Fairchild FAN5361UC13X 6mhz, 600ma tinybuckâ ¢ synchronous buck regulator Datasheet

FAN5361
6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Features
Description
„ 6MHz Fixed-Frequency Operation
The FAN5361 is a 600mA, step-down, switching voltage
regulator that delivers a fixed output from an input voltage
supply of 2.3V to 5.5V. Using a proprietary architecture with
synchronous rectification, the FAN5361 is capable of
delivering a peak efficiency of 92%, while maintaining
efficiency over 80% at load currents as low as 1mA.
„ 35µA Typical Quiescent Current
„ Best-in-Class Load Transient
„ 600mA Output Current Capability
„ 2.3V to 5.5V Input Voltage Range
„ 1.0 to 1.82V 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
The regulator operates at a nominal fixed frequency of 6MHz,
which reduces the value of the external components to 470nH
for the output inductor and 4.7µF for the output capacitor. The
PWM modulator can be synchronized to an external frequency
source.
At moderate and light loads, pulse frequency modulation is
used to operate the device in power-save mode with a typical
quiescent current of 35µA. 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 6MHz. In
shutdown mode, the supply current drops below 1µA,
reducing power consumption. For applications that require
minimum ripple or fixed frequency, PFM mode can be
disabled using the MODE pin.
„ 6-bump WLCSP, 0.4mm Pitch
„ 6-pin 2 x 2mm UMLP
Applications
„ Cell Phones
„ Portable Media Players
„ WLAN, 3G, and 4G Data Cards
The FAN5361 is available in 6-bump, 0.4mm pitch, WaferLevel Chip-Scale Package (WLCSP) and a 6-lead 2 x 2mm
ultra-thin MLP package.
Typical Applications
MODE
L1
SW
470nH
FB
4.7 F
A1
A2
B1
B2
C1
C2
VIN
EN
CIN
2.2 F
GND
COUT
Figure 1. Typical Applications
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
September 2008
Output
(1)
Voltage
Part Number
(2)
FAN5361UC10X
1.0V
FAN5361UC12X
1.2V
(2)
1.3V
(2)
1.5V
(2)
1.8V
FAN5361UC13X
FAN5361UC15X
FAN5361UC18X
FAN5361UC182X
Eco Status Temperature Range
Package
Packing
WLCSP-6 0.4mm Pitch
Green
–40 to +85°C
Tape and Reel
6 Lead UMLP 2 x 2mm
RoHS
–40 to +85°C
Tape and Reel
1.82V
(2)
1.0V
(2)
1.2V
(2)
1.3V
(2)
1.5V
(2)
1.8V
FAN5361UMP10X
FAN5361UMP12X
FAN5361UMP13X
FAN5361UMP15X
FAN5361UMP18X
For Fairchild’s definition of “green” Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
Notes:
1. Other voltage options available on request. Contact a Fairchild representative.
2. Preliminary release.
Pin Configuration
MODE
A1
A2
VIN
VIN
A2
A1
MODE
SW
B1
B2
EN
EN
B2
B1
SW
FB
C1
C2
GND
GND
C2
C1
FB
Figure 2. WLCSP, Bumps Facing Down
Figure 3. WLCSP, Bumps Facing Up
Figure 4. UMLP, Leads Facing Down
Pin Definitions
Pin #
WLCSP MLP
A1
3
Name Description
MODE. Logic 1 on this pin forces the IC to stay in PWM mode. A logic 0 allows the IC to automatically
MODE 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.
B1
2
SW
Switching Node. Connect to output inductor.
C1
1
FB
Feedback / VOUT. Connect to output voltage.
C2
6
GND
B2
5
EN
Enable. The device is in shutdown mode when voltage to this pin is <0.4V and enabled when >1.2V.
Do not leave this pin floating.
A2
4
VIN
Input Voltage. Connect to input power source.
Ground. Power and IC ground. All signals are referenced to this pin.
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
2
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Ordering Information
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
Min.
Max.
Input Voltage
–0.3
7.0
Voltage on SW Pin
–0.3
Units
V
(3)
V
(3)
V
(3)
V
VIN + 0.3
EN and MODE Pin Voltage
–0.3
VIN + 0.3
Other Pins
–0.3
VIN + 0.3
Human Body Model per JESD22-A114
4
kV
1.5
kV
ESD
Electrostatic Discharge
Protection Level
TJ
Junction Temperature
–40
+150
°C
TSTG
Storage Temperature
–65
+150
°C
+260
°C
TL
Charged Device Model per JESD22-C101
Lead Soldering Temperature, 10 Seconds
Note:
3. Lesser of 7V or VIN+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
VCC
IOUT
L
CIN
COUT
Parameter
Min.
