Fairchild FAN5353 service manual

FAN5353 — 3MHz, 3A Synchronous Buck Regulator

September 2010

FAN5353 3MHz, 3A Synchronous Buck Regulator

Features

 3MHz Fixed-Frequency Operation  Best-in-Class Load Transient  3A Output Current Capability  2.7V to 5.5V Input Voltage Range  Adjustable Output Voltage: 0.8V to V

IN

•0.9

 Power Good Output  Internal Soft-Start  Input Under-Voltage Lockout (UVLO)  Thermal Shutdown and Overload Protection  12-lead 3x3.5mm MLP

Applications

 Set-Top Box  Hard Disk Drive  Communications Cards  DSP Power

Description

The FAN5353 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 FAN5353 is capable of delivering 3A at over 85% efficiency. The regulator operates at a nominal fixed frequency of 3MHz, which reduces the value of the external components to 470nH for the output inductor and 10µF for the output capacitor. Additional output capacitance can be added without affecting stability if tighter regulation during transients is required. The regulator includes an open-drain power good (PGOOD) signal that pulls low when the output is not in regulation.

In shutdown mode, the supply current drops below 1µA, reducing power consumption.

FAN5353 is available in a 12-lead 3x3.5mm MLP package.

R1

C

OUT

L1

FB

VOUT

PGND

SW

R2

1

2

3

4

5

6

AGND

(GND)

P1

12

11

10

9

8

7

PGOOD

EN

VCC

PVIN

C

IN1

R3

C

VCC

C

IN

Figure 1. Typical Application

Ordering Information

Part Number Temp. Range Package Packing Method

FAN5353MPX -40 to 85°C MLP-12, 3x3.5mm Tape and Reel

FAN5353 — 3MHz, 3A Synchronous Buck Regulator

Table 1. Recommended External Components for 3A Maximum Load Current

Component Description Vendor Parameter Typ. Units

Vishay IHLP1616ABER47M01

L1 470nH nominal

Coiltronics SD12-R47-R

TDK VLC5020T-R47N

MURATA LQH55PNR47NT0

C

R3

OUT

IN

IN1

VCC

(1)

4.7μF, 6.3V, X5R, 0603

2 pieces

10μF, 6.3V, X5R, 0805 10μF, 6.3V, X5R, 0805

10nF, 25V, X7R, 0402

Resistor: 1Ω 0402

GRM21BR60J106M (Murata)

C2012X5R0J106M (TDK)

GRM155R71E103K (Murata)

C1005X7R1E103K (TDK)

GRM188R60J475K (Murata)

C1608X5R0J475K (TDK)

any R 1

Note:

1. R3 is optional and improves IC power supply noise rejection. See Layout recommendations for more information.

L 0.47

DCR 20

C 10.0

μH

mΩ

μF

C 10 nF

C 4.7

μF

Ω

Pin Configuration

FB

VOUT

PGND

SW

1

2

3

4

5

6

P1

(GND)

12

11

10

9

8

7

NC

PGOOD

EN

VCC

PVIN

Figure 2. 12-Pin, 3x3.5mm MLP (Top View)

Pin Definitions

Pin # Name Description

1 FB

2 VOUT

3, 4 PGND

5, 6 SW

P1 GND

7, 8 PVIN

9 VCC

10 EN

11 PGOOD

12 NC This pin has no function and should be tied to GND.

Note:

2. P1 is the bottom heat-sink pad. Ground plane should flow through pins 3, 4, 12, and P1 and can be extended through pin 11 if PGOOD’s function is not required to improve IC cooling.

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

VOUT. Sense pin for VOUT. Connect to COUT.

Power Ground. Low-side MOSFET is referenced to this pin. CIN and COUT should be returned with a minimal path to these pins.

Switching Node. Connect to inductor.

Ground. All signals are referenced to this pin.

Power Input Voltage. Connect to input power source. Connect to CIN with minimal path.

IC Bias Supply. Connect to input power source. Use a separate bypass capacitor CVCC from this pin

to the P1 GND terminal between pins 1 and 12.

Enable. The device is in shutdown mode when this pin is LOW. Do not leave this pin floating.

