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bq27x00 vs bq2622x series

Anonymous
Anonymous

Hi,

I would like to ask a question on bq27x00 and bq2622x series.

I read from Application Report SLUA358, Choosing Between Battery Gas Gauges and Battery Monitors to Track Charge Availability in Handheld Devices, that:

Page 1:

A gas gauging algorithm in a microprocessor is used to analyze the data. This algorithm is complex, due to the various characteristics among batteries that must be considered.

  1. Self-discharge and aging of batteries also must be considered when implementing gas gauging.
  2. A battery that is at rest may show decreased capacity after an extensive time because of self-discharge.
  3. As a battery ages, the impedance is higher, and hence decreases the total battery capacity that can be used.

Page 2:

The small CPU that is in the bq27x00 devices contains an advanced gas gauging algorithm developed by TI for single-cell, Li-ion applications. The

bq2622x does not have this small CPU. With the bq2622x, the gas gauging algorithm is performed by the host. The host has to get the measurement data such as battery voltage, charge and discharge current, and battery temperature to calculate the remaining capacity and estimate the battery run time.

Coulomb counters that have the internal CPU with a gas gauging algorithm are known as gas gauges, whereas coulomb counters without a CPU are known as battery monitors.

 

I compared some aspects of the two series from datasheets:

 

bq27x00

bq2622x

Datasheet year

2004

2004

Name

battery gas gauge

battery monitor

Price($)

1.15-1.25

2.55-2.60

CPU

✓

✕

Register maintenance by host

not required

required, otherwise some will overflow

Example:

discharge count registers (DCRH/DCRL)

charge count registers (CCRH/CCRL)

self-discharge count registers (SCRH/SCRL)

Register count

RAM: 25

EEPROM: 11

13

Automatic calculation

many

Example:

 

Available Energy Registers

(SAEL/SAEH)

SAE(mWh) = (256*SAEH + SAEL) * 29.2 / Rs(mΩ)

 

SAE = 8 * CACT * (3088 +512*NAC/LMD)/65536

 

SAE = 4 * CACT * (Reported Voltage + EDVF)/65536

Max Load Current Registers (MLIL/MLIH)

Max Load Current = (256*MLIH + MLIL) * (3.57/ RS )

Compensated State-of-Charge (CSOC)

CSOC (%) = 100 * CACT/LMD

Not found

 

Question 1:

Does the "complex algorithm(s)" cited in SLUA358 refer to the "Automatic calculation" row the table?

Question 2:

The two series have most likely the same release year according to datasheet versions, and are both still active. From all most all aspects' comparison bq27x00 series is more advanced and convenient than bq2622x series, but why curiously the latter have higher price than the former?

 

 

Zheng

  • 0
    TI__Intellectual 2340 points

    Zheng,

    Answer to Question 1:

    The complex algorithm is more than just those calculations. It is knowing when the battery is fully charged, knowing to compensate remaining capacity based on load rate and temperature, etc. The higher the accuracy that you want to achieve the more complex that the gauging algorithm becmes.

    Answer to Question 2:

    The bq2622x devices are much older than the bq27x00. The datasheet date may not reflect the actual device release date. The datasheet date should reflect when the document was last updated. The price may be due to improvements on technology processes which help to reduce production cost.

  • Anonymous
    0 Anonymous in reply to MikeV

    Mike,

    This question is resolved. Thanks.

     

    Zheng