Power Saving Design in Mobile Applications
November 2010
www.fairchildsemi.com
Agenda
Fairchild Power Saving Solution for RF Power Amplifier
DC/DC (non-isolated) for Power Dissipation Consideration
Select Right LED Driver in Backlight Application
Company Confidential
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Power Consumption in a Smartphone
Major Power consumptions in a Smartphone
1.
RFPA for GSM/WCDMA
2.
Application Processor (AP)
3.
LED Backlighting
Company Confidential
3
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Power Consumption in a Smartphone
Reference: Araon Carroll and Gernot Heiser; NICTA, University of
New South Wales and Open Kernel Labs; “An Analysis of Power
Consumption in a Smartphone”
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Power Consumption in a Smartphone
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Fairchild Power Saving Solution for
RF Power Amplifier
November, 2010
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6
Variety Functions of Mobile Applications
Mobile is Camera, Mobile PC, Video Phone
More data is sent out from mobile phones
Picture sharing
Data send for mobile office
Video conference
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Challenge in Power Saving
Data rate has increased along with longer operation
3G and LTE need Linear RFPAs.
Limited battery capacity in small form factor
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Why Linearity Limit the Efficiency
Power amplifiers are designed for worst case: High RF Power
So they waste current (IQ) at low RF power
VDC
IDC
HIGH POWER RF
High IQ
Idc
VDS
Idc
Load
Line
Vds
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LOW POWER RF
High IQ = waste
Vds
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How to Improve the Efficiency
LOW POWER RF
Low IQ = NO waste
Idc
Idc
LOW POWER RF
High IQ = waste
Compression
Vds
Vds
Reduce the bias point in
lower power transmission
Company Confidential
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Ids
How to Move the Bias Point
RFPA Load
Line
Vds
Battery Voltage
Power Saving
4.0V
RFPA Supply Operated
by High Efficiency DCDC
instead of direct battery
supply
3.6V
VDCDC
RF Signal
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Longer Talk time with Fairchild RF
DCDC in WCDMA
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More Data/Web Surfing Time with
Fairchild RF DCDC in WCDMA
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Further Benefits in Mechanical Design
20°°C
25°°C
30°°C
40°°C
50°°C
65°°C
POUT = 28dBm @ VBAT=2.97V
Reduced Heat Dissipation
POUT = 28dBm @ VBAT=3.7V
3G PA with Reduced
Bias Point Thermal
Profile
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POUT = 28dBm @ VBAT=4.2V
(Battery Charging)
3G PA with Fixed Bias Point Thermal Profile
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FAN5902
800mA Buck Converter for 3G/3.5G PAs
Features
96% efficiency in synchronous operation
2.7V to 5.5V input voltage range
Up to 800mA output current
10µs step response
10µs bypass transition time
30mΩ bypass FET with slew rate control
for low battery
6MHz PWM operation for small form
factor inductor and capacitors
PFM Mode for light current loads when PA
output <8dBm
100% duty cycle for low drop-out
operation
Pkg: WLCSP-12 & 12-lead MLP
Applications
Status
Dynamic supply for 3G, 3.5G, 4G RF PAs
Scalable supply for processor core power
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Production:
Samples & EVBs:
15
Now
Now
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FAN5904
6W Buck Converter for GSM/EDGE & 3G/4G PAs
Features
GSM/EDGE Mode
•
•
•
•
Up to 95% efficiency
Enables 35dBm output power
5µs VOUT step response to allow early
GSM Tx power loop settling
3MHz PWM Mode
3G/4G Mode
•
•
•
•
Up to 95% efficiency
Supports 29dBm output power
10µs VOUT step response to allow early
power loop settling
6MHz PWM for high POUT and PFM for low
POUT PA operation
Bypass Mode
•
•
3A of load current
35mΩ integrated bypass FET
2.7V to 5.5V input voltage range
VOUT range: 0.4V to 3.4V or VBATT
Small form factor inductor (470nH) and
capacitors
Pkg: 1.75x1.75x0.6mm WLCSP-16
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FAN5904 Application Diagram
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IBATT vs. RF POUT for W-CDMA
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IBATT vs. RF POUT for W-CDMA
No FAN5904
With FAN5904
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IBATT vs. RF POUT for W-CDMA
No FAN5904
With FAN5904
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FAN590x Solution for Various RFPAs
FAN5904
GSM
2G
GPRS
2.5G
EDGE
2.75G
WCDMA
3G
HSPA+
3.5G
LTE
4G
FAN5902
FAN5903
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DC/DC (non-isolated) for Power Dissipation
Consideration
