LTC3528/LTC3528B
1A, 1MHz Synchronous
Step-Up DC/DC Converters
in 3mm
×
2mm DFN
FEATURES
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DESCRIPTION
The LTC
®
3528/LTC3528B are synchronous, fixed frequency
step-up DC/DC converters with output disconnect. High
efficiency synchronous rectification, in addition to a 700mV
start-up voltage and operation down to 500mV once
started, provides longer run time for single or multiple
cell battery-powered products.
A switching frequency of 1MHz minimizes solution
footprint by allowing the use of tiny, low profile induc-
tors and ceramic capacitors. The current mode PWM is
internally compensated, simplifying the design process.
The LTC3528 enters Burst Mode operation at light loads,
while the LTC3528B features continuous switching at light
loads. Anti-ringing circuitry reduces EMI by damping the
inductor in discontinuous mode. Additional features include
a low shutdown current, open-drain power good output,
short-circuit protection and thermal overload protection.
The LTC3528/LTC3528B are offered in an 8-lead 3mm
×
2mm
×
0.75mm DFN package.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered
trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
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Delivers 3.3V at 200mA from a Single Alkaline/
NiMH Cell or 3.3V at 400mA from Two Cells
V
IN
Start-Up Voltage: 700mV
1.6V to 5.25V V
OUT
Range
Up to 94% Efficiency
Output Disconnect
1MHz Fixed Frequency Operation
V
IN
> V
OUT
Operation
Integrated Soft-Start
Current Mode Control with Internal Compensation
Burst Mode
®
Operation with 12µA Quiescent Current
(LTC3528)
Low Noise PWM Operation (LTC3528B)
Internal Synchronous Rectifier
Logic Controlled Shutdown: <1µA
Anti-Ringing Control
Low Profile (3mm
×
2mm
×
0.75mm) DFN Package
APPLICATIONS
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Medical Instruments
Flash-Based MP3 Players
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
100
4.7µH
SW
V
IN
4.7µF
V
OUT
499k
FB
287k
3528 TA01a
Efficiency and Power Loss
90
V
OUT
3.3V
400mA
10µF
80
EFFICIENCY (%)
70
60
POWER LOSS
50
40
30
0.01
0.1
1
10
100
0.1
0.01
1000
3528 TA01b
V
OUT
= 3.3V
V
IN
= 2.4V
1000
100
POWER LOSS (mW)
V
IN
1.8V TO 3.2V
EFFICIENCY
10
1
LTC3528
PGOOD
SHDN
GND
33pF
OFF ON
LOAD CURRENT (mA)
3528fd
1
LTC3528/LTC3528B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
SHDN
1
FB 2
PGOOD 3
V
OUT
4
9
8 V
IN
7 SGND
6 PGND
5 SW
V
IN
Voltage ................................................... –0.3V to 6V
SW Voltage
DC............................................................ –0.3V to 6V
Pulsed < 100ns ........................................ –0.3V to 7V
SHDN,
FB Voltage ........................................ –0.3V to 6V
V
OUT
............................................................. –0.3V to 6V
PGOOD......................................................... –0.3V to 6V
Operating Junction Temperature Range
(Notes 2, 5) ............................................ –40°C to 125°C
Storage Temperature Range................... –65°C to 125°C
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 76°C/W (NOTE 6)
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3528EDDB#PBF
LTC3528BEDDB#PBF
TAPE AND REEL
LTC3528EDDB#TRPBF
LTC3528BEDDB#TRPBF
PART MARKING
LCYD
LDDG
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°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/
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Start-Up Voltage
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current—Shutdown
Quiescent Current—Active
Quiescent Current—Burst
P-Channel MOSFET Switch Leakage Current
N-Channel MOSFET Switch On-Resistance
P-Channel MOSFET Switch On-Resistance
N-Channel MOSFET Current Limit
Current Limit Delay Time to Output
Maximum Duty Cycle
Minimum Duty Cycle
Frequency
(Note 3)
V
FB
= 1.15V
V
FB
= 1.3V
CONDITIONS
I
LOAD
= 1mA
T
A
= 0°C to 85°C
(Note 7)
V
FB
= 1.3V
The
l
denotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise noted.
