BL3406B

BL3406B
1.5 MHz, 600mA Synchronous Buck Converter
FEATURES
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DESCRIPTION
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: 200μA
Over temperature Protection
Short Circuit Protection
Shutdown Quiescent Current < 1μA
Space Saving 5-Pin Thin SOT23 Package
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 200μA at no load, and drops to < 1μA in
shutdown. Pulse Skipping Mode operation
increases efficiency at light loads, further
extending battery life.
APPLICATIONS
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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.
Cellular and Smart Phones
Wireless Handsets and DSL Modems
Microprocessors and DSP Core Supplies
PDAs
Digital Still and Video Cameras
MP3/MP4/MP5 Players
Portable Instruments
GPS Receivers
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
Default：Adjustable
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2.7V - 4.2V
VIN
4
C1
4.7uF
SW
VIN
3
C3
22pF
BL3406B-ADJ
1
VFB 5
Run
GND
2
L1
2.2 µH
VOUT 1.8V
C2
10uF
R2
200k
R1
100k
Figure 1. BL3406B-ADJ Typical Application Circuit
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BL3406B
1.5MHz, 600mA Synchronous Buck Converter
Absolute Maximum Rating (Note 1)
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) ……800mA
N-Channel Switch Sink Current (DC) ……800mA
Peak SW Sink and Source Current……………1.3A
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
TOP VIEW
TOP VIEW
Run
5
1
GND
2
SW
3
Run
VFB
M
A
R
K
IN
G
4
VIN
TSOT23-5
Part Number
BL3406BAdj
Top Mark
X V Y M(Note3)
1
GND
2
SW
3
5
VOUT
4
VIN
M
A
R
K
IN
G
TSOT23-5
Temp Range
-40°C to +85°C
Part Number
BL3406B-1.0
BL3406B-1.2
BL3406B-1.5
BL3406B-1.8
BL3406B-2.5
BL3406B-3.3
Top Mark
XVYM
XVYM
XVYM
XVYM
XVYM
XVYM
Temp Range
-40°C to +85°C
Thermal Resistance (Note 4)
Package
TSOT23-5
ӨJA
220°C/W
ӨJC
110°C/W
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 TA and power dissipation PD according to the following formula:
TJ = TA + (PD) x (220°C/W).
Note 3:. X:Product Code V:Voltage Code Y:Year M:Month
Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
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BL3406B
1.5MHz, 600mA Synchronous Buck Converter
Pin Description
PIN
NAME
1
RUN
2
GND
3
SW
4
VIN
5
VFB/VOUT
FUNCTION
Regulator Enable Control Input. Drive RUN above 1.5V to turn on the part. Drive RUN
below 0.3V to turn it off. In shutdown, all functions are disabled drawing <1µA supply
current. Do not leave RUN floating.
Ground
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.
VOUT (BL3406B-1.2/BL3406B-1.5/BL3406B-1.8): Output Voltage Feedback Pin. An
internal resistive divider divides the output voltage down for comparison to the internal
reference voltage.
Block Diagram
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BL3406B
1.5 MHz, 600mA Synchronous Buck Converter
Electrical Characteristics (Note 5)
(VIN =VRUN= 3.6V, TA = 25°C, unless otherwise noted.)
Parameter
Conditions
Input Voltage Range
Input DC Supply Current
Active Mode
Shutdown Mode
MIN
TYP
MAX
Unit
5.5
V
300
1.0
0.6120
0.6135
0.6150
µA
µA
V
V
V
±30
nA
0.04
0.4
%/V
1.200
1.800
50
7.8
1.236
1.854
80
13
V
V
mV
%
0.04
0.40
%
2.5
VFB=0.5V or VOUT=90%
VFB=0V, VIN=4.2V
TA = +25°C
Regulated Feedback Voltage TA= 0°C ≤ TA ≤ 85°C
TA= -40°C ≤ TA ≤ 85°C
VFB Input Bias Current
VFB = 0.65V
Reference Voltage Line
Regulation
VIN = 2.5V to 5.5V,
BL3406B-1.2, -40°C ≤ TA ≤ 85°C
BL3406B-1.8, -40°C ≤ TA ≤ 85°C
Output Overvoltage Lockout ∆VOVL = VOVL – VFB, Adjustable Version
∆VOVL = VOVL – VOUT, Fixed Version
Output Voltage Line
VIN = 2.5V to 5.5V
Regulation
Output Voltage Load
Regulation
VIN=3V, VFB=0.5V or VOUT=90%
Peak Inductor Current
Duty Cycle <35%
Oscillator Frequency
VFB=0.6V or VOUT=100%
RDS(ON) of P-CH MOSFET
ISW = 300mA
Regulated Output Voltage
0.5880
0.5865
0.5850
1.164
1.746
20
2.5
200
0.1
0.6000
0.6000
0.6000
0.5
%
0.75
1.00
1.25
A
1.2
1.5
0.40
1.8
0.50
MHz
Ω
RDS(ON) of N-CH MOSFET
ISW = -300mA
0.35
0.45
Ω
SW Leakage
VRUN = 0V, VSW= 0V or 5V, VIN = 5V
±0.01
±1
µA
RUN Threshold
RUN Leakage Current
-40°C ≤ TA ≤ 85°C
1.1
±0.01
1.30
±1
V
µA
0.3
Note 5: 100% production test at +25°C. Specifications over the temperature range are guaranteed by design and characterization.
