Rainbow Electronics DS2404 - Manual (Page 22)

DS2404
22 of 29
V
CC
Operate Mode (Battery-Backed)
Figure 16 shows the necessary connections for operating the DS2404 in V
CC
Operate mode.
V
CC
OPERATE MODE Figure 16
V
CC
Pin 1 & 16 2.8V to 5.5V
V
BATB
Pin 9 2.8V to 5.5V
V
BATO
Pin 10 must be unconnected
To always allow communication through the 1-Wire or wire port, the voltage on V
CC
must be
approximately 3-wire port, the voltage on V
CC
must be approximately 0.2V above the voltage on V
BATB
.
Otherwise the DS2404 will retain data, but will not allow any access.
The V
BATB
pin is normally connected to any standard 3V lithium cell or other energy source. As V
CC
falls
below V
BATB
, the power switching circuit allows V
BATB
to provide energy for maintaining clock
functionality and data retention. No communication can take place while V
BATB
is greater than V
CC
.
During power-up, when V
CC
reaches a value of approximately 0.2V above V
BATB
, the power switching
circuit connects V
CC
and disconnects V
BATB
. If the oscillator is on, no communication can take place until
V
CC
has stayed approximately 0.2V above V
BATB
for 123 ± 2ms. During power-down, the falling V
CC
must pass the range from V
BATB
to 0V in no less than 100ns for the power switching circuit to function
properly.