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Offchip Driver with self adjust damper resistor and Receiver with terminator which has power save mode using MTJ

IP.com Disclosure Number: IPCOM000016043D
Original Publication Date: 2002-Nov-30
Included in the Prior Art Database: 2003-Jun-21
Document File: 4 page(s) / 84K

Publishing Venue

IBM

Abstract

Offchip Driver with self adjust damper resistor

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  Offchip Driver with self adjust damper resistor and Receiver with terminator which has power save mode using MTJ

Offchip Driver with self adjust damper resistor

Impedance matching is the essential technique for the high quality signal transfer via the line on the print circuit boards or the cables. In the typical driver circuit (Fig-1), small resistor (22ohm or 33ohm) will be implemented serially to the offchip drivers to keep the line impedance matching between driver and signal line, but this damper resistor is not ideal solution for the impedance matching. Ideally impedance of the Driver (Zs) plus impedance of the Damper (Zd) should be equal to signal line impedance on the print circuit board (Zo). Unfortunately, ideal impedance matching could not be implemented in the actual products based on the CMOS technology because Zd and Zo are the static parameters but Zs is not static fixed but dynamic parameter which will be defined by following parameters: manufacturing process, Operating Voltage, and Operating Temperature. So Zd should be complemental dynamic parameter to Zs for ideal impedance matching.

Zs

verDriZo

Zd

(Fig-1)

Following is a method to implement this Zd adjustable capability by using MTJ. The driver circuit is composed of 3 functions: (Fig-2)

1. MTJ Resistor as the damper
2. Write circuit to the MTJ
3. CMOS chip speed self detect circuit

First step is the chip speed detection, this will be done by measure the delay value of the delay line in the chip and measurement operation will be triggered by the POR (Power-On Reset). Next step is the write operation to the MTJs. Damper resistor will be composed of several MTJ connected in parallel, write value to the MTJs should be predefined. Resistance of MTJ will be 2 different values under the condition that the magnetic direction in the free layer is in the same direction as the pinned layer or not...