AN095
Application Note
October 2017 – Revision 04a Page 1 Company Confidential
Overview
This document provides an overview of a design using the Kinetic KTA1550 device with a voltage-mode PHY;
the specific design example in this document shows the KTA1550 used with the Broadcom BCM54610 PHY.
The KTA1550 is a Dual Channel Active EMI suppressor for Ethernet Applications for both Power over Ethernet
(PoE) and traditional non-PoE Ethernet systems, where compliance to tougher EMI Emissions (Class B), EMI
Immunity standards (Level 2/3 or higher) and / or ESD (±25kV Air Discharge / ±12kV CDE) is required.
There are various voltage-mode PHYs in the market, ranging from standalone to embedded in IP processors.
As such, the presented method of use applies to a general category, and some fine tuning may be necessary
for other part numbers or manufacturers.
This document is to be used in conjunction with relevant parts datasheets and application notes that provide
generic design guidelines for the KTA1550 part.
Design Notes
For a more detailed description of the KTA1550 technology and applications, please refer to additional reference
material along with these design notes.
Line Transformer Powering
Designing the Kinetic KTA1550 with Broadcom’s BCM54610 (voltage mode PHY) requires some minimal circuit
modifications in order to have the KTA1550 and BCM54610 voltage mode PHY compatible. The following
changes have been tested, and the combined circuit is Ethernet compliant.
The BCM54610 Ethernet transceiver is a voltage-mode device that provides its own common mode voltage to
the transformer, rather than an off chip supply as is usual in a current mode design. The common mode voltage
for the BCM54610 Ethernet transceiver in 10, 100, and 1000Base-T mode is nominally at 1.65V. The KTA1550
shall be connected in parallel to the Broadcom PHY, and the center-tap of the transformer shall source a voltage
close to 1.65V. This voltage to the center tap current shall be supplied from the PHY_VDD (2.5V) supply through
a 16Ω resistor (R1) to the center tap of the transformer (C12). The 16Ω resistor is calculated based on the
following equation:
R = [PHY_VDD -1.7V]/50mA
PHY_VDD = 2.5V
Two KTA1550 will draw 50mA current
1.7V Common Mode voltage of BCM54610
([2.5V – 1.70V]/50mA = 16Ω).
When using two KTA1550 in the case of a 1000Base_T application, both KTA1550 will draw 50mA combined;
therefore, using a 16Ω resistor will provide adequate current for the two KTA1550 devices.
It is also important to note that in order to meet return loss, 22Ω ferrite beads (22Ω@100khz, 500mA;
M18BA220SN1D) are added in series with the PHY to achieve the required return loss performance.
If the design uses a current-mode PHY, then the center tap voltage of the transformer can be set to PHY_VDD.
In this case, the resistor R1 should be set to 0Ω.
How to Design Kinetic Technologies KTA1550 for Use with Voltage-Mode PHY
AN095
Application Note
October 2017 – Revision 04a Page 2 Company Confidential
Design Schematics
Schematics and BOM are embedded here for reference only. For high quality images, please see separate PDF
and XLS files respectively.
Working Modes
Mode 1: Default Mode
Mode 1 is the default working mode. Under typical working condition, KTA1550 should give 13dB additional
common mode rejection @100MHz and the current will be 49mA.
Following settings are needed to work in mode 1:
HBW = floating
HGM = floating
EXRES = 8.06kΩ for 2.5V or 10.7kΩ for 3.3V power supply.
Table 1 lists the average test results from multiple units, including current from each supply. Total power
consumption, common mode rejection with KTA1550 and without KTA1550, and net decibel common mode
rejection KTA1550 brings into the system are included. The best operating condition to achieve 13dB common
mode rejection is marked in bolded blue in the table. It is achieved at VDD = 2.5V, and VCT = 1.8V, which has
the lowest power consumption under default mode, typical 88mW.
Table 1. Average Performance of KTA1550 Under Default Working Mode
HGM
HBW
VDD (V)
VCT (V)
IDD
(mA)
ICT
(mA)
Power
(mW)
CMMR
(off)
CMMR
(on)
KTA1550
CMMR
Z
Z
3.3
3.3
4.97
43.80
161.01
-43.99
-57.25
13.26
Z
Z
3.3
1.8
4.97
43.10
94.03
-43.99
-57.20
13.21
Z
Z
2.5
2.5
4.97
42.30
118.18
-43.97
-57.09
13.12
Z
Z
2.5
1.8
4.97
42.03
88.12
-43.98
-57.05
13.07
KTA1550
KTA1550
KTA1550 with BCM54610 Design
Designer: Kinetic
Date: September 2017
Kinetic
Technologies
Kinetic Technologies
6399 San Ignacio Ave., Suite 250
San Jose, CA 95119, USA
Tel: +1 (408) 746-9000
Fax: +1 (408) 351
-0338