Datasheet
GATE
RTN
V
C
CS
V
DD
V
SS
DEN
BLNK
FRS
V
B
CTL
CLS
1
2
3
4
5
6
7
8
14
13
11
10
9
12
APD
V
DD1
TPS23753A
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SLVS933B –JULY 2009–REVISED JANUARY 2010
ELECTRICAL CHARACTERISTICS (continued)
PoE and Control
[V
DD
= V
DD1
] or [V
DD1
= RTN], V
VC-RTN
= 0 V, all voltages referred to V
SS
. Typical specifications are at 25°C.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
THERMAL SHUTDOWN
Turn off temperature 135 145 155 °C
Hysteresis
(2)
20 °C
(2) These parameters are provided for reference only.
DEVICE INFORMATION
TOP VIEW
Table 1. Terminal Functions
TERMINAL
I/O DESCRIPTION
NO. NAME
1 CTL I The control loop input to the PWM (pulse width modulator). Use V
B
as a pull up for CTL.
5 V bias rail for dc/dc control circuits. Apply a 0.1 mF to RTN. V
B
may be used to bias an external
2 V
B
O
optocoupler for feedback.
Dc/dc converter switching MOSFET current sense input. Connect CS to the high side of R
CS
per
3 CS I
Figure 1.
Dc/dc converter bias voltage. The internal startup current source and converter bias winding output
4 V
C
I/O power this pin. Connect a 0.22 mF minimum ceramic capacitor to RTN, and a larger capacitor to
facilitate startup.
5 GATE O Gate drive output for the dc/dc converter switching MOSFET.
6 RTN RTN is the negative rail input to the dc/dc converter and output of the PoE hotswap.
7 V
SS
Negative power rail derived from the PoE source.
8 V
DD1
Source of dc/dc converter startup current. Connect to V
DD
for most applications.
9 V
DD
Positive input power rail for PoE interface circuit. Derived from the PoE source.
Connect a 24.9 kΩ resistor from DEN to V
DD
to provide the PoE detection signature. Pulling this pin
10 DEN I/O
to V
SS
during powered operation causes the internal hotswap MOSFET to turn off.
11 CLS O Connect a resistor from CLS to V
SS
to program the classification current per Table 2.
Pull APD above 1.5 V to disable the internal PD hotswap switch, forcing power to come from an
12 APD I
external adapter. Connect to the adapter through a resistor divider.
Connect to RTN to utilize the internally set blanking period or connect through a resistor to RTN to
13 BLNK I/O
program the blanking period.
14 FRS I/O Connect a resistor from FRS to RTN to program the converter switching frequency.
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