LTC4020
55V Buck-Boost
Multi-Chemistry
Battery Charger
Features
Description
Wide Voltage Range: 4.5V to 55V Input, Up to 55V
Output (60V Absolute Maximums)
nn Synchronous Buck-Boost DC/DC Controller
nn Li-Ion and Lead-Acid Charge Algorithms
nn ±0.5% Float Voltage Accuracy
nn ±5% Charge Current Accuracy
nn Instant-On for Heavily Discharged Batteries
nn Ideal Diode Controller Provides Low Loss
PowerPath When Input Power is Limited
nn Input Voltage Regulation for High Impedance Input
Supplies and Solar Panel Peak Power Operation
nn Onboard Timer for Protection and Termination
nn Bad Battery Detection with Auto-Reset
nn NTC Input for Temperature Qualified Charging
nn Binary Coded Open-Collector Status Pins
nn Low Profile (0.75mm) 38-Pin 5mm × 7mm QFN
Package
The LTC®4020 is a high voltage power manager providing PowerPath™ instant-on operation and high efficiency
battery charging over a wide voltage range. An onboard
buck-boost DC/DC controller operates with battery and/or
system voltages above, below, or equal to the input voltage.
nn
Applications
Portable Industrial and Medical Equipment
Solar-Powered Systems
nn Military Communications Equipment
nn 12V to 24V Embedded Automotive Systems
nn
nn
The LTC4020 seamlessly manages power distribution
between battery and converter outputs in response to load
variations, battery charge requirements and input power
supply limitations.
The LTC4020 battery charger can provide a constant-current/
constant-voltage charge algorithm (CC/CV), constantcurrent charging (CC), or charging with an optimized 4-step,
3-stage lead-acid battery charge profile. Maximum converter
and battery charge currents are resistor programmable.
The IC's instant-on operation ensures system load power
even with a fully discharged battery. Additional safety
features include preconditioning for heavily discharged
batteries and an integrated timer for termination and
protection.
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. Protected by U.S. Patents, including 7583113 and 8405362.
Typical Application
Buck-Boost DC/DC Converter Controller with PowerPath Battery Charger Accepts
Inputs from 4.5V to 55V and Produces Output Voltages Up to 55V
RSENSEA
BUCK-BOOST
DC/DC CONVERTER
PowerPath BATTERY CHARGER
100
VOUT
CSP
TG2
BGATE
SENSGND
SENSBOT
BG1
70
90
60
INPUT POWER
50
85
40
30
80
20
10
P(LOSS)
NTC
75
RNTC
TG1
SENSTOP
SENSVIN
80
POWER (W)
CSN
VFB
RSENSEB
90
RCS
LTC4020
BG2
100
VOUT = 14V
EFFICIENCY
95
EFFICIENCY (%)
VIN
5V to 30V 6-Cell Lead-Acid Supply/Charger
Maximum Power Efficiency vs VIN
(Application Circuit on Page 37)
5
10
15
20
VIN (V)
25
0
30
4020 TA01b
VFBMAX
4020 TA01a
4020fd
For more information www.linear.com/LTC4020
1
LTC4020
Absolute Maximum Ratings
Pin Configuration
(Note 1)
SW2
BG2
INTVCC
PGND
PVIN
SW1
BG1
TOP VIEW
PVIN, SENSVIN.............................................. –0.3 to 60V
BST1, BST2................................................... –0.3 to 66V
SW1, SW2.........................................................–2 to 60V
SENSVIN – PVIN............................................ –0.3 to 60V
BST1 – SW1, BST2 – SW2.............................. –0.3 to 6V
SENSVIN – SENSTOP, SENSBOT –
SENSGND.....................................................–0.3 to 0.3V
CSP, CSN...................................................... –0.3 to 60V
CSP – CSN....................................................–0.3 to 0.3V
STAT1, STAT2, SHDN.................................... –0.3 to 60V
VFBMAX, VINREG, VFB, VFBMIN, BAT, FBG........ –0.3 to 60V
MODE.............................................................. –0.3 to 6V
Status Pin Currents:
STAT1, STAT2.......................................................5mA
Operating Junction Temperature
Range (Note 2)........................................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
38 37 36 35 34 33 32
TG1 1
31 TG2
BST1 2
30 BST2
SGND 3
29 SGND
SENSGND 4
28 VC
SENSBOT 5
27 ITH
39
SGND
SENSTOP 6
SENSVIN 7
26 VFBMAX
25 ILIMIT
24 CSOUT
RT 8
SHDN 9
