LTC4258 datasheet(11/28 Pages) LINER

11 / 28 page

LTC4258

4258p

rupt register as the Supply Fault bit. The remaining bits in

the register are reserved and will always read as 0. The

Supply Event bits latch high and will remain high until

cleared by reading from address 0Bh.

Supply Event CoR (Address 0Bh): Supply Event Register,

Clear on Read. Read this address to clear the Fault Event

and reading address 0Bh clears all bits at both addresses.

Status Registers

Port 1 Status (Address 0Ch): Port 1 Status Register, Read

Only. This register reports the most recent detection and

classification results for port 1. Bits 0-2 report the status

of the most recent detection attempt at the port and bits 4-6

report the status of the most recent classification attempt

at the port. If power is on, these bits report the detection/

classification status present just before power was turned

on. If power is turned off at the port for any reason, all bits

in this register will be cleared. See Table 1 for detection and

classification status bit encoding.

Port 2 Status (Address 0Dh): Port 2 Status Register, Read

Only. See Port 1 Status.

Port 3 Status (Address 0Eh): Port 3 Status Register, Read

Only. See Port 1 Status.

Port 4 Status (Address 0Fh): Port 4 Status Register, Read

Only. See Port 1 Status.

Power Status (Address 10h): Power Status Register, Read

Only. The lower four bits in this register report the switch

on/off state for the corresponding ports. The upper four

bits (the power good bits) indicate that the drop across the

power switch and sense resistor for the corresponding ports

is less than 2V (typ) and power start-up is complete. The

power good bits are latched high and are only cleared when

a port is turned off or the LTC4258 is reset.

Pin Status (Address 11h): External Pin Status, Read Only.

This register reports the real time status of the AUTO

(Pin 35) and AD0-AD3 (Pins 7-10) digital input pins. The

logic state of the AUTO pin appears at bit 0 and the AD0-AD3

pins at bits 2-5. The remaining bits are reserved and will

read as 0. AUTO affects the initial states of some of the

LTC4258 configuration registers at start-up but has no

effect after start-up and can be used as a general purpose

input if desired, as long as it is guaranteed to be in the

appropriate state at start-up.

Configuration Registers

Operating Mode (Address 12h): Operating Mode Configu-

ration, Read/Write. This register contains the mode bits for

each of the four ports in the LTC4258. See Table 1 for mode

bit encoding. At power-up, all bits in this register will be set

to the logic state of the AUTO pin (Pin 35). See Operating

Modes in the Applications Information section.

Disconnect Enable (Address 13h): Disconnect Enable

enable or disable DC disconnect detection circuitry at the

corresponding port. If the DC Discon Enable bit is set the

port circuitry will turn off power if the current draw at the

port falls below IMINformorethantDIS.IMINisequaltoVMIN/

RS, where RS is the sense resistor and should be 0.5Ω for

IEEE 802.3af compliance. If the bit is clear the port will not

remove power due to low current.

Detect/Class Enable (Address 14h): Detection and Clas-

sification Enable, Read/Write. The lower four bits of this reg-

ister enable the detection circuitry at the corresponding port

if that port is in Auto or Semiauto mode. The upper four bits

enable the classification circuitry at the corresponding port

if that port is in Auto or Semiauto mode. In manual mode,

setting a bit in this register will cause the LTC4258 to per-

form one classification or detection cycle on the corre-

sponding port. Writing to the Detect/Class Restart PB (18h)

has the same effect without disturbing the Detect/Class

Enable bits for other ports.

Timing Config (Address 16h): Global Timing Configuration,

Read/Write. Bits 0-1 program tDIS, the time duration before

a port is automatically tuned off after the PD is removed.

The LTC4258 can be programmed to monitor whether port

current is below IMIN (DCconnect)orportimpedanceishigh

(AC disconnect). Bits 2-3 program tICUT, the time during

which a port’s current can exceed ICUT without it being

turned off. If the current is still above ICUT after tICUT, the

LTC4258 will indicate a tICUT fault and turn the port off. Bits

LTC4258 Datasheet(PDF) 11 Page - Linear Technology

LTC4258 Datasheet(HTML) 11 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL