FAN53611AUC18X - ON SEMICONDUCTOR

December-2017, Rev. 2 FAN53611/D

FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

FAN53601 / FAN53611

6 MHz, 600 mA / 1 A Synchronous Buck Regulator

Features

 600 mA or 1 A Output Current Capability

 24 µA Typical Quies cent Cur rent

 6 MHz Fixed-Frequency Operation

 Best-in-Class Load Trans ient Response

 Best-in-Class Efficiency

 2.3 V to 5.5 V Input Voltage Range

 Low Ripple Light-Load PFM Mode

 Forc ed PWM and Ex ternal Clock Sync hronization

 Internal Soft-Start

 Input Under-Voltage Loc kout (UV LO)

 Thermal Shutdown and Overload Protection

 Optional Output Discharge

 6-Bump WLCSP, 0.4 mm Pitc h

Applications

 3G, 4 G, WiFi®, WiMA X™, and WiBro® Data Cards

 Tablets

 DSC, DVC

 Netbooks®, Ultra-Mobile PCs

All tr ademar k s ar e the pr oper ty of their r especti ve own er s .

Description

The FAN53601/11 is a 6 MHz, step-down switching voltag e

regulator, av ail ab le in 6 00 mA o r 1 A optio ns, that de liver s a

fixed output from an input voltage supply of 2.3 V to 5.5 V.

Using a proprietary architecture with synchronous

rectification, the FA N53601/11 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 reduc es the v alue of the exter na l c o mpon ents

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 ty pic al qu iesc ent cur rent of 24 µA. Ev en with suc h a

low quiescent current, the part exhibits excellent transient

response during large load sw ings. At higher loads, the

system automatically switches to fixed-frequency control,

operating at 6 MHz. In Shutdow n Mode, the supply current

drops below 1 µA, reducing power consumption. For

appl ic ations tha t req uire mi ni mu m ripp le or f ixed fr equency ,

PFM Mode c an be disabled us ing the MODE pin.

The FAN53601/11 is available in 6-bu mp, 0.4 mm pitch,

Wafer-Level C hip-Scale Package (WLCSP).

Figure 1. Typical Application

MODE

GND

CIN

2.2µF

470nH

4.7µFCOUT

VIN

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Ordering Information

Part Number

Output

Voltage(1)

Max. Output

Current

Active

Discharge(2)

Max.

VIN Package

Temperature

Range Packing

FAN53601AUC10X

1.000 V

600 mA

Yes

5.5 V WLCSP-6,

0.4 mm Pitch -40 to +85° C

Tape and

Reel

FAN53601AUC105X

1.050 V

600 mA

Yes

FAN53611AUC11X

1.100 V

1 A

Yes

FAN53611AUC115X

1.150 V

1 A

Yes

FAN53611AUC13X

1.300 V

1 A

Yes

FAN53611AUC135X

1.350 V

1 A

Yes

FAN53611UC123X

1.233 V

1 A

FAN53601UC182X

1.820 V

600 mA

FAN53611AUC205X

2.050 V

1 A

Yes

FAN53611AUC123X

1.233 V

1 A

Yes

FAN53611AUC12X

1.200 V

1 A

Yes

FAN53611AUC18X

1.800 V

1 A

Yes

Notes:

1. Other v oltage options available on r equest. Contac t a ON Semiconductor representative.

2. All voltage and output current options are available with or without active discharge. Contact a ON Semiconductor

representative.

Pin Configurations

MODE

VIN

GND

A2MODE

VIN

GND

Figure 2. Bum ps Facing Down Figure 3 . Bum ps Facing Up

Pin Definitions

Pi n # Name Description

A1 MODE

MODE. Logic 1 on this pin f orc es the IC to s tay in PWM Mode. A logic 0 allow s the IC to

automatically s witch to PFM during light loads. The regulator also s ync hronizes its s witching

frequency to four times the fr equency pr ovided on this pin. Do not leave this pin f loating.

Switching N ode. Connect to output inductor.

Feedba c k / V

OUT

. Connect to output voltage.

GND

Ground. Power and IC ground. A ll s ignals ar e refer enced to this pin.

