BQ26150 Datasheet, PDF(9/16 Page) Texas Instruments – BATTERY PACK SECURITY AND AUTHENTICATION IC FOR PORTABLE APPLICATIONS (bqSECURE)

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BQ26150 Datasheet, PDF (9/16 Pages) Texas Instruments – BATTERY PACK SECURITY AND AUTHENTICATION IC FOR PORTABLE APPLICATIONS (bqSECURE)

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www.ti.com

bq26150

SLUS641A â JANUARY 2005 â REVISED JULY 2005

P14

AV[15]

P13

AV[14]

P12

AV[13]

P11

AV[12]

P10

AV[11]

AV[10]

AV[9]

AV[8]

AV[7]

AV[6]

x10

AV[5]

x11

AV[4]

x12

AV[3]

x13

AV[2]

x14

AV[1]

x15

AV[0]

INPUT

(lsb first)

Figure 3. bq26150 Programmable CRC Hardware Implementation

The generic polynomial used in the bq26150 can be written as:

1+P14x1+P13x2+12x3+P11x4+P10x5+P9x6+P8x7+P7x8P6x9+P5x10+4x11+P3x12+P2x13+P1x14+P0x15+x16

Figure 3 shows the hardware implementation of the CRC, with the corresponding bits of the authentication value

shown below each stage of the shift register. This configuration assumes that the x0 term coefficient, which is