FAIRCHILD FAN53610AUC29X

FAN53600 / FAN53610
3 MHz, 600 mA / 1A Synchronous Buck Regulator
Features
Description
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The FAN53600/10 is a 3 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 FAN53600/10 is capable of delivering a
peak efficiency of 92%, while maintaining efficiency over
80% at load currents as low as 1 mA.
600 mA or 1 A Output Current Capability
26 µA Typical Quiescent Current
3 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 3.3 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
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3G, 4G, WiFi®, WiMAX™, and WiBro® Data Cards
Tablets
The regulator operates at a nominal fixed frequency of
3 MHz, which reduces the value of the external components
to as low as 1 µH 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 26 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 3 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 FAN53600/10 is available in 6-bump, 0.4 mm pitch,
Wafer-Level Chip-Scale Package (WLCSP).
DSC, DVC
Netbooks®, Ultra-Mobile PCs
All trademarks are the property of their respective owners.
Figure 1.
Typical Application
Ordering Information
Output
Voltage(1)
Max. Output
Current
Active
Discharge(2)
FAN53600AUC33X
3.3 V
600 mA
Yes
FAN53610AUC29X
2.9 V
1A
Yes
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
FAN53600 / FAN56310 • Rev. 1.0.0
www.fairchildsemi.com
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
August 2012
MODE
A1
A2
VIN
SW
B1
B2
EN
FB
C1
C2
GND
Figure 2.
Bumps Facing Down
Figure 3.
Bumps Facing Up
Pin Definitions
Pin #
Name
Description
A1
MODE
MODE. Logic 1 on this pin forces the IC to stay in PWM Mode. Logic 0 allows the IC to automatically
switch to PFM Mode during light loads. The regulator also synchronizes its switching frequency to
two times the frequency provided on this pin. Do not leave this pin floating.
B1
SW
Switching Node. Connect to output inductor.
C1
FB
Feedback. Connect to output voltage.
C2
GND
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.
Ground. Power and IC ground. All signals are referenced to this pin.
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
2
FAN53600 / FAN53610 — 3MHz, 600mA / 1A 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
Unit
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
Parameter
VCC
Supply Voltage Range
IOUT
Output Current
L
CIN
COUT
Min.
Max.
Unit
2.3
5.5
V
FAN53600
0
600
mA
FAN53610
0
1
A
Inductor
Input Capacitor
Output Capacitor VOUT<2.7 V
1.6
VOUT ≥2.7 V
Typ.
1
µH
2.2
µF
4.7
12.0
µF
10
TA
Operating Ambient Temperature
–40
+85
°C
TJ
Operating Junction Temperature
–40
+125
°C
Thermal Properties
Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with two-layer 1s2p
boards in accordance to JEDEC standard JESD51. Special attention must be paid not to exceed junction temperature TJ(max) at a
given ambient temperature TA.
Symbol
θJA
Parameter
Junction-to-Ambient Thermal Resistance
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
Typical
Unit
150
°C/W
www.fairchildsemi.com
3
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Absolute Maximum Ratings
Minimum and maximum values are at VIN = VEN = 2.3 V to 5.5 V, VMODE = 0V (AUTO Mode), and 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, VOUT=2.9 V.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
Power Supplies
IQ
I(SD)
VUVLO
Quiescent Current
Shutdown Supply Current
No Load, Not Switching
26
µA
PWM Mode
3
mA
VIN = 3.6 V, EN = GND
Under-Voltage Lockout Threshold Rising VIN
VUVHYST Under-Voltage Lockout Hysteresis
0.25
1.00
µA
2.15
2.27
V
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
2.7
3.0
3.3
MHz
Square Wave at MODE Input
1.3
1.5
1.7
MHz
ILOAD = 0 to 600 mA
1.207
1.233
1.272
V
PWM Mode
1.207
1.233
1.259
V
ILOAD = 0 to 600 mA
1.784
1.820
1.875
V
PWM Mode
1.784
1.820
1.856
V
ILOAD = 0 to 400 mA, VIN ≥ VOUT +
