Datasheet

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LTC3528/LTC3528B

3528fd

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

1A, 1MHz Synchronous

Step-Up DC/DC Converters

in 3mm × 2mm DFN

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.

■

Delivers 3.3V at 200mA from a Single Alkaline/

NiMH Cell or 3.3V at 400mA from Two Cells

■

Start-Up Voltage: 700mV

■

1.6V to 5.25V V

OUT

Range

■

Up to 94% Efﬁciency

■

Output Disconnect

■

1MHz Fixed Frequency Operation

■

> 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

■

Medical Instruments

■

Flash-Based MP3 Players

■

Noise Canceling Headphones

■

Wireless Mice

■

Bluetooth Headsets

499k

4.7µH

287k

4.7µF

10µF

33pF

3528 TA01a

LTC3528

SHDN

PGOOD

OUT

1.8V TO 3.2V

OUT

3.3V

400mA

OFF ON

GND

LOAD CURRENT (mA)

0.01

100

3528 TA01b

0.1 1 10 1000

100

1000

0.1

0.01

EFFICIENCY (%)

POWER LOSS (mW)

EFFICIENCY

POWER LOSS

OUT

= 3.3V

= 2.4V

Efﬁciency and Power Loss

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.

Summary of content (18 pages)

PAGE 1
LTC3528/LTC3528B 1A, 1MHz Synchronous Step-Up DC/DC Converters in 3mm × 2mm DFN FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION Delivers 3.3V at 200mA from a Single Alkaline/ NiMH Cell or 3.3V at 400mA from Two Cells VIN Start-Up Voltage: 700mV 1.6V to 5.
PAGE 2
LTC3528/LTC3528B ABSOLUTE MAXIMUM RATINGS (Note 1) PIN CONFIGURATION 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........................................................
PAGE 3
LTC3528/LTC3528B ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the specified operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 1.2V, VOUT = 3.3V, unless otherwise noted. PARAMETER CONDITIONS MIN SHDN Input High Voltage TYP MAX 0.88 UNITS V SHDN Input Low Voltage 0.25 V 0.3 1 µA –10 –13 % SHDN Input Current VSHDN = 1.
PAGE 4
LTC3528/LTC3528B TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current and VIN for VOUT = 5V (LTC3528) 1000 100 90 50 1 VIN = 1.2V VIN = 1.8V VIN = 2.4V VIN = 3V 40 30 0.01 0.1 1 10 0.1 0.01 1000 100 80 EFFICIENCY (%) EFFICIENCY (%) POWER LOSS 60 110 100 70 10 POWER LOSS 60 50 VIN = 1.2V VIN = 2.4V VIN = 3.6V VIN = 4.2V 40 30 0.01 0.
PAGE 5
LTC3528/LTC3528B TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency Change vs VOUT Burst Mode Threshold Current vs VIN 60 (TA = 25°C unless otherwise noted) 0.50 VOUT = 5V RDS(ON) vs VOUT 450 NORMALIZED TO VOUT = 3V 0.25 400 IOUT (mA) 40 EXIT BURST ENTER BURST 20 –0.25 350 –0.50 RDS(ON) (mΩ) FREQUENCY CHANGE (%) 0 –0.75 –1.00 –1.25 2 4 3 –2.25 1.5 2.5 2 VIN (V) 3.5 3 VOUT (V) 4 4.5 Oscillator Frequency Change vs Temperature 2 2.5 3.5 3 VOUT (V) 4 40 1 30 0 20 4.
PAGE 6
LTC3528/LTC3528B TYPICAL PERFORMANCE CHARACTERISTICS Burst Mode Waveforms (TA = 25°C unless otherwise noted) Load Step Response (Fixed Frequency, 3.6V to 5V) VOUT and IIN During Soft-Start VOUT 1V/DIV VOUT 20mV/DIV VOUT 100mV/DIV IIN 200mA/DIV SHDN PIN INDUCTOR CURRENT 100mA/DIV VIN = 3.6V VOUT = 5V COUT = 22µF CFF = 33pF ILOAD = 30mA 5µs/DIV VIN = 1.2V VOUT = 3.3V COUT = 10µF L = 4.7µH 3528 G20 LOAD CURRENT 200mA/DIV VIN = 3.6V VOUT = 5V COUT = 10µF L = 4.
PAGE 7
LTC3528/LTC3528B PIN FUNCTIONS SGND (Pin 7): Signal Ground. Provide a short direct PCB path between SGND and the (–) side of the input and output capacitors. 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. VIN (Pin 8): Battery Input Voltage. Connect a minimum of 1µF ceramic decoupling capacitor from this pin to ground. BLOCK DIAGRAM L1 4.7µH CIN 4.
PAGE 8
