Specifications

E PENTIUM® PRO PROCESSOR AT 150, 166, 180, and 200 MHz
13
nS
Vss Current
Vcc Current
Averaged Vcc Current
Load-Change
Transient
Switching
Transient
Switching
Transient
Figure 8. Transient Types
Bulk capacitance with a low Effective Series
Resistance (ESR) should also be placed near the
Pentium Pro processor in order to handle changes in
average current between the low-power and normal
operating states. About 4000uF of capacitance with
an ESR of 5mΩ makes a good starting point for
simulations, although more capacitance may be
needed to bring the ESR down to this level due to the
current technology in the industry. The standard
Pentium Pro Voltage Regulator Modules already
contain this bulk capacitance. Be sure to determine
what is available on the market before choosing
parameters for the models. Also, include power
supply response time and cable inductance in a full
simulation.
See
AP-523 Pentium
®
Pro Process or Power
Distribution Guidelines
Application Note (Order
Number 242764) for power modeling for the Pentium
Pro processor.
3.4.1. V
CC
S DECOUPLING
Decoupling of ten (10) 1µF ceramic capacitors (type
Y5S or better) and a minimum of five 22µF tantalum
capacitors is recommended for the V
CC
S pins. This
is to handle the transients that will occur in future
devices.
3.4.2. GTL+ DECOUPLING
Although the Pentium Pro GTL+ processor bus
receives power external to the Pentium Pro
processor, it should be noted that this power supply
will also require the same diligent decoupling
methodologies as the processor. Notice that the
existence of external power entering through the I/O
buffers causes V
SS
current to be higher than the V
CC
current as evidenced in Figure 8.