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BL3406B
1.5 MHz, 600mA Synchronous Buck Converter
Typical Performance Characteristics
(Test Figure 1 above unless otherwise specified)
Efficiency VS Output Current
Output Voltage vs Load Current
2.2
90
VOUT=1.8V
L=2.2uH
80
2.0
Output Voltage(V)
Efficiency(%)
VIN=3.6V
TA=25°C
2.1
70
60
50
40
20
0.1
1
10
100
1.8
1.7
1.6
1.5
Vin=2.7V
Vin=3.6V
Vin=4.2V
30
1.9
1.4
1.3
1000
0
200
400
Output Current(mA)
800
1000
1200
Output Voltage vs Input Voltage
Reference Voltage vs Temperature
0.606
1.820
VIN=3.6V
ILOAD=10mA
ILOAD=100mA
ILOAD=600mA
1.815
0.605
1.810
Vout(V)
Reference Voltage(V)
600
Load Current(mA)
0.604
1.805
1.800
1.795
0.603
1.790
1.785
0.602
-50
-25
0
25
50
75
100
1.780
2.7
125
Temperature(°C)
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
5.4
5.7
VIN(V)
Supply Current vs Supply Voltage
Start_up from Shutdown
245
VOUT=1.8V
ILOAD=0A
TA=25°C
Dynamic Supply Current(uA)
240
235
230
225
220
215
210
205
200
195
2
3
4
5
6
Supply Voltage(V)
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BL3406B
1.5 MHz, 600mA Synchronous Buck Converter
Load Step
Load Step
Load Step
Load Step
Pulse Skipping Mode
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Output Short
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BL3406B
1.5MHz, 600mA 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
600mA 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
voltage then is the input voltage minus the
voltage drop across the main switch and the
inductor. At low input supply voltage, the
RDS(ON) of the P-Channel MOSFET increases,
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 5: The duty cycle D of a step-down converter is
defined as:
D = TON × f OSC × 100% ≈
VOUT
×100%
VIN
where TON is the main switch on time, and fOSC
is the oscillator frequency (1.5MHz).
Maximum Load Current
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,
IRCMP, or the beginning of the next clock cycle.
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.
Application Information
Figure 2 below shows the basic application
circuit with BL3406B fixed output versions.
2.7V - 4.2V
VIN
Pulse Skipping Mode Operation
4
C1
4.7uF
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.
SW
VIN
3
L1
2.2 µH
BL3406B-18
1
VOUT 1.8V
C2
10uF
VOUT 5
Run
GND
2
Figure 2. Basic Application Circuit
with fixed output versions
Dropout Operation
Setting the Output Voltage
When the input voltage decreases toward the
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 5) until it reaches 100%. The output
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:
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BL3406B
1.5 MHz, 600mA Synchronous Buck Converter
VOUT = 0.6V × (1 +
R2
)
R1
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:
ΔI L =
V
1
VOUT (1 − OUT )
f ×L
VIN
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
VOUT/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:
I RMS ≈ I OMAX
A reasonable starting point for setting ripple
current is ∆IL=240mA (40% of 600mA). For
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
efficiency at heavy loads (above 200mA), or
minimal load regulation (but some transient
overshoot), the resistance should be kept
below 100mΩ.
[VOUT (VIN − VOUT )]0.5
VIN
This formula has a maximum at VIN =2VOUT,
where IRMS = IOUT/2. This simple worst-case
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 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 720mA rated inductor
should be enough for most applications
(600mA+120mA).
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
frequency. Ceramic capacitors with X5R or
X7R dielectrics are recommended due to
their low ESR and high ripple current. The
output ripple VOUT is determined by:
Input Capacitor Selection
ΔVOUT ≤
⎞
VOUT × (VIN − VOUT ) ⎛
1
⎟
× ⎜⎜ ESR +
VIN × f OSC × L
8 × f OSC × C 2 ⎟⎠
⎝
The input capacitor reduces the surge current
drawn from the input and switching noise
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BL3406B
1.5MHz, 600mA Synchronous Buck Converter
Package Description
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