
DS1672
9 of 12
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 3V is applied to V
CC
and a super cap is
connected to V
BACKUP
. Also assume that the trickle charger has been enabled with a diode and resistor R2
between V
CC
and V
BACKUP
. The
maximum current I
MAX
would, therefore, be calculated as follows:
I
MAX
= (5.0V - diode drop) / R1 » (5.0V - 0.7V) / 2kW » 2.2mA
As the super cap changes, the voltage drop between V
CC
and V
BACKUP
will decrease and, therefore, the
charge current will decrease.
Figure 5. Programmable Trickle Charger
1 OF 16 SELECT
NOTE: ONLY 1010 ENABLES
1 OF 2
SELECT
1 OF 3
SELECT
TCS TCS TCS TCS DS DS RS RS
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
250W
R1
R2
TRICKLE CHARGE REGISTER
TCS = TRICKLE CHARGER SELECT
DS = DIODE SELECT
RS = RESISTOR SELECT
V
CC
V
BACKUP
2kW
R3
4kW
Kommentare zu diesen Handbüchern