150mV
2.755
(-5%)
2.900
2.987
(+3%)
V
ILOAD = 0 to 600 mA, VIN ≥ VOUT +
300 mV
2.813
(-3%)
2.900
2.987
(+3%)
V
From EN Rising Edge
180
300
µs
PMOS On Resistance
VIN = VGS = 3.6 V
175
mΩ
NMOS On Resistance
VIN = VGS = 3.6 V
165
mΩ
(4)
MODE Synchronization Range
Regulation
1.233V
1.820V
VO
Output Voltage Accuracy
2.900V
tSS
Soft-Start
Output Driver
RDS(on)
ILIM(OL)
PMOS Peak Current Limit
Open-Loop for FAN53600
900
1100
1250
mA
Open-Loop for FAN53610
1500
1750
2000
mA
RDIS
Output Discharge Resistance
EN = GND
230
Ω
TTSD
Thermal Shutdown
CCM Only
150
°C
THYS
Thermal Shutdown Hysteresis
15
°C
Notes:
4. Limited by the effect of tOFF minimum (see Operation Description section).
5. The Electrical Characteristics table reflects open-loop data.
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
4
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Electrical Characteristics
98%
100%
95%
95%
92%
90%
Efficiency
Efficiency
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
89%
86%
85%
80%
3.6
4.2
5.0
5.5
83%
80%
0
200
400
600
800
VIN
VIN
VIN
VIN
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
75%
70%
1000
0
200
Load Current (mA)
600
95%
95%
92%
90%
Efficiency
100%
89%
86%
85%
80%
3.2 VIN
3.6 VIN
4.2 VIN
5.0 VIN
83%
80%
200
400
600
1000
Figure 5. Efficiency vs. Load Current and
Temperature VIN=5 V, VOUT=3.3 V, Dotted for FPWM
98%
0
800
Load Current (mA)
Figure 4. Efficiency vs. Load Current and Input
Voltage, VOUT=3.3 V, Dotted for Decreasing Load
Efficiency
400
800
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
75%
70%
0
1000
200
Load Current (mA)
400
600
800
1000
Load Current (mA)
Figure 6. Efficiency vs. Load Current and Input
Voltage, VOUT=2.9 V, Dotted for Decreasing Load
Figure 7. Efficiency vs. Load Current and
Temperature, VOUT=2.9 V, Dotted for FPWM
95%
95%
93%
90%
91%
85%
87%
Efficiency
Efficiency
89%
85%
83%
80%
75%
81%
79%
2.7 VIN
3.6 VIN
4.2 VIN
5.0 VIN
77%
75%
0
200
400
600
800
70%
65%
0
1000
Load Current (mA)
200
400
600
800
1000
Load Current (mA)
Figure 8. Efficiency vs. Load Current and Input
Voltage, VOUT=1.82 V, Dotted for Decreasing Load
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
Figure 9. Efficiency vs. Load Current
and Temperature, VOUT=1.82 V, Dotted for FPWM
www.fairchildsemi.com
5
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
91%
90%
88%
85%
85%
Efficiency
Efficiency
80%
82%
79%
75%
70%
- 40C, AUTO
+25C, AUTO
+85C, AUTO
- 40C, PWM
+25C, PWM
+85C, PWM
76%
2.7 VIN
3.6 VIN
4.2 VIN
5.0 VIN
73%
70%
0
200
400
600
65%
60%
800
1000
0
200
Load Current (mA)
3
800
3
2.7VIN, AUTO
3.6VIN, AUTO
4.2VIN, AUTO
5.0VIN, AUTO
2.7VIN, PWM
3.6VIN, PWM
4.2VIN, PWM
5.0VIN, PWM
1000
1
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 (%)
2
Output Regulation (%)
600
Figure 11. Efficiency vs. Load Current and
Temperature, VOUT=1.23 V, Dotted for FPWM
Figure 10. Efficiency vs. Load Current and Input
Voltage, VOUT=1.23 V, Dotted for Decreasing Load
0
-1
-2
1
0
-1
-2
0
200
400
600
800
1000
0
200
Load Current (mA)
400
600
800
Figure 13. ∆VOUT (%) vs. Load Current and Input
Voltage, VOUT=1.23 V, Normalized to 3.6 VIN, 500 mA
Load, FPWM, Dotted for Auto Mode
500
400
400
Load Current (mA)
500
300
200
100
300
200
100
PWM
PWM
PFM
PFM
100% d.c.
0
3.3
3.8
4.3
4.8
100% d.c.
0
2.9
5.3
3.4
3.9
4.4
4.9
5.4
Input Voltage (V)
Input Voltage (V)
Figure 15. PFM / PWM /100% Duty Cycle Boundary
vs. Input Voltage, VOUT=2.9 V
Figure 14. PFM / PWM /100% Duty Cycle Boundary
vs. Input Voltage, VOUT=3.3 V
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
1000
Load Current (mA)
Figure 12. ∆VOUT (%) vs. Load Current and Input
Voltage, VOUT=1.82 V, Normalized to 3.6 VIN, 500mA
Load, FPWM, Dotted for Auto Mode
Load Current (mA)
400
Load Current (mA)
www.fairchildsemi.com
6
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
500
500
400
400
Load Current (mA)
