DS1338U-33/T&R - 56B I2C RTC | Analog Devices
部品番号: DS1338U-33/T&R ✓ 生産中DS1338U-33/T&R 概要
A real-time clock is a clock-and-timing integrated circuit that preserves time independently of a host processor and system clock. In the component hierarchy, an RTC is a timing IC, a clock-and-calendar device, and ultimately a semiconductor designed for timekeeping and data retention. Unlike a microcontroller timer, the DS1338U can continue maintaining calendar time from a backup source when the main system supply is unavailable, subject to the application backup circuit.
The principal feature is 56 bytes of battery-backed nonvolatile SRAM alongside the calendar registers. Address and data move serially through the two-wire I2C interface, allowing a host microcontroller to read or update time and retain small quantities of configuration or operational data. The device includes automatic end-of-month correction, as stated on the Analog Devices product page, reducing host software complexity. A square-wave output provides a periodic reference that can support system timing, alarms, or periodic interrupts when the host schedules an interrupt.
The DS1338U is designed for low-power embedded systems that require accurate wall-clock time and a small amount of persistent storage. Its I2C interface reduces the number of connections compared with a parallel RTC, making it suitable for compact controller boards. The -33 configuration is useful where a 3.3 V system is prominent, while the documented 3 V to 5.5 V supply range provides flexibility across industrial and embedded equipment operating from compatible rails. Exact oscillator accuracy and current-consumption figures are not present in the supplied source data and therefore require confirmation in the manufacturer datasheet.
Typical uses include industrial controllers, embedded instruments, data-acquisition systems, access-control terminals, and compact communications equipment. Its calendar and persistent-memory functions can record operating events without repeatedly writing nonvolatile data to flash. In designs where wall-clock continuity matters, the backup-supply architecture should be implemented and tested independently of the main 3.3 V rail rather than assuming that a backup capacitor alone meets every retention requirement.
PCB design should preserve the I2C signal integrity by keeping SDA and SCL routing short, using continuous ground references, and avoiding long stubs between the DS1338U and its host. Place required input and backup capacitors close to their associated pins. Verify the oscillator crystal or resonator connection against the manufacturer reference layout, because incorrect loading or excessive trace length can affect time accuracy. The uSOP-8 footprint is compact, but exposed-pad-free implementations still require adequate copper for stable electrical and thermal behavior.
This page combines the verified manufacturer description, distributor package and ordering information, documented supply and temperature limits, and cross-reference results for the DS1338 family. It also distinguishes true pin-compatible candidates from parts with different packages or added functions, providing practical guidance for RTC selection, replacement, sourcing, and circuit integration.
ドロップイン代替品: DS1338U-33/T&R — 同一パッケージでピン互換。PCBの作り直しが必要な異なるパッケージの部品は除外されています。
このシリーズのバリエーション
同一シリーズでドロップイン互換のモデル: DS1338U-33/T&R （同一形状・フットプリント） — 相違点: Product Type, RoHS Status, Serial Interface.
DS1338U-33+
✅ ドロップイン価格はお問い合わせください
データシートを見る →DS1338U-18+T&R
✅ ドロップイン価格はお問い合わせください
データシートを見る →DS1340U-33+T&R
✅ ドロップイン📋 参考代替品（カタログ未掲載）
DS1338U-33/T&R 仕様
| Product Type | Serial real-time clock (RTC) with nonvolatile RAM |
| Timekeeping Format | Full binary-coded decimal (BCD) |
| Serial Interface | I2C, 2-wire serial |
| Nonvolatile Memory | 56 bytes |
| Supply Voltage Range | 3 V to 5.5 V |
| Nominal Configuration | 3.3 V |
| 動作温度範囲 | -40°C to +85°C |
| パッケージ | 8-pin uSOP, 3.00 mm width |
| Package Pins | 8 pins |
| 実装タイプ | Surface mount |
| Calendar Information | Seconds, minutes, hours, day, date, month, and year |
| End-of-Month Adjustment | Automatic |
| Backup Supply | Dedicated backup battery input |
| RoHS ステータス | Compliant |
| AEC-Q100 Qualification | Not applicable |
DS1338U-33/T&R ピン構成
| ピン 1 | SDA — Serial data input/output for the I2C interface |
| ピン 2 | SCL — Serial clock input for the I2C interface |
| ピン 3 | VCC — Primary supply input |
| ピン 4 | VBACKUP — Backup supply input |
| ピン 5 | GND — Ground connection |
| ピン 6 | X1 — Crystal or oscillator input |
| ピン 7 | X2 — Crystal or oscillator output |
| ピン 8 | SQW/OUT — Square-wave or alarm output |
主な用途
DS1338U-33/T&R の用途: 6 件s: Industrial Data-Acquisition Controller, Embedded Instrumentation, Communications Equipment, Access-Control and Security Terminal, Battery-Powered Sensor Node, Consumer Appliance Control.
