Datasheet BL3406B-1.0V, BL3406B-1.2V, BL3406B-1.5V, BL3406B-1.8V, BL3406B-2.5V Datasheet (Belling)

BL3406B

V

µ H

1.5 MHz, 800mA Synchronous Buck Converter

FEATURES

• High Efficiency: Up to 96%

• 1.5MHz Constant Switching Frequency

• Current Mode Operation for Excellent

Line and Load Transient Response

• No Schottky Diode Required

• 2.5V to 5.5V Input Voltage Range

• 1.0V,1.2V,1.5V,1.8V,2.5V and 3.3V

Fixed/Adjustable Output Voltage

• 100% Duty Cycle in Dropout Mode

• Low Quiescent Current: 180µA

• Over temperature Protection

• Short Circuit Protection

• Shutdown Quiescent Current < 1µA

• Space Saving 5-Pin Thin SOT23 Package

APPLICATIONS

• Cellular and Smart Phones

• Wireless Handsets and DSL Modems

• Microprocessors and DSP Core Supplies

• PDAs

• Digital Still and Video Cameras

• GPS Receivers

DESCRIPTION

The BL3406B is a constant frequency,

1.5MHz, slope compensated current mode PWM step-down converter working under an input voltage range of 2.5V to 5.5V. This feature makes the BL3406B suitable for single cell Li-ion battery-powered applications. The internal synchronous rectifier is desired to increase efficiency without an external Schottky diode. 100% duty cycle capability extends battery life in portable devices, while the quiescent current is 180µA at no load, and drops to < 1µA in shutdown. Pulse Skipping Mode operation increases efficiency at light loads, further extending battery life. The BL3406B is offered in a low profile (1mm) 5-pin, thin SOT23 package, and is available in an adjustable version and fixed output versions of 1.0V, 1.2V, 1.5V , 1.8V, 2.5V and

3.3V.

• MP3/MP4/MP5 Players

• Portable Instruments

ORDERING INFORMATION TYPICAL APPLICATION

BL3406B –XX X XXX

Package： TRN: TSOT23-5 RN: SOT23-5

Features: P: Standard (default,

lead free)

C: Customized

Output Voltage： 10: 1.0V 12: 1.2V 15: 1.5V 18: 1.8V 25: 2.5V 33: 3.3V AD: Adjustable

V

IN

2.7V - 4.2V

C1

4.7uF

4

IN

BL3406B-ADJ

1

Run

GND

SW

V

FB

2

L1

2.2

3

C3

22pF

5

R2

200k

R1

100k

Figure 1. BL3406B-ADJ Typical Application Circuit

V

1.8V

OUT

C2

10uF

1

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

Absolute Maximum Rating

Input Supply Voltage…………………-0.3V to +6V RUN, VFB Voltages……………………-0.3V to +VIN SW Voltages……………………-0.3V to (VIN+0.3V) P-Channel Switch Source Current (DC) ………1A N-Channel Switch Sink Current (DC) …………1A

(Note 1)

Peak SW Sink and Source Current……………1.4A Operating Temperature Range……-40°C to +85°C Junction Temperature

(Note2)

………………+125°C Storage Temperature Range………-65°C to +150°C Lead Temperature (Soldering, 10s) ………+300°C

Package Information

Adjustable Output Version Fixed Output Versions

SOT23-5

TOP VIEW

V

RUN

GND

SW

1

2

3

MARKING

FB

5

4

V

IN

SOT23-5

TOP VIEW

RUN

GND

SW

1

2

3

MARKING

5

4

Part Number Top Mark Temp Range BL3406B-Adj

A J Y W

(Note3)

-40°C to +85°C

Part Number Top Mark Temp Range

BL3406B-1.0V A A Y W BL3406B-1.2V A B Y W BL3406B-1.5V A C Y W BL3406B-1.8V A D Y W

-40°C to +85°C

BL3406B-2.5V A E Y W BL3406B-3.3V A F Y W

Y 9 A B C D

Year 2009 2010 2011 2012 2013

W 1 … 26 27 28 … 53 54

Week A … Y Z a … y z

Thermal Resistance

Package JA JC TSOT23-5 SOT23-5

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: TJ is calculated from the ambient temperature T

T

Note 3: Y: Year of wafer manufacturing W: Week of wafer manufacturing Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz copper.

