LTC3528-2
1A, 2MHz Synchronous
Step-Up DC/DC Converter
in 2mm
×
3mm DFN
FEATURES
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DESCRIPTION
The LTC
®
3528-2 is a synchronous, fixed frequency step-up
DC/DC converter 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 2MHz minimizes solution foot-
print by allowing the use of tiny, low profile inductors
and ceramic capacitors. The current mode PWM is inter-
nally compensated, simplifying the design process. The
LTC3528-2 enters Burst Mode operation at light loads.
Anti-ringing circuitry reduces EMI by damping the induc-
tor in discontinuous mode. Additional features include a
low shutdown current, open-drain power good output,
short-circuit protection and thermal overload protection.
The LTC3528-2 is offered in an 8-lead 2mm
×
3mm
×
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.
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
0.50V to 5.5V Input Range
1.6V to 5.25V V
OUT
Range
Up to 94% Efficiency
Output Disconnect
2MHz Fixed Frequency Operation
V
IN
> V
OUT
Operation
Integrated Soft-Start
Current Mode Control with Internal Compensation
Burst Mode
®
Operation with 12µA Quiescent Current
Internal Synchronous Rectifier
Logic Controlled Shutdown: <1µA
Anti-Ringing Control
Low Profile (2mm
×
3mm
×
0.75mm) DFN Package
APPLICATIONS
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Medical Instruments
Noise Canceling Headphones
Wireless Mice
Bluetooth Headsets
TYPICAL APPLICATION
Efficiency and Power Loss
100
2.2µH
SW
V
IN
4.7µF
V
OUT
499k
68pF
LTC3528-2
PGOOD
OFF ON
SHDN
GND
FB
287k
35282 TA01a
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
V
OUT
= 3.3V
V
IN
= 2.4V
EFFICIENCY
1000
100
POWER LOSS (mW)
10
1
0.1
0.01
1000
V
IN
1.8V TO 3.2V
V
OUT
3.3V
400mA
10µF
POWER LOSS
0
0.01
0.1
1
10
100
LOAD CURRENT (mA)
35282 TA01b
35282fb
1
LTC3528-2
ABSOLUTE MAXIMUM RATINGS
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
Junction Temperature ........................................... 125°C
Storage Temperature Range .................. –65°C to 125°C
(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
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-2#PBF
TAPE AND REEL
LTC3528EDDB-2#TRPBF
PART MARKING
LDNZ
PACKAGE DESCRIPTION
8-Lead (3mm × 2mm) Plastic DFN
TEMPERATURE RANGE
–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
V
IN
Range
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
(Note 3)
V
FB
= 1.15V
CONDITIONS
The
l
denotes the specifications which apply over the specified operating
junction 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
5.5
0.88
5.25
5.25
UNITS
V
V
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
A
ns
%
35282fb
Operating, Excluding Start-Up
I
LOAD
= 1mA
T
A
= 0°C to 85°C
(Note 7)
V
FB
= 1.3V
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
0.5
1.7
1.6
1.170
1.200
1
0.01
300
12
0.1
0.1
0.175
0.250
l
1.230
50
1
500
20
10
10
N-Channel MOSFET Switch Leakage Current V
SW
= 5V
l
1.0
87
1.5
60
92
l
2
LTC3528-2
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Duty Cycle
Frequency
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
V
FB
= 1.3V
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise noted.
MIN
1.8
0.88
0.25
1
–13
0.1
0.2
1
TYP
2.0
MAX
0
2.4
UNITS
%
MHz
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 LTC3528-2 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3528E-2 is 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
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
(T
A
= 25°C unless otherwise noted)
Efficiency vs Load Current
and V
IN
for V
OUT
= 3V
EFFICIENCY
1000
100
POWER LOSS (mW)
10
POWER
LOSS
1
1
0.01
1000
0
0.01
V
IN
= 1V
V
IN
= 1.5V
V
IN
= 2.4V
0.1
10
100
1
LOAD CURRENT (mA)
0.1
0.01
1000
35282 G01
35282 G26
35282fb
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LTC3528-2
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
and V
IN
for V
OUT
= 3.3V
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)
35282 G02
(T
A
= 25°C unless otherwise noted)
Efficiency vs Load Current
and V
IN
for V
OUT
= 5V
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)
35282 G03
No-Load Input Current vs V
IN
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
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
35282 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
100
60
10
0.7
0.8
V
IN
(V)
0.9
1
35282 G06
50
1
1.5
2
3
2.5
V
IN
(V)
3.5
4
4.5
35282 G05
35282 G07
Burst Mode Threshold Current
vs V
IN
80
V
OUT
= 1.8V
80
Burst Mode Threshold Current
vs V
IN
V
OUT
= 3V
80
Burst Mode Threshold Current
vs V
IN
V
OUT
= 3.3V
60
I
OUT
(mA)
EXIT BURST
I
OUT
(mA)
60
EXIT BURST
I
OUT
(mA)
40
ENTER BURST
20
60
EXIT BURST
40
ENTER BURST
40
ENTER BURST
20
20
0
1
1.1
1.3
1.2
V
IN
(V)
1.4
1.5
35282 G08
0
1
1.5
V
IN
(V)
2
2.5
35282 G09
0
1
1.5
2
V
IN
(V)
2.5
3
35282 G10
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LTC3528-2
TYPICAL PERFORMANCE CHARACTERISTICS
Burst Mode Threshold Current
vs V
IN
80
V
OUT
= 5V
FREQUENCY CHANGE (%)
0.50
0.25
0
60
I
OUT
(mA)
EXIT BURST
40
ENTER BURST
20
–0.25
R
DS(ON)
(m )
–0.50
–0.75
–1.00
–1.25
–1.50
–1.75
–2.00
0
1
1.5
2
2.5
V
IN
(V)
3
3.5
4
–2.25
1.5
2
2.5
3.5
3
V
OUT
(V)
4
4.5
5
(T
A
= 25°C unless otherwise noted)
Oscillator Frequency Change
vs V
OUT
450
400
350
300
250
200
150
R
DS(ON)
vs V
OUT
PMOS
NMOS
100
1.5
2
2.5
3.5
3
V
OUT
(V)
4
4.5
5
35242 G11
35282 G12
35282 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)
1.198
50
25
75
0
TEMPERATURE (˚C)
100
125
50
25
75
0
TEMPERATURE (˚C)
100
125
–25
75
0
25
50
TEMPERATURE (°C)
100
125
35282 G14
35282 G15
35282 G16
Output Voltage vs Load Current
for V
OUT
= 5V
0.20
CHANGE IN OUTPUT VOLTAGE (%)
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
0
200
400
600
3528-2 G27
Output Voltage vs Load Current
for V
OUT
= 3.3V
0.20
CHANGE IN OUTPUT VOLTAGE (%)
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
0
50
100
150
200
35282 G28
Start-Up Voltage vs Temperature
850
V
IN
= 3.6V
V
IN
= 1.2V
START-UP VOLTAGE (mV)
800
750
700
650
600
–50
–25
LOAD CURRENT (mA)
LOAD CURRENT (mA)
50
0
75
25
TEMPERATURE (°C)
100
125
35282 G17
35282fb
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