User`s manual

142 eDisplay (OP7200)
B.2.2 External Battery
As an alternative to preserving the SRAM contents and the real-time clock settings while
changing the backup battery, you may connect an external battery temporarily at header J7.
The
pins on header J7 have ground on the ends and positive in the center to allow the external
battery to be connected without the potential of reversing its polarity. Connect the positive
terminal of the external battery to pin 2 and the negative terminal to either pin 1 or pin 3 of
header J7.
The onboard battery does not have to be removed as it is protected against overvoltage by
resistors R80–R81. By having both batteries connected, either can be replaced from time
to time without losing the data stored in the SRAM and the real-time clock. The external
battery should be no more than 6.3 V.
Figure B-2. OP7200 External Battery Connections
J3
J10
J2
J6
J7
Battery
J1
R2
C3
D2
R7
C27
R8
R36
RT1
R41
R37
R38
D1
R39
Y2
C2
C1
U8
U7
U3
U6
C7
GND
GND
EGND
DS2
LNK
ACT
DS1
R19
Q3
Q4
Q5
Q2
R1
Y1
C4
C17
C8
R9
R13
R11
U1
BT1
R15
C12
R17
R20
C13
Y3
R16
R22
R21
C14
R18
C25
C28
D3
J2
JP4
JP3
JP1
JP6
C30
JP2
JP5
C29
U2
Flash
EPROM
External
Battery
J7
VBAT
D11
1 kW
R81
1
2
3