Справочник Пользователя для Intel 315889-002

315889-002

53

An electronic load that has the capability to change the repetition rate up to 3 MHz of 
the load step is needed. The Intel LGA771/775V2 VTT by Cascade Systems Design, will 
meet this requirement. By monitoring the VTT current and voltage waveforms with an 
oscilloscope capable of executing an FFT on these waveforms, the platform impedance 
is found. A complete impedance profile is then generated by sweeping the input 
waveform frequency across the range of interest. In order to automate the data 
collection process, Intel has modified the VTT control software and a GPIB controlled 
oscilloscope is used along with software supplied with the VTT.

These utilities allow the user to automatically display and collect the magnitude and 
phase of the motherboard impedance in a Microsoft Excel* compatible data file. The 
total time it takes to extract the impedance profile using this method is about 1-2 
minutes. This technique is very useful in investigating and assuring MB performance 
based on its stack up.

For more information on the measurement method and theory, see the paper 
Microprocessor Platform Impedance Characterization using VTT Tools by K. Aygun, S. 
Chickamenahalli, K. Eilert, M. Hill, K. Radhakrishnan and E. Stanford published at the 
IEEE Applied Power Electronics Conference, 2005.

As an example, 

 shows the test platform with 10 560 

μ

F Al-Poly bulk 

capacitors and 10 10 

μ

F and 8 22

μ

F high frequency MLCC capacitors in the socket 

cavity. 

 

as capacitors are removed. The VID setting for this measurement was 1.35 V and load