenth
of the maximum current, as programmed with R
The C/10 threshold current corresponds to 10mV across
.
SENSE
R
. This termination mode is engaged by shorting
SENSE
the TIMER pin to ground.
Termination at the end of the timer cycle only occurs if
the charging cycle was successful. A successful charge
cycle is when the battery is charged to within 2.5% of the
full-chargefloatvoltage. Ifachargecycleisnotsuccessful
at EOC, the timer cycle resets and charging continues for
another full timer cycle.
When C/10 termination is used, a LT3652HV charger will
sourcebatterychargecurrentaslongastheaveragecurrent
level remains above the C/10 threshold. As the full-charge
float voltage is achieved, the charge current falls until
the C/10 threshold is reached, at which time the charger
terminates and the LT3652HV enters standby mode. The
CHRG status pin follows the charger cycle, and is high
impedance when the charger is not actively charging.
When V
drops below 97.5% of the full-charge float
BAT
voltage, whether by battery loading or replacement of the
battery, the charger automatically reengages and starts
charging.
When V
drops below 97.5% of the full-charged float
BAT
voltage, whether by battery loading or replacement of the
battery, the charger automatically re-engages and starts
charging.
Preconditioning and Bad Battery Fault
A LT3652HV has a precondition mode, where charge cur-
rent is limited to 15% of the programmed I
, as
CHG(MAX)
There is no provision for bad battery detection if C/10
termination is used.
set by R
. The precondition current corresponds to
SENSE
SENSE
15mV across R
.
Timer Termination
Precondition mode is engaged while the voltage on the
pin is below the precondition threshold (2.3V, or
V
TheLT3652HVsupportsatimerbasedterminationscheme,
inwhichabatterychargecycleisterminatedafteraspecific
amount of time elapses. Timer termination is engaged
when a capacitor (C
pin to ground. The timer cycle EOC (T ) occurs based
FB
0.7 • V
). Once the V voltage rises above the
BAT(FLT)
FB
precondition threshold, normal full-current charging can
commence.TheLT3652HVincorporates70mVofthreshold
hysteresis to prevent mode glitching.
) is connected from the TIMER
TIMER
EOC
3652hvf
18
LT3652HV
APPLICATIONS INFORMATION
Whentheinternaltimerisusedfortermination,badbattery
detection is engaged. There is no provision for bad battery
detection if C/10 termination is used. A bad battery fault
If higher operational charging temperatures are desired,
the temperature range can be expanded by adding series
resistance to the 10k NTC resistor. Adding a 0.91k resistor
will increase the effective hot temperature to 45°C.
is triggered when the voltage on V remains below the
FB
precondition threshold for greater than 1/8 of a full timer
cycle (1/8 EOC). A bad battery fault is also triggered if a
normally charging battery re-enters precondition mode
after 1/8 EOC.
During an NTC fault, charging is halted and both status
pins are pulled low. If timer termination is enabled, the
timer count is suspended and held until the fault condi-
tion is relieved.
When a bad battery fault is triggered, the charging cycle
is suspended, so the CHRG status pin becomes high-
impedance. The FAULT pin is pulled low to signal a fault
detection.
Thermal Foldback
The LT3652HV contains a thermal foldback protection
feature that reduces maximum charger output current if
the IC junction temperature approaches 125°C. In most
cases, on-chip temperatures servo such that any exces-
sive temperature conditions are relieved with only slight
reductions in maximum charger current.
Cycling the charger’s power or SHDN function initiates
a new charging cycle, but a LT3652HV charger does not
require a reset. Once a bad battery fault is detected, a new
timerchargingcycleinitiateswhentheV pinexceedsthe
FB
precondition threshold voltage. During a bad battery fault,
0.5mA is sourced from the charger, so removing the failed
battery allows the charger output voltage to rise and initi-
ate a charge cycle reset. As such, removing a bad battery
resets the LT3652HV, so a new charge cycle is started by
connecting another battery to the charger output.
In some cases, the thermal foldback protection feature
can reduce charger currents below the C/10 threshold. In
applications that use C/10 termination (TIMER=0V), the
LT3652HV will suspend charging and enter standby mode
until the excessive temperature condition is relieved.
Layout Considerations
Battery Temperature Monitor and Fault
The LT3652HV switch node has rise and fall times that are
typicallylessthan10nStomaximizeconversionefficiency.
The switch node (Pin SW) trace should be kept as short
as possible to minimize high frequency noise. The input
The LT3652HV can accommodate battery temperature
monitoringbyusinganNTC(negativetemperatureco-effi-
cient)thermistorclosetothebatterypack.Thetemperature
monitoring function is enabled by connecting a 10kΩ,
B=3380NTCthermistorfromtheNTCpintoground.Ifthe
NTC function is not desired, leave the pin unconnected.
capacitor(C )shouldbeplacedclosetotheICtominimize
IN
this switching noise. Short, wide traces on these nodes
also help to avoid voltage stress from inductive ringing.
The BOOST decoupling capacitor should also be in close
proximity to the IC to minimize inductive ringing. The
SENSE and BAT traces should be routed together, and
The NTC pin sources 50μA, and monitors the voltage
dropped across the 10kΩ thermistor. When the voltage
on this pin is above 1.36V (0°C) or below 0.29V (40°C),
the battery temperature is out of range, and the LT3652HV
triggersanNTCfault.TheNTCfaultconditionremainsuntil
the voltage on the NTC pin corresponds to a temperature
withinthe0°Cto40°Crange. Bothhotandcoldthresholds
incorporate hysteresis that correspond to 5°C.
these and the V trace should be kept as short as pos-
FB
sible. Shielding these signals from switching noise with
a ground plane is recommended.
3652hvf
19
LT3652HV
APPLICATIONS INFORMATION
tive terminal. When the switch is disabled (loop #2), the
current to the battery positive terminal is provided from
High current paths and transients should be kept iso-
lated from battery ground, to assure an accurate output
voltage reference. Effective grounding can be achieved
by considering switched current in the ground plane,
and careful component placement and orientation can
effectively steer these high currents such that the battery
reference does not get corrupted. Figure 11 illustrates an
effective grounding scheme using component placement
to control ground currents. When the switch is enabled
(loop #1), current flows from the input bypass capacitor
ground through the freewheeling Schottky diode (D ). In
F
both cases, these switch currents return to ground via the
output bypass capacitor (C ).
BAT
The LT3652HV packaging has been designed to efficiently
remove heat from the IC via the Exposed Pad on the
backside of the package, which is soldered to a copper
footprint on the PCB. This footprint should be made as
large as possible to reduce the thermal resistance of the
IC case to ambient air.
(C ) through the switch and inductor to the battery posi-
IN
C
C
V
BAT
IN
BAT
R
SENSE
1
2
D
F
GND
+
SW
V
IN
LT3652HV
SENSE
BAT
V
FB
3652 F11
Figure 11. Component Orientation Isolates High Current Paths
from Sensitive Nodes
3652hvf
20
LT3652HV
TYPICAL APPLICATIONS
2A Solar Panel Power Manager With 7.2V LiFePO4 Battery
Solar Panel Input Voltage Regulation,
Tracks Max Power Point to
Greater Than 98%
and 17V Peak Power Tracking
CMSH1-40MA
10μF
22
SOLAR
PANEL INPUT
(<40V OC
T = 25°C
A
SYSTEM LOAD
CMSH3-40MA
CMSH3-40MA
20
18
16
14
12
10
VOLTAGE)
530k
100k
100% TO 98% PEAK POWER
98% TO 95% PEAK POWER
SW
V
IN
LT3652HV
IN_REG
1μF
10μH
0.05
V
BOOST
SENSE
BAT
SHDN
CHRG
FAULT
TIMER
10μF
542k
NTC
V
FB
459k
0.2
0.6 0.8
1
1.2 1.4 1.6 1.8
2
0.4
CHARGER OUTPUT CURRENT (A)
+
10k
B = 3380
3652 TA03
2-CELL LiFePO (2 × 3.6V) BATTERY PACK
4
3652 TA02
Basic 2A 1-Cell LiFePO4 Charger (3.6V Float) with C/10 Termination
CMSH3-40MA
CMSH3-40MA
V
IN
6V TO 34V (40V MAX)
SW
V
IN
LT3652HV
IN_REG
CMDSH2-4L
1μF
5.6μH
0.05
V
BOOST
SENSE
BAT
SYSTEM
LOAD
SHDN
CHRG
FAULT
TIMER
10μF
C3
10μF
30k
NTC
+
V
FB
223k
3652 TA05
330k
LiFePO CELL
4
3652hvf
21
LT3652HV
PACKAGE DESCRIPTION
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
0.70 ±0.05
2.38 ±0.05
1.65 ±0.05
3.50 ±0.05
2.10 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.45 BSC
2.25 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
R = 0.115
0.40 ± 0.10
TYP
7
12
2.38 ±0.10
3.00 ±0.10
(4 SIDES)
1.65 ±0.10
PIN 1 NOTCH
PIN 1
TOP MARK
R = 0.20 OR
0.25 × 45°
CHAMFER
(SEE NOTE 6)
6
1
0.23 ± 0.05
0.45 BSC
0.75 ±0.05
0.200 REF
2.25 REF
(DD12) DFN 0106 REV A
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
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 AND TIE BARS SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3652hvf
22
LT3652HV
PACKAGE DESCRIPTION
MSE Package
12-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1666 Rev B)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 p 0.102
(.112 p .004)
2.845 p 0.102
(.112 p .004)
0.889 p 0.127
(.035 p .005)
1
6
0.35
REF
5.23
(.206)
MIN
1.651 p 0.102
(.065 p .004)
3.20 – 3.45
(.126 – .136)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
DETAIL “B”
12
4.039 p 0.102
7
NO MEASUREMENT PURPOSE
0.65
(.0256)
BSC
0.42 p 0.038
(.0165 p .0015)
(.159 p .004)
TYP
(NOTE 3)
0.406 p 0.076
RECOMMENDED SOLDER PAD LAYOUT
(.016 p .003)
12 11 10 9 8 7
REF
DETAIL “A”
0.254
(.010)
3.00 p 0.102
(.118 p .004)
(NOTE 4)
0o – 6o TYP
4.90 p 0.152
(.193 p .006)
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
1
2 3 4 5 6
DETAIL “A”
0.86
(.034)
REF
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 p 0.0508
(.004 p .002)
MSOP (MSE12) 0608 REV B
0.650
(.0256)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
3652hvf
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresenta-
t ion t h a t t he in ter c onne c t ion o f i t s cir cui t s a s de s cr ib e d her ein w ill no t in fr inge on ex is t ing p a ten t r igh t s.
