Fairchild FAN53611UC123X 6 mhz 600 ma / 1 a synchronous buck regulator Datasheet

FAN53601 / FAN53611
6 MHz 600 mA / 1 A Synchronous Buck Regulator
Features
 600 mA or 1 A Output Current Capability
 24 µA Typical Quiescent Current
 6 MHz Fixed-Frequency Operation
 Best-in-Class Load Transient Response
 Best-in-Class Efficiency
 2.3 V to 5.5 V Input Voltage Range
 0.8 V to 2 V Fixed Output Voltage
 Low Ripple Light-Load PFM Mode
 Forced PWM and External Clock Synchronization
 Internal Soft-Start
 Input Under-Voltage Lockout (UVLO)
 Thermal Shutdown and Overload Protection
 Optional Output Discharge
 6-Bump WLCSP, 0.4 mm Pitch
Applications
 6-Bump WLCSP, 0.4mm Pitch
 3G, 4G, WiFi®, WiMAX™, and WiBro® Data Cards
 Tablets
 DSC, DVC
 Netbooks®, Ultra-Mobile PCs
Description
The FAN53601/11 is a 6 MHz, step-down switching voltage
regulator, available in 600 mA or 1 A options, that delivers a
fixed output from an input voltage supply of 2.3 V to 5.5 V.
Using a proprietary architecture with synchronous
rectification, the FAN53601/11 is capable of delivering a
peak efficiency of 92%, while maintaining efficiency over
80% at load currents as low as 1 mA.
The regulator operates at a nominal fixed frequency of
6 MHz, which reduces the value of the external components
to as low as 470 nH for the output inductor and 4.7 µF for the
output capacitor. In addition, the Pulse Width Modulation
(PWM) modulator can be synchronized to an external
frequency source.
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 24 µA. 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 6 MHz. In Shutdown Mode, the supply current
drops below 1 µA, reducing power consumption. For
applications that require minimum ripple or fixed frequency,
PFM Mode can be disabled using the MODE pin.
The FAN53601/11 is available in 6-bump, 0.4 mm pitch,
Wafer-Level Chip-Scale Package (WLCSP).
MODE
L1
SW
470nH
FB
F
All trademarks are the property of their respective owners.
A1
A2
B1
B2
C1
C2
VIN
CIN
2.2 F
EN
GND
COUT
Figure 1. Typical Application
Ordering Information
Output
Voltage(1)
Max. Output
Current
Active
Discharge(2)
FAN53611AUC11X
1.100 V
1A
Yes
FAN53611UC123X
1.233 V
1A
No
FAN53601UC182X
1.820 V
600 mA
No
Part Number
Package
Temperature
Range
Packing
WLCSP-6,
0.4 mm Pitch
–40 to +85°C
Tape and
Reel
Notes:
1. Other voltage options available on request. Contact a Fairchild representative.
2. All voltage and output current options are available with or without active discharge. Contact a Fairchild representative.
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
October 2012
Figure 2. Bumps Facing Down
Figure 3. Bumps Facing Up
Pin Definitions
Pin #
Name
Description
A1
MODE
B1
SW
Switching Node. Connect to output inductor.
C1
FB
Feedback / VOUT. Connect to output voltage.
C2
GND
MODE. Logic 1 on this pin forces the IC to stay in PWM Mode. A logic 0 allows the IC to
automatically switch to PFM during light loads. The regulator also synchronizes its switching
frequency to four times the frequency provided on this pin. Do not leave this pin floating.
Ground. Power and IC ground. All signals are referenced to this pin.
B2
EN
Enable. The device is in Shutdown Mode when voltage to this pin is < 0.4 V and enabled when
> 1.2 V. Do not leave this pin floating.
A2
VIN
Input Voltage. Connect to input power source.
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
2
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Pin Configurations
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
VIN
VSW
VCTRL
Parameter
Input Voltage
Min.
Max.
