Microchip targets active current reduction in PIC24F expansion - Embedded.com

Microchip targets active current reduction in PIC24F expansion


Microchip has expanded its eXtreme Low Power (XLP) microcontrollers portfolio with the PIC24F ‘GA3’ 16-bit MCU family, which  have 150 microamperes/MHz active current, as well as six DMA channels, which allow a routine to be executed with less power consumption and increased throughput.  With these six additions the PIC24F range now numbers 91 devices.

The family adds a low-power sleep mode with RAM retention down to 330 nA. and the first PIC MCUs with VBAT for battery backup of the on-chip real-time clock calendar.

“The XLP technology has traditionally concentrated on reducing static currents,” according Don Schneider, Product Marketing Manager with the Advanced MCU Division of Microchip Technology Inc., “but with this development we have targeted reducing active current.” With its operating current of 150 microamperes/MHz, numerous low-power modes, and its low-power sleep mode with RAM retention down to 330 nA, the PIC24F ‘GA3’ MCUs enable maximum battery life by reducing the overall amount of power that the application consumes.  

Standard XLP modes include run/idle/doze and sleep/deep sleep. The news devices add a low voltage sleep and VBAT battery backup modes. “We have added an intermediate step between sleep mode and the deep sleep mode which allows the RAM to be maintained and some of the peripherals to be operated at a very low current.”

To allow the application’s real-time clock to continue running when primary power is removed, a VBAT pin can be used to supply back-up power with 400 nA.  Additionally, the transition from VDD to the VBAT supply pin occurs automatically as VDD is removed.  

This is also the first time an integrated LCD display driver has been included in the PIC24F to provide the ability to directly drive up to 480 segments, with an eight-common-drive capability, enabling more informative and flexible displays that include descriptive icons and scrolling. “The LCD driver is a real step up from the 42 segment x 4 we have traditionally provided to a 60 segment x 8 driver,” said Schneider.

The MCUs also include a charge time measurement unit (CTMU) with a constant current source that can be used for mTouch capacitive sensing, ultrasonic flow measurement and many other sensors.   

Click on image to enlarge.

The device also includes up to 24 channels of 12-bit ADC. The ADC includes a threshold detect function that allows the ADC to wake the CPU when a specific threshold of window is reached. The threshold detect function is particularly useful when used with the CTMU in a capacitive touch application. The button or proximity sensor can be monitored while the device is in sleep and can wake when a specific threshold value is reached.

“For the parts that have the CTMU you just don't want to think of the analog to digital converter as just an ADC but it provides the ability to carry out capacitive touch. If you use 8 channels for A to D you can still have 16 channels capacitive touch button or sliders. With the CTMU, each channel can monitor a separate button and these can be multiplexed together to give you more keys if you need them.”

“Proximity detect looks a look like a capacitive touch button and you can set this device to run in the low power sleep mode and when it detects something coming near it, it can trigger and wake up from the sleep mode and go in to active mode where maybe it turns on the backlighting for the display or starts to look for other capacitive touch buttons.”

There are a couple of additional ADC channels which are used internally for operations like internal temperature sensors.

The PIC24F ‘GA3’ devices are targeted for use in consumer thermostats, door locks, and home automation; industrial products such as security, wired and wireless sensors, and controls; portable medical devices and medical diagnostic equipment; and metering products including e-Meters, energy monitoring, automated meter reading and meters for gas, water or heat; in addition to other applications.

“One of the areas we are seeing a lot of interest in is water and heat meters where they are transitioning to ultrasonic flow technology which use two transducers to bounce a sound from one to the other and by measuring the time taken determines the speed of the fluid in the pipe,” said Don Schneider. “The CTMU will allow time measurement with resolutions down to 10 pS.”

Power meters are constantly on and monitoring the power. They are required to meet a 10 VA IEC current budget and many power companies are asking for still lower power numbers. To achieve the 10VA target an MCU must consume around 10 mA or less. Many MCU must operate at reduced speed to stay with in this budget. The GA3 family can operate at its full 16 MIPS with 4.9 mA. This allows the device to either add function, perhaps running more complex code or a communication stack. The other option is to continue running the device at a slower sped and conserve still more power. The DMA channels on the device to move data to peripherals in parallel with the CPUs operation. Once again this  frees the CPU for other functions. An example of a DMA operation could be the transfer of data from the device RAM to a serial channel for an RF communication Stack.

These devices have also been added to Microchip's Battery Life Estimator which now covers approximately 105 devices.

To aid development the PIC24FJ128GA310 plug-in module (left) is available for $25 and is used with the company's Explorer 16 development board (above right). To evaluate or develop designs with a 480-segment LCD, the LCD Explorer Development Board (pictured below) is available for $125.00

Samples and volume production in versions with 64 KB or 128 KB of lash. The PIC24FJXXXGA306 MCUs are available in 64-pin QFN and TQFP packages; PIC24FJXXGA308 versions are available in an 80-pin TQFP package; whilst PIC24FJXXXGA310 are available in 100-pin TQFP and 121 BGA packages.


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