Datasheet

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LTC3406AB

3406abfa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

1.5MHz, 600mA

Synchronous Step-Down

Regulator in ThinSOT

The LTC

3406AB is a high efﬁ ciency monolithic synchro-

nous buck regulator using a constant frequency, current

mode architecture. Supply current with no load is 200μA,

dropping to <1μA in shutdown. The 2.5V to 5.5V input

voltage range makes the LTC3406AB ideally suited for

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

cycle provides low dropout operation, extending battery

run time in portable systems. PWM pulse skipping mode

operation provides very low output ripple voltage for noise

sensitive applications. Refer to LTC3406A for applications

that require Burst Mode

operation.

Switching frequency is internally set at 1.5MHz, allowing

the use of small surface mount inductors and capacitors.

The internal synchronous switch increases efﬁ ciency

and eliminates the need for an external Schottky diode.

Low output voltages are easily supported with the 0.6V

feedback reference voltage. The LTC3406AB is available

in a low proﬁ le (1mm) ThinSOT package.

Efﬁ ciency vs Load Current

■

High Efﬁ ciency: Up to 96%

■

600mA Output Current

■

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: 200μA

■

±2%

0.6V Reference

■

Shutdown Mode Draws <1μA Supply Current

■

Internal Soft-Start Limits Inrush Current

■

Current Mode Operation for Excellent Line and

Load Transient Response

■

Overtemperature Protected

■

Low Proﬁ le (1mm) ThinSOT

Package

■

Cellular Telephones

■

Satellite and GPS Receivers

■

Wireless and DSL Modems

■

Digital Still Cameras

■

Media Players

■

Portable Instruments

, LT, LTC, LTM and Burst Mode 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 5481178, 6580258.

4.7μF

CER

LTC3406AB

RUN

2.2μH

22pF

619k

309k

3406AB TA09

GND

10μF

CER

1.8V, 600mA

OUT

OUTPUT CURRENT (mA)

0.1

EFFICIENCY (%)

1000

100

3406B TA14

1 100

OUT

= 1.8V

= 2.7V

= 3.6V

= 4.2V

Summary of content (16 pages)