Supply Voltage Range
Typ.
2.3
Output Current
0
Max.
Units
5.5
V
600
mA
Inductor
0.47
µH
Input Capacitor
2.2
µF
Output Capacitor
4.7
µF
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 four-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 temperate TA.
Symbol Parameter
θJA
Junction-to-Ambient Thermal Resistance
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
Typical
Units
WLCSP
150
°C/W
MLP
49
°C/W
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3
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Absolute Maximum Ratings
Minimum and maximum values are at VIN = VEN = 2.3V to 5.5V, AUTO Mode, TA = -40°C to +85°C; circuit of Figure 1, unless
otherwise noted. Typical values are at TA = 25°C, VIN = VEN = 3.6V.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
No load, Not Switching
35
55
PWM Mode
6
Units
Power Supplies
IQ
I(SD)
Quiescent Current
Shutdown Supply Current
VIN = 3.6V, EN = GND
0.05
1.00
Rising VIN
2.15
2.25
VUVLO
Under-Voltage Lockout Threshold
VUVHYST
Under-Voltage Lockout hysteresis
V(ENH)
Enable HIGH-Level Input Voltage
V(ENL)
Enable LOW-Level Input Voltage
I(EN)
Enable Input Leakage Current
V(MH)
MODE HIGH-Level Input Voltage
V(ML)
MODE LOW-Level Input Voltage
I(M)
150
MODE Input Leakage Current
V
V
0.01
0.4
V
1.00
µA
1.2
MODE to VIN or GND
µA
mV
1.2
EN to VIN or GND
µA
mA
V
0.4
V
0.01
1.00
µA
Switching and Synchronization
fSW
fSYNC
Switching Frequency
(4)
MODE Synchronization Range
VIN = 3.6V, TA = 25°C
5.4
6.0
6.6
MHz
Squarewave at MODE Input
1.3
1.5
1.7
MHz
ILOAD = 0 to 600mA
1.784
1.820
1.875
V
PWM Mode
1.784
1.820
1.856
V
Regulation
1.82V
1.80V
VO
Output Voltage
Accuracy
1.50V
ILOAD = 0 to 600mA
1.764
1.800
1.854
V
PWM Mode
1.764
1.800
1.836
V
ILOAD = 0 to 600mA
1.470
1.500
1.545
V
PWM Mode
1.470
1.500
1.530
V
ILOAD = 0 to 600mA
1.274
1.300
1.339
V
PWM Mode
1.274
1.300
1.326
V
ILOAD = 0 to 600mA
1.174
1.200
1.239
V
PWM Mode
1.174
1.200
1.226
V
ILOAD = 0 to 600mA
0.974
1.000
1.039
V
PWM Mode
0.974
1.000
1.026
V
From EN Rising Edge
150
300
µs
PMOS On Resistance
VIN = VGS = 3.6V
350
mΩ
NMOS On Resistance
VIN = VGS = 3.6V
225
mΩ
ILIM
PMOS Peak Current Limit
Open-Loop
TTSD
Thermal Shutdown
CCM Only
THYS
Thermal Shutdown Hysteresis
1.30V
1.20V
1.00V
tSS
Soft-Start
Output Driver
RDS(on)
900
1000
1250
mA
150
°C
15
°C
Notes:
4. Limited by the effect of tOFF minimum (see Figure 13 in Typical Performance Characteristics).
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
4
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Electrical Characteristics
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C.
100%
100%
95%
90%
90%
85%
85%
80%
Efficiency
Efficiency
95%
Auto 2.3VIN
75%
70%
Auto 2.7VIN
65%
Auto 3.6VIN
60%
80%
75%
25C
70%
85C
65%
60%
Auto 4.2VIN
55%
-30C
55%
50%
50%
1
10
100
1000
1
10
I LOAD Output Current (mA)
100
1000
I LOAD Output Current (mA)
100%
100%
95%
95%
90%
90%
85%
85%
80%
80%
Efficiency
Efficiency
Figure 5. Efficiency vs. Load Current vs. Input Supply Figure 6. Efficiency vs. Load Current vs. Temperature
75%
VIN=2.3V
70%
VIN=2.7V
65%
75%
70%
65%
VIN=3.6V
60%
55%
Auto PFM/PWM
60%
VIN=4.2V
55%
VOUT = 1.2 V
Forced PWM
50%
50%
1
10
100
1
1000
10
100
1000
I LOAD Output Current (mA)
I LOAD Output Current (mA)
Figure 7. Efficiency vs. Load Current vs. Input Supply
Figure 8. Efficiency, Auto PWM/PFM vs. Forced PWM
1.82
1.215
VIN=2.3V
1.210
VIN=2.7V
VIN=3.6V
V OUT (V)
Output Voltage (V)
1.81
1.80
VIN=2.3V
1.205
VIN=4.2V
1.200
VIN=2.7V
1.79
1.195
VIN=3.6V
VIN=4.2V
1.190
1.78
0
100
200
300
400
500
0.0
600
Figure 9. Load Regulation vs. Input Supply
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
0.1
0.2
0.3
0.4
0.5
0.6
I LOAD Output Current (A)
Load Current (mA)
Figure 10. 1.2VOUT Load Regulation vs. Input Supply
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5
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C.