23 CSP
VIN_REG 10
22 CSN
21 BGATE
MODE 11
20 BAT
STAT1 12
VFBMIN
FBG
VFB
NTC
RNG/SS
STAT2
TIMER
13 14 15 16 17 18 19
UHF PACKAGE
38-LEAD PLASTIC QFN (5mm × 7mm)
TJMAX = 125°C, θJA = 34°C/W, θJC = 2°C/W
EXPOSED PAD (PIN 39) IS SGND, MUST BE SOLDERED TO PCB
Order Information
(http://www.linear.com/product/LTC4020#orderinfo)
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4020EUHF#PBF
LTC4020EUHF#TRPBF
4020
38-Lead (5mm × 7mm) Plastic QFN
–40°C to 125°C
LTC4020IUHF#PBF
LTC4020IUHF#TRPBF
4020
38-Lead (5mm × 7mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
Electrical Characteristics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). PVIN = SENSVIN = CSP = CSN = BAT = 20V, SHDN = 2V,
C(TG1, BG1, TG2, BG2) = 1000pF, VRNG/SS = 2V.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Buck-Boost Switching Converter
VIN
Operating Voltage Range
PVIN; SENSVIN
l
4.5
UVLO
VIN Supply UVLO (Rising)
VIN Supply UVLO Hysteresis
DC/DC Functions Enabled
VIN Falling
l
3.6
SENSVIN Supply UVLO (Rising)
SENSVIN UVLO Hysteresis
INTVCC Enabled
SENSVIN Falling
BST Supplies UVLO (Rising)
BST Supplies UVLO Hysteresis
BST1 – SW1; BST2 – SW2;
SW1, SW2 = 0V
4.0
0.4
55
V
4.4
V
V
3.4
0.3
l
3.0
3.3
0.4
V
V
3.8
V
V
4020fd
2
For more information www.linear.com/LTC4020
LTC4020
Electrical Characteristics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). PVIN = SENSVIN = CSP = CSN = BAT = 20V, SHDN = 2V,
C(TG1, BG1, TG2, BG2) = 1000pF, VRNG/SS = 2V.
SYMBOL
INTVCC
IPVIN
ISENSVIN
PARAMETER
CONDITIONS
5.15
V
Boost Refresh Supply Short-Circuit Current
Limit
VINTVCC = 0V
l
PVIN Operating Current
Note 3; ITH = 0V
l
Shutdown Current
VSHDN = 0
l
3
6
µA
l
0.25
0.5
mA
25
60
SENSEVIN Operating Current
VSHDN = 0
85
4.46
V
150
mA
1.6
l
SENSETOP Operating Current
3
32.5
VSHDN = 0
DC/DC Converter Reference
Charging Terminated
SHDN
IC Enable Threshold (Rising)
Threshold Hysteresis
µA
µA
0.1
µA
2.7
2.75
2.8
l
1.175
1.225
100
1.275
V
mV
60
mV
10
DC/DC Converter Inductor Current Limit
(Average Value)
VSENSVIN – VSENSTOP;
VSENSGND – VSENSBOT
l
45
50
Reverse Current Inhibit
(Average Value)
VITH Falling (TG2 Disabled)
VITH Rising (TG2 Enabled)
l
0
2
6
Inductor Current Limit Programming
VILIMIT = 0.5V; VILIMIT/VSENS(MAX)
l
47.5
ILIMIT Pin Bias Current
mA
l
SHDN Pin Bias Current
ITH
5.0
ILOAD = 5mA
Shutdown Current
ILIMIT
UNITS
PVIN = 4.5V; IINTVCC = 5mA
VFBMAX
VSENS
MAX
Boost Refresh Supply Voltage
l
4.85
TYP
Boost Refresh Supply Dropout
Shutdown Current
ISENSTOP
MIN
nA
mV
mV
20
50
V
V/V
52.5
µA
Error Amp Current Limit
VFBMAX = 0, VITH = 1.3V
8
µA
Error Amp Transconductance
VFBMAX = 2.75V; VITH = 1.3V
95
umho
High Side Current Sense Transconductance
(VSENSVIN – VSENSETOP) to IVC
VC = 1.8V
200
umho
Low Side Current Sense Transconductance
(VSENSGND – VSENSEBOT) to IVC
VC = 1.8V
200
umho
DCMAX
Maximum Duty Cycle
BG2: tON • fO
l
70
80
fO
Switching Frequency
RRT = 100k
RRT = 50k
RRT = 250k
l
235
250
500
100
265
kHz
kHz
kHz
VC
%
tON
Minimum On Time
BG2
l
150
250
ns
tOFF
Minimum Off Time
TG1
l
300
500
ns
tTR
Gate Drive Transition Time
TG1, BG1, TG2, BG2
5
ns
tNOL
Gate Drive Non-Overlap time
(TG1 – SW1) to BG1,
(TG2 – SW2) to BG2
75
ns
4020fd
For more information www.linear.com/LTC4020
3
LTC4020
Electrical Characteristics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). PVIN = SENSVIN = CSP = CSN = BAT = 20V, SHDN = 2V,
C(TG1, BG1, TG2, BG2) = 1000pF, VRNG/SS = 2V.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Charger
VBAT
Charger Output Voltage Range
VFB
Float Reference
55
l
CC/CV Charging (MODE = 0V)
Auto Recharge Voltage
Precondition Threshold (Rising)
Precondition Hysteresis
% of Float Reference
% of Float Reference
Absorption Reference
Lead-Acid Charging (MODE = INTVCC)
% of Absorption Reference
% of Absorption Reference
% of Absorption Reference
Float Reference
Bulk Charge Threshold (Falling)
Precondition Threshold (Rising)
Precondition Hysteresis
Voltage Reference
l
l
l
2.4875
2.475
96.5
68
l
l
l
l
2.4875
2.475
91.5
86
68
l
2.4875
2.475
CC Charging (MODE = - NC -)
