FAN5354 — 3MHz, 3A Synchronous Buck Regulator
March 2011
FAN5354
3MHz, 3A Synchronous Buck Regulator
Features
3MHz Fixed-Frequency Operation
Best-in-Class Load Transient
3A Output Current Capability
2.7V to 5.5V Input Voltage Range
Adjustable Output Voltage: 0.8 to V
IN
•0.9
PFM Mode for High Efficiency in Light Load (Forced PWM
Available on MODE Pin)
Minimum PFM Frequency Avoids Audible Noise
270 A Typical Quiescent Current in PFM Mode
External Frequency Synchronization
Low Ripple Light-Load PFM Mode with Forced
PWM Control
Power Good Output
Internal Soft-Start
Input Under-Voltage Lockout (UVLO)
Thermal Shutdown and Overload Protection
12-Lead 3x3.5mm MLP
Description
The FAN5354 is a step-down switching voltage regulator that
delivers an adjustable output from an input voltage supply of
2.7V to 5.5V. Using a proprietary architecture with
synchronous rectification, the FAN5354 is capable of
delivering 3A at over 85% efficiency, while maintaining a
very high efficiency of over 80% at load currents as low as
2mA. The regulator operates at a nominal fixed frequency of
3MHz, which reduces the value of the external components
to 470nH for the output inductor and 10 F for the output
capacitor. Additional output capacitance can be added to
improve regulation during load transients without affecting
stability and inductance up to 1.2 H may be used with
additional output capacitance.
At moderate and light loads, pulse frequency modulation
(PFM) is used to operate the device in power-save mode
with a typical quiescent current of 270 A. Even with such a
low quiescent current, the part exhibits excellent transient
response during large load swings. At higher loads, the
system automatically switches to fixed-frequency control,
operating at 3MHz. In shutdown mode, the supply current
drops below 1 A, reducing power consumption. PFM mode
can be disabled if constant frequency is desired. To avoid
audible noise, the regulator limits its minimum PFM
frequency. The FAN5354 is available in 12-lead 3x3.5mm
MLP package.
Applications
Set-Top Box
Hard Disk Drive
Communications Cards
DSP Power
Figure 1. Typical Application
Ordering Information
Part Number
FAN5354MPX
Temperature Range
-40 to 85°C
Package
MLP-12, 3x3.5mm
Packing Method
Tape and Reel
© 2009 Fairchild Semiconductor Corporation
FAN5354 • Rev. 1.0.5
www.fairchildsemi.com
FAN5354 — 3MHz, 3A Synchronous Buck Regulator
Table 1. Recommended External Components for 3A Maximum Load Current
Component
Description
Vendor
IHLP1616ABER47M01 (Vishay)
SD12-R47-R (Coiltronics)
VLC5020T-R47N (TDK)
(TDK)
LQH55PNR47NT0 (Murata)
GRM21BR60J106M (Murata)
C2012X5R0J106M (TDK)
GRM155R71E103K (Murata)
C1005X7R1E103K (TDK)
GRM188R60J475K (Murata)
C1608X5R0J475K (TDK)
Any
Parameter
L
DCR
Typ.
0.47
20
Units
µH
mΩ
L1
470nH Nominal
C
OUT
C
IN
C
IN1
C
VCC
R3
(1)
2 Pieces
10µF, 6.3V, X5R, 0805
10µF, 6.3V, X5R, 0805
10nF, 25V, X7R, 0402
4.7µF, 6.3V, X5R, 0603
Resistor: 1Ω 0402
C
10.0
µF
C
C
R
10
4.7
1
nF
µF
Ω
Note:
1. R3 is optional and improves IC power supply noise rejection.
See Layout recommendations for more information.
Pin Configuration
FB 1
VOUT 2
PGND 3
PGND 4
SW 5
SW 6
P1
(GND)
12 MODE
11 PGOOD
10 EN
9 VCC
8 PVIN
7 PVIN
Figure 2. 12-Pin, 3x3.5mm MLP (Top View)
Pin Definitions
Pin #
1
2
3, 4
5, 6
P1
7, 8
9
10
11
12
Name
FB
VOUT
PGND
SW
GND
PVIN
VCC
EN
PGOOD
MODE
Description
FB.
Connect to resistor divider. The IC regulates this pin to 0.8V.
VOUT.
Sense pin for VOUT. Connect to COUT.
Power Ground.
Low-side MOSFET is referenced to this pin. CIN and COUT should be returned with a
minimal path to these pins.
Switching Node.
Connect to inductor.
Ground.
All signals are referenced to this pin.
Power Input Voltage.
