DS1338U-3+ - Low-Power I2C RTC with 56B NV RAM | Analog Devices
料号： DS1338U-3+ ✓ 量产中DS1338U-3+ 概述
A real-time clock is a clock-and-timing IC that maintains time independently of the system processor and can preserve calendar or configuration data across power interruptions. The DS1338U-3+ combines an RTC timebase with 56 bytes of NV SRAM, making it useful for embedded systems that need both timestamping and small quantities of retained data. Its low-power design suits battery-backed equipment where continued timekeeping is required while the main supply is absent.
The verified manufacturer description identifies the DS1338 series as a full BCD clock/calendar with serial I2C access. The clock/calendar information includes seconds, minutes, hours, day, date, month, and year, while the end-of-month date is automatically adjusted for shorter months. The -3+ ordering suffix is associated with the 2.7 V device variant in the distributor data; exact electrical limits not present in the supplied source snippets are marked as data needed rather than inferred.
Typical uses include industrial controllers, data loggers, meters, embedded instruments, and battery-powered systems that require an independent time reference. The I2C interface allows the host processor to read or write clock registers and access the NV SRAM without dedicating multiple parallel pins. Designers should preserve the device-specific pinout and verify voltage, current, oscillator, accuracy, and retention specifications against the manufacturer datasheet before releasing a production design.
A key design consideration is matching the RTC supply architecture to the system power source. If the device is intended to maintain time during a main-power interruption, the backup supply and current-consumption requirements must be designed together with the load switch and battery path. The host firmware should also account for I2C address configuration and calendar rollover behavior.
This page combines verified distributor and manufacturer information, structured specifications, application guidance, design notes, and only the drop-in alternatives supported by the supplied cross-reference data. It is intended to help engineers evaluate the DS1338U-3+ for embedded timing and nonvolatile data-retention designs while avoiding unsupported assumptions.
直接替换替代料： DS1338U-3+ ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： DS1338U-3+ （相同外形与封装尺寸） ——差异在于 Package, Package Width, RoHS Status.
DS1338U-3
✅ 直接替换📋 参考替代料（不在目录中）
DS1338U-33+
✅ 直接替换📋 参考替代料（不在目录中）
DS1308U-3+
✅ 直接替换📋 参考替代料（不在目录中）
DS1338C-3#
✅ 直接替换联系询价
查看数据手册 →DS1340U-33+
✅ 直接替换📋 参考替代料（不在目录中）
DS1338U-3+ 规格参数
| Product Type | Serial real-time clock (RTC) with clock/calendar and NV SRAM |
| Manufacturer | Analog Devices Inc./Maxim Integrated |
| 接口 | I2C serial interface |
| Calendar Encoding | Full BCD |
| Calendar Fields | Seconds, minutes, hours, day, date, month, year |
| End-of-Month Adjustment | Automatic adjustment for months with fewer than 31 days |
| Nonvolatile SRAM | 56 bytes |
| 封装 | 8-pin µMAX/TSSOP-style package |
| Terminal Count | 8 terminals |
| Package Width | 3.00 mm |
| Package Length | 0.118 in |
| Terminal Form | Gull wing |
| Temperature Grade | Industrial |
| RoHS 状态 | unknown |
| REACH Status | unknown |
| AEC-Q100 Qualification | not_applicable |
| Lead-Free Status | unknown |
| Halogen-Free Status | unknown |
DS1338U-3+ 0.118 in 引脚配置指南
DS1338U-3+（0.118 in 封装）的引脚配置。 引脚编号、功能和连接图在制造商数据手册中定义。请参阅该手册以了解确切的封装尺寸和焊接指南。
暂无详细引脚数据： DS1338U-3+.
请参阅 数据手册 以查看完整引脚配置。
典型应用
DS1338U-3+ 适用于 7 应用s: Battery-Backed Industrial Data Logger, Embedded Measurement Instrument, Battery-Powered Sensor Node, Embedded Controller Timebase, Data Acquisition and Event Ordering, Compact Access-Control and Security Controller, Portable Medical or Diagnostic Equipment.
Battery-Backed Industrial Data Logger
The DS1338U-3+ fits a battery-backed data logger because it combines a dedicated BCD clock/calendar with 56 bytes of NV SRAM. The host controller can timestamp records through the I2C interface and retain a small configuration block across a power interruption. This is useful when the main supply is absent but the product still needs event ordering. The exact backup current, retention duration, and operating voltage must be taken from the manufacturer datasheet before sizing the battery and load switch.
推荐
Embedded Measurement Instrument
The DS1338U-3+ can provide time stamps for meters, test equipment, and compact measurement instruments. Its seconds-through-year calendar fields support event ordering, while the 56-byte NV SRAM can retain a small calibration identifier, instrument counter, or operating mode setting. The RTC keeps time independently of the main controller, allowing the system to present a valid timestamp even after a reset. Verify the exact I2C address and register access sequence in the manufacturer documentation.
