900844 datasheet(84/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

POWER SUPPLIES

POWER SUPPLIES FAULT MANAGEMENT

This section discusses faults related to, or caused by power supplies (directly or indirectly) operating outside their specified

boundaries.

Reference Interrupt Controller for more information on the various interrupt signals, and the interrupt mechanism used to

communicate to the system controller.

THERMAL MANAGEMENT

The thermal protection is based on a circuit with a voltage output that is proportional to the absolute temperature. This voltage

can be read out via the ADC for precise temperature readouts. See ADC Subsystem.

This voltage is monitored by an integrated comparator. Interrupt THRM will be generated, if not masked, when crossing the

thermal warning threshold TWARN, and sets the VRFAULT 1st level interrupt that causes the PMICINT pin to assert, notifying

the system controller of a system event.

In addition to the previous, the 900844 includes integrated thermal protection that shuts down and powers off the system, in

cases of over dissipation, if the junction temperature exceeds the TSHUTDOWN threshold. This thermal protection will act above

the maximum junction temperature, to avoid any unwanted power downs. The protection is de-bounced by one period of the

32 kHz clock in order to suppress any (thermal) noise. This protection should be considered as a fail-safe mechanism. Therefore,

the application design should execute a thermal shutdown under normal conditions.

Once the thermal event is cleared and the temperature is back to its normal range, the 900844 restarts automatically, by

following the steps outlined in Initial Power Up Sequence

VDDQTONT

5:4

Turn On Time Settings for VDDQ Regulator

x0 = 240 μs

x1 = 120 μs

x2 = 60 μs

x3 = 30 μs

RSVD

7:6

RSVD

FSLTONTCNTL2 (ADDR 0x1CB - R/W - Default Value: 0xAA)

V21TONT

1:0

Turn On Time Settings for V21 Regulator

x0 = 320 μs

x1 = 160 μs

x2 = 80 μs

x3 = 40 μs

V15TONT

3:2

Turn On Time Settings for V15 Regulator

x0 = 200 μs

x1 = 100 μs

x2 = 50 μs

x3 = 25 μs

Reserved

7:4

Reserved

Table 49. Thermal Warning/Shutdown Thresholds

Parameter

Min

Typ

Max

Unit

Thermal Warning Threshold

115

120

125

°C

Thermal Warning Hysteresis

°C

Thermal Shutdown Threshold

130

140

150

°C

Table 48. Ramp Rate Control Registers (Freescale Defined)

Name

Bits

Description

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