Actel ProASIC3/E, User Manual, Page: 13 / 106

Power Supplies
ProASIC3/E Starter Kit User’s Guide and Tutorial 13
The board must be powered-up during programming because the chip needs its core voltages to be provided and VJTAG
must be detected by the FlashPro3 programmer in order for it to set its JTAG signal voltages to the right level.
The LCD has its own dedicated 5 V power supply, all components of which (including the regulator U20) are marked
on the circuit board in a boxed area so that you may know which components on the PCB are associated with which
tasks. An LED (D17) representing the 5 V supply availability is positioned at the top left of the board.
The ex9 V power supply is rated at 2 A maximum. On the first of the full-page dedicated schematics shown in
the appendix
“Board Schematics” on page 81 , it will be noted that the 3.3 V supply is rated at 5 A maximum. The
derived power supplies of 1.5 V, 1.8 V, and 2.5 V are rated at 2 A max each, and the LCD 5 V power supply is rated at
500 mA, as shown in
Figure B-11 on page 92 . Clearly, not all these derived supplies can be working at their respective
maximum current outputs simultaneously. The maximum ratings are for the individual regulator ICs and cannot be
numerically added together.
Both the U11 (LM2678S-3.3) and U20 (LM2674M-5.0) components are rated for an input voltage range of +8 V to
+40 V, so a wide range of power supplies may be used with the board with no concern about over-voltage conditions
occurring from inadvertent accidental usage of the wrong power supply. However, the user should take care to ensure
that the voltage provided is positive at the center pin of the J16 connector and grounded on the outside. Greater heating
of the regulator chips will be observed with higher voltages. It is therefore recommended that only the included power
supply or an equivalent substitute be used with the evaluation kit. The included power supply has been rated for this
board, including Actel daughter cards that may be attached to the board.
Daughter Card Power Supply Connections
Limited power to a daughter card may be supplied by the board. The connector for the daughter card is shown in
Figure B-7 on page 88 and is the J12 header. All the FPGA voltages of 1.5 V, 1.8 V, 2.5 V, and 3.3 V are provided to the
daughter card via a 12-pin 0.1 inch pitch connector. The voltages are arranged with a no-connection pin interspersing
the voltage pins. This prevents accidental use of a jumper to short a supply rail to ground, which could connect differing
supply rails together. The purpose is not to protect the power supply regulators, as these will go high-impedance when
an over-voltage condition is detected. It is to protect the FGPA from unintentional application of a higher voltage to the
1.5 V core. Three of the twelve pins are ground pins, which will provide more than sufficient current return capability for
future Actel daughter cards that will work with this board.
Power Supplies and Chaining Boards Together
There is a special note on “V
PUMP
Connections When Chaining Boards Together” on page 14 .
Instructions are detailed here but the novice reader is advised to return to this section after reading the section on
standard JTAG programming connections via FlashPro3.
When joining multiple ProASIC3 starter kit boards together via the chain programming connection, bear in mind that
the J2 connector is used to connect to the J1 connector of the next board in the chain by attaching a standard 0.100-inch
pitch 10-pin programming cable. The length of the cable does need to be kept as short as possible, because multiple
boards connected to form a JTAG chain of ProASIC3/E devices will provide much greater noise pick-up and may
degrade the TCK clock for devices remote from the FlashPro3 programmer. Set VJTAG at an absolute minimum of 1.8
V to help with signal integrity when chaining boards together. Higher voltages will give better noise and impedance
mismatch immunity.
Disconnect the jumper at JP10 on all boards. This jumper can be used to provide VJTAG to a downstream board or to
some element in the design that you wish to supply with the VJTAG voltage used by the ProASIC3/E component. The
shunt that is normally in this location can be safely stored across pins 11 and 12, or 9 and 10 of the J12 daughter card
power supply connector. For particularly long chains, the value of TCK used during programming should be reduced.
During its development, various revisions of the ProASIC3 Starter Kit board have been produced. This documentation
contains additional text that documents some of these earlier versions, as well as the newest Rev3 version of the board.
Schematics for Rev3 and Rev2 boards are the same when viewed as PDF files, but there is a short in the board layers on
the Rev2 that has been corrected for Rev3. The rare Rev1 prototype boards had different schematics and are not
discussed in this document.