Texas Instruments | TPS23861 VDD Power Solutions | Application notes | Texas Instruments TPS23861 VDD Power Solutions Application notes

Texas Instruments TPS23861 VDD Power Solutions Application notes
Application Report
SLUA788 – September 2016
TPS23861 VDD Power Solutions
Johnny Guo, JW Wu, Penny Xu
ABSTRACT
TPS23861 is an IEEE 802.3at compliant PSE controller integrated with analog circuits, digital circuits and
an embedded processor. The VPWR pin supplies power to the internal analog circuits while the VDD pin
supplies power for the digital circuits and internal processor. In most applications, an extra 3.3 V power is
required for VDD. This paper introduces some VDD power supply solutions and design considerations in
different solution environment.
1
2
3
4
5
Contents
Introduction ...................................................................................................................
VDD Power Design in Isolated PSE System .............................................................................
VDD Power Design in Non-isolated PSE System .......................................................................
Conclusion ....................................................................................................................
Reference .....................................................................................................................
2
2
6
7
7
List of Figures
1
VDD Power with High Voltage LDO in Isolated System ................................................................ 3
2
TPS23861 Power On Sequence ........................................................................................... 3
3
VDD Power with Switching Regulator in Isolated System .............................................................. 4
4
VDD Power with Discrete Solution in Isolated System ................................................................. 4
5
VDD Power with Auxiliary Winding Power in Isolated System
5
6
VDD Power in Non-isolated System - 1
6
7
........................................................
..................................................................................
VDD Power in Non-isolated System - 2 ..................................................................................
6
List of Tables
1
IVDD Specification in TPS23861 Datasheet ................................................................................ 2
All trademarks are the property of their respective owners.
SLUA788 – September 2016
Submit Documentation Feedback
TPS23861 VDD Power Solutions
Copyright © 2016, Texas Instruments Incorporated
1
Introduction
1
www.ti.com
Introduction
TPS23861 is an IEEE 802.3at compliant PSE controller integrated with analog circuits, digital circuits and
an embedded processor. The VDD (3.3 V) pin supplies power for internal digital circuits and processor. In
most applications, PSE power and system power are designed isolated regarding safety considerations.
This paper introduces different VDD power supply solutions and considerations for different applications.
In Electrical Characteristics Table of TPS23861 datasheet (SLUSBX9) , VDD current is 5 mA (typical) and
6 mA (maximum). When designing power supply for VDD with different solutions approaches, we need to
take the power consumption as a key consideration.
Table 1. IVDD Specification in TPS23861 Datasheet
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
INPUT SUPPLY VPWR
IVPWR
VPWR current consumption
VVPWR = 57 V
VUVLOPW_F
VPWR UVLO falling threshold
Internal oscillator stops operating
VPUV_F
VPWR Undervoltage falling
threshold
VPUV for port de-assertion
VUVLOPW_R
VPWR UVLO rising threshold
3.5
14.5
25
26.5
15.5
7
mA
17.5
V
28
V
18.5
V
INPUT SUPPLY VDD
2
IVDD
VDD current consumption
VUVDD_F
VDD UVLO falling threshold
VUVDD_R
VDD UVLO rising threshold
VUVDD_HYS
Hysteresis VDD UVLO
For port turn off
5
6
2
2.2
2.4
V
2.4
2.6
2.8
V
0.4
mA
V
VDD Power Design in Isolated PSE System
In most PSE systems like Ethernet Switch and Network Video Recorder (NVR), isolation is a common
system requirement. In these applications, VPWR (normally 48 V ~ 54 V) for PSE and 12 V for system are
supplied with adapters. Since VPWR is isolated from 12 V, power supply for VDD should be generated
from VPWR.
According to different system design and cost considerations, three VDD power solutions are proposed.
2
TPS23861 VDD Power Solutions
SLUA788 – September 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated
VDD Power Design in Isolated PSE System
www.ti.com
2.1
High Voltage LDO
12V
To System
Power
Supply
48~54V
VPWR
3.3V
VDD
LDO
TPS7A4001
TPS23861
Copyright © 2016, Texas Instruments Incorporated
Figure 1. VDD Power with High Voltage LDO in Isolated System
The simplest VDD power solution comes with a high voltage LDO. The maximum power loss on LDO is
calculated in Equation 1.
Ploss = (VVPWR(MAX) - VDD) × IVDD(MAX) = 0.304 W
(1)
Due to 0.304 W maximum power consumption on LDO, proper thermal consideration is required in real
board design, and one LDO is not suggested to supply power to ≥ 2 pieces of TPS23861.
Considering TPS23861 power on sequence requirement as shown in Figure 2, a high voltage LDO with
adjustable UVLO is recommended.
VVPWR > VUVLOPW_R (18.5V Max)
VPWR
