Application Report
SLVA339A – June 2009 – Revised May 2010
High-Vin, High-Efficiency Power Solution Using DC/DC
Converter With DVFS
Ambreesh Tripathi .......................................................................... PMP - DC/DC Low-Power Converters
ABSTRACT
This reference design is intended for users designing with the TMS320C6742, TMS320C6746,
TMS320C6748, or OMAP-L138 processor. Using sequenced power supplies, this reference design
describes a system having a 12-V input voltage and a high-efficiency dc/dc converter with integrated FETs
and dynamic voltage and frequency scaling (DVFS) for a small, simple design.
Sequenced power supply architectures are becoming commonplace in high-performance microprocessor
and digital signal processor (DSP) systems. To save power and increase processing speeds, processor
cores have smaller geometry cells and require lower supply voltages than the system bus voltages. Power
management in these systems requires special attention. This application report addresses these topics
and suggests solutions for output voltage sequencing.
1
2
3
4
Contents
Introduction ..................................................................................................................
Power Requirements .......................................................................................................
Features ......................................................................................................................
Bill of Materials ..............................................................................................................
2
2
3
6
List of Figures
1
PMP4976 Reference Design Schematic ................................................................................. 4
2
Optional Circuit for DVDD_A, DVDD_B, and DVDD_C ................................................................ 5
3
Sequencing in Start-up Waveform ........................................................................................ 7
4
Efficiency vs Output Current ............................................................................................... 7
5
Efficiency vs Output Current ............................................................................................... 7
6
Efficiency vs Output Current ............................................................................................... 7
7
Efficiency vs Output Current ............................................................................................... 7
List of Tables
1
General Requirements ..................................................................................................... 2
2
PMP4976 Bill of Materials
SLVA339A – June 2009 – Revised May 2010
.................................................................................................
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
6
1
Introduction
1
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Introduction
In dual voltage architectures, coordinated management of power supplies is necessary to avoid potential
problems and ensure reliable performance. Power supply designers must consider the timing and voltage
differences between core and input/output (I/O) voltage supplies during power-up and power-down
operations.
Sequencing refers to the order, timing, and differential in which the two voltage rails are powered up and
down. A system designed without proper sequencing may be at risk for two types of failures. The first of
these represents a threat to the long-term reliability of the dual voltage device, whereas the second is
more immediate, with the possibility of damaging interface circuits in the processor or system devices
such as memory, logic, or data converter integrated circuits (IC).
Another potential problem with improper supply sequencing is bus contention. Bus contention is a
condition in which the processor and another device both attempt to control a bidirectional bus during
power up. Bus contention may also affect I/O reliability. Power supply designers must check the
requirements regarding bus contention for individual devices.
The power-on sequencing for the OMAP-L138, TMS320C6742, TMS320C6746, and TMS320C6748 are
shown in Table 1. None of the supplies for these devices require a specific voltage ramp rate as long as
the 3.3-V rail does not exceeds the 1.8-V rail by more than 2 V.
In order to reduce the power consumption of the processor core, dynamic voltage and frequency scaling
(DVFS) is used in the reference design. DVFS is a power management technique used while active
processing is going on in the system-on-chip (SoC), which matches the operating frequency of the
hardware to the performance requirement of the active application scenario. Whenever clock frequencies
are lowered, operating voltages are also lowered to achieve power savings. In the reference design, the
TPS62353 is used, which can scale its output voltage.
2
Power Requirements
The power requirements are as specified in the following table.
