BELLING BL3406B-3.3V 1.5 mhz, 800ma synchronous buck converter Datasheet

BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
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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: 180µA
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 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.
APPLICATIONS
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GPS Receivers
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
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
PPMIC BU
BL3406B Rev 1.5
10/2009
2.7V - 4.2V
VIN
4
C1
4.7uF
SW
VIN
3
BL3406B-ADJ
1
VFB 5
Run
GND
2
L1
2.2 µH
C3
22pF
VOUT 1.8V
C2
10uF
R2
200k
R1
100k
Figure 1. BL3406B-ADJ Typical Application Circuit
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BL3406B
1.5 MHz, 800mA 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) ………1A
N-Channel Switch Sink Current (DC) …………1A
Peak SW Sink and Source Current……………1.4A
Operating Temperature Range……-40°C to +85°C
(Note2)
Junction Temperature
………………+125°C
Storage Temperature Range………-65°C to +150°C
Lead Temperature (Soldering, 10s) ………+300°C
Package Information
Adjustable Output Version
RUN
SOT23-5
SOT23-5
TOP VIEW
TOP VIEW
1
5
Y
Year
RUN
GND 2
3
4
Top Mark
(Note3)
AJYW
SW
VIN
3
Part Number
BL3406B-1.0V
BL3406B-1.2V
BL3406B-1.5V
BL3406B-1.8V
BL3406B-2.5V
BL3406B-3.3V
Temp Range
-40°C to +85°C
9
2009
A
2010
B
2011
C
2012
D
2013
1
A
…
…
26
Y
27
Z
28
a
W
Week
1
…
…
53
y
5
VOUT
4
VIN
MARKING
Part Number
BL3406B-Adj
VFB
MARKING
GND 2
SW
Fixed Output Versions
Top Mark
AAYW
ABYW
ACYW
ADYW
AEYW
AFYW
Temp Range
-40°C to +85°C
54
z
Thermal Resistance (Note 4)
Package
TSOT23-5
SOT23-5
ӨJA
220°C/W
250°C/W
ӨJC
110°C/W
130°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: Y: Year of wafer manufacturing W: Week of wafer manufacturing
Note 4: Thermal Resistance is specified with approximately 1 square of 1 oz copper.
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA 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
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA 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
VFB=0.5V or VOUT=90%
Shutdown Mode
VFB=0V, VIN=4.2V
TA = +25°C
Regulated Feedback
TA= 0°C ≤ TA ≤ 85°C
Voltage
TA= -40°C ≤ TA ≤ 85°C
VFB Input Bias Current
VFB = 0.65V
Reference Voltage Line
Regulation
VIN = 2.5V to 5.5V
Regulated Output Voltage
Output Overvoltage
Lockout
Output Voltage Line
Regulation
Output Voltage Load
Regulation
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
2.5
0.5880
0.5865
0.5850
180
0.1
0.6000
0.6000
0.6000
BL3406B-1.2, -40°C ≤ TA ≤ 85°C
BL3406B-1.8, -40°C ≤ TA ≤ 85°C
∆VOVL = VOVL – VFB, Adjustable Version
1.164
1.746
20
1.200
1.800
50
1.236
1.854
80
V
V
mV
∆VOVL = VOVL – VOUT, Fixed Version
2.5
7.8
13
%
0.04
0.40
%
VIN = 2.5V to 5.5V
Oscillator Frequency
RDS(ON) of P-CH MOSFET
VIN=3V, VFB=0.5V or VOUT=90%
Duty Cycle <35%
VFB=0.6V or VOUT=100%
ISW = 300mA
RDS(ON) of N-CH MOSFET
Peak Inductor Current
MIN
1.2
0.5
%
1.2
A
1.5
0.40
1.8
0.50
MHz
Ω
ISW = -300mA
0.35
0.45
Ω
SW Leakage Current
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.
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA 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
1.8
1.7
1.6
1.5
Vin=2.7V
Vin=3.6V
Vin=4.2V
30
1.9
1.4
1.3
1
10
100
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
125
1.780
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
Temperature(°C)
VIN(V)
Supply Current vs. Supply Voltage
Start_up from Shutdown
5.4
5.7
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)
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
Load Step
Load Step
Load Step
Load Step
Pulse Skipping Mode
PPMIC BU
BL3406B Rev 1.5
10/2009
Output Short
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BL3406B
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.
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
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 6: The duty cycle D of a step-down converter is
defined as:
D = TON × f OSC × 100% ≈
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,
IRCMP, or the beginning of the next clock cycle.
VOUT
× 100%
VIN
where TON is the main switch on time, and fOSC
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.
Pulse Skipping Mode Operation
Maximum Load Current
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.
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.
Dropout Operation
When the input voltage decreases toward the
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
Application Information
Figure 2 below shows the basic application
circuit with BL3406B fixed output versions.
2.7V - 4.2V
VIN
4
C1
4.7uF
SW
VIN
3
L1
2.2 µH
VOUT 1.8V
C2
10uF
BL3406B-18
1
VOUT 5
Run
GND
2
Figure 2. Basic Application Circuit
with fixed output versions
Input Capacitor Selection
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:
R2
)
R1
Table 1—Resistor Selection vs.
Output Voltage Setting
VOUT
R1
R2
1.0V
180 kΩ(1%)
120 kΩ(1%)
1.2V
180 kΩ(1%)
180 kΩ(1%)
1.5V
180 kΩ(1%)
270 kΩ(1%)
1.8V
180 kΩ(1%)
360 kΩ(1%)
2.5V
158 kΩ(1%)
499 kΩ(1%)
3.3V
180 kΩ(1%)
810 kΩ(1%)
VOUT = 0.6V × (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:
∆I L =
V
1
VOUT (1 − OUT )
f ×L
VIN
A reasonable starting point for setting ripple
current is ∆IL=320mA (40% of 800mA). For
PPMIC BU
BL3406B Rev 1.5
10/2009
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. 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).
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 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
[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 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
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BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
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:
∆VOUT ≤

