Fairchild FAN53540 service manual

February 2012

FAN53540

2.4MHz, 5A TinyBuck™ Synchronous Buck Regulator

FAN53540 — 2.4MHz, 5A TinyBuck™ Synchronous Buck Regulator

Features

 2.4MHz Fixed-Frequency Operation
 Best-in-Class Load Transient Response

 5A Output Current Capability
 2.7V to 5.5V Input Voltage Range

 Adjustable Output Voltage: 0.8V to V

IN

•0.9

 PFM Mode for High Efficiency in Light Load

(Forced PWM Available on MODE Pin)

 50µA Typical Quiescent Current in PFM Mode

 External Frequency Synchronization
 Low Ripple Light-Load PFM Mode with Forced

PWM Control

 Power Good Output

 Internal Soft-Start
 Input Under-Voltage Lockout (UVLO)

 Thermal Shutdown and Overload Protection
 No External Compensation Required

 20-Bump WLCSP

Applications

 Set-Top Box

 Hard Disk Drive
 Communications Cards

 DSP Power

Description

The FAN53540 is a step-down switching voltage regulator
that delivers an adjustable output from an input voltage
supply of 2.7V to 5.5V. Using a proprietary architecture with
synchronous rectification, the FAN53540 is capable of
delivering 5A at over 90% efficiency, while maintaining a
very high efficiency of over 80% at load currents as low as
2mA. The regulator operates at a nominal fixed frequency of

2.4MHz, which reduces the value of the external
components to 470nH for the output inductor and 20µF for
the output capacitor. Additional output capacitance can be
added to improve regulation during load transients without
affecting stability and inductance up to 1.2µH may be used
with additional output capacitance.

At moderate and light loads, pulse frequency modulation
(PFM) is used to operate the device in power-save mode
with a typical quiescent current of 50µA. 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 2.4MHz. In shutdown mode, the supply current
drops below 1µA, reducing power consumption. PFM mode
can be disabled if constant frequency is desired. The
FAN53540 is available in a 20-bump 1.96mm x 1.56mm
Wafer-Level Chip-Scale Package (WLCSP).

PGOOD

SW

0.47H

GND

VOUT

FB

L1

R2

C

OUT

10F

R1

C

OUT

10F

C

IN

10F

VIN

C

10nF

EN

MODE

IN1

FAN54540

Figure 1. Typical Application

Ordering Information

Part Number Temperature Range Package Packing Method

FAN53540UCX -40 to 85°C

© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN53540 • Rev. 1.0.2

20-Ball Wafer-Level, Chip-Scale Package (WLCSP),
4x5 Array, 0.4mm Pitch, 250µm Ball

Tape and Reel

FAN53540 — 2.4 MHz, 5A TinyBuck™ Synchronous Buck Regulator

Recommended External Components

Table 1. Recommended External Components for 5A Maximum Load Current

Component Description Vendor Parameter Typical Unit

L1 470nH Nominal

C

OUT

CIN

C

10nF, 25V, X7R, 0402 Any C 10 nF

IN1

10F, 6.3V, X5R, 0805, 2 Pieces

10F, 6.3V, X5R, 0805

GRM21BR60J106M (Murata)

See Table 2

C2012X5R0J106M (TDK)

L

C 10

0.47

H

F

Table 2. Recommended Inductors

Component Dimensions

Manufacturer Part# L (nH) DCR (mΩ)I

Bourns SRP5012-R47M 470 19 6.0 5.1 4.5 1.2

Bourns SRP4012-R47M 470 20 5.5 4.6 4.0 1.2

Coilcraft XPL4020-471ML 470 19 7.2 4.2 4.2 2.0

Inter-Technical

TDK VLC5020T-R47M 470 15 5.4 5.0 5.0 2.0

Vishay IHLP1616ABERR47M01 470 20 5.0 4.5 4.1 1.2

Notes:

1. I

MAXDC

2. Inductor used for efficiency and temperature rise measurements.

(2)

SC2511-R47M 470 2.6 16.0 6.5 6.5 3.0

is the lesser current to produce 40oC temperature rise or 30% inductance roll-off.

MAXDC

(1)

L W H

© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN53540 • Rev. 1.0.2 2

Pin Configuration

FAN53540 — 2.4 MHz, 5A TinyBuck™ Synchronous Buck Regulator

PGOOD

MODE

EN FB VOUT

A1 A2

B1

C1

VIN SW

D1 D3D2

E1 E3E2 E4

B2

C2

A3

GND

B3

C3

A4

B4

C4

D4

Figure 2. Top View Figure 3. Top View Bottom View

Pin Definitions

Bump # Name Description

A1 PGOOD

A2 EN

A3 FB

A4 VOUT

B1 MODE

B2, B3,

C1 – C4

GND

B4 AGND

D1, D2,

E1, E2

D3, D4,

E3, E4

VIN

SW

Power Good. This open-drain pin pulls LOW if the output falls out of regulation or is in soft-start.

Enable. The device is in Shutdown Mode when this pin is LOW. Do not leave this pin floating. When

tying HIGH, use at least a 1kΩ series resistor if V

is expected to exceed 4.5V.

IN

FB. Connect to resistor divider. The IC regulates this pin to 0.8V.

VOUT. Sense pin for V

. Connect directly to C

OUT

OUT

.

MODE / SYNC. A logic 0 allows the IC to automatically switch to PFM during light loads. When held
HIGH, the IC to stays in PWM Mode. The regulator also synchronizes its switching frequency to four
times (4X) the frequency provided on this pin (f
use at least a 1kΩ series resistor if V

is expected to exceed 4.5V.