Load Current (mA)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
300
200
100
300
200
100
PWM
PWM
PFM
PFM
0
2.5
3.0
3.5
4.0
4.5
5.0
0
5.5
2.5
3.0
Input Voltage (V)
35
35
Input Current (μ A)
Input Current (μ A)
40
30
25
20
- 40C, EN=VIN
+25C, EN=VIN
+85C, EN=VIN
- 40C, EN=1.8V
+25C, EN=1.8V
+85C, EN=1.8V
15
10
3.5
4.0
5.0
4.5
5.0
25
20
- 40C, EN=VIN
+25C, EN=VIN
+85C, EN=VIN
- 40C, EN=1.8V
+25C, EN=1.8V
+85C, EN=1.8V
15
10
5.5
2.5
3.0
3.5
4.0
4.5
5.0
Figure 19. Quiescent Current vs. Input Voltage and
Temperature, VOUT=1.82 V, EN=VIN Solid, Dotted for
EN=1.8 V
25
20
20
Input Current (mA)
25
15
10
5
15
10
5
- 40C
- 40C
+25C
+25C
+85C
0
3.0
3.5
4.0
4.5
5.0
+85C
0
2.5
5.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Input Voltage (V)
Figure 20. Quiescent Current vs. Input Voltage and
Temperature, VOUT=2.9 V, Mode=EN=VIN (FPWM)
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
5.5
Input Voltage (V)
Figure 18. Quiescent Current vs. Input Voltage and
Temperature, VOUT=2.9 V, EN=VIN Solid, Dotted for
EN=1.8 V
2.5
5.5
30
Input Voltage (V)
Input Current (mA)
4.5
Figure 17. PFM / PWM Boundary vs. Input Voltage,
VOUT=1.23 V
40
3.0
4.0
Input Voltage (V)
Figure 16. PFM / PWM Boundary vs. Input Voltage,
VOUT=1.82 V
2.5
3.5
Figure 21. Quiescent Current vs. Input Voltage and
Temperature, VOUT=1.82 V, Mode=EN=VIN (FPWM)
www.fairchildsemi.com
7
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
100
50
3.2VIN, AUTO
2.7VIN, AUTO
3.6VIN, AUTO
3.2VIN, PWM
3.6VIN, PWM
5.0VIN, PWM
60
5.0VIN, AUTO
40
Output Ripple (mVpp)
Output Ripple (mVpp)
3.6VIN, AUTO
5.0VIN, AUTO
80
40
20
2.7VIN, PWM
3.6VIN, PWM
5.0VIN, PWM
30
20
10
0
0
0
200
400
600
800
1000
0
200
Load Current (mA)
3,500
3,500
3,000
3,000
2,500
3.2VIN, AUTO
3.6VIN, AUTO
1,500
5.0VIN, AUTO
3.2VIN, PWM
1,000
3.6VIN, PWM
5.0VIN, PWM
1,500
2.7VIN, AUTO
5.0VIN, AUTO
0
600
800
1000
3.6VIN, AUTO
1,000
0
400
1000
2,000
500
200
800
2,500
500
0
600
Figure 23. Output Ripple vs. Load Current and Input
Voltage, VOUT=2.9 V, FPWM, Dotted for Auto Mode
Switching Frequency (KHz)
Switching Frequency (KHz)
Figure 22. Output Ripple vs. Load Current and Input
Voltage, VOUT=2.9 V, FPWM, Dotted for Auto Mode
2,000
400
Load Current (mA)
2.7VIN, PWM
3.6VIN, PWM
5.0VIN, PWM
0
Load Current (mA)
200
400
600
800
1000
Load Current (mA)
Figure 24. . Frequency vs. Load Current and Input
Voltage, VOUT=2.9 V, Auto Mode, Dotted for FPWM
Figure 25. Frequency vs. Load Current and Input
Voltage, VOUT=1.82 V, Auto Mode, Dotted for FPWM
Figure 26. Load Transient, VIN=5 V, VOUT=3.3 V,
10-200-10 mA, 100 ns Edge
Figure 27. Load Transient, VIN=5 V, VOUT=3.3 V, 200800-200 mA, 100 ns Edge
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
8
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
Figure 28. Load Transient, VIN=5 V, VOUT=2.9 V,
10-200-10 mA, 100 ns Edge
Figure 29. Load Transient, VIN=5 V, VOUT=2.9 V,
200-800-200 mA, 100 ns Edge
Figure 30. Line Transient, 3.3-3.9-3.3 VIN, 10 µs Edge,
VOUT=2.9 V, 58 mA Load
Figure 31. Line Transient, 3.3-3.9-3.3 VIN, 10 µs Edge,
VOUT=2.9 V, 600 mA Load
Figure 32. Combined Line / Load Transient,
VOUT=2.9V, 3.9-3.3-3.9 VIN, 10 µs Edge, 58-500-58 mA
Load, 100 ns Edge
Figure 33. Startup, 50 Ω Load
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
9
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), and TA = 25°C.
Figure 34. Startup, 4.7 Ω Load
Figure 35. Over-Current, Load Increasing Past Current
Limit, FAN53600
Figure 36. 250 mΩ Fault, Rapid Fault, FAN53600
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
10
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
The FAN53600/10 is a 3 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 FAN53600/10 is capable of delivering a
peak efficiency of 92%, while maintaining efficiency over
80% at load currents as low as 1 mA.
All voltage options can be ordered with a feature that actively
discharges FB to ground through a 230 Ω path when EN is
