Fuses, Batteries, Regulators, And Fans; On-Board Current Monitoring And Variable Voltage Testing; Supplies; Table 7-1. Current Measurement Of The1.4V Supplies - IBM PPC750FX User Manual

Preliminary

7. Fuses, Batteries, Regulators, and Fans

This evaluation board is a PCI card and contains no fuses, batteries, or user-adjustable regulators. All supply
voltages needed for the various board components are developed by fixed, board-mounted regulators that
use the voltage provided through the PCI edge connector or the ATX power connector. There are three on-
board voltages that can be monitored for current drain or replaced with external voltage sources for variable
voltage testing.
There is one fan installed on the board that cools the two processor chips.

7.1 On-Board Current Monitoring and Variable Voltage Testing

The PPC750FX logic, PLL, and 60X bus voltages can be monitored for current drain. In addition, external
supplies can be connected in place of the fixed, on-board regulators to perform variable voltage testing.
Removal of zero-ohm resistors, as shown in Figure 7-1, is required to implement current measurement or
supply substitution.

Figure 7-1. Resistor Location Diagram

7.1.1 1.45V Supplies
The PPC750FX uses +1.45 V for the logic and PLL voltages. There are two +1.45V supplies on the board.
They are identified as VCCA1 and VCCA2. A pair of zero-ohm resistors can be removed for either of both
supplies to create a connection point or points for current measurement or external supply connection.
Figure 7-1 shows the location of the zero-ohm resistors. Current measurements can be made between
terminals 1 and 2 of either resistor. External supplies should be connected to terminal 2.

Table 7-1. Current Measurement of the1.4V Supplies

Voltage
VCCA1
750FXebm_ch7.fm
June 10, 2003
Remove resistors at:
R267 and R271
Fuses, Batteries, Regulators, and Fans
Evaluation Board Manual
PPC750FX Evaluation Board
R224
2 1
R226
R267
2 1
R271
R307
2 1
R312
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