Simple Battery Circuit Extends PoE Peak Current (Design Note 361)
Design note describing a circuit using the LTC4267 and LTC4055 to supplement PoE power with a battery for high peak current loads like disk drives or RF transmitters.
Overview
This design note details a compact power management solution for Power over Ethernet (PoE) applications that require peak currents exceeding standard PoE limits. It utilizes the LTC4267, which combines a PoE Powered Device (PD) interface with an isolated flyback converter to generate a 5V supply. The LTC4055 PowerPath controller manages the battery charging of a single Li-Ion cell and provides seamless power switching. When system demand exceeds the PoE power capability, the battery automatically supplements the supply. This configuration is ideal for handling transient loads such as disk drive spin-up or sustained RF transmissions without triggering PoE current limits.
Use Cases
- Disk drive spin-up in PoE devices
- RF transmitter peak power management
- High transient load PoE applications
- Battery-backed Ethernet powered devices
Topics
Referenced Parts
LTC3407-2
Linear Technology
and/or the LTC3407-2 dual buck regulators.
LTC3443
Linear Technology
Recommended DC/DC converters to generate logic supplies in this application include the LTC3443 buck-boost
LTC4055
Linear Technology
In Figure 1, the LTC4055 provides triple PowerPath control and Li-Ion battery charging.
LTC4267
Linear Technology
The LTC ®4267 simplifies the design of PDs by providing wholesale implementation of the protocol and power management functions.
LTC4411
Linear Technology
the diode D9 can be replaced with the LTC4411 ideal diode for more efficient operation.
SMB540
Diodes Incorporated
D1 SMB540
ZRL431
Diodes Incorporated
D8 ZRL431
UPS340
Microsemi
D9 UPS340
PA1134
Pulse Electronics
T1 PA1134
PS2911
Renesas
PS2911
Si3440DV
Vishay
Q1 Si3440DV
HD01
Diodes Incorporated
AC2 HDO1
| SMAJ58A | Littelfuse | D2 SMAJ58A |
| BAS516 | NXP | D7 BAS516 |
| 1N5237B | Onsemi | D5 1N5237B |
| 2N7002 | Onsemi | Q3 2N7002 |
| MMBTA42 | Onsemi | Q2 MMBTA42 |
| LTC3407-2 | Linear Technology | and/or the LTC3407-2 dual buck regulators. |
| LTC3443 | Linear Technology | Recommended DC/DC converters to generate logic supplies in this application include the LTC3443 buck-boost |
| LTC4055 | Linear Technology | In Figure 1, the LTC4055 provides triple PowerPath control and Li-Ion battery charging. |
| LTC4267 | Linear Technology | The LTC ®4267 simplifies the design of PDs by providing wholesale implementation of the protocol and power management functions. |
| LTC4411 | Linear Technology | the diode D9 can be replaced with the LTC4411 ideal diode for more efficient operation. |
| SMB540 | Diodes Incorporated | D1 SMB540 |
| ZRL431 | Diodes Incorporated | D8 ZRL431 |
| UPS340 | Microsemi | D9 UPS340 |
| PA1134 | Pulse Electronics | T1 PA1134 |
| PS2911 | Renesas | PS2911 |
| Si3440DV | Vishay | Q1 Si3440DV |
| HD01 | Diodes Incorporated | AC2 HDO1 |