2.5
V
2.5125
2.525
98.5
72
V
V
%
%
mV
2.5125
2.525
93.5
89
72
V
V
%
%
%
mV
2.5
2.5125
2.525
V
V
97.5
70
85
2.5
92.5
87.5
70
85
VIN_REG
Input Regulation Reference
% of Float (CC/CV), Safety (CC), or
Absorption (LA) Reference
l
98
100
102
%
VFBMIN
Instant-On Reference
% of Float (CC/CV) or Absorption (LA)
Reference
l
84
85
86
%
C/10 Detection Enable (Rising)
Hysteresis (Falling)
2.175
20
V
mV
Instant-On Charge Current Reduction
Threshold
VCSN – VBAT; Note 4
0.45
V
C/10 Detection Enable
C/10 Detection Hysteresis
VCSN – VBAT Falling
VCSN – VBAT Rising
1.05
150
V
mV
Charge Current Reduction Gain
ΔVCS(MAX)/Δ(VCSN – VBAT);Note 4
–33
mV/V
IBATQ
Battery Bias Currents with PowerPath
Switcher Disabled
ICSP + ICSN + IBAT
CSN, CSP
Charger Current Sense Pin Operating Bias
Currents
ICSP = ICSN; Charging Enabled
Charger Current Sense Limit Voltage
VCSP – VCSN
l
47.5
50
52.5
mV
Charger Current Sense Termination Voltage
(C/10)
VCSP – VCSN; MODE = 0V
l
3
5
7
mV
Charger Current Sense Precondition Voltage
VCSP – VCSN; VFB = 1.5
l
1.5
3
4.5
mV
Sense Input UVLO
UVLO Hysteresis
VCSP Rising (Charging Enabled)
VCSP Falling (Charging Disabled)
l
1.6
1.75
100
1.9
V
mV
9
l
18
40
µA
µA
Offset
VCSP = VCSN
l
0.225
0.25
0.290
Gain
ΔVCSOUT / Δ(VCSP – VCSN)
l
19
20
21
V/V
RNG/SS
Current Limit Programming
VRNG/SS = 0.5V; VRNG/SS/VCS(MAX)
l
18
20
22
V/V
NTC
NTC Range Limit (High)
NTC Range Limit (Low)
NTC Range Hysteresis
VNTC Rising
VNTC Falling
% of VNTC(H,L)
l
l
1.30
0.27
1.35
0.3
20
1.40
0.33
V
V
%
INTC
NTC Pin Bias Current
VNTC = 0.8V
l
47.5
50
52.5
µA
NTC Disable Current
INTC Pin Current (Falling)
CSOUT
NTC Disable Current Hysteresis
VBGATE
Gate Clamp Voltage
VCSN – VBGATE
C/10 Detection Enable (Falling)
C/10 Detection Enable Hysteresis
VCSN < 7V
l
7
V
3.5
µA
2
µA
9.5
0.425
0.125
12
V
V
V
4020fd
4
For more information www.linear.com/LTC4020
LTC4020
Electrical Characteristics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). PVIN = SENSVIN = CSP = CSN = BAT = 20V, SHDN = 2V,
C(TG1, BG1, TG2, BG2) = 1000pF, VRNG/SS = 2V.
SYMBOL
BGATE
TIMER
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BGATE Pull-Down Current
Charging Enabled
15
µA
BGATE Pull-Up Current
Charging Disabled; VCSN – VBGATE = 2V
15
µA
BGATE Standby Pull-Down Current
VSHDN = 0V
120
µA
Ideal Diode Pull-Down Current
Charging Disabled; VBAT – VCSN = 0.5V
Ideal Diode Forward Voltage
VBAT – VCSN; VCSN Measured Through
100Ω Series Resistor
500
l
5
Timer High Threshold
Timer Low Threshold
C/10 Mode Threshold (Rising)
l
0.4
C/10 Mode Hysteresis
14
µA
20
1.5
V
1.0
V
0.5
0.6
225
Timer Source/Sink Current
VTIMER = 1.25V
l
VSTAT(L)
Status Pins Enabled Voltage
ISTAT1 = 1mA; ISTAT2 = 1mA
ISTAT1 = 5mA; ISTAT2 = 5mA
l
l
8.5
mV
V
mV
10
11.5
µA
0.15
0.75
0.4
2.5
V
V
IVFBMIN
Instant-On Feedback Bias Current
10
nA
IVFB
Feedback Pin Bias Current
10
nA
IVIN_REG
Input Regulation Bias Current
10
nA
IFBG
Pin Current (Disabled)
10
nA
RNTC
NTC Minimum Disable Resistance
400
kΩ
RFBG
FBG Resistance to SGND
VSHDN = 0V; VFBG = 55V
l
IFBG = 1mA
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 LTC4020 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC4020E is guaranteed to meet specifications 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
LTC4020I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The junction temperature (TJ) is calculated from
the ambient temperature (TA) and power dissipation (PD) according
l
250
20
50
Ω
to the formula TJ = TA + (PD • θJA). Note that the maximum ambient
temperature consistent with these specifications is determined by specific
operating conditions in conjunction with board layout, the rated package
thermal resistance and other environmental factors. This IC includes
overtemperature protection that is intended to protect the device during
momentary overload. Junction temperature will exceed 125°C when
overtemperature protection is active. Continuous operation above the
specified maximum operating junction temperature may impair device
reliability.
