Rainbow-electronics MAX5965B Manual de usuario descargar pdf (Pagina 35)

MAX5965A/MAX5965B

High-Power, Quad, Monolithic, PSE Controllers

for Power over Ethernet

______________________________________________________________________________________ 35

Table 20a. Timing Configuration Register

ADDRESS = 16h

SYMBOL BIT R/W

DESCRIPTION

RSTR[1] 7 R/W Restart timer programming bit 1

RSTR[0] 6 R/W Restart timer programming bit 0

TSTART[1] 5 R/W Startup timer programming bit 1

TSTART[0] 4 R/W Startup timer programming bit 0

TFAULT[1] 3 R/W Overcurrent timer programming bit 1

TFAULT[0] 2 R/W Overcurrent timer programming bit 0

TDISC[1] 1 R/W Load disconnect timer programming bit 1

TDISC[0] 0 R/W Load disconnect timer programming bit 0

Table 20b. Startup, Fault, and Load Disconnect Timer Values for Timing Register

BIT [1:0]

(ADDRESS = 16h)

RSTR t

DISC

START

FAULT

00 16 x t

FAULT

DISC

nominal (350ms, typ) t

START

nominal (60ms, typ) t

FAULT

nominal (60ms, typ)

01 32 x t

FAULT

x t

DISC

nominal

x t

START

nominal

x t

FAULT

nominal

10 64 x t

FAULT

x t

DISC

nominal 2 x t

START

nominal 2 x t

FAULT

nominal

11 0 x t

FAULT

2 x t

DISC

nominal 4 x t

START

nominal 4 x t

FAULT

nominal

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).

Set the bits in R16h to scale the t

START

, t

FAULT

, and

DISC

to a multiple of their nominal value specified in the

Electrical Characteristics

table.

When the MAX5965A/MAX5965B shut down a port due

to an extended overcurrent condition (either during

startup or normal operation), if RSTR_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 effec-

tively sets a minimum duty cycle that protects the exter-

nal MOSFET from overheating during prolonged output

overcurrent conditions. A reset sets R16h = 00h.

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 51 52

MAX5965A/MAX5965B 1

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Rainbow-electronics MAX5965B Manual de usuario Pagina 35

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