PAGE 1
LTC3406AB 1.5MHz, 600mA Synchronous Step-Down Regulator in ThinSOT DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ High Efficiency: Up to 96% 600mA Output Current 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: 200μA ±2% 0.
PAGE 2
LTC3406AB ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Input Supply Voltage ....................................– 0.3V to 6V RUN, VFB Voltages .......................................–0.3V to VIN SW Voltage (DC) ........................... – 0.3V to (VIN + 0.3V) P-Channel Switch Source Current (DC) (Note 7)................................................................800mA N-Channel Switch Sink Current (DC) (Note 7) .....800mA Peak SW Sink and Source Current (Note 7) .............1.
PAGE 3
LTC3406AB ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.6V unless otherwise speciﬁed. SYMBOL PARAMETER VRUN RUN Threshold ● RUN Leakage Current ● IRUN CONDITIONS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
PAGE 4
LTC3406AB TYPICAL PERFORMANCE CHARACTERISTICS (From Front Page Figure Except for the Resistive Divider Resistor Values) Oscillator Frequency vs Temperature 1.55 1.50 1.45 1.40 1.35 50 25 0 75 TEMPERATURE (°C) 100 125 1.812 1.50 1.45 1.40 1.35 1.30 1.796 1.792 1.784 1.20 1.780 2.0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 5.5 RDS(ON) (Ω) 0.30 0.20 Dynamic Supply Current 300 VIN = 2.7V VIN = 3.6V 0.25 VIN = 4.2V 0.20 0.15 0.
PAGE 5
LTC3406AB TYPICAL PERFORMANCE CHARACTERISTICS (From Front Page Figure Except for the Resistive Divider Resistor Values) Start-Up from Shutdown Load Step Load Step VOUT 200mV/DIV VOUT 200mV/DIV IL 500mA/DIV IL 500mA/DIV ILOAD 500mA/DIV ILOAD 500mA/DIV RUN 2V/DIV VOUT 1V/DIV ILOAD 500mA/DIV VIN = 3.6V 400μs/DIV VOUT = 1.8V ILOAD = 600mA (3Ω RES) 3406B G31 VIN = 3.6V 20μs/DIV VOUT = 1.8V ILOAD = 0mA TO 600mA Load Step VIN = 3.6V 20μs/DIV VOUT = 1.
PAGE 6
LTC3406AB FUNCTIONAL DIAGRAM SLOPE COMP OSC OSC 4 VIN FREQ SHIFT – – + 5 0.6V + – EA S Q R Q RS LATCH VIN RUN SWITCHING LOGIC AND BLANKING CIRCUIT ANTISHOOTTHRU 3 SW 0.6V REF SHUTDOWN + 1 5Ω + ICOMP VFB IRCMP 2 GND – 3406AB BD OPERATION (Refer to Functional Diagram) Main Control Loop The LTC3406AB 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
LTC3406AB OPERATION (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
LTC3406AB APPLICATIONS INFORMATION The basic LTC3406AB application circuit is shown on the front page. 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) MAX DC CURRENT (A) SIZE W × L × H (mm3) 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.
PAGE 9
LTC3406AB APPLICATIONS INFORMATION 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 ΔVOUT is determined by: ⎛ 1 ⎞ ΔVOUT ≅ ΔIL ⎜ ESR + 8 fCOUT ⎟⎠ ⎝ where f = operating frequency, COUT = output capacitance and ΔIL = ripple current in the inductor. For a ﬁxed output voltage, the output ripple is highest at maximum input voltage since ΔIL increases with input voltage.
PAGE 10
LTC3406AB APPLICATIONS INFORMATION Although all dissipative elements in the circuit produce losses, two main sources usually account for most of the losses in LTC3406AB 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
LTC3406AB APPLICATIONS INFORMATION The junction temperature, TJ, is given by: TJ = TA + TR where TA is the ambient temperature. As an example, consider the LTC3406AB 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 0.27Ω. Therefore, power dissipated by the part is: PD = ILOAD2 • RDS(ON) = 97.2mW For the SOT-23 package, the θJA is 250°C/ W.
PAGE 12
LTC3406AB APPLICATIONS INFORMATION 1 RUN VFB LTC3406AB 2 5 R2 R1 GND – COUT VOUT 3 + L1 SW VIN CFWD 4 CIN + VIN – BOLD LINES INDICATE HIGH CURRENT PATHS 3406AB F05a Figure 3. LTC3406AB Layout Diagram VIA TO VIN R1 CFWD LTC3406AB L1 VIA TO VOUT R2 PIN 1 VOUT VIN SW COUT CIN GND 3406AB F06a Figure 4. LTC3406AB Suggested Layout Design Example As a design example, assume the LTC3406AB is used in a single lithium-ion battery-powered cellular phone application.
PAGE 13
LTC3406AB APPLICATIONS INFORMATION For the feedback resistors, choose R1 = 316k. R2 can then be calculated from Equation (2) to be: ⎛V ⎞ R2 = ⎜ OUT − 1⎟ R1= 1000k ⎝ 0.6 ⎠ Figure 5 shows the complete circuit along with its efﬁciency curve. (4) 100 90 4 † CIN 4.7μF CER VIN SW 3 2.2μH* 22pF VFB RUN GND 2 70 COUT** 10μF CER LTC3406AB 1 80 2.5V, 600mA VOUT 5 1M *MURATA LQH32CN2R2M33 ** TAIYO YUDEN JHK316BJ106ML † 3406AB TA09a TAIYO YUDEN JMK212BJ475MG 316k EFFICIENCY (%) VIN VOUT = 2.
PAGE 14
LTC3406AB TYPICAL APPLICATIONS Single Li-Ion 1.2V/600mA Regulator for High Efﬁciency and Small Footprint VIN † CIN 4.7μF CER SW 3 VFB RUN GND 2 1.2V, 600mA VOUT 22pF COUT** 10μF CER LTC3406AB 1 100 2.2μH* 5 301k *MURATA LQH32CN2R2M33 ** TAIYO YUDEN JHK316BJ106ML † TAIYO YUDEN JMK212BJ475MG 3406AB TA09b 301k 90 VOUT = 1.2V 80 70 EFFICIENCY (%) VIN Efﬁciency vs Load Current 60 50 40 30 20 VIN = 2.7V VIN = 3.6V VIN = 4.2V 10 0 0.
PAGE 15
LTC3406AB PACKAGE DESCRIPTION S5 Package 5-Lead Plastic SOT-23 (Reference LTC DWG # 05-08-1633 Rev B) 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
LTC3406AB RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3406/LTC3406B 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converters 96% Efﬁciency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20μA, ISD <1μA, ThinSOT Package LTC3407/LTC3407-2 Dual 600mA/800mA (IOUT), 1.5MHz/2.25MHz, Synchronous Step-Down DC/DC Converters 95% Efﬁciency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA, ISD <1μA, MS10E, DFN Packages LTC3410/LTC3410B 300mA (IOUT), 2.