LOW. Raising EN above its threshold voltage activates the
part and starts the soft-start cycle. During soft-start, the
internal reference is ramped using an exponential RC shape
to prevent overshoot of the output voltage. Current limiting
minimizes inrush during soft-start.
The regulator operates at a nominal fixed frequency of
3 MHz, which reduces the value of the external components
to as low as 1 µH 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.
The IC may fail to start if heavy load is applied during startup
and/or if excessive COUT is used. This is due to the currentlimit fault response, which protects the IC in the event of an
over-current condition present during soft-start.
The current required to charge COUT during soft-start,
commonly referred to as “displacement current,” is given as:
Control Scheme
dV
(2)
dt
dV
term refers to the soft-start slew rate above.
where the
dt
The FAN53600/10 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 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.
IDISP = COUT •
To prevent shutdown during soft-start, the following condition
must be met:
IDISP + ILOAD < IMAX ( DC )
where IMAX(DC) is the maximum load current the IC is
guaranteed to support.
For very light loads, the FAN53600/10 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, with a glitch of less than 18 mV at VOUT during the
transition between DCM and CCM modes.
Startup into Large COUT
Multiple soft-start cycles are required for no-load startup if
COUT is greater than 15 μF. Large COUT requires light initial
load to ensure the FAN53600/10 starts appropriately. The IC
shuts down for 1.3 ms when IDISP exceeds ILIMIT for more
than 210 μs 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.
Combined
with
exceptional
transient
response
characteristics, the very low quiescent current of the
controller (26 µA) maintains high efficiency, even at very light
loads, while preserving fast transient response for
applications requiring tight output regulation.
MODE Pin
100% Duty Cycle Operation
Logic 1 on this pin forces the IC to stay in PWM Mode. 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 two times the frequency on the
MODE pin (fMODE).
When VIN approaches VOUT, the regulator increases its duty
cycle until 100% duty cycle is reached. As the duty cycle
approaches 100%, the switching frequency declines due to
the minimum off-time (tOFF(MIN)) of about 50 ns imposed by
the control circuit. When 100% duty cycle is reached, VOUT
follows VIN with a drop-out voltage (VDROPOUT) determined by
the total resistance between VIN and VOUT as calculated by:
(
VDROPOUT = ILOAD • PMOS R DS(ON) + DCR L
(3)
)
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.
(1)
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/μs
from 0 to 1 VOUT, then 12.5 mV/μs 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.
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
11
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Operation Description
Minimum Off-Time and Switching Frequency
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.
tOFF(MIN) is 50 ns. This imposes constraints on the maximum
VOUT
that the FAN53600/10 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 frequency is maintained as
long as:
If the fault was caused by short circuit, the soft-start circuit
attempts to restart and produces an over-current fault after
about 250 μs, which results in a duty cycle of less than 0%,
limiting power dissipation.
VOUT
≤ 1 − tOFF ( MIN ) • fSW ≈ 0.85 .
VIN
The switching frequency drops when the regulator cannot
provide sufficient duty cycle at 3 MHz to maintain regulation.
This occurs when VOUT >0.85 VIN at high load currents. The
calculation for switching frequency is given by:
The closed-loop peak-current limit, ILIM(PK), 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.