= TA + (PD) x (220°C/W).

J

220°C/W 250°C/W

(Note 4)

110°C/W 130°C/W

and power dissipation P

A

according to the following formula:

D

V

OUT

V

IN

2

1.5 MHz, 800mA Synchronous Buck Converter

Pin Description

PIN NAME FUNCTION

Regulator Enable Control Input. Drive RUN above 1.5V to turn on the part.

1 RUN

2 GND Ground

3 SW

4 VIN

5 VFB/V

Drive RUN below 0.3V to turn it off. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave RUN floating.

Power Switch Output. It is the switch node connection to external inductor. This pin connects to the drains of the internal P-Channel and N-Channel MOSFET switches. Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 2.2µF or greater ceramic capacitor.

VFB (BL3406B-Adj): Feedback Input Pin. Connect FB to the center point of the external resistor divider. The regulated voltage on this pin is 0.6V. V

OUT

(BL3406B-1.2/BL3406B-1.5/BL3406B-1.8): Output Voltage Feedback Pin.

OUT

An internal resistive divider divides the output voltage down for comparison to the internal reference voltage.

Block Diagram

BL3406B

3

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

Electrical Characteristics

(VIN =V

Input Voltage Range 2.5 5.5 V

Input DC Supply Current

Regulated Feedback

VFB Input Bias Current VFB = 0.65V ±30 nA

= 3.6V, TA = 25°C, unless otherwise noted.)

RUN

Parameter Conditions MIN TYP MAX Unit

Active Mode

Shutdown Mode

Voltage

VFB=0.5V or V VFB=0V, VIN=4.2V

TA= -40°C ≤ TA ≤ 85°C 0.5850 0.6000 0.6150

(Note 5)

=90%

OUT

TA = +25°C 0.5880 0.6000 0.6120

TA= 0°C ≤ TA ≤ 85°C 0.5865 0.6000 0.6135

180

0.1

300

1.0

µA µA

V V V

Reference Voltage Line

Regulation

Regulated Output Voltage

Output Overvoltage

Lockout

Output Voltage Line

Regulation

Output Voltage Load

Regulation

Peak Inductor Current

Oscillator Frequency VFB=0.6V or V

R

Note 5: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.

of P-CH MOSFET

DS(ON)

of N-CH MOSFET

DS(ON)

SW Leakage Current V

RUN Threshold -40°C ≤ TA ≤ 85°C 0.3 1.1 1.30 V

RUN Leakage Current ±0.01

BL3406B-1.2, -40°C ≤ TA ≤ 85°C 1.164 1.200 1.236 BL3406B-1.8, -40°C ≤ TA ≤ 85°C 1.746 1.800 1.854

∆V

OVL

∆V

RUN

VIN = 2.5V to 5.5V 0.04 0.4 %/V

= V

OVL

VIN=3V, VFB=0.5V or V

– VFB, Adjustable Version

OVL

= V

= 0V, VSW= 0V or 5V, VIN = 5V ±0.01

– V

OVL

VIN = 2.5V to 5.5V 0.04 0.40 %

Duty Cycle <35%

I

SW

ISW = -300mA 0.35 0.45 Ω

, Fixed Version 2.5 7.8 13 %

OUT

0.5 %

=90%

OUT

=100% 1.2 1.5 1.8 MHz

OUT

= 300mA 0.40 0.50 Ω

20 50 80 mV

1.2 A

V V

±1 µA

4

1.5 MHz, 800mA Synchronous Buck Converter

Typical Performance Characteristics

(Test Figure 1 above unless otherwise specified)