Table 1. General Requirements
VOLTAGE
(V)
PIN NAME
I/O
RTC_CVDD
(4)
(1) (2)
Imax
(mA)
TOLERANCE
SEQUENCING
ORDER
1.2
1
–25%, +10%
1 (3)
1.0 / 1.1 / 1.2
600
–9.75%, +10%
2
Core
CVDD
I/O
RVDD, PLL0_VDDA,
PLL1_VDDA, SATA_VDD,
USB_CVDD, USB0_VDDA12
1.2
200
–5%, +10%
3
I/O
USB0_VDDA18, USB1_VDDA18,
DDR_DVDD18, SATA_VDDR,
DVDD18
1.8
180
±5%
4
I/O
USB0_VDDA33, USB1_VDDA33
3.3
24
±5%
5
I/O
DVDD3318_A, DVDD3318_B,
DVDD3318_C
1.8 / 3.3
50 / 90 (5)
±5%
4/5
(1)
(2)
(3)
(4)
(5)
TIMING
DELAY
If 1.8-V LVCMOS is used, power rails up with the 1.8-V rails. If 3.3-V LVCMOS is used, power it up with the ANALOG33 rails
(VDDA33_USB0/1).
No specific voltage ramp rate is required for any of the supplies LVCMOS33 (USB0_VDDA33, USB1_VDDA33) as long as
STATIC18 (USB0_VDDA18, USB1_VDDA18, DDR_DVDD18, SATA_VDDR, DVDD18) never exceeds more than 2 V.
If RTC is not used/maintained on a separate supply, it can be included in the STATIC12 (fixed 1.2 V) group.
If using CVDD at fixed 1.2 V, all 1.2-V rails may be combined.
If DVDD3318_A, B, and C are powered independently, maximum power for each rail is 1/3 above maximum power.
NanoFree is a trademark of Texas Instruments.
2
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
SLVA339A – June 2009 – Revised May 2010
Features
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3
Features
The design uses the following high-efficiency dc/dc converters with integrated FETs.
HIGH EFFICIENCY (With DVFS)
INPUT VOLTAGE
~12 V/3.3 V
OUTPUT VOLTAGES
Core 1.2 V at 600 mA
TPS62353
Fixed 1.2 V + VRTC at 251 mA
TPS62232
1.8 V at 230 mA
TPS62231
3.3 V at 115 mA
TPS62111
In the preceding table, VRTC is included in the STATIC12 (fixed 1.2-V) group.
TPS62353
• 88% efficiency at 3-MHz operation
• Output peak current up to 800 mA
• 3-MHz fixed frequency operation
• Best in class load and line transient
• ±2% PWM dc voltage accuracy
• Efficiency optimized Power-Save mode
• Transient optimized Power-Save mode
• Fixed 1.2-V output eliminates need for external voltage-setting resistors
• Available in a 10-pin QFN (3 × 3 mm) 12-pin NanoFree™ (CSP) packaging
TPS62231 and TPS62232
• 3-MHz switch frequency
• Up to 94% efficiency
• Output peak current up to 500 mA
• Small external output filter components (1 mH/4.7 mF)
• Small 1 × 1,5 × 0,6 mm 3 SON package
• Fixed 1.8-V and 1.2-V output, respectively, eliminates need for external voltage-setting resistors
TPS62111
• High-efficiency synchronous step-down converter with up to 95% efficiency
• Up to 1.5-A output current
• High efficiency over a wide load-current range due to PFM/PWM operation mode
• Fixed 3.3-V output eliminates need for external voltage-setting resistors
More information on the devices can be found in the data sheets.
• TPS62111, SLVS585
• TPS62231 and TPS62232, SLVS941
• TPS62353, SLVS540
SLVA339A – June 2009 – Revised May 2010
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
3
Features
www.ti.com
Figure 1. PMP4976 Reference Design Schematic
4
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
SLVA339A – June 2009 – Revised May 2010
Features
www.ti.com
Proper sequencing is ensured in the design with the use of a NPN transistor and a P-channel MOSFET.
As required, Core 1.2 V at 600 mA comes first, and is followed by Static 1.2 V + VRTC at 251 mA. Then
comes Static 1.8 V at 230 mA, which in turn pulls down the gate of a P-channel MOSFET with the use of
a NPN transistor. Last, Static 3.3 V at 115 mA comes up.
(1)
Use three such LDOs to power up DVDDA, DVDDB, and DVDDC. (It can be either 1.8 V or 3.3 V.)
