Datasheet
10.4
10.45
10.5
10.55
10.6
10.65
10.7
10.75
10.8
10.85
10.9
39 44 49 54
V
DD
(V)
MPS Supply Current (mA)
T
A
= −40°C
T
A
= 25°C
T
A
= 125°C
G015
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
−40 −20 0 20 40 60 80 100 120
Temperature (°C)
r
DS(on)
(Ω)
G013
10.35
10.4
10.45
10.5
10.55
10.6
10.65
10.7
10.75
10.8
0 2 4 6 8 10
I
LED
(mA)
MPS Supply Current (mA)
T
A
= −40°C
T
A
= 25°C
T
A
= 125°C
G014
TPS23751
TPS23752
www.ti.com
SLVSB97C –JULY 2012–REVISED JANUARY 2014
TYPICAL CHARACTERISTICS (continued)
r
DS(on)
MPS SUPPLY CURRENT
vs vs
TEMPERATURE LED CURRENT
Figure 17. Figure 18.
MPS SUPPLY CURRENT
vs
SUPPLY VOLTAGE
Figure 19.
DETAILED DESCRIPTION
PoE OVERVIEW
The following text is intended as an aid in understanding the operation of the TPS23751 and TPS23752 but not
as a substitute for the IEEE 802.3at standard. The IEEE 802.3at standard is an update to IEEE 802.3-2008
clause 33 (PoE), adding high-power options and enhanced classification. Generally speaking, a device compliant
to IEEE 802.3-2008 is referred to as a type 1 device, and devices with high power and enhanced classification
are referred to as type 2 devices. Standards change and should always be referenced when making design
decisions.
The IEEE 802.3at standard defines a method of safely powering a PD (powered device) over a cable by power
sourcing equipment (PSE), and then removing power if a PD is disconnected. The process proceeds through an
idle state and three operational states of detection, classification, and operation. The PSE leaves the cable
unpowered (idle state) while it periodically looks to see if something has been plugged in; this operation is
referred to as detection. The low power levels used during detection are unlikely to damage devices not designed
for PoE. If a valid PD signature is present, the PSE may inquire how much power the PD requires; this operation
is referred to as classification. The PSE may then power the PD if it has adequate capacity.
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