Z-World Fox LP3500 User Manual - page 128

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Fox (LP3500)

E.2.1  Replacing the Backup Battery

The battery is user-replaceable, and is fitted in a battery holder. To replace the battery, lift 

up on the spring clip and slide out the old battery. Use only a Panasonic CR2330 or equiv-

alent replacement battery, and insert it into the battery holder with the + side facing up.

NOTE:

The SRAM contents and the real-time clock settings will be lost if the battery is 

replaced with no power applied to the LP3500. Exercise care if you replace the battery 

while external power is applied to the LP3500.

NOTE:

Should it be more convenient, it is also possible to install the onboard battery on 

the other side of the LP3500 board.

CAUTION:

There is an explosion danger if the battery is short-circuited, recharged, or 

replaced incorrectly. Replace the battery only with the same type or an equivalent type 

recommended by the battery manufacturer. Dispose of used batteries according to the 

battery manufacturer’s instructions.

E.2.2  Power to VRAM Switch

The VRAM switch on the LP3500 module, shown in Figure E-3, allows the battery 

backup to provide power when the external power goes off. The switch provides an isola-

tion between Vcc and the battery when Vcc goes low. This prevents the Vcc line from 

draining the battery.

Figure E-3.  VRAM Switch

Field-effect transistor Q12 provides a very small voltage drop between Vcc and VRAM 

(

significantly different voltage than VRAM.

When the LP3500 is 

not

 in reset, the 

/RESOUT

 line will be high. This allows VRAM to 

nearly equal Vcc.

When the LP3500 

is

 in reset, the 

/RESOUT

 line will go low. This provides an isolation 

between Vcc and VRAM.

RESOUT

Q12

R46

/CS

220 k

W

Vcc

10 nF

C62

VRAM