45
50
V OUT Ripple (mVpp)
40
VIN=2.5V
40
VIN=3.6V
35
V OUT Ripple (m Vpp)
45
VIN=5.5V
35
30
25
20
COUT=4.7μF nom.
2.5VIN
3.6VIN
30
5.5VIN
25
VOUT=1.2V
COUT=4.7µF nom.
20
15
10
15
5
10
0
5
0
0.1
0.2
0.3
0.4
0.5
0
0.6
0.1
0.2
0.3
0.4
0.5
0.6
ILOAD Output Current (A)
ILOAD Output Current (A)
Figure 11. Peak-to-Peak Output Voltage Ripple
Figure 12. 1.2VOUT Peak-to-Peak Output Voltage Ripple
Switching Frequency (MHz)
7
6
5
4
3
2
VIN>2.4V
1
VOUT=1.2V
VIN=2.3V
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Load Current (A)
Figure 14. 1.2VOUT Effect of tOFF(MIN) on
Switching Frequency
Figure 13. Effect of tOFF(MIN) on Switching Frequency
350
350
300
300
Always PWM
Always PWM
200
Load Current (mA)
Load Current (mA)
250
The switching mode changes
at these borders
150
100
Always PFM
250
200
The switching mode changes
at these borders
150
100
Always PFM
PFM Border
50
PFM border
50
PWM Borde
PWM border
0
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
Input Voltage (V)
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Figure 15. PFM / PWM Boundaries
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
3.0
Figure 16. 1.2VOUT PFM / PWM Boundaries
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6
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C.
42
1.810
1.805
38
V OUT (V)
Quiescent Current (μA)
40
36
34
32
1.800
1.795
1.790
VEN=VIN
Auto PWM/PFM
Forced PWM
VEN=1.8V
30
2.0
2.5
3.0
3.5
4.0
4.5
5.0
1.785
5.5
1
VIN Input Voltage (V)
10
100
1,000
I LOAD Output Current (mA)
Figure 18. Load Regulation, Auto PFM / PWM and
Forced PWM
Figure 17. Quiescent Curent vs. Input Voltage
0.20
0.18
VIN=5.5V
VEN=0V
Supply Current (µA)
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
-40
-20
0
20
40
60
80
Ambient Temperature (°C)
Figure 19. Shutdown Current vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
7
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C, 5µs/div. horizontal sweep.
Figure 20. Line Transient 3.3VIN to 3.9VIN,
50mA Load, 10µs/div.
Figure 21. Line Transient 3.3VIN to 3.9VIN,
250mA Load, 10µs/div.
Figure 22.
Combined Line/Load Transient 3.3 to
Figure 23. Combined Line/Load Transient 3.9 to 3.3VIN
Combined with 400mA to 40mA Load Transient
3.9VIN Combined with 400mA to 40mA Load Transient
Figure 24. Load Transient 0 to 150mA, 2.5VIN
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
Figure 25. Load Transient 50 to 250mA, 2.5VIN
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8
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C, 5µs/div. horizontal sweep.
Figure 26. Load Transient 150 to 400mA, 2.5VIN
Figure 27. Load Transient 0 to 150mA, 3.6VIN
Figure 28. Load Transient 50 to 250mA, 3.6VIN
Figure 29. Load Transient 150 to 400mA, 3.6VIN
Figure 30. Load Transient 0 to 150mA, 4.5VIN
Figure 31. Load Transient 50 to 250mA, 4.5VIN
Figure 32. Load Transient 150 to 400mA, 4.5VIN
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
9
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C, 5µs/div. horizontal sweep.
Figure 33. Metallic Short Applied at VOUT, 20μs/div.
Figure 34. Metallic Short Applied at VOUT
Figure 35. Over-Current Fault Response,
RLOAD = 1Ω, 20μs/div.