Connect to input power source. Connect to CIN with minimal path.
IC Bias Supply.
Connect to input power source. Use a separate bypass capacitor CVCC from this pin
to the P1 GND terminal between pins 1 and 12.
Enable.
The device is in shutdown mode when this pin is LOW. Do not leave this pin floating.
Power Good.
This open-drain pin pulls LOW if the output falls out of regulation or is in soft-start.
MODE / Sync.
A logic 0 allows the IC to automatically switch to PFM during light loads. When held
HIGH, the IC to stays in PWM mode. The regulator also synchronizes its switching frequency to the
frequency provided on this pin. Do not leave this pin floating.
Note:
2. P1 is the bottom heat-sink pad. Ground plane should flow through pins 3, 4, and P1 and can be extended through pin 11 if
PGOOD’s function is not required, and through pin 12 if MODE is to be grounded, to improve IC cooling.
© 2009 Fairchild Semiconductor Corporation
FAN5354 • Rev. 1.0.5
www.fairchildsemi.com
2
FAN5354 — 3MHz, 3A Synchronous Buck Regulator
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above
the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended
exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum
ratings are stress ratings only.
Symbol Parameter
V
IN
SW, PVIN, VCC Pins
Other Pins
V
INOV_SLEW
Maximum Slew Rate of VIN Above 6.5V when PWM is Switching
R
PGOOD
ESD
T
J
T
STG
T
L
Pull-Up Resistance from PGOOD to VCC
Electrostatic Discharge
Protection Level
Junction Temperature
Storage Temperature
Lead Soldering Temperature, 10 Seconds
Human Body Model per JESD22-A114
Charged Device Model per JESD22-C101
IC Not Switching
IC Switching
Min.
-0.3
-0.3
-0.3
1
2
2
–40
–65
Max.
7.0
6.5
V
CC
+ 0.3
15
(3)
Units
V
V
V/ms
KΩ
KV
+150
+150
+260
°C
°C
°C
Note:
3. Lesser of 7V or V
CC
+0.3V.
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating
conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend
exceeding them or designing to Absolute Maximum Ratings.
Symbol
V
CC,
V
IN
V
OUT
I
OUT
L
C
IN
C
OUT
T
A
T
J
Parameter
Supply Voltage Range
Output Voltage Range
Output Current
Inductor
Input Capacitor
Output Capacitor
Operating Ambient Temperature
Operating Junction Temperature
Min.
2.7
0.8
0
Typ.
Max.
5.5
90% Duty Cycle
3
Units
V
V
A
H
F
F
0.47
10
20
-40
-40
+85
+125
°C
°C
Thermal Properties
Symbol
θ
JA
Parameter
Junction-to-Ambient Thermal Resistance
(4)
Min.
Typ.
46
Max.
Units
°C/W
Note:
4. Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with four-layer
1s2p boards in accordance to JESD51- JEDEC standard. Special attention must be paid not to exceed junction
temperature T
J(max)
at a given ambient temperate T
A
.
© 2009 Fairchild Semiconductor Corporation
FAN5354 • Rev. 1.0.5
www.fairchildsemi.com
3
FAN5354 — 3MHz, 3A Synchronous Buck Regulator
Electrical Characteristics
Minimum and maximum values are at V
IN
=2.7V to 5.5V, T
A
=-40°C to +85°C, unless otherwise noted. Typical values are at
T
A
=25°C, V
IN
=5V.