(2)
Rx = 0.499 MΩ, Ry = 1 MΩ for Vout = 1.8 V
(3)
Rx = 1.8 MΩ, Ry = 1 MΩ for Vout = 3.3 V
(4)
For proper sequencing of output, the enable of the LDOs are fed either from a 1.2-V output from TPS62232 if
DVDDX is 1.8 V or from a 1.8-V output from TPS62231 if DVDDX is 3.3 V.
Figure 2. Optional Circuit for DVDD_A, DVDD_B, and DVDD_C
SLVA339A – June 2009 – Revised May 2010
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
5
Bill of Materials
4
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Bill of Materials
Table 2. PMP4976 Bill of Materials
Count
2
RefDes
Value
Description
Size
Part Number
MFR
AREA
C1
10 mF
Capacitor, Ceramic, 25V, X5R, 20%
1206
C3216X5R1E106
TDK
15390
C2
10 mF
Capacitor, Ceramic, 25V, X5R, 20%
1206
C3216X5R1E106
TDK
15390
C3
22 mF
Capacitor, Ceramic, 10V, X5R, 20%
1206
C3216X5R1A226
TDK
15390
C4
22 mF
Capacitor, Ceramic, 10V, X5R, 20%
1206
C3216X5R1A226
TDK
15390
1
C5
1 mF
Capacitor, Ceramic, 25V, X7R, 10%
603
C1608X7R1E105K
TDK
5650
2
C6
10 mF
Capacitor, Ceramic, 6.3V, X5R, 10%
603
C1608X5R0J106KT
TDK
5650
C7
10 mF
Capacitor, Ceramic, 6.3V, X5R, 10%
603
C1608X5R0J106KT
TDK
5650
1
C8
47 mF
Capacitor, Ceramic, 10V, X5R, 20%
1812
C4532X5R1A476M
TDK
43,360
2
C9
22 mF
Capacitor, Ceramic, 10V, X5R, 20%
1210
Std
Std
83,600
2
C10
2.2 mF
Capacitor, Ceramic, 6.3V, X5R, 20%
402
JDK105BJ225MV
Taiyo Yuden
2800
2
C11
4.7 mF
Capacitor, Ceramic, 6.3V, X5R, 20%
402
JDK105BJ475MV
Taiyo Yuden
2800
C12
22 mF
Capacitor, Ceramic, 10V, X5R, 20%
1210
Std
Std
83,600
C13
2.2 mF
Capacitor, Ceramic, 6.3V, X5R, 20%
402
JDK105BJ225MV
Taiyo Yuden
2800
C14
4.7 mF
Capacitor, Ceramic, 6.3V, X5R, 20%
402
JDK105BJ475MV
Taiyo Yuden
2800
1
J1
PTC36SAAN
Header, Male 6-pin, 100mil spacing, (36-pin strip)
0.100 inch × 6
PTC36SAAN
Sullins
70000
1
J2
2510-6002UB
Connector, Male Straight 2×10 pin, 100mil
spacing, 4 Wall
0.338 × 0.788
2510-6002UB
3M
301.02
4
1
J3
PEC36SAAN
Header, Male 5-pin, 100mil spacing, (36-pin strip)
0.100 inch × 5
PEC36SAAN
Sullins
60000
1
JP1
PTC36SAAN
Header, 3-pin, 100mil spacing, (36-pin strip)
0.100 × 3
PTC36SAAN
Sullins
34100
1
L1
6.8 mH
Inductor, SMT, 3.0A, 97 mΩ
0.276 × 0.276 inch
HA3808-AL
Coiltronics
90000
1
L2
1 mH
Inductor, SMT, 1.6A, ±30%
0.118 × 0.118
LPS3010-102NLC
Coilcraft
26,560
2
L3
2.2 mH
Inductor, SMT, 0.7A, 230-mΩ
805
MIPSZ20120D2R2
FDK
10160
L4
2.2 mH
Inductor, SMT, 0.7A, 230-mΩ
805
MIPSZ20120D2R2
FDK
10160
1
Q1
Si2335DS
MOSFET, P-ch, -12 V, 4 A, 51 mΩ
SOT23
Si2335DS
Vishay
14105
1
Q2
2N3904
Transistor, NPN, 40V, 200mA, 625mW
TO-92
2N3904
Fairchild
37800
1
R1
1M
Resistor, Chip, 1/16-W, 1%
603
Std
Std
9100
2
R2
10K
Resistor, Chip, 1/16W, x%
603
Std
Std
5,650
R3
10K
Resistor, Chip, 1/16W, x%