B2 EN

Enable. The dev ic e is in Shutdown Mode w hen voltage to this pin is <

0.4

V and enabled when

> 1.2 V . Do not leave this pin f loating.

VIN

I nput Voltage. Connect to input pow er source.

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Absolute Maximum Ratings

Stres ses ex ceeding the absolute max imu m ratings may da mage the dev ic e. The dev ic e may not f unc tion or be operable above

the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended

expos ure to s tresses above the r ecommended op erating conditi ons may af f ect dev ic e reliability . The absolut e max imum ratin gs

are stress ratings only.

Symbol Parameter Min. Max. Units

Input Voltage

-0.3

7.0

Voltage on SW Pin

-0.3

+ 0.3(3)

CTRL

EN an d MO DE Pi n Voltage

-0.3

+ 0.3(3)

Other Pins

-0.3

+ 0.3(3)

ESD Electrostatic Discharge

Protection Level

Human Body Model per JESD22-A114

2.0

Charged Device Model per JESD22-C101

1.5

Junction Temperature

-40

+150

°C

STG

Storage Temperature

-65

+150

°C

Lead Solder ing Temperatur e, 10 Sec onds

+260

°C

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 s pecified to ens ure optimal performance to the datas heet spec if ications. ON Semic onductor does not recommend

exceeding them or designing to Absolute M axim um R atings.

Symbol

Parameter

Min.

Typ.

Max.

Units

Supply V oltage Range

2.3

5.5

IOUT

Output Current for FAN53601

600

Output Current for FAN53611

Inductor

470

Input Capacitor

2.2

µF

OUT

Output Capacitor

1.6

4.7

12.0

µF

Operating Ambient Temperature

-40

+85

°C

Operating Junction Temperature

-40

+125

°C

T he rmal Prope rtie s

Junction-to-a mbient th ermal res is tance is a f unc tion of application and board layout. This data is measur ed with four-layer 2s2p

boards in accordance to JEDEC standard JESD51. Special attention must be paid to not exceed junction temperature TJ(max) at a

gi ven ambient temperature TA.

Symbol Parameter Typical Unit

θJA Junction-to-Ambient Thermal Resistance 125 °C/W

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Elect rical C har acte r istics

Mini mu m an d maxi mu m v alues are at V IN = VEN = 2.3 V to 5.5 V, VMODE = 0 V (AUTO Mode), TA = -40 ° C to +85 ° C; c ir c uit of

Figure 1 , unless otherw ise noted. Typical values are at TA = 25°C, VIN = VEN = 3.6 V.

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Units

Power Supplies

IQ Quiescent Current No Load, No t S w itching 24 50 µA

PWM Mode 8 mA

(SD)

Shutdown Supply Current

EN = GND, V

= 3.6 V

0.25

1.00

µA

VUVLO Under-V oltage Loc kout Thr eshold Rising VIN 2.15 2.27 V

VUVHYST Under-Voltage Lockout Hysteresis 200 mV

Logi c I nputs: EN a nd MODE Pins

VIH Enable HIGH-Level Input Voltage 1.2 V

Enable LOW-Level Input Voltage

0.4

VLHYST Logic Input Hysteresis Voltage 100 mV

IIN Enable Input Leakage Current Pin to VIN or GND 0.01 1.00 µA

Switching and Synchroni zation

fSW Sw itching Frequency(4) VIN = 3.6 V, TA = 25°C, PWM

Mode, ILOAD = 10 mA 5.4 6.0 6.6 MHz

fSYNC MODE Synchronization Range

(4)