Note 3: ICC does not include switching currents. VBST1 = VBST2 = VINTVCC
and VSW1 = VSW2 = 0V for testing.
Note 4: See Typical Performance Characteristics
4020fd
For more information www.linear.com/LTC4020
5
LTC4020
Typical Performance Characteristics
VFLOAT(CC/CV) or, VABSORB(Lead-Acid)
Reference vs Temperature
VFLOAT(Lead-Acid) Reference vs
Temperature
VFBMAX Reference vs Temperature
2.525
2.36
2.80
2.520
2.35
2.79
2.515
2.34
2.78
2.33
2.505
2.500
2.495
2.77
2.32
VOLTAGE (V)
VOLTAGE (V)
2.510
VOLTAGE (V)
TA = 25°C, unless otherwise noted.
2.31
2.30
2.29
2.76
2.75
2.74
2.490
2.28
2.73
2.485
2.27
2.72
2.480
2.26
2.71
2.475
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
2.25
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
2.70
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4020 G02
4020 G01
Shutdown Current vs Temperature
(IPVIN + ISENSVIN + ISENSTOP)
INTVCC Short-Circuit Current
Limit vs Temperature
35
30
25
20
155
100
154
90
MAXIMUM CHARGE CURRENT (%)
45
INTVCC CURRENT LIMIT (mA)
STANDBY MODE CURRENT (µA)
50
40
153
152
151
150
149
148
147
146
15
–40–30–20–10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
10.0
70
9.5
60
9.0
30
20
10
0
0.2
20
7.0
10
6.5
6.0
0.6
0.4
0.8
RNG/SS VOLTAGE (V)
1.2
1.0
IBATQ (IBAT + ICSN + ICSP) vs
Temperature PowerPath Switcher
Disabled
VBAT = 20V
10.5
10.0
8.0
7.5
4020 G07
40
11.0
8.5
30
0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
VCSN–BAT (V)
50
4020 G06
IBATQ (µA)
80
IBATQ (µA)
10.5
MAXIMUM CHARGE CURRENT (%)
11.0
90
0
60
IBATQ (IBAT + ICSN + ICSP) vs VBAT
PowerPath Switcher Disabled
100
40
70
4020 G05
Instant-On: Maximum Charge
Current (Percent of ICSMAX) vs
VCSN–BAT
50
80
0
145
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4020 G04
0
4020 G03
Maximum Charge Current
(Percent of Programmed ICSMAX)
vs RNG/SS Voltage
9.5
9.0
8.5
0
5 10 15 20 25 30 35 40 45 50 55
VBAT (V)
4020 G08
8.0
–40–30–20–10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
4020 G09
4020fd
6
For more information www.linear.com/LTC4020
LTC4020
Typical Performance Characteristics
Ideal Diode VF vs Temperature
Ideal Diode VF vs Battery Voltage
16.0
24
15.5
14.5
14.0
13.5
13.0
4.4
25°C
18
16
0
125°C
Feedback References vs Input
Voltage
CSOUT vs CSP-CSN
2.80
1.2
2.75
1.1
2.70
FEEDBACK REFERENCES (V)
1.3
0.9
0.8
0.7
0.6
0.5
0.4
0.3
20
30
V(CSP-CSN) (mV)
40
2.55
255
2.45
5.02
5.00
4.98
4.96
2.40
2.35
4.94
VFLOAT(LEAD-ACID)
4.92
5
4.90
10 15 20 25 30 35 40 45 50 55
VIN (V)
4020 G14
255
254
SWITCHING FREQUENCY (kHz)
253
252
251
250
249
248
247
5
10 15 20 25 30 35 40 45 50 55
VIN (V)
4020 G15
Switching Frequency vs
Temperature
RRT = 100kΩ
254
SWITCHING FREQUENCY (kHz)
VFLOAT(CC/CV;ABSORB)
2.50
Switching Frequency vs Input
Voltage
4020 G12
5.04
2.60
4020 G13
50
40
5.06
2.65
2.25
50
20
30
IINTVCC (mA)
IINTVCC = 5mA
5.08
VFBMAX
2.30
10
10
INTVCC vs VIN
5.10
IRNG/SS, ILIMIT, INTC, vs
Temperature
52.5
VIN = 20V
RRT = 100kΩ
52.0
51.5
253
IRNG/SS, ILIMIT, INTC (µA)
VCSOUT (V)
1.0
0
0
4020 G11
4020 G10
0.2
4.0
10
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
5 10 15 20 25 30 35 40 45 50 55
VBAT (V)
4.2
4.1
VINTVCC (V)
12.0
4.3
14
12
12.5
PVIN = 4.5V
20
VINTVCC (V)
15.0
BST Refresh Regulator Dropout
INTVCC vs IINTVCC
4.5
VBAT = 20V
22
IDEAL DIODE VF (mV)
IDEAL DIODE VF (mV)
TA = 25°C, unless otherwise noted.
