7. INTERNAL STRUCTURE
7.3 Real-Time Clock (RTC)
The Vision 307 includes a Real-Time Clock (RTC) with a backup power system. When the device is con-
nected to the vehicle’s battery via the main connector’s (C1) BAT+ pin, the Real-Time Clock is supplied by
the vehicle’s battery regardless of whether the device is operational or not.
The Vision 307 is equipped with an internal super-capacitor which provides approximately 14 days of backup
time (when fully charged). The capacitor is charged to 90% after 2 hours, and fully charged after 5 hours. It
is charging if the BAT+ pin is connected to the vehicle’s battery.
To maintain RTC data for longer periods of time, the RTC can be powered by an external battery, connecting
the positive terminal of the battery to the main connector’s (C1) RTC supply pin. It is advised to use a sin-
gle 3 V primary (non-rechargeable) lithium cell, or two 1.5 V alkaline cells connected in series for this purpose.
NOTE
It is not advised to leave the RTC pins unconnected, as this leads to an increased internal current draw
of the RTC, and reduces the retention time provided by the super-capacitor.
7.3.1 Characteristics
Symbol Parameter Note Min Max Unit
Δ min/year Time variation per year at 25
○
C -15 +15 min/year
t
pr
RTC power reserve 1 14 days
C
in
Pin input capacitance 8 12 nF
V
in
Nominal input voltage 2.5 3.3 V
I
in-nom
Steady state input current at 3.3 V 10 µA
I
in-max
Steady state input current at 33 V 600 µA
Note 1 If the super-capacitor has been charged for at least 5 hours with V
BAT+
> 9 V.
© TTControl GmbH 2024. All rights reserved.
Proprietary Information
33
Document Number:
D-156-G-02-003
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