Board Design Guidelines for SmartFusion2 SoC and IGLOO2 FPGAs
AC393 Application Note Revision 14.0 9
2.2.2 Power Supply Sequencing
The SmartFusion2/IGLOO2 system controller performs systematic power-on reset (POR) whenever the
device is powered on or reset. All the I/Os are held in a high-impedance state by the system controller
until all power supplies are at their required levels and the system controller has completed the reset
sequence.
VDD refers to the supply voltage to the SmartFusion2/IGLOO2 device core and VDDI refers to the supply
voltage to the bank I/O buffers and I/O logic.
On detection of a power-up event, the POR circuit sends the power-on reset signal to the system
controller and reset controller in the SmartFusion2/IGLOO2 device. The power-on reset circuitry in
SmartFusion2/IGLOO2 devices require the VDD and VPP supplies to ramp monotonically from 0 V to the
minimum recommended operating voltage within a predefined time. There is no sequencing requirement
on VDD and VPP. Four ramp rate options are available during design generation: 50 µs, 1 ms, 10 ms,
and 100 ms. Each selection represents the maximum ramp rate to apply to VDD and VPP. The ramp
rates can be configured by using the Libero software.
The SERDES_VDD pins are shorted to VDD on silicon die; therefore, Microsemi recommends using the
same regulator to power up the VDD, SERDES_VDD and SERDES_VDDAIO pins. These three voltage
supplies must be powered at the same voltage and must be ramped up and ramped down at the same
time.
For information about the power-up to functional time sequence, see DS0128: IGLOO2 and
SmartFusion2 Datasheet.
2.3 I/O Glitch
Glitches were observed in SmartFusion2 and IGOOL2 devices during power-up and power-down cases
in different scenarios. The following sections describe the glitch observations.
2.3.1 I/O Glitch During Power-Up
Table 4, page 10 lists the I/O glitch observations during power-up found during internal testing.
T491B476M010AT KEMET Tantalum 47 µF, 10 V, 20%SMD
T520V107M010ATE050 KEMET Tantalum 100 µF, 10 V, 20%, 2917
TPSD337K010R0050 AVX Tantalum 330 µF, 10 V, 10%, 2917
Table 3 • Recommended Capacitors (continued)
Part Number Manufacturer Description
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