DS1336 datasheet(2/6 Pages) DALLAS

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DS1336

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current when VCC is out of tolerance. The DS1336 switches back to the higher current VCC from battery

current when PF and PF become inactive.

OPERATION

The required PF or PF input which controls the switching between the main VCC and backup battery can

be supplied by any of the devices listed in Table 1. All of the devices provide the DS1336 with a PF or

signal, switching between a main supply VCC and backup supply VBAT when VCC falls out of

tolerance. For applications requiring switching from the VCC supply inputs to VBAT, the required PF or

input to the DS1336 can be provided by the DS1236, DS1239, DS5001, or DS5340. For applications

requiring switching from the VCC inputs to the VBAT input when VCC begins falling out of tolerance, any

of the Dallas Semiconductor devices listed in Table 1 can provide the DS1336 with the required

switching input. A typical application is shown in Figure 1.

For applications where switching between

VCC and VBAT must occur at a voltage level such that VCC is still greater than VBAT, the OUT5 pin is

recommended as it provides a diode path which will provide for a gradual transition between VCC and

VBAT. OUT5 can be tied to the other OUTPUT pins to provide a gradual transition for all five current

paths. In applications where tri-state switching is desired, OUT5 should be omitted. Only the PF/ PF pin

is required for switching. In cases where the PF input will not be used, it should be connected to GND.

When either PF or PF is active, either of the VBAT0X outputs is available, although they should not be tied

together (Figure 2, “DS1336 Block Diagram”). VBAT01 is recommended for sensitive applications such as

providing backup current to timekeepers, because its diode isolated path provides for increased

protection. VBAT02 is not recommended for applications where it would be tied to an OUTPUT pin

supplying a voltage greater than that of the backup battery because VBAT02 is not a diode isolated current

path.

TYPICAL APPLICATION Figure 1

DS1336 Datasheet(PDF) 2 Page - Dallas Semiconductor