LTC3528BEDDB#PBF - Linear Technology Corporation

LTC3528-2

35282fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

1A, 2MHz Synchronous

Step-Up DC/DC Converter

in 2mm × 3mm DFN

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

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 LTC3528-2 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.

n Delivers 3.3V at 200mA from a Single Alkaline/

NiMH Cell or 3.3V at 400mA from Two Cells

n VIN Start-Up Voltage: 700mV

n 0.50V to 5.5V Input Range

n 1.6V to 5.25V VOUT Range

n Up to 94% Efﬁciency

n Output Disconnect

n 2MHz Fixed Frequency Operation

n VIN > VOUT Operation

n Integrated Soft-Start

n Current Mode Control with Internal Compensation

n Burst Mode

Operation with 12µA Quiescent Current

n Internal Synchronous Rectiﬁer

n Logic Controlled Shutdown: <1µA

n Anti-Ringing Control

n Low Proﬁle (2mm × 3mm × 0.75mm) DFN Package

n Medical Instruments

n Noise Canceling Headphones

n Wireless Mice

n Bluetooth Headsets

Efﬁciency and Power Loss

LOAD CURRENT (mA)

0.01

100

35282 TA01b

0.1 1 10 1000

100

1000

0.1

0.01

EFFICIENCY (%)

POWER LOSS (mW)

EFFICIENCY

POWER LOSS

VOUT = 3.3V

VIN = 2.4V

VIN

499k

2.2µH

287k

4.7µF

10µF

68pF

35282 TA01a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

1.8V TO 3.2V

VOUT

3.3V

400mA

OFF ON

GND

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.

LTC3528-2

35282f

ELECTRICAL CHARACTERISTICS

ABSOLUTE MAXIMUM RATINGS

VIN 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

VOUT ............................................................. –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)

PARAMETER CONDITIONS MIN TYP MAX UNITS

VIN Range Operating, Excluding Start-Up l0.5 5.5 V

Minimum Start-Up Voltage ILOAD = 1mA l0.70 0.88 V

Output Voltage Adjust Range

TA = 0°C to 85°C

l1.7

1.6

5.25

Feedback Voltage (Note 7) l1.170 1.200 1.230 V

Feedback Input Current VFB = 1.3V 1 50 nA

Quiescent Current—Shutdown VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V 0.01 1 µA

Quiescent Current—Active Measured on VOUT, Nonswitching (Note 4) 300 500 µA

Quiescent Current—Burst Measured on VOUT

, FB > 1.230V 12 20 µA

N-Channel MOSFET Switch Leakage Current VSW = 5V 0.1 10 µA

P-Channel MOSFET Switch Leakage Current VSW = 5V, VOUT = 0V 0.1 10 µA

N-Channel MOSFET Switch On Resistance 0.175 Ω

P-Channel MOSFET Switch On Resistance 0.250 Ω

N-Channel MOSFET Current Limit l1.0 1.5 A

Current Limit Delay Time to Output (Note 3) 60 ns

Maximum Duty Cycle VFB = 1.15V l87 92 %

The l denotes the speciﬁcations which apply over the speciﬁed operating

junction temperature range, otherwise speciﬁcations are at TA = 25°C (Note 2). VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.

TOP VIEW

DDB PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

1SHDN

PGOOD

VOUT

VIN

SGND

PGND

TJMAX = 125°C, θJA = 76°C/W (NOTE 6)

EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB

LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC3528EDDB-2#PBF LTC3528EDDB-2#TRPBF LDNZ 8-Lead (3mm × 2mm) Plastic DFN –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/

PIN CONFIGURATION

ORDER INFORMATION

LTC3528-2

35282fa

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

TJ ≈ TA. 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 (TJ, in °C) is calculated from the ambient temperature (TA, in

°C) and power dissipation (PD, in Watts) according to the formula:

TJ = TA + (PD • θJA)

where θJA = 76°C/W is the package thermal impedance.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Duty Cycle VFB = 1.3V l0 %

Frequency l1.8 2.0 2.4 MHz

SHDN Input High Voltage 0.88 V

SHDN Input Low Voltage 0.25 V

SHDN Input Current VSHDN = 1.2V 0.3 1 µA

PGOOD Threshold Percentage Referenced to Feedback Voltage Falling –7 –10 –13 %

PGOOD Low Voltage IPGOOD = 1mA

VOUT = 1.6V, IPGOOD = 1mA

0.05

0.1

0.2

PGOOD Leakage Current VPGOOD = 5.5V 0.01 1 µA

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). VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.

