d1340-33 Maxim Integrated Products, Inc., d1340-33 Datasheet - Page 9

• Manufacturer Part Number: d1340-33
• Description: Ds1340, Ds1340c I?c Rtc With Trickle Charger
• Manufacturer: Maxim Integrated Products, Inc.

Bit 7: Output Control (OUT). This bit controls the out-
put level of the FT/OUT pin when the FT bit is set to 0. If
FT = 0, the logic level on the FT/OUT pin is 1 if OUT = 1
and 0 if OUT = 0. The initial power-up OUT value is 1.
Bit 6: Frequency Test (FT). When this bit is 1, the
FT/OUT pin toggles at a 512Hz rate. When FT is written
to 0, the OUT bit controls the state of the FT/OUT pin.
The initial power-up value of FT is 0.
Bit 5: Calibration Sign Bit (S). A logic 1 in this bit indi-
cates positive calibration for the RTC. A 0 indicates
negative calibration for the clock. See the Clock
Calibration section for a detailed description of the bit
operation. The initial power-up value of S is 0.
Bits 4 to 0: Calibration Bits (CAL4 to CAL0). These
bits can be set to any value between 0 and 31 in binary
form. See the Clock Calibration section for a detailed
description of the bit operation. The initial power-up
value of CAL0–CAL4 is 0.
The simplified schematic in Figure 6 shows the basic
components of the trickle charger. The trickle-charge
select (TCS) bits (bits 4–7) 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
Figure 6. Trickle Charger Functional Diagram
Trickle-Charger Register (08h)
V
BIT 7
TCS3
CC
NOTE: ONLY 1010b
ENABLES CHARGER
BIT 6
TCS2
1 OF 16 SELECT
Control Register (07h)
TCS1
BIT 5
TCS0
BIT 4
_____________________________________________________________________
BIT 3
DS1
SELECT
1 OF 2
I
BIT 2
DS0
2
C RTC with Trickle Charger
ROUT1
BIT 1
SELECT
1 OF 3
ROUT0
BIT 0
is disabled when power is first applied. The diode-
select (DS) bits (bits 2, 3) select whether or not a diode
is connected between V
no diode is selected; if DS is 10, a diode is selected.
The ROUT bits (bits 0, 1) select the value of the resistor
connected between V
the resistor selected by the resistor select (ROUT) bits
and the diode selected by the diode select (DS) bits.
Warning: The ROUT value of 250Ω must not be select-
ed whenever V
The user determines diode and resistor selection
according to the maximum current desired for battery
or super cap charging (Table 4). The maximum charg-
ing current can be calculated as illustrated in the fol-
lowing example.
Assume that a 3.3V system power supply is applied to
V
assume that the trickle charger has been enabled with
a diode and resistor R2 between V
The maximum current I
ed as follows:
As the super cap charges, the voltage drop between
V
current decreases.
CC
CC
I
MAX
and V
and a super cap is connected to V
TCS
DS
TOUT
= (3.3V - diode drop) / R2 ≈ (3.3V - 0.7V) /
0-1
0-3
BACKUP
0-1
= DIODE SELECT
= TRICKLE-CHARGER SELECT
= RESISTOR SELECT
CC
is greater than 3.63V.
250Ω
2kΩ
4kΩ
decreases and therefore the charge
R1
R2
R3
2kΩ ≈ 1.3mA
CC
MAX
CC
and V
would therefore be calculat-
and V
V
BACKUP
BACKUP
BACKUP
CC
. Table 3 shows
and V
BACKUP
. If DS is 01,
BACKUP
. Also
9
.