Datasheet

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LTC3406-1.2

340612fa

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High Efficiency: Up to 90%

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Very Low Quiescent Current: Only 20µA

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600mA 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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Shutdown Mode Draws < 1µA Supply Current

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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

3406-1.2 is a high efficiency monolithic syn-

chronous buck regulator using a constant frequency,

current mode architecture. Supply current during opera-

tion with only 20µA drops <1µA in shutdown. The 2.5V to

5.5V input voltage range makes the LTC3406-1.2 ideally

suited for single Li-Ion battery-powered applications. 100%

duty cycle provides low dropout operation, extending

battery life in portable systems. Automatic Burst Mode

operation further increases efficiency at light loads.

Switching frequency is internally set at 1.5MHz, allowing

the use of small surface mount inductors and capacitors.

The internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. The

LTC3406-1.2 is available in a low profile (1mm) ThinSOT

package.

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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

High Efficiency Step-Down Converter

1.5MHz, 600mA

Synchronous Step-Down

Regulator in ThinSOT

Efficiency and Power Loss

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

4.7µF

CER

2.7V TO 5.5V

LTC3406-1.2

RUN

2.2µH

340612 TA01a

OUT

GND

OUT

10µF

CER

OUT

1.2V

600mA

LOAD CURRENT (mA)

0.1

1000

100

340612 TA01b

1 100

0.1

0.01

0.001

0.00001

0.0001

= 2.7V

= 3.6V

= 4.2V

EFFICIENCY

POWER LOSS

POWER LOSS (W)

EFFICIENCY (%)

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

trademarks are the property of their respective owners. ThinSOT is a trademark of Linear

Technology Corporation. Protected by U.S. Patents including 5481178, 6580258, 6304066,

6127815, 6498466, 6611131.

Summary of content (12 pages)

PAGE 1
LTC3406-1.2 1.5MHz, 600mA Synchronous Step-Down Regulator in ThinSOT U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC ®3406-1.2 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. Supply current during operation with only 20µA drops <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3406-1.2 ideally suited for single Li-Ion battery-powered applications.
PAGE 2
LTC3406-1.2 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 RUN, VOUT Voltages................................... – 0.3V to VIN SW Voltage (DC) ......................... – 0.3V to (VIN + 0.3V) P-Channel Switch Source Current (DC) ............. 800mA N-Channel Switch Sink Current (DC) ................. 800mA Peak SW Sink and Source Current (VIN = 3V)........ 1.3A Operating Temperature Range (Note 2) ..
PAGE 3
LTC3406-1.2 U W TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise specified. (From Figure 1) Efficiency vs Input Voltage Reference Voltage vs Temperature Efficiency and Power Loss 100 1.228 100 VIN = 3.6V 1.218 90 IOUT = 100mA 85 IOUT = 10mA 80 75 70 3 80 70 60 5 4 INPUT VOLTAGE (V) 40 0.1 6 1 10 ILOAD (mA) 340612 G01 1.198 1.188 1.168 –50 –25 1000 100 1.208 1.178 VIN = 2.7V VIN = 3.6V VIN = 4.
PAGE 4
LTC3406-1.2 U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1) Supply Current vs Temperature 50 Switch Leakage vs Temperature 300 VIN = 3.6V ILOAD = 0A 45 VIN = 5.
PAGE 5
LTC3406-1.2 U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1a Except for the Resistive Divider Resistor Values) Load Step Load Step VOUT 100mV/DIV AC COUPLED VOUT 100mV/DIV AC COUPLED ILOAD 500mA/DIV ILOAD 500mA/DIV IL 500mA/DIV IL 500mA/DIV 340612 G16 20µs/DIV 20µs/DIV 340612 G17 VIN = 3.6V ILOAD = 200mA TO 600mA VIN = 3.6V ILOAD = 100mA TO 600mA U U U PI FU CTIO S RUN (Pin 1): Run Control Input. Forcing this pin above 1.5V enables the part. Forcing this pin below 0.
PAGE 6
LTC3406-1.2 U OPERATIO (Refer to Functional Diagram) VIN 2.7V TO 5.5V 4 CIN** 4.7µF CER VIN SW 3 2.2µH* COUT 10µF CER LTC3406-1.2 1 VOUT RUN 5 † VOUT 1.2V 600mA 340612 F01 GND 2 *MURATA LQH3C2R2M24 **TAIYO YUDEN JMK212BJ475MG † TAIYO YUDEN JMK316BJ106ML Figure 1. Typical Application Main Control Loop The LTC3406-1.2 uses a constant frequency, current mode step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal.
PAGE 7
LTC3406-1.2 U W U U APPLICATIO S I FOR ATIO The basic LTC3406-1.2 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. Table 1. Representative Surface Mount Inductors PART NUMBER VALUE (µH) DCR (Ω MAX) Sumida CDRH3D16 1.5 2.2 3.3 4.7 0.043 0.075 0.110 0.162 1.55 1.20 1.10 0.90 3.8 × 3.8 × 1.8 Sumida CMD4D06 2.2 3.3 4.7 0.116 0.174 0.216 0.950 0.770 0.750 3.5 × 4.3 × 0.
PAGE 8
LTC3406-1.2 U W U U APPLICATIO S I FOR ATIO ⎛ 1 ⎞ ∆VOUT ≅ ∆IL ⎜ ESR + ⎟ ⎝ 8fC OUT ⎠ where f = operating frequency, COUT = output capacitance and ∆IL = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since ∆IL increases with input voltage. Aluminum electrolytic and dry tantalum capacitors are both available in surface mount configurations.
PAGE 9
LTC3406-1.2 U W U U APPLICATIO S I FOR ATIO 1. The VIN quiescent current is due to two components: the DC bias current as given in the electrical characteristics and the internal main switch and synchronous switch gate charge currents. The gate charge current results from switching the gate capacitance of the internal power MOSFET switches. Each time the gate is switched from high to low to high again, a packet of charge, dQ, moves from VIN to ground.
PAGE 10
LTC3406-1.2 U W U U APPLICATIO S I FOR ATIO The regulator loop then acts to return VOUT to its steadystate value. During this recovery time VOUT can be monitored for overshoot or ringing that would indicate a stability problem. For a detailed explanation of switching control loop theory, see Application Note 76. A second, more severe transient is caused by switching in loads with large (>1µF) supply bypass capacitors.
PAGE 11
LTC3406-1.2 U TYPICAL APPLICATIO S Single Li-Ion 1.2V/600mA Regulator for Lowest Profile, ≤1mm High 4 VIN 2.7V TO 4.2V CIN** 4.7µF CER VIN SW 3 2.2µH† COUT1* 10µF CER LTC3406-1.2 1 RUN VOUT GND VOUT 1.2V 5 340612 TA02 2 *MURATA GRM219R60JI06KE19B **AVX06036D475MAT † FDK MIPW3226D2R2M LTC3406-1.2 Efficiency Load Step 100 90 VOUT 100mV/DIV AC COUPLED EFFICIENCY (%) 80 70 60 ILOAD 500mA/DIV 50 40 IL 500mA/DIV 30 20 VIN = 2.7V VIN = 3.6V VIN = 4.2V 10 0 0.
PAGE 12
LTC3406-1.2 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 LTC1701/LT1701B 750mA (IOUT), 1MHz, High Efficiency Step-Down DC/DC Converter 90% Efficiency, VIN = 2.5V to 5V, VOUT = 1.