LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
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DESCRIPTION
The LTC
®
3499/LTC3499B are synchronous, fixed frequency
step-up DC/DC power converters with integrated reverse
battery protection that protect and disconnect the devices
and load when the battery polarity is reversed while
delivering high efficiency in a small (3mm
×
3mm) DFN
package. True output disconnect eliminates inrush current
and allows zero load current in shutdown.
The devices feature an input voltage range of 1.8V to 5.5V
enabling operation from two alkaline or NiMH batteries. The
switching frequency is internally set at 1.2MHz allowing
the use of tiny surface mount inductors and capacitors.
A minimal number of external components are required
to generate output voltages ranging from 2V to 6V. The
LTC3499 features automatic Burst Mode operation to
increase efficiency at light loads, while the LTC3499B
features continuous switching at light loads.
The soft-start time is externally programmable through a
small capacitor. Anti-ring circuitry reduces EMI emissions
by damping the inductor in discontinuous mode. The
devices feature <1μA shutdown supply current, integrated
overvoltage protection and are available in both 8-pin
(3mm
×
3mm) DFN and 8-pin MSOP packages.
Reverse-Battery Protection for DC/DC Converter
and Load
High Efficiency: Up to 94%
Generates 5V at 175mA from a 1.8V Input
Operates from 1.8V to 5.5V Input Supply
2V to 6V Adjustable Output Voltage
Inrush Current Controlled During Start-Up
Output Disconnnect in Shutdown
Low Noise 1.2MHz PWM Operation
Tiny External Components
Automatic Burst Mode
®
Operation (LTC3499)
Continuous Switching at Light Loads (LTC3499B)
Overvoltage Protection
8-Lead (3mm
×
3mm
×
0.75mm) DFN
and MSOP Packages
APPLICATIONS
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Medical Equipment
Digital Cameras
MP3 Players
Handheld Instruments
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Two AA Cells to 5V Synchronous Boost Converter
V
IN
1.8V TO 3.2V
4.7μH
1.0
SHDN = 0V
V
OUT
= 0V
2.2μF
V
IN
LTC3499
ON OFF
SHDN
VC
100k
330pF
FB
SS
0.01μF
3499 TA01
Battery Current vs V
IN
+
SW
V
OUT
5V
175mA
1M
10μF
324k
BATTERY CURRENT (μA)
0.5
V
OUT
0
GND
–0.5
–1.0
–6
–4
–2
0
2
4
V
IN
AND SW VOLTAGE (V)
6
3499 TA01b
3499fb
1
LTC3499/LTC3499B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
to GND ..................................................... – 7V to 7V
V
OUT
to GND .............................................. – 0.3V to 7V
SW to V
OUT
................................................... – 7V to 1V
SW to GND
DC............................................................... –7V to 7V
Pulsed < 100ns ........................................... –7V to 8V
SHDN
to GND................................................. – 7V to 7V
FB, SS to GND............................................. – 0.3V to 7V
Operating Temperature Range
(Notes 3, 4)......................................... –40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
MSOP .............................................................. 300°C
PIN CONFIGURATION
TOP VIEW
SHDN
V
IN
SW
GND
1
2
3
4
9
8
7
6
5
VC
FB
V
OUT
SS
SHDN
V
IN
SW
GND
1
2
3
4
TOP VIEW
8
7
6
5
VC
FB
V
OUT
SS
DD PACKAGE
8-LEAD PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 45°C
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3499EDD#PBF
LTC3499BEDD#PBF
LTC3499EMS8#PBF
LTC3499BEMS8#PBF
TAPE AND REEL
LTC3499EDD#TRPBF
LTC3499BEDD#TRPBF
LTC3499EMS8#TRPBF
LTC3499BEMS8#TRPBF
PART MARKING
LBRB
LCDZ
LTBRC
LTCFB
PACKAGE DESCRIPTION
8-Lead Plastic DFN
8-Lead Plastic DFN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
The
l
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 2.4V, V
OUT
= 5V,
SHDN
= 2.4V, T
A
= T
J
unless otherwise noted.
