AS3668 datasheet(20/60 Pages) AMSCO

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AS3668

Data Sheet - D e t a i l e d D e s c r i p t i o n

Figure 25. Reset Circuit Block Diagram

8.4 VBAT Monitor

The VBAT monitor is a supervisory circuit. The monitor is per default disabled when the AS3668 is powered up. The function can be used in order

to send the device automatically into standby mode if the supply voltage of AS3668 drops below the defined values in register vmon_vbat. All

together the user can select between three different voltage thresholds for this function with 3.375V, 3.3V and 3.0V. If the function is disabled the

device switches of if the battery voltage drops below 2.0V. The monitor function has also a debouncer with 100ms implemented in order to filter

the 217Hz GSM noise pulses from the battery supply voltage. Without the debouncer the chip would be susceptible to this noise and maybe

enter into standby mode due to a misinterpretation of the supply voltage.

Table 17. Power On Reset Parameters

Symbol

Parameter

Condition

Min

Typ

Max

Unit

VPOR_VBAT

Overall Power-On Reset

Monitor voltage on VBAT; power-on reset for all

internal functions.

2.0

VMON_VBAT

mode voltage

depending on register setting the voltage can be

configured

3.0V

3.3V

VPOR_PERI

Reset Level for pins SCL

Monitor voltage on pin SCL

1.0

tPOR_DEB

Reset debounce time for

pins SCL

110

130

150

tstart

Interface Startup Time

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