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51525354555657585960
3
64
59 0
1
58
2Seconds
59 0
1
58
2
Hours
3 4Hours
59 0 1
Seconds
Compensation event
Compensation event
swcs046-015
TPS65910
,
TPS65910A
,
TPS65910A3
,
TPS659101
TPS659102
,
TPS659103
,
TPS659104
,
TPS659105
TPS659106, TPS659107, TPS659108, TPS659109
www.ti.com
SWCS046U –MARCH 2010–REVISED JUNE 2014
Figure 6-5. RTC Compensation Scheduling
This drift can be balanced to compensate for any inaccuracy of the 32-kHz oscillator. Software must
calibrate the oscillator frequency, calculate the drift compensation versus one time hour period; and then
load the compensation registers with the drift compensation value. Indeed, if the AUTO_COMP_EN bit in
the RTC_CTRL_REG is enabled, the value of COMP_REG (in twos-complement) is added to the RTC 32-
kHz counter at each hour and one second. When COMP_REG is added to the RTC 32-kHz counter, the
duration of the current second becomes (32768 - COMP_REG)/32768s; so, the RTC can be compensated
with a 1/32768 s/hour time unit accuracy.
NOTE
The compensation is considered once written into the registers.
6.6 Backup Battery Management
The device includes a back-up battery switch connecting the VRTC regulator input to a main battery
(VCC7) or to a back-up battery (VBACKUP), depending on the batteries voltage value.
The VRTC supply can then be maintained during a BACKUP state as far as the input voltage is high
enough (>VBNPR threshold). Below the VBNPR voltage threshold the digital core of the device is set
under reset by internal signal POR (Power-on Reset).
The back-up domain functions which are always supplied from VRTC comprehend:
• The internal 32-kHz oscillator
• Backup registers
The back-up battery can be charged from the main battery through an embedded charger. The back-up
battery charge voltage and enable is controlled through BBCH_REG register programming. This register
content is maintained during the device Backup state.
Hence enabled the back-up battery charge is maintained as far as the main battery voltage is higher than
the VMBLO threshold and the back-up battery voltage.
Copyright © 2010–2014, Texas Instruments Incorporated Detailed Description 55
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