DS1343 Maxim, DS1343 Datasheet - Page 15

• Manufacturer Part Number: DS1343
• Description: The DS1343/DS1344 low-current real-time clocks (RTCs) are timekeeping devices that provide an extremely low standby current, permitting longer life from a backup supply source
• Manufacturer: Maxim

X = Don’t care.
Assume, for the purposes of the example, that a system
power supply of 5V is applied to V
connected to V
has been enabled with one diode and resistor R1. The
maximum current I
As the super cap charges, the voltage drop between
V
current decreases.
Figure 2. Trickle Charger Block Diagram
Table_3._Trickle-Charger_Resistor_and_Diode_Select
CC
I
TCS3
MAX
X
X
X
1
1
1
1
1
1
0
and V
CHARGER
REGISTER
TRICKLE
= (5.0V - diode drop)/R1 ≈ (5.0V - 0.6V)/2kΩ ≈
BAT
V
TCS2
CC
NOTE: ONLY 1010 CODE ENABLES CHARGER
BIT 7
TCS
X
X
X
0
0
0
0
0
0
0
BAT
decreases, and therefore, the charge
MAX
. Also assume that the trickle charger
BIT 6
TCS
1 0F 18 SELECT
TCS1
would be calculated as follows:
2.2mA
X
X
X
1
1
1
1
1
1
0
BIT 5
TCS
TCS0
CC
X
X
X
0
0
0
0
0
0
0
BIT 4
TCS
and a super cap is
BIT 3
DS
DS1
Low-Current SPI/3-Wire RTCs
X
0
1
0
0
0
1
1
1
0
SELECT
1 OF 2
BIT 2
DS
DS0
X
0
1
1
1
1
0
0
0
0
BIT 1
RS
SELECT
The devices offer the flexibility to choose between two
serial-interface modes. The component can commu-
nicate with the SPI interface or with a standard 3-wire
interface. The interface method used is determined by
SERMODE. When SERMODE is connected to V
communication is selected. When SERMODE is con-
nected to ground, standard 3-wire communication is
selected.
1 OF 3
RS1
BIT 0
RS
X
X
0
0
1
1
0
1
1
0
TCS = TRICKLE-CHARGER SELECT
DS = DIODE SELECT
RS = RESISTOR SELECT
RS0
0
X
X
1
0
1
1
0
1
0
Serial Port Operation
Initial power-on state—disabled
1k Ω
2k Ω
4k Ω
One diode, 1kI
One diode, 2kI
One diode, 4kI
R1
R2
R3
No diode, 1kI
No diode, 2kI
No diode, 4kI
FUNCTION
Disabled
Disabled
Disabled
V
BAT
CC
, SPI
15