FAIRCHILD FAN5331

FAN5331
1.6MHz Boost Converter with 20V Integrated FET Switch
Features
Description
■ 1.6MHz Switching Frequency
The FAN5331 is a general purpose, fixed-frequency boost converter designed to operate at high switching frequencies in
order to minimize switching noise measured at the battery terminal of hand-held communications equipment. Quiescent current in normal mode of operation as well as in shutdown mode
is designed to be minimal in order to extend battery life. Normal
mode of operation or shutdown mode can be selected by a logic
level shutdown circuitry.
■ Low Noise
■ Low RDS(ON): 0.5Ω
■ Adjustable Output Voltage
■ 1A Peak Switch Current
■ Low Shutdown Current: <1µA
■ Cycle-by-Cycle Current Limit
■ Over-Voltage Protection
The low ON-resistance of the internal N-channel switch ensures
high efficiency and low power dissipation. A cycle-by-cycle current limit circuit keeps the peak current of the switch below a
maximum value of 1A. The FAN5331 is available in a 5-lead
SOT-23 package.
■ Fixed -Frequency PWM Operation
■ Internal Compensation
■ 5-lead SOT-23 Package
Applications
■ Cell Phones
■ PDAs
■ Handheld Equipment
■ Display Bias
■ LED Bias
Typical Application
BAT54
L
2.7V to 5.5V
VIN
VOUT
10µH
CIN
COUT
4.7µF
4.7µF
5
SW
FAN5331
VIN
FB
R1
1
CF
120pF
3
R2
4
ON
OFF
SHDN
GND
2
Figure 1. Typical Application Diagram
©2004 Fairchild Semiconductor Corporation
FAN5331 Rev. 1.0.1
1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
October 2004
Top View
SW
VIN
GND
FB
SHDN
5-Lead SOT-23
Figure 2. Pin Assignment
Pin Description
Pin No.
Pin Name
1
SW
2
GND
3
FB
4
SHDN
5
VIN
Pin Description
Switching node.
Analog and power ground.
Feedback node that connects to an external voltage divider.
Shutdown control pin. Logic HIGH enables, logic LOW disables the device.
Input voltage.
Absolute Maximum Ratings (Note1)
Parameter
Min
VIN to GND
Max
Unit
6.0
V
FB, SHDN to GND
-0.3
VIN + 0.3
V
SW to GND
-0.3
23
V
Lead Soldering Temperature (10 seconds)
300
°C
Junction Temperature
150
°C
Storage Temperature
-55
Thermal Resistance (ΘJA)
Electrostatic Discharge Protection (ESD) Level (Note 2)
HBM
2.5
CDM
1
Min
Typ
150
°C
265
°C/W
kV
Recommended Operating Conditions
Parameter
Input Voltage
2.7
Output Voltage
VIN
Operating Ambient Temperature
-40
Output Capacitance (Note 3)
1.6
25
Max
Unit
5.5
V
20
V
85
°C
µF
Notes:
1. Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This
is a stress rating only and functional operation of the device at these or any other conditions above those indicated
in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in combination.
2. Using EIA/JESD22A114B (Human Body Model) and EIA/JESD22C101-A (Charge Device Model).
3. This load capacitance value is required for the loop stability. Tolerance, temperature variation, and voltage
dependency of the capacitance must be considered. Typically a 4.7µF ceramic capacitor is required to achieve
specified value at VOUT = 15V.
2
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Pin Assignment
Unless otherwise noted, VIN = 3.6V, TA = -40°C to +85°C, Typical values are at TA = 25°C, Test Circuit,
Figure 3.
Parameter
Conditions
Min.
Typ.
1
Max.
Units
Switch Current Limit
VIN = 3.2V
0.7
Load Current
VOUT = 15V, V IN ≥ 2.7V
35
mA
VOUT = 15V, V IN ≥ 3.2V
50
mA
Switch On-resistance
Quiescent Current
OFF Mode Current
Shutdown Threshold
A
VIN = 5V
0.5
Ω
VIN = 3.6V
0.7
Ω
VSHDN = 3.6V, No Switching
0.7
VSHDN = 3.6V, Switching
1.6
3.0
mA
VSHDN = 0V
0.1
2
µA
0.5
V
Device ON
mA
1.5
V
Device OFF
Shutdown Pin Bias Current
VSHDN = 0V or VSHDN = 5.5V
Feedback Voltage
ILoad = 0mA
10
1.205
nA
1.230
Feedback Pin Bias Current
1.255
10
Feedback Voltage Line Regulation
2.7V < VIN < 5.5V, ILOAD = 0mA
V
nA
0.6
1.2
%
Switching Frequency
1.15
1.6
1.85
MHz
Maximum Duty Cycle
87
93
%
Enable Delay
VIN = 2.7V, IOUT = 35mA, VOUT = 15V
0.8
5
mS
Power on Delay
VIN = 2.7V, IOUT = 35mA, VOUT = 15V
0.8
5
mS
Switch Leakage Current
No Switching, VIN = 5.5V
1
µA
Test Circuit
BAT54
L
2.7V to 5.5V
VIN
VOUT
10µH
CIN
COUT
4.7µF
4.7µF
5
SW
V
1
R1
150KΩ
120pF
FAN5331
IN
4
ON
FB
3
R2
SHDN
CF
GND
2
13.4KΩ
OFF
Figure 3. Test Circuit
3
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Electrical Characteristics
TA = 25°C, Test Circuit Figure 3, unless otherwise noted.
Maximum Load Current vs Input Voltage
Output Voltage vs Input Voltage
Maximum Load Current (mA)
Output Voltage (V)
14.98
14.96
14.94
14.92
VIN(V)
VIN(V)
VIN(V)
VIN(V)
VIN(V)
VIN(V)
14.90
14.88
vs
vs
vs
vs
vs
vs
VOUT(V) at Iload=0mA
VOUT(V), at load=10mA
VOUT(V), at load=20mA
VOUT(V) at Iload=30mA
VOUT(V) at Iload=40mA
VOUT(V) at Iload=50mA
14.86
2.5
3.0
3.5
4.0
4.5
5.0
5.5
350
300
250
200
UT
=
V
12
UT
VO
VO
150
=
T
V
15
1V
=2
VOU
100
50
0
6.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Input Voltage (V)
Efficiency vs Input Voltage
Feedback Voltage vs Ambient Temperature
0.92
1.25
0.90
Feedback Voltage (V)
0.88
0.86
Efficiency
0.84
0.82
0.80
0.78
VIN(V)
VIN(V)
VIN(V)
VIN(V)
VIN(V)
0.76
0.74
vs
vs
vs
vs
vs
Efficiency
Efficiency
Efficiency
Efficiency
Efficiency
at
at
at
at
at
Iload
Iload
Iload
Iload
Iload
=10mA
=20mA
=30mA
=40mA
=50mA
1.24
1.23
1.22
3.0
3.5
4.0
4.5
5.0
5.5
Temperature (°C) vs Vf (Vin=2.7V, Iload=15m A)
Temperature (°C) vs Vf (Vin=3.6V, Iload=15m A)
Temperature (°C) vs Vf (Vin=5.5V, Iload=15m A)
1.21
0.72
2.5
IOUT = 15mA
-50
6.0
0
Input Voltage (V)
50
100
150
Ambient Temperature (ºC)
Supply Current vs Input Voltage
Switching Frequency vs Ambient Temperature
Switching Frequency (MHz)
Supply Current (mA)
3.0
IOUT = 0mA
2.5
2.0
Switching
1.5
Non Switching
1.0
0.5
0.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
1.6
1.4
1.2
1.0
-40
6.0
Input Voltage (V)
-20
0
20
40
60
80
100
120
140
Ambient Temperature (ºC)
4
FAN5331 Rev. 1.0.1
IOUT = 15mA
VOUT = 15V
VIN = 3.6V
1.8
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Typical Performance Characteristics
TA = 25°C, Test Circuit Figure 3, unless otherwise noted.
Startup After Enable
Line Transient Response
IOUT = 30mA
Tr = Tf = 10µS
VOUT = 15V
Inductor Current= 0mA
Time (200µs/div)
VIN = 3.2V
+0.6V
-0.6V
Time (100µs/div)
Load Transient Response
Output Power Spectral Density
(100mV/Div)
(10mA/Div)
VIN = 4.2V
Output Voltage
(200mA/div)
(5V/div)
Input Voltage
RL = 300Ω
VIN = 3V
VOUT = 15V
VIN = 3.6V
IOUT = 35mA
Tr = Tr = <1µS
VOUT = 15V
IOUT = 0 to 35mA
Time (20µs/div)
5
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Typical Performance Characteristics (Contd.)