23
LT3652HV
TYPICAL APPLICATION
1A Solar Panel Powered 3-Stage 12V Lead-Acid Fast/Float Charger; 1A Charger Fast Charges with CC/CV
Characteristics Up to 14.4V; When Charge Current Falls to 0.1A Charger Switches to 13.5V Float Charge Mode;
Charger Re-Initiates 14.4V Fast Charge Mode if Battery Voltage Falls Below 13.2V and Trickle Charges at 0.15A if
Battery Voltage is Below 10V; 0°C to 45°C Battery Temperature Charging Range
MBRS140
SOLAR PANEL INPUT
<40V OC VOLTAGE
16V PEAK POWER VOLTAGE
10μF
499k
SW
V
V
IN
LT3652HV
BZX84C6V2L
1μF
1N4148
WURTH
7447779122
MBRS340
22μH
0.1
IN_REG
BOOST
SENSE
BAT
SYSTEM
LOAD
SHDN
CHRG
100k
+
910
10μF
100μF
309k
100k
NTC
FAULT
174k
V
+
FB
TIMER
4.7μF
12V LEAD
ACID BATTERY
10k
B = 3380
muRata
1M
1N4148
NCP18XH103
3652 TA04
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT3650-4.1/LT3650-4.2 Monolithic 2A Switch Mode 1-Cell Li-Ion
Battery Charger
Standalone, 4.75V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A
IN
Programmable Charge Current, Timer or C/10 Termination, Small and Few
External Components, 3mm × 3mm DFN12 Package, –4.1 for 4.1V Float Voltage
Batteries, –4.2 for 4.2V Float Voltage Batteries
LT3650-8.2/LT3650-8.4 Monolithic 2A Switch Mode 2-Cell Li-Ion
Battery Charger
Standalone, 9V ≤ V ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable
IN
Charge Current, Timer or C/10 Termination, Small and Few External
Components, 3mm × 3mm DFN12 Package, –8.2 for 2 × 4.1V Float Voltage
Batteries, –8.4 for 2 × 4.2V Float Voltage Batteries
LTC4001/LTC4001-1
Monolithic 2A Switch Mode Synchronous Standalone, 4V ≤ V ≤ 5.5V (6V Absolute Maximum, 7V Transient), 1.5MHz,
IN
Li-Ion Battery Charger
Synchronous Rectification Efficiency >90%, Adjustable Timer Termination, Small
and Few External Components, 4mm × 4mm QFN-16 Package, –1 for 4.1V Float
Voltage Batteries
LTC4002
LTC4006
Switch Mode Lithium-Ion Battery Charger Standalone, 4.7V ≤ V ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination
IN
Small, High Efficiency, Fixed Voltage,
Lithium-Ion Battery Charger with
Termination and Thermistor Sensor
Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit,
16-Pin Narrow SSOP Package
LTC4007
LTC4008
High Efficiency, Programmable Voltage
Battery Charger with Termination
4A, High Efficiency, Multi-Chemistry
Battery Charger
Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit,
Thermistor Sensor and Indicator Outputs
Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor
Voltage/Current Programming, AC Adapter Current Limit and Thermistor Sensor
and Indicator Outputs
LTC4009/LTC4009-1/
LTC4009-2
4A, High Efficiency, Multi-Chemistry
Battery Charger
Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor
Voltage/Current Programming, AC Adapter Current Limit and Thermistor
Sensor and Indicator Outputs 1 to 4 Cell Li, Up to 18 Cell Ni, SLA and Supercap
Compatible; 4mm × 4mm QFN-20 Package, –1 Version for 4.1V Li Cells, –2 Version
for 4.2V Li Cells
LTC4012/LTC4012-1/
4A, High Efficiency, Multi-Chemistry
PowerPath Control, Constant-Current/Constant-Voltage Switching Regulator
LTC4012-2/ LTC4012-3 Battery Charger with PowerPath™ Control Charger, Resistor Voltage/Current Programming, AC Adapter Current Limit and
Thermistor Sensor and Indicator Outputs 1 to 4 Cell Li, Up to 18 Cell Ni, SLA
and Supercap Compatible; 4mm × 4mm QFN-20 Package, –1 Version for 4.1V Li
Cells, –2 Version for 4.2V Li Cells, –3 Version has Extra GND Pin
3652hvf
LT 0510 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2010
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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