Square Wave at MO DE Input 1.3 1.5 1.7 MHz

Regulation

VO Output Voltage

Accuracy

1.000 V ILOAD = 0 to 600 mA 0.953 1.000 1.048

PWM Mode 0.967 1.000 1.034

1.35 V

LOAD

= 0 to 1 A

1.298

1.350

1.402

PWM mode 1.309 1.350 1.391

1.233 V ILOAD = 0 to 1 A 1.185 1.233 1.281

PWM Mode

1.192

1.233

1.274

1.820 V ILOAD = 0 to 600 mA 1.755 1.820 1.885

PWM Mode 1.781 1.820 1.859

1.100 V

LOAD

= 0 to 1 A

1.054

1.100

1.147

PWM Mode 1.061 1.100 1.140

1.300 V ILOAD = 0 to 1 A 1.250 1.300 1.350

PWM Mode

1.259

1.300

1.341

1.150 V ILOAD = 0 to 1 A 1.104 1.150 1.196

PWM Mode 1.110 1.150 1.190

1.050 V ILOAD = 0 to 600 mA 1.003 1.050 1.097

PWM Mode 1.016 1.050 1.084

2.050 V ILOAD = 0 to 1 A, VIN = 2.7 V to

5.5 V 1.973 2.050 2.127

PWM Mode, VIN = 2.7 V to 5.5 V 2.004 2.050 2.096

1.200 V ILOAD = 0 to 1 A 1.152 1.200 1.248

PWM Mode 1.160 1.200 1.240

1.800 V ILOAD = 0 to 1 A 1.732 1.800 1.868

PWM Mode 1.756 1.800 1.844

tSS Soft-Start VIN = 4.5 V, From EN Rising Edge 180 300 µs

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Elect rical C har acte r istics (Continued)

Mini mu m an d maxi mu m v alues are at V IN = V EN = 2.3 V to 5.5 V, VM ODE = 0 V (AUTO Mode), TA = -

40 ° C to +85 ° C; c ir cuit of

Figure 1 , unless otherwise noted. T ypi cal val ues are at T A = 25°C, VIN = VEN = 3.6 V.

Symbol

Parameter

Conditions

Min.

Typ.

Max.

Units

Output Driver

RDS(on) PMOS On Res is tance VIN = V GS = 3.6 V 175 mΩ

NMOS On Res is tance

= V

= 3.6 V

165

mΩ

ILIM(OL) PMOS Peak Current Limit

Open-Loop for F AN53601,

VIN = 3.6 V, TA = 25°C 900 1100 1250 mA

Open-Loop for FAN53611,

VIN = 3.6 V, TA = 25°C 1500 1750 2000 mA

RDIS Output Discharge Resistance EN = GND 230 Ω

TSD

Thermal Shutdown

150

°C

THYS Thermal Shutdown Hys teres is 15 °C

Notes:

4. Limited by the effec t of tOFF minimum ( see O per ati o n D esc r ipt io n secti on ) .

5. The Electr ical C har acter istics table r efle cts open-loop data. R efer to the Oper ati o n D esc r ipt io n and Ty pica l C har acter istics Sec t io ns for

closed-loop data.

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Typical P e rformance C har acter istics

U nless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), V OUT = 1.82 V, and TA = 25°C.

70%

75%

80%

85%

90%

95%

0200 400 600 800 1000

Efficiency

Load Current (mA)

2.7 VIN

3.6 VIN

4.2 VIN

5.0 VIN

60%

62%

64%

66%

68%

70%

72%

74%

76%

78%

80%

82%

84%

86%

88%

90%

92%

0200 400 600 800 1000

Efficiency

Load Current (mA)

-40C, AUTO

+25C, AUTO

+85C, AUTO

-40C, PWM

+25C, PWM

+85C, PWM

Figure 4. Efficiency vs . Load Curre nt and

Input Voltage, Auto Mode, Dotted for Decreasing Load Figure 5. Efficiency vs . Load Curre nt

and Temperature, A uto Mode, Dotted for FPW M

64%

66%

68%

70%

72%

74%

76%

78%

80%

82%

84%

86%

88%

90%

0200 400 600 800 1000

Efficiency

Load Current (mA)

2.7 VIN

3.6 VIN

4.2 VIN

5.0 VIN

60%

62%

64%

66%

68%

70%

72%

74%

76%

78%

80%

82%

84%

86%

88%

90%

0200 400 600 800 1000

Efficiency

Load Current (mA)