SYMBOL
Supply
V
IN
V
OUT
V
FB
Minimum Start-Up Voltage
Output Voltage Adjust Range
FB Voltage
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ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
1.6
MAX
1.8
6
1.245
UNITS
V
V
V
3499fb
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1.195
1.220
2
LTC3499/LTC3499B
ELECTRICAL CHARACTERISTICS
SYMBOL
I
FB
I
VIN
I
SD
I
BURST
I
NMOS
I
PMOS
R
NMOS
R
PMOS
I
LIM
t
DLY, ILIM
D
MAX
D
MIN
f
OSC
G
mEA
I
SOURCE
I
SINK
I
SS
V
OV
V
OV(HYST)
Shutdown
V
SHDN(LOW)
V
SHDN(HIGH)
I
SD
Reverse Battery
I
VOUT,REVBATT
I
VIN,REVBATT
I
SHDN,REVBATT
V
OUT
Reverse-Battery Current
V
IN
and V
SW
Reverse-Battery Current
SHDN
Reverse-Battery Current
V
OUT
= 0V, V
IN
= V
SHDN
= V
SW
= –6V
V
OUT
= 0V, V
IN
= V
SHDN
= V
SW
= –6V
V
OUT
= 0V, V
IN
= V
SHDN
= V
SW
= –6V
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The
l
denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 2.4V, V
OUT
= 5V,
SHDN
= 2.4V, T
A
= T
J
unless otherwise noted.
PARAMETER
FB Input Current
V
IN
Quiescent Current
V
IN
Quiescent Current in Shutdown
Quiescent Current – Burst Mode Operation
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
NMOS Current Limit
Current Limit Delay to Output
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
Error Amplifier Transconductance
Error Amplifier Source Current
Error Amplifier Sink Current
SS Current Source
V
OUT
Overvoltage Threshold
V
OUT
Overvoltage Hysteresis
SHDN
Input Low
SHDN
Input High
SHDN
Input Current
Measured at SW
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CONDITIONS
V
FB
= 1.22V
No Output Load
SHDN
= 0V, V
OUT
= 0V
V
IN
Current at 2.4V (LTC3499 Only)
V
OUT
Current at 5V (LTC3499 Only)
V
SW
= 6V
V
OUT
= 6V, V
SW
= 0V
V
OUT
= 3.3V
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 5V
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MIN
TYP
3
300
0.1
20
1.5
0.1
0.1
0.45
0.4
0.58
0.45
MAX
50
600
1
UNITS
nA
μA
μA
μA
μA
5
5
μA
μA
Ω
Ω
Ω
Ω
A
ns
%
0.75
80
1
1
60
85
0
1.2
40
–5
5
1.4
Note 2
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%
MHz
μmhos
μA
μA
μA
V
mV
V
SS
= 1V
–3
6.8
400
0.2
1.2
1
5
–5
–5
V
V
μA
μA
μA
μA
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:
Specification is guaranteed by design and not 100% tested in
production.
Note 3:The
LTC3499E/LTC3499BE are guaranteed to meet device
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature are assured by design, characterization and
correlation with statistical process controls.
Note 4:
These ICs include overtemperature protection that is intended
to protect the devices during momentary overload conditions. Junction
temperatures will exceed 125°C when overtemperature protection is
active. Continuous operation above the specified maximum operating
temperature range may impair device reliability.
3499fb
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LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS
2-Cell to 5V Efficiency
vs Load Current (LTC3499 Only)
100
90
EFFICIENCY
EFFICIENCY (%)
80
70
60
50
40
0.1
1
POWER LOSS
1000
100
10
1
100000
10000
POWER LOSS (mW)
100
90
EFFICIENCY
80
EFFICIENCY (%)
70
POWER LOSS
60
50
40
30
0.1
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3V
1
100
LOAD CURRENT (mA)
10
10
1
100
T
A
= 25°C, unless otherwise noted.