VOUT×(VIN −VOUT) 
1

× ESR+
VIN × fOSC× L 
8× fOSC×C2 
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:
2.7V - 4.2V
VIN
4
C1
4.7uF
SW
VIN
3
BL3406B-ADJ
1
VFB 5
Run
GND
2
L1
2.2 µH
VOUT 1.8V
C3
22pF
10/2009
VIN
4
C1
4.7uF
SW
VIN
3
L1
2.2 µH
BL3406B-18
1
R2
200k
R1
100k
VOUT 1.8V
C2
10uF
VOUT 5
Run
GND
2
Figure 4. BL3406B-1.8 Layout Circuit
Figure 5. BL3406B-ADJ Suggested Layout
BL3406B Rev 1.5
2.7V - 4.2V
C2
10uF
Figure 3. BL3406B-ADJ Layout Circuit
PPMIC BU
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 VFB node.
5. Keep the (-) plates of CIN and COUT as
close as possible.
Figure 6. BL3406B-1.8 Suggested Layout
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BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
Package Description
Symbol
A
A1
B
b
C
D
e
H
L
Dimensions In Millimeters
Min
0.889
0.000
1.397
0.356
2.591
2.692
0.838
0.080
0.300
Max
1.295
0.152
1.803
0.559
2.997
3.099
1.041
0.254
0.610
Dimensions In Inches
Min
0.035
0.000
0.055
0.014
0.102
0.106
0.033
0.003
0.012
Max
0.051
0.006
0.071
0.022
0.118
0.122
0.041
0.010
0.024
SOT-23-5 Surface Mount Package
PPMIC BU
BL3406B Rev 1.5
10/2009
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BL3406B
1.5 MHz, 800mA Synchronous Buck Converter
TSOT-23-5 Surface Mount Package
PPMIC BU
BL3406B Rev 1.5
10/2009
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©2009 Belling All Rights Reserved
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