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LTC3528B-2

3528b2fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

1A, 2MHz Synchronous

Step-Up DC/DC Converter

in 2mm × 3mm DFN

The LTC

3528B-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 LTC3528B-2 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 LTC3528B-2 is offered in an 8-lead 2mm × 3mm ×

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

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

OUT

Operation

Integrated Soft-Start

Current Mode Control with Internal Compensation

Low Noise PWM Operation

Internal Synchronous Rectiﬁer

Logic Controlled Shutdown: <1µA

Anti-Ringing Control

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

Medical Instruments

Flash-Based MP3 Players

Noise Canceling Headphones

Wireless Mice

Bluetooth Headsets

Efﬁciency and Power Loss

499k

2.2µH

287k

4.7µF

10µF

68pF

35282 TA01a

LTC3528B-2

SHDN

PGOOD

OUT

1.8V TO 3.2V

OUT

3.3V

400mA

OFF ON

GND

LOAD CURRENT (mA)

0.1

100

35282 TA01b

1 10 100 1000

100

1000

EFFICIENCY (%)

POWER LOSS (mW)

EFFICIENCY

POWER LOSS

OUT

= 3.3V

= 2.4V

L, LT, LTC, LTM, 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
LTC3528B-2 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN FEATURES n n n n n n n n n n n n n n n 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 0.50V to 5.5V Input Range 1.6V to 5.
PAGE 2
LTC3528B-2 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.......................................................... –0.
PAGE 3
LTC3528B-2 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. 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
LTC3528B-2 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current and VIN for VOUT = 1.8V Efficiency vs Load Current and VIN for VOUT = 3V 100 50 10 POWER LOSS 40 30 70 EFFICIENCY (%) 60 50 30 20 VIN = 1V VIN = 1.2V VIN = 1.5V 10 1 0 0.1 1 1 1000 100 10 LOAD CURRENT (mA) 35282 G01 35282 G26 Efficiency vs Load Current and VIN for VOUT = 3.3V Efficiency vs Load Current and VIN for VOUT = 5V 90 EFFICIENCY 80 60 50 POWER LOSS 40 30 1 60 100 50 POWER LOSS 40 10 VIN = 2.
PAGE 5
LTC3528B-2 TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency Change vs VOUT 0 –0.25 450 2 400 1 FREQUENCY CHANGE (%) 0.25 350 –0.50 RDS(ON) (mΩ) FREQUENCY CHANGE (%) Oscillator Frequency Change vs Temperature RDS(ON) vs VOUT 0.50 –0.75 –1.00 –1.25 300 PMOS 250 200 –1.50 –1.75 NMOS 150 –2.00 –2.25 (TA = 25°C unless otherwise noted) 1.5 2 2.5 3.5 3 VOUT (V) 4 4.5 100 1.5 5 2 2.5 3.5 3 VOUT (V) 4.
PAGE 6
LTC3528B-2 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) Load Step Response (3.6V to 5V) Load Step Response (1.2V to 3.3V) VOUT 100mV/DIV VOUT 100mV/DIV LOAD CURRENT 200mA/DIV LOAD CURRENT 100mA/DIV VIN = 3.6V 20µs/DIV VOUT = 5V COUT = 10µF L = 2.2µH LOAD CURRENT = 100mA TO 550mA 35282 G22 20µs/DIV VIN = 1.2V VOUT = 3.3V COUT = 10µF L = 2.2µH LOAD CURRENT = 20mA TO 170mA 35282 G24 PIN FUNCTIONS SHDN (Pin 1): Logic Controlled Shutdown Input.
PAGE 7
