Tag Archives: ICs

7/13-cell applications with Atmel’s ATA6870 (Part I)

A standard (automotive) battery measurement system using Atmel’s ATA6870 is capable of measuring the voltage of up to 6 battery cells. Several of these ICs can be stacked in series to measure the voltage of up to 96 battery cells simultaneously. For the majority of applications, the “stacked” battery measurement IC approach is sufficient, as the number of cells measured in these applications is a multiple of three, four or six.

batterymanagementfigure1

“In some instances, such as an e-bike application, the cell count of the battery may be of an odd number: 7 or 13 cells,” Atmel engineering rep Darius Rydahl told Bits & Pieces. “With these applications, the use of multiple, stacked ATA6870 circuits combined with a standard microcontroller (MCU) may not be the most cost-effective solution for the end application.”

According to Rydahl, a more practical, lower cost implementation is to use one ATA6870 chip in conjunction with an Atmel battery management microcontroller.

“The standard implementation of an ATA6870 battery management system consists of at least one ATA6870 battery measurement IC (maximum sixteen, connected in series) plus a general-purpose MCU for control and data processing,” Rydahl continued. “As you can see in the image above (Figure 1), the MCU is powered by the lower ATA6870 IC’s on-board 3.3V voltage regulator (VDDHVM). Communication occurs via SPI where data is transferred serially between multiple ATA6870 circuits, one IC to the next, to/from the MCU.”

As shown in Figure 1, a common ground reference is shared between the bottom ATA6870 device and the MCU. In this instance, there is no voltage offset between the MCU and the ATA6870 circuit, neatly eliminating the need for additional interface circuitry between the CLK and SPI pins of the two ICs.

batterymanagementfigure2

In applications where the total cell count is a multiple of 7 or 13, the designer can simply add additional ATA6870 ICs to the battery stack as shown in Figure 2. However, the 7 battery cells must be split between the ICs to maintain the minimum operating voltage of 6.7V for each ATA6870 IC.

“Atmel offers two possible solutions for the seven-cell application using a battery measurement MCU as shown in Figure 3. In this example, the ATA68670 IC can be paired with either the  ATmega32HVE2, or ATmega32HVB MCU,” said Rydahl.

batterymanagementfigure3

“Both MCUs have battery voltage and current measurement capabilities. The feature sets and peripheral offerings (number of cell measurement inputs, LIN bus interface, etc) of two MCUs are slightly different, so the specific requirements of the end application must be taken into consideration before selecting the MCU.”

Interested in learning more about using 7/13-cell applications with Atmel’s ATA6870? Be sure to check back tomorrow for part two of this series.

Under the hood with Atmel tech

Engineers building complex systems slated for “under the hood” tasks know there is little room for weak designs in such demanding environments.

Indeed, high temperatures, strong mechanical vibration and fluctuating electromagnetic fields demand the inclusion of products based on decades of optimized architecture, meticulous manufacturing and robust testing.

And that is why Atmel’s motor driver family targets brushed and brushless DC motors capable of operating in standard temperature – or even more demanding hot engine environments.

“A wide variety of combinations integrate high-side and low-side output stages so manufacturers can easily tailor solutions to suit customer needs,” an Atmel engineering rep told Bits & Pieces. “Plus, our driver portfolio includes ICs for small DC motors controlled directly from the output stages, as well as motor driver system basis chips, with integrated gate drivers or pre-drivers to control separate NMOSFETs of almost any size.”

Key features include rugged design, with Atmel’s unique BCD-on-SOI architecture combining high-voltage capability with the benefits of rugged SOI technology: high temperature resistance (T-junctions up to 200°C), optimized radiation hardness, very low leakage currents, low parasitics, high switching frequency and latch-up immunity.

We also offer cost-effective ICs that require few external components, because capabilities such as LIN connectivity and diagnostics are already built in. Plus, all Atmel drivers share the same protective features—over-temperature warning and switch-off, as well as under-voltage, over-current, short-circuit and open-load detection.

Interested in learning more about Atmel’s extensive motor driver portfolio? Be sure to check out our full device breakdown here.