VUVDD (2.8V Max)
VDD
VRESET = VIL (0.9V Max)
RESET
Figure 2. TPS23861 Power On Sequence
SLUA788 – September 2016
Submit Documentation Feedback
TPS23861 VDD Power Solutions
Copyright © 2016, Texas Instruments Incorporated
3
VDD Power Design in Isolated PSE System
2.2
www.ti.com
Switching Regulator
If efficiency and thermal are key considerations, a switching regulator is recommended. Compared with
LDO, switching regulator has better efficiency and higher current capability to feed multiple TPS23861
devices. Therefore, it is a good fit for Switch and NVR end equipment which has higher port count (>4
ports).
12V
To System
Power
Supply
48~54V
VPWR
3.3V
Switching
Regulator
LM5165
VDD
TPS23861
Copyright © 2016, Texas Instruments Incorporated
Figure 3. VDD Power with Switching Regulator in Isolated System
It is good engineering practice to set switching regulator’s EN/UVLO voltage above TPS23861 UVLO
(18.5 V) in application design.
2.3
Discrete Solution
For some cost-sensitive products and applications, a simple discrete solution is proposed as shown in
Figure 4. A Zener diode and high voltage NPN transistor is used to replace the high voltage LDO with a
low cost LDO.
12V
To System
Power
Supply
48~54V
VPWR
3.3V
VDD
LDO
TLV70433
12V
TPS23861
Copyright © 2016, Texas Instruments Incorporated
Figure 4. VDD Power with Discrete Solution in Isolated System
4
TPS23861 VDD Power Solutions
SLUA788 – September 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated
VDD Power Design in Isolated PSE System
www.ti.com
For the NPN transistor, a SOT-223 package is recommended which has better thermal performance. In
this design, the power consumption is shared by the collector resistor, NPN transistor and LDO. As a
result, it has better efficiency with lower cost compared to the high LDO solution.
2.4
Auxiliary Winding Power
In some isolated applications with single-output adapter, a Flyback topology is used to generate isolated
12 V from 48 V. VDD can be supplied from 12 V through above three solutions. Normally in Flyback
application, an auxiliary winding is used to generate 12 V for Flyback controller VCC power. One optional
selection is to generate 3.3 V with an LDO from auxiliary winding 12 V as shown in Figure 5. Since the
IVDD is 6 mA maximum, single wire auxiliary winding is able to power more than 2 TPS23861 devices. This
solution is also widely used due to its low cost and good thermal performance.
Power
Supply
48~54V
12V
To System
Flyback
Controller
LM5022
VPWR
VCC
3.3V
VDD
TPS23861
LDO
TLV70433
12V
Auxiliary Winding
Copyright © 2016, Texas Instruments Incorporated
Figure 5. VDD Power with Auxiliary Winding Power in Isolated System
SLUA788 – September 2016
Submit Documentation Feedback
TPS23861 VDD Power Solutions
Copyright © 2016, Texas Instruments Incorporated
5
VDD Power Design in Non-isolated PSE System
3
www.ti.com
VDD Power Design in Non-isolated PSE System
We have seen some customer’s system in which 48 V power rail and system power rail are non-isolated.
Under this condition, usually 12 V / 5 V / 3.3 V is generated from 48 V and VDD can be connected directly
with system 3.3 V.
Power
Supply
Switching
Regulator
LM5160A
48~54V
12V/5V to System
LDO
TLV70433
VPWR
3.3 V
3.3 V
VDD
TPS23861
Copyright © 2016, Texas Instruments Incorporated
Figure 6. VDD Power in Non-isolated System - 1
Power
Supply
48~54V
Switching
Regulator
LM5160A
3.3V to System
VPWR
3.3 V
VDD
TPS23861
Copyright © 2016, Texas Instruments Incorporated
Figure 7. VDD Power in Non-isolated System - 2
6
TPS23861 VDD Power Solutions
SLUA788 – September 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated
Conclusion
www.ti.com
4
Conclusion
The VDD for the TPS23861 digital circuits and internal processor needs external power supply. In nonisolated system, VDD pin can be directly connected to system 3.3 V. While in isolated system, 3.3 V
should be generated separately. Four methods have been discussed for different systems with
corresponding design considerations.
5
Reference
TPS23861 IEEE 802.3at Quad Port Power-over-Ethernet PSE Controller, SLUSBX9
TPS23861 Power-On Considerations, SLVA723
SLUA788 – September 2016
Submit Documentation Feedback
TPS23861 VDD Power Solutions
Copyright © 2016, Texas Instruments Incorporated
7
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
Automotive and Transportation
www.ti.com/automotive
Amplifiers
amplifier.ti.com
Communications and Telecom
www.ti.com/communications
Data Converters
dataconverter.ti.com
Computers and Peripherals
www.ti.com/computers
DLP® Products
www.dlp.com
Consumer Electronics
www.ti.com/consumer-apps
DSP
dsp.ti.com
Energy and Lighting
www.ti.com/energy
Clocks and Timers
www.ti.com/clocks
Industrial
www.ti.com/industrial
Interface
interface.ti.com
Medical
www.ti.com/medical
Logic
logic.ti.com
Security
www.ti.com/security
Power Mgmt
power.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Microcontrollers
microcontroller.ti.com
Video and Imaging
www.ti.com/video
RFID
www.ti-rfid.com
OMAP Applications Processors
www.ti.com/omap
TI E2E Community
e2e.ti.com
Wireless Connectivity
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2016, Texas Instruments Incorporated
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Related manuals

Download PDF

advertising