EM357-RTR datasheet(37/241 Pages) SILABS

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Rev 1.3

6.2. Resets

The EM35x resets are generated from a number of sources. Each of these reset sources feeds into central reset

detection logic that causes various parts of the system to be reset depending on the state of the system and the

nature of the reset event.

6.2.1. Reset Sources

6.2.1.1. Power-On-Resets (POR HV and POR LV)

The EM35x measures the voltage levels supplied to the three power domains. If a supply voltage drops below a

low threshold, then a reset is applied. The reset is released if the supply voltage rises above a high threshold.

There are three detection circuits for power-on-reset as follows:



POR HV monitors the always-on domain supply voltage. Thresholds are given in Table 6.1.



POR LV core monitors the core domain supply voltage. Thresholds are given in Table 6.2.



POR LV mem monitors the memory supply voltage. Thresholds are given in Table 6.3.

The POR LVcore and POR LVmem reset sources are merged to provide a single reset source, POR LV, to the

Reset Generation module, since the detection of either event needs to reset the same system modules.

Table 6.1. POR HV Thresholds

Parameter

Test conditions

Min

Typ

Max

Unit

Always-on domain release

0.62

0.95

1.20

Always-on domain assert

0.45

0.65

0.85

Supply rise time

From 0.5 V to 1.7 V

250

µs

Table 6.2. POR LVcore Thresholds

Parameter

Test conditions

Min

Typ

Max

Unit

1.25 V domain release

0.9

1.0

1.1

1.25 V domain assert

0.8

0.9

1.0

Table 6.3. POR LVmem Thresholds

Parameter

Test conditions

Min

Typ

Max

Unit

1.8 V domain release

1.35

1.5

1.65

1.8 V domain assert

1.26

1.4

1.54

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