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L4969

1.4

Oscillator

A low power oscillator provides an internal clock. In sleep mode (Watchdog active) the output frequency is

250kHz, if the Watchdog function is not requested, the internal Oscillator is switched off.

In standby and operating mode the oscillator is running at 1MHz, and can be calibrated in a range from -16% to

+16% using the

1.5

WatchdL4969og

A triple function programmable watchdog is integrated to perform the following tasks:

– Wakeup Watchdog:

When in sleep or standby mode the watchdog can generate a wakeup condition after a programma-

ble period of time ranging from 80ms up to 45 minutes

– Startup Watchdog:

Upon V1 power-up or

ated periodically every 320ms for 2.5ms until activity of the

knowledge is received within 7 cycles (2.2sec). In this condition the device is forced into Sleep mode

until a Wakeup is detected and a startup cycle is reinitialized.

– Window Watchdog:

After passing the startup sequence, this watchdog request an acknowledge by the

within a programmable timing frame, ranging from 2.5 ... 5ms up to 20 ... 40ms. Upon a missing or

misplaced acknowledge the Startup Watchdog is initialized.

1.6

Reset

1.6.1 Power-on Reset

Upon Power-on (VS > 3.5V), the internal reset forces the device into a predefined power-on state (see 1.1):

Standby #3:V1 on V2 off V3 off,CAN-Standby mode, ID-Filter disabled, Startup Watchdog active

With VS below 5V the regulator V1 will follow VS with minimum drop. The

below a programmable voltage level of either 4.5V (default) or 4.0V. The programmed state of the L4969 re-

mains unchanged. The act. low Resetpulse duration is fixed internally by an open-drain output stage to 1ms.

However, this time can be externally extended by an additional capacitance connect between NRESET and

GROUND which is then charged by the internal pull-up of typ. 120K. Depending on the Reset-Input-Threshold

0.5) = 600nF is required.

Figure 4.

1.6.2

Undervoltage Reset

Upon detection of a V1 voltage level below a programmable voltage level of either 4.5V (default) or 4.0V,the

NRES-pin is pulled low. Since this undervoltage detection is additionally sampled periodically every ms, the

V1

120K

NRES

to Reset Input of uC