U1AFS250-FG256 Datasheet, PDF (6/27 Pages) Actel Corporation – 3 - DC and Power Characteristics

DC and Power Characteristics
PLL Behavior at Brownout Condition
Actel recommends using monotonic power supplies or voltage regulators to ensure proper power-
up behavior. Power ramp-up should be monotonic at least until V_CC and V_CCPLX exceed brownout
activation levels. The V_CC activation level is specified as 1.1 V worst-case (see Figure 3-1 on page 3-6
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 of Fusion FPGAs application note for information on clock and lock recovery.
V_CC
V_CC = 1.575 V
V_CC = 1.425 V
Activation trip point:
Va = 0.85 V ± 0.25 V
Deactivation trip point:
Vd = 0.75 V ± 0.25 V
V_CC = V_CCI + VT
Where VT can be from 0.58 V to 0.9 V (typically 0.75 V)
Region 1: I/O Buffers are OFF
Region 4: I/O
buffers are ON.
I/Os are functional
(except differential inputs)
but slower because V_CCI is
below specification. For the
same reason, input buffers do not
meet V_IH/V_IL levels, and output
buffers do not meet V_OH/V_OL levels.
Region 5: I/O buffers are ON
and power supplies are within
specification.
I/Os meet the entire datasheet
and timer specifications for
speed, VIH/VIL , VOH /VOL , etc.
Region 2: I/O buffers are ON.
I/Os are functional (except differential inputs)
but slower because V_CCI/V_CC are below
specification. For the same reason, input
buffers do not meet V_IH/V_IL levels, and
output buffers do not meet V_OH/V_OL levels.
Region 3: I/O buffers are ON.
I/Os are functional; I/O DC
specifications are met,
but I/Os are slower because
the VCC is below specification
Region 1: I/O buffers are OFF
Activation trip point:
Va = 0.9 V ±0.3 V
Deactivation trip point:
Vd = 0.8 V ± 0.3 V
Min V_CCI datasheet specification
voltage at a selected I/O
standard; i.e., 1.425 V or 1.7 V
or 2.3 V or 3.0 V
Figure 3-1 • I/O State as a Function of V_CCI and V_CC Voltage Levels
VCCI
3-6
Preliminary v0.4