Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Holder TSOT 23 5

LTC34 06B

3406bfa

■

High Efficiency: Up to 96%

■

600mA Output Current at V

= 3V

■

2.5V to 5.5V Input Voltage Range

■

1.5MHz Constant Frequency Operation

■

No Schottky Diode Required

■

Low Dropout Operation: 100% Duty Cycle

■

Low Quiescent Current: 300µA

■

0.6V Reference Allows Low Output Voltages

■

Shutdown Mode Draws <1µA Supply Current

■

Current Mode Operation for Excellent Line and

Load Transient Response

■

Overtemperature Protected

■

Low Profile (1mm) ThinSOT

Package

The LTC

3406B is a high efficiency monolithic synchro-

nous buck regulator using a constant frequency, current

mode architecture. The device is available in an adjustable

version and fixed output voltages of 1.5V and 1.8V. Supply

current with no load is 300µA and drops to <1µA in

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

LTC3406B ideally suited for single Li-Ion battery-powered

applications. 100% duty cycle provides low dropout op-

eration, extending battery life in portable systems. PWM

pulse skipping mode operation provides very low output

ripple voltage for noise sensitive applications.

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. Low

output voltages are easily supported with the 0.6V feed-

back reference voltage. The LTC3406B is available in a low

profile (1mm) ThinSOT package. Refer to LTC3406 for

applications that require Burst Mode

operation.

■

Cellular Telephones

■

Personal Information Appliances

■

Wireless and DSL Modems

■

Digital Still Cameras

■

MP3 Players

■

Portable Instruments

Figure 1a. High Efficiency Step-Down Converter

1.5MHz, 600mA

Synchronous Step-Down

Regulator in ThinSOT

Figure 1b. Efficiency vs Load Current

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

Burst Mode is a registered trademark of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

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

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

4.7µF

CER

2.7V

TO 5.5V

†

LTC3406B-1.8

RUN

2.2µH*

3406B F01a

MURATA LQH32CN2R2M33

TAIYO YUDEN JMK212BJ475MG

TAIYO YUDEN JMK316BJ106ML

OUT

GND

OUT

†

10µF

CER

OUT

1.8V

600mA

OUTPUT CURRENT (mA)

0.1

EFFICIENCY (%)

1000

100

3406B F01b

1 100

= 2.7V

OUT

= 1.8V

= 3.6V

= 4.2V

Summary of content (16 pages)