–0.3
7.0
Units
V
(3)
Voltage on SW Pin
–0.3
VIN + 0.3
V
EN and MODE Pin Voltage
–0.3
VIN + 0.3(3)
V
–0.3
(3)
V
Other Pins
VIN + 0.3
Human Body Model per JESD22-A114
3.5
Charged Device Model per JESD22-C101
1.5
ESD
Electrostatic Discharge
Protection Level
TJ
Junction Temperature
–40
+150
°C
TSTG
Storage Temperature
–65
+150
°C
+260
°C
TL
Lead Soldering Temperature, 10 Seconds
kV
Note:
3. Lesser of 7 V or VIN+0.3 V.
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
VCC
IOUT
L
CIN
COUT
Parameter
Min.
Max.
Units
2.3
5.5
V
Output Current for FAN53601
0
600
mA
Output Current for FAN53611
0
1
A
Supply Voltage Range
Typ.
Inductor
470
nH
Input Capacitor
2.2
µF
Output Capacitor
1.6
TA
Operating Ambient Temperature
TJ
Operating Junction Temperature
4.7
12.0
μF
–40
+85
°C
–40
+125
°C
Thermal Properties
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 JEDEC standard JESD51. Special attention must be paid to not exceed junction temperature TJ(max) at a
given ambient temperate TA.
Symbol
JA
Parameter
Junction-to-Ambient Thermal Resistance
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
Typical
Unit
150
°C/W
www.fairchildsemi.com
3
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Absolute Maximum Ratings
Minimum and maximum values are at VIN = VEN = 2.3 V to 5.5 V, VMODE = 0 V (AUTO Mode), TA = -40°C to +85°C; circuit of
Figure 1, unless otherwise noted. Typical values are at TA = 25°C, VIN = VEN = 3.6 V.
Symbol Parameter
Conditions
Min.
Typ.
Max.
Units
No Load, Not Switching
24
50
µA
PWM Mode
8
Shutdown Supply Current
EN = GND
0.25
1.00
µA
Under-Voltage Lockout Threshold
Rising VIN
2.15
2.27
V
Power Supplies
IQ
I(SD)
VUVLO
Quiescent Current
VUVHYST Under-Voltage Lockout Hysteresis
mA
200
mV
Logic Inputs: EN and MODE Pins
VIH
Enable HIGH-Level Input Voltage
VIL
Enable LOW-Level Input Voltage
VLHYST
Logic Input Hysteresis Voltage
IIN
Enable Input Leakage Current
1.2
V
0.4
100
Pin to VIN or GND
V
mV
0.01
1.00
µA
Switching and Synchronization
fSW
fSYNC
Switching Frequency(4)
VIN = 3.6 V, TA = 25°C
5.4
6.0
6.6
MHz
Square Wave at MODE Input
1.3
1.5
1.7
MHz
ILOAD = 0 to 1 A
1.207
1.233
1.272
PWM Mode
1.207
1.233
1.259
ILOAD = 0 to 1 A
1.784
1.820
1.875
PWM Mode
1.784
1.820
1.856
ILOAD = 0 to 1 A
1.075
1.100
1.136
PWM Mode
1.075
1.100
1.125
From EN Rising Edge
180
300
PMOS On Resistance
VIN = VGS = 3.6 V
175
m
NMOS On Resistance
VIN = VGS = 3.6 V
165
m
(4)
MODE Synchronization Range
Regulation
1.233 V
VO
Output Voltage
Accuracy
1.820 V
1.100 V
tSS
Soft-Start
V
µs
Output Driver
RDS(on)
ILIM(OL)
PMOS Peak Current Limit
Open-Loop for FAN53601
900
1100
1250
mA
Open-Loop for FAN53611
1500
1750
2000
mA
230

Thermal Shutdown
150
°C
Thermal Shutdown Hysteresis
15
°C
RDIS
Output Discharge Resistance
TTSD
THYS
EN = GND
Notes:
4. Limited by the effect of tOFF minimum (see Operation Description section).
5. The Electrical Characteristics table reflects open-loop data. Refer to the Operation Description and Typical Characteristics
Sections for closed-loop data.