VIN
5
SHDN
4
Shutdown
Circuitry
FB
SW
1
+
Comp
-
1.15 x VREF
Thermal
Shutdown
R
FB 3
-
Error
Amp
+
S
+
Comp
-
R
Current Limit
Comparator
-
Ramp
Generator
Q
R
n
Driver
S
+
Oscillator
+
Amp
Reference
0.05
Soft-Start
2
GND
Figure 4. Block Diagram
Circuit Description
reset by other events as well. Over-current condition is monitored by the current limit comparator which resets the latch and
turns off the switch instantaneously within each clock cycle.
Over-voltage condition is detected by a fast comparator limiting
the duty cycle in a similar manner to over-current monitoring
described above.
The FAN5331 is a pulse-width modulated (PWM) current-mode
boost converter. The FAN5331 improves the performance of battery powered equipment by significantly minimizing the spectral
distribution of noise at the input caused by the switching action of
the regulator. In order to facilitate effective noise filtering, the
switching frequency was chosen to be high, 1.6MHz. An internal
soft start circuitry minimizes in-rush currents. The timing of the soft
start circuit was chosen to reach 95% of the nominal output voltage
within maximum 5mS following an enable command when VIN =
2.7V, VOUT = 15V, ILOAD = 35mA and COUT (EFFECTIVE) = 3.2µF.
Applications Information
Setting the Output Voltage
The internal reference is 1.23V (Typical). The output voltage is
divided by a resistor divider, R1 and R2 to the FB pin. The output voltage is given by
The device architecture is that of a current mode controller with
an internal sense resistor connected in series with the N-channel switch. The voltage at the feedback pin tracks the output
voltage at the cathode of the external Schottky diode (shown in
the test circuit). The error amplifier amplifies the difference
between the feedback voltage and the internal bandgap reference. The amplified error voltage serves as a reference voltage
to the PWM comparator. The inverting input of the PWM comparator consists of the sum of two components: the amplified
control signal received from the 50mΩ current sense resistor
and the ramp generator voltage derived from the oscillator. The
oscillator sets the latch, and the latch turns on the FET switch.
Under normal operating conditions, the PWM comparator resets
the latch and turns off the FET, thus terminating the pulse. Since
the comparator input contains information about the output voltage and the control loop is arranged to form a negative feedback loop, the value of the peak inductor current will be adjusted
to maintain regulation.
R
V OUT = V REF  1 + ------1-

R 
2
According to this equation, and assuming desired output voltage of 15V, good choices for the feedback resistors are,
R1=150kΩ and R2=13.4kΩ.
Inductor Selection
The inductor parameters directly related to device performances
are saturation current and dc resistance. The FAN5331 operates with a typical inductor value of 10µH. The lower the dc
resistance, the higher the efficiency. Usually a trade-off between
inductor size, cost and overall efficiency is needed to make the
optimum choice.
The inductor saturation current should be rated around 1A,
which is the threshold of the internal current limit circuit. This
limit is reached only during the start-up and with heavy load
condition; when this event occurs the converter can shift over in
Every time the latch is reset, the FET is turned off and the current flow through the switch is terminated. The latch can be
6
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Block Diagram
Some recommended inductors are suggested in the table
below:
Inductor
Value
Vendor
Part Number
Comment
10µH
Panasonic
ELL6GM100M
Lower Profile
(1.6mm)
10µH
Murata
LQS66SN100M03L
Highest
Efficiency
10µH
Coilcraft
DO1605T-103Mx
Small Size
Table 1: Recommended Inductors
Figure 5. Recommended Layout
Capacitors Selection
Application Examples
For best performance, low ESR input and output capacitors are
required. Ceramic capacitors in the range 4.7µF to 10µF, placed
as close to the IC pins, are recommended for the lower input
and output ripple. The output capacitor voltage rating should be
according to the VOUT setting.
1. LED Driver
One or more serial LED strings can be driven with a constant
current, set by the series resistor, given by
1.23V
I LED = ---------------R1
A feed forward capacitor CF, is required for stability. The recommended value (R1 x CF) is around 18µS. Some capacitors are
suggested in the table below.
Capacitor
Value
Vendor
Part Number
4.7µF
Panasonic
ECJ3YB1C475K
4.7µF
Murata
GRM31CR61C475
BAT54
L
2.7V to 5.5V
VIN
10µH
CIN
VOUT
COUT
4.7µF
4.7µF
5
SW
V
1
IN
FAN5331
Table 2: Recommended Capacitors
Diode Selection
The external diode used for rectification is usually a Schottky
diode. Its average forward current and reverse voltage maximum ratings should exceed the load current and the voltage at
the output of the converter respectively. A barrier Schottky diode
such as BAT54 is preferred, due to its lower reverse current over
the temperature range.