Figure 36. Over-Current Fault Response, RLOAD = 1Ω
Figure 37. 1.2VOUT Overload Recovery to Light Load
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
10
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
Unless otherwise noted, VIN = VEN = 3.6V, VMODE = 0V, VOUT = 1.82V, TA = 25°C.
Figure 39. SW-Node Jitter (Infinite Persistence),
ILOAD = 200mA, 50ns/div.
Figure 38. Soft-Start, RLOAD = 50Ω, 20μs/div.
Figure 40. Power Supply Rejection Ratio at 300mA Load
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
11
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Typical Performance Characteristics (Continued)
The FAN5361 is a 600mA, step-down, switching voltage
regulator that delivers a fixed output from an input voltage
supply of 2.3V to 5.5V. Using a proprietary architecture with
synchronous rectification, the FAN5361 is capable of
delivering a peak efficiency of 92%, while maintaining
efficiency over 80% at load currents as low as 1mA. The
regulator operates at a nominal frequency of 6MHz at full load,
which reduces the value of the external components to 470nH
for the inductor and 4.7µF for the output capacitor.
cycle-by-cycle. After 21µs of current limit, the regulator
triggers an over-current fault, causing the regulator to shut
down for about 86μs before attempting a restart.
Control Scheme
When EN is high, the under-voltage lock-out keeps the part
from operating until the input supply voltage rises high enough
to properly operate. This ensures no misbehavior of the
regulator during start-up or shutdown.
If the fault was caused by short circuit, the soft-start circuit
attempts to restart at 33% of normal current limit and produces
an over-current fault after about 21μs, which results in a duty
cycle of less than 25% providing current into a short.
Under-Voltage Lockout (UVLO)
The FAN5361 uses a proprietary, non-linear, fixed-frequency
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.
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 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.
For very light loads, the FAN5361 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 18mV at VOUT during the transition between DCM
and CCM modes.
Minimum Off-Time Effect on Switching
Frequency
tOFF(MIN) is 50ns. This imposes constraints on the maximum
VOUT
that the FAN5361 can provide, while maintaining a
VIN
fixed switching frequency in PWM mode.
Combined with exceptional transient response characteristics,
the very low quiescent current of the controller (35µA)
maintains high efficiency; even at very light loads, while
preserving fast transient response for applications requiring
tight output regulation.
VOUT
≤ 1 − tOFF ( MIN ) • fSW ≈ 0.7
VIN
Enable and Soft-Start
fSW ≈
Maintaining the EN pin LOW keeps the FAN5361 in nonswitching mode, in which all circuits are off and the part draws
~50nA of current. Increasing EN above its threshold voltage
activates the part and starts the soft-start cycle. The output
ramp during soft-start is a fixed slew rate of 50mV/μs from 0 to
1VOUT, then 25mV/μs for 1.82VOUT or 12mV/µs for 1.2VOUT
until the output reaches its setpoint.
The switching frequency drops when the regulator cannot
provide sufficient duty cycle at 6Mhz to maintain regulation.
This occurs when VOUT is 1.8V or 1.82V and VIN is below 3V at
high load currents (see Figure 13).
The calculation for switching frequency is given by:
MODE pin
⎛
⎞
1
1
⎟
fSW = min ⎜
,
⎜ tSW ( MAX ) 166.6ns ⎟
⎝
⎠
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, the converter synchronizes
its switching frequency to four times the frequency on the
mode pin (fMODE). The mode pin must be held LOW for at least
10μs or HIGH for 10μs to ensure that the converter does not
attempt to synchronize to this pin.
(1)
where:
⎛
VOUT + IOUT • ROFF
tSW (MAX ) = 50ns • ⎜⎜1 +
V
IN − IOUT • RON − VOUT
⎝
Current Limit, Fault Shutdown, and Restart
where:
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
ROFF
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
VIN − VOUT
50ns • VIN
RON
⎞
⎟
⎟
⎠
(2)
= RDSON _ N + DCRL
= RDSON _ P + DCRL
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FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Operation Description
The increased RMS current produces higher losses through
the RDS(ON) of the IC MOSFETs, as well as the inductor ESR.
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-to-PFM
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.
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 470nH on regulator performance.
(3)
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 ) −
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.
(4)
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
⎛
⎞
1
ΔVOUT = ΔI • ⎜⎜
+ ESR ⎟⎟
⎝ 8 • COUT • fSW
⎠
Input Capacitor
(5)
The 2.2μF 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 ringing that can occur between the inductance of the
power source leads and CIN.