BL3406B

Efficiency vs. Output Current

90

V

OUT

=1.8V

L=2.2uH

80

70

60

50

Efficiency(%)

40

30

20

0.1 1 10 100 1000

Vin=2.7V Vin=3.6V Vin=4.2V

Output Current(mA)

0.606

Reference Voltage vs. Temperature

VIN=3.6V

0.605

0.604

Reference Voltage(V)

0.603

0.602

-50 -25 0 25 50 75 100 125

Temperature(°C

)

Supply Current vs. Supply Voltage Start_up from Shutdown

245

V

OUT

240

235

230

225

220

215

210

205

Dynamic Supply Current(uA)

200

195

=1.8V

I

LOAD

=0A

TA=25°C

2 3 4 5 6

Supply Voltage(V)

2.2

Output Voltage vs. Load Current

VIN=3.6V

2.1

TA=25°C

2.0

1.9

1.8

1.7

1.6

Output Voltage(V)

1.5

1.4

1.3 0 200 400 600 800 1000 1200

Load Current(mA)

Output Voltage vs. Input Voltage

1.820

I

LOAD

1.815

1.810

1.805

(V)

1.800

OUT

V

1.795

1.790

1.785

1.780

2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 5.7

I I

LOAD

=10mA =100mA =600mA

VIN(V)

PPMIC BU www.belling.com.cn BL3406B Rev 1.5 Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited

5

Load Step

1.5 MHz, 800mA Synchronous Buck Converter

BL3406B

Load Step

Pulse Skipping Mode

Load Step

Output Short

6

1.5 MHz, 800mA Synchronous Buck Converter

Operation

The BL3406B uses a constant frequency, current mode step-down architecture. Both the main switch (P-channel MOSFET) and the synchronous rectifier (N-channel MOSFET) are integrated internally. This Step-Down DC-DC Converter can supply 800mA output current over a wide input voltage range from 2.5V to 5.5V. The over voltage comparator OVDET guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the fault is removed.

Current Mode PWM Control

Slope compensated current mode PWM control provides stable switching and cycleby-cycle current limit for excellent load and line responses. During normal operation, the internal main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak inductor current reaches the controlled value. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, I

, or the beginning of the next clock cycle.

RCMP

Pulse Skipping Mode Operation

At very light loads, the BL3406B will automatically enter Pulse Skipping Mode to increase efficiency, further extending battery life. In this mode, the control loop skips PWM pulses while maintaining output in regulation, and the switching frequency depends on the load condition. This is a kind of PFM mode operation.

Dropout Operation

When the input voltage decreases toward the

BL3406B

value of the output voltage, the BL3406B will keep the main switch on for more than one switching cycle and increases the duty cycle (Note 6) until it reaches 100%. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage, the R and the efficiency of the converter decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC.

Note 6666: The duty cycle D of a step-down converter is defined as:

where TON is the main switch on time, and f is the oscillator frequency (1.5MHz).

Short Circuit Protection

The BL3406B has short circuit protection. When output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the PFET current limit. The PFET current limit is also reduced to lower the short circuit current. The frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6V.

Maximum Load Current

The BL3406B will operate with input supply voltage as low as 2.5V, however the maximum load current decreases at lower input voltage due to large IR drop on the main switch and synchronous rectifier.

of the P-Channel MOSFET increases,

DS(ON)

V

fTD

OSCON

V

OUT

IN

%100%100 ×≈××=

OSC

7

V

µ H

1

R

Application Information

Figure 2 below shows the basic application circuit with BL3406B fixed output versions.

V

IN

2.7V - 4.2V

C1

4.7uF

4

IN

BL3406B-18

1

Run

SW

V

GND

2

Figure 2. Basic Application Circuit

with fixed output versions

Setting the Output Voltage

Figure 1 above shows the basic application circuit with BL3406B adjustable output version. The external resistor sets the output voltage according to the following equation:

2

R

OUT

1(6.0

VV

)

+×=

Table 1—Resistor Selection vs.