252
251
250
249
248
51.0
50.5
50.0
49.5
49.0
247
48.5
246
246
48.0
245
245
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
47.5
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
0
10
20
30
VIN (V)
40
50
60
4020 G16
4020 G17
4020 G18
4020fd
For more information www.linear.com/LTC4020
7
LTC4020
Pin Functions
TG1 (Pin 1): VIN side (step-down) primary switch FET
gate driver output.
BST1 (Pin 2): Boosted supply rail for VIN side (step-down)
switch FETs. Connect 1µF capacitor from this pin to SW1.
Connect 1A Schottky diode cathode to this pin, anode to
INTVCC pin.
SENSGND (Pin 4): Kelvin connection for PGND used for
SENSBOT current sense reference.
SENSBOT (Pin 5): Ground Referred Current Sense Amplifier
Input. Inductor current is monitored via a PGND referenced
current sense resistor (RSENSEB), typically in series with
the source of the VIN side synchronous switch FET. Kelvin
connect this pin to the associated sense resistor. Inductor
current is limited to a maximum average value (ILMAX), and
corresponds to 50mV across this sense resistor during
normal operation.
RSENSEB = 0.05/ILMAX
Set RSENSEB = RSENSEA, as described in SENSTOP pin
description. A filter capacitor (CSENSB) is typically connected from SENSBOT to SENSGND for noise reduction.
CSENSB ~ 1nS/RSENSEB
See Applications Information section.
SENSTOP (Pin 6): VIN Referred Current Sense Amplifier
Input. Inductor current is monitored via a VIN referenced
current sense resistor (RSENSEA), typically in series with
the drain of the VIN side primary switch FET. Kelvin connect this pin to the associated sense resistor. Inductor
current is limited to a maximum average value (ILMAX),
and corresponds to 50mV across this sense resistor during normal operation.
RSENSEA = 0.05/ILMAX
Set RSENSEA = RSENSEB, as described in SENSBOT pin
description.
SENSVIN (Pin 7): Kelvin connection for input supply (VIN)
used for SENSTOP current sense reference. Input power
supply pin for most internal low current functions. Typical
pin bias current is 0.25mA.
RT (Pin 8): System Oscillator Frequency Control Pin.
Connect resistor (RRT) from this pin to ground. Resistor
value can range from 50kΩ (500khz) to 500kΩ (50khz).
RRT = 100kΩ yields 250kHz operating frequency. See
Applications Information.
SHDN (Pin 9): Precision Threshold Shutdown Pin. Enable threshold is 1.225V (rising), with 100mV of input
hysteresis. When in shutdown, all charging functions are
disabled and input supply current is reduced to 27.5µA.
Typical SHDN pin input bias current is 10nA.
VIN_REG (Pin 10): Input Voltage Regulation Reference.
Battery charge current is reduced when the voltage on
this pin falls below 2.5V. Connecting a resistor divider
from VIN to this pin enables programming of minimum
operational VIN voltage for the battery charging function.
This is used to program the peak power voltage for a
solar panel, or to help maintain a minimum voltage on
a poorly regulated input supply. This pin should not be
used to program minimum operational VIN voltage with
low impedance supplies. Should the input supply begin to
collapse, the LTC4020 reduces the DC/DC converter input
power such that programmed minimum VIN operational
voltage is maintained. If the voltage regulation feature is
not used, connect the VIN_REG pin to VIN or INTVCC. Typical
VIN_REG pin input bias current is 10nA. See Applications
Information.
MODE (Pin 11): Charger Mode Control Pin. Short this pin
to ground to enable a constant-current/constant-voltage
(CC/CV) charging algorithm. Connect this pin to pin INTVCC
to enable a 4-step, 3-stage lead-acid charging algorithm.
Float this pin to force a constant-current (CC) charging
function. See Applications Information section.
STAT1 (Pin 12): Open-collector status output, typically
pulled up through a resistor to a supply voltage. This status
pin can be pulled up to voltages as high as 55V when the
pin is disabled, and can sink currents up to 1mA when logic
low ( 2.5 – ε?
