DS32KHZSLASHDIP datasheet(6/8 Pages) DALLAS

6 / 8 page

DS32kHz

6 of 8

The DS32kHz is packaged in a 36-pin ball grid array (BGA). It also is available in a 16-pin 0.300” SO and a 14-pin

encapsulated DIP (EDIP) module.

The additional PC board space required to add the DS32kHz as an option for driving a RTC is negligible in many

applications (see Figure 6) Therefore, adding the DS32kHz to new designs and future board revisions allows the

use of the DS32kHz where applications require improved timekeeping accuracy.

Figure 3. Block Diagram

OPERATION

The DS32kHz module contains a quartz tuning-fork crystal and an IC. When power is first applied, and when the

device switches between supplies, the DS32kHz measures the temperature and adjusts the crystal load to

compensate the frequency. The power supply must remain at a valid level whenever a temperature measurement

is made, including when VCC is first applied. While powered, the DS32kHz measures the temperature once every

64 seconds and adjusts the crystal load.

The DS32kHz is designed to operate in two modes. In the dual-supply mode, a comparator circuit, powered by VCC,

monitors the relationship between the VCC and VBAT input levels. When VCC drops below a certain level compared to

VBAT, the device switches over to VBAT (Figure 4A). This mode uses VCC to conserve the battery connected to VBAT

while VCC is applied.

In the single-supply mode, VCC is grounded and the unit is powered by VBAT. Current consumption is less than VCC,

because the comparator circuit is unpowered (Figure 4B).

Figure 4A shows how the DS32kHz should be connected when using two power supplies. VCC should be between

4.5V and 5.5V, and VBAT should be between 2.7V and 3.5V. Figure 4B shows how the DS32kHz can be used when

only a single-supply system is available. VCC should be grounded and VBAT should then be held between 2.7V and

5.5V. The VBAT pin should be connected directly to a battery. Figure 4C shows a single-supply mode where VCC is

held at +5V. See the frequency stability vs. operating voltage for information about frequency error vs. supply

voltage.

Temperature

Measurement

BAT

32.768kHz

Power

Switching

Circuit

GND

Power Control

Dallas

Semiconductor

DS32kHz

DS32KHZ/DIP Datasheet(PDF) 6 Page - Dallas Semiconductor