Intel 1.00 GHz BX80530F1000256 Data Sheet

57

There are three signal quality parameters defined for non-AGTL+ signals: overshoot/undershoot, 
ringback, and settling limit. All three signal quality parameters are shown in 

 for the non-

AGTL+ signal group.

1. For the FC-PGA/FC-PGA2 packages, V

HI 

= 1.5 V for all non-AGTL+ signals except for BCLK, PICCLK, and 

PWRGOOD. V

HI 

= 2.5 V for BCLK, PICCLK, and PWRGOOD. BCLK and PICCLK signal quality is detailed in 

.

Overshoot (or undershoot) is the absolute value of the maximum voltage above the nominal high 
voltage or below V

SS

. The overshoot/undershoot guideline limits transitions beyond V

CC

 or V

SS

 

due to the fast signal edge rates. (See 

 for non-AGTL+ signals.) The processor can be 

damaged by repeated overshoot events on the voltage tolerant buffers if the charge is large enough 
(i.e., if the overshoot is great enough). The PPGA and S.E.P. packages have 2.5 V tolerant buffers 
and the FC-PGA/FC-PGA2 packages has 1.5 V or 2.5 V tolerant buffers.

However, excessive ringback is the dominant detrimental system timing effect resulting from 
overshoot/undershoot (i.e., violating the overshoot/undershoot guideline will make satisfying the 
ringback specification difficult). The overshoot/undershoot guideline is 0.7 V for the PPGA 
and S.E.P. packages and 0.3 V for the FC-PGA/FC-PGA2 packages and assumes the absence 
of diodes on the input. These guidelines should be verified in simulations without the on-chip 
ESD protection diodes present because the diodes will begin clamping the signals (2.5 V tolerant 
signals for the S.E.P. and PPGA packages, and 2.5 V or 1.5 V tolerant signals for the FC-PGA/
FC-PGA2 packages) beginning at approximately 0.7 V above the appropriate supply and 0.7 V 
below V

SS

. If signals are not reaching the clamping voltage, this will not be an issue. A system 

should not rely on the diodes for overshoot/undershoot protection as this will negatively affect the 
life of the components and make meeting the ringback specification very difficult.

Undershoot

Overshoot

Settling Limit

Settling Limit

Rising-Edge
Ringback

Falling-Edge
Ringback

V

LO

V

SS

V

HI