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Power Dissipation in DC/DC Analysis
Vin
Vo
FET
Lf
Chip
Diode
D
Cin
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Io
Cf
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Power Loss Calculation
Vin=3.7V; Vo=1.8V; Io=300mA or 20mA;
Vf=0.7V
Vo
Major Power Loss in DCDC
PLoss = PMOSFET = PSW + Pcond
PCond = Ploss_FET + Ploss_Diode
Vin
FET
Cin D
Lf
Diode
Io
Chip
Cf
Heavy load condition (Conduction Loss)
PLoss_FET(HS) = (D ∙ Io)2 ∙ Rdson = 0.021 ∙ 0.2 = 4.2mW
PLoss_diode = (1 – D) ∙ Io ∙ Vf
= 107.8mW
Ploss_Lf
= Io2 ∙ Rdc = 0.09 ⋅ 0.1
= 9.0mW
(Rdc depends on the size of inductor, while the size depends on switching frequency)
Light load condition (Switching Loss)
Psw ≈ PLoss_FET(HS) = (3.7 ∙ 0.02)/2 ∙ 0.2µs ⋅ 1MHz
= 7.4mW
Refer to Fairchild application notes, AN-6005 (http://www.fairchildsemi.com/an/AN/AN6005.pdf#page=1)
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Advanced Buck Converter Solution
Typical value
10nF to
0.1μF
PLoss_diode
= (1 – D) ∙ Io ∙ Vf
= 107.8mW
Fig_2: N-FET+N-FET Sync
buck structure
P loss_FET(LS)
= ((1 - D) ⋅ Io)2 ⋅ Rdson
= ((1-1.8/3.7) ⋅ 0.3)2 ⋅ 0.2
= 4.74mW
Fig_3: P-FET+N-FET Sync
buck structure
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Advanced Buck Converter Solution
Async-Buck w/ Diode
(Given Vf=0.7V)
Sync-Buck w/ FETLS
(Given 200mohm)
Improvement
Vin=3.7V; Vo=3.3V;
Io=300mA
22.7mW
0.21mW
(Conduction loss)
22.49mW
Vin=3.7V; Vo=1.8V;
Io=300mA
107.8mW
4.74mW
(Conduction loss)
103.06mW
Switching Freq =
1MHz (PWM)
Switching Freq =
20KHz (PFM)
7.4 mW
0.15mW
(Switching loss)
Condition
Vin=3.7V; Io=20mA
7.25mW
PWM
PFM
f(kHz)
Io(mA)
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IC design to reduce power loss
CPU or Application
Processor (AP) power
dissipation:
Ploss=C ∙ V2 ∙ Freq
Major solutions
Reduce operation
current consumption
Reduce leakage current
Advance solutions
Reduce Operation
Voltage, VCC
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How to save power by changing Vcc
Fig_4: Core power
loss variable with
different process
Fig_5: DVS technique
improve core power
loss
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Fairchild DVS Solution
FAN5365
VIN
VIN
Q1
CIN
EN
VSEL
SDA
VOUT
SW
MODULATOR
Q2
L OUT
COUT
SCL
PGND
AGND
VOUT
2
Dynamic Voltage
Scaling (DVS)
Tiny 0805 inductor
Automatically adjust Vcc based
on the processing status.
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Fairchild’s Integrated Switching
Regulators Portfolio
*Under development
Input Voltage (Vin)
24V
TinyBuck™
FAN8303
2A
FAN2103 - 3A
FAN2106 - 6A
FAN2108 - 8A
FAN2110 - 10A
FAN8301
370kHz 2A
12V
FAN53600: 3/6Mhz, 1A*
FAN5365: 6MHz 1A w/ I2C
FAN5355: 3MHz 1A w/ I2C
FAN2011: 1.3MHz 1.5A
FAN2001: 1.3MHz 1A
2.3V
Monolithic
VIN
FAN5352: 2.5A* FAN5353/4, 3MHz 3A
FAN5351:2A*
FAN53531, 3Mhz, 4A*
FAN2013B: 2A FAN53540, 2Mhz, 5A*
Portable Power Portfolio
0.5A
Non-Synchronous
SW
FAN21SV04 – 4A
FAN21SV06 - 6A
(single supply)
5.5V
FAN5361: 6MHz 600mA
FAN5362: 3Mhz 500mA
FAN5350: 3MHz 600mA
FAN5358: 2MHz 500mA
FAN4603: uModule*
PGND
1A
2A
3A
8A
10A
Load Current
Multi Chip
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LED Driver in Backlight Application
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LED Driver Configuration Analysis
Linear Mode
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Linear + Charge pump Mode
32
Boost converter Mode
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LED Driver Configuration Comparison
Mode
Linear
Charge Pump
Boost
Efficiency
85%@3.7V
<70%@3.7V below
80~90%@3.7V above
>80%@20mA
Vo range
Vin>Vo
Vin>Vo or
Vin<Vo
Vin<Vo
Component
count (Ext)
~2
~4
4~5 (2 cap, 1 inductor,
1 res, 1 diode)
LED
connection
Parallel
Parallel
Series or mixed
Solution space
smallest
middle
large
EMI
no
potential
potential
Control
interface
PWM
Single wire
PWM
Single wire
PWM
Single wire
LED screening
yes
yes
no
Item
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Brightness Control Modes
LED current Modulation pulse
Control signal
Ref. voltage
Fig_2: PWM Dimming
Fig_3: Single_wire Dimming
Mode
Control
Signal
Dimming
Direction
Interface
Noise
EMI
PWM
Current
Bi-direction
Analog
Yes
Yes
Single
Wire
Voltage
Count-down
or Up
Digital
No
No
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Linear mode Backlight LED Driver
FAN5626
Cell phone
FAN5624
Blood pressure meter
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Charge Pump Mode Backlight LED
Driver
CURRENT SINKS
FAN5701
Smart phone
GPS
CURRENT SINKS
FAN5702
Smart phone with ALS and DBC
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Boost mode Backlight LED Driver
Reduces
Start-up
Transients and
Audible
Interference
FAN5340
R
Q3
Sync boost
(True load
disconnection)
--Prevent from
conduction when
device disable
Dimming MOSFET.