-40C, AUTO

+25C, AUTO

+85C, AUTO

-40C, PWM

+25C, PWM

+85C, PWM

Figure 6. Efficiency vs . Load Curre nt and

Input Voltage , VOUT = 1.23 V, Auto Mode, Dotte d

for Decreasing Load

Figure 7. Efficiency vs . Load Curre nt

and Temperature, VOUT = 1.23 V, Auto M ode,

Dotted for FP WM

-2

-1

0100 200 300 400 500 600

Output R e gula tion ( %)

Load Current (mA)

2.7VIN, AUTO

3.6VIN, AUTO

4.2VIN, AUTO

5.0VIN, AUTO

2.7V IN, PWM

3.6V IN, PWM

4.2V IN, PWM

5.0V IN, PWM

64%

66%

68%

70%

72%

74%

76%

78%

80%

82%

84%

86%

88%

90%

0100 200 300 400 500 600

Efficiency

Load Current (mA)

2.7 VIN

3.6 VIN

4.2 VIN

5.0 VIN

Figure 8. Output Regulation vs. Load Current,

VOUT = 1.00 V, Dotted for Auto Mode Figure 9. Efficiency vs. Load Curr ent, VOUT = 1.00 V,

Dotted for Decreasing Load

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Typical P e rformance C har acter istics (Continued)

Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), V OUT = 1.82 V, and TA = 25°C.

-2

-1

0200 400 600 800 1000

Output Regulation (%)

Load Current (mA)

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

-1

0200 400 600 800 1000

Output Regulation (%)

Load Current (mA)

2.7VIN, AUTO

3.6VIN, AUTO

4.2VIN, AUTO

5.0VIN, AUTO

2.7VIN, PWM

3.6VIN, PWM

4.2VIN, PWM

5.0VIN, PWM

Figure 10. ∆VOUT (%) v s. L oad Current and In put

Voltage, Nor m aliz e d to 3.6 VIN, 500 mA Load, FPWM ,

Dotted for Auto Mode

Figure 11. ∆VOUT (%) vs. Load Current and Input

V oltage , V OUT = 1.23 V, Normalized to 3.6 VIN, 500 mA

Load, FPWM, Dotted for Auto Mode

100

150

200

250

300

350

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Load Current (mA)

Input Voltage (V)

PWM

PFM

100

150

200

250

300

350

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Load Current (mA)

Input Voltage (V)

PWM

PFM

Figure 12. PFM / PWM Boundary vs. Input Voltage

Figure 13. PFM / PWM Boundary vs. Input Voltage ,

VOUT = 1.23 V

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Input Cur rent (µA)

Input Voltage (V)

-40C, EN=VIN

+25 C , EN=VIN

+85 C , EN=VIN

-40C, EN=1.8V

+25C, EN=1.8V

+85C, EN=1.8V

2.5 3.0 3.5 4.0 4.5 5.0 5.5

Input Current (mA)

Input Voltage (V)

-40C

+25C

+85C

Figure 14. Quies ce nt Curre nt vs. Input V oltage and

Temperature, Auto Mode; EN = VIN Solid, Dotte d for

EN=1. 8 V (-40oC, +25oC, +85oC)

Figure 15. Quies ce nt Curre nt vs. Input V oltage and

Temperature, Mode = EN = VIN (FPWM)

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Typical P e rformance C har acter istics (Continued)

U nless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), V OUT = 1.82 V, and TA = 25°C.

0200 400 600 800 1000

Output Ripple (mVpp)

Load Current (mA)

2.7VIN, AUTO

3.6VIN, AUTO

5.0VIN, AUTO

2.7VIN, PWM

3.6VIN, PWM

5.0VIN, PWM

1,500

3,000

4,500

6,000

7,500

0200 400 600 800 1000

Switching Frequency (KHz)

Load Current (mA)

2.7VIN, AUTO

3.6VIN, AUTO

5.0VIN, AUTO

2.7VIN, PWM

3.6VIN, PWM

5.0VIN, PWM

Figure 16. Output Ripple vs. Load Current and

Input Voltage , FPWM, Dotted for Auto Mode

Figure 17. Frequency vs. Load Curre nt and

Input Voltage , Auto Mode , Dotted for FPW M

Figure 18. Load Transient, 10-200-10 m A, 100 ns Edge Figure 19. Load Transient, 200-800-200 mA,

100 ns Edge

Figure 20. Line Tr ans ie nt, 3.3-3.9-3.3 VIN, 10 µs Edge,

36 m A Load Figure 21. Line Transient, 3.3-3.9-3.3 VIN, 10 µs Edge,

600 mA Loa d

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Typical P e rformance C har acter istics (Continued)

U nless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), V OUT = 1.82 V, and TA = 25°C.

