PT7C4339 Datasheet, PDF (14/22 Pages) Pericom Semiconductor Corporation – Real-time Clock Module

PT7C4339/4339C
Real-time Clock Module
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Table3. Alarm 1 Mask Bits
Day,
Alarm 1 register mask bits
/Date A1M4 A1M3 A1M2 A1M1
Alarm rate

1
1
1
1 Alarm once per second

1
1
1
0 _{Alarm when seconds match}

1
1
0
0 Alarm when minutes and seconds match

1
0
0
0 Alarm when hours, minutes, and seconds match
0
0
0
0
0 Alarm when date, hours, minutes, and seconds match
1
0
0
0
0 Alarm when day, hours, minutes, and seconds match
Others
Ignored.
Table4. Alarm 2 Mask Bits
Day, Alarm 2 register mask bits
/Date A2M4 A2M3 A2M2

1
1
1

1
1
0

1
0
0
0
0
0
0
1
0
0
0
Others
Alarm rate
Alarm once per minute (00 seconds of every minute)
Alarm when minutes match
Alarm when hours, minutes
Alarm when date, hours, and minutes match
Alarm when day, hours, and minutes match
Ignored.
4.8. Trickle Charger Register (10h)
The simplified schematic in Figure 5 shows the basic components of the trickle charger. The trickle-charge select (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 VCC and VBACKUP. The ROUT bits (bits 0 and 1)
select the value of the resistor connected between VCC and VBACKUP. Table 5 shows the bit values.
Table5. Trickle Charger Register (10h)
BIT 7 BIT 6 BIT 5 BIT 4
TCS3 TCS2 TCS1 TCS0
X
X
X
X
X
X
X
X
X
X
X
X
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
0
0
0
BIT 3
DS1
0
1
X
0
1
0
1
0
1
0
BIT 2
DS0
0
1
X
1
0
1
0
1
0
0
BIT 1
ROUT1
X
X
0
0
0
1
1
1
1
0
BIT 0
ROUT0
X
X
0
1
1
0
0
1
1
0
Function
Disabled
Disabled
Disabled
No diode, 200Ω resistor
One diode, 200Ω resistor
No diode, 2kΩ resistor
One diode, 2kΩ resistor
No diode, 4kΩ resistor
One diode, 4kΩ resistor
Initial power-up values
Warning: The ROUT value of 200Ω must not be selected whenever V_CC is greater than 3.63V.
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 VCC and a super cap is connected to VBACKUP. Also assume that the trickle charger has been enabled with
a diode and resistor R2 between VCC and VBACKUP. The maximum current IMAX would therefore be calculated as follows:
IMAX = (3.3V - diode drop) / R2 ≈ (3.3V - 0.7V) / 2kΩ ≈ 1.3mA
As the super cap or battery charges, the voltage drop between VCC and VBACKUP decreases and therefore the charge
current decreases.
2015-08-0008
PT0508-1 08/24/15
14