TPS23754_10 Datasheet, PDF (1/41 Pages) Texas Instruments – High Power/High Efficiency PoE Interface and DC/DC Controller

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TPS23754
TPS23754-1
TPS23756
SLVS885D – OCTOBER 2008 – REVISED DECEMBER 2009
High Power/High Efficiency PoE Interface and DC/DC Controller
FEATURES
1
•2 Powers up to 30 W (input) PDs
• DC/DC Control Optimized for Isolated
Converters
• Supports High-efficiency Topologies
• Complete PoE Interface
• Enhanced Classification per IEEE 802.3at with
Status Flag
• Adapter ORing Support
• Programmable Frequency with
Synchronization
• Robust 100 V, 0.5 Ω Hotswap MOSFET
• –40°C to 125°C Junction Temperature Range
• Industry Standard PowerPAD™ TSSOP-20
APPLICATIONS
• IEEE 802.3at Compliant Devices
• Video and VoIP Telephones
• RFID Readers
• Multiband Access Points
• Security Cameras
DESCRIPTION
The TPS23754/6 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 standard.
The TPS23754/6 supports a number of input voltage
ORing options including highest voltage, external
adapter preference, and PoE preference. These
features allow the designer to determine which power
source will carry the load under all conditions.
The PoE interface features the new extended
hardware classification necessary for compatibility
with high-power midspan power sourcing equipment
(PSE) per IEEE 802.3at. 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 active-clamp forward converters or
optimized gate drive for highly-efficient flyback
topologies. 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 TPS23754 has a 15 V converter startup while the
TPS23756 has a 9 V converter startup. The
TPS23754-1 replaces the PPD pin with a no-connect
for increased pin spacing.
D_A
R_APD1
Optional
Interface
DEN
CLS
N/C OR PPD
PAD
V_SS
APD
CTL
FRS
T2P
V_C
V_B
GATE
CS
GAT2
R_DT
R_T2P
L_VC
M1
C_C
M2
C_CL
D_CL
C_IO
C_IN
D_VC1
D_VC2
T1
M4
L_OUT
M3
C_OUT
V_B
R_CTL
C_CTL
R_OB
C_IZ
TLV431
Figure 1. High Efficiency Converter Using TPS23754
V_OUT
R_T2P-OUT
V_T2P-OUT
Type 2 PSE
Indicator
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.
PowerPAD is a trademark of Texas Instruments.
2
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 © 2008–2009, Texas Instruments Incorporated