Power Modes - NXP Semiconductors PN7462 series User Manual

NXP Semiconductors

8.3 Power modes

The PN7462 family offers four different power modes allowing customer to optimize its
energy consumption. These are:
• Active mode
• Standby mode
• USB suspend mode
• Hard Power Down mode
8.3.1 Full Power Mode (Active Mode)
In the active mode, all functionalities are available and all blocks are accessible. The
PN7462 family is powered from the VBUS supply.
8.3.2 Standby Mode
In this mode, only small part of the IC is powered to maintain operation of the Power
Control Unit, the LFO and a small set of registers for storing data during the standby
operation. The MLDO is set to the low power mode. The possible wake-up sources are
still powered. Depending on the application requirements, it is possible to put
PVDDL_LDO into active mode, low power mode (default) or shut down mode.
The standby mode is triggered by the application firmware. Before entering the standby
mode, the PN7462 family executes automatically the deactivation of the contact card.
An internal mechanism prevents from entering into the standby mode either when no
relevant wake up source is activated, or when conditions for a corresponding wakeup
source are not present. The IC goes to power on mode again when a wake up is
asserted.
8.3.2.1 Entering Standby Mode
To enter standby mode, the firmware needs to operate in an infinite while loop of:
1. Programming the standby bit in the PCR_CTRL_REG.
2. Checking if there is any standby prevention reason.
3. If any reason found, then cater to the reason preventing entry of standby
This loop will be automatically broken when PN7462 family enters standby and comes
out. As this will reset PN7462 family and restart the boot.
8.3.2.2 Standby prevention root causes
Table below summarizes conditions preventing PN7462 family from entering the standby
mode.
Table 68. Standby prevention root causes
No.
1
2
UM10858
User manual
COMPANY PUBLIC
Go back to step 1.
Root cause description
A host communication is ongoing
If wake-up timer is enabled and its value is 0
All information provided in this document is subject to legal disclaimers.
Rev. 1.4 — 14 May 2018
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UM10858
PN7462 family HW user manual
© NXP B.V. 2018. All rights reserved.
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