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
4
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Electrical Characteristics
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25°C.
95%
85%
Efficiency
Efficiency
90%
80%
75%
2.7
3.6
4.2
5.0
70%
0
200
400
600
800
VIN
VIN
VIN
VIN
92%
90%
88%
86%
84%
82%
80%
78%
76%
74%
72%
70%
68%
66%
64%
62%
60%
1000
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
0
200
Load Current (mA)
800
1000
Figure 5. Efficiency vs. Load Current
and Temperature, Auto Mode, Dotted for FPWM
90%
90%
88%
88%
86%
86%
84%
84%
82%
82%
80%
80%
Efficiency
Efficiency
600
Load Current (mA)
Figure 4. Efficiency vs. Load Current and
Input Voltage, Auto Mode, Dotted for Decreasing Load
78%
76%
74%
78%
76%
74%
72%
70%
72%
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
68%
70%
2.7
3.6
4.2
5.0
68%
66%
64%
0
200
400
600
800
66%
VIN
VIN
VIN
VIN
64%
62%
60%
0
1000
200
Load Current (mA)
3
3
800
1000
2.7VIN, AUTO
3.6VIN, AUTO
4.2VIN, AUTO
5.0VIN, AUTO
2.7VIN, PWM
3.6VIN, PWM
4.2VIN, PWM
5.0VIN, PWM
2
Output Regulation (%)
1
600
Figure 7. Efficiency vs. Load Current
and Temperature, VOUT=1.23 V, Auto Mode,
Dotted for FPWM
2.7VIN, AUTO
3.6VIN, AUTO
4.2VIN, AUTO
5.0VIN, AUTO
2.7VIN, PWM
3.6VIN, PWM
4.2VIN, PWM
5.0VIN, PWM
2
400
Load Current (mA)
Figure 6. Efficiency vs. Load Current and
Input Voltage, VOUT = 1.23 V, Auto Mode, Dotted
for Decreasing Load
Output Regulation (%)
400
0
-1
-2
1
0
-1
-2
0
200
400
600
800
1000
0
Load Current (mA)
400
600
800
1000
Load Current (mA)
Figure 8. ∆VOUT (%) vs. Load Current and Input Voltage,
Normalized to 3.6 VIN, 500 mA Load, FPWM, Dotted for
Auto Mode
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
200
Figure 9. ∆VOUT (%) vs. Load Current and Input Voltage,
VOUT=1.23 V, Normalized to 3.6 VIN, 500 mA Load, FPWM,
Dotted for Auto Mode
www.fairchildsemi.com
5
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Typical Performance Characteristics
350
350
300
300
Load Current (mA)
Load Current (mA)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25°C.
250
200
150
100
250
200
150
100
PWM
PWM
PFM
50
2.5
3.0
3.5
4.0
4.5
5.0
PFM
50
5.5
2.5
3.0
Input Voltage (V)
15
5.0
5.5
- 40C
+25C
+85C
12
Input Current (mA)
Input Current (A)
4.5
Figure 11. PFM / PWM Boundary vs. Input Voltage,
VOUT=1.23 V
- 40C, EN=VIN
+25C, EN=VIN
+85C, EN=VIN
- 40C, EN=1.8V
+25C, EN=1.8V
+85C, EN=1.8V
30
4.0
Input Voltage (V)
Figure 10. PFM / PWM Boundary vs. Input Voltage
35
3.5
25
9
6
20
3
15
0
2.5
3.0
3.5
4.0
4.5
5.0
2.5
5.5
3.0
Input Voltage (V)
5.0
5.5
7,500
Switching Frequency (KHz)
Output Ripple (mVpp)
4.5
Figure 13. Quiescent Current vs. Input Voltage and
Temperature, Mode=EN=VIN (FPWM)
2.7VIN, AUTO
3.6VIN, AUTO
5.0VIN, AUTO
2.7VIN, PWM
3.6VIN, PWM
5.0VIN, PWM
20
4.0
Input Voltage (V)
Figure 12. Quiescent Current vs. Input Voltage and
Temperature, Auto Mode; EN=VIN Solid, Dotted for
o
o
o
EN=1.8 V (-40 C, +25 C, +85 C)
25
3.5
15
10
5
6,000
4,500
3,000
2.7VIN, AUTO
3.6VIN, AUTO
5.0VIN, AUTO
1,500
2.7VIN, PWM
3.6VIN, PWM
0
5.0VIN, PWM
0
0
200
400
600
800
1000
0
Load Current (mA)
400
600
800
1000
Load Current (mA)
Figure 14. Output Ripple vs. Load Current and
Input Voltage, FPWM, Dotted for Auto Mode
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
200
Figure 15. Frequency vs. Load Current and
Input Voltage, Auto Mode, Dotted for FPWM
www.fairchildsemi.com
6
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25°C.