The FAN5361 is optimized for operation with L = 470nH, but is
stable with inductances up to 1.2μH (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 since ∆I increases, the RMS
current increases, as do the core and skin effect losses.
2
IRMS =
IOUT(DC ) +
ΔI 2
12
(7)
The effective capacitance value decreases as VIN increases
due to DC Bias effects. This has no significant impact on
regulator performance.
(6)
Table 1. Effects of Changes in Inductor Value (from 470nH Recommended Value) on Regulator Performance
Inductor Value
IMAX(LOAD)
∆VOUT EQ. 7
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.
L1
470nH, 2012,
90mΩ,1.1A
Murata LQM21PNR47MG0
Hitachi Metals JLSI-2012AG-R47(D2A)
CIN
2.2μF, X5R,
0402
COUT
4.7μF, X5R,
0402
Typ.
Max.
Comment
300nH 470nH 520nH
Minimum value occurs
at maximum current
Murata or Equivalent
GRM155R60J225ME15
1.0μF
2.2μF
2.4μF
Decrease primarily due
to DC bias (VIN) and
elevated temperature
Murata or Equivalent GRM155R60G475M
1.6μF
4.7μF
5.2μF
Decrease primarily due
to DC bias (VOUT)
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
13
FAN5361 — 6MHz, 600mA TinyBuck™ 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 FAN5361, it is important to place a low-ESR
input capacitor very close to the IC, as shown in Figure 41.
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 FAN5361 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.
VIN
470nH
A1
A2
B1
B2
C1
C2
CIN
GND
COUT
VOUT
Figure 41. PCB Layout Guidance
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
14
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
PCB Layout Guidelines
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Physical Dimensions
F
BALL A1
INDEX AREA
A
E
SOLDER MASK
OPENING
B
0.40
A1
(Ø0.180)
CU PAD
0.03 C
2X
0.80
D
(1.080)
F
0.03 C
(R0.140)
(0.680)
2X
TOP VIEW
RECOMMENDED LAND PATTERN (NSMD)
0.06 C
0.378±0.018
0.625
0.547
0.05 C
E
0.208±0.021
SEATING PLANE
C
SIDE VIEWS
D
NOTES:
Ø0.260±0.010
0.40
6X
0.005
C
B
0.40
(Y) +/-0.018
A
0.80
C A B
1 2
F
(X) +/-0.018
A. NO JEDEC REGISTRATION APPLIES.
B. DIMENSIONS ARE IN MILLIMETERS.
C. DIMENSIONS AND TOLERANCES PER
ASMEY14.5M, 1994.
D. DATUM C, THE SEATING PLANE IS DEFINED
BY THE SPHERICAL CROWNS OF THE BALLS.
E. PACKAGE TYPICAL HEIGHT IS 586 MICRONS
±39 MICRONS (547-625 MICRONS).
F. FOR DIMENSIONS D, E, X, AND Y SEE
PRODUCT DATASHEET.
BOTTOM VIEW
G. BALL COMPOSITION: Sn95.5-Ag3.9-Cu0.6.
H. DRAWING FILENAME: UC006ACrev1.
Figure 42. 6-Bump WLCSP, 0.4mm Pitch
Product Specific Dimensions
Product
D
E
X
Y
FAN5361UCX
1.390 +/-0.030
0.990 +/-0.030
0.295
0.295
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/.
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
15
0.10 C
2.0
2X
A
B
1.60
1.50
2.0
6
4
0.50
0.10 C
2X
PIN1
IDENT
1.10
1.40
TOP VIEW
1
0.55 MAX
3
0.65
0.10 C
0.08 C
2.40
0.30
(0.15)
RECOMMENDED LAND PATTERN
0.05
0.00
C
SEATING
PLANE
SIDE VIEW
NOTES:
PIN1
IDENT
1
1.50
MAX
A. OUTLINE BASED ON JEDEC REGISTRATION
MO-229, VARIATION VCCC.
3
B. DIMENSIONS ARE IN MILLIMETERS.
6x
1.10
MAX
0.35
0.25
6
4
0.65
C. DIMENSIONS AND TOLERANCES PER
ASME Y14.5M, 1994.
D. DRAWING FILENAME: MKT-UMLP06Crev1
0.35
6x
0.25
1.30
0.10 C A B
0.05 C
BOTTOM VIEW
Figure 43. 6-Pin UMLP
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/.
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
16
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
Physical Dimensions
FAN5361 — 6MHz, 600mA TinyBuck™ Synchronous Buck Regulator
© 2008 Fairchild Semiconductor Corporation
FAN5361 • Rev. 1.0.0
www.fairchildsemi.com
17
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