Figure 22. Com bine d Line / Load Transient, 3.9-3.3 V

10 µs Edge, 36-400 m A Load, 100 ns Edge

Figure 23. Com bine d Line / Load Transient, 3.3-3.9 V

10 µs Edge, 400-36 mA Lo ad, 100 ns Edge

Figure 24. Startup, 50 Ω Load Figure 25. Startup, 3 Ω Load

Figure 26. Shutdown, 10k Ω Load, No Output Discharge

Figure 27. Shutdown, No Load, Output Discharge

Enabled

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

T ypical Pe rfor mance Characteristics (Continued)

U nless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), V OUT = 1.82 V, and TA = 25°C.

Figure 28. Over-Current, Load Increasing Past

Current Limit, FAN5360 1 Figure 29. 250 m Ω Fault , Rapid Fault,

Hiccup, FAN53601

Figure 30. Over-Cur re nt, Load Increasing Past

Current Limit, FAN5361 1

Figure 31. 250 mΩ Fault, Rapid Fault,

Hiccup, FAN53611

0.1 110 100 1000

PSRR (dB)

Frequency (KHz)

36mA Load

600mA Load

0.1 110 100 1000

PSRR (dB)

Frequency (KHz)

24mA Load

500mA Load

Figure 32. PSRR, 50 Ω and 3 Ω Load Figure 33. PSRR, 50 Ω and 3 Ω Load, VOUT = 1.23 V

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Operation Description

The FAN53601/11 is a 6 MHz, step-down switching volta ge

regulator av aila ble i n 6 00 mA o r 1 A o pti ons that deliver s a

fixed output from an input voltage supply of 2.3 V to 5.5 V.

Using a proprietary architecture w ith 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 reduc es the v alue of the exter na l c o mpo nents

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

sy nchr oniz ed to an ex ternal f requenc y s ourc e.

Control S cheme

The FAN53601/11 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,

allow ing for the use of ceramic output capacitors. Although

this type of operati on normally results in a swi tching frequency

that varies w ith input voltage and load current, an internal

f requency loop holds the switc hing f r equency cons tant ov er a

l arge range of input voltages and load currents.

For very light loads, the FAN53601/11 operates in

Discontinuous Current Mode (DCM) single-pu lse PFM Mode,

w hich pr oduces low output ri pple c o mp ared w ith other PFM

architectures. Transition between PWM and PFM is

seamless, allowing for a smooth transition betw een DCM

and CCM.

Combined w ith exceptional transient response

characteristics, the very low quiescent current of the

controller mai nta ins high eff iciency ; even at ver y lig ht l oads ;

while preserving fast transient response for applications

requiring tight output regulation.

E nable and S oft-Start

When EN is LOW, all circuits are off and the IC draw s

~250 nA of current. When EN is HIGH and VIN is above its

UVLO threshold, the regulator begins a soft-start cycle. The

output ra mp during sof t-s tart is a f ixed s lew r ate of 50 mV/µs

from Vout = 0 to 1 V, 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 w hen COUT is charged.

In addit ion, a ll voltage options c an be order ed with a f eature

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 s hape to prev ent ov ers hoot of the output voltage. Current

limiting minimizes inrush during soft-start.

The c urrent-l imi t f ault respons e pro tec ts the IC in the ev ent

of an over-current condition present during soft-start. As a

res ult, the IC may f ail to start if heavy loa d is applie d duri ng

startup and/or if ex ces sive COUT is used.

The current required to charge COUT during soft-start

commonly referred to as “displacement current” is given as:

OUTDISP

•=

(1)

where

refers to the soft-start slew rate.

