LTC4271IUF#PBF Linear Technology, LTC4271IUF#PBF Datasheet - Page 18

• Manufacturer Part Number: LTC4271IUF#PBF
• Manufacturer: Linear Technology

Specifications of LTC4271IUF#PBF

• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Pin Count: 24
• Mounting: Surface Mount
• Package Type: QFN EP
• Case Length: 4mm
• Screening Level: Industrial
• Lead Free Status / Rohs Status: Compliant

LTC4270/LTC4271
APPLICATIONS INFORMATION
Extended Power LTPoE ++
A-grade LTC4270/LTC4271 parts add the capability to
autonomously deliver up to 90W of power to the PD.
LTPoE ++ PDs may forgoe 802.3 LLDP support and rely
solely on the LTPoE ++ Physical Classification to negotiate
power with LTPoE ++ PSEs; this greatly simplifies high-
power PD implementations.
LTPoE ++ may be optionally enabled for A-grade LTC4270/
LTC4271s by setting both the High Power Enable and
LTPoE ++ Enable bits.
The higher levels of LTPoE ++ delivery impose additional
layout and component selection constraints. LTC4270 pin
selects allow the AUTO pin mode LTC4271 to autonomously
power up to supported power levels. If the AUTO pin is
high, the XIO1 and XIO0 pins are sampled at reset to de-
termine the maximum deliverable power. PDs requesting
more than the available power limits are not powered.
Table 1. LTPoE ++ AUTO Pin Mode Maximum Delivered Power
Capabilities
POWER
35W
45W
70W
90W
BACKWARDS COMPATIBILITY
The LTC4270/LTC4271 chipset is designed to be backward
compatible with the LTC4266, operating in Type 2 mode,
without software changes; only minor layout changes
are required to implement a fully compliant IEEE 802.3at
design.
Some LTC4266 registers have been obsoleted in the
LTC4270/LTC4271 chipset. The obsoleted registers are not
required for 802.3at compliant PSE operation. For more
details about software differences between the LTC4266
and LTC4270/LTC4271, refer to the LTC4271 Software
Programming document.
Operation with high power mode disabled is obsoleted in
the LTC4270/LTC4271 chipset. All operations previously
available in low power mode are fully implemented as a
subset of the high power mode capabilities.
18
XIO1
0
0
1
1
XIO0
0
1
0
1
OPERATING MODES
The LTC4270/LTC4271 includes 12 independent ports,
each of which can operate in one of four modes: manual,
semi-auto, AUTO pin, or shutdown.
Table 2. Operating Modes
MODE
AUTO Pin
Reserved
Semi-auto
Manual
Shutdown
In manual mode, the port waits for instructions from the
host system before taking any action. It runs a single
detection or classification cycle when commanded to by
the host, and reports the result in its Port Status register.
The host system can command the port to turn on or off
the power at any time.
In semi-auto mode, the port repeatedly attempts to detect
and classify any PD attached to it. It reports the status of
these attempts back to the host, and waits for a command
from the host before turning on power to the port. The
host must enable detection (and optionally classification)
for the port before detection will start.
AUTO pin mode operates the same as semi-auto mode
except it will automatically turn on the power to the port if
detection is successful. AUTO pin mode will autonomously
set the I
operational mode is only valid if the AUTO pin is high.
In shutdown mode, the port is disabled and will not detect
or power a PD.
Regardless of which mode it is in, the LTC4270/LTC4271
will remove power automatically from any port that gener-
ates a current limit fault. It will also automatically remove
power from any port that generates a disconnect event if
disconnect detection is enabled. The host controller may
also command the port to remove power at any time.
CUT
AUTO
PIN
1
0
0
0
0
and I
OPMD DETECT/
LIM
11b
11b
10b
01b
00b
values based on the class result. This
Disabled
at Reset
Request
Enabled
Enabled
CLASS
Upon
Once
Host
N/A
Automatically
POWER-UP
Disabled
Request
Request
Upon
Upon
N/A
ASSIGNMENT
AUTOMATIC
I
CUT
N/A
Yes
No
No
No
/I
LIM
42701f