Industrial Data-Acquisition Controller
The DS1338U-33/T&R fits industrial data-acquisition equipment that must retain a wall-clock timestamp and small event records across a main-power interruption. Its 56-byte nonvolatile SRAM provides a practical place for counters, calibration markers, or operating state without continuous flash writes, while the I2C interface lets the host controller access the data serially. The documented 3 V to 5.5 V supply range supports common embedded rails, and the -40°C to +85°C rating covers many industrial environments. Place the device on the same controller board as the acquisition processor, route SDA and SCL away from high-current switching nodes, and validate the backup network under the worst expected load. Its advantage over DS1340U-33+T&R is functional simplicity, since DS1338U does not add the DS1340U trickle-charger function.
おすすめ
Embedded Instrumentation
The DS1338U-33/T&R is appropriate for embedded test and measurement instruments where displayed records need real calendar dates rather than an elapsed-time counter. The RTC maintains seconds, minutes, hours, day, date, month, and year in BCD form, and automatically adjusts the end-of-month date according to the Analog Devices product description. Its 56-byte nonvolatile RAM can preserve a short operating-state record while the I2C host reads and updates it. With an operating range of 3 V to 5.5 V, the device can share a 3.3 V control rail. Designers should use the manufacturer reference layout for oscillator and bypass connections and should not treat the backup path as guaranteed until retention under worst-case conditions has been tested.
おすすめ
Communications Equipment
The DS1338U-33/T&R can support communications equipment that requires timestamps for message delivery, maintenance logs, or configuration changes. The two-wire I2C connection limits bus usage compared with a parallel calendar device, leaving more host-controller I/O available for communications and status functions. Its 56-byte nonvolatile memory can hold compact counters or node-state information, although it is not intended as a substitute for a large nonvolatile data store. The 3.3 V-oriented DS1338U-33 configuration aligns with many communication modules. Place pull-up resistors in accordance with the manufacturer interface guidance, keep the I2C traces short, and isolate clocks and switching supplies to avoid introducing digital noise into the RTC and its backup supply.
おすすめ
Access-Control and Security Terminal
The DS1338U-33/T&R is useful in access-control terminals that need event timing and a small amount of persistent state. The RTC's full BCD calendar supplies date and time fields, while 56 bytes of nonvolatile storage can retain a limited transaction or service-state record. The I2C interface simplifies integration with a host processor and helps limit connector count in compact terminals. The -40°C to +85°C operating range and 3 V to 5.5 V supply span suit many indoor and industrial-enclosure implementations. For security-sensitive systems, engineers should authenticate or protect stored event data independently, maintain a defined backup-power budget, and verify oscillator behavior across the full product temperature range rather than relying only on nominal timing accuracy.
おすすめ
Battery-Powered Sensor Node
The DS1338U-33/T&R can support battery-powered sensor nodes that need timekeeping after a power interruption or during reduced-energy operation. The 3 V to 5.5 V operating range includes common 3.3 V sensor-node rails, and the I2C interface limits the connection burden on a microcontroller constrained by board area. The 56-byte nonvolatile RAM offers space for a limited synchronization timestamp or operating flag. Because the verified excerpts do not provide active current, backup current, or oscillator-accuracy figures, battery sizing must use the current manufacturer datasheet rather than nominal assumptions. During schematic design, define exactly what state must survive, estimate the worst backup load, and verify whether the chosen backup source can maintain the required retention interval.
