Product Brief
Microchip offers stand-alone, real-time clock/calendar family
Rick DeMeis11/9/2010 1:12 AM EST
Microchip Technology has announced availability of its first stand-alone I2CTM real-time clock/calendar (RTCC) family. The six MCP794XX devices (video interview below) include on-chip SRAM (64 Bytes) and can include EEPROM (1 kbits).
Also featured are digital trimming for time-of-day calibration and a battery switchover function that supports backup power at low voltage and current levels. Such integration in a single device lower parts count and cost ($0.64/0.70/0.76 each in 10k quantities).
Applications include automotive (i.e. dashboard controls, radio), smart energy (i.e. thermostats, power meters, and commercial refrigeration), appliances (i.e. stoves, dishwashers, microwave ovens), and commercial and consumer electronics (i.e. office equipment, irrigation controls, and video systems).
Devices such as cameras and notebook computers require a real-time clock with back up to maintain time and alarm settings when their power is turned off. Commercial refrigeration, point-of-sale, and security systems need such functionality with a power-fail monitor to capture and store "timeframes" when main power fails. The on-chip battery switchover circuit and power-fail timestamp on the MCP794XX RTCCs provide these capabilities. Digital trimming supports software temperature compensation, which lowers cost compared to devices where compensation is done in hardware. The devices function over industrial temperatures from -40 to 85C.
RTCC development support includes a daughter board (available in Q1 2011) that is compatible with various Microchip development boards.
For product information and data sheets, click here.
Applications include automotive (i.e. dashboard controls, radio), smart energy (i.e. thermostats, power meters, and commercial refrigeration), appliances (i.e. stoves, dishwashers, microwave ovens), and commercial and consumer electronics (i.e. office equipment, irrigation controls, and video systems).
RTCC development support includes a daughter board (available in Q1 2011) that is compatible with various Microchip development boards.
For product information and data sheets, click here.
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Rick DeMeis
11/9/2010 1:47 AM EST
I was pre-briefed on these at ESC Boston. What's impressive are the features for the price, along with temperature compensation in software over the industrial temperature range.
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t.alex
11/9/2010 2:57 AM EST
cool device. Just have a thought .. isn't nicer if the 32.768Khz crystal can be integrated into the IC?
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powerlifter
11/9/2010 4:14 PM EST
Integrated crystals in real-time clocks often drift in frequency, when exposed to the high reflow-soldering temperatures. For this reason, many designers prefer to utilize external crystals and capacitors. If, however, designers prefer an integrated crystal and require higher accuracy, there are real-time clocks with an integrated hardware-compensation circuit to keep the clock calibrated across a wide temperature range. Since these crystal-integrated RTCs with compensation circuits are much more expensive—on average, about 4x the price of Microchip’s RTC— the system requirements usually dictate this selection.
-Alex Martinez,
Product Marketing Manager,
Microchip Technology Inc.
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t.alex
11/10/2010 12:39 AM EST
Yep, it is quite true using internal oscillator is a bad idea due to huge drifting. Btw, for the IC above, is it possible to supply a clock source instead of fixed 32768 crystal? It is good if we can reuse some output clock from a microcontroller instead of maintaining 2 crystals on the board.
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Jagdish Bisawa
11/10/2010 1:04 AM EST
Alex, that might not be a good idea, again, due to slight drifts in the external clock that is derived from a microcontroller. Such a solution might lead to inaccuracies in real-time estimation that can accumulated over a period of time.
Also, what would happen if the device has to switched to a low power/battery mode ?
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powerlifter
11/10/2010 6:08 PM EST
This device can operate from a crystal or external clock source, but in battery backup mode only the crystal would be operational. If you really need to reduce the number of crystals, you could also use the 32.768 KHz clock output in the RTCC as a second clock source. When considering this option, make sure your system requirements do not require an alarm output from the RTCC.
-Alex Martinez,
Product Marketing Manager,
Microchip Technology Inc.
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