ProASIC3 Flash Family FPGAs
Table 2-4 • Overshoot and Undershoot Limits 1
VCCI and VMV
Average VCCI–GND Overshoot or Undershoot
Duration as a Percentage of Clock Cycle2
2.7 V or less
1. Based on reliability requirements at 85°C.
2. The duration is allowed at one out of six clock cycles. If the overshoot/undershoot occurs at one out of two cycles, the
maximum overshoot/undershoot has to be reduced by 0.15 V.
3. This table does not provide PCI overshoot/undershoot limits.
I/O Power-Up and Supply Voltage Thresholds for Power-On Reset
(Commercial and Industrial)
Sophisticated power-up management circuitry is designed into every ProASIC®3 device. These circuits
ensure easy transition from the powered-off state to the powered-up state of the device. The many
different supplies can power up in any sequence with minimized current spikes or surges. In addition, the
I/O will be in a known state through the power-up sequence. The basic principle is shown in Figure 2-1
on page 2-4.
There are five regions to consider during power-up.
ProASIC3 I/Os are activated only if ALL of the following three conditions are met:
1. VCC and VCCI are above the minimum specified trip points (Figure 2-1 on page 2-4).
2. VCCI > VCC – 0.75 V (typical)
3. Chip is in the operating mode.
VCCI Trip Point:
Ramping up: 0.6 V < trip_point_up < 1.2 V
Ramping down: 0.5 V < trip_point_down < 1.1 V
VCC Trip Point:
Ramping up: 0.6 V < trip_point_up < 1.1 V
Ramping down: 0.5 V < trip_point_down < 1 V
VCC and VCCI ramp-up trip points are about 100 mV higher than ramp-down trip points. This specifically
built-in hysteresis prevents undesirable power-up oscillations and current surges. Note the following:
• During programming, I/Os become tristated and weakly pulled up to VCCI.
• JTAG supply, PLL power supplies, and charge pump VPUMP supply have no influence on I/O
PLL Behavior at Brownout Condition
Microsemi recommends using monotonic power supplies or voltage regulators to ensure proper power-
up behavior. Power ramp-up should be monotonic at least until VCC and VCCPLLX exceed brownout
activation levels. The VCC activation level is specified as 1.1 V worst-case (see Figure 2-1 on page 2-4
for more details).
When PLL power supply voltage and/or VCC levels drop below the VCC brownout levels (0.75 V ± 0.25
V), the PLL output lock signal goes low and/or the output clock is lost. Refer to the "Power-Up/-Down
Behavior of Low Power Flash Devices" chapter of the ProASIC3 FPGA Fabric User’s Guide for
information on clock and lock recovery.