LTC3528B-2 BLOCK DIAGRAM L1 2.2µH CIN 4.7µF 8 5 VIN SW ANTI-RING VOUT VSEL VBEST 1 SHDN SHUTDOWN SHUTDOWN WELL SWITCH VB VOUT GATE DRIVERS AND ANTI-CROSS CONDUCTION – + 4M Σ VREF VREF UVLO PK COMP PK UVLO IZERO 3 CLK R1 + – VREF FB CLAMP VREF – 10% SOFT-START FB THERMAL SHUTDOWN COUT 10µF ERROR AMP LOGIC PGOOD + – IZERO COMP R2 2 SLOPE COMP START-UP 2MHz OSC FB VOUT 1.6V TO 5.25V 4 + – VIN 0.
PAGE 8
LTC3528B-2 OPERATION (Refer to Block Diagram) The LTC3528B-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 current mode architecture with adaptive slope compensation provides excellent transient load response and requires minimal output filtering.
PAGE 9
LTC3528B-2 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 1.6V to 5.
PAGE 10
LTC3528B-2 APPLICATIONS INFORMATION VIN > VOUT OPERATION soldered will help to lower the chip temperature. A multilayer board with a separate ground plane is ideal, but not absolutely necessary. The LTC3528B-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.
PAGE 11
LTC3528B-2 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 12
LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 1.8V Efficiency 100 90 2.2µH 80 SW VIN 4.7µF 68pF 499k LTC3528B-2 PGOOD OFF ON VOUT 1.8V 250mA VOUT EFFICIENCY (%) VIN 0.88V TO 1.6V 10µF FB SHDN 1M GND 70 60 50 40 30 VIN = 0.9V VIN = 1.2V VIN = 1.5V 20 35282 TA02a 10 0.1 1 10 100 LOAD CURRENT (mA) 1000 35282 TA02b Dual 1 Cell to 1.8V, 3V Sequenced Supply 2.2µH SW VIN 0.88V TO 1.6V VOUT VIN 4.7µF 475k LTC3528B-2 68pF SHDN VOUT2 1M GND VOUT1 VIN PGOOD1 0.5V/DIV 2.2µH SW VIN 4.
PAGE 13
LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 3.3V Efficiency 90 2.2µH 80 VIN 4.7µF VOUT LTC3528B-2 68pF 10µF FB PGOOD OFF ON 499k SHDN VOUT 3.3V 200mA 70 EFFICIENCY (%) SW VIN 0.88V TO 1.6V 287k GND 60 50 40 30 VIN = 0.9V VIN = 1.2V VIN = 1.5V 20 35282 TA04a 10 1 10 100 LOAD CURRENT (mA) 1000 36282 TA04b 2 Cell to 3.3V Efficiency 100 2.2µH 90 VIN 4.7µF VOUT LTC3528B-2 PGOOD OFF ON SHDN GND 499k 68pF VOUT 3.3V 400mA 10µF FB 287k 80 EFFICIENCY (%) SW VIN 1.8V TO 3.
PAGE 14
LTC3528B-2 TYPICAL APPLICATIONS 2 Cell to 5V 2.2µH SW VIN 1.8V TO 3.2V VIN 4.7µF VOUT LTC3528B-2 PGOOD OFF ON 1M 22µF FB SHDN VOUT 5V 300mA 316k GND 35282 TA06a Efficiency 100 90 EFFICIENCY (%) 80 70 60 50 40 30 VIN = 1.8V VIN = 2.4V VIN = 3V 20 10 0.
PAGE 15
LTC3528B-2 TYPICAL APPLICATIONS Li-Ion to 5V 2.2µH SW VIN 2.7V TO 4.2V VIN 4.7µF LTC3528B-2 PGOOD OFF ON VOUT 5V 400mA VOUT 1M 22µF FB SHDN 316k GND 35282 TA07a Efficiency 100 90 EFFICIENCY (%) 80 70 60 50 40 30 VIN = 2.8V VIN = 3.6V VIN = 4.2V 20 10 0.
PAGE 16
LTC3528B-2 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
LTC3528B-2 REVISION HISTORY REV DATE DESCRIPTION A 01/11 Change to Operating Temperature Range PAGE NUMBER Update to Note 2 reflected in Electrical Characteristics 2 2, 3 Replaced graphs G14, G15, G16 and G17 5 Operations section update Pin 9 to read GND 6 Operations section update to Shutdown 8 3528b2fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 18
LTC3528B-2 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 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.