Analog Devices Inc./Maxim Integrated DS1315S-33+

Overview

DS1315S-33+ from Maxim Integrated is a real-time clock (RTC) and nonvolatile SRAM controller IC combining timekeeping (hundredths of seconds to years, with leap-year correction through 2100) and battery-backed memory control in a single 16-pin SOIC package. It operates at +3.3V, supports dual battery inputs (BAT1/BAT2), and interfaces with external CMOS SRAM or ROM without address-space gaps.

For engineers reviewing the DS1315S-33+ datasheet, DS1315S-33+ pinout, DS1315S-33+ application, or DS1315S-33+ equivalent, key selection criteria include its pattern-based serial access protocol, VCCO switched supply output for SRAM backup, power-fail detection with CEO-driven write protection, and industrial-grade temperature support when ordered as SN variant.

Technical Context

The DS1315S-33+ implements a 64-bit serial pattern recognition protocol (C5h, 3Ah, A3h, 5Ch repeated) to gate access to time registers-prior to match, all CEI/OE/WE activity routes to external memory via CEO; after match, CEO goes high to isolate memory and enable RTC register read/write. Time data is stored in eight BCD-encoded registers accessed sequentially bit-by-bit.

Its nonvolatile controller dynamically selects between RAM mode (ROM/RAM = GND) and ROM mode (ROM/RAM = VCCO): in RAM mode, it supplies VCCO (VCCI − 0.3V max drop) to back up SRAM and performs automatic redundant battery switchover; in ROM mode, CEO asserts low on power fail while retaining internal RTC write protection.

Key Specifications

Pinout & Package

DS1315S-33+ is housed in a 16-pin Small Outline (SO) package, 300 mils wide, RoHS-compliant (indicated by '+' suffix). Pin 1 is VCC1; pins 9–16 follow standard SOIC numbering with X1/X2 on pins 9/10 and dual ground pins (7 and 16).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock and nonvolatile memory controller applications.

Compared with DS1315S-33+, both alternatives omit the patented 64-bit pattern access protocol, lack VCCO-regulated SRAM backup, and provide no automatic BAT1/BAT2 voltage arbitration-making DS1315S-33+ uniquely suited for high-integrity, long-duration data logging where memory retention and time accuracy must survive multiple power-loss events.

Availability

DS1315S-33+ is available at Aetrix Electronics and suitable for industrial data loggers, medical device timestamping, point-of-sale terminals, network infrastructure diagnostics, and embedded instrumentation requiring stable component supply with long-term lifecycle assurance.

Supply support for DS1315S-33+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated, now part of Analog Devices, designs precision analog, mixed-signal, and digital ICs for industrial, communications, computing, and consumer applications.

The DS1315S-33+ belongs to Maxim's Phantom Time Chip family, engineered specifically to unify high-accuracy RTC functionality with autonomous nonvolatile SRAM control-enabling zero-software-overhead time stamping and guaranteed data retention in power-constrained systems.

FAQ

What is the primary function of the DS1315S-33+?

The DS1315S-33+ is a combined real-time clock and nonvolatile SRAM controller IC. It maintains accurate time (hundredths of seconds through years with leap-year correction to 2100) while providing battery-backed power switching and write protection for external CMOS SRAM. Its core value lies in eliminating firmware dependency for timekeeping and memory retention during power loss.

How does the DS1315S-33+ interface with external memory?

The DS1315S-33+ uses a serial pattern recognition protocol-not address/data bus-to access its internal time registers. External memory connects directly to CEO, CEI, OE, WE, D, and Q pins. During normal operation, CEO passes through CEI to enable memory; after 64-bit pattern match, CEO goes high to isolate memory and route subsequent cycles to the RTC registers.

Does the DS1315S-33+ support dual battery backup?

Yes, the DS1315S-33+ supports dual battery inputs (BAT1 and BAT2) and automatically selects the higher-voltage source to drive VCCO in RAM mode. This redundancy ensures uninterrupted SRAM backup even if one battery fails, making it ideal for high-reliability applications like industrial loggers and medical devices where data integrity is critical.

What is the purpose of the VCCO pin on the DS1315S-33+?

VCCO is the switched supply output pin that delivers VCCI − 0.3V (max drop) to external SRAM during main power failure. It enables seamless transition from VCC-powered operation to battery-backed SRAM retention without voltage droop or reset. This regulated output is central to the DS1315S-33+'s role as a nonvolatile memory controller-not just an RTC.

Can the DS1315S-33+ operate with a 5V supply?

No, the DS1315S-33+ is rated exclusively for +3.3V ±10% operation. For 5V systems, the pin-compatible DS1315-5+ or DS1315N-5+ variants must be used. The "33" in DS1315S-33+ explicitly denotes 3.3V operation, and applying 5V to DS1315S-33+ exceeds its absolute maximum ratings and will cause permanent damage.