Power
NVIDIA Jetson Xavier NX DG-09693-001_v1.7 | 13
SHUTDOWN_REQ*
SHUTDOWN_REQ* is driven active (low) by the module if the system must be shut down, due
to a software shutdown request, over-temperature event, undervoltage event, or other
faults. The power control logic on the carrier board must drive
POWER_EN inactive (low) if
SHUTDOWN_REQ* is asserted.
SHUTDOWN_REQ* is not driven during power-on. It is pulled up to the 5V supply, so stays
inactive. If the system is on and reset is driven low, the PMIC will initiate a full power cycle
and start the power-on sequence. Again,
SHUTDOWN_REQ* is not asserted. SHUTDOWN_REQ*
will only go low when the module determines the system needs to shut down.
SHUTDOWN_REQ* comes from a latch on module and is cleared when POWER_EN goes low.
If
SHUTDOWN_REQ* is asserted, the carrier board must de-assert POWER_EN as soon as
possible. One reason for this is to give the system enough time to do a correct power down
sequence in the case of a sudden power loss case. In this case, once the 5V supply drops
to ~4.2 V, the on-module
VIN_PWR_BAD_N signal is asserted which results in SHUTDOWN_REQ*
being asserted. The PMIC then starts the power down sequence which takes ~4 to 5 ms.
The sequence must finish before the input voltage drops below 3.0 V to correctly power off
the module.
Power Rail Discharge
To satisfy the power down sequencing requirement and prevent unwanted back drive from the
carrier board to the module, the following must be true:
The carrier board 3.3V power supply that powers any module I/O must be off within 1.5 ms
of
SYS_RESET* assertion.
The 1.8V power supply that powers any module I/O must be off within 4 ms.
The power rails should be fully discharged before attempting to power back up.
Figure 5-1. System Power and Control Block Diagram
Carrier Board
Main 5V
Power
Source
Sup plies
Jetson
Power
Logic
POWER_EN
251
↓
260
237
233
SHUTDOWN_REQ*
239
SYS_RESET*
VDD_IN
EN
Note: Designs which implement an eFUSE or current limiting device on the input power rail of
the module should select a part that DOES NOT limit reverse current.
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