Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Holder TSOT 23 6

LTC3405A-1.5/LTC3405A-1.8

3405a1518fa

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High Efficiency: Up to 93%

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Very Low Quiescent Current: Only 20

During Operation

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300mA Output Current at V

= 3V

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2.5V to 5.5V Input Voltage Range

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1.5MHz Constant Frequency Operation

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No Schottky Diode Required

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Low Dropout Operation: 100% Duty Cycle

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Stable with Ceramic Capacitors

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Shutdown Mode Draws <1µA Supply Current

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±3% Output Voltage Accuracy

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Current Mode Operation for Excellent Line and

Load Transient Response

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Overtemperature Protected

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Low Profile (1mm) ThinSOT

Package

The LTC

3405A-1.5/LTC3405A-1.8 are high efficiency

monolithic synchronous buck regulators using a constant

frequency, current mode architecture. Supply current

during operation is only 20µA and drops to <1µA in

shutdown. The 2.5V to 5.5V input voltage range makes the

LTC3405A-1.5/LTC3405A-1.8 ideally suited for single

Li-Ion battery-powered applications. 100% duty cycle

provides low dropout operation, extending battery life in

portable systems.

Switching frequency is internally set at 1.5MHz, allowing

the use of small surface mount inductors and capacitors.

The LTC3405A-1.5/LTC3405A-1.8 are specifically designed

to work well with ceramic output capacitors, achieving

very low output voltage ripple and a small PCB footprint.

The internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. The

LTC3405A-1.5/LTC3405A-1.8 are available in a low profile

(1mm) ThinSOT package.

For adjustable output voltage, refer to the LTC3405A data

sheet.

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Cellular Telephones

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Personal Information Appliances

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Wireless and DSL Modems

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Digital Still Cameras

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MP3 Players

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Portable Instruments

Figure 1a. High Efficiency Step-Down Converter

1.5V, 1.8V, 1.5MHz, 300mA

Synchronous Step-Down

Regulators in ThinSOT

Figure 1b. Efficiency vs Load Current

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

ThinSOT is a trademark of Linear Technology Corporation.

Protected by U.S. Patents, including 6580258, 5481178.

4.7µF

CER

2.7V

TO 5.5V

LTC3405A-1.8

RUN

MODE

4.7µH*

3405A1518 F01

MURATA LQH3C4R7M34

TAIYO YUDEN JMK212BJ475MG

OUT

GND

OUT

4.7µF

CER

OUT

1.8V

300mA

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

OUTPUT CURRENT (mA)

0.1

EFFICIENCY (%)

1000

100

3405A1518 F01b

1 100

= 2.7V

= 5.5V

= 4.2V

= 3.6V

Summary of content (16 pages)