MIN
l
l
l
TYP
0.70
MAX
0.88
5.25
5.25
UNITS
V
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
A
ns
%
1.7
1.6
1.170
1.200
1
0.01
300
12
0.1
0.1
0.175
0.250
1.230
50
1
500
20
10
10
V
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching (Note 4)
Measured on V
OUT
, FB > 1.230V
V
SW
= 5V, V
OUT
= 0V
N-Channel MOSFET Switch Leakage Current V
SW
= 5V
l
1.0
88
0.7
1.5
60
93
0
1.0
1.3
l
l
l
%
MHz
3528fd
2
LTC3528/LTC3528B
ELECTRICAL CHARACTERISTICS
PARAMETER
SHDN
Input High Voltage
SHDN
Input Low Voltage
SHDN
Input Current
PGOOD Threshold Percentage
PGOOD Low Voltage
PGOOD Leakage Current
V
SHDN
= 1.2V
Referenced to Feedback Voltage Falling
I
PGOOD
= 1mA
V
OUT
= 1.6V, I
PGOOD
= 1mA
V
PGOOD
= 5.5V
–7
0.3
–10
0.05
0.05
0.01
CONDITIONS
The
l
denotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise noted.
MIN
0.88
0.25
1
–13
0.1
0.2
1
TYP
MAX
UNITS
V
V
µA
%
V
V
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:
The LTC3528/LTC3528B are tested under pulsed load conditions
such that T
J
≈ T
A
. The LTC3528E/LTC3528BE are guaranteed to meet
specifications from 0°C to 85°C junction temperature. Specifications
over –40°C to 125°C operating junction temperature range are assured
by design, characterization and correlation with statistical process
controls. 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 impedance
and other environmental factors. The junction temperature (T
J
, in °C) is
calculated from the ambient temperature (T
A
, in °C) and power dissipation
(P
D
, in Watts) according to the formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
= 76°C/W is the package thermal impedance.
Note 3:
Specification is guaranteed by design and not 100% tested in
production.
Note 4:
Current measurements are made when the output is not switching.
Note 5:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
Note 6:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
76°C/W.
Note 7:
The IC is tested in a feedback loop to make the measurement.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and V
IN
for V
OUT
= 1.8V (LTC3528)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
V
IN
= 1V
V
IN
= 1.2V
V
IN
= 1.5V
10
100
1
LOAD CURRENT (mA)
0.1
POWER
LOSS
10
EFFICIENCY
100
POWER LOSS (mW)
EFFICIENCY (%)
1000
100
90
80
70
60
50
40
30
20
10
0
0.01
(T
A
= 25°C unless otherwise noted)
Efficiency vs Load Current and V
IN
for V
OUT
= 3V (LTC3528)
EFFICIENCY
1000
100
POWER LOSS (mW)
10
POWER
LOSS
1
1
0.01
1000
V
IN
= 1V
V
IN
= 1.5V
V
IN
= 2.4V
0.1
10
100
1
LOAD CURRENT (mA)
0.1
0.01
1000
3528 G01
3528 G26
3528fd
3
LTC3528/LTC3528B
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and V
IN
for V
OUT
= 3.3V (LTC3528)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
0.01
0.1
1
10
POWER
