RX8111CE
Page
−
11
ETM61E-01
10. Power Supply Sequence
10.1. Power Supply Sequence
This circuit is sensitive to power supply noise and supply voltage should be stabilized to avoid negative impact
on the accuracy.
tR1 is needed for a proper power-on reset. If this power-on condition cannot be kept, it is necessary to
send an initialization routine to the RTC by software.
In case of repeated ON/OFF of the power supply within short term, it is possible that the power-on reset
will become unstable.
After power OFF, keep V
DD
= V
BAT
= GND for more than 10 seconds for a proper power-on reset.
When it is unstable, please initialize the RTC by the software.
Power-on-reset occurs on rising edge of V
OUT
voltage.
Note: During first Power ON for internal initialization, V
DD
must be over 1.45 V: +V
DET1
.
V
Main
GND
V
DD
t
R1
t
F
t
R2
+
V
DET1
Back-up operation
t
CL
t
CD
t
CU
-
V
DET1
+
V
DET1
I
2
C
Communication
Communication
Access denied
V
DD
V
CLK
_Min
GND
V
OUT
t
R1
GND
V
BAT
V
BAT
*
1
Figure 14 Power on Sequence
Table 9 Power up down characteristics
Item
Symbol
Condition
Min.
Typ.
Max.
Unit
Power supply rise time1
tR1
V
OUT
rise time
by V
DD
or V
BAT
.
3 V
0.1
-
10
ms / V
5 V
0.5
-
10
ms / V
Access wait time.
After initial power on.
tCL
After V
DD
reach to +V
DET1
30
-
-
ms
Access disable hold time
tCD
After I
2
C communication.
0
-
-
ms
Power supply fall time
tF
Time of -V
DET1
from, V
DD
max.
1
-
-
ms / V
Power supply rise time2
tR2
V
DD
reach to +V
DET1
From GND.
0.1
-
-
ms / V
Access wait time
( Normal power on)
tCU
Waiting time before starting I
2
C
from Power-ON.
40
-
-
ms