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

(TA = 25°C unless otherwise noted)

Efﬁciency vs Load Current

and VIN for VOUT = 1.8V

Efﬁciency vs Load Current

and VIN for VOUT = 3V

LOAD CURRENT (mA)

0.01

EFFICIENCY (%)

POWER LOSS (mW)

100

35282 G01

100

1000

0.1

0.01

0.1 110 1000

VIN = 1V

VIN = 1.2V

VIN = 1.5V

EFFICIENCY

POWER

LOSS

LOAD CURRENT (mA)

0.01

EFFICIENCY (%)

POWER LOSS (mW)

100

35282 G26

100

1000

0.1

0.01

0.1 110 1000

VIN = 1V

VIN = 1.5V

VIN = 2.4V

EFFICIENCY

POWER

LOSS

LTC3528-2

35282f

Maximum Output Current vs VIN

Minimum Load Resistance During

Start-Up vs VIN Start-Up Delay Time vs VIN

Efﬁciency vs Load Current

and VIN for VOUT = 5V

Efﬁciency vs Load Current

and VIN for VOUT = 3.3V

VIN (V)

IOUT (mA)

700

2.5

35282 G05

400

200

1.5 2 3

100

800

600

500

300

3.5 4 4.5

VOUT = 1.8V

VOUT = 3.3V

VOUT = 5V

VIN (V)

0.7

RLOAD (Ω)

1000

100

10000

0.8 0.9 1

35282 G06

VIN (V)

DELAY (µs)

120

2.5

35282 G07

1.5 2 3

130

110

100

3.5 4 4.5

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C unless otherwise noted)

LOAD CURRENT (mA)

0.01

100

35282 G02

0.1 1 10 1000

100

1000

0.1

0.01

EFFICIENCY (%)

POWER LOSS (mW)

VIN = 1.2V

VIN = 1.8V

VIN = 2.4V

VIN = 3V

EFFICIENCY

POWER

LOSS

LOAD CURRENT (mA)

0.01

100

35282 G03

0.1 1 10 1000

100

1000

0.1

EFFICIENCY (%)

POWER LOSS (mW)

VIN = 1.2V

VIN = 2.4V

VIN = 3.6V

VIN = 4.2V

EFFICIENCY

POWER

LOSS

VIN (V)

IIN (µA)

110

130

2 3 4 5

35282 G04

VOUT = 1.8V

VOUT = 3V

VOUT = 3.3V

VOUT = 5V

No-Load Input Current vs VIN

Burst Mode Threshold Current

vs VIN

Burst Mode Threshold Current

vs VIN

Burst Mode Threshold Current

vs VIN

VIN (V)

IOUT (mA)

1.4

35282 G08

01.1 1.2 1.3 1.5

80 VOUT = 1.8V

ENTER BURST

EXIT BURST

VIN (V)

IOUT (mA)

35282 G09

01.5 22.5

80 VOUT = 3V

ENTER BURST

EXIT BURST

VIN (V)

IOUT (mA)

35282 G10

01.5 22.5

80 VOUT = 3.3V

ENTER BURST

EXIT BURST

LTC3528-2

35282fa

Oscillator Frequency Change

vs VOUT RDS(ON) vs VOUT

Oscillator Frequency Change

vs Temperature RDS(ON) Change vs Temperature VFB vs Temperature

Start-Up Voltage vs Temperature

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C unless otherwise noted)

Burst Mode Threshold Current

vs VIN

VIN (V)

IOUT (mA)

1.5 2 2.5 3

35242 G11

3.5 4

VOUT = 5V

ENTER BURST

EXIT BURST

VOUT (V)

1.5

FREQUENCY CHANGE (%)

–1.50

0.25

0.50

2.5 3.5 4

35282 G12

–2.00

–0.50

–1.00

–1.75

–0.25

–2.25

–0.75

–1.25

234.5 5

VOUT (V)

1.5

300

350

450

3 4

35282 G13

250

200

2 2.5 3.5 4.5 5

150

100

400

RDS(ON) (mΩ)

PMOS

NMOS

TEMPERATURE (˚C)

–50

FREQUENCY CHANGE (%)

25 75

35282 G14

–1

–2

–25 0 50 100 125

–3

–4

TEMPERATURE (°C)

–50

1.196

VFB (V)

1.197

1.198

1.199

1.200

–25 0 25 50

35282 G16

75 100 125

TEMPERATURE (°C)

–50 –25

600

START-UP VOLTAGE (mV)

700

850

050 75

35282 G17

650

800

750

25 100 125

Output Voltage vs Load Current

for VOUT = 5V

LOAD CURRENT (mA)

CHANGE IN OUTPUT VOLTAGE (%)

–0.05

0.05

3528-2 G27

–0.10

–0.15

–0.20 200 400

0.10

0.15

0.20 VIN = 3.6V

600

Output Voltage vs Load Current

for VOUT = 3.3V

LOAD CURRENT (mA)

CHANGE IN OUTPUT VOLTAGE (%)

–0.05

0.05

35282 G28

–0.10

–0.15

–0.20 10050 150

0.10

0.15

0.20 VIN = 1.2V

200

TEMPERATURE (˚C)

–50

CHANGE (%)

25 75

35282 G15

–25 0 50 100 125

–10

–20

LTC3528-2

35282f

Load Step Response (Burst Mode

Operation, 3.6V to 5V)

VOUT and IIN During Soft-Start

TYPICAL PERFORMANCE CHARACTERISTICS

(TA = 25°C unless otherwise noted)