Figure 16. Load Transient, 10-200-10 mA, 100 ns Edge
Figure 17. Load Transient, 200-800-200 mA, 100 ns Edge
Figure 18. Line Transient, 3.3-3.9-3.3 VIN, 10 µs Edge,
36 mA Load
Figure 19. Line Transient, 3.3-3.9-3.3 VIN, 10 µs Edge,
600 mA Load
Figure 20. Combined Line / Load Transient, 3.9-3.3 VIN,
10 µs Edge, 36-400 mA Load, 100 ns Edge
Figure 21. Combined Line / Load Transient, 3.3-3.9 VIN,
10 µs Edge, 400-36 mA Load, 100 ns Edge 3.9-3.3 VIN,
10 µs Edge
Figure 22. Startup, 50 Ω Load
Figure 23. Startup, 3 Ω Load
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
7
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25°C.
Figure 24. Shutdown, 10k Ω Load, No Output Discharge
Figure 25. Shutdown, No Load, Output Discharge Enabled
Figure 26. Over-Current, Load Increasing Past Current
Limit, FAN53601
Figure 27. 250 mΩ Fault, Rapid Fault, Hiccup, FAN53601
Figure 28. Over-Current, Load Increasing Past Current
Limit, FAN53611
Figure 29. 250 mΩ Fault, Rapid Fault, Hiccup, FAN53611
70
36mA Load
24mA Load
600mA Load
500mA Load
60
60
50
50
PSRR (dB)
PSRR (dB)
70
40
30
40
30
20
0.1
1
10
100
20
1000
0.1
Frequency (KHz)
10
100
1000
Frequency (KHz)
Figure 30. PSRR, 50 Ω and 3 Ω Load
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
1
Figure 31. PSRR, 50 Ω and 3 Ω Load, VOUT=1.23 V
www.fairchildsemi.com
8
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
The FAN53601/11 is a 6 MHz, step-down switching voltage
regulator available in 600 mA or 1 A options that delivers a
fixed output from an input voltage supply of 2.3 V to 5.5 V.
Using a proprietary architecture with synchronous
rectification, the FAN53601/11 is capable of delivering a
peak efficiency of 92%, while maintaining efficiency over
80% at load currents as low as 1 mA.
The current required to charge COUT during soft-start
commonly referred to as “displacement current” is given as:
IDISP  C OUT 
where
The regulator operates at a nominal fixed frequency of
6 MHz, which reduces the value of the external components
to as low as 470 nH for the output inductor and 4.7 µF for the
output capacitor. In addition, the PWM modulator can be
synchronized to an external frequency source.
(1)
dV
refers to the soft-start slew rate.
dt
To prevent shut down during soft-start, the following condition
must be met:
IDISP  ILOAD  IMAX(DC)
Control Scheme
(2)
where IMAX(DC) is the maximum load current the IC is
guaranteed to support.
