Teledyne LeCroy CPCI64 - Manual (Page 5)

5
POWER-ON RESET
Each time the Active Extender board is turned Off and then On, a reset signal will be generated from the
extender to the Unit-Under-Test automatically. The duration of this reset is 200 milliseconds. The reset to
the Unit-Under-Test is also activated every time there is a reset from the bus.
CURRENT MEASUREMENT
To measure the current being drawn by the Unit-Under-Test, just connect a voltmeter to J3. Every Volt
read by the meter represents One Amp, so a voltmeter reading of 0.35 indicates that the Unit-Under-Test is
drawing 350 milliamperes of current. J3 terminals are marked for Ground, +5I, +3.3I and +12I.
NOTE: If the VIO and +5V are on the same plane on your board, you need to remove the JP10
jumper from the extender board, in order to get an accurate current measurement for the
+5V.
CURRENT LIMIT CIRCUITRY
Red LEDs, when illuminated, indicate a short or a very low voltage. Green LEDs when illuminated,
indicate voltages at their designated outputs. In the case of the short for the +5V, +12V and +3.3V from
the Unit-Under-Test, the Active Extender will automatically switch the current limit down to about 200
milliampere and will continue to deliver this current for troubleshooting purposes. In the case of shorts or
excessive current draw for the other voltages, resetable fuses will open up until the problem is corrected.
The current limit value for the +5V is set to 5 Amps with JP8 (JP2 for CPCI) not installed and 1 Amp with
JP8 (JP2 for CPCI) installed.
CURRENT LIMIT ADJUSTMENT
FOR PCIAX532/PCIAX332
To increase the +5V current limit you must remove the resistor at R23 and perform the following
reworks:
• To change the current limit to 8A install a 10k resistor at location R22 and a 6.2k resistor at
location R23. This does not affect the current measurement reading.
• To change the current limit to 10A, install a 10k resistor at location R22 and R23. This does not
affect the current measurement reading.
To increase the +3.3V current limit, you must supply +3.3V current from the motherboard or an
external power supply and reduce the gain of the current measurement circuitry. To do so, perform the
following rework:
• To change the current limit to 8A install a 4.7k Resistor on top of R57. This does not affect the
current measurement reading.