AN4092

Power Management Controller (PMC)

Doc ID 023080 Rev 2

17/38

The standby switch breaks before make, and hence is not shorted Vdd to Vstby during the

transition.

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When the switch sources Vdd_array from Vstby, and Vdd ramps high, the switch

transitions to sourcing Vdd anywhere while 0 < Vdd - Vstby < 0.050V is valid

●

When the switch sources Vdd_array from Vdd, the switch is designed to transition to

Vstby when Vstby > Vdd

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The switch works with all ramp rates of Vdd

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The circuit is not drew excessive leakage current if Vdd remains at a mid-level

If VSTBY is not used, it must be connected to ground. When VSTBY is grounded, the switch

is always connected to VDD.

1.6.2

Standby Regulator

The purpose of the regulator is for when VSTBY is in the range of 2V-5.5V. The regulated

output is 1V. When the standby voltage is in the range of 0.95V-1.2V, the regulator is

bypassed and the RAM sees the raw, unregulated standby voltage.

1.6.3

The brown-out detector monitors the standby voltage and sets the BRW flag on the PMC

Configuration and Status Register when the voltage on the VSTBY pin falls to 600 mV. After

reset, this flag comes up asserted and then it can be cleared by software by writing 1 to it.

When the voltage on the VSTBY pin is 0, the brownout detector flag is also 0, regardless of

the voltage on VDD.

1.7

Power dissipation

The total power dissipation depends on the current required on the different supplies. It also

depends on the power configuration. In the single 5V supply configuration, the contributors

are:

1.

VDD * IDD

2.

VDDA * IDDA

3.

VDDREG * IDDREG

4.

VDDEHx * IDDEHx

If the internal 3.3V voltage regulator is switched off the contributors are:

1.

VDD * IDD

2.

VDDA * IDDA

3.

4.

VRC33 * IDD33

5.

VDDEHx * IDDEHx

i.

Please refer to device errata sheet to check whether or not this feature is available.

j.

If the internal 3.3V is switched off but VDDREG is not grounded, there is still a small current consumption due

to the LVI circuitry and the 1.2V regulator.