YES
YES
CHARGE TO FIXED
VOLTAGE
NO
RUN LOW BATTERY
TIMER
NO
CHARGE AT
CONSTANT-CURRENT
IBAT < C/10?
NO
TIMER ACTIVE?
YES
NO
TIMER AT 1/8
EOC?
VFB = 2.4375V
YES
YES
YES
INDICATE NOT
CHARGING
RUN SAFETY TIMER
NO
NO
STOP CHARGING
IBAT < C/10?
YES
BGATE PULLED HIGH
INDICATE NOT
CHARGING
INDICATE BAD
BATTERY FAULT
SAFETY TIMER
AT EOC?
NO
YES
VFB > 1.75?
NO
STOP CHARGING
INDICATE NOT
CHARGING
ENABLE IDEAL DIODE
FUNCTION
YES
VFB = 2.4375?
NO
YES
4020 CD01
4020fd
34
For more information www.linear.com/LTC4020
LTC4020
Applications Information
LTC4020 Lead-Acid Charging Diagram
START
INDICATE NOT
CHARGING
NO
POWER
AVAILABLE?
YES
BGATE PULLED
LOW
SET ABSORPTION
REFERENCE (2.5V)
CLEAR LOW BATTERY
AND SAFETY TIMERS
NTC
OUT-OF-RANGE?
YES
INDICATE NOT
CHARGING
STOP CHARGING
NO
SET ABSORPTION
REFERENCE (2.5V)
INDICATE BULK
CHARGING
YES
BGATE PULLED LOW
ENABLE IDEAL
DIODE FUNCTION
VFB < 2.125?
TIMERS ACTIVE?
YES
NO
NO
FLOAT
REFERENCE SET
(2.3125)?
VFB < 1.75?
YES
NO
YES
PAUSE TIMERS
NO
TRICKLE
CHARGE (7%)
VFB < 2.5 – ε?
INDICATE
ABSORPTION
CHARGING
YES
CHARGE TO FIXED
VOLTAGE
NO
NO
INDICATE BULK
CHARGING
TIMER ACTIVE?
NO
NO
TIMER AT 1/8
EOC?
RUN SAFETY TIMER
YES
VFB = 2.4375V
YES
STOP CHARGING
BGATE PULLED HIGH
IBAT < C/10?
NO
YES
YES
TIMER ACTIVE?
YES
CHARGE AT
CONSTANT-CURRENT
RUN LOW
BATTERY TIMER
SAFETY TIMER
AT EOC?
NO
SET FLOAT
REFERENCE
(2.3125V)
INDICATE NOT
CHARGING
VFB > 1.75?
NO
YES
YES
NO
IBAT < C/10?
INDICATE FLOAT
CHARGING
NO
YES
4020 CD02
4020fd
For more information www.linear.com/LTC4020
35
LTC4020
Applications Information
LTC4020 Constant-Current Charging Diagram
START
INDICATE NOT
CHARGING
NO
POWER
AVAILABLE?
YES
BGATE PULLED
LOW
CLEAR TIMER
NTC
OUT-OF-RANGE?
YES
STOP CHARGING
NO
BGATE PULLED LOW
INDICATE NTC
FAULT
CHARGE AT
CONSTANT-CURRENT
ENABLE IDEAL
DIODE FUNCTION
INDICATE CHARGING
TIMERS ACTIVE?
NO
YES
NO
TIMER ACTIVE?
PAUSE TIMER
YES
RUN TIMER
NO
SAFETY TIMER
AT EOC?
YES
STOP CHARGING
INDICATE NOT
CHARGING
ENABLE IDEAL
DIODE FUNCTION
4020 CD02
4020fd
36
For more information www.linear.com/LTC4020
LTC4020
Typical Applications
5V to 30V to 6-cell lead-acid PowerPath charger/system supply. 6A inductor current limit with
2.5A battery charge current limit. Instant-on functionality incorporated for battery voltages below 12.25V,
14.4V absorption voltage, 13.3V float voltage,and 15.6V maximum output voltage (Instant-On and NTC fault only).
Status pins light LEDs for visible charge-state monitoring.
VIN
5V TO 30V
RSENSEA
0.008
1µF
+
56µF
×2
CMSH3-40MA
VOUT
Si7272DP
15µH
XAL1010-153MEB
Si7272DP
Si7272DP
Si7272DP
0.1µF
4.7µF
+
56µF
×3
RSENSEB
0.008
4.7µF
SBR0560S1
PGND
INTVCC
SBR0560S1
PVIN
BG2
BG1
SW2
SW1
TG2
TG1
1µF
LTC4020
BST1
0.033µF
ITH
SENSTOP
VFBMAX
680pF
95.3k
2nF
2nF
20k
100Ω
CSP
0.33µF
VIN_REG
2.7k
ILIMIT
33k
CSOUT
RT
SHDN
100k
VC
SENSBOT
SENSVIN
RT, 130k
284k
1µF
SGND
SGND
SENSGND
BZX84C6V2L
BST2
MODE
CSN
100Ω
BGATE
STAT1
RCS
0.02Ω
Si7135DP
BAT
2.7k
VFBMIN
STAT2
FBG
20k
95.3k
TIMER
RNG_SS
SGNDBACK
VFB
NTC
RNTC
10k
6-CELL LEAD-ACID (12V)
4020 TA02
4020fd
For more information www.linear.com/LTC4020
37
LTC4020
Typical Applications
15V to 55V to 6-cell Li-Ion PowerPath charger/system supply. 6A inductor current limit with 2.5A battery charge current limit.