The FAN53601/11 uses a proprietary, non-linear, fixedfrequency PWM modulator to deliver a fast load transient
response, while maintaining a constant switching frequency
over a wide range of operating conditions. The regulator
performance is independent of the output capacitor ESR,
allowing for the use of ceramic output capacitors. Although
this type of operation normally results in a switching frequency
that varies with input voltage and load current, an internal
frequency loop holds the switching frequency constant over a
large range of input voltages and load currents.
Startup into Large COUT
Multiple soft-start cycles are required for no-load startup if
COUT is greater than 15 F. Large COUT requires light initial
load to ensure the FAN53601/11 starts appropriately. The IC
shuts down for 1.3 ms when IDISP exceeds ILIMIT for more
than 200 s of current limit. The IC then begins a new softstart cycle. Since COUT retains its charge when the IC is off,
the IC reaches regulation after multiple soft-start attempts.
For very light loads, the FAN53601/11 operates in
discontinuous current (DCM) single-pulse PFM Mode, which
produces low output ripple compared with other PFM
architectures. Transition between PWM and PFM is
seamless, allowing for a smooth transition between DCM
and CCM.
MODE Pin
Logic 1 on this pin forces the IC to stay in PWM Mode. A
logic 0 allows the IC to automatically switch to PFM during
light loads. If the MODE pin is toggled with a frequency
between 1.3 MHz and 1.7 MHz, the converter synchronizes
its switching frequency to four times the frequency on the
MODE pin.
Combined
with
exceptional
transient
response
characteristics, the very low quiescent current of the
controller maintains high efficiency; even at very light loads;
while preserving fast transient response for applications
requiring tight output regulation.
The MODE pin is internally buffered with a Schmitt trigger,
which allows the MODE pin to be driven with slow rise and
fall times. An asymmetric duty cycle for frequency
synchronization is also permitted as long as the minimum
time below VIL(MAX) or above VIH(MAX) is 100 ns.
Enable and Soft-Start
When EN is LOW, all circuits are off and the IC draws ~50 nA
of current. When EN is HIGH and VIN is above its UVLO
threshold, the regulator begins a soft-start cycle. The output
ramp during soft-start is a fixed slew rate of 50 mV/s from 0
to 1 VOUT, then 12.5 mV/s until the output reaches its
setpoint. Regardless of the state of the MODE pin, PFM Mode
is enabled to prevent current from being discharged from COUT
if soft-start begins when COUT is charged.
Current Limit, Fault Shutdown, and Restart
A heavy load or short circuit on the output causes the current
in the inductor to increase until a maximum current threshold
is reached in the high-side switch. Upon reaching this point,
the high-side switch turns off, preventing high currents from
causing damage. The regulator continues to limit the current
cycle-by-cycle. After 16 cycles of current limit, the regulator
triggers an over-current fault, causing the regulator to shut
down for about 1.3 ms before attempting a restart.
In addition, all voltage options can be ordered with a feature
that actively discharges FB to ground through a 230  path
when EN is LOW. Raising EN above its threshold voltage
activates the part and starts the soft-start cycle. During softstart, the internal reference is ramped using an exponential
RC shape to prevent overshoot of the output voltage. Current
limiting minimizes inrush during soft-start.
If the fault is caused by short circuit, the soft-start circuit
attempts to restart and produces an over-current fault after
about 200 s, which results in a duty cycle of less than 15%,
limiting power dissipation.
The closed-loop peak-current limit is not the same as the
open-loop tested current limit, ILIM(OL), in the Electrical
Characteristics table. This is primarily due to the effect of
propagation delays of the IC current limit comparator.
The current-limit fault response protects the IC in the event
of an over-current condition present during soft-start. As a
result, the IC may fail to start if heavy load is applied during
startup and/or if excessive COUT is used.
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
dV
dt
www.fairchildsemi.com
9
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Operation Description


1
, 6MHz 
fSW  min 
 tSW ( MAX )



When EN is HIGH, the under-voltage lockout keeps the part
from operating until the input supply voltage rises high
enough to properly operate. This ensures no misbehavior of
the regulator during startup or shutdown.
