Maxim time clock
The PowerCap top, containing the heat-sensitive battery and crystal, is snapped onto the base after soldering. The module base, containing the RAM and clock, is mounted to the board using standard reflow techniques. PowerCap products use a two-piece construction to provide a device that can be surface-mounted using the reflow process. Modules can also be attached to the PCB using wavesolder, as long as the lithium battery is not exposed to temperatures above +85☌. Consequently, modules can be attached manually or inserted in a socket after reflow. However, crystals and batteries cannot tolerate the temperatures encountered during the reflow process. Modules include an embedded 32,768Hz crystal and a lithium battery, making PCB design easier. Timekeeping NV RAMs, mux-bus clocks, and some watchdog and phantom clocks are available in module and/or PowerCap packages. Other timekeeping NV RAM modules are monolithic (controller and SRAM in one IC) and require no freshness seal. This function is often called "freshness seal," and is used to conserve the battery until the module is first used. The battery will be connected to the SRAM after V CC is removed for the first time. The oscillator is disabled and the SRAM is electrically disconnected from the battery when shipped from the factory. Some timekeeping NV RAM modules use a clock-controller IC and a SRAM. While the oscillator is disabled, the battery current is less than the self-discharge of the battery, or about 0.5% per year at room temperature. All clock modules with embedded crystals and batteries are shipped from the factory with the oscillator disabled. The majority of the current consumed by a clock while in battery-backed mode is from the oscillator. Water washing will short the battery terminals, and therefore drain the batteries.Ĭlock Modules, Freshness Seal and Shelf Life Packages that include the battery and have exposed battery pins, such as the SmartSockets, should never be water washed. The battery should never be exposed to temperatures above +85☌. Lithium batteries are normally rated to operate from -40☌ to +85☌. Regulatory agency data and Conditions of Acceptability information can be found at UL Recognition. Most Maxim products that include a battery input pin include on-chip reverse charging protection circuitry. When the end user first powers the system, the firmware/software should start the oscillator and prompt the user for the time and date. It also allows the system designer to set up a manufacturing flow so that no battery current is drawn after a fresh lithium battery is installed. This conserves the battery until the system is powered up.
![maxim time clock maxim time clock](https://i.ebayimg.com/images/g/FOcAAOSwDtRetd34/s-l640.jpg)
In almost all clocks with this bit, it is preferable that the oscillator be off when the battery is initially attached.
![maxim time clock maxim time clock](https://www.bobswatches.com/rolex-blog/wp-content/uploads/2018/05/Rolex_GMTII_16710_20JM5068-Edit-2-1-1024x683.jpg)
This bit is usually located in bit 7 of the seconds register, or in a control register. Many clocks include an oscillator control bit, usually called the clock halt (CH) or enable oscillator (EOSC) bit. The V CC voltage level at which communications is locked out is usually defined in the data sheet as V TP (Trip Point Voltage). Communications between the microprocessor and the RTC are usually locked out (often called write protect) to keep the battery current at a minimum and to prevent data corruption. In this situation the RTC will switch its internal supply bus to the battery and go into a low-power mode. If a primary battery, such as a lithium coin cell, is used for backup, the RTC should be designed to draw as little power as possible when running from the battery. In this case, the RTC must be able to switch between the two power supplies. To keep the clock oscillator running, a primary or secondary battery or a super capacitor may be used. Other applications require that the time and date remain valid even if the main power supply is off. In some applications such as VCRs, the time and date information will be lost if power is removed. A phantom clock can therefore provide time and date information without using any memory space.
#Maxim time clock software#
Finally, phantom clocks "hide" behind battery-backed RAM and use a 64-bit software protocol to gain access to the clock. Timekeeping NV RAMs use the same control signals as SRAMs, to which many processors provide an easy interface, and include battery-backed RAM in various densities. Others, such as 8051 processors and their derivatives, support multiplexed address and data buses. Many processors include I☬ or SPI interfaces.
![maxim time clock maxim time clock](https://n3.sdlcdn.com/imgs/c/l/3/The-Maxim-Square-Digital-Wall-SDL576303826-1-25eca.jpg)
The choice of interface is often determined by the type of processor being used. Parallel interfaces include mux-bus (multiplexed data and address bus) and designs with separate address and bytewide data inputs.
#Maxim time clock serial#
Serial interfaces include I☬, 3-wire, and Serial Peripheral Interface (SPI). Real-time clocks (RTCs) are available in a wide range of bus interfaces.