2-Cell to 5V Efficiency
vs Load Current (LTC3499B Only)
100000
10000
EFFICIENCY (%)
1000
POWER LOSS (mW)
100
90
80
70
60
50
40
30
20
10
0
0.1
1
V
IN
= 3.2V
V
IN
= 2.4V
V
IN
= 1.8V
10
100
LOAD CURRENT (mA)
1000
3499 G17
Li-Ion to 5V Efficiency
vs Load Current (LTC3499 Only)
V
IN
= 3.2V
V
IN
= 2.4V
V
IN
= 1.8V
10
100
LOAD CURRENT (mA)
0.1
1000
0.1
1000
3499 G01
3499 G03
Current Limit Accuracy
vs Temperature
1.04
1.03
1.02
CURRENT LIMIT (A)
1.01
1.00
EFFICIENCY (%)
80
70
60
100
90
2-Cell to 3.3V Efficiency
vs Load Current (LTC3499 Only)
Burst Mode OUTPUT CURRENT THRESHOLD (mA)
100000
10000
EFFICIENCY
POWER LOSS (mW)
1000
100
10
POWER LOSS
50
40
0.1
1
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.8V
10
100
LOAD CURRENT (mA)
1
60
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3499 Only)
V
OUT
= 5V
50
40
30
20
10
0
0.99
0.98
0.97
0.96
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
3499 G04
0.1
1000
1.8
2.3
2.8
3.3
3.8
INPUT VOLTAGE (V)
4.3
4.8
3499 G05
3499 G02
Maximum Output Current
Capability vs V
IN
800
V
IN
> V
OUT
700
OUTPUT CURRENT (mA)
600
500
400
300
V
OUT
= 5V
200
100
0
1.5
2.5
3.5
V
IN
(V)
3499 G06
No Load Input Current vs V
IN
(LTC3499 Only)
200
Burst Mode QUIESCENT CURRENT (μA)
5.5
3499 G07
Burst Mode Quiescent Current
vs Temperature (LTC3499 Only)
30
25
20
15
10
5
0
–50
V
IN
> V
OUT
INPUT CURRENT (μA)
180
160
V
OUT
= 3.3V
140
120
100
80
60
40
20
0
V
OUT
= 3.3V
V
OUT
= 5V
4.5
5.5
1.5
2.5
3.5
V
IN
(V)
4.5
–25
0
25
50
TEMPERATURE (°C)
75
100
3499 G08
3499fb
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LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS
FB Voltage vs Temperature
1.2225
1.2220
1.2215
FB VOLTAGE (V)
1.2210
1.2205
1.2200
1.2195
1.2190
1.2185
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
3499 G09
T
A
= 25°C, unless otherwise noted.
V
IN
and SW Reverse-Battery
Current vs V
IN
and SW Voltage
1.0
REVERSE-BATTERY CURRENT (μA)
SHDN = 0V
V
OUT
= 0V
0.5
Oscillator Frequency
vs Temperature
30
Burst Mode QUIESCENT CURRENT (μA)
25
20
15
10
5
0
–50
0
–0.5
–25
0
25
50
TEMPERATURE (°C)
75
100
3499 G08
–1.0
–6
–4
–2
0
2
4
V
IN
AND SW VOLTAGE (V)
6
3499 G11
Burst Mode Operation
(LTC3499 Only)
Load Transient 50mA to 200mA
Fixed Frequency Discontinous
Mode Operation
V
OUT
50mV/DIV
V
OUT
200mV/DIV
200mA
50mA
V
IN
= 2.4V
200μs/DIV
V
OUT
= 5V
I
LOAD
= 50mA to 200mA
R
Z
= 100k
C
F
= 680pF
C
OUT
= 10μF
L = 4.7μH
3499 G13
SW
2V/DIV
I
L
50mA/DIV
V
IN
= 2.4V
20μs/DIV
V
OUT
= 5V
L = 4.7μH
C
OUT
= 10μF
C
FF
= 10pF (FEEDFORWARD CAPACITOR FROM
V
OUT
TO FB)
3499 G12
I
LOAD
100mA/DIV
I
L
100mA/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7μH
200ns/DIV
3499 G14
Soft-Start into 25Ω Load
V
IN
2V/DIV
SS
2V/DIV
V
OUT
2V/DIV
I
L
200mA/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7μH
C
SS
= 0.01μF
C
OUT
= 10μF
1ms/DIV
3499G15
Fixed Frequency Operation
SW
2V/DIV
I
L
100mA/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7μH
200ns/DIV
3499 G16
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