DS1338Z-3+T&R - I2C RTC with 56B NV RAM | Analog Devices
MPN: DS1338Z-3+T&R ✓ ActiveDS1338Z-3+T&R Overview
A real-time clock is a timing IC that maintains calendar information independently of the host processor's main clock. The DS1338 belongs to the RTC and clock/calendar hierarchy within clock and timing integrated circuits. By separating continuous timekeeping from the central processing unit, it reduces firmware overhead and allows the system time to remain available across resets, power interruptions, and low-power operating states when supported by the associated backup supply arrangement.
Key features include a full binary-coded decimal clock/calendar, automatic month-end correction, 56 bytes of nonvolatile RAM, serial two-wire communication, and an operating temperature range of -40 C to +85 C. The 2.7 V to 5.5 V operating range supports both 3.3 V and 5 V system rails. Its SOIC-8 package provides a conventional surface-mount footprint compatible with automated assembly and compact mixed-signal or embedded-control boards.
The RTC architecture separates calendar processing from the external host while the I2C interface exposes registers and RAM to the processor. Firmware can read the current time, configure clock settings, and use the 56-byte RAM for small amounts of retained configuration or diagnostic information. Because the communication bus is shared, address integrity, pull-up implementation, and software access timing are important considerations when the device shares an I2C segment with sensors, memory, or interface expanders.
Typical uses include industrial data loggers, building automation controllers, medical monitoring equipment, security systems, industrial sensors, and compact communication equipment. In each case, the device can maintain wall-clock time while the main controller sleeps or restarts. The integrated RAM also allows small system-specific values to survive a reset without adding a separate memory component.
The principal design consideration is preserving an accurate reference during supply interruptions. The DS1338Z-3+T&R is specified for 2.7 V to 5.5 V operation and includes NV RAM, but the supplied product information does not state the backup-battery configuration, oscillator accuracy, or capacitor values. Those parameters must therefore be confirmed in the manufacturer datasheet before finalizing a timekeeping circuit.
This product record combines verified manufacturer and distributor information with package, interface, comparison, and design guidance. It identifies where the DS1338Z-3+T&R fits within embedded timekeeping designs, documents the verified 56-byte RAM and I2C characteristics, and distinguishes supported drop-in alternatives without introducing unverified electrical claims.
Drop-in alternatives for DS1338Z-3+T&R — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with DS1338Z-3+T&R (same form factor and footprint) — differing in Package, Device Type, Serial Interface, Mounting Type, Supply Voltage Range.
DS1338Z-33+T&R
✅ Drop-InContact for price
View Datasheet →DS1338Z-3+
✅ Drop-InContact for price
View Datasheet →DS1340Z-18+
✅ Drop-In📋 Reference alternative (not in catalog)
DS1340Z-33+
✅ Drop-In📋 Reference alternative (not in catalog)
FRTC1338S
✅ Drop-In📋 Reference alternative (not in catalog)
PT7C433833WEX
✅ Drop-In📋 Reference alternative (not in catalog)
DS1338Z-3+T&R Specifications
| Device Type | Serial real-time clock and clock/calendar with nonvolatile RAM |
| RTC Memory | 56 bytes nonvolatile RAM |
| Serial Interface | I2C, 2-wire serial |
| Time Format | Full binary-coded decimal (BCD) |
| Calendar Information | Seconds, minutes, hours, day, date, month, and year |
| Operating Supply Voltage | 2.7 V to 5.5 V |
| Operating Temperature | -40 C to +85 C |
| Package | 8-pin SOIC, 0.154 inch body width, 3.90 mm |
| Mounting Type | Surface mount |
| Month-End Adjustment | Automatic for months with fewer than 31 days |
| Manufacturer Document Revision | DS1338-DS1338Z data sheet, Rev.10, 04/27/2015 |
DS1338Z-3+T&R 8-pin soic, 0.154 inch body width, 3.90 mm Pin Configuration Guide
Pin configuration for DS1338Z-3+T&R (8-pin soic, 0.154 inch body width, 3.90 mm package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for DS1338Z-3+T&R.
Refer to the datasheet for full pin configuration.
Typical Applications
DS1338Z-3+T&R is suitable for 6 applications: Industrial Data Loggers, Building Automation Controllers, Medical Monitoring Equipment, Security and Access Systems, Networked Sensor Hubs, Compact Consumer and IoT Controllers.
Industrial Data Loggers
The DS1338Z-3+T&R fits industrial data loggers that must timestamp measurements even when the main controller restarts. Its I2C clock/calendar provides seconds, minutes, hours, day, date, month, and year, while the 56-byte NV RAM can retain compact configuration or diagnostic values. Operating from 2.7 V to 5.5 V supports both 3.3 V and 5 V embedded rails, and the -40 C to +85 C range suits many factory environments. The host processor reads and updates the clock through the shared two-wire interface, reducing the need to maintain calendar logic in firmware.
Recommended
Building Automation Controllers
The DS1338Z-3+T&R is suitable for building automation controllers that maintain schedules and event timestamps for lighting, HVAC, access, and occupancy equipment. The full BCD clock/calendar automatically recognizes month-end boundaries, while the I2C interface allows a controller to query or synchronize time without occupying multiple parallel lines. Its 56-byte NV RAM can preserve a small configuration block across resets. The verified 2.7 V to 5.5 V supply range is useful for low-voltage controller boards, although backup-battery operation must be confirmed from the manufacturer data.