Instant-on functionality for battery voltages below 20.4V, 24V charge termination voltage, and 26.4V maximum output voltage.
Status pins light LEDs for visible charge-state monitoring.
V IN
15V TO 55V
RSENSEA
0.008
0.1µF
VOUT
24V AT
3.5A MAX
MBRS360
+
Si7960DP
Si7960DP
4.7µF
×2
XAL1010-153MEB
15µH
56µF
×2
4.7µF
×4
Si7960DP
Si7960DP
+
RSENSEB
0.008
56µF
×2
10µF
SBR0560S1
PGND
SBR0560S1
INTVCC
BG2
SW2
PVIN
1µF
BG1
TG2
SW1
1µF
BST2
TG1
LTC4020
BST1
SENSGND
SENSBOT
RT, 100k
105k
SHDN
47k
ITH
56k
680pF
10nF
215k
VFBMAX
SENSTOP
ILIMIT
SENSVIN
CSOUT
100Ω
100pF
24.9k
CSP
RT
4.7Ω
2.2µF
CSN
SHDN
RCS
0.02Ω
100Ω
1nF
VIN_REG
10k
68pF
SGND
VC
SGND
0.033µF
BZX84C6V2L
Si7461DP
BGATE
MODE
BAT
2.7k
STAT1
VFBMIN
FBG
2.7k
STAT2
0.2µF
215k
VFB
NTC
TIMER
RNG_SS
24.9k
RNTC
10k
SGNDBACK
6-CELL Li-ION (24V)
4020 TA03
4020fd
38
For more information www.linear.com/LTC4020
LTC4020
Typical Applications
9V to 55V to 9-cell lead-acid (18V) charger/system supply with no PowerPath.
External 5V regulator for boosted supplies. 5A inductor current limit with 1.67A battery charge current limit.
21.5V absorption voltage output, 19.9V float voltage output.
VIN
9V TO 55V
RSENSEA
0.01
1µF
VOUT
+
56µF
×2
CMSH3-40MA
Si7960DP
XAL1010-153MEB
Si7272DP
15µH
Si7272DP
0.1µF
4.7µF
Si7850DP
+
RSENSEB
0.01
OUT
VIN
4.7µF
LT3010-5
SHDN
SBR0560S1
SENSE
PGND
GND
INTVCC
PVIN
BG2
BG1
SW2
SW1
TG2
TG1
1µF
BST1
LTC4020
SBR0560S1
BZX84C6V2L
0.033µF
SENSGND
SENSBOT
SENSTOP
SENSVIN
RT, 100k
RT
SGND
43k
VC
ITH
680pF
43k
VFBMAX
1.5nF
ILIMIT
CSOUT
100Ω
CSP
0.33µF
SHDN
VIN_REG
100k
MODE
STAT1
1µF
BST2
SGND
249k
56µF
×3
CSN
100Ω
RCS
0.03Ω
100pF
BGATE
BAT
VFBMIN
STAT2
FBG
TIMER
VFB
RNG_SS
SGNDBACK
NTC
75.9k
10k
9-CELL LEAD-ACID (18V)
4020 TA04
4020fd
For more information www.linear.com/LTC4020
39
LTC4020
Package Description
Please refer to http://www.linear.com/product/LTC4020#packaging for the most recent package drawings.