Symbol Parameter
Power Supplies
I
Q
I
SD
V
UVLO
Quiescent Current
Shutdown Supply Current
Under-Voltage Lockout Threshold
Conditions
I
LOAD
=0, MODE=0
I
LOAD
=0, MODE=1 (Forced PWM)
EN=GND
V
IN
Rising
V
IN
Falling
Min. Typ. Max. Units
270
14
0.1
2.83
2.10
2.30
530
1.05
0.4
100
3.0
2.95
2.40
µA
mA
µA
V
V
mV
V
V
mV
1.00
1
0.01
1.00
µA
mA
µA
V
V
%
%/A
%/V
mV
m
m
5.50
A
°C
°C
V
V
3.3
3.3
36
250
420
MHz
MHz
kHz
µs
µs
V/ms
V
UVHYST
Under-Voltage Lockout Hysteresis
Logic Pins
V
IH
V
IL
V
LHYST
I
IN
I
OUTL
I
OUTH
HIGH-Level Input Voltage
LOW-Level Input Voltage
Logic Input Hysteresis Voltage
Input Bias Current
PGOOD Pull-Down Current
PGOOD HIGH Leakage Current
Input Tied to GND or V
IN
V
PGOOD
=0.4V
V
PGOOD
=V
IN
T
A
=25°C
At V
OUT
Pin W.R.T. Calculated Value,
I
LOAD
=500mA
I
OUT(DC)
=1 to 3A
2.7V ≤ V
IN
≤ 5.5V, I
OUT(DC)
=1.5A
I
LOAD
Step 0.1A to 1.5A, t
r
=t
f
=100ns, V
OUT
=1.2V
0.01
V
OUT
Regulation
V
REF
V
REG
∆
V
OUT
∆
I
LOAD
∆
V
OUT
∆
V
IN
Output Reference DC Accuracy
Measured at FB Pin
V
OUT
DC Accuracy
Load Regulation
Line Regulation
Transient Response
0.792 0.800 0.808
0.788 0.800 0.812
1.6
–0.03
0.01
+40
60
40
3.75
4.55
150
20
+1.6
Power Switch and Protection
R
DS(ON)P
P-Channel MOSFET On Resistance
R
DS(ON)N
N-Channel MOSFET On Resistance
I
LIMPK
T
LIMIT
T
HYST
V
SDWN
P-MOS Peak Current Limit
Thermal Shutdown
Thermal Shutdown Hysteresis
Input OVP Shutdown
Rising Threshold
Falling Threshold
5.50
2.7
External Square-Wave, 30% to 70% Duty Cycle
T
A
= 25°C, V
IN
= 5.0V
R
LOAD
> 5Ω, to V
OUT
=1.2V
R
LOAD
> 5Ω, to V
OUT
=1.8V
2.7
17
6.2
5.85
3.0
3.0
26
210
340
10
Frequency Control
f
SW
f
SYNC
Soft-Start
t
SS
V
SLEW
Regulator Enable to Regulated V
OUT
Soft-Start V
REF
Slew Rate
Oscillator Frequency
MODE Pin Synchronization Range
f
PFM(MIN)
Minimum PFM Frequency
© 2009 Fairchild Semiconductor Corporation
FAN5354 • Rev. 1.0.5
www.fairchildsemi.com
4
FAN5354 — 3MHz, 3A Synchronous Buck Regulator
Typical Characteristics
Unless otherwise specified, V
IN
=5V, V
OUT
=1.2V, circuit of Figure 1, and components per Table 1.
100%
90%
80%
70%
Efficiency
Efficiency
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
VIN = 3.3V, Mode = 0
VIN = 3.3V, Mode = 1
VIN = 5V, Mode = 0
VIN = 5V, Mode = 1
60%
50%
40%
30%
20%
10%
0%
1
10
100
1000
10000
I
LOAD
Output Current (mA)
VIN = 3.3V, Mode=0
VIN = 3.3V, Mode=1
VIN = 5V, Mode=0
VIN = 5V, Mode=1
1
10
100
1000
10000
I
LOAD
Output Current (mA)
Figure 3. Efficiency vs. I
LOAD
at V
OUT
=1.2V
Figure 4. Efficiency vs. I
LOAD
at V
OUT
=1.8V
100%
90%
80%
70%
Efficiency
60%
50%
40%
30%
20%
10%
0%
1
10
100
1000
10000
I
LOAD
Output Current (mA)
VIN = 3.3V, Mode = 0
VIN = 3.3V, Mode = 1
VIN = 5V, Mode = 0
VIN = 5V, Mode = 1
100%
90%
80%
70%
Efficiency
60%
50%
40%
30%
20%
10%
0%
1
10
100
1000
10000
I
LOAD
Output Current (mA)
VIN = 4.2V, Mode = 0
VIN = 4.2V, Mode = 1
VIN = 5V, Mode = 0
VIN = 5V, Mode = 1
Figure 5. Efficiency vs. I
LOAD
at V
OUT
=2.5V
Figure 6. Efficiency vs. I
LOAD
at V
OUT
=3.3V
1
PFM, No load supply Current( A)
400
375
350
VOUT = 3.3
0.9
0.8
Supply Current (
µ
A)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2.7
3.2
3.7
4.2
Input Voltage(V)
4.7
5.2
85°C
25°C
-40°C
325
300
VOUT = 1.2
275
250
225
200
2.7
3.2
3.7
4.2
4.7
5.2
85°C
25°C
–40°C
Input Voltage(V)
Figure 7. Shutdown Supply Current vs V
IN
, EN=0
Figure 8. Quiescent Current in PFM vs. V
IN
, No Load
© 2009 Fairchild Semiconductor Corporation
FAN5354 • Rev. 1.0.5
www.fairchildsemi.com
5
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