Dallas Semiconductor announced a single chip that monitors battery parameters and stores pertinent data for battery identification and charge control. Integrating a 10-bit voltage A/D converter, temperature-sensing circuitry, and nonvolatile memory, the DS2436 Battery Identification/Monitor Chip is designed for use as a data-acquisition system for batteries.

"The DS2436 combines the features of two devices in the Dallas Semiconductor Battery Management family: the temperature-sensing and nonvolatile data storage functions of the DS2434 and the battery-identification capabilities of the DS2401," said Norbert Wank, product manager. "These functions, along with battery voltage monitoring, distinguish the DS2436 from other battery management ICs that monitor fewer parameters with less accuracy."

Distinguishes OEM Batteries from Clones

Battery packs equipped with a DS2436 carry their identification parameters and manufacturing data in 256 bits of nonvolatile memory. The device uses this information to distinguish OEM batteries from clones, ensuring safe and efficient battery charging. The DS2436 is a chemistry-independent device: the host's firmware can use temperature and voltage data for charge termination and fuel gauging.

Wank said, "Protecting the battery and the system becomes increasingly important as battery chemistries continue to proliferate, battery manufacturers produce clones, and fast charging routines become more popular. Many OEM batteries can be safely fast-charged, but some clone products should be trickle-charged only."

Minimal Interconnects

The DS2436 uses Dallas Semiconductor's proprietary 1-Wire technology to reduce the number of interconnects required for operation to three: data, power, and ground. With these minimal interconnects, the DS2436 can be mounted directly in the battery pack, reducing tooling costs and board space consumption. The chip can share this data line with other 1-Wire components through the unique 64-bit ROM address assigned to each device, simplifying the design of gang chargers, general-purpose chargers for multiple battery packs, and battery clusters.

Provides the Accuracy Important for Safe Charging

The device's onboard A/D voltage converter provides highly accurate readings of the cell voltage, bypassing the power-supply circuit's total resistance. This approach ensures the safety of fast-charging, high-capacity batteries as they-and the systems 1-Wirethey power-age.

"The quick-charge current of 800-, 1000- and 1200-mAh cells can reach 1A," Wank said. "Resistances throughout the circuit change over time and with oxidation and temperature. If you over-compensate, you can end up with a charging voltage that's greater than the battery can safely handle. At the other end of the spectrum, you might never reach the full potential of your battery."

External A/D converters implemented in ASICs can't accurately measure the cumulative resistance of printed circuit boards, contacts, solder joints, wires, and other components. Both voltage and temperature data are required to interpret battery capacity status correctly. A high 10 mV resolution in the A/D converter facilitates charge and discharge control and eliminates voltage measurement errors due to contact and cable parasitic resistance. The onboard 13-bit temperature sensor determines the temperature-based charge cut-off point. A cycle counter manages battery maintenance intervals and functions as a wear-out indicator.

The chip's 64-bit unique identification code can be accessed through the use of a parasite-powered single data line even when the system has experienced total battery voltage failure. A two-byte manufacturing ID value authorizes equipment usage and can be customized at the factory.

There are really only two companies who have taken this market as their own -- and not just as a sideline to their other businesses -- and focus on the developments that take place. Battery architecture is getting more and more complicated and the different chemistries that are around create some real problems for the OEMs. Clone batteries may, in many cases, be safe product replacements but in others they could be literally explosive! In many ways the OEMs need to protect themselves against others' stupidities otherwise they could end up in expensive litigation from a user who "didn't know" any better: fast charging a clone under the wrong conditions could be a disaster that someone else needs to prevent.

Combining the DS2401 and DS2434 into one part is putting together two great products, already with a history, into an entirely logical next-generation part; the part is operable over a large supply range, from 2.7 top 10 V and the full industrial temperature range.

This is not a product that Dallas Semi can lose with. The DS2436 is packaged in a three-lead PR-35 or a 16-pin SSOP and tape-and-reel format and is priced at $4.10 in 1000-piece lots.