603
Std
Std
5,650
1
R4
1M
Resistor, Chip, 1/16W, x%
603
Std
Std
5,650
1
R5
1M
Resistor, Chip, 1/16W, 1%
603
Std
Std
5650
2
R6
10k
Resistor, Chip, 1/16W, 1%
603
Std
Std
5650
R7
10k
Resistor, Chip, 1/16W, 1%
603
Std
Std
5650
R8
1K
Resistor, Chip, 1/16W, x%
603
Std
Std
5,650
R9
1K
Resistor, Chip, 1/16W, x%
603
Std
Std
5,650
1
U1
TPS62111RSA
IC, Synchronous Step-Down Converter, 17V,
1.2A
QFN-16
TPS62111RSA
TI
54289
1
U2
TPS62353YZG
IC, 3MHz Synchronous Step Down Converter
with I2C, 800mA
CSP-12
TPS62353YZG
TI
12,000
1
U3
TPS62232DRY
IC, 3MHz Ultra Small Step Down Converter, x.x V QFN
TPS62232DRY
TI
6020
1
U4
TPS62231DRY
IC, 3MHz Ultra Small Step Down Converter, x.x V QFN
TPS62232DRY
TI
6020
2
2
Notes: 1. These assemblies are ESD sensitive, ESD precautions shall be observed.
2. These assemblies must be clean and free from flux and all contaminants. Failure to use clean flux is unacceptable.
3. These assemblies must comply with workmanship standards IPC-A-610 Class 2.
4. Reference designators marked with an asterisk ('**') cannot be substituted. All other components can be substituted with equivalent MFG's
components.
6
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
SLVA339A – June 2009 – Revised May 2010
Bill of Materials
www.ti.com
4.1
Test Result
The start-up waveform Figure 3 specifies the sequencing order that is required.
Figure 3. Sequencing in Start-up Waveform
100
100
VIN = 2.3 V
4.2 V
90
90
80
Efficiency -%
70
80
VIN = 2.7 V
Efficiency - %
VIN = 3.3 V
VIN = 3.6 V
60
VIN = 4.2 V
50
VIN = 5 V
40
30
20
10
L = 2.2 mH (MIPSA25202R2),
COUT = 4.7 mF
8.4 V
50
12 V
40
VO = 3.3 V
o
TA = 25 C
PFM Mode
20
1
10
100
IO - Output Current - mA
Figure 4. Efficiency vs Output Current
SLVA339A – June 2009 – Revised May 2010
60
30
MODE = GND,
VOUT = 1.8 V,
0
0.1
5V
70
10
1000
0
0.0001
0.001
0.01
0.1
IO - Output Current- A
1
10
Figure 5. Efficiency vs Output Current
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
7
Bill of Materials
www.ti.com
100
100
VIN = 2.3 V
90
80
80
VIN = 2.7 V
70
Efficiency − %
Efficiency -%
70
VIN = 3.6 V
60
VIN = 4.2 V
50
VIN = 5 V
40
30
60
50
FPFM/PWM
3-MHz PWM
40
30
20
MODE = GND,
VOUT = 1.2 V,
10
L = 2.2 mH MIPSZ2012 2R2 (2012 size),
COUT = 4.7 mF
0
0.1
1
10
100
IO - Output Current - mA
Figure 6. Efficiency vs Output Current
8
LPFM/PWM
90
1000
20
VI = 3.6 V
VO = 1.35 V
10
L = 1 mH
CO = 10 mF
0
0.1
1
10
100
IO − Output Current − mA
1000
Figure 7. Efficiency vs Output Current
High-Vin, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Copyright © 2009–2010, Texas Instruments Incorporated
SLVA339A – June 2009 – Revised May 2010
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