max5965a Maxim Integrated Products, Inc., max5965a Datasheet - Page 21

• Manufacturer Part Number: max5965a
• Description: High-power, Quad, Monolithic, Pse Controllers For Power Over Ethernet
• Manufacturer: Maxim Integrated Products, Inc.

Connect the gate of the external n-channel MOSFET to
GATE_. An internal 50µA current source pulls GATE_ to
(V
current source pulls down GATE_ to V
MOSFET.
The pullup and pulldown current controls the maximum
slew rate at the output during turn-on or turn-off. Use
the following equation to set the maximum slew rate:
Table 3. Automatic ICUT Programming
Figure 3a. Foldback Current Characteristics
V
CL_DISC
(V
EE
SU_LIM
RS
V
High-Power, Quad, Monolithic, PSE Controllers
SU_LIM
- V
0
1
1
1
1
1
1
1
1
1
1
1
1
+ 10V) to turn on the MOSFET. An internal 40µA
EE
/ 3
)
CLASSIFICATION
6 or Illegal
6 or Illegal
6 or Illegal
6 or Illegal
RESULT
PORT
______________________________________________________________________________________
Any
0, 3
4, 5
Δ
28V
1
2
5
5
4
4
V
Δ
OUT
t
=
MOSFET Gate Driver
I
GATE
C
ENx_CL6 EN_HP_ALL EN_HP_CL6 EN_HP_CL5
GD
X
X
X
X
X
X
X
X
X
0
1
1
1
48V
EE
to turn off the
X
X
X
X
0
1
1
1
1
X
1
1
0
(V
OUT_
- V
EE
)
for Power over Ethernet
X
X
X
X
X
X
X
X
X
X
1
0
X
where C
DRAIN of the external MOSFET. Current limit and the
capacitive load at the drain control the slew rate during
startup. During current-limit regulation, the
MAX5965A/MAX5965B manipulate the GATE_ voltage
to control the voltage at SENSE_ (V
activates if V
(V
amount of overshoot. The maximum fast pulldown cur-
rent is 100mA.
During turn-off, when the GATE_ voltage reaches a
value lower than 1.2V, a strong pulldown switch is acti-
vated to keep the MOSFET securely off.
Figure 3b. Foldback Current Characteristics for High-Power Mode
(V
SU_LIM
RS
V
V
SU_LIM
- V
TH_FB
EE
)
GD
). The fast pulldown current increases with the
X
X
X
X
X
1
0
X
X
X
X
X
x
is the total capacitance between GATE and
RS
EN_HP_CL4
overshoots the limit threshold
10V
X
X
X
X
X
X
X
X
X
X
X
1
0
User programmed
ICUT = 110
ICUT = 111
ICUT = 000
ICUT = 000
ICUT = R24h[6:4]
ICUT = 000
ICUT = R24h[6:4]
ICUT = 000
—
(See Table 35a)
ICUT = 000
ICUT = 000
RS
RESULTING ICUT
REGISTER BITS
). A fast pulldown
48V
(V
OUT_
- V
EE
21
)