EM357-RTR datasheet(38/240 Pages) ETC2

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EM351 / EM357

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 LVcore monitors the core domain supply voltage. Thresholds are given in Table 6-2

POR LVmem monitors the memory supply voltage. Thresholds are given in Table 6-3.

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

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.

6.2.1.2

nRESET Pin

A single active low pin, nRESET, is provided to reset the system. This pin has a Schmitt triggered input.

To afford good noise immunity and resistance to switch bounce, the pin is filtered with the Reset Filter

module and generates the reset source RSTB to the Reset Generation module. Table 6-4 contains the

specification for the filter.

Table 6-4. Reset Filter Specification for RSTB

Parameter

Min

Typ

Max

Unit

Reset filter time constant

2.1

12.0

16.0

µs

Reset pulse width to guarantee a reset

26.0

µs

Reset pulse width guaranteed not to cause a reset

1.0

µs

6-3

120-035X-000D

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