To prev ent shut dow n dur ing s of t-s tart, the f ollowing condition

must be met:

)DC(MAXLOADDISP

I I I <+

(2)

where IMAX(DC) is the maximum load current the IC is

guaranteed to support.

Startup into Larg e 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 FA N53601/11 s tarts approp riately. The I C

shuts dow n for 1.3 ms w hen IDISP exceeds ILIMIT for more

than 200 µs of current limit. The IC then begins a new soft-

start c yc le. Since COUT retains its charge w hen the IC is o ff,

the IC reaches regulation after multiple soft-start attempts.

MODE Pin

Logic 1 on this pin forces the IC to stay in PWM Mode. A

logic 0 al low s the IC to automatically sw itch to PFM during

light loads. If the MODE pin is toggled w ith a frequency

betw een 1.3 MHz and 1.7 MHz, the converter synchronizes

its sw itching frequency to four times the frequency on the

MODE pin.

The MODE pin is internally buffered w ith a Schmitt trigger,

which all ows the MODE pi n to be drive n w ith slow rise an d

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.

Current L imit, Fault S hutdown, and Restart

A heavy load or short circuit on the output causes the current

in the induc tor to incr ease un til a maxi mum current threshold

is r eached in the high-side sw itch. Upon r eachi ng this poi nt,

the high-side sw itch tur ns o ff, prev enting high cur rents fr om

caus ing damage. The reg ulator continues to li mit the c urr ent

cycle-by-cyc le. A fter 16 c yc les of cur rent limit, the reg ulator

triggers an over-current fault, causing the regulator to shut

dow n for about 1.3 ms before attempting a restart.

If the fault is caused by short circuit, the soft-start circuit

attempts to restart and produces an over-current fault after

about 200 µs, w hich results in a duty cycle of less than 15%,

limiting pow er 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.

Under-Voltag e L ockout (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.

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

T herm al Shutd own (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 nom inally 150°C with a 15°C hysteresis.

Minimum Off-Time Effect on Switching

Frequency

tOFF(MIN) is 40 ns. This impos es c onstr aints on t he maxi mu m

OUT

that the FAN53601/11 can provide or the maximum

output v oltage it c an prov ide at low VIN w hile maintaining a

fixed switchi ng frequency in PWM Mode.

When VIN is LOW, f ixed switching is mai nta ined as lo ng as :

7.01 )( ≈•−≤ SWMINOFF

OUT ft

The switching frequency drops when the regulator cannot

prov ide s uf f icient duty c yc le at 6 MHz to mai ntain regul ati on.

This occurs when VOUT is 1.82 V and VIN is below 2.7 V at

high load currents (see Figure 34).

1,500

3,000

4,500

6,000

7,500

0200 400 600 800 1000

Switching Frequency (KHz)

Load Current (mA)

2.7VIN, AUTO

2.3VIN, AUTO

2.7VIN, PWM

2.3VIN, PWM

Figure 34. Fre quency vs. Load Curre nt to

Demonstrate tOFFMIN Effect, VIN = 2.3 V and 2.7 V,

VOUT = 1.82 V, Au to Mode, FPWM Dotted

The calculation for switching frequency is given by:













=MHz

MAXSW

6 ,

min

)(

(3)

where:













−•−

•+

+•=

OUTONOUTIN

OFFOUTOUT

MAXSW

VRIV RIV

nst140

)(

)

where:

OFF

LNDSON DCRR +

LPDSON DCRR +

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

Applications Information

Selecting the Inductor

The o utput ind uctor mus t meet b oth the re quired ind uc tanc e

and the energy-handling capability of the application. The

inductor value affects average current limit, the PWM-to-

PFM trans ition point, output voltage ripple, and ef f ic iency.

The ripple current (∆I) of the regulator is:













•

−

•≈

∆

OUTIN

OUT

LVV

(5)

The maximum average load current, IMAX(LOAD), is related to

the peak c urrent limit, ILIM(PK), by the ripple current, given by:

)PK(LIM)LOAD(MAX

∆

−=

(6)

The transition betw een PFM and PWM operation is

determined by the point at which the in ductor val ley curr ent

crosses zero. The regulator DC current when the inductor

current crosses zero, IDCM, is:

DCM

∆

(7)

The FAN53601/11 is opti mized for oper ation with L = 470 nH,

but is stable w ith inductances up to 1 µH (nominal). The

inductor s hould be r ated to mai ntain at least 80% of its v alue

at ILIM(PK).