Output Voltage Setting

VOUT R1 R2

1.0V 180 k

1.2V 180 k

1.5V 180 k

1.8V 180 k

2.5V 158 k

3.3V 180 k

Ω(1%) Ω(1%) Ω(1%) Ω(1%) Ω(1%) Ω(1%)

Inductor Selection

The output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of the full load current at the maximum input voltage. In continuous mode, the ripple current is determined by:

1

I −

=∆

A reasonable starting point for setting ripple current is ∆IL=320mA (40% of 800mA). For

V

OUTL

Lf

×

L1

2.2

3

5

OUT

180 k 270 k 360 k 499 k 810 k

V

OUT

V

IN

120 k

)1(

Ω(1%) Ω(1%) Ω(1%) Ω(1%) Ω(1%) Ω(1%)

V

OUT

C2

10uF

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

output voltages above 2.0V, when efficiency at light load condition is important, the minimum recommended inductor is 2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance below 150mΩ. For higher

1.8V

efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 1120mA rated inductor should be enough for most applications (800mA+320mA).

Input Capacitor Selection

The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. In continuous mode, the source current of the main switch is a square wave of duty cycle V

OUT/VIN

. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by:

VVV

−

II

≈

OMAXRMS

OUTINOUT

V

IN

This formula has a maximum at VIN =2V where I

RMS

= I

/2. This simple worst-case

OUT

5.0

)]([

OUT

condition is commonly used for design because even significant deviations do not offer much relief. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current.

Output Capacitor Selection

The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching

,

8

V

V IN

µ H

V

frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple ∆V

≤∆

V

OUT

is determined by:

−×

VVV

××



OUTINOUT



ESR



LfV





1)(

+×

8

OSCOSCIN

 

××

Cf

2



Layout Considerations

When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the BL3406B. These items are also illustrated graphically in Figures 5 and 6. Check the following in your layout:

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

1. The power traces, consisting of the GND

trace, the SW trace and the VIN trace should be kept short, direct and wide.

2. Does the VFB pin connect directly to the

feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of Cout and ground.

3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETS.

4. Keep the switching node, SW, away from the sensitive V

5. Keep the (-) plates of CIN and C close as possible.

node.

FB

OUT

as

2.7V - 4.2V

V

IN

C1

4.7uF

4

IN

BL3406B-ADJ

1

Run

GND

SW

V

FB

2

L1

2.2 µ H

3

C3

22pF

5

R2

200k

R1

100k

OUT

C2

10uF

1.8V

V

IN

2.7V - 4.2V

C1

4.7uF

4

BL3406B-18

1

Run

GND

SW

V

OUT

2

L1

2.2

3

5

Figure 3. BL3406B-ADJ Layout Circuit Figure 4. BL3406B-1.8 Layout Circuit

1.8V

OUT

C2

10uF

Figure 5. BL3406B-ADJ Suggested Layout Figure 6. BL3406B-1.8 Suggested Layout

9

Package Description

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

Symbol

A 0.889 1.295 0.035 0.051

A1 0.000 0.152 0.000 0.006

B 1.397 1.803 0.055 0.071

b 0.356 0.559 0.014 0.022

C 2.591 2.997 0.102 0.118

D 2.692 3.099 0.106 0.122

e 0.838 1.041 0.033 0.041

H 0.080 0.254 0.003 0.010

L 0.300 0.610 0.012 0.024

Dimensions In Millimeters Dimensions In Inches

Min Max Min Max

SOT-23-5 Surface Mount Package

10

BL3406B

1.5 MHz, 800mA Synchronous Buck Converter

TSOT-23-5 Surface Mount Package

11

Datasheet BL3406B-1.0V, BL3406B-1.2V, BL3406B-1.5V, BL3406B-1.8V, BL3406B-2.5V Datasheet (Belling) [ru]