DS1343E-33+T&R

Real Time Clock Overview

The DS1343E-33+T&R is a low-current real-time clock (RTC) IC manufactured by Analog Devices Inc./Maxim Integrated. It provides timekeeping and calendar functions including seconds, minutes, hours, day, date, month, and year with leap year compensation valid through 2099. The device supports SPI or 3-wire serial interfaces and includes 96 bytes of battery-backed non-volatile RAM. Electrical specifications include a supply voltage range of 3.0V to 5.5V and a backup voltage range of 1.3V to 5.5V. Typical standby current is 250nA, while active current ranges from 120µA to 160µA at 3.63V to 5.5V. It operates within an industrial temperature range of -40°C to +85°C.

Real Time Clock Feature Summary

• Low Timekeeping Current: Typical standby current of 250nA.
• High ESR Crystal Support: Compatible with crystals up to 100kΩ ESR.
• Integrated Capacitive Loading: Supports 6pF crystals for DS1343 variants.
• Dual Alarms: Two programmable time-of-day alarms with interrupt outputs.

Real Time Clock Applications

• Medical devices
• Handheld devices
• Telematics systems
• Embedded timestamping

Real Time Clock Procurement Notes

Verify the package type matches the required design; the 'E' suffix indicates a 20-pin TSSOP package, whereas other suffixes may denote different form factors. Confirm the ordering suffix '+T&R' corresponds to the tape-and-reel packaging format required for automated assembly processes.

Real Time Clock Selection Notes

Select this component when a 3.0V to 5.5V supply voltage is available. Ensure the application utilizes a crystal with a load capacitance of 6pF, as this specific variant integrates internal capacitors for that value. Verify that the system requires SPI or 3-wire interface compatibility rather than I2C.

Real Time Clock Part Context

This part belongs to the DS1343/DS1344 family of low-current RTCs. The primary distinction between the DS1343 and DS1344 models is the integrated capacitive loading for the external crystal oscillator. The DS1343 supports 6pF crystals, while the DS1344 supports 12.5pF crystals. Both share identical pinouts and functional registers.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not provided in the source material.

Real Time Clock FAQ

What is the difference between the DS1343 and DS1344 regarding crystal selection?

The DS1343 includes integrated capacitive loading for a 6pF crystal, while the DS1344 includes loading for a 12.5pF crystal.

How does the power-fail circuitry operate?

The device detects power failure via the PF pin when VCC drops below the trip point (VPF). It automatically switches power to the VBAT backup supply and blocks access to internal clock registers during the transition.

Can the trickle charger be enabled on initial power-up?

No. On initial power-up, the trickle charger is disabled by default. It must be explicitly enabled by writing the specific pattern 1010 to the TCS bits in the Trickle Charger register.