Product category:
Power Supply ICs and Controllers
News Release from: Maxim Integrated Products | Subject: DS2790
Edited by the Electronicstalk Editorial
Team on 10 August 2006
IC brings measurement to simpler battery
formats
Dallas Semiconductor's DS2790 is a real first: an affordable device for incorporating fuel-gauging and protection in single cell battery devices.
Anyone wanting to incorporate sophisticated algorithms for fuel-gauging into single cell systems has traditionally had a problem, with no affordable option being available The DS2790 from Dallas Semiconductor is set to change all that
This article was originally published on Electronicstalk on 27 Aug 2002 at 8.00am (UK)
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It incorporates a MAXQ microcontroller, as well as ample program and data memory as part of an accurate system for battery current, voltage and temperature measurement.
In the past, manufacturers have been forced to adapt ICs designed for 9- to 12-cell count battery packs like those in notebook computers.
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To exacerbate the situation, those multicell battery packs were too costly for use in a single-cell application like a cellphone.
Besides the DS2790, there is currently no other competitive device with this capability at a comparable price point.
The DS2790 is a truly unique device.
Optimised for a single-cell Li+ battery pack, the DS2790 microprocessor-based solution enables the fuel-gauging capability and customisation traditionally reserved for devices that serve battery packs with much higher cell counts and more complexity, such as those found in notebook computers.
At the heart of the DS2790's computing core is the low-power 16bit MAXQ20 microcontroller with its advanced, accumulator-based (MAC), 16bit RISC architecture.
Highly efficient, its fetch and execution operations are completed in one cycle without pipelining, because the instruction contains both the operation code and data.
The processing core is supported by a 16-level hardware stack, which enables fast subroutine calling and task switching.
Data can be quickly and efficiently manipulated with three internal data pointers.
Multiple data pointers allow more than one function to access data memory without having to save and restore data pointers each time.
To allow the user to program proprietary algorithms, the DS2790 contains three types of memory: programming memory, data EEPROM, and data RAM.
The memory is arranged in a Harvard architecture, with separate address spaces for program and data memory.
The 16Kbyte of programming memory consists of 8Kbyte of password-protected EEPROM and 8Kbyte of ROM.
The inclusion of EEPROM allows the devices to be reprogrammed, which simplifies and reduces the cost of development and field upgrades.
The ROM contains routines that allow reprogramming over the I2C interface, SHA-1 authentication, and support for in-circuit debugging.
The data EEPROM consists of 128byte, and is available for storing important data such as charge parameters, cell characteristics, and manufacturing data that should remain unaffected by sever battery depletion, accidental shorts, or ESD events.
The data RAM is 512byte, and is used for temporary data storage.
The DS2790 also provides precise current, accumulated current, voltage, and temperature measurements.
The 12bit-plus-sign current measurements are an average of 128 individual current samples.
The current measurements are internally summed to produce the accumulated current with accuracy within +/-2% of full-scale measurement, +/-4uV over a range of +/-64mV.
Using a 15mohm sense resistor, this current accuracy translates to within +/-2% of full scale, +/-267uA over a 4.2A range.
Standby currents are measured with an accuracy of +/-195uA.
The DS2790 measures voltage as a 10bit-plus-sign value over a 0 to 4.75V range with a resolution of 4.8mV.
An on-chip temperature sensor measures the temperature of the battery and reports the results as a 10bit-plus-sign value with a resolution of 0.125C.
All measured data and any password-protected reprogramming of the EEPROM memory can be communicated to the host through the DS2790's I2C communication interface.
A single-cell protector provides even greater performance-to-cost capability.
The DS2790's single-cell Li+ protection circuitry is comprised of an autonomous state machine that provides the overvoltage, undervoltage and over/underdischarge protection.
Safety and reliability are increased because the protection function does not rely on the CPU and, therefore, does not depend on its loading to perform other functions.
Typical applications for the DS2790 include wireless handsets, high-end PDAs, digital video camcorders, and digital still cameras.
The device is available in 28-pin TSSOP and TDFN packages with prices starting at US $2.50 (1000-up, FOB USA).
(Updated by CR, May 2007).
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