LTC3528/LTC3528B OPERATION (Refer to Block Diagram) The LTC3528/LTC3528B are 1MHz synchronous boost converters housed in an 8-lead 3mm × 2mm DFN package. With the ability to start-up and operate from inputs less than 0.88V, the devices feature fixed frequency, current mode PWM control for exceptional line and load regulation. The current mode architecture with adaptive slope compensation provides excellent transient load response and requires minimal output filtering.
PAGE 9
LTC3528/LTC3528B OPERATION (Refer to Block Diagram) Error Amplifier Synchronous Rectifier The error amplifier is a transconductance type. The noninverting 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.
PAGE 10
LTC3528/LTC3528B OPERATION (Refer to Block Diagram) Burst Mode OPERATION The LTC3528 will automatically enter Burst Mode operation 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.
PAGE 11
LTC3528/LTC3528B APPLICATIONS INFORMATION VIN > VOUT OPERATION The LTC3528/LTC3528B will maintain 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/LTC3528B output disconnect feature allows an output short circuit while maintaining a maximum internally set current limit.
PAGE 12
LTC3528/LTC3528B APPLICATIONS INFORMATION 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 current without saturating.
PAGE 13
LTC3528/LTC3528B TYPICAL APPLICATIONS 1 Cell to 1.8V Efficiency 100 4.7µH 90 SW VIN 4.7µF VOUT PGOOD OFF ON 33pF 499k LTC3528 80 VOUT 1.8V 250mA EFFICIENCY (%) VIN 0.88V TO 1.6V 10µF FB SHDN 60 50 1M GND 70 VIN = 0.9V VIN = 1.2V VIN = 1.5V 40 3528 TA02a 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 3528 TA02b Dual 1 Cell to 1.8V, 3V Sequenced Supply 4.7µH SW VIN 0.88V TO 1.6V VOUT VIN 4.7µF 475k 33pF SHDN VOUT2 1M GND VOUT1 VIN PGOOD1 0.5V/DIV 4.7µH SW VIN 4.
PAGE 14
LTC3528/LTC3528B TYPICAL APPLICATIONS 1 Cell to 3.3V Efficiency 100 4.7µH 90 VIN 4.7µF VOUT 33pF 10µF FB PGOOD OFF ON 499k LTC3528 SHDN VOUT 3.3V 200mA 80 EFFICIENCY (%) SW VIN 0.88V TO 1.6V 287k GND 70 60 50 VIN = 0.9V VIN = 1.2V VIN = 1.5V 40 3528 TA04a 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 3528 TA04b 2 Cell to 3.3V Efficiency 100 4.7µH 90 VIN 1.8V TO 3.2V VIN 4.7µF VOUT PGOOD OFF ON 499k LTC3528 SHDN GND 33pF VOUT 3.
PAGE 15
LTC3528/LTC3528B TYPICAL APPLICATIONS 2 Cell to 5V Efficiency 100 4.7µH 90 VIN 4.7µF VOUT LTC3528 68pF 22µF FB PGOOD OFF ON 1M SHDN VOUT 5V 300mA 80 EFFICIENCY (%) SW VIN 1.8V TO 3.2V 60 50 316k GND 70 VIN = 1.8V VIN = 2.4V VIN = 3V 40 3528 TA06a 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 3528 TA06b Li-Ion to 5V Efficiency 100 4.7µH 90 VOUT VIN 4.7µF LTC3528 PGOOD OFF ON SHDN GND 1M 68pF VOUT 5V 400mA 22µF FB 80 EFFICIENCY (%) SW VIN 2.7V TO 4.
PAGE 16
LTC3528/LTC3528B PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ±0.05 (2 SIDES) 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.20 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.56 ± 0.05 (2 SIDES) 0.200 REF 0.75 ±0.05 0 – 0.05 4 0.25 ± 0.05 1 PIN 1 R = 0.20 OR 0.
PAGE 17
LTC3528/LTC3528B REVISION HISTORY (Revision history begins at Rev D) REV DATE DESCRIPTION D 01/11 Change to Operating Temperature Range PAGE NUMBER 2 Revised Note 2 2 Replaced graphs G14, G15, G16, G17 4 Operations Shutdown section revised text; added Figure 1 8 3528fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 18
LTC3528/LTC3528B RELATED PARTS PART NUMBER DESCRIPTION COMMENTS 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, ThinSOTTM Package LTC3401 1A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38µA, ISD < 1µA, 10-Lead MS Package LTC3402 2A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency VIN: 0.