(3)
where:

VOUT  IOUT  ROFF
tSW ( MAX )  40ns  1 
V
IN  IOUT  RON  VOUT

Thermal Shutdown (TSD)
When the die temperature increases, due to a high load
condition and/or a high ambient temperature; the output
switching is disabled until the die temperature falls sufficiently.
The junction temperature at which the thermal shutdown
activates is nominally 150°C with a 15°C hysteresis.




(4)
where:
ROFF = RDSON _ N  DCRL
RON = RDSON _ P  DCRL
Minimum Off-Time Effect on Switching
Frequency
tOFF(MIN) is 40 ns. This imposes constraints on the maximum
VOUT
that the FAN53601/11 can provide or the maximum
VIN
output voltage it can provide at low VIN while maintaining a
fixed switching frequency in PWM Mode.
When VIN is LOW, fixed switching is maintained as long as:
VOUT
 1  t OFF ( MIN )  fSW  0.7 .
VIN
The switching frequency drops when the regulator cannot
provide sufficient duty cycle at 6 MHz to maintain regulation.
This occurs when VOUT is 1.82 V and VIN is below 2.7 V at
high load currents (see Figure 32).
Switching Frequency (KHz)
7,500
6,000
4,500
2.7VIN, AUTO
2.3VIN, AUTO
2.7VIN, PWM
2.3VIN, PWM
3,000
1,500
0
0
200
400
600
800
1000
Load Current (mA)
Figure 32. Frequency vs. Load Current to Demonstrate
tOFFMIN Effect, VIN=2.3 V and 2.7 V, VOUT=1.82 V,
Auto Mode, FPWM Dotted
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
10
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
The calculation for switching frequency is given by:
Under-Voltage Lockout (UVLO)
Selecting the Inductor
The increased RMS current produces higher losses through
the RDS(ON) of the IC MOSFETs, as well as the inductor DCR.
The output inductor must meet both the required inductance
and the energy-handling capability of the application. The
inductor value affects average current limit, the PWM-toPFM transition point, output voltage ripple, and efficiency.
Increasing the inductor value produces lower RMS currents,
but degrades transient response. For a given physical
inductor size, increased inductance usually results in an
inductor with lower saturation current and higher DCR.
The ripple current (∆I) of the regulator is:
Table 1 shows the effects of inductance higher or lower than
the recommended 1 H on regulator performance.
I 
VOUT  VIN  VOUT
 
VIN
 L  fSW




(5)
Output Capacitor
The maximum average load current, IMAX(LOAD), is related to
the peak current limit, ILIM(PK), by the ripple current, given by:
IMAX(LOAD )  ILIM(PK ) 
I
2
Table 2 suggests 0402 capacitors. 0603 capacitors may
further improve performance in that the effective capacitance
is higher. This improves transient response and output ripple.
(6)
Increasing COUT has no effect on loop stability and can
therefore be increased to reduce output voltage ripple or to
improve transient response. Output voltage ripple, ∆VOUT, is:
The transition between PFM and PWM operation is
determined by the point at which the inductor valley current
crosses zero. The regulator DC current when the inductor
current crosses zero, IDCM, is:
IDCM 
I
2
f

C
 ESR2
1
VOUT  IL  SW OUT









2
D
1
D
8
f
C
SW
OUT 

(7)
Input Capacitor
The 2.2 F ceramic input capacitor should be placed as
close as possible between the VIN pin and GND to minimize
the parasitic inductance. If a long wire is used to bring power
to the IC, additional “bulk” capacitance (electrolytic or
tantalum) should be placed between CIN and the power
source lead to reduce the ringing that can occur between the
inductance of the power source leads and CIN.
The FAN53601/11 is optimized for operation with L = 470 nH,
but is stable with inductances up to 1H (nominal). The
inductor should be rated to maintain at least 80% of its value
at ILIM(PK).
