ds1306et-r Maxim Integrated Products, Inc., ds1306et-r Datasheet - Page 9

• Manufacturer Part Number: ds1306et-r
• Description: Ds1306 Serial Alarm Real-time Clock
• Manufacturer: Maxim Integrated Products, Inc.

Table 2. TRICKLE CHARGER RESISTOR AND DIODE SELECT
If RS is 00, the trickle charger is disabled independently of TCS.
Diode and resistor selection is determined by the user according to the maximum current desired for
battery or super cap charging. The maximum charging current can be calculated as illustrated in the
following example. Assume that a system power supply of 5V is applied to V
connected to V
between V
As the super cap charges, the voltage drop between V
current decreases.
POWER CONTROL
Power is provided through the V
are illustrated in Figure 4. Configuration 1 shows the DS1306 being backed up by a non-rechargeable
energy source such as a lithium battery. In this configuration, the system power supply is connected to
V
backup mode. Upon power-up, the device switches from V
V
Configuration 2 illustrates the DS1306 being backed up by a rechargeable energy source. In this case, the
V
secondary supply (the rechargeable energy source). The DS1306 operates from the larger of V
V
V
Configuration 3 shows the DS1306 in battery-operate mode, where the device is powered only by a single
battery. In this case, the V
Only these three configurations are allowed. Unused supply pins must be grounded.
Bit 7
TCS
CC1
BAT
BAT
CC2
CC2
X
X
X
1
1
1
1
1
1
0
. When V
, V
and V
+ 0.2V. The device is write-protected whenever it is switched to V
pin is grounded, V
CC2
Bit 6
TCS
X
X
X
0
0
0
0
0
0
1
CC1
powers the DS1306. The DS1306 does not write-protect itself in this configuration.
CC2
and V
CC1
CC2
is grounded. When V
Bit 5
TCS
X
X
X
1
1
1
1
1
1
0
is greater than V
. Also assume that the trickle charger has been enabled with one diode and resister R1
CC2
I
MAX
. The maximum current I
Bit 4
TCS
X
X
X
0
0
0
0
0
0
1
CC1
CC1
= (5.0V - diode drop) / R1 » (5.0V - 0.7V) / 2kΩ » 2.2mA
and V
is connected to the primary power supply, and V
Bit 3
DS
X
0
1
0
0
0
1
1
1
1
CC1
CC2
BAT
, V
CC
+ 0.2V (typical), V
Bit 2
DS
pins are grounded and the battery is connected to the V
CC2
X
0
1
1
1
1
0
0
0
1
falls below V
, and V
Bit 1
RS
X
X
0
0
1
1
0
1
1
0
MAX
9 of 21
BAT
would, therefore, be calculated as follows:
Bit 0
RS
BAT
pins. Three different power supply configurations
X
X
CC1
0
1
0
1
1
0
1
0
CC1
the device switches into a low-current battery
and V
powers the DS1306. When V
Initial power-on state
BAT
CC2
2 Diodes, 2kΩ
2 Diodes, 4kΩ
2 Diodes, 8kΩ
1 Diode, 2kΩ
1 Diode, 4kΩ
1 Diode, 8kΩ
FUNCTION
Disabled
Disabled
Disabled
decreases and, therefore, the charge
to V
BAT
CC
.
when V
CC2
CC1
is connected to the
and a super cap is
CC
is greater than
CC1
CC2
is less than
pin.
CC1
or