1. FAN5903: 3/6MHz Buck Converter for 3G, 3.5G & 4G PAs
September 2011

2. Introduction
Mobile handsets and data cards are becoming an intricate part of everyday life and its use has become ubitiquos.
Battery technology has not kept up to pace with the demands to support higher densities to prolong usage time.
Since the requirement for longer talk and data transmit times has increased there needs to be a way to reduce power consumption in the 3G and 4G PAs.
DC-DC converters that support PAs are an emerging application space to reduce power consumption while enabling longer usage times and lower heat dissipation in portable devices.

3. RF Power Mgmt for Today, Tomorrow and Yesterday
FAN5903
GSM 2G
GPRS
2.5G
EDGE
2.75G
WCDMA 3G
HSPA+
3.5G
LTE 4G
FAN5904

4. FAN5903 3/6MHz Buck Converter for 3G/3.5G/4G PAs
Features
VIN range from 2.7V to 5.5V
VOUT range from 0.4V to 3.6V (or VIN)
Auto and manual Bypass modes
Small 540nH form factor inductor
1.34mm x 1.29mm, 9-Bump, 0.4mm pitch WLCSP
High efficiency PFM operation at low power
100% Duty Cycle for low dropout operation
3MHz/6MHz selectable switching frequency to facilitate system optimization
<10µs output voltage step response to allow early power loop settling
Input Under-Voltage Lockout / Thermal Shutdown
Applications
Dynamic supply for 3G, 3.5G, 4G PAs
Scalable supply for processor core power
Status
Samples & Eval Boards: Available Now
Production: Now

5. FAN5903 Application Diagram

6. FAN5903: Extending Connection Time for Mobile Devices
Voice Calls
Data Transmit
Usage curve from GSMA’s “Battery Life Measurement Technique, v4.7
Assumes System Current Consumption = 100mA

7. FAN5903: Usage Time Summary WCDMA Mode
Type
Parameters
FAN5903
(minutes)
No FAN5903
Improvement
Absolute (minutes)
Percentage
Voice
Tx Time using 3 PA Power Modes
641
585 56
9.5%
Tx Time with PA in High Power Mode
515
297
218
73.2%
Data
436
348 88
25.4%
394
253
141
55.6%

8. Reduced Heat Dissipation
POUT = VPA=2.97V
POUT = VBAT=3.7V
POUT = VBAT=4.2V
(Battery Charging)
3G PA w/ FAN5903
Thermal Profile
3G PA without FAN5903 Thermal Profile

9. Pricing & Availability
Fairchild Part Number
Package
Unit 1ku
Availability
FAN5903UCX
WLCSP-9
$0.760
Now

10. Summary
Best in-class power management solutions to support all cellular standards
Meets specifications outlined in cellular standards
FAN5903 is a compact, high efficiency buck converter that provides these benefits:
More than 55 minutes of increased talk/usage time in 3G mode
Lowers heat dissipation by 40%
Smallest solution footprint
Smaller passive components due to 6MHz switching frequency
Lowers total cost of ownership
Reduce battery size, weight and cost

11. Technical Materials FAN5903 Datasheet
FAN5903 Product Overview
Evaluation Boards
Request via Sales Center
Samples

12. Marketing & Apps Contacts
Marketing Contact
Wayne Seto
Applications Support
Paul Finkel

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