Efficiency is affected by the inductor DCR and inductance
value. Decreasing the inductor value for a given physical size
typically decreases the DCR; but because ∆I increases, the
RMS current increases, as do the core and skin effect losses.
IRMS 
2
IOUT(DC ) 
I2
12
(9)
The effective capacitance value decreases as VIN increases
due to DC bias effects.
(8)
Table 1. Effects of Changes in Inductor Value (from 470nH Recommended Value) on Regulator Performance
Inductor Value
IMAX(LOAD)
∆VOUT
Transient Response
Increase
Increase
Decrease
Degraded
Decrease
Decrease
Increase
Improved
Table 2. Recommended Passive Components and their Variation Due to DC Bias
Component
Description
Vendor
Min.
Typ.
Max.
L1
470 nH,
2012,90 mΩ,
1.1 A
Murata LQM21PNR47MC0
Murata LQM21PNR54MG0
Hitachi Metals HLSI 201210R47
300 nH
470 nH
520 nH
CIN
2.2 F, 6.3 V,
X5R, 0402
Murata or Equivalent GRM155R60J225ME15
GRM188R60J225KE19D
1.0 F
2.2 F
COUT
4.7 F, X5R,
0402
Murata or Equivalent GRM155R60G475M
GRM155R60E475ME760
1.6 F
4.7 F
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
11
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Applications Information
There are only three external components: the inductor and
the input and output capacitors. For any buck switcher IC,
including the FAN53601/11, it is important to place a low-ESR
input capacitor very close to the IC, as shown in Figure 33.
The input capacitor ensures good input decoupling, which
helps reduce noise appearing at the output terminals and
ensures that the control sections of the IC do not behave
erratically due to excessive noise. This reduces switching
cycle jitter and ensures good overall performance. It is
important to place the common GND of CIN and COUT as close
as possible to the C2 terminal. There is some flexibility in
moving the inductor further away from the IC; in that case,
VOUT should be considered at the COUT terminal.
Figure 33. PCB Layout Guidance
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
12
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
PCB Layout Guidelines
0.03 C
F
E
2X
A
B
BALL A1
INDEX AREA
0.40
A1
D
(Ø0.20)
Cu Pad
0.40
F
(Ø0.30)
Solder Mask
Opening
0.03 C
2X
TOP VIEW
RECOMMENDED LAND PATTERN
(NSMD PAD TYPE)
0.06 C
0.625
0.547
0.05 C
0.378±0.018
0.208±0.021
E
SEATING PLANE
C
D
SIDE VIEWS
Ø0.260±0.010
6X
0.40
0.005
A. NO JEDEC REGISTRATION APPLIES.
C A B
B. DIMENSIONS ARE IN MILLIMETERS.
C
B
0.40
NOTES:
C. DIMENSIONS AND TOLERANCES PER
ASMEY14.5M, 1994.
(Y) +/-0.018
A
D. DATUM C, THE SEATING PLANE IS DEFINED
BY THE SPHERICAL CROWNS OF THE BALLS.
F
1 2
(X) +/-0.018
E. PACKAGE TYPICAL HEIGHT IS 586 MICRONS
±39 MICRONS (547-625 MICRONS).
BOTTOM VIEW
F. FOR DIMENSIONS D, E, X, AND Y SEE
PRODUCT DATASHEET.
G. DRAWING FILENAME: UC006ACrev4.
Figure 1. 6-Bump WLCSP, 0.4mm Pitch
Product-Specific Dimensions
Product
D
E
X
Y
FAN53611AUC11X
1.160 ±0.030
0.860 ±0.030
0.230
0.180
FAN53611UC123X
1.160 ±0.030
0.860 ±0.030
0.230
0.180
FAN53601UC182X
1.160 ±0.030
0.860 ±0.030
0.230
0.180
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without
notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most
recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which
covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
13
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
Physical Dimensions
FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator
© 2010 Fairchild Semiconductor Corporation
FAN53601 / FAN53611 • Rev. 1.0.1
www.fairchildsemi.com
14