PM8800ATR STMicroelectronics, PM8800ATR Datasheet - Page 14

• Manufacturer Part Number: PM8800ATR
• Description: IC POE-PD PWM CTLR 16-HTSSOP
• Manufacturer: STMicroelectronics

Specifications of PM8800ATR

• Applications: Power Over Ethernet (PoE)
• Interface: IEEE 802.3af
• Voltage - Supply: 10 V
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Mounting Type: Surface Mount
• For Use With: 497-6366 - BOARD EVAL FOR PM8800A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6897-2; PM8800ATR

Device description and operation
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Device description and operation
The PM8800A is a monolithic device embedding an IEEE 802.3af compliant PD interface
together with a current mode pulse width modulator to be used in all power over Ethernet
powered devices.
In addition to the standard.3af features, PM8800A anticipates some features of the forth-
coming.3at standard, specifically targeting appliances or systems requiring higher power
with respect to the 12.95 W allowed by standard PSE.
The PD interface integrates the 24.5 kΩ signature resistor used in detection and disabled
during the rest of operating modes. Classification is done through an external resistor
detached when classification is over, in order to save power.
The PM8800A integrates standard compliant UVLO thresholds to determine normal operat-
ing mode (UVLO rising) or recognize disconnection (UVLO falling).
A graphical representation of the voltage thresholds and hysteresis during all the operating
phases is depicted in the following figure:
Figure 6.
For input voltages in the range 1.5 to 11.5 V, PM8800A exposes a 24.5 kΩ resistance. After
detection is over, the internal resistor is disabled and the external classification resistor is
presented. When classification is over, the external resistor is disconnected and the
PM8800A wait for the input voltage to overpass the UVLO voltage.
The hot-swap MOSFET is specifically designed to have a low R
tion losses and sustain up to 800 mA. A constant dissipated power method is used to limit
the current in the in-rush phase. The integrated in-rush current limit controls in a safe man-
ner the current flowing through the MOSFET, shortening the duration of the hot-swap event
itself. Designers have the possibility to further limit the current in the in-rush by acting on the
proper programming resistor.
Designers have the possibility to set the limit of the current through the interface during nor-
mal operation. For non standard application, this limit exceeds the 350 mA foreseen by the
802.3af and can reach up to 800 mA.
1.5V
State diagram of the PM8800A interface depending on the input voltage
Detection
10.1V
11.5V
Classification
21V
Wait for turn-on
23V
30.5V
31.5V
38.5V
Powered
DSon
to contain the conduc-
Input voltage
PM8800A