DS1339 Maxim, DS1339 Datasheet - Page 15

• Manufacturer Part Number: DS1339
• Description: The DS1339 serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day alarms and a programmable square-wave output
• Manufacturer: Maxim

TRICKLE CHARGER REGISTER (10h)
The simplified schematic in
(TCS) bits (bits 4 to 7) control the selection of the trickle charger. To prevent accidental enabling, only a pattern on
1010 enables the trickle charger. All other patterns disable the trickle charger. The trickle charger is disabled when
power is first applied. The diode-select (DS) bits (bits 2 and 3) select whether or not a diode is connected between
V
Table 6
Table 6. Trickle Charger Register (10h)
Warning: The ROUT value of 250Ω must not be selected whenever V
The user determines diode and resistor selection 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 3.3V system power supply is applied to V
trickle charger has been enabled with a diode and resistor R2 between V
would therefore be calculated as follows:
As the super cap or battery charges, the voltage drop between V
charge current decreases.
CC
TCS3
BIT 7
X
X
X
1
1
1
1
1
1
0
and V
shows the bit values.
BACKUP
TCS2
BIT 6
X
X
X
0
0
0
0
0
0
0
. The ROUT bits (bits 0 and 1) select the value of the resistor connected between V
TCS1
BIT 5
X
X
X
1
1
1
1
1
1
0
I
MAX
Figure 5
BIT 4
TCS0
X
X
X
0
0
0
0
0
0
0
= (3.3V - diode drop) / R2 ≈ (3.3V - 0.7V) / 2kΩ ≈ 1.3mA
shows the basic components of the trickle charger. The trickle-charge select
BIT 3
DS1
X
0
1
0
1
0
1
0
1
0
BIT 2
DS0
CC
0
1
X
1
0
1
0
1
0
0
and a super cap is connected to V
15 of 20
ROUT1
BIT 1
X
X
0
0
0
1
1
1
1
0
ROUT0
BIT 0
CC
X
X
0
1
1
0
0
1
1
0
and V
CC
and V
Disabled
Disabled
Disabled
No diode, 250Ω resistor
One diode, 250Ω resistor
No diode, 2kΩ resistor
One diode, 2kΩ resistor
No diode, 4kΩ resistor
One diode, 4kΩ resistor
Initial power-up values
BACKUP
DS1339 I
CC
BACKUP
is greater than 3.63V.
decreases and therefore the
BACKUP
. The maximum current I
FUNCTION
2
C Serial Real-Time Clock
. Also assume that the
CC
and V
BACKUP
MAX
.