4
ON
OFF
GND
SHDN
R1
2
R2
Figure 6. Low Noise Boost LED Driver
Care should be taken to avoid any short circuit of VOUT to GND,
even with the IC disabled, since the diode can be instantly damaged by the excessive current.
LED Current vs Input Voltage
(String Connected to FB Pin)
Thermal Shutdown
When the die temperature exceeds 150°C, a reset occurs and
will remain in effect until the die cools to 130°C, at that time the
circuit will be allowed to restart.
LED Current (mA)
20.2
PCB Layout Recommendations
The inherently high peak currents and switching frequency of
power supplies require careful PCB layout design. Therefore,
use wide traces for high current paths and place the input
capacitor, the inductor, and the output capacitor as close as
possible to the integrated circuit terminals. The resistor divider
that sets the output voltage should be routed away from the
inductor to avoid RF coupling. A four layer PCB with at least one
20.1
20.0
19.9
19.8
19.7
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
7
FAN5331 Rev. 1.0.1
3
FB
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
ground plane connected to the pin 2 of the IC is recommended.
This ground plane acts as an electromagnetic shield to reduce
EMI and parasitic coupling between components.
discontinuous conduction mode due to the automatic turn-off of
the switching transistor, resulting in higher ripple and reduced
efficiency.
While the feedback loop tightly regulates VOUT, the negative output voltage (-VOUT) can supply a light load with a negative voltage. Nevertheless, the negative voltage depends on the
changes of the load current in both -VOUT and +VOUT, as shown
in the graph below.
A Zener diode (VZ = 22V) connected between VOUT and GND
can prevent the FAN5331 from being damaged by over-voltage,
if the load is accidently disconnected during operation.
Negative Output Voltage vs Load Current
-18
Negative Output Voltage (V)
2. Dual Boost Converter
A negative voltage can be provided by adding an external
charge pump (C1, C2, D2, and D3).
BAT54S D2
C1
0.1µF
IOUT = 10mA
4.7µF
BAT54
L
2.7V to 5.5V
VIN
-VOUT
C2
D3
VOUT
10µH
CIN
COUT I
OUT = 50mA
D1
4.7µF
4.7µF
5
SW
V
1
R1
FAN5331
4
ON
OFF
FB
-15V/10mA Load
-14
-12
-10
CF
0
120pF
IN
-15V/Unloaded
-16
10
20
30
40
50
Load Current On Positive Output Side (mA)
3
R2
SHDN
GND
2
Figure 7. Dual (±) Boost Converter
8
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
The feedback loop tightly regulates the current in the branch
connected to FB pin, while the current in the other branch
depends on the sum of the LED’s forward voltages, VOUT and
the ballast resistor. The input and the output ripple is less than
3mVRMS, for load currents up to 40mA.
FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
Mechanical Dimensions
5-Lead SOT-23Package
B
L
c
e
E
H
e1
D
A
A1
Symbol
Inches
Min
Millimeters
Max
Min
Max
A
.035
.057
.90
1.45
A1
.000
.006
.00
.15
B
.008
.020
.20
.50
c
.003
.010
.08
.25
D
.106
.122
2.70
3.10
E
.059
.071
1.50
1.80
e
.037 BSC
.95 BSC
e1
.075 BSC
1.90 BSC
H
.087
.126
2.20
3.20
L
.004
.024
.10
.60
α
0º
10º
0º
10º
Notes
Ordering Information
Product Number
Package Type
Order Code
FAN5331
5-Lead SOT23
FAN5331SX
9
FAN5331 Rev. 1.0.1
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support device or system, or to affect its safety or
failure to perform when properly used in accordance
with instructions for use provided in the labeling, can be
effectiveness.
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user.
PRODUCT STATUS DEFINITIONS
Definition of Terms
Datasheet Identification
Product Status
Definition
Advance Information
Formative or
In Design
This datasheet contains the design specifications for
product development. Specifications may change in
any manner without notice.
Preliminary
First Production
This datasheet contains preliminary data, and
supplementary data will be published at a later date.
Fairchild Semiconductor reserves the right to make
changes at any time without notice in order to improve
design.
No Identification Needed
Full Production
This datasheet contains final specifications. Fairchild
Semiconductor reserves the right to make changes at
any time without notice in order to improve design.
Obsolete
Not In Production
This datasheet contains specifications on a product
that has been discontinued by Fairchild semiconductor.
The datasheet is printed for reference information only.
Rev. I7
10
FAN5331 Rev. 1.0.1
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FAN5331 1.6MHz Boost Converter with 20V Integrated FET Switch
TRADEMARKS