VOUT

1V/DIV

SHDN PIN

200µs/DIV 35282 G21

VIN = 1.2V

VOUT = 3.3V

COUT = 10µF

L = 2.2µH

IIN

200mA/DIV

VOUT

100mV/DIV

20µs/DIV 35282 G23

VIN = 3.6V

VOUT = 5V

COUT = 10µF

L = 2.2µH

LOAD CURRENT = 20mA TO 550mA

LOAD

CURRENT

200mA/DIV

Load Step Response (Fixed

Frequency, 1.2V to 3.3V)

Load Step Response (Burst Mode

Operation, 1.2V to 3.3V)

VOUT

100mV/DIV

20µs/DIV 35282 G24

VIN = 1.2V

VOUT = 3.3V

COUT = 10µF

L = 2.2µH

LOAD CURRENT = 20mA TO 170mA

LOAD

CURRENT

100mA/DIV

VOUT

100mV/DIV

20µs/DIV 35282 G25

VIN = 1.2V

VOUT = 3.3V

COUT = 10µF

L = 2.2µH

LOAD CURRENT = 10mA TO 160mA

LOAD

CURRENT

100mA/DIV

Load Step Response (Fixed

Frequency, 3.6V to 5V)

VOUT

100mV/DIV

20µs/DIV 35282 G22

VIN = 3.6V

VOUT = 5V

COUT = 10µF

L = 2.2µH

LOAD CURRENT = 100mA TO 550mA

LOAD

CURRENT

200mA/DIV

Fixed Frequency VOUT Ripple and

Inductor Current Waveforms

VOUT

20mV/DIV

500ns/DIV 35282 G19

VIN = 1.2V

VOUT = 3.3V

COUT = 10µF

CFF = 33pF

IOUT = 100mA

L = 2.2µH

200mA/DIV

Burst Mode Waveforms

5µs/DIV 35282 G20

VIN = 3.6V

VOUT = 5V

COUT = 10µF

CFF = 33pF

ILOAD = 30mA

VOUT

50mV/DIV

INDUCTOR

CURRENT

100mA/DIV

LTC3528-2

35282fa

PIN FUNCTIONS

SHDN (Pin 1): Logic Controlled Shutdown Input. There is

an internal 4M pull-down resistor on this pin.

• SHDN = High: Normal operation

• SHDN = Low: Shutdown, quiescent current < 1µA

FB (Pin 2): Feedback Input. Connect resistor divider tap

to this pin. The output voltage can be adjusted from 1.6V

to 5.25V by:

VOUT =1.20V •1+R2











PGOOD (Pin 3): Power Good Comparator Output. This

open-drain output is low when VFB < 10% from its regu-

lation voltage.

VOUT (Pin 4): Output Voltage Sense and Drain Connection

of the Internal Synchronous Rectiﬁer. PCB trace length

from VOUT to the output ﬁlter capacitor (4.7µF minimum)

should be as short and wide as possible.

SW (Pin 5): Switch Pin. Connect inductor between SW

and VIN. Keep PCB trace lengths as short and wide as

possible to reduce EMI. If the inductor current falls to

zero, or SHDN is low, an internal anti-ringing switch is

connected from SW to VIN to minimize EMI.

PGND (Pin 6): Power Ground. Provide a short direct PCB

path between PGND and the (–) side of the input and

output capacitors.

SGND (Pin 7): Signal Ground. Provide a short direct PCB

path between SGND and the (–) side of the input and

output capacitors.

VIN (Pin 8): Battery Input Voltage. Connect a minimum of

1µF ceramic decoupling capacitor from this pin to ground.

GND (Exposed Pad Pin 9): The exposed pad must be

soldered to the PCB ground plane. It serves as another

ground connection and as a means of conducting heat

away from the die.

LTC3528-2

35282f

BLOCK DIAGRAM

–

GATE DRIVERS

AND

ANTI-CROSS

CONDUCTION

LOGIC

CLK

UVLO PK

COMP

SLOPE

COMP

IZERO

COMP

ERROR AMP

SLEEP COMP

IZERO

WAKE

EXPOSED

PAD

–

WELL

SWITCH

MODE

CONTROL

UVLO

VREF VREF

SHDN

VBEST

START-UP

2MHz

OSC

TSD

THERMAL

SHUTDOWN

ANTI-RING

VSEL

VIN

VOUT

2.2µH

SHUTDOWN

CLAMP

BURST

SOFT-START

VREF

–

VREF – 10%

VOUT

SGND

35282 BD

PGND

COUT

10µF

VOUT

1.6V

TO 5.25V

PGOOD

CIN

4.7µF

VIN

0.7V

TO 5V

LTC3528-2

35282fa

OPERATION

The LTC3528-2 is a 2MHz synchronous boost converter

housed in an 8-lead 3mm × 2mm DFN package. With the

ability to start up and operate from inputs less than 0.88V,

the device features ﬁxed frequency, current mode PWM

control for exceptional line and load regulation. The cur-

rent mode architecture with adaptive slope compensation

provides excellent transient load response and requires

minimal output ﬁltering. Internal soft-start and internal

loop compensation simpliﬁes the design process while

minimizing the number of external components.

With its low RDS(ON) and low gate charge internal N-channel

MOSFET switch and P-channel MOSFET synchronous recti-

ﬁer, the LTC3528-2 achieves high efﬁciency over a wide

range of load current. The LTC3528-2 features continuous

2MHz PWM operation over a wide range of load current.