Recommended
Medical Monitoring Equipment
The DS1338Z-3+T&R can provide timestamp and small retained-record support for medical monitoring equipment where event time must remain traceable across controller resets. Its I2C register interface keeps the connection compact, and its 56-byte NV RAM supports a limited amount of calibration or session metadata without a separate nonvolatile memory IC. The stated -40 C to +85 C industrial temperature range supports controlled equipment environments. Medical-system designers must still verify backup behavior, accuracy, regulatory requirements, and the suitability of the complete power architecture for their intended use.
Recommended
Security and Access Systems
The DS1338Z-3+T&R is appropriate for access-control panels, alarm controllers, and security equipment requiring a persistent wall-clock reference. Firmware can attach an event time to access attempts or sensor alarms through the I2C clock/calendar, while the 56-byte NV RAM can retain limited device counters or configuration values. Automatic month-end date handling avoids manual correction for months with fewer than 31 days. Because security systems frequently rely on battery backup, the final design must confirm the target's supported backup arrangement and the accuracy of the internal oscillator under the expected temperature range.
Recommended
Networked Sensor Hubs
The DS1338Z-3+T&R can supply synchronized timestamps for networked sensor hubs that combine measurements from several remote nodes. Using I2C allows the RTC to share the bus with environmental sensors or interface expanders, reducing wiring complexity. The 56-byte NV RAM can hold limited synchronization or configuration information, and the automatic calendar update supports long-duration deployments. The device's 2.7 V to 5.5 V operating range aligns with common low-power embedded systems. Designers should verify address compatibility, bus pull-ups, and oscillator accuracy against the hub's synchronization requirements.
Recommended
Compact Consumer and IoT Controllers
The DS1338Z-3+T&R fits compact IoT controllers that need scheduling, event logging, or a stable timestamp without dedicating a high-power processor to continuous calendar management. The device operates from 2.7 V to 5.5 V, making it suitable for 3.3 V systems, and its I2C interface limits the connection to the address and data lines. The 56 bytes of NV RAM provide limited retained state, while the -40 C to +85 C range supports many indoor and industrial-connected products. Firmware must avoid bus conflicts and verify the supported backup-supply configuration before deployment.
Recommended
Recommended Products Summary
Engineering reference data for DS1338Z-3+T&R — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | DS1338Z-33+T&R | DS1338Z-3+ | DS1340Z-18+ | DS1340Z-33+ | FRTC1338S | PT7C433833WEX |
|---|---|---|---|---|---|---|---|
| Package | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | NYFEA | Maxim Integrated |
| Device Type | I2C RTC with 56-byte NV RAM | I2C RTC with 56-byte NV RAM | I2C RTC with 56-byte NV RAM | I2C RTC with trickle charger and oscillator STOP flag | I2C RTC with trickle charger and oscillator STOP flag | Pin-to-pin functionally compatible RTC | Pin-to-pin functionally compatible RTC |
| Interface | I2C, 2-wire serial | I2C, serial | I2C, serial | I2C | I2C | Pin-to-pin functionally compatible | Pin-to-pin functionally compatible |
Key Differentiators
- Combines real-time clock and retained storage (vs PT7C433833WEX)
- Wider verified supply range than the cross-brand FRTC1338S (vs FRTC1338S)
- Simpler feature set for standard timestamp-only designs (vs DS1340Z-18+)
- Direct family match with identical core resource (vs DS1338Z-33+T&R)
Design Notes
Design the power path around the verified 2.7 V to 5.5 V operating range and confirm the manufacturer-supported backup arrangement before finalizing the schematic. The supplied sources do not identify the backup pin treatment, minimum backup voltage, or capacitor recommendations, so those values must come from the DS1338-DS1338Z data sheet. Avoid inferring a battery configuration from the presence of NV RAM alone.
Place the DS1338Z-3+T&R close to the circuit components required by the manufacturer layout guidance, especially any crystal or oscillator and associated load components. Keep the I2C traces short, provide the required bus pull-ups, and route them away from high-current switching nodes. Because the supplied web snippets do not include the reference layout or pin assignments, use the official Revision 10 data sheet for exact placement and grounding.
Do not assume that an 8-pin SOIC competitor is interchangeable merely because its outline matches. Confirm the I2C device address, time and calendar register mapping, RAM behavior, voltage limits, oscillator accuracy, and power-loss behavior. In particular, DS1340Z variants add a trickle-charge function and oscillator STOP flag, while FRTC1338S lists different supply choices; those differences can affect firmware and board-level power design.
Treat the I2C connection as a shared resource and verify address uniqueness, pull-up resistance, bus capacitance, and rise-time behavior with all connected peripherals present. A pull-up value that works with one sensor may over-degrade the bus when the DS1338Z-3+T&R and other devices are added. Test worst-case bus length, supply voltage, and temperature, and use the manufacturer's timing specifications for the actual operating frequency.
Compliance Information
The supplied verified product information does not explicitly state RoHS, REACH, lead-free, halogen-free, or conflict-mineral status. AEC-Q100 is not applicable because the DS1338 is an RTC and clock/calendar IC rather than an automotive-qualified device category.