1
, 3MHz 
fSW = min 
 tSW ( MAX )



Under-Voltage Lockout (UVLO)
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.
where:

VOUT + IOUT • ROFF
t SW ( MAX ) = 50ns •  1 +
V
IN − IOUT • RON − VOUT

Thermal Shutdown (TSD)




(5)
where:
When the die temperature increases, due to a high load
condition and/or a high ambient temperature, the output
switching is disabled until the temperature on the die has
fallen sufficiently. The junction temperature at which the
thermal shutdown activates is nominally 150°C with a
15°C hysteresis.
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
(4)
ROFF
RON
= RDSON _ N + DCRL
= RDSON _ P + DCRL .
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12
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Current Limit, Fault Shutdown, and Restart
The increased RMS current produces higher losses through
the RDS(ON) of the IC MOSFETs, as well as the inductor DCR.
Selecting the Inductor
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:
 V − VOUT
V
ΔI ≈ OUT •  IN
VIN
 L • fSW




Table 1 shows the effects of inductance higher or lower than
the recommended 1 μH on regulator performance.
(6)
Output Capacitor
The maximum average load current, IMAX(LOAD), is related to
the peak current limit, ILIM(PK), by the ripple current, given by:
I MAX ( LOAD ) = I LIM ( PK ) −
ΔI
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.
(7)
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 =
ΔI
2
f

⋅C
⋅ ESR2
1
ΔVOUT = ΔIL  SW OUT
+

(
)
⋅
⋅
−
⋅
⋅
2
D
1
D
8
f
C
SW
OUT 

(8)
Input Capacitor
The 2.2 μF ceramic input capacitor should be placed as
close as possible between the VIN pin and GND to minimize
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 ringing that can occur between the inductance of the
power source leads and CIN.
The FAN53600/10 is optimized for operation with L = 1 μH,
but is stable with inductances up to 2.2 μH (nominal). The
inductor should be rated to maintain at least 80% of its value
at ILIM(PK).
Efficiency is affected by inductor DCR and inductance value.
Decreasing the inductor value for a given physical size
typically decreases DCR; but since ∆I increases, the RMS
current increases, as do the core and skin effect losses:
IRMS =
Table 1.
2
IOUT(DC ) +
ΔI2
12
The effective capacitance value decreases as VIN increases
due to DC bias effects.
(9)
Effects of Changes in Inductor Value (470 nH Recommended Value) on Regulator Performance
Inductor Value
Table 2.
(10)
IMAX(LOAD)
∆VOUT
Transient Response
Increase
Increase
Decrease
Degraded
Decrease
Decrease
Increase
Improved
Recommended Passive Components and Variation Due to DC Bias
Component
Description
Vendor
1 μH, 2012, 190 mΩ,
0.8 A
Murata LQM21PN1R0MC0
1 μH
Not recommended for 1A load
1 μH, 1.4 A, 85 mΩ,
2016
Murata LQM2MPN1R0M
1 μH
Utilized to generate graphs,
Figure 4 — Figure 36
CIN
2.2 μF, 6.3 V, X5R,
0402
Murata or Equivalent
GRM155R60J225ME15
GRM188R60J225KE19D
1.0 μF
2.2 μF
Decrease primarily due to DC bias
(VIN) and elevated temperature
COUT
4.7 μF, X5R 0603
Murata or Equivalent
GRM188R60G106ME47D
1.6 μF
4.7 μF
Decrease primarily due to DC bias
(VOUT) and elevated temperature
L1
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
Min.
Typ.
Comment
www.fairchildsemi.com
13
FAN53600 / FAN53610 — 3MHz, 600mA / 1A 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 FAN53600/10, it is important to place a low-ESR
input capacitor very close to the IC, as shown in Figure 37.
The input capacitor ensures good input decoupling, which
helps reduce noise at the output terminals and ensures that
the control sections of the IC do not behave erratically due to
Figure 37.
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
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.
3 MHz PCB Layout Guidance
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14
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
PCB Layout Guidelines
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
Physical Dimensions
Figure 38.
6-Bump WLCSP, 0.4mm Pitch
Product-Specific Dimensions
Product
D
E
X
Y
FAN53600AUC33X
1.160 ±0.030
0.860 ±0.030
0.230
0.180
FAN53610AUC29X
1.160 ±0.030
0.860 ±0.030
0.230
0.180
FAN53610UC33X
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
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
15
FAN53600 / FAN53610 — 3MHz, 600mA / 1A Synchronous Buck Regulator
© 2010 Fairchild Semiconductor Corporation
FAN53600 / FAN53610 • Rev. 1.0.0
www.fairchildsemi.com
16