At very light loads, the LTC3528-2 will enter Burst Mode

operation to maintain high efﬁciency. Operation can be

best understood by referring to the Block Diagram.

LOW VOLTAGE START-UP

The LTC3528-2 includes an independent start-up oscillator

designed to operate at an input voltage of 0.70V (typical).

Soft-start and inrush current limiting are provided during

start-up, as well as normal operating mode.

When either VIN or VOUT exceeds 1.6V typical, the IC enters

normal operating mode. Once the output voltage exceeds

the input by 0.24V, the IC powers itself from VOUT instead of

VIN. At this point the internal circuitry has no dependency

on the VIN input voltage, eliminating the requirement for

a large input capacitor. The input voltage can drop as low

as 0.5V. The limiting factor for the application becomes

the availability of the power source to supply sufﬁcient

power to the output at the low voltages, and the maximum

duty cycle, which is clamped at 92% typical. Note that

at low input voltages, small voltage drops due to series

resistance become critical, and greatly limit the power

delivery capability of the converter.

LOW NOISE FIXED FREQUENCY OPERATION

Soft-Start

The LTC3528-2 contains internal circuitry to provide soft-

start operation. The internal soft-start circuitry slowly

ramps the peak inductor current from zero to its peak

value of 1.5A (typical), allowing start-up into heavy loads.

The soft-start time is approximately 0.5ms. The soft-start

circuitry is reset in the event of a commanded shutdown

or a thermal shutdown.

Oscillator

An internal oscillator sets the frequency of operation to

2MHz.

Shutdown

The converter is shut down by pulling the SHDN pin below

0.25V, and activated by pulling SHDN above 0.88V. Although

SHDN can be driven above VIN or VOUT (up to the absolute

maximum rating) without damage, the LTC3528-2 has a

proprietary test mode that may be engaged if SHDN is held

in the range of 0.5V to 1V higher than the greater of VIN or

VOUT. If the test mode is engaged, normal PWM switching

action is interrupted, which can cause undesirable opera-

tion in some applications. Therefore, in applications where

SHDN may be driven above VIN, a resistor divider or other

means must be employed to keep the SHDN voltage below

(VIN + 0.4V) to prevent the possibility of the test mode

being engaged. Please refer to Figure 1 for two possible

implementations

(Refer to Block Diagram)

±30% SHDN

LTC3528-2

VCNTRL

±30% SHDN

LTC3528-2

ZETEX ZC2811E

R > (VCNTRL/(VIN + 0.4) – 1) MΩ

VIN

3528 F01

Figure 1. Recommended Shutdown Circuits

when Driving SHDN Above VIN

LTC3528-2

35282f

Error Ampliﬁer

The error ampliﬁer is a transconductance type. The nonin-

verting input is internally connected to the 1.20V reference

and the inverting input is connected to FB. Clamps limit

the minimum and maximum error amp output voltage for

improved large-signal transient response. Power converter

control loop compensation is provided internally. A voltage

divider from VOUT to ground programs the output voltage

via FB from 1.6V to 5.25V.

VOUT =1.20V •1+R2











Current Sensing

Lossless current sensing converts the peak current signal

of the N-channel MOSFET switch into a voltage which

is summed with the internal slope compensation. The

summed signal is compared to the error ampliﬁer output

to provide a peak current control command for the PWM.

Current Limit

The current limit comparator shuts off the N-channel

MOSFET switch once its threshold is reached. The cur-

rent limit comparator delay to output is typically 60ns.

Peak switch current is limited to approximately 1.5A,

independent of input or output voltage, unless VOUT falls

below 0.7V, in which case the current limit is cut in half.

Zero Current Comparator

The zero current comparator monitors the inductor cur-

rent to the output and shuts off the synchronous rectiﬁer

when this current reduces to approximately 20mA. This

prevents the inductor current from reversing in polarity,

improving efﬁciency at light loads.

Synchronous Rectiﬁer

To control inrush current and to prevent the inductor

current from running away when VOUT is close to VIN, the

P-channel MOSFET synchronous rectiﬁer is only enabled

when VOUT > (VIN + 0.24V).

Anti-Ringing Control

The anti-ringing control connects a resistor across the

inductor to prevent high frequency ringing on the SW pin

during discontinuous current mode operation. The ringing

of the resonant circuit formed by L and CSW (capacitance

on SW pin) is low energy, but can cause EMI radiation.

Output Disconnect

The LTC3528-2 is designed to allow true output discon-

nect by eliminating body diode conduction of the internal

P-channel MOSFET rectiﬁer. This allows for VOUT to go to

zero volts during shutdown, drawing no current from the

input source. It also enables inrush current limiting at turn-

on, minimizing surge currents seen by the input supply.

Note that to obtain the advantages of output disconnect,

a Schottky diode cannot be connected between SW and

VOUT. The output disconnect feature also allows VOUT

to be forced above the programmed regulation voltage,

without any reverse current into the input power source.

