MAX5980 MAXIM [Maxim Integrated Products], MAX5980 Datasheet - Page 42

• Manufacturer Part Number: MAX5980
• Description: Quad, IEEE 802.3at/af PSE Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Quad, IEEE 802.3at/af PSE Controller
for Power-over-Ethernet
The Port Current registers (Tables 32 and 33) provide
port current readout when a port is powered on. On
a power-up or after a reset condition, these registers
are both set to a default value of 00h. The Port Current
Readout registers have 16 total bits, but the 3 highest
bits (MSBs) and the 4 lowest bits (LSBs) are hardwired
to 0. The port current readout has 9 bits of overall actual
Table 32. Port Current Register (LSB)
Table 33. Port Current Register (MSB)
42
ADDRESS = 30h, 34h, 38h, 3Ch
ADDRESS = 31h, 35h, 39h, 3Dh
Port Current Registers (R30h, R31h, R34h, R35h,
SYMBOL
SYMBOL
IP_[15:8]
IP_[7:0]
Current/Voltage Readout Registers
BIT NO.
BIT NO.
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
R38h, R39h, and R3Ch, R3Dh)
TYPE
TYPE
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
IP_[7:0] (LSB). Lower 8 bits of the 16-bit port current readout. IP_[3:0] are configured
to be hardwired to 0.
IP_[15:8] (LSB). Lower 8 bits of the 16-bit port current readout. IP_[15:13] are config-
ured to be hardwired to 0.
(R30h–R3Fh)
resolution. To avoid the LSB register changing while
reading the MSB, the register contents are frozen if
addressing byte points to either of the current readout
registers. During normal operation, the port output cur-
rent can be calculated as:
where N
rent readout. The ADC saturates both at full scale and at
zero, resulting in poor current readout accuracy near the
top and bottom codes.
IP_
DESCRIPTION
DESCRIPTION
is the decimal value of the 16-bit port cur-
I
OUT_
= N
IP_
x 122.07FA/count