PAGE 1
LTC3405A-1.5/LTC3405A-1.8 1.5V, 1.8V, 1.5MHz, 300mA Synchronous Step-Down Regulators in ThinSOT U FEATURES DESCRIPTIO ■ The LTC ®3405A-1.5/LTC3405A-1.8 are high efficiency monolithic synchronous buck regulators using a constant frequency, current mode architecture. Supply current during operation is only 20µA and drops to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3405A-1.5/LTC3405A-1.8 ideally suited for single Li-Ion battery-powered applications.
PAGE 2
LTC3405A-1.5/LTC3405A-1.8 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage .................................. – 0.3V to 6V MODE, RUN, VOUT Voltages....................... – 0.3V to VIN SW Voltage .................................. – 0.3V to (VIN + 0.3V) P-Channel Switch Source Current (DC) ............. 400mA N-Channel Switch Sink Current (DC) ................. 400mA Peak SW Sink and Source Current ....................
PAGE 3
LTC3405A-1.5/LTC3405A-1.8 U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure1a) Efficiency vs Input Voltage IOUT = 100mA 80 IOUT = 10mA IOUT = 1mA 80 VIN = 4.2V 70 75 70 65 60 VIN = 3.6V 50 VIN = 4.2V 40 30 IOUT = 0.1mA 60 PULSE SKIPPING MODE Burst Mode OPERATION 20 Burst Mode OPERATION VOUT = 1.8V 55 50 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 90 10 5.0 EFFICIENCY (%) IOUT = 250mA VIN = 2.7V 90 V = 3.6V IN EFFICIENCY (%) 85 EFFICIENCY (%) 100 100 90 5.5 VOUT = 1.
PAGE 4
LTC3405A-1.5/LTC3405A-1.8 U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1a) Dynamic Supply Current vs Supply Voltage VOUT = 1.8V ILOAD = 0A 1400 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 1600 1200 1000 800 600 400 PULSE SKIPPING MODE 0 3 3.5 4 4.5 SUPPLY VOLTAGE (V) 5.5 5 VIN = 5.5V 140 RUN = 0V PULSE SKIPPING MODE 220 180 140 100 BURST MODE OPERATION 20 0 50 –50 –25 25 75 0 TEMPERATURE (°C) BURST MODE OPERATION 2.5 VIN = 3.6V 300 VOUT = 1.
PAGE 5
LTC3405A-1.5/LTC3405A-1.8 U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1a) Load Step Load Step Load Step VOUT 100mV/DIV AC COUPLED VOUT 100mV/DIV AC COUPLED IL 200mA/DIV IL 200mA/DIV IL 200mA/DIV ILOAD 200mA/DIV ILOAD 200mA/DIV ILOAD 200mA/DIV VIN = 3.6V 40µs/DIV VOUT = 1.8V ILOAD = 20mA TO 250mA PULSE SKIPPING MODE 3405A1518 G20 VOUT 100mV/DIV AC COUPLED VIN = 3.6V 40µs/DIV VOUT = 1.8V ILOAD = 20mA TO 250mA Burst Mode OPERATION 3405A1518 G21 VIN = 3.6V 40µs/DIV VOUT = 1.
PAGE 6
LTC3405A-1.5/LTC3405A-1.8 W FU CTIO AL DIAGRA U U MODE 6 SLOPE COMP 0.65V OSC OSC 4 VIN FREQ SHIFT VOUT – 5 + LTC3405A-1.5 R1 = 110k R2 = 440k R1 LTC3405A-1.8 R1 = 180k R2 = 360k R2 – + 1.2V 0.4V – EA SLEEP S Q R Q RS LATCH RUN – OVDET 1.294V ICOMP SWITCHING LOGIC AND BLANKING CIRCUIT ANTISHOOTTHRU 3 SW OV + + 1.
PAGE 7
LTC3405A-1.5/LTC3405A-1.8 U OPERATIO (Refer to Functional Diagram) 600 VOUT = 1.5V MAXIMUM OUTPUT CURRENT (mA) When the converter is in Burst Mode operation, the peak current of the inductor is set to approximately 100mA regardless of the output load. Each burst event can last from a few cycles at light loads to almost continuously cycling with short sleep intervals at moderate loads.
PAGE 8
LTC3405A-1.5/LTC3405A-1.8 U W U U APPLICATIO S I FOR ATIO The basic LTC3405A series parts application circuit is shown in Figure 1. External component selection is driven by the load requirement and begins with the selection of L followed by CIN and COUT. Inductor Selection For most applications, the inductor value will fall in the range of 2.2µH to 10µH. Its value is determined by the desired ripple current.
PAGE 9
LTC3405A-1.5/LTC3405A-1.8 U W U U APPLICATIO S I FOR ATIO Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications.
PAGE 10
LTC3405A-1.5/LTC3405A-1.8 U W U U APPLICATIO S I FOR ATIO 2. I2R losses are calculated from the resistances of the internal switches, RSW, and external inductor RL. In continuous mode, the average output current flowing through inductor L is “chopped” between the main switch and the synchronous switch.
PAGE 11
LTC3405A-1.5/LTC3405A-1.8 U W U U APPLICATIO S I FOR ATIO PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3405A series parts. These items are also illustrated graphically in Figures 4 and 5. Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide. 2.
PAGE 12
LTC3405A-1.5/LTC3405A-1.8 U W U U APPLICATIO S I FOR ATIO VIN 2.7V TO 4.2V 4 CIN** 4.7µF CER VIN 3 SW 6.8µH* VOUT 1.8V LTC3405A-1.8 1 6 COUT** 4.7µF CER RUN MODE 5 VOUT GND 2 *SUMIDA CMD4D11-6R8MC ** TAIYO YUDEN JMK212BJ475MG 3405A1518 F06a Figure 6a. 100 VIN = 2.7V 90 VIN = 4.2V EFFICIENCY (%) 60 VIN = 3.6V 70 60 50 40 30 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 3405A1518 F06b Figure 6b. VOUT 100mV/DIV AC COUPLED IL 200mA/DIV IL 200mA/DIV VIN = 3.6V 20µs/DIV VOUT = 1.
PAGE 13
LTC3405A-1.5/LTC3405A-1.8 U TYPICAL APPLICATIO S Single Li-Ion to 1.5V/300mA Regulator for High Efficiency and Small Footprint VIN 2.7V TO 4.2V 4 CIN** 4.7µF CER VIN 3 SW 4.7µH* VOUT 1.5V LTC3405A-1.5 1 6 COUT1** 4.7µF CER RUN MODE 5 VOUT GND 3405A1518 TA02a 2 *MURATA LQH32CN4R7M33 **TAIYO YUDEN CERAMIC JMK212BJ475MG 100 VIN = 2.7V 90 VIN = 4.2V VIN = 3.6V EFFICIENCY (%) 60 70 60 50 40 30 0.
PAGE 14
LTC3405A-1.5/LTC3405A-1.8 U TYPICAL APPLICATIO S Single Li-Ion to 1.5V/150mA Regulator Using All Ceramic Capacitors Optimized for Smallest Footprint VIN 2.7V TO 4.2V 4 CIN** 2.2µF CER VIN SW 3 2.2µH* LTC3405A-1.5 1 6 COUT1** 2.2µF CER RUN MODE VOUT GND VOUT 1.5V 5 3405A1518 TA03a 2 *TAIYO YUDEN LB2012T2R2M **TAIYO YUDEN CERAMIC LMK212BJ225MG 90 VOUT = 1.5V VIN = 2.7V EFFICIENCY (%) 80 VIN = 3.6V 70 VIN = 4.2V 60 50 40 30 0.
PAGE 15
LTC3405A-1.5/LTC3405A-1.8 U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 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 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 16
LTC3405A-1.5/LTC3405A-1.8 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1616 500mA (IOUT), 1.4MHz, High Efficiency Step-Down DC/DC Converter 90% Efficiency, VIN = 3.6V to 25V, VOUT = 1.25V, IQ = 1.9mA ISD = <1µA, ThinSOT Package LT1676 450mA (IOUT), 100kHz, High Efficiency Step-Down DC/DC Converter 90% Efficiency, VIN = 7.4V to 60V, VOUT = 1.24V, IQ = 3.2mA ISD = 2.5µA, S8 Package LT1765 25V, 2.75A (IOUT), 1.25MHz, High Efficiency Step-Down DC/DC Converter 90% Efficiency, VIN = 3.