Datasheet

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LTC3426

3426fa

1.2MHz Step-Up DC/DC

Converter in SOT-23

■

Internal 2A MOSFET Switch

■

1.2MHz Switching Frequency

■

Integrated Soft-Start

■

Low 1.6V V

Operation

■

Low R

DS(ON)

Switch: 100mΩ at 5V Output

■

Delivers 5V at 800mA from a 3.3V Input

■

Delivers 3.3V at 800mA from a 2.5V Input

■

Uses Small, Low Profile External Components

■

Low Profile (1mm) SOT-23 (ThinSOT

) Package

■

White LED Driver Supply

■

Local 3.3V or 5V Supply

■

Battery Back-Up

The LTC

3426 step-up switching regulator generates an

output voltage of up to 5.5V from an input voltage as low

as 1.6V. Ideal for applications where space is limited, it

switches at 1.2MHz, allowing the use of tiny, low cost and

low profile external components. Its internal 2A, 100mΩ

NMOS switch provides high efficiency even at heavy load,

while the constant frequency, current mode architecture

results in low, predictable output noise that is easy to filter.

Antiringing circuitry reduces EMI concerns by damping

the inductor while in discontinuous mode, and internal

soft-start eases inrush current worries. Internal frequency

compensation is designed to accommodate ceramic out-

put capacitors, further reducing noise. The device features

very low shutdown current of 0.5µA.

The LTC3426 is available in the 6-lead SOT-23 package.

3.3V to 5V Boost Converter Efficiency

2.2µH

3.3V

LTC3426

SHDN

22µF

10µF

OUT

800mA

3426 TA01

OUT

FBOFF ON

GND

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

LOAD CURRENT (mA)

EFFICIENCY (%)

10 100 1000

3426 TA01b

100

= 3.3V

OUT

= 5V

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents, including 6498466, 6611131

Summary of content (12 pages)