Thermal Shutdown

If the die temperature exceeds 160°C, the LTC3528-2

enters thermal shutdown. All switches will be turned off

and the soft-start capacitor will be discharged. The device

will be enabled again when the die temperature drops by

approximately 15°C.

Burst Mode OPERATION

The LTC3528-2 will automatically enter Burst Mode op-

eration at light load current and return to ﬁxed frequency

PWM mode when the load increases. Refer to the Typical

Performance Characteristics to see the output load Burst

Mode threshold vs VIN. The load at which Burst Mode

operation is entered can be changed by adjusting the

inductor value. Raising the inductor value will lower the

load current at which Burst Mode operation is entered.

In Burst Mode operation, the LTC3528-2 continues switch-

ing at a ﬁxed frequency of 2MHz, using the same error

ampliﬁer and loop compensation for peak current mode

control. This control method minimizes output transients

OPERATION

(Refer to Block Diagram)

LTC3528-2

35282fa

OPERATION

(Refer to Block Diagram)

when switching between modes. In Burst Mode opera-

tion, energy is delivered to the output until it reaches the

nominal regulated value, then the LTC3528-2 transitions to

sleep mode where the outputs are off and the LTC3528–2

consumes only 12µA of quiescent current from VOUT. Once

the output voltage has drooped slightly, switching resumes

again. This maximizes efﬁciency at very light loads by

minimizing switching and quiescent current losses. Burst

Mode output ripple, which is typically 1% peak-to-peak,

can be reduced by using more output capacitance (10µF

or greater).

As the load current increases, the LTC3528-2 automatically

leaves Burst Mode operation. Note that larger output ca-

pacitor values may cause this transition to occur at lighter

loads. The regulator will also leave Burst Mode operation if

a load transient occurs which causes the inductor current

to repeatedly reach current limit. Once the LTC3528-2 has

left Burst Mode operation and returned to normal opera-

tion, it will remain there until the output load is reduced

below the Burst threshold.

Burst Mode operation is inhibited during start-up and

until soft-start is done and VOUT is at least 0.24V greater

than VIN.

Single Cell to 5V Step-Up Applications

Due to the high inductor current slew rate in applications

boosting to 5V from a single cell (alkaline, NiCd or NiMH),

the LTC3528-2 may not enter Burst Mode operation at in-

put voltages below 1.5V. For single cell to 5V applications

requiring Burst Mode operation, the 1MHz LTC3528 is

recommended. Refer to the Typical Performance Charac-

teristics for the Burst Mode thresholds for different input

and output voltages.

LTC3528-2

35282f

APPLICATIONS INFORMATION

VIN > VOUT OPERATION

The LTC3528-2 maintains voltage regulation even when

the input voltage is above the desired output voltage. Note

that the efﬁciency is much lower in this mode, and the

maximum output current capability will be less. Refer to

the Typical Performance Characteristics.

SHORT-CIRCUIT PROTECTION

The LTC3528-2 output disconnect feature allows an output

short circuit while maintaining a maximum internally set

current limit. To reduce power dissipation under short-

circuit conditions, the peak switch current limit is reduced

to 750mA (typical).

SCHOTTKY DIODE

Although not required, adding a Schottky diode from

SW to VOUT will improve efﬁciency by about 2%. Note

that this defeats the output disconnect and short-circuit

protection features.

PCB LAYOUT GUIDELINES

The high speed operation of the LTC3528-2 demands

careful attention to board layout. A careless layout will

not produce the advertised performance. Figure 2 shows

the recommended component placement. A large ground

copper area with the package backside metal pad properly

soldered will help to lower the chip temperature. A multi-

layer board with a separate ground plane is ideal, but not

absolutely necessary.

COMPONENT SELECTION

Inductor Selection

The LTC3528-2 can utilize small surface mount chip induc-

tors due to its fast 2MHz switching frequency. Inductor

values between 1.5µH and 3.3µH are suitable for most

applications. Larger values of inductance will allow slightly

greater output current capability by reducing the inductor

ripple current. Increasing the inductance above 10µH will

increase size while providing little improvement in output

current capability.

The minimum inductance value is given by:

L>VIN(MIN) •VOUT(MAX) – VIN(MIN)

( )

2•Ripple •VOUT(MAX)

µH

where:

Ripple = Allowable inductor current ripple (amps peak-

peak)

VIN(MIN) = Minimum input voltage

VOUT(MAX) = Maximum output voltage

The inductor current ripple is typically set for 20% to

40% of the maximum inductor current. High frequency

ferrite core inductor materials reduce frequency dependent

power losses compared to cheaper powdered iron types,

improving efﬁciency. The inductor should have low ESR

(series resistance of the windings) to reduce the I2R power

losses, and must be able to handle the peak inductor cur-

rent without saturating. Molded chokes and some chip

inductors usually do not have enough core area to support

the peak inductor currents of 1.5A seen on the LTC3528-2.

To minimize radiated noise, use a shielded inductor. See

Table 1 for suggested components and suppliers.

