COP8CCR9IMT7SLASHNOPB datasheet(28/111 Pages) TI1

28 / 111 page

COP8CBR9, COP8CCR9, COP8CDR9

SNOS535I – OCTOBER 2000 – REVISED MARCH 2013

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Figure 5-3. Reset Circuit Using External Reset

5.7.2

On-Chip Brownout Reset

When enabled, the device generates an internal reset as VCC rises. While VCC is less than the specified

brownout voltage (Vbor), the device is held in the reset condition and the Idle Timer is preset with 00Fx

(240–256 tC). When VCC reaches a value greater than Vbor, the Idle Timer starts counting down. Upon

underflow of the Idle Timer, the internal reset is released and the device will start executing instructions.

This internal reset will perform the same functions as external reset. Once VCC is above the Vbor and this

initial Idle Timer time-out takes place, instruction execution begins and the Idle Timer can be used

normally. If, however, VCC drops below the selected Vbor, an internal reset is generated, and the Idle Timer

is preset with 00Fx. The device now waits until VCC is greater than Vbor and the countdown starts over.

When enabled, the functional operation of the device, at frequency, is ensured down to the Vbor level.

Figure 5-4. Brownout Reset Operation

One exception to the above is that the brownout circuit will insert a delay of approximately 3 ms on power

up or any time the VCC drops below a voltage of about 1.8V. The device will be held in Reset for the

duration of this delay before the Idle Timer starts counting the 240 to 256 tC. This delay starts as soon as

the VCC rises above the trigger voltage (approximately 1.8V). This behavior is shown in Figure 5-4.

In Case 1, VCC rises from 0V and the on-chip RESET is undefined until the supply is greater than

approximately 1.0V. At this time the brownout circuit becomes active and holds the device in RESET. As

the supply passes a level of about 1.8V, a delay of about 3 ms (td) is started and the Idle Timer is preset

to a value between 00F0 and 00FF (hex). Once VCC is greater than Vbor and td has expired, the Idle Timer

is allowed to count down (tid).

Functional Description

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Product Folder Links: COP8CBR9 COP8CCR9 COP8CDR9

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