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22 Sept 2016
v1.1
3.7 Sequencing
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PWR_EN signal, active high, JX1.5, allows the carrier to turn on or off the PicoZed
power supplies. R18 and C6 have been placed to adjust the timing of this signal during
power off conditions. This signal should not be de-asserted until VCCIO_EN is de-
asserted. In the carrier off condition (power plug removed or power switch turned off),
this signal is driven low.
•
VCCIO_EN signal, active high, JX2.10, originates on the SOM and is the output of the
1.8V regulator, PG_1V8. This signal enables the carrier’s 3.3V supply, which in turn
enables the VADJ regulator. When the carrier is turned off (power switch turned off or
power plug removed) or the PicoZed’s PG_1V8 signal is de-asserted VCCI_EN is
driven low, which turns off the FMC-CC supplies. 5V will continue to be supplied
unless the power switch SW7 is set to OFF.
•
PG_CARRIER signal, active high, JX2.11, is pulled up by PicoZed’s +3.3V
PG_MODULE signal. This signal can be pulled low by the carrier board (SW4), the
FMC board or the PicoZed when the board’s power circuitry is not ‘Good’ yet.
•
The following diagram illustrates the power supply sequencing on power up. Note Vin
and PWR_Enable can come up simultaneously, but shown staggered as PWR_Enable
can come up later.
Vin
PWR_EN
VCCIO_EN
PG_CARRIER
Figure 23 – Power Sequencing
The PG_CARRIER (on PZCC-FMC-V2) and PG_MODULE (on PicoZed) signals are
wired OR and tied to the Zynq Power On Reset signal. When the power supplies are
valid on both the SOM and carrier, the PG signal de-asserts the Zynq POR signal.