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Ambient Light Control and
Dynamic Backlight Control
Ambient Light Control (ALC)
Ambient light sensor (ALS) provides a reference voltage
Adjusts the backlight level based upon outside light condition (Ref. voltage)
Information can be sent via digital bus to LED driver or done on-chip
Dynamic Backlight Control (DBC)
External PWM signal from image processor or LCD driver to LED driver
Utilizes image histogram information to optimize LED backlight given an
image profile
Tries to keep image contrast constant – frame by frame
Also called Content Adjustable Backlight Control (CABC)
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Ambient Light Control Setting
Up and working with DBC
Set initial current, ILED = 20.0mA
Ambient light trigger points:
ALSLOW ~ 1.00V (100lux)
ALSFULL ~ 1.50V (1,000lux)
ALSSUN ~ 1.75V (3,000lux)
LED current levels
ILED = 2.6mA; when EV < 100lux
ILED = 16.0mA; when EV < 1,000lux
ILED = 20.0mA; when EV > 3,000lux
If reflective display is used then set
register bit to 1 and ILED = 0mA
ALC
DBC
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Minimizing Backlight Power
Implementing DBC and ALC with FAN5702
Image Processor
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The Benefit with ALC & DBC
LED Current
Typical/Constant Dimming Mode
Ambient Light Control
Ambient Light Control
+
Dynamic Backlight Control
Time
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The Benefit with ALC & DBC
Fig_6: Display with
typical dimming
Image Quality
is improved
Fig_7: Display with
DBC&ALC
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Lighting Product Portfolio
Current Solutions
New Products
Serial Boost LED Driver
Charge Pump Boost LED Driver
Linear LED Driver
FAN5340
FAN5336
Low Audible
w/ 33V FET
FAN5340
FAN5341
FAN5343
FAN5333B
18V @ 40mA
Asynch. Boost
Asynch. Boost
VFB=315mV
FAN5336
FAN5607
FAN5702
FAN5333A
33V @ 50mA
IMAX=120mA
IMAX=180mA, I2C
VFB=110mV
FAN5333
FAN5646
FAN5624
FAN5701
FAN5331
30V @ 50mA
Prog. Fading
IMAX=120mA
IMAX=180mA, PWM
2x5 @ 25mA
FAN5331
FAN5645
FAN5622
FAN5611
FAN5626
FAN5640
FAN5608
20V @ 50mA
LED Blinker
IMAX=60mA
IMAX=160mA
IMAX=180mA
2-ch @ 25mA
2x6 @ 20mA
1
2
4
6
8
10+
PMOLED
<3” OLED
Displays
3
Number of LEDs to Backlight LCD Display / Keypads / Indicator
Indicator LEDs
Keypads
Secondary or ≤2” Displays
>2” Main LCD Displays
Mobile Handset, DSC, MP3, PMP, Video Camcorder, PC Cards, Security Camera, Wireless Headset, Consumer Electronics, Hand Tools
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Mobile Power Solutions
Battery Management
FAN540x – USB Charger
• 3MHz switcher
• Single inductor
•Buck for charge
•Boost for OTG
•I2C programmable
•>20V AMR voltage
•±5% Input/Charge current
regulation accuracy
RF Power Management
Batt Mngment
RFPA Power
Managament
Lighting
Management
W-CDMA
RFPA
FAN5902 – 6MHz 0.8A for WCDMA
FAN5904 – 6MHz 2A for
WCDMA/EDGE
• Controlled Output Voltage 0.4V to
3.4V
• 20us/5us transitions for WCDMA/EDGE
• 35mOhm Integrated Bypass FET
for Low-Batt 2.5A Load
GSM
RFPA
Core Power
Management
Lighting
Memory
I/O
WiMax
Application
Processor
FAN534x, FAN570x, FAN562x
• Parallel/Series LED driver
• PWM Dimming
Company Confidential
Core Power
FAN5365 – 6MHz 1A buck, I2C
• DVS for Apps Processors
• 0.75 < VOUT < 1.975 (12.5mV
resolution)
• Ultra fast transient response
architecture
• Low IQ
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The Right Technology for Your Success
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