Efficiency is affected by the inductor DCR and inductance

value. Decr easing the induc tor v alue f or a giv en phys ic al size

typically decreases the DCR; but because ∆I increases, the

R M S current increases, as do the core and skin effect losses.

I I 2

)DC(OUTRMS ∆

(8)

The increased RMS current produces higher losses through

the RDS(ON) of the I C M OSFE Ts, as well as the inductor DCR.

Inc reasi ng the ind uctor value pro duc es lower RMS cur rents ,

but degrades transient response. For a given physical

inductor size, increased inductance usually results in an

inductor w ith lower saturation current and higher DCR.

Table 1 shows the effects of inductance higher or lower than

the rec ommended 1 µH on r egulator performanc e.

Output C apacito r

Table 2 suggests 0402 capacitors. 0603 capacitors may

f urther impr ove perfor manc e in that the ef fective c apacitanc e

i s higher. This improves transient response and output r ipple.

Increasing COUT has no effect on loop stability and can

therefore be increased to reduce output voltage ripple or to

i mprove transient response. Output voltage ripple, ∆VOUT, is:

()













⋅⋅

−⋅⋅

⋅⋅

∆=∆

OUTSW

LOUT

Cf8 1

D1D2 ESRCf

(9)

Input C apacit or

The 2.2 µF ceramic input capacitor should be placed as

close as possible between the VIN pin and GND to minimize

the par asitic 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 pow er

source lead to reduce the ringing that can occur between the

inductance of the pow er source leads and CIN.

The ef f ec tive capac itanc e value dec reas es as V IN increases

due to DC bias effects.

Table 1. Effects of Changes in Inductor Value (from 470 nH Recommended Value) on R egulator Performance

I nductor V al ue IMAX(LOAD) ∆VOUT Transi ent Response

Increase

Decrease

Degraded

Decrease

Increase

Improved

Table 2. Rec ommended Passi v e Components and their Variation Due to D C Bias

Component

Description

Vendor

Min.

Typ.

Max.

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 µF, 6.3 V,

X5R, 0402 Murata or Equivalent GRM155R60J 225ME15

GRM188R60J225KE19D 1.0 µF 2.2 µF

COUT

4.7 µF, X5R,

0402

Murata or Equivalent GRM155R60G475M

GRM155R60E475ME760 1.6 µF 4.7 µF

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FAN53601 / FAN53611 — 6 MHz 600 mA / 1 A Synchronous Buck Regulator

PCB Layout Guidelines

There are only three external components: the inductor and

the input and output capacitors. For any buck switcher IC,

i ncluding the FAN53601/11, it is important to place a low-ESR

input capacitor very close to the IC, as shown in Figure 35.

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 aw ay from the IC; in that case,

VOUT should be considered at the COUT terminal.

Figure 35. PCB Layout Guidance

T he followin g inf or mat ion app lies to th e WL CS P package dim ensio ns on th e next pag e:

Product-Specific Dimensions

D E X Y

1.160 ±0.030

0.860 ±0.030

0.230

0.180

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FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator

Physical Dimensions

SEATING PLANE

0.06 C

0.05 C

SIDE VIEWS

NOTES:

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.

G. DRAWING FILENAME: UC006ACrev4.

BOTTOM VIEW

TOP VIEW RECOMMENDED LAND PATTERN

(NSMD PAD TYPE)

BALL A1

INDEX AREA A1

0.03 C

0.208±0.021

0.378±0.018

0.40

0.005 C A B

(X) +/-0.018

(Y) +/-0.018

Ø0.260±0.010

0.40

F0.40

(Ø0.20)

Cu Pad

(Ø0.30)

Solder Mask

Opening

0.625

0.547

Figure 36. 6-Bump WLCSP, 0.4 mm Pitch

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FAN53601 / FAN53611 — 6 MHz, 600 mA / 1 A Synchronous Buck Regulator

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