Figure 2. Recommended Component Placement

for Single Layer Board

SHDN

PGOOD

LTC3528-2

VOUT

35282 F02

COUT

VIN

VIN CIN

SGND

PGND

MULTIPLE VIAS

TO GROUND PLANE

LTC3528-2

35282fa

APPLICATIONS INFORMATION

Table 1. Recommended Inductors

VENDOR PART/STYLE

Coilcraft

(847) 639-6400

www.coilcraft.com

DO1606T, MSS5131, MSS5121

MSS6122, MOS6020

ME3220, DO1608C

1812PS

Coiltronics SD12, SD14, SD20

SD25, SD52

Sumida

(847) 956-0666

www.sumida.com

CD43

CDC5D23B

CDRH5D18

TDK VLP, VLF

VLCF, SLF, VLS

Toko

(408) 432-8282

www.tokoam.com

D53, D62, D63

D73, D75

Wurth

(201) 785-8800

www.we-online.com

WE-TPC type M, MH

Output and Input Capacitor Selection

Low ESR (equivalent series resistance) capacitors should

be used to minimize the output voltage ripple. Multilayer

ceramic capacitors are an excellent choice as they have

extremely low ESR and are available in small footprints.

A 10µF to 22µF output capacitor is sufﬁcient for most ap-

plications. Values larger than 22µF may be used to obtain

extremely low output voltage ripple and improve transient

response. X5R and X7R dielectric materials are preferred

for their ability to maintain capacitance over wide voltage

and temperature ranges. Y5V types should not be used.

The internal loop compensation of the LTC3528-2 is de-

signed to be stable with output capacitor values of 10µF

or greater. Although ceramic capacitors are recommended,

low ESR tantalum capacitors may be used as well.

A small ceramic capacitor in parallel with a larger tantalum

capacitor may be used in demanding applications which

have large load transients. Another method of improving the

transient response is to add a small feed-forward capaci-

tor across the top resistor of the feedback divider (from

VOUT to FB). A typical value of 68pF will generally sufﬁce.

Low ESR input capacitors reduce input switching noise

and reduce the peak current drawn from the battery. It

follows that ceramic capacitors are also a good choice

for input decoupling and should be located as close as

possible to the device. A 10µF input capacitor is sufﬁcient

for most applications. Larger values may be used without

limitations. Table 2 shows a list of several ceramic capaci-

tor manufacturers. Consult the manufacturers directly for

detailed information on their selection of ceramic parts.

Table 2. Capacitor Vendor Information

SUPPLIER PHONE WEBSITE

AVX (803) 448-9411 www.avxcorp.com

Murata (714) 852-2001 www.murata.com

Taiyo-Yuden (408) 573-4150 www.t-yuden.com

TDK (847) 803-6100 www.component.tdk.com

TYPICAL APPLICATIONS

1 Cell to 1.8V

VIN

499k

2.2µH

4.7µF

10µF

68pF

35282 TA02a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

0.88V TO 1.6V

VOUT

1.8V

250mA

OFF ON

GND

Efﬁciency

LOAD CURRENT (mA)

0.01

100

35282 TA02b

0.1 1 10 1000

EFFICIENCY (%)

VIN = 0.9V

VIN = 1.2V

VIN = 1.5V

LTC3528-2

35282f

Dual 1 Cell to 1.8V, 3V Sequenced Supply

VIN

499k

475k

2.2µH

4.7µF

10µF

LTC3528-2

SHDN

PGOOD

VOUT

VIN

0.88V TO 1.6V

VOUT1

1.8V

250mA

OFF ON

GND

VIN

499k

2.2µH

324k

4.7µF

10µF

68pF

3528 TA03a

LTC3528-2

SHDN

PGOOD

VOUT

VOUT2

200mA

GND

68pF

Output Voltage Sequencing

VOUT2

VOUT1

VIN

PGOOD1

200µs/DIV

0.5V/DIV

35282 TA03b

TYPICAL APPLICATIONS

1 Cell to 3.3V Efﬁciency

VIN

499k

2.2µH

287k

4.7µF

10µF

68pF

35282 TA04a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

0.88V TO 1.6V

VOUT

3.3V

200mA

OFF ON

GND

LOAD CURRENT (mA)

0.01

100

35282 TA04b

0.1 1 10 1000

EFFICIENCY (%)

VIN = 0.9V

VIN = 1.2V

VIN = 1.5V

LTC3528-2

35282fa

TYPICAL APPLICATIONS

2 Cell to 5V Efﬁciency

EfﬁciencyLi-Ion to 5V

VIN

2.2µH

316k

4.7µF

22µF

68pF

35282 TA06a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

1.8V TO 3.2V

VOUT

300mA

OFF ON

GND

VIN

2.2µH

316k

4.7µF 68pF

35282 TA07a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

2.7V TO 4.2V

VOUT

400mA

OFF ON

GND

LOAD CURRENT (mA)

0.01

100

35282 TA06b

0.1 1 10 1000

EFFICIENCY (%)

VIN = 1.8V

VIN = 2.4V

VIN = 3V

LOAD CURRENT (mA)

0.01

100

35282 TA07b

0.1 1 10 1000

EFFICIENCY (%)