PAGE 1
LTC3406B 1.5MHz, 600mA Synchronous Step-Down Regulator in ThinSOT U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC ®3406B is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. The device is available in an adjustable version and fixed output voltages of 1.5V and 1.8V. Supply current with no load is 300µA and drops to <1µA in shutdown. The 2.5V to 5.
PAGE 2
LTC3406B U W W W ABSOLUTE AXI U RATI GS (Note 1) Input Supply Voltage .................................. – 0.3V to 6V RUN, VFB Voltages ..................................... – 0.3V to VIN SW Voltage .................................. – 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 ........................ 1.3A Operating Temperature Range (Note 2) ..
PAGE 3
LTC3406B ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 3.6V unless otherwise specified. SYMBOL PARAMETER CONDITIONS VRUN RUN Threshold ● IRUN RUN Leakage Current ● Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3406BE is guaranteed to meet performance specifications from 0°C to 70°C.
PAGE 4
LTC3406B U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure1a Except for the Resistive Divider Resistor Values) Oscillator Frequency vs Supply Voltage 1.844 TA = 25°C 1.5 1.4 1.3 1.2 2 3 4 5 SUPPLY VOLTAGE (V) 6 1.824 0.5 1.814 1.804 1.784 0.1 0.2 0.1 340 320 300 280 260 240 220 MAIN SWITCH SYNCHRONOUS SWITCH 50 25 75 0 TEMPERATURE (°C) DYNAMIC SUPPLY CURRENT (µA) DYNAMIC SUPPLY CURRENT (µA) RDS(ON) (Ω) 0.
PAGE 5
LTC3406B U W TYPICAL PERFOR A CE CHARACTERISTICS (From Figure 1a Except for the Resistive Divider Resistor Values) Start-Up from Shutdown Load Step RUN 5V/DIV Load Step VOUT 100mV/DIV AC COUPLED VOUT 1V/DIV VOUT 100mV/DIV AC COUPLED IL 500mA/DIV IL 500mA/DIV IL 500mA/DIV ILOAD 500mA/DIV ILOAD 500mA/DIV VIN = 3.6V 40µs/DIV VOUT = 1.8V ILOAD = 600mA (LOAD: 3Ω RESISTOR) 3406B G16 3406B G17 VIN = 3.6V 20µs/DIV VOUT = 1.
PAGE 6
LTC3406B W FU CTIO AL DIAGRA U U SLOPE COMP OSC OSC 4 VIN FREQ SHIFT – VFB /VOUT + 5 LTC3406B-1.5 R1 + R2 = 550k 0.6V R1 FB LTC3406B-1.8 R1 + R2 = 540k + ICOMP R2 S Q R Q RS LATCH VIN – 0.6V REF 0.
PAGE 7
LTC3406B U OPERATIO (Refer to Functional Diagram) Dropout Operation Slope Compensation and Inductor Peak Current As the input supply voltage decreases to a value approaching the output voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the main switch to remain on for more than one cycle until it reaches 100% duty cycle.
PAGE 8
LTC3406B U W U U APPLICATIO S I FOR ATIO The basic LTC3406B 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 9
LTC3406B U W U U APPLICATIO S I FOR ATIO Typically, once the ESR requirement for COUT has been met, the RMS current rating generally far exceeds the IRIPPLE(P-P) requirement. The output ripple ∆VOUT is determined by: ⎛ 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.
PAGE 10
LTC3406B U W U U APPLICATIO S I FOR ATIO Although all dissipative elements in the circuit produce losses, two main sources usually account for most of the losses in LTC3406B circuits: VIN quiescent current and I2R losses. The VIN quiescent current loss dominates the efficiency loss at very low load currents whereas the I2R loss dominates the efficiency loss at medium to high load currents.
PAGE 11
LTC3406B U W U U APPLICATIO S I FOR ATIO The junction temperature, TJ, is given by: T J = TA + TR where TA is the ambient temperature. As an example, consider the LTC3406B in dropout at an input voltage of 2.7V, a load current of 600mA and an ambient temperature of 70°C. From the typical performance graph of switch resistance, the RDS(ON) of the P-channel switch at 70°C is approximately 0.52Ω. Therefore, power dissipated by the part is: PD = ILOAD2 • RDS(ON) = 187.
PAGE 12
LTC3406B U W U U APPLICATIO S I FOR ATIO 1 RUN VFB 5 LTC3406B 2 – 3 + L1 SW RUN LTC3406B-1.8 COUT VOUT 1 R1 R2 GND VIN 2 CFWD 4 – 5 COUT VOUT CIN GND VOUT + 3 L1 SW VIN 4 CIN + VIN VIN – 3406B F05b 3406B F05a BOLD LINES INDICATE HIGH CURRENT PATHS BOLD LINES INDICATE HIGH CURRENT PATHS Figure 5a. LTC3406B Layout Diagram Figure 5b. LTC3406B-1.8 Layout Diagram VIA TO GND R1 L1 PIN 1 CFWD LTC3406B LTC3406B-1.
PAGE 13
LTC3406B U W U U APPLICATIO S I FOR ATIO For the feedback resistors, choose R1 = 316k. R2 can then be calculated from equation (2) to be: Figure 7 shows the complete circuit along with its efficiency curve. 100 ⎛V ⎞ R2 = ⎜ OUT − 1⎟ R1 = 1000k ⎝ 0.6 ⎠ 4 CIN† 4.7µF CER VIN SW 2.2µH* 3 VOUT 2.5V 22pF COUT** 10µF CER LTC3406B 1 VFB RUN VIN = 4.2V 80 5 EFFICIENCY (%) VIN 2.7V TO 4.2V VOUT = 2.5V 90 50 40 VIN = 3.6V 20 316k 2 60 30 1M GND VIN = 2.7V 70 10 0.
PAGE 14
LTC3406B U TYPICAL APPLICATIO S Single Li-Ion 1.2V/600mA Regulator for High Efficiency and Small Footprint Efficiency vs Output Current 100 4 CIN† 4.7µF CER VIN SW 3 2.2µH* VOUT 1.2V 22pF COUT** 10µF CER LTC3406B 1 VFB RUN 5 GND 2 301k *MURATA LQH32CN2R2M33 ** TAIYO YUDEN JHK316BJ106ML † TAIYO YUDEN JMK212BJ475MG 3406B TA09 301k VOUT = 1.2V 90 VIN = 2.7V 80 EFFICIENCY (%) VIN 2.7V TO 4.2V 70 VIN = 3.6V 60 50 VIN = 4.2V 40 30 20 10 0.
PAGE 15
LTC3406B U PACKAGE DESCRIPTIO S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 TYP 5 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) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4.
PAGE 16
LTC3406B U TYPICAL APPLICATIO 5V Input to 3.3V/0.6A Regulator VIN 5V 4 † CIN 4.7µF CER VIN SW 3 2.2µH* COUT** 10µF CER LTC3406B 1 VFB RUN VOUT 3.3V 22pF 5 GND 2 1M *MURATA LQH32CN2R2M33 ** TAIYO YUDEN JHK316BJ106ML † TAIYO YUDEN JMK212BJ475MG 3406B TA13 221k 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.