NXP Semiconductors
PCF2127
Accurate RTC with integrated quartz crystal for industrial applications
9%%6 9''
P9
DDM
9'' 9
9'' 9
9'' 9
,%%6P$
Fig 14. Typical driving capability of VBBS: (VBBS VDD) with respect to the output load
current IBBS
8.7 Oscillator stop detection function
The PCF2127 has an on-chip oscillator detection circuit which monitors the status of the
oscillation: whenever the oscillation stops, a reset occurs and the oscillator stop flag OSF
(in register Seconds) is set logic 1.
• Power-on:
a. The oscillator is not running, the chip is in reset (OSF is logic 1).
b. When the oscillator starts running and is stable after power-on, the chip exits from
reset.
c. The flag OSF is still logic 1 and can be cleared (OSF set logic 0) by command.
• Power supply failure:
a. When the power supply of the chip drops below a certain value (Vlow), typically
1.2 V, the oscillator stops running and a reset occurs.
b. When the power supply returns to normal operation, the oscillator starts running
again, the chip exits from reset.
c. The flag OSF is still logic 1 and can be cleared (OSF set logic 0) by command.
PCF2127
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 8 — 19 December 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
27 of 100