max5952auaxt Maxim Integrated Products, Inc., max5952auaxt Datasheet - Page 34

• Manufacturer Part Number: max5952auaxt
• Description: Max5952 High-power, Quad, Pse Controller For Power-over-ethernet
• Manufacturer: Maxim Integrated Products, Inc.

High-Power, Quad, PSE Controller
for Power-Over-Ethernet
TSTART[1,0] (Table 20a) programs the startup timers.
Startup time is the time the port is allowed to be in cur-
rent limit during startup. TFAULT_[1,0] programs the
fault time. Fault time is the time allowed for the port to
be in current limit during normal operation. RSTR[1,0]
programs the discharge rate of the TFAULT_ counter
and effectively sets the time the port remains off after
an overcurrent fault. TDISC[1,0] programs the load dis-
connect detection time. The device turns off power to
the port if it fails to provide a minimum power mainte-
nance signal for longer than the load disconnect detec-
tion time (TDISC).
Table 20a. Timing Register
Table 20b. Startup, Fault, and Load Disconnect Timer Values for Timing Register
34
RSTR[1]
RSTR[0]
TSTART[1]
TSTART[0]
TFAULT[1]
TFAULT[0]
TDISC[1]
TDISC[0]
(ADDRESS = 16h)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
SYMBOL
BIT [1:0]
00
01
10
11
ADDRESS = 16h
16 x t
32 x t
64 x t
0 x t
BIT
RSTR
7
6
5
4
3
2
1
0
FAULT
FAULT
FAULT
FAULT
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
t
DISC
1 / 2 x t
1 / 4 x t
2 x t
nominal (350ms, typ)
DISC
Restart timer programming bit 1
Restart timer programming bit 0
Startup timer programming bit 1
Startup timer programming bit 0
Overcurrent timer programming bit 1
Overcurrent timer programming bit 0
Load disconnect timer programming bit 1
Load disconnect timer programming bit 0
DISC
DISC
t
DISC
nominal
nominal
nominal
Set the bits in R16h to scale the t
t
Electrical Characteristics table.
When the MAX5952 shuts down a port due to an
extended overcurrent condition (either during startup or
normal operation), if RSRT_EN is set high, the part does
not allow the port to power back on before the restart
timer (Table 20b) returns to zero. This effectively sets a
minimum duty cycle that protects the external MOSFET
from overheating during a prolonged output overcur-
rent conditions. A reset sets R16h = 00h.
DISC
t
START
to a multiple of their nominal value specified in the
1 / 2 x t
2 x t
4 x t
nominal (60ms, typ)
START
START
START
t
DESCRIPTION
START
nominal
nominal
nominal
t
FAULT
1 / 2 x t
2 x t
4 x t
START
nominal (60ms, typ)
FAULT
FAULT
FAULT
t
FAULT
, t
FAULT
nominal
nominal
nominal
, and