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Revision 2.3

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AS8525

Datasheet - Application In form atio n

Note:

L = low state, H = high state, OT = Over-temperature Reset, Uvcc = Under-voltage VCC, Uvbat = Under-voltage VBAT, rwake

=remote wake, X = don’t care.

8.3 Initialization

When the power supply is switched on, when VSUP > VSUVR_OFF, RESET_VSUP_N becomes high. This starts the regulator LDO with 3.3V

and Vuvr_off option of 2.75V. When VCC > Vuvr_off (2.75V), active-low PORN_2_OTP is generated and the regulator ALDO is turned on with

loads contents of OTP latch onto a register. This register provides the actual settings of LDO (and ALDO), Vuvr_off and Reset Timeout period

slow ramp rates on VSUP (of the order of 0.5V/min).

Figure 9. Initialization Sequence for AS8525

Table 17. VSUP>Vsuvr_on and VCC<Vuvr_on

Block

Output Signal

TRANSCEIVER=Enabled (disabled only during initial VSUP ramp-up)

LIN=high-z, RX=follows VCC…

LDO=Enabled (disabled only during initial ramp-up)

VCC=low…

RELAY DRIVER=Enabled

LDRIVE1=high… LDRIVE2=high…

RESET BLOCK=Enabled

RESET=high-z…

RESISTIVE DIVIDER=Enabled

VBAT=high…, VBAT_DIV=enabled

LDO Off

LDO On

VCC Por Threshold = 2.75V

LDO setting = 3.3V

Reset Timeout = 4msec

LDO On

VCC Por Threshold = from OTP Block

LDO setting = from OTP Block

Reset Timeout = from OTP Block

VCC

VSUP

Device

Settings

RESET_VCC_N

RESET_VSUP_N

PORN_2_OTP

LOAD_OTP_IN_

PREREG

RESET

VCC_POR_Threshold

VSUP_POR_Threshold

6 Cycles of

RC-Oscillator

PHASE 1

PHASE 2

If Phase 1 POR threshold == Phase 2 POR threshold

Tres = Reset Timeout from OTP Block

If Phase 1 POR threshold != Phase 2

POR threshold

Tres = Reset Timeout from OTP Block

LDO settings to 5 V

LDO settings to 3.3 V

LDO settings to 5 V

LDO settings to 3.3 V

AVCC