max5965a Maxim Integrated Products, Inc., max5965a Datasheet - Page 23

• Manufacturer Part Number: max5965a
• Description: High-power, Quad, Monolithic, Pse Controllers For Power Over Ethernet
• Manufacturer: Maxim Integrated Products, Inc.

The R1Eh and R1Fh registers control the watchdog
operation. The watchdog function, when enabled, allows
the MAX5965A/MAX5965B to gracefully take over con-
trol or securely shuts down the power to the ports in
case of software/firmware crashes. Contact the factory
for more details.
A3, A2, A1, and A0 represent the 4 LSBs of the chip
address. The complete chip address is 7 bits (see
Table 4).
The 4 LSBs latch on the low-to-high transition of RESET or
after a power-supply start (either on V
inputs default high through an internal 50kΩ pullup resistor
to V
call through a global address 30h (see the Global
Addressing and Alert Response Protocol section).
Table 4. MAX5965A/MAX5965B Address
Figure 4. 2-Wire, Serial-Interface Timing Details
Figure 5. 3-Wire, Serial-Interface Timing Details
0
High-Power, Quad, Monolithic, PSE Controllers
DD
SDAIN
SDAIN/SDA
SCL
. The MAX5965A/MAX5965B also respond to the
t
t
SCL
HD, STA
HD, STA
1
START CONDITION
START CONDITION
0
______________________________________________________________________________________
A3
t
t
LOW
LOW
t
t
R
R
A2
t
t
HIGH
HIGH
t
t
SU, DAT
SU, DAT
DD
t
Address Inputs
t
F
F
A1
or V
t
t
HD, DAT
HD, DAT
Watchdog
EE
A0
). Address
R/W
t
t
SU, STA
SU, STA
REPEATED START CONDITION
REPEATED START CONDITION
for Power over Ethernet
The MAX5965A/MAX5965B operate as a slave that
sends and receives data through an I
wire or 3-wire interface. The interface uses a serial-data
input line (SDAIN), a serial-data output line (SDAOUT),
and a serial-clock line (SCL) to achieve bidirectional
communication between master(s) and slave(s). A mas-
ter (typically a microcontroller) initiates all data transfers
to and from the MAX5965A/MAX5965B, and generates
the SCL clock that synchronizes the data transfer. In
most applications, connect the SDAIN and the SDAOUT
lines together to form the serial-data line (SDA).
Using the separate input and output data lines allows
optocoupling with the controller bus when an isolated
supply powers the microcontroller.
The MAX5965A/MAX5965B SDAIN line operates as an
input. The MAX5965A/MAX5965B SDAOUT operates as
an open-drain output. A pullup resistor, typically 4.7kΩ,
is required on SDAOUT. The MAX5965A/MAX5965B SCL
line operates only as an input. A pullup resistor, typically
4.7kΩ, is required on SCL if there are multiple masters,
or if the master in a single-master system has an open-
drain SCL output.
t
t
HD, STA
HD, STA
I
2
C-Compatible Serial Interface
t
t
SU, STO
SU, STO
CONDITION
CONDITION
STOP
STOP
2
C-compatible, 2-
t
t
BUF
BUF
CONDITION
CONDITION
START
START
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