Electronic Design

Low-Voltage Timekeeping IC Integrates Many Functions

With its DS1672 timekeeping chip, Dallas Semiconductor has crafted a low-voltage clock that also performs power monitoring, backup power switching, and optional trickle charging. This IC is available in three versions for operation at 2.0, 3.0, or 3.3 V. It combines low-voltage timekeeping with power-fail protection for applications in battery-powered equipment such as cell phones, GPS units, laptop computers, and other handheld devices.

For timekeeping, the chip contains a 32-bit counter that counts time in seconds (see the figure). An external microprocessor uses this information to calculate the time of day, the week, the month, and the year. The processor and the timekeeping chip communicate over a two-wire serial interface.

When the on-chip voltage monitor detects an undervoltage condition on the main power supply, the DS1672 write-protects timekeeping data registers, resets the processor, and switches to backup power to prevent data corruption. In the low-power mode, the oscillator maintains timekeeping down to 1.3 V while consuming less than 200 nA. When the power supply returns to normal voltage levels, the DS1672 holds the processor in the reset mode for 250 ms while operating conditions stabilize. Additionally, the IC can be used to trickle-charge a backup battery.

Now sampling, the DS1672 is offered in 8-pin DIPs, SOPs, and µSOPs. Pricing varies from $1.18 each for DIPs and SOPs to $1.35 each for µSOPs, ordered in 1000-unit quantities.

Dallas Semiconductor, 4401 S. Beltwood Pkwy., Dallas TX 75244; Jim Waldron, (972) 371-4322; [email protected]; www.dalsemi.com/datasheets/pdfs/1672.pdf.

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