推荐
Battery-Powered Sensor Node
The DS1338U-3+ is a useful timing companion for a low-power sensor node that must preserve event order during intermittent operation. The 56-byte NV area can hold a small status record, while the BCD calendar provides human-readable time fields to the host processor. The device does not eliminate the need for low-power firmware: the controller should wake periodically, read the RTC, and return to sleep. Supply current and oscillator accuracy are not present in the supplied sources and must be verified before battery-life estimation.
推荐
Embedded Controller Timebase
The DS1338U-3+ gives an embedded controller a dedicated, low-power calendar source instead of relying on software timing tied to the processor. The host reads seconds, minutes, hours, date, month, and year over I2C, while the RTC’s automatic shorter-month handling reduces calendar logic. This arrangement is useful in controllers that sleep between tasks but must preserve a consistent time base. The final firmware should handle rollover and invalid-clock conditions according to the manufacturer register definitions.
推荐
Data Acquisition and Event Ordering
The DS1338U-3+ can annotate acquisition records with calendar time while the 56-byte NV SRAM stores limited persistent context. In a data-acquisition product, this helps distinguish events that occur after a controller reset or power cycle. The two-wire interface conserves package pins and is suitable for sharing with other I2C peripherals, although the complete bus loading and pull-up design must follow the selected system topology. Confirm the package footprint and pin numbering before placing the device beside the controller.
推荐
Compact Access-Control and Security Controller
The DS1338U-3+ can support timestamped access events in a compact access-control or security controller. Its clock/calendar gives the host an independent event time, and the small NV SRAM can retain a limited device counter or configuration record. This use case is attractive when the controller must retain time through a short power interruption without dedicating a separate nonvolatile storage device for small amounts of data. Do not use the 56-byte SRAM as the sole security credential store; protect access to the I2C bus and validate the system’s tamper-resistance requirements.
推荐
Portable Medical or Diagnostic Equipment
The DS1338U-3+ can provide persistent timestamps for portable diagnostic equipment that records events or device sessions. The RTC separates timekeeping from the main processor, while the 56-byte NV SRAM can hold a limited operating counter or configuration marker. Because the supplied data does not provide medical qualification, battery current, or reliability figures, this application requires a separate system-level compliance review. Confirm electrical limits and the exact package before using the part in a regulated design.
推荐
推荐产品汇总
工程参考数据： DS1338U-3+ ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | DS1338U-3 | DS1338U-33+ | DS1308U-3+ | DS1338C-3# | DS1340U-33+ |
|---|---|---|---|---|---|---|
| Function | I2C real-time clock/calendar with 56 bytes NV SRAM | Related DS1338U RTC; exact suffix differences require verification | Related DS1338U RTC; exact suffix differences require verification | Related low-current I2C RTC with 56-byte memory description | DS1338 family comparison candidate | Related RTC candidate; exact equivalence unverified |
关键差异点
- Integrated calendar and persistent small data store （对比 DS1308U-3+)
- Calendar month-length handling （对比 DS1338U-33+)
- Two-wire serialized access （对比 DS1338C-3#)
设计说明
Design the DS1338U-3+ supply and backup path together with the system load switch. The verified sources identify the part as a low-power RTC but do not provide supply current, standby current, or backup-source limits. Confirm those values in the manufacturer datasheet, then verify that pull-ups and other connected peripherals do not defeat the intended low-power state. Use the exact recommended capacitor and backup-battery configuration rather than deriving a battery budget from the RTC function alone.
Place the DS1338U-3+ close to the controller and route the I2C signals as a compact two-wire bus. Keep the package footprint and pin numbering aligned with the official 8-pin package drawing; the supplied snippets do not provide the complete pin map. Check pull-up placement so the bus remains usable during low-power states and does not create excessive leakage from the RTC supply. Confirm the selected package variant before releasing the PCB footprint.
Do not treat a related DS1338U or DS1340U ordering suffix as proof of interchangeability. Before replacing DS1338U-3+, compare supply range, I2C address, clock-register map, NV SRAM behavior, package markings, temperature grade, and oscillator requirements. The supplied search results identify several comparison candidates but do not provide a complete manufacturer cross-reference. A successful prototype should not be treated as production equivalence without this full verification.
Keep the RTC timebase and its required support components away from noisy switching nodes, high-current return paths, and sources of strong electromagnetic coupling. Follow the manufacturer reference circuit for the timebase and decoupling, because the supplied data does not specify the oscillator topology or required loading. Provide a stable ground reference and avoid routing sensitive I2C traces parallel to long power-switching edges. Validate signal integrity with the final bus topology and load conditions.
Treat the DS1338U-3+ I2C bus as a shared two-wire resource. Account for pull-up voltage, bus capacitance, speed, peripheral address conflicts, and the controller’s sleep or reset state. The verified sources identify I2C address and data transfer but do not provide the address or timing values; obtain those from the manufacturer documentation. Add bus-contention or brownout testing when the RTC must remain available during power transitions.
合规信息
The supplied manufacturer and distributor snippets do not state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-mineral status. These fields remain unknown rather than inferred.
