Texas Instruments TPS23751 Evaluation Module TPS23751EVM-104 TPS23751EVM-104 Datenbogen
Produktcode
TPS23751EVM-104
T
PS
2
3
7
5
2
P 2
/2
WAKE
LED
SLPb
MODE
R
SL
R
MO
D
E
V
B
SLPb
MODE
S
WAKE
R
PB
R
LED
Sl
e
e
p
Mo
d
e
Pro
ce
sso
r
C
o
n
tro
l
In
te
rf
a
ce
R
W
AKE
R
SLN
R
MPS
V
C
OPTO4
OPTO5
OPTO6
T
PS
2
3
7
5
2
P 1
/2
M1
R
C
S
D
VC1
GATE
V
C
CS
C
VC
CTL
5
8
V
0.1u
F
R
D
EN
F
ro
m
Et
h
e
rn
e
t
Pa
irs
1,2
V
SS
C
IN
F
ro
m
Et
h
e
rn
e
t
Pa
irs
3,4
CLS
DEN
RT
T2P
R
C
L
S
Type 2 PSE
Indicator
R
T
V
B
C
VB
R
F
BU
R
F
BL
TLV431
R
OB
C
IZ
V
OUT
PAD
V
D
D
SRD
M2
R
T2P
D
A
R
APD
2
R
APD1
Ad
a
p
te
r
R
SR
T
1
APD
R
SR
T
2
C
O
U
T
T1
C
IO
V
B
R
C
T
L
C
C
T
L
R
SR
D
R
VC
D
OUT
V
OUT
SRT
AR
T
N
OPTO2
OPTO2
OPTO1
OPTO1
OPTO3
OPTO3
V
OUT
PBb
R
T
N
SLVSB97C – JULY 2012 – REVISED JANUARY 2014
APPLICATION INFORMATION
The TPS23751 and TPS23752 support power supply topologies that require a single PWM gate drive with
current-mode control.
current-mode control.
provides an example of a synchronous rectifier flyback converter. Selecting a
converter topology along with a design procedure is beyond the scope of this applications section. Examples to
help in programming the TPS23751 and TPS23752 are shown below. Additional special topics are included to
explain the ORing capabilities, frequency dithering, and other design considerations. For more specific converter
design examples refer to the following application notes:
•
help in programming the TPS23751 and TPS23752 are shown below. Additional special topics are included to
explain the ORing capabilities, frequency dithering, and other design considerations. For more specific converter
design examples refer to the following application notes:
•
Designing with the TPS23753 Powered Device and Power Supply Controller,
•
Advanced Adapter ORing Solutions using the TPS23753,
•
TPS23751EVM-104 EVM: Evaluation Module for TPS23751,
•
TPS23752EVM-145 EVM: Evaluation Module for TPS23752,
Figure 29. TPS23752 Application Circuit
Input Bridges and Schottky Diodes
Using Schottky diodes instead of PN junction diodes for the PoE input bridges reduces the power dissipation in
these devices by about 30%. There are, however, some things to consider when using them.
these devices by about 30%. There are, however, some things to consider when using them.
The IEEE standard specifies a maximum backfeed voltage of 2.8 V. A 100 k
Ω resistor is placed between the
unpowered pairs and the voltage is measured across the resistor. Schottky diodes often have a higher reverse
leakage current than PN diodes, making this a harder requirement to meet. To compensate, use conservative
design for diode operating temperature, select lower-leakage devices where possible, and match leakage and
temperatures by using packaged bridges.
leakage current than PN diodes, making this a harder requirement to meet. To compensate, use conservative
design for diode operating temperature, select lower-leakage devices where possible, and match leakage and
temperatures by using packaged bridges.
Schottky diode leakage currents and lower dynamic resistances can impact the detection signature. Setting
reasonable expectations for the temperature range over which the detection signature is accurate is the simplest
solution. Increasing R
reasonable expectations for the temperature range over which the detection signature is accurate is the simplest
solution. Increasing R
DEN
slightly may also help meet the requirement.
Schottky diodes have proven less robust to the stresses of ESD transients than PN junction diodes. After
exposure to ESD, Schottky diodes may become shorted or leak. Care must be taken to provide adequate
protection in line with the exposure levels. This protection may be as simple as ferrite beads and capacitors.
exposure to ESD, Schottky diodes may become shorted or leak. Care must be taken to provide adequate
protection in line with the exposure levels. This protection may be as simple as ferrite beads and capacitors.
As a general recommendation, use 1 A or 2 A, 100 V rated discrete or bridge diodes for the input rectifiers.
30
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