VIN = 2.8V

VIN = 3.6V

VIN = 4.2V

Efﬁciency

2 Cell to 3.3V

VIN

499k

2.2µH

287k

4.7µF

10µF

68pF

35282 TA05a

LTC3528-2

SHDN

PGOOD

VOUT

VIN

1.8V TO 3.2V

VOUT

3.3V

400mA

OFF ON

GND

LOAD CURRENT (mA)

0.01

100

35282 TA05b

0.1 1 10 1000

EFFICIENCY (%)

VIN = 1.8V

VIN = 2.4V

VIN = 3V

LTC3528-2

35282f

2.00 ±0.10

(2 SIDES)

NOTE:

1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm 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

0.40 ± 0.10

BOTTOM VIEW—EXPOSED PAD

0.56 ± 0.05

(2 SIDES)

0.75 ±0.05

R = 0.115

TYP

R = 0.05

TYP

2.15 ±0.05

(2 SIDES)

3.00 ±0.10

(2 SIDES)

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

0.200 REF

0 – 0.05

(DDB8) DFN 0905 REV B

0.25 ± 0.05

0.50 BSC

PIN 1

R = 0.20 OR

0.25 × 45°

CHAMFER

0.25 ± 0.05

2.20 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

0.61 ±0.05

(2 SIDES)

1.15 ±0.05

0.70 ±0.05

2.55 ±0.05

PACKAGE

OUTLINE

0.50 BSC

PACKAGE DESCRIPTION

DDB Package

8-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1702 Rev B)

LTC3528-2

35282fa

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 representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 01/11 Change in Operating Temperature Range

Update to Note 2 reﬂected in Electrical Characteristics

Replaced graphs G14, G15, G16 and G17

Operations section update Pin 9 to read GND

Operations section update to Shutdown

2,3

LTC3528-2

35282f

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

 LINEAR TECHNOLOGY CORPORATION 2009

LT 0111 REV A • PRINTED IN USA

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LTC3528/LTC3528 1A (ISW), 1MHz Synchronous Step-Up DC/DC Converters

with Output Disconnect

94% Efﬁciency, VIN: 0.7V to 5.5V, VOUT(MAX) = 5.25V, IQ = 12µA,

ISD < 1µA, 3mm × 2mm DFN8 Package

LTC3528B-2 1A (ISW), 2MHz Synchronous Step-Up DC/DC Converter

with Output Disconnect

94% Efﬁciency, VIN: 0.7V to 5.5V, VOUT(MAX) = 5.25V, IQ = 12µA,

ISD < 1µA, 3mm × 2mm DFN8 Package

LTC3400/LTC3400B 600mA (ISW), 1.2MHz, Synchronous Step-Up

DC/DC Converters

92% Efﬁciency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA,

ISD < 1µA, ThinSOT

Package

LTC3421 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter

with Output Disconnect

94% Efﬁciency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA,

ISD < 1µA, 4mm × 4mm QFN24 Package

LTC3422 1.5A (ISW), 3MHz Synchronous Step-Up DC/DC

Converter with Output Disconnect

94% Efﬁciency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25µA,

ISD < 1µA, 3mm × 3mm DFN10 Package

LTC3426 2A (ISW), 1.5MHz, Step-Up DC/DC Converter 92% Efﬁciency VIN: 1.6V to 5.5V, VOUT(MAX) = 5V, IQ = 600µA,

ISD < 1µA, ThinSOT Package

LTC3427 500mA (ISW), 1.25MHz, Synchronous Step-Up DC/DC

Converter with Output Disconnect

94% Efﬁciency VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, IQ = 350µA

ISD < 1µA, 2mm × 2mm DFN6 Package

LTC3429/LTC3429B 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC

Converter with Output Disconnect and Soft-Start

96% Efﬁciency VIN: 0.85V to 4.3V, VOUT(MAX) = 5V, IQ = 20µA,

ISD < 1µA, ThinSOT Package

LTC3458/LTC3458L 1.4A/1.7A (ISW), 1.5MHz, Synchronous Step-Up DC/DC

Converter

94% Efﬁciency VIN: 0.85V to 6V, VOUT(MAX) = 7.5V/6V, IQ = 15µA,

ISD < 1µA, 3mm × 4mm DFN12 Package

LTC3459 80mA (ISW), Synchronous Step-Up DC/DC Converter 92% Efﬁciency VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10µA,

