MAX5971BETI+ Maxim Integrated Products, MAX5971BETI+ Datasheet - Page 15

• Manufacturer Part Number: MAX5971BETI+
• Description: Hot Swap & Power Distribution IEEE 802.3af/at PSE Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX5971BETI+

• Lead Free Status / Rohs Status: Details

3) Software Reset. To initiate a software reset, write a
4) Thermal Shutdown. The device enters thermal shut-
At the end of a reset event, the MAX5971B latches in
the state of MIDSPAN, LEGACY, and OSC. During nor-
mal operation, changes to the MIDSPAN and LEGACY
inputs are ignored, and these inputs can be changed
at any time prior to the end of a reset state. Changes to
OSC input during normal operation can impact device
functionality. Therefore, OSC is only changed while the
device is held in a reset state (or powered down), and
OSC then latches in when the reset state ends (other
schematic modifications may be needed, see Figures
15 and 16).
Set RESET_P (R1Ah[0]) high anytime during normal
operation to turn off port power and clear the port event
and status registers. Port reset does not initiate a global
device reset.
In midspan mode, the device adopts cadence timing dur-
ing the detection phase. When cadence timing is enabled
and a failed detection occurs, the port waits between 2s
and 2.4s before attempting to detect again. Midspan
mode is activated by setting MIDSPAN high and then
powering or resetting the device. Alternatively, midspan
mode is software enabled by setting BCKOFF (R15h[0],
Table 22) to a logical 1. By default, the MIDSPAN input
is internally pulled high, enabling cadence timing. Force
MIDSPAN low to disable this function.
The MAX5971B provides four operating modes to suit dif-
ferent system requirements. By default, auto mode allows
the device to operate automatically at its default settings
without any software. Semiautomatic mode automatically
detects and classifies a device connected to the port
after initial software activation, but does not power up the
port until instructed to by software. Manual mode allows
total software control of the device and is useful for sys-
tem diagnostics. Shutdown mode terminates all activities
and securely turns off power to the port.
Switching between auto, semiautomatic, and manual
mode does not interfere with the operation of the out-
put port. When the port is set into shutdown mode, all
logical 1 to the RESET_IC register (R1Ah[4]) any time
after power-up. Reset clears automatically and all
registers are set to their default states.
down at 150NC. The device exits thermal shutdown
and is reset once the temperature drops below 130NC.
______________________________________________________________________________________
Operation Modes
Single-Port, 40W, IEEE 802.3af/at,
Midspan Mode
Port Reset
PSE Controller with I
port operations are immediately stopped and the port
remains idle until shutdown mode is exited.
By default, the MAX5971B enters auto mode after
the reset condition is cleared. To manually place the
MAX5971B into auto mode from any other mode, set
P_M[1:0] (R12h[1:0]) to [11] during normal operation
(see Tables 18 and 19).
In auto mode, the MAX5971B performs detection and
classification, and powers up the port automatically if a
valid PD is connected to the port. If a valid PD is not con-
nected at the port, the MAX5971B repeats the detection
routine continuously until a valid PD is connected.
When entering auto mode, the DET_EN and CLASS_EN
bits (R14h[0] and R14h[4], Table 21) are set to high
and stay high unless changed by software. Using soft-
ware to set DET_EN and/or CLASS_EN low causes the
MAX5971B to skip detection and/or classification. As a
protection, disabling the detection routine in auto mode
does not allow the corresponding port to power up,
unless the DET_BY bit (R23h[4], Table 32) is set to 1.
The MAX5971B is put into semiautomatic mode by set-
ting P_M[1:0] (R12h[1:0]) to [10] during normal operation
(see Tables 18 and 19). In semi mode, the MAX5971B,
upon request, performs detection and/or classification
repeatedly but does not power up the port. To power
the port, set the PWR_ON bit (R19h[0], Table 26) to 1.
This immediately terminates the detection/classification
routine and turns on power to the port.
DET_EN and CLASS_EN (R14h[0] and R14h[4], Table 21)
default to low in semiautomatic mode. Use software to set
DET_EN (R14h[0]) to 1 to start the detection routine and
CLASS_EN (R14h[4]) to 1 to enable classification routine.
They are reset every time the software commands a
power-off of the port, either through a reset event or by
writing a 1 to the PWR_OFF bit (R19h[4]). In any other
case, the status of the bits is left unchanged (including
when the state machine turns off the power when a load
disconnect or a fault condition is encountered).
The MAX5971B is placed in manual mode by setting
P_M[1:0] (R12h[1:0]) to [01] during normal operation
(see Tables 18 and 19). Manual mode allows the soft-
ware to dictate the sequence of operation. Write a 1 to
both R14h[0] (DET_EN) and R14h[4] (CLASS_EN) to
start detection and classification operations, respec-
tively, and in that priority order. In manual mode, after
Semiautomatic (Semi) Mode
Auto (Automatic) Mode
Manual Mode
2
C
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