DS1647P-120

Real Time Clock Overview

The DS1647P-120+ is a nonvolatile timekeeping RAM module integrating 512k x 8 SRAM, a real-time clock (RTC), crystal, and lithium battery backup. It operates within a 0°C to +70°C temperature range using a single 5V supply (4.5V–5.5V). The device features BCD-coded time registers with leap year compensation through 2099. Key electrical parameters include a typical standby current of 3mA (TTL) or 2mA (CMOS), write-protection voltage at 4.0V–4.5V, and address access times of 120ns. The PowerCap package allows surface-mount assembly before attaching the separate battery/crystal module.

Real Time Clock Feature Summary

• Integrates 512k x 8 NV SRAM and RTC in a single byte-wide interface
• Power-fail write protection prevents data corruption during low VCC conditions
• Double-buffered clock registers ensure accurate time reading without halting the internal oscillator
• DS1647P variant uses a separate PowerCap (DS9034PCX+) for battery and crystal, enabling reflow soldering

Real Time Clock Applications

• Industrial systems requiring precise timekeeping and nonvolatile data storage
• Embedded controllers needing battery-backed memory with minimal component count
• Equipment requiring automatic leap year correction and calendar functions

Real Time Clock Procurement Notes

Verify that the DS9034PCX+ or DS9034I-PCX+ PowerCap module is ordered separately, as it is not included with the DS1647P-120+ silicon. Confirm RoHS compliance via the '+' suffix. Ensure the application design accommodates the separate mounting of the PowerCap after the surface mount process to protect the lithium source from reflow temperatures.

Real Time Clock Selection Notes

Select the DS1647P-120+ when surface-mount technology is required for the silicon die, distinguishing it from the 32-pin DIP DS1647-120+. This part is suitable for environments where the battery and crystal must be isolated from high-temperature soldering processes. Ensure the system VCC remains above 4.5V for normal operation and below 4.0V to trigger write protection.

Real Time Clock Part Context

The DS1647P-120+ belongs to the DS164x family of nonvolatile timekeeping RAMs. It is functionally equivalent to standard JEDEC 512k x 8 SRAM but adds integrated timekeeping capabilities in the top eight memory locations. The 'P' designation indicates the PowerCap package configuration, which requires an external companion module for energy storage and clock generation.

Real Time Clock Replacement Considerations

Direct pin-for-pin replacements exist within the DS164x series for different densities (e.g., DS1643, DS1645), though capacity will vary. For the specific PowerCap package, the DS1647P-120+ requires the DS9034PCX+ or DS9034I-PCX+ battery/crystal module. Standard SRAMs cannot replace this device due to the lack of nonvolatility and integrated RTC functionality.