おすすめ
Consumer Appliance Control
The DS1338U-33/T&R fits compact consumer appliances that log operating events, schedule service intervals, or display the correct date and time. Its low-power serial design avoids a parallel RTC bus, and its 56-byte nonvolatile memory can hold small counters without wearing a flash-based nonvolatile memory through frequent updates. The device operates across 3 V to 5.5 V and uses an 8-pin uSOP package, supporting compact controller layouts. Compared with DS1338U-18+T&R, the -33 configuration is the more natural match for a 3.3 V logic rail. Compared with DS1340U-33+T&R, it avoids an unnecessary trickle charger if the appliance does not require managed battery charging. Layout and firmware should still include oscillator, bypass, and backup checks that go beyond basic power-up functionality.
おすすめ
おすすめ製品の概要
エンジニアリング参考データ: DS1338U-33/T&R — 比較、設計ガイダンス、コンプライアンス情報。
選定ガイド
代替品との比較
| パラメータ | この製品 | DS1338U-33+ | DS1338U-18+T&R | DS1340U-33+T&R |
|---|---|---|---|---|
| Package | uSOP-8 | uSOP-8 - same | uSOP-8 - same | uSOP-8 - same |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Product Type | I2C real-time clock with 56-byte nonvolatile RAM | I2C real-time clock with 56-byte nonvolatile RAM | I2C real-time clock with 56-byte nonvolatile RAM | I2C real-time clock with 56-byte nonvolatile RAM |
| Nominal Voltage Configuration | 3.3 V | 3.3 V | 1.8 V | 3.3 V |
| Supply Voltage Range | 3 V to 5.5 V | 3 V to 5.5 V | 3 V to 5.5 V maximum | 3 V to 5.5 V maximum |
| Nonvolatile Memory | 56 bytes | 56 bytes | 56 bytes | 56 bytes |
| Serial Interface | I2C, 2-wire serial | I2C, 2-wire serial | I2C, 2-wire serial | I2C, 2-wire serial |
| Calendar Features | Full BCD clock/calendar with automatic end-of-month adjustment | Full BCD clock/calendar | Full BCD clock/calendar | Full BCD clock/calendar |
| Backup Features | Backup supply input | Backup supply input | Backup supply input | Backup supply with trickle-charge capability |
| Additional Control Feature | No oscillator STOP flag documented for this option | No oscillator STOP flag documented for this option | No oscillator STOP flag documented for this option | Oscillator STOP flag |
主な差別化要因
- Direct 3.3 V configuration with full same-family functionality （vs DS1338U-18+T&R)
- Simpler backup architecture when managed trickle charging is unnecessary （vs DS1340U-33+T&R)
- Tape-and-reel production ordering （vs DS1338U-33+)
設計ノート
Follow the Analog Devices DS1338U recommended layout for the oscillator, bypass capacitors, I2C connections, and backup supply. Keep SDA and SCL traces short, provide a continuous ground reference, and avoid routing them beside high-current switching nodes. The supplied evidence confirms the uSOP-8 package and I2C function but does not provide the complete land pattern, so the current manufacturer package drawing should control PCB implementation.
Design the VBACKUP path around the data that must survive a main-rail outage. The verified sources confirm a backup supply and 56-byte nonvolatile memory, but they do not provide backup-current, retention-time, or capacitor-sizing limits. Use the manufacturer datasheet to determine permissible backup-source voltage, leakage allowance, and capacitor selection, then test the assembled circuit at maximum expected backup load and temperature rather than relying on nominal capacitance alone.
Do not confuse the -33 suffix with a general 5 V-only part: the verified operating range is 3 V to 5.5 V and the -33 version is intended for a nominal 3.3 V configuration. Also do not substitute DS1338U-18+T&R without reviewing its 1.8 V configuration, and do not select DS1340U-33+T&R merely because it shares the package; its trickle charger and oscillator STOP flag can require different support circuitry and firmware.
コンプライアンス情報
RoHS compliance is identified in the verified cross-reference data for the DS1338U family. The supplied sources do not establish REACH, lead-free, halogen-free, or conflict-minerals status, so those fields remain unknown.
