Rainbow Electronics MAX5971B User Manual
Page 34
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MAX5971B
Single-Port, 40W, IEEE 802.3af/at,
PSE Controller with I
2
C
Miscellaneous Configuration 1 Register (R17h)
The miscellaneous configuration 1 register (R17h, Table
25) is used for several functions that do not cleanly fit
within one of the other configuration categories. On a
power-up or after a reset condition, this register is set to
a default value of 0xC0h. Therefore, by default, INT_EN
(R17h[7]) and RSTR_EN (R17h[6]) are set to 1, enabling
both INT functionality and the autorestart protection timer.
Setting CL_DISC (R17h[2] to 1 enables current-limit
programming regardless of the classification result
through the ICUT[2:0] register (R2Ah). Setting OUT_ISO
(R17h[1]) to 1, forces DET to a high-impedance state.
Setting HP_TIME high enables the higher current limits
needed for type 2 PDs even during startup (during the
time after port power-up but before t
START
has expired).
Pushbutton Registers (R18h to R1Ah)
Reserved Register (R18h)
Register R18h is at this time reserved. Writing to this
register has no effect (the address autoincrement still
updates) and any attempt to read this register returns
all zeros.
Power Enable Pushbutton Register (R19h)
The power enable pushbutton register (R19h, Table
26) is used to manually power the port on or off. On a
power-up or after a reset condition, this register is set to
a default value of 0x00h. Setting PWR_ON (R19h[0]) to
1 turns on power to the port. PWR_ON commands are
ignored when the port is already powered and during
shutdown. During detection or classification, if a 1 is
written to PWR_ON, the MAX5971B gracefully terminates
the detection/classification routine and turns on power
to the port. The MAX5971B also ignores PWR_ON com-
mands when operating in auto mode. Setting PWR_OFF
(R19h[4]) to 1 turns off power to the port. PWR_OFF
commands are ignored when the port is already off and
during shutdown. After the appropriate command is
executed (port power on or off), the PWR_ON/PWR_OFF
bit resets back to 0.
Global Pushbutton Register (R1Ah)
The global pushbutton register (R1Ah, Table 27) is used
to manually clear interrupts and to initiate global and
port resets. On a power-up or after a reset condition, this
register is set to a default value of 0x00h. Writing a 1 to
Table 24. Timer Values for Timing Register
Table 25. Miscellaneous Configurations 1 Register
BIT [1:0]
(ADDRESS = 16h)
t
RESTART
t
DISC
t
START
t
FAULT
00
16 x t
FAULT
t
DISC
nominal
(350ms, typ)
t
START
nominal
(60ms, typ)
t
FAULT
nominal
(60ms, typ)
01
32 x t
FAULT
¼ x t
DISC
nominal
½ x t
START
nominal
½ x t
FAULT
nominal
10
64 x t
FAULT
½ 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
ADDRESS = 17h
DESCRIPTION
SYMBOL
BIT NO.
TYPE
INT_EN
7
R/W
A logic-high enables INT functionality
RSTR_EN
6
R/W
A logic-high enables the autorestart protection timer (set by the RSRT[1:0] bits)
Reserved
5
—
Reserved
Reserved
4
—
Reserved
Reserved
3
—
Reserved
CL_DISC
2
R/W
A logic-high enables
current-limit programming regardless of the classification result through
the ICUT[2:0] register
OUT_ISO
1
R/W
A logic-high forces DET to a high-impedance state. Does not interfere with other circuit operation.
HP_TIME
0
R/W
A logic-high enables the higher current limit for Type 2 PDs during startup.