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

FAN5353 — 3MHz, 3A 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. Units

VIN

SW, PVIN, VCC Pins

Other Pins -0.3 VCC + 0.3

V

INOV_SLEW

R

Maximum Slew Rate of VIN Above 6.5V when PWM is Switching 15 V/ms

Pull-Up Resistance from PGOOD to VCC 1

PGOOD

ESD

Electrostatic Discharge Protection Level

TJ Junction Temperature –40 +150 °C

T

Storage Temperature –65 +150 °C

STG

TL Lead Soldering Temperature, 10 Seconds +260 °C

Note:

3. Lesser of 7V or V

+0.3V.

CC

IC Not Switching -0.3 7.0

IC Switching -0.3 6.5

V

(3)

V

KΩ

Human Body Model per JESD22-A114 2 KV

Charged Device Model per JESD22-C101 2 KV

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. Units

V

Supply Voltage Range 2.7 5.5 V

CC, VIN

V

Output Voltage Range 0.8 90% Duty Cycle V

OUT

I

Output Current 0 3 A

OUT

L Inductor 0.47 µH

CIN Input Capacitor 10 µF

C

Output Capacitor 20 µF

OUT

TA Operating Ambient Temperature -40 +85 °C

TJ Operating Junction Temperature -40 +125 °C

Thermal Properties

Symbol Parameter Min. Typ. Max. Units

θJA

Junction-to-Ambient Thermal Resistance

Note:

4. 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 JESD51- JEDEC standard. Special attention must be paid not to exceed junction temperature T

at a given ambient temperate TA.

J(max)

(4)

46 °C/W

FAN5353 — 3MHz, 3A Synchronous Buck Regulator

Electrical Characteristics

Minimum and maximum values are at V

= 25°C, VIN =5V.

T

A

Symbol Parameter Conditions Min. Typ. Max. Units

Power Supplies

IQ Quiescent Current I

I

Shutdown Supply Current EN = GND 0.1 3.0

SD

V

Under-Voltage Lockout Threshold

UVLO

V

Logic Pins

VOUT Regulation

Power Switch and Protection

R

Frequency Control

Soft-Start

Under-Voltage Lockout Hysteresis 530 mV

UVHYST

VIH HIGH-Level Input Voltage 1.05 V

VIL LOW-Level Input Voltage 0.4 V

V

Logic Input Hysteresis Voltage 100 mV

LHYST

IIN Input Bias Current Input tied to GND or VIN 0.01 1.00

I

PGOOD Pull-Down Current V

OUTL

I

PGOOD HIGH Leakage Current V

OUTH

Output Reference DC Accuracy Measured at FB Pin

V

OUT

IN

DC Accuracy

OUT

Load Regulation I

Line Regulation

Δ

V

IVΔ

LOAD

REF

REG

VVΔ

Transient Response

P-channel MOSFET On Resistance 60 mΩ

DS(ON)P

N-channel MOSFET On Resistance 40 mΩ

DS(ON)N

I

P-MOS Peak Current Limit 3.75 4.55 5.50 A

LIMPK

T

Thermal Shutdown 150 °C

LIMIT

T

Thermal Shutdown Hysteresis 20 °C

HYST

V

Input OVP Shutdown

SDWN

fSW Oscillator Frequency 2.7 3.0 3.3 MHz

tSS Regulator Enable to Regulated V

V

Soft-Start V

SLEW

Slew Rate 10 V/ms

OUT

= 2.7V to 5.5V, T

IN

OUT

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

A

LOAD

= 0, V

=1.2V 14 mA

OUT

μA

V

Rising 2.83 2.95 V

IN

VIN Falling 2.10 2.30 2.40 V

μA

= 0.4V 1 mA

PGOOD

= VIN 0.01 1

PGOOD

= 25°C 0.792 0.800 0.808 V

T

A

μA

0.788 0.800 0.812 V

At VOUT pin W.R.T. Calculated Value, I

OUT(DC)

2.7V ≤ V

= 500mA

LOAD

= 0 to 3A –0.03 %/A

≤ 5.5V, I

IN

OUT(DC)

=

1.5A

I

step 0.1A to 1.5A, tr = tf =

LOAD

100ns, V

OUT

=1.2V

1.6% +1.6 %

0.01 %/V

+20 mV

Rising Threshold 6.2 V

Falling Threshold 5.50 5.85 V

R

LOAD

> 5Ω, to V > 5Ω, to V

OUT

= 1.2V

= 1.8V

210 250

340 420

μs μs