ISD < 1µA, ThinSOT Package

3494/LT3494A 180mA/350mA (ISW), High Efﬁciency Step-Up DC/DC

Converter with Output Disconnect

85% Efﬁciency VIN: 2.3V to 16V, VOUT(MAX) = 38V, IQ = 65µA,

ISD < 1µA, 2mm × 3mm DFN6, ThinSOT Packages

LTC3523/LTC3523-2 600mA (ISW), Step-Up and 400mA Synchronous

Step-Down 1.2MHz/2.4MHz DC/DC Converters with

Output Disconnect

94% Efﬁciency VIN: 1.8V to 5.5V, VOUT(MAX) = 5.25V, IQ = 45µA,

ISD < 1µA, 3mm × 3mm QFN16

LTC3526/LTC3526L

LTC3526B

500mA (ISW), 1MHz Synchronous Step-Up DC/DC

Converters with Output Disconnect

94% Efﬁciency, VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9µA,

ISD < 1µA, 2mm × 2mm DFN6 Package

LTC3527/LTC3527-1 Dual 800mA/400mA (ISW), 2.2MHz, Synchronous

Step-Up DC/DC Converter with Output Disconnect

94% Efﬁciency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 12µA,

ISD < 1µA, 3mm × 3mm QFN16 Package

LTC3537 600mA, 2.2MHz Synchronous Step-Up DC/DC Converter

with Output Disconnect and 100mA LDO

94% Efﬁciency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 30µA,

ISD < 1µA, 3mm × 3mm QFN16 Package

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN 
 
●     
●     
●     
●     
●     
●     
   
●     
●     
●     
●     
●     
Step-Up (Boost) Regulators
Home  >  Products  >  Power Management  >  Switching Regulator  >  Step-Up (Boost) Regulators  >  
Micropower Boost  >  LTC3528-2 
 
 
●     Micropower Boost 
●     Internal Power Switch Boost 
●     Multiple Output Boost 
●     External Power Switch Boost 
LTC3528-2 - 1A, 2MHz Synchronous Step-
Up DC/DC Converter in 2mm × 3mm DFN
●     
●     
●     
●     
●     
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (1 of 6) [24-Jan-2011 8:20:55 AM]
Search

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN

● Print Friendly

Features

● Delivers 3.3V at 200mA from a Single Alkaline/ NiMH Cell or 3.3V at 400mA from Two Cells

● VIN Start-Up Voltage: 700mV

● 0.50V to 5.5V Input Range

● 1.6V to 5.25V VOUT Range

● Up to 94% Efficiency

● Output Disconnect

● 2MHz Fixed Frequency Operation

● VIN > VOUT Operation

● Integrated Soft-Start

● Current Mode Control with Internal Compensation

● Burst Mode® Operation with 12•A Quiescent Current

● Internal Synchronous Rectifier

● Logic Controlled Shutdown: <1•A

● Anti-Ringing Control

● Low Profile (2mm × 3mm × 0.75mm) DFN Package

Typical Application

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (2 of 6) [24-Jan-2011 8:20:55 AM]

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN

Description

The LTC3528-2 is a synchronous, fixed frequency step-up DC/DC converter with output disconnect. High

efficiency synchronous rectification, in addition to a 700mV startup 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 footprint by allowing the use of tiny, low profile

inductors and ceramic capacitors. The current mode PWM is internally compensated, simplifying the

design process. The LTC3528-2 enters Burst Mode operation 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, shortcircuit protection and thermal overload protection.

The LTC3528-2 is offered in an 8-lead 2mm × 3mm × 0.75mm DFN package.

Packaging

DFN-8

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (3 of 6) [24-Jan-2011 8:20:55 AM]

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN 
 
Back to Top 
Order Info
●     Part numbers ending in PBF are lead free. Please contact LTC marketing for information on lead 
based finish parts.
●     Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, 
respectively
●     Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
Part Number Package Pins Temp Price (1-99) Price (1k)*RoHS Data
LTC3528BEDDB#PBF DFN 8 E $2.79   View
LTC3528BEDDB#TRMPBF DFN 8 E $2.79 $2.00 View
LTC3528BEDDB#TRPBF DFN 8 E $2.79 $1.95 View
LTC3528BEDDB-2#PBF DFN 8 E $2.79   View
LTC3528BEDDB-2#TRMPBF DFN 8 E $2.79 $2.00 View
LTC3528BEDDB-2#TRPBF DFN 8 E $2.79 $1.95 View
LTC3528EDDB#PBF DFN 8 E $2.79   View
LTC3528EDDB#TRMPBF DFN 8 E $2.79 $2.00 View
LTC3528EDDB#TRPBF DFN 8 E $2.79 $1.95 View
LTC3528EDDB-2#PBF DFN 8 E $2.79   View
LTC3528EDDB-2#TRMPBF DFN 8 E $2.79 $2.00 View
LTC3528EDDB-2#TRPBF DFN 8 E $2.79 $1.95 View
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (4 of 6) [24-Jan-2011 8:20:55 AM]

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN

Buy Now

Request Samples

* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB

USA per unit for the stated volume), and is subject to change. International prices may differ due to local

duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your

local Linear Technology sales office or authorized distributor.

Applications

● Medical Instruments

● Noise Canceling Headphones

● Wireless Mice

● Bluetooth Headsets

Simulate

To simulate selected Linear Technology products, please download LTSpice / SwitcherCAD III. This

powerful schematic capture and simulation tool includes macro models for 80% of Linear Technology's

switching regulators, over 200 op amp models, as well as resistors, transistors and MOSFET models.

For other simulation tools, visit our Design Simulation and Device Models page.

Order Now

Request Samples

Documentation

Datasheet

● LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (5 of 6) [24-Jan-2011 8:20:55 AM]

Linear Technology - LTC3528-2 - 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN

● Site Help

● Site Map

● Site Index

● Send Us Feedback

●

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1031,C1060,P88383 (6 of 6) [24-Jan-2011 8:20:55 AM]