TPS23757 Datasheet, PDF (1/37 Pages) Texas Instruments – High Efficiency PoE Interface and DC/DC Controller

TPS23757
www.ti.com ....................................................................................................................................................................................................... SLVS948 – JULY 2009
High Efficiency PoE Interface and DC/DC Controller
FEATURES
1
• Powers up to 13 W (Input) PDs
• Legacy and IEEE 802.3at type 1 PDs
• Optimized for Isolated DC/DC Converters
• Supports High-Efficiency Topologies
• Complete PoE Interface
• Adapter ORing Support
• Programmable Frequency with Synch.
• Robust 100 V, 0.5 Ω Hotswap MOSFET
• Pin Compatible with TPS23754/6
• –40°C to 125°C Junction Temperature Range
• Industry Standard TSSOP-20
APPLICATIONS
• IEEE 802.3at (draft) type 1 Compliant Devices
• Video and VoIP Telephones
• Access Points
• Security Cameras
DESCRIPTION
The TPS23757 is a combined Power over Ethernet
(PoE) powered device (PD) interface and
current-mode dc/dc controller optimized specifically
for isolated converters. The PoE interface supports
the IEEE 802.3at (draft) standard for a type 1 PD,
which is equivalent to the 13W standard of IEEE
802.3-2008.
The TPS23757 supports a number of input voltage
ORing options including highest voltage, external
adapter preference, and PoE preference.
The TPS23757 has an output flag indicating if an
external wall adapter is active when used in
conjunction with ORing controls. The detection
signature pin can also be used to force power from
the PoE source off. Classification can be
programmed to any of the defined types with a single
resistor.
The dc/dc controller features two complementary gate
drivers with programmable dead time. This simplifies
design of highly-efficient flyback topologies or
active-clamp forward or flyback converters. The
second gate driver may be disabled if desired for
single MOSFET topologies. The controller also
features internal softstart, bootstrap startup source,
current-mode compensation, and a 78% maximum
duty cycle. A programmable and synchronizable
oscillator allows design optimization for efficiency and
eases use of the controller to upgrade existing power
supply designs. Accurate programmable blanking,
with a default period, simplifies the usual current-
sense filter design trade-offs.
The TPS23757 has a 9 V converter startup,
permitting operation with 12 V wall adapters.
DA
RAPD1
Optional
Interface
DEN
PPD
CLS
VSS
APD
CTL
FRS
APb
VC
VB
GATE
CS
GAT 2
RAPb
M1 ^VB
T1
CIN
DVC1
M2
T2
CIO
L OUT
ROB
CIZ
TLV 431
Figure 1. High Efficiency Converter Using TPS23757
VOUT
RAPb_OUT
VAPb_OUT
Adapter
Present and
Converter
Running
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009, Texas Instruments Incorporated