PAGE 1
LTC3426 1.2MHz Step-Up DC/DC Converter in SOT-23 U FEATURES DESCRIPTIO ■ The LTC®3426 step-up switching regulator generates an output voltage of up to 5.5V from an input voltage as low as 1.6V. Ideal for applications where space is limited, it switches at 1.2MHz, allowing the use of tiny, low cost and low profile external components.
PAGE 2
LTC3426 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) VIN Voltage ................................................. –0.3V to 6V SW Voltage .................................................. –0.3V to 6V SHDN, FB Voltage ....................................... –0.3V to 6V VOUT ........................................................... –0.3V to 6V Operating Temperature Range (Note 2) .. – 40°C to 85°C Storage Temperature Range .................
PAGE 3
LTC3426 U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency vs Temperature Efficiency vs VIN EFFICIENCY (%) 1.3 1.2 FIGURE 1 CIRCUIT 98 TA = 25°C = 150mA I 96 VLOAD = 5V OUT 94 COUT = 22µF L = 2.2µH 92 FIGURE 1 CIRCUIT TA = 25°C VOUT = 5V 1.1 C OUT = 22µF L = 2.2µH IOUT(MAX) (A) 1.40 FREQUENCY (MHz) IOUT(MAX) vs VIN 1.3 100 90 88 0.9 0.7 86 1.1 84 0.5 82 1.0 –50 80 –30 –10 10 30 50 TEMPERATURE (°C) 70 1.8 90 2.2 2.6 3 VIN (V) 3.4 3.8 4.2 1.8 2.6 3 VIN (V) 3.
PAGE 4
LTC3426 U U U PI FU CTIO S SW (Pin 1): Switch Pin. Connect inductor between SW and VIN. A Schottky diode is connected between SW and VOUT. Keep these PCB trace lengths as short and wide as possible to reduce EMI and voltage overshoot. If the inductor current falls to zero, an internal 100Ω antiringing switch is connected from SW to VIN to minimize EMI. SHDN (Pin 4): Logic Controlled Shutdown Input. Typically, SHDN should be connected to VIN through a 1M pull-up resistor.
PAGE 5
LTC3426 U OPERATIO The LTC3426 is a monolithic 1.2MHz boost converter housed in a 6-lead SOT-23 package. The device features fixed frequency, current mode PWM control for excellent line and load regulation. The low RDS(ON) NMOS switch enables the device to maintain high efficiency over a wide range of load current. Operation of the feedback loop which sets the peak inductor current to keep the output in regulation can be best understood by referring to the Block Diagram in Figure 1.
PAGE 6
LTC3426 U W U U APPLICATIO S I FOR ATIO possible to the device. A 10µF input capacitor is sufficient for most applications. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information in their entire selection of ceramic parts. Table 2. Ceramic Capacitor Manufacturers Taiyo Yuden PCB Layout Guidelines The high speed operation of the LTC3426 demands careful attention to board layout. You will not get advertised performance with careless layout.
PAGE 7
LTC3426 U TYPICAL APPLICATIO S Efficiency L1 2.2µH 100 D1 95 VIN 3.3V VOUT VIN C1 10µF OFF ON R1 95.3k 1% LTC3426 SHDN FB VOUT 5V 800mA C2 22µF R2 30.9k 1% GND EFFICIENCY (%) 90 SW 85 80 75 70 65 60 55 C1: TAIYO YUDEN X5R JMK212BJ475ML C2: TAIYO YUDEN X5R JMK316BJ226ML D1: ON SEMICONDUCTOR MBRA210LT3 L1: COILCRAFT D03316P-222 3426 TA02a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA02b Efficiency L1 1.5µH 100 D1 VIN 1.8V VOUT VIN C1 10µF OFF ON LTC3426 SHDN GND FB R1 64.
PAGE 8
LTC3426 U TYPICAL APPLICATIO S Efficiency 100 L1 2.2µH VIN 3V TO 4.2V D1 95 VOUT VIN C1 10µF OFF ON R1 95.3k 1% LTC3426 SHDN FB R2 30.9k 1% GND C1: TDK C1608X5R0J475M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBR120VLSFT1 L1: SUMIDA CDRH4D28-2R2 2 VOUT 5V 750mA AT 3V C2 22µF EFFICIENCY (%) 90 SW VIN = 4.2V 85 80 VIN = 3V 75 70 65 60 55 3426 TA04a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA04b Efficiency 100 L1 2.5µH VIN 2.
PAGE 9
LTC3426 U TYPICAL APPLICATIO S Efficiency 100 L1 1.5µH D1 VIN 1.8V VOUT VIN C1 10µF OFF ON R1 75k 1% LTC3426 SHDN FB R2 44.2k 1% GND C1: TDK C1608X5R0J106M C2: TAIYO YUDEN JMK316BJ226ML D1: ON SEMICONDUCTOR MBRM120LT3 L1: TDK RLF7030T-1R5N6R1 VOUT 3.3V 540mA C2 22µF EFFICIENCY (%) 90 SW 80 70 60 3426 TA06a 50 1 10 100 LOAD CURRENT (mA) 1000 3426 TA06b Efficiency 90 L1 2.2µH VIN 1.8V D1 SW VOUT VIN C1 10µF OFF ON LTC3426 SHDN GND FB R1 95.3k 1% R2 30.
PAGE 10
LTC3426 U TYPICAL APPLICATIO S Efficiency L1 2.5µH VIN 2.5V 100 D1 VIN C1 10µF OFF ON VOUT LTC3426 SHDN GND FB R1 95.3k 1% R2 30.
PAGE 11
LTC3426 U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636 Rev B) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 REV B NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 12
LTC3426 RELATED PARTS PART NUMBER LT1613 LT1946/LT1946A LTC3400/LTC3400B LTC3401/LTC3402 LTC3421 LTC3425 LTC3429 LTC3436 LTC3459 LTC3464 DESCRIPTION 550mA (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converter 600mA (ISW), 1.