LOSS
V
IN
= 1.2V
V
IN
= 1.8V
V
IN
= 2.4V
V
IN
= 3V
100
LOAD CURRENT (mA)
3528 G02
(T
A
= 25°C unless otherwise noted)
No-Load Input Current vs V
IN
(LTC3528)
1000
130
110
100
POWER LOSS (mW)
90
I
IN
(µA)
70
50
30
10
V
OUT
= 1.8V
V
OUT
= 3V
V
OUT
= 3.3V
V
OUT
= 5V
Efficiency vs Load Current and V
IN
for V
OUT
= 5V (LTC3528)
1000
100
90
80
EFFICIENCY (%)
70
60
50
40
30
0.01
0.1
1
10
POWER
LOSS
V
IN
= 1.2V
V
IN
= 2.4V
V
IN
= 3.6V
V
IN
= 4.2V
100
LOAD CURRENT (mA)
3528 G03
EFFICIENCY
100
POWER LOSS (mW)
10
1
0.1
EFFICIENCY
10
1
0.01
1000
0.1
1000
1
2
3
V
IN
(V)
4
5
3528 G04
Maximum Output Current vs V
IN
800
700
600
10000
Minimum Load Resistance During
Start-Up vs V
IN
130
120
110
1000
DELAY (µs)
R
LOAD
( )
100
90
80
70
Start-Up Delay Time vs V
IN
I
OUT
(mA)
500
400
300
200
100
0
1
1.5
2
3
2.5
V
IN
(V)
V
OUT
= 1.8V
V
OUT
= 3.3V
V
OUT
= 5V
3.5
4
4.5
3528 G05
100
60
10
0.7
0.8
V
IN
(V)
0.9
1
3528 G06
50
1
1.5
2
3
2.5
V
IN
(V)
3.5
4
4.5
3528 G07
Burst Mode Threshold Current
vs V
IN
40
V
OUT
= 1.8V
50
40
EXIT BURST
I
OUT
(mA)
I
OUT
(mA)
30
20
20
ENTER BURST
10
Burst Mode Threshold Current
vs V
IN
V
OUT
= 3V
60
Burst Mode Threshold Current
vs V
IN
V
OUT
= 3.3V
30
EXIT BURST
ENTER BURST
I
OUT
(mA)
40
EXIT BURST
ENTER BURST
20
10
0
1
1.1
1.3
1.2
V
IN
(V)
1.4
1.5
3528 G08
0
1
1.5
V
IN
(V)
2
2.5
3528 G09
0
1
1.5
2
V
IN
(V)
2.5
3
3528 G10
3528fd
4
LTC3528/LTC3528B
TYPICAL PERFORMANCE CHARACTERISTICS
Burst Mode Threshold Current
vs V
IN
60
V
OUT
= 5V
FREQUENCY CHANGE (%)
0.50
0.25
0
–0.25
R
DS(ON)
(m )
–0.50
–0.75
–1.00
–1.25
–1.50
–1.75
–2.00
0
1
2
V
IN
(V)
3528 G11
(T
A
= 25°C unless otherwise noted)
Oscillator Frequency Change
vs V
OUT
NORMALIZED TO V
OUT
= 3V
450
400
350
300
250
200
150
R
DS(ON)
vs V
OUT
40
I
OUT
(mA)
EXIT BURST
ENTER BURST
20
PMOS
NMOS
3
4
–2.25
1.5
2
2.5
3.5
3
V
OUT
(V)
4
4.5
5
100
1.5
2
2.5
3.5
3
V
OUT
(V)
4
4.5
5
3528 G12
3528 G13
Oscillator Frequency Change
vs Temperature
2
1
FREQUENCY CHANGE (%)
0
–1
–2
–3
–4
–50 –25
40
30
R
DS(ON)
Change vs Temperature
1.200
V
FB
vs Temperature
1.199
CHANGE (%)
20
10
0
1.197
–10
–20
–50 –25
1.196
–50
V
FB
(V)
50
25
75
0
TEMPERATURE (˚C)
100
125
1.198
50
25
75
0
TEMPERATURE (˚C)
100
125
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3528 G14
3528 G15
3528 G16
Start-Up Voltage vs Temperature
850
13.5
Burst Mode Quiescent Current vs
V
OUT
(LTC3528)
V
IN
= 1.2V
V
OUT
20mV/DIV
CURRENT (µA)
12.5
I
L
200mA/DIV
Fixed Frequency V
OUT
Ripple and
Inductor Current Waveforms
START-UP VOLTAGE (mV)
800
750
700
11.5
650
V
IN
= 1.2V
V
OUT
= 3.3V
C
OUT
= 22µF
C
FF
= 33pF
I
OUT
= 100mA
1
2
3
V
OUT
(V)
4
5
3528 G18
2µs/DIV
3528 G19
600
–50
–25
50
0
75
25
TEMPERATURE (°C)
100
125
10.5
3528 G17
3528fd
5
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