M41T00AUDD1E STMICROELECTRONICS [STMicroelectronics], M41T00AUDD1E Datasheet - Page 22

• Manufacturer Part Number: M41T00AUDD1E
• Description: Serial real-time clock with audio
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

5.4
Figure 13. Switchover thresholds
22/44
V CC (= 3.3V)
V BACK (> V PFD )
Switchover voltage
V SO = V PFD (= 2.8V)
STATE
V CC (= 3.3V)
V PFD = 2.8V
V SO = V BACK (< V PFD )
STATE
Switchover voltage
Switchover thresholds
While the M41T00AUD includes a precision reference for the backup switchover threshold, it
is not a fixed value, but depends on the backup voltage, V
switchover at the lesser of the reference voltage (V
This ensures that it stays on V
As shown in
drops below V
Conversely, when V
V
BACK
.
Table 14
Figure
PFD
provides the values of these voltages.
.
On V CC
On V CC
BACK
13, whenever V
is less than V
Condition 2: V BACK < 2.8V (V PFD )
Condition 1: V BACK > 2.8V (V PFD )
CC
as long as possible before switching to the backup supply.
BACK
PFD
is greater than V
, switchover occurs when V
On V BACK
On V BACK
PFD
, approximately 2.8V) and V
PFD
BACK
, switchover occurs when V
. The device will always
CC
drops below
On V CC
On V CC
BACK
ai13326
.
CC