AS1135

Product Brief

AS1135 Product Brief

March 2008

Page 2

Thermal

Limit

Protection

UVLO

AS1135

PD controller

Local

Adapter

Control

DC-DC

Controller

With

Managed

Emissions

Control

AT

Detection

Signature

Extended

Classification

& MPS

Current

Limit/

Sense

Surge

Protection

Figure 2: Top-Level Block Diagram of the AS1135

Functional Description

The AS1135 is a fully integrated PD that includes surge protection,

PD controller, DC-DC controller, local adapter control and

Emission control functions. This includes all the functions and

features required to build IEEE 802.3af/at complaint Power over

Ethernet (PoE) system. The optimized architecture of the AS1135

reduces external component cost in a small footprint package

while providing high performance.

PD Controller

The AS1135 PD controller interface is designed to provide a fully

compliant IEEE 802.3at (Draft 2.0) as both Type 1 and Type 2 PD.

The PD Controller provides the following major functions:

•

Signature detection

•

2-Event Physical Layer Classification

•

Type 2 PSE Detection Indicator (ATDET)

•

Maitain power signature (MPS)

•

Current sense/limit

•

Under voltage lockout (UVLO)

•

Thermal limit protection

The AS1135 includes new 2-event classification feature based on

802.3at (Draft 2.0) standard to indicate to a Type 2 PSE that the

PD is also a Type 2 PD and can accept more than 13W of input

power.

The ATDET output indicator stays low if the PD connects to a

Type 1 PSE (13W), and goes high if the PD connects to a Type 2

PSE (30W). This can be used by the system micro-controller to

self-configure the system based on available power. ATDET

stays high under local power since higher power is available

through the local adapter.

DC-DC Controller

The integrated DC-DC controller operates from a switched input

voltage and includes soft-start and current limiting. After the input

power and enable signals are asserted, the DC-DC controller starts

up. The controller provides control signals to external MOSFET

switche and uses an external sense resistor to sense the

transformer primary current.

The DC-DC architecture is a current mode controller which can be

configured with external component changes for either flyback,

forward or buck topologies. Both non-isolated and isolated

switching technologies are supported. The PWM switching signal is

controlled for low radiated and conducted emissions.

Local Adapter Control

Even with the convenience of PoE, many systems are designed to

work with both the PoE and Local Power supplies to ensure

broader deployment. The integrated local adapter controller

enables the AS1135 to be used with a wall power adapter in wide

range of 10-57V. The local adapter is OR-ed in after the hot-swap

FET. The internal detector disabled the hot-swap FET when local

power is available. This allows local power to have higher priority

than the PoE power irrespective of the relative voltages local or

PoE connections. If system design requires higher voltage based

priority selection, then local power can also be OR-ed in at the front

end diode bridge to take benefit of inrush/current limiting features.

For More Information

Contact us at mailto:marcom@akrossilicon.com, or

Akros Silicon, Inc., 275 Turn Pike Drive, Folsom, CA95630

http://www.AkrosSilicon.com