UHF Package
38-Lead Plastic QFN (5mm × 7mm)
(Reference LTC DWG # 05-08-1701 Rev C)
0.70 ±0.05
5.50 ±0.05
5.15 ±0.05
4.10 ±0.05
3.00 REF
3.15 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
5.5 REF
6.10 ±0.05
7.50 ±0.05
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.75 ±0.05
5.00 ±0.10
PIN 1 NOTCH
R = 0.30 TYP OR
0.35 × 45° CHAMFER
3.00 REF
37
0.00 – 0.05
38
0.40 ±0.10
PIN 1
TOP MARK
(SEE NOTE 6)
1
2
5.15 ±0.10
5.50 REF
7.00 ±0.10
3.15 ±0.10
(UH) QFN REF C 1107
0.200 REF 0.25 ±0.05
0.50 BSC
R = 0.125
TYP
R = 0.10
TYP
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE
OUTLINE M0-220 VARIATION WHKD
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
40
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm 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
For more information www.linear.com/LTC4020
4020fd
LTC4020
Revision History
REV
DATE
DESCRIPTION
PAGE NUMBER
A
01/14
Changed VIN to PVIN
Modified ISENSTOP Operating Current spec
Modified Error Amp Transconductance spec
Changed C/10 Detection Enable Units
Modified C/10 Detection Hysteresis spec
Changed Conditions for Gate Clamp Voltage
Changed Conditions for BGATE tests
Changed Conditions for Pin Current (Disabled) spec
Changed cathode to anode for BST1
Changed anode to cathode for BST1
Modified equations for TEOC and TPRE and associated TIMER text
Modified equations for RFB1/RFB2 and RMIN1/RMIN2
Changed cathode to anode for BST2
Changed anode to cathode for BST2
Modified Error Amplified Transconductance
Modified step-up and step-down equations in Switch FET section
Modified CTIMER equation and associated text
Modified Typical Applications circuit
Modified Typical Application circuit to 12-cell
2 to 5
3
3
4
4
4
5
5
8
8
9
10
12
12
14
24
30
38
42
B
09/14
Added “(Application Circuit on Page 37)” to efficiency curve title
Added Ω unit to RFBG specification
1
5
6
10
12
14
15
23
28
37
38
39
Changed “INTVCC Short Circuit Current Limit vs Temperature” curve y-axis units to ‘mA’
Added text to the end of the NTC (Pin 16) section
Corrected formula: (VOUTMAX/2.75) - 1
Changed BST1 on lower-right of block diagram to BST2; Insert “(VSENS)” below ‘2mV’ near VC pin
Added 2V Zener diode symbol from NTC pin (cathode) to ground (anode)
Added “average” to first line; change “Charge” to “Average Inductor” in Figure 6 title
Changed “inductor” to “charge”
Added ground symbol to bottom of IC symbol (backside connection)
Flipped PMOS symbol vertically (Si7461DP); add ground symbol to bottom of IC symbol (backside connection)
Added ground symbol to bottom of IC symbol (backside connection)
Moved connection of BZX84C6V2L anode from BG2 to SW2 (diode between BST2 and SW2); add ground symbol to
bottom of IC symbol (backside connection)
C
D
09/15
04/16
Added pin names to Typical Application IC drawing
Added text to end of SENSBOT (5) pin description section
Changed text in RNG/SS section: “Inductor” to “Charge”
Changed ILIMIT text, “...pin, so maximum charge current..." to “...pin, so maximum inductor current..."
Changed Operation section to “a 0.47µF capacitor on the TIMER pin is typically used, which generates a 6.8 hour
absorption stage safety timeout”
Changed “CSENSBOT,SENSGND” to “CSENSB”
Changed “...BGATE pin to ground” to “...BGATE pit to CSN”
Changed “CSN” to “CSN”. Replaced “RCS with RCSZ” in the text and in Figure 19. Replaced “RSENSE” with RCS in
Figure 19
Replaced “RSENSE” with “RCS” in schematic
Modified bulk capacitance equation
42
1
8
9
12
20
22
28
32
37-39, 42
24
4020fd
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 representaFor more
information
www.linear.com/LTC4020
tion that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
41
LTC4020
Typical Application
Remote 24V to 55V (48V system) input to 12-cell Li-Ion (48V) PowerPath charger/system supply. 5A inductor current limit with 2.5A
battery charge current limit. Minimum VIN is 24V as input regulation limits voltage loss due to line impedance. Battery termination
voltage is 48V with maximum output voltage of 52.8V. Instant-on functionality limits minimum regulated output voltage to 40.8V.
VIN
24V TO 55V
RSENSEA
0.01
1µF
+
Si7850DP
56µF
×2
VOUT
MBRS360
Si7850DP
0.1µF
IHLP-5050FD-5A
Si7850DP
22µH
Si7850DP
4.7µF
+
56µF
×2
RSENSEB
0.01
4.7µF
SBR0560S1
PGND
INTVCC
SBR0560S1
PVIN
BG2
BG1
SW2
SW1
TG2
TG1
LTC4020
BST1
BST2
SGND
SGND
SENSGND
VC
0.033µF
RT, 100k
191k
1µF
BZX84C6V2L
1µF
SENSBOT
ITH
SENSTOP
VFBMAX
SENSVIN
RT
33k
680pF
365k
1.5nF
2nF
ILIMIT
CSOUT
20k
100Ω
CSP
SHDN
0.33µF
10k
CSN
VIN_REG
12k
MODE
BGATE
STAT1
BAT
STAT2
VFBMIN
TIMER
20k
VFB
SGNDBACK
RCS
0.02Ω
Si7465DP
FBG
RNG_SS
100Ω
356k
RNTC
10k
NTC
12-CELL Li-ION (48V)
4020 TA05
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PART NUMBER
DESCRIPTION
COMMENTS
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4020fd
42 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC4020
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC4020
LT 0416 REV D • PRINTED IN USA
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