IN

). Do not leave this pin floating. When tying HIGH,

MODE

Ground. Low-side MOSFET is referenced to this pin. C
path to these pins.

Analog Ground. All signals are referenced to this pin. Avoid routing high dV/dt AC currents through
this pin.

Power Input Voltage. Connect to input power source. Connect to C

Switching Node. Connect to inductor.

A4

B4

C4

D4

and C

IN

B2

C2

A1

B1

C1

D1D3 D2

E1E3 E2E4

A3 A2

B3

C3

should be returned with a minimal

OUT

with minimal path.

IN

© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN53540 • Rev. 1.0.2 3

FAN53540 — 2.4 MHz, 5A TinyBuck™ Synchronous Buck Regulator

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above
the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended
exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum
ratings are stress ratings only.

Symbol Parameter Min. Max. Unit

SW, VIN Pins -0.3 7.0

VIN

ESD

Other Pins

Electrostatic Discharge
Protection Level

Tied without Series Impedance -0.3 4.5
Tied through Series Resistance ≥100

-0.3 V

Human Body Model per JESD22-A114 2250

Charged Device Model per JESD22-C101 1500

TJ Junction Temperature –40 +150 °C

T

Storage Temperature –65 +150 °C

STG

TL Lead Soldering Temperature, 10 Seconds +260 °C

Note:

3. V

4. Lesser of 7V or V

slew rate is limited to 1V/µs.

IN

+0.3V.

IN

(3)

V

IN

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 Min. Typ. Max. Unit

VIN Supply Voltage Range 2.7 5.5 V

V

Output Voltage Range 0.8 90% Duty Cycle V

OUT

I

Output Current 0 5 A

OUT

L Inductor 0.47 1.20 µH

CIN Input Capacitor 10 µF

C

Output Capacitor 20

OUT

TA Operating Ambient Temperature -40 +85 °C

TJ Operating Junction Temperature -40 +125 °C

μF

Thermal Properties

Symbol Parameter Typical Unit

(5)

JA

Junction-to-Ambient Thermal Resistance 38

Note:

5. See Thermal Considerations in the Applications section.

°C/W

© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN53540 • Rev. 1.0.2 4

Electrical Characteristics

Minimum and maximum values are at V

=25°C, VIN=5V, and V

T

A

OUT

=1.2V.

Symbol Parameter Condition Min. Typ. Max. Unit

Power Supplies

IQ Quiescent Current

I

Shutdown Supply Current EN=GND 0.1 10 µA

SD

V

Under-Voltage Lockout Threshold

UVLO

V

Logic Pins

V

Power Switch and Protection

R

R

Frequency Control

Soft-Start and Output Discharge

Under-Voltage Lockout Hysteresis 365 mV

UVHYST

VIH High-Level Input Voltage 1.05 V

VIL Low-Level Input Voltage 0.4 V

V

Logic Input Hysteresis Voltage 140 mV

LHYST

IIN Input Bias Current Input Tied to GND or 1ΩK Resistor to VIN 0.01 1.00 µA

I

PGOOD Pull-Down Current V

OUTL

I

PGOOD HIGH Leakage Current V

OUTH

Regulation

OUT

V



IV



I

V

DS(ON)P

DS(ON)N

I

LIMPK

T

T

V

SDWN

Output Reference DC Accuracy,

REF

Measured at FB Pin

OUT

Load Regulation MODE=V

LOAD

OUT

Line Regulation 2.7V ≤ VIN ≤ 5.5V, I

VV

IN

FB Pin Leakage Current FB=0.8V 1 nA

REF

Transient Response I

OUT

P-Channel MOSFET On Resistance 33 mΩ

N-Channel MOSFET On Resistance 28 mΩ

P-MOS Peak Current Limit

Thermal Shutdown 155 °C

LIMIT

Thermal Shutdown Hysteresis 20 °C

HYST

Input OVP Shutdown

fSW Oscillator Frequency 2.1 2.4 3.0 MHz

f

MODE Pin Synchronization Range

MODE

Regulator Enable to Regulated V

tSS

(Rising PGOOD)

R

Output Discharge Resistance EN=0V 175 Ω

DIS

=2.7V to 5.5V, and T

IN

I

=0, MODE=0 (AUTO PFM/PWM) 50 µA

LOAD

I

=0, MODE=1 (Forced PWM) 30 mA

LOAD

V

Rising 2.67 2.80 V

IN

VIN Falling 2.1 2.3 V

PGOOD

PGOOD=VIN

=25°C, Forced PWM 0.792 0.800 0.808 V

T

A

TA=-40°C to 85°C, Forced PWM 0.787 0.800 0.813 V

AUTO PFM/PWM 0.784 0.800 0.824 V

Step 0.1A to 1.5A, tR=100ns -30 mV

LOAD

Open Loop 5.8 7.5 8.8 A

Closed Loop 8 A

Rising Threshold 6.1 V

Falling Threshold 5.5 5.8 V

External Square-Wave, 30% to 70% Duty
Cycle

OUT

1.2 ms

=-40°C to +85°C, unless otherwise noted. Typical values are at

A

=0.4V 1 mA

0.01 1.00 µA

(Forced PWM) –0.02 %/A

IN

=1.5A -0.16 %/V

OUT(DC)

525 600 700 kHz

FAN53540 — 2.4 MHz, 5A TinyBuck™ Synchronous Buck Regulator

© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com
FAN53540 • Rev. 1.0.2 5