DS32C35-33#T&R

Real Time Clock Overview

The DS32C35-33#T&R is an accurate real-time clock (RTC) and calendar integrated with a temperature-compensated crystal oscillator (TCXO), crystal, and 8192-bit FRAM. It operates on a fast 400kHz I²C interface within a 20-pin SO package. The device provides seconds, minutes, hours, day, date, month, and year information with leap-year compensation valid to 2100. Operating voltage ranges from 2.7V to 3.63V, with battery backup support between 2.3V and 3.6V. Standby current is typically 110µA at 3.63V. Accuracy is ±2ppm from 0°C to +40°C and ±3.5ppm from -40°C to 0°C and +40°C to +85°C.

Real Time Clock Feature Summary

• Integrated TCXO and crystal for enhanced long-term accuracy
• 8192-bit nonvolatile FRAM with no write cycle limitations
• Two time-of-day alarms and programmable square-wave output
• Precision temperature sensor with ±3°C accuracy

Real Time Clock Applications

• Servers
• Utility Power Meters
• Telematics
• GPS systems

Real Time Clock Procurement Notes

Verify the specific suffix '#T&R' against manufacturer documentation to confirm tape-and-reel packaging status, as datasheet ordering tables list bulk 'SO' packages. Confirm RoHS compliance via the '#' designation in official component markings. Check lead finish specifications (JESD97 category e3) for soldering process compatibility.

Real Time Clock Selection Notes

Select the DS32C35 variant over DS32B35 when 8192 bytes of FRAM are required instead of 2048 bytes. Ensure the operating environment stays within the specified commercial or industrial temperature ranges. Verify that the system power supply remains above the power-fail threshold (VPF) during FRAM access to prevent data corruption.

Real Time Clock Part Context

This component belongs to the DS32x35 family, which includes DS32B35 and DS32C35 variants. These devices share the same die but differ in FRAM density. The DS32C35 specifically offers higher memory capacity while maintaining the same high-precision timing features and I²C interface characteristics as its counterparts.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers: DS32B35-33#T&R (lower FRAM density).

Real Time Clock FAQ

What is the difference between DS32B35 and DS32C35?

The primary difference is the FRAM memory density. DS32B35 contains 2048 x 8 bits of FRAM, while DS32C35 contains 8192 x 8 bits. Both share identical RTC accuracy, interfaces, and pinouts.

How does the device handle power failure?

A precision reference monitors VCC. When VCC falls below the power-fail voltage (VPF), the device automatically switches to the VBAT backup supply to maintain RTC/TCXO operation. The RST pin indicates this status.

Can the FRAM be accessed during battery backup?

No. The FRAM is only accessible when the device is powered by VCC. Accessing FRAM when VCC is below the minimum operating voltage may result in data errors due to destructive read mechanisms.