MP6411GS datasheet(13/14 Pages) MPS

13 / 14 page

MP6411―WINDOWED WATCHDOG TIMER

MP6411 Rev. 1.1

www.MonolithicPower.com

1/24/2018

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

OPERATION

Supply Voltage

VCC= 5V

10% is recommended for MP6411

normal operation; while VCC= 3.3V

10% is

recommended for MP6411-33 normal operation.

WDO is pulled low when VCC rises to 1V or

above. After VCC rises to 90% (typically), WDO

will remain at a low level for t0 to reset the MCU.

TIMER

Period T (

s):



 





 

TIMER

T s

15.75 R

73.5

RTIMER (k):



 





 

TIMER

0.063 T s

4.67

For example: RTIMER=51kΩ, T0.88ms

Monitor MCU Synchronization Signal

When the watchdog is in a “sync signal

monitoring state,” the following will occur:

 If the watchdog IC receives a WDI_OK

signal from the MCU within t1 (WDI remains

low for 10µs to 5ms), the timer will be reset,

and

the

watchdog

works

normal

operation.

 If the watchdog does not receive the

WDI_OK signal from the MCU during t1, it

will generate a reset signal and go into

“sync signal monitor state” again.

Short Window Mode

If the MCU and watchdog are synchronized

correctly and MODE is low, the watchdog will

work in short window mode:

 If WDI_OK is received in a window close

state (t2), the watchdog outputs a reset

signal and goes into a sync signal

monitoring state.

 If WDI_OK is received in a window open

state (t3), the watchdog goes into a window

close state. The MCU works in normal

operation in this situation.

 If no WDI_OK signal is received in t2+t3, the

watchdog outputs a reset signal and goes

into a sync signal monitoring state.

 If MODE is pulled high during short window

mode, the watchdog will go into long

window mode.

Long Window Mode

If the MCU and watchdog are synchronized

correctly and MODE is high, the watchdog will

operate in long window mode, and the following

will occur:

 If WDI_OK is received in a window close

state (t4), the watchdog outputs a reset

signal and goes into a sync signal

monitoring state.

 If WDI_OK is received in a window open

state (t5), the watchdog goes into a window

close state. The MCU works in normal

operation in this situation.

 If no WDI_OK signal is received in t4+t5, the

watchdog outputs a reset signal and goes

into a sync signal monitoring state.

 If MODE is pulled low during a long window

mode, the watchdog will go into a short

window mode.

Watchdog Disable

Pull /WD_DIS low to disable the watchdog; pull

it high to enable the watchdog. /WD_DIS has a

weak internal pull-up, so the watchdog is

enabled if /WD_DIS is left open.

WDI Error

If a WDI signal remains at a low level for longer

than the maximum WDI_OK pulse width, it is

regarded as an error. When this error occurs,

WDO is pulled down until WDI returns to a high

level.

MP6411GS Datasheet(PDF) 13 Page - Monolithic Power Systems

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