Fairchild FAN5903 service manual

December 2011

FAN5903 Buck Converter with Bypass Mode for 3G/3.5G/4G PAs

FAN5903 — Buck Converter with Bypass Mode for 3G/3.5G/4G PAs

Features



2.7V to 5.5V Input Voltage Range

 V

Range from 0.4V to 3.50V (or VIN)

OUT

 Small Form Factor Inductor

o 2012 470nH or 540nH for Minimal PCB Area o 2020 1.0µH for Higher Efficiency

 Bypass Dropout at 500mA, 60mV Typical  100% Duty Cycle for Low Dropout Operation  Input Under-Voltage Lockout / Thermal Shutdown  1.34mm x 1.29mm, 9-Bump, 0.4mm-Pitch WLCSP  3MHz / 6MHz Selectable Switching Frequency to

Facilitate System Optimization

 High-Efficiency PFM Operation at Low Power  Sleep Mode for Very Low I

Operation

 Up to 96% Efficient Synchronous Operation at

High-Power Conditions

 10µs Output Voltage Step Response for Early

Power Loop Settling

Applications

 Dynamic Supply Bias for 3G/3.5G and 4G PAs  Power Supply for WCDMA/LTE PAs

Resources

For more information or a full copy of this datasheet, please contact a Fairchild representative.

Description

FAN5903 is a high-efficiency, low-noise, synchronous, step-down, DC-DC converter designed for powering 3G/3.5G/4G RF Power Amplifiers (PAs) in handsets and other mobile applications.

The output voltage may be dynamically varied from

0.40V to 3.50V, proportional to an analog input V ranging from 0.16V to 1.40V provided by an external DAC. This allows the PA to be supplied with the voltage that enables maximum power-added efficiency.

An integrated bypass FET automatically switches on when battery voltage drops close to the desired output voltage (V to Synchronous Mode when the voltage dropout exceeds 375mV. The integrated bypass FET is also enabled when V

The FAN5903 offers fast transition times, enabling changes to the output voltage in less than 10µs for power transitions. Moreover, a Current-Mode control loop with fast transient response ensures excellent line and load regulation.

Light-load efficiency is optimized by operating in PFM Mode for load currents typically less than 100mA.

The switching frequency may be set to 3MHz or 6MHz, enabling further optimization of system performance. The FAN5903 typically uses a single, small-form-factor inductor of 540nH. Efficiency may be further optimized using a 1.0µH inductor when running at 3MHz.

When output regulation is not required, the FAN5903 may be placed in Sleep Mode by setting V to 100mV. This ensures a very low I enabling a fast return to output regulation. The FAN5903 enables significant current reduction and increased talk time and is available in a 1.34mm x

1.29mm, 9-bump, 0.40mm-pitch, WLCSP package.

OUT=VBAT

-200mV). The DC-DC switches back

is nominally greater than to 1.5V.

CON

nominally

CON

(<70µA) while

CON

Ordering Information

Part Number

FAN5903UCX -40 to +85°C

Operating

Temperature Range

1.34mm x 1.29mm, 9-bump, 0.4mm Pitch, Wafer-Level Chip-Scale Package (WLCSP)

Package Packing Method

Tape and Reel

Physical Dimensions

FAN5903 — Buck Converter with Bypass Mode for 3G/3.5G/4G PAs

PIN A1

INDEX AREA

0.05

0.03

TOP VIEW

SEATING PLANE

0.539

0.461

0.03

0.06

SIDE VIEWS

0.40

Ø0.20 Cu Pad

Ø0.30 Solder Mask

LAND PATTERN RECOMMENDATION

(NSMD PAD TYPE)

0.292±0.018

0.208±0.021

NOTES:

A. NO JEDEC REGISTRATION APPLIES.

0.40

123

BOTTOM VIEW

Ø0.260±0.020 9X

C B

(Y)±0.018

(X)±0.018

B. DIMENSIONS ARE IN MILLIMETERS.

C. DIMENSIONS AND TOLERANCE PER ASMEY14.5M, 1994.

D. DATUM C IS DEFINED BY THE SPHERICAL

CROWNS OF THE BALLS.

E. PACKAGE NOMINAL HEIGHT IS 500 MICRONS

±39 MICRONS (461-539 MICRONS).

F. FOR DIMENSIONS D, E, X, AND Y SEE

PRODUCT DATASHEET.

G. DRAWING FILNAME: MKT-UC009AErev1

Product D E X Y Unit

FAN5903UCX 1.292 ± 0.030 1.342 ± 0.030 0.271 0.246 mm

Figure 42. 1.34 x 1.29mm, 9-Bump, 0.4mm-Pitch WLCSP

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 revi sion. 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/.

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