LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
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DESCRIPTIO
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
The LTC
®
3499/LTC3499B are synchronous, fixed fre-
quency 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 allow-
ing 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.
APPLICATIO S
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Medical Equipment
Digital Cameras
MP3 Players
Handheld Instruments
, LTC and LT 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 APPLICATIO
V
IN
1.8V TO 3.2V
Two AA Cells to 5V Synchronous Boost Converter
4.7µH
Battery Current vs V
IN
1.0
SHDN = 0V
V
OUT
= 0V
2.2µF
V
IN
LTC3499
SW
V
OUT
5V
175mA
1M
FB
10µF
324k
BATTERY CURRENT (µA)
+
0.5
ON OFF
SHDN
VC
V
OUT
0
100k
330pF
–0.5
SS
0.01µF
GND
–1.0
–6
3499 TA01
–4
U
–2
0
2
4
V
IN
AND SW VOLTAGE (V)
6
3499 TA01b
U
U
3499f
1
LTC3499/LTC3499B
ABSOLUTE
AXI U RATI GS
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SHDN
V
IN
SW
GND
1
2
3
4
9
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
ORDER PART NUMBER
LTC3499EDD
LTC3499BEDD
DD PART MARKING
LBRB
LCDZ
Order Options
Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
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
I
FB
I
VIN
I
SD
I
BURST
Minimum Start-Up Voltage
Output Voltage Adjust Range
FB Voltage
FB Input Current
V
IN
Quiescent Current
V
IN
Quiescent Current in Shutdown
Quiescent Current – Burst Mode Operation
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)
●
●
●
●
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
2
U
U
W
W W
U
W
(Note 1)
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
TOP VIEW
SHDN
V
IN
SW
GND
1
2
3
4
8
7
6
5
VC
FB
V
OUT
SS
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
ORDER PART NUMBER
LTC3499EMS8
LTC3499BEMS8
MS8 PART MARKING
1250
LTBRC
LTCFB
MIN
TYP
1.6
MAX
1.8
6
1.245
50
600
1
UNITS
V
V
V
nA
µA
µA
µA
µA
2
1.195
1.220
3
300
0.1
20
1.5
3499f
LTC3499/LTC3499B
ELECTRICAL CHARACTERISTICS
SYMBOL
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
SHDN Input Low
SHDN Input High
SHDN Input Current
PARAMETER
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
The
●
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.
CONDITIONS
V
SW
= 6V
V
OUT
= 6V, V
SW
= 0V
V
OUT
= 3.3V
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 5V
●
MIN
TYP
0.1
0.1
0.45
0.4
0.58
0.45
MAX
5
5
UNITS
µA
µA
Ω
Ω
Ω
Ω
A
ns
%
0.75
60
80
1
85
0
1.2
40
–5
5
1.4
Note 2
●
●
●
%
MHz
µmhos
µA
µA
µA
V
mV
V
SS
= 1V
–3
6.8
400
●
0.2
1.2
1
V
V
µA
µA
µA
µA
Measured at SW
●
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
●
●
●
5
–5
–5
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.
3499f
3
LTC3499/LTC3499B
TYPICAL PERFOR A CE CHARACTERISTICS
2-Cell to 5V Efficiency
vs Load Current (LTC3499 Only)
100
90
EFFICIENCY
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
80
70
60
50
40
0.1
1
POWER LOSS
V
IN
= 3.2V
V
IN
= 2.4V
V
IN
= 1.8V
10
100
LOAD CURRENT (mA)
Current Limit Accuracy
vs Temperature
1.04
1.03
1.02
100
90
Burst Mode OUTPUT CURRENT THRESHOLD (mA)
CURRENT LIMIT (A)
1.01
1.00
0.99
0.98
0.97
0.96
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
3499 G04
EFFICIENCY (%)
Maximum Output Current
Capability vs V
IN
800
V
IN
> V
OUT
700
V
IN
> V
OUT
INPUT CURRENT (µA)
Burst Mode QUIESCENT CURRENT (µA)
OUTPUT CURRENT (mA)
600
500
400
300
V
OUT
= 5V
200
100
0
1.5
2.5
3.5
V
IN
(V)
3499 G06
V
OUT
= 3.3V
4.5
4
U W
1
3499 G01
T
A
= 25°C unless noted.
2-Cell to 5V Efficiency
vs Load Current (LTC3499B Only)
100000
10000
Li-Ion to 5V Efficiency
vs Load Current (LTC3499 Only)
100000
10000
POWER LOSS (mW)
100
90
EFFICIENCY
80
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
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
POWER LOSS (mW)
1000
100
10
1000
0.1
1000
0.1
1000
3499 G03
2-Cell to 3.3V Efficiency
vs Load Current (LTC3499 Only)
100000
10000
EFFICIENCY
POWER LOSS (mW)
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3499 Only)
60
V
OUT
= 5V
50
40
30
20
10
0
80
70
60
POWER LOSS
50
40
0.1
1
V
IN
= 3V
V
IN
= 2.4V
V
IN
= 1.8V
10
100
LOAD CURRENT (mA)
1000
100
10
1
0.1
1000
1.8
2.3
2.8
3.3
3.8
INPUT VOLTAGE (V)
4.3
4.8
3499 G05
3499 G02
No Load Input Current vs V
IN
(LTC3499 Only)
200
180
160
140
120
100
80
60
40
20
0
V
OUT
= 3.3V
V
OUT
= 5V
Burst Mode Quiescent Current
vs Temperature (LTC3499 Only)
30
25
20
15
10
5
0
–50
5.5
1.5
2.5
3.5
V
IN
(V)
4.5
5.5
3499 G07
–25
0
25
50
TEMPERATURE (°C)
75
100
3499 G08
3499f
LTC3499/LTC3499B
TYPICAL PERFOR A CE CHARACTERISTICS
FB Voltage vs Temperature
1.2225
OSCILLATOR FREQUENCY (MHz)
REVERSE-BATTERY CURRENT (µA)
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
Burst Mode Operation
(LTC3499 Only)
V
OUT
50mV/DIV
I
L
50mA/DIV
20µs/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7µH
C
OUT
= 10µF
C
FF
= 10pF (FEEDFORWARD CAPACITOR FROM
V
OUT
TO FB)
3499 G12
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
34991G15
U W
T
A
= 25°C unless noted.
V
IN
and SW Reverse-Battery
Current vs V
IN
and SW Voltage
1.0
SHDN = 0V
V
OUT
= 0V
0.5
Oscillator Frequency
vs Temperature
1.4
1.3
1.2
0
1.1
–0.5
1.0
–50
–1.0
–25
0
25
50
TEMPERATURE (°C)
75
100
3499 G08
–6
–4
–2
0
2
4
V
IN
AND SW VOLTAGE (V)
6
3499 G11
Load Transient 50mA to 200mA
Fixed Frequency Discontinous
Mode Operation
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
LOAD
100mA/DIV
I
L
100mA/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7µH
200ns/DIV
3499 G14
Fixed Frequency Operation
SW
2V/DIV
I
L
100mA/DIV
V
IN
= 2.4V
V
OUT
= 5V
L = 4.7µH
200ns/DIV
3499 G16
3499f
5
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