Rainbow Electronics MAX5971B - Manual (Page 29)

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MAX5971B
Single-Port, 40W, IEEE 802.3af/at,
PSE Controller with I 2 C
Supply Event Register (R0Ah/R0Bh)
The MAX5971B continuously monitors the power sup-
plies and sets the appropriate bits in the supply event
register (R0Ah/R0Bh, Table 12). On power-up or after
a reset condition, the supply event register is set to a
default value of 00h. V
EE_OV is set to 1 whenever V EE
exceeds its overvoltage threshold. V EE_UV is set to 1
whenever V EE falls below its undervoltage threshold.
A thermal shutdown circuit monitors the temperature
of the die and resets the MAX5971B if the temperature
exceeds +150NC. TSD is set to 1 after the MAX5971B
returns to normal operation.
When V
EE is below its UVLO threshold, the MAX5971B is
in reset mode and securely holds the port off. When V EE
rises above its UVLO threshold, the device comes out of
reset and the V
EE_UVLO bit in the supply event register
is set to 1.
As with any of the other event registers, the supply
event register has two addresses. When read through
the R0Ah address, the content of the register is left
unchanged. When read through the CoR R0Bh address,
the register content is reset to the default state.
The Status Registers (R0Ch to R11h)
Port Status Register (R0Ch)
The port status register (R0Ch, Table 13) records the
results of the port detection and classification at the end
of each phase in three encoded bits. On power-up or
after a reset condition, the port status register is set to a
default value of 00h. Tables 14 and 15 show the detection
and classification result decoding charts, respectively.
For CLC_EN = 0 (R23h[5]), the detection result is shown
in Table 13. When CLC_EN = 1, the MAX5971B allows
valid detection of high capacitive loads of up to 47FF, typ.
As a protection, when POFF_CL (R12h[3], Table 18) is set
to 1, the MAX5971B prohibits turning on power to the port
that returns a status 111 after classification.
Table 12. Supply Event Register
Table 13. Port Status Register
ADDRESS = 0Ch
DESCRIPTION
SYMBOL BIT NO. TYPE
Reserved 7 — Reserved
CLASS
6 R CLASS[2]
5 R CLASS[1]
4 R CLASS[0]
Reserved 3 — Reserved
DET_ST
2 R DET[2]
1 R DET[1]
0 R DET[0]
ADDRESS = 0Ah 0Bh
DESCRIPTION
SYMBOL BIT NO. TYPE TYPE
TSD 7 R CoR Overtemperature shutdown
Reserved 6 — — Reserved
Reserved 5 — — Reserved
V EE_UVLO 4 R CoR V EE undervoltage lockout condition
V EE_OV 3 R CoR V EE overvoltage condition
V EE_UV 2 R CoR V EE undervoltage condition
Reserved 1 — — Reserved
Reserved 0 — — Reserved