AS8221-ASSP datasheet(16/42 Pages) AMSCO

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AS8221

Datasheet - Detailed Descr i p ti on

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Revision 1.7

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8.5 Undervoltage Events

The device monitors the following three voltage supplies:



VBAT: Battery supply voltage



VIO: Supply voltage for I/O digital level adaptation



VCC: Supply voltage (+5V)

8.5.1 Undervoltage/Voltage Recovery VBAT

If VBAT voltage falls below VBATTHL for a time longer than tUV_DETECT then the undervoltage VBAT flag is set and it is reset if VBAT exceeds the

voltage threshold VBATTHH for a time longer than tUV_REC or in case a wake-up event has been detected. The flag can be set or reset in all the

modes.

8.5.2 Undervoltage/Voltage Recovery VIO

If VIO voltage falls below VIOTHL for a time longer than tUV_DETECT then the undervoltage VIO flag is set and it is reset if VIO exceeds the voltage

threshold VIOTHH for a time longer than tUV_REC or in case a wake-up event has been detected. The flag can be set or reset in all the operation

modes. The flag is automatically reset at POWER-OFF.

8.5.3 Undervoltage/Voltage Recovery VCC

If VCC voltage falls below VCCTHL for a time longer than tUV_DETECT then the undervoltage VCC flag is set and it is reset if VCC exceeds the

voltage threshold VCCTHH for a time longer than tUV_REC or in case a wake-up event has been detected. The flag can be set or reset in all

operation modes. The flag is automatically reset at POWER-OFF.

8.6 Power On/Off Events



Starting from POWER-OFF mode a power on event occurs in case VBAT undervoltage flag is reset.



Starting from every operation mode a POWER-OFF event occurs in case VBAT and VCC undervoltage flags are set.

8.7 Wake-Up Events

A wake-up event can be detected only in low-power modes. The wake-up flag is set if the remote or local wake flag is set. The wake-up flag is

reset if both the remote and local wake-up flags are reset. The remote wake-up flag is set if a remote wake-up event occurs. The local wake-up

flag is set if a local wake-up event occurs. The remote and local wake-up flags are reset entering a low-power mode from a non-low-power mode,

entering NORMAL mode, whenever an undervoltage event occurs and at POWER-OFF.

8.7.1 Remote Wake-Up Event

A remote wake-up event, only possible in low-power mode, consists in the reception of at least two consecutive wake-up symbols via the bus

within tBWU_Detect. The wake-up symbol is defined as Data0 longer than tBWU_D0 followed by idle or Data1 longer than tBWU_Idle as in Figure 7

unless an undervoltage or wake-up event is present.

Figure 7. Signal for Wake-up Pattern Recognition

tBWU_D0

tBWU_Idle

VBUS

tBWU_D0

tBWU_Idle

tBWU_Detect

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