Actel Fusion Mixed-Signal FPGAs
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VCCOSC
Oscillator Power Supply (3.3 V)
Power supply for both integrated RC oscillator and crystal oscillator circuit.
VCC
Core Supply Voltage
Supply voltage to the FPGA core, nominally 1.5 V. VCC is also required for powering the JTAG state
machine, in addition to VJTAG. Even when a Fusion device is in bypass mode in a JTAG chain of
interconnected devices, both VCC and VJTAG must remain powered to allow JTAG signals to pass
through the Fusion device.
VCCIBx
I/O Supply Voltage
Supply voltage to the bank's I/O output buffers and I/O logic. Bx is the I/O bank number. There are
either four (AFS090 and AFS250) or five (AFS600 and AFS1500) I/O banks on the Fusion devices plus
a dedicated VJTAG bank.
Each bank can have a separate VCCI connection. All I/Os in a bank will run off the same VCCIBx
supply. VCCI can be 1.5V, 1.8V, 2.5V, or 3.3V, nominal voltage. Unused I/O banks should have their
corresponding VCCI pins tied to GND.
VCCPLA/B
PLL Supply Voltage
Supply voltage to analog PLL, nominally 1.5 V, where A and B refer to the PLL. AFS090 and AFS250
each have a single PLL. The AFS600 and AFS1500 devices each have two PLLs. Actel recommends
tying VCCPLX to VCC and using proper filtering circuits to decouple VCC noise from PLL.
If unused, VCCPLA/B should be tied to GND.
VCOMPLA/B
Ground for West and East PLL
VCOMPLA is the ground of the west PLL (CCC location F) and VCOMPLB is the ground of the east PLL
(CCC location C).
VJTAG
JTAG Supply Voltage
Fusion devices have a separate bank for the dedicated JTAG pins. The JTAG pins can be run at any
voltage from 1.5 V to 3.3 V (nominal). Isolating the JTAG power supply in a separate I/O bank gives
greater flexibility in supply selection and simplifies power supply and PCB design. If the JTAG
interface is neither used nor planned to be used, the VJTAG pin together with the TRST pin could be
tied to GND. It should be noted that VCC is required to be powered for JTAG operation; VJTAG alone
is insufficient. If a Fusion device is in a JTAG chain of interconnected boards and it is desired to
power down the board containing the Fusion device, this may be done provided both VJTAG and
VCC to the Fusion part remain powered; otherwise, JTAG signals will not be able to transition the
Fusion device, even in bypass mode.
VPUMP
Programming Supply Voltage
Fusion devices support single-voltage ISP programming of the configuration flash and FlashROM.
For programming, VPUMP should be in the 3.3 V +/-5% range. During normal device operation,
VPUMP can be left floating or can be tied to any voltage between 0 V and 3.6 V.
When the VPUMP pin is tied to ground, it shuts off the charge pump circuitry, resulting in no sources
of oscillation from the charge pump circuitry.
For proper programming, 0.01 F and 0.33 F capacitors (both rated at 16 V) are to be connected in
parallel across VPUMP and GND, and positioned as close to the FPGA pins as possible.
User-Defined Supply Pins
VREF
I/O Voltage Reference
Reference voltage for I/O minibanks. Both AFS600 and AFS1500 (north bank only) support Actel Pro
I/O. These I/O banks support voltage reference standard I/O. The VREF pins are configured by the
user from regular I/Os, and any I/O in a bank, except JTAG I/Os, can be designated as the voltage
reference I/O. Only certain I/O standards require a voltage reference—HSTL (I) and (II), SSTL2 (I) and
(II), SSTL3 (I) and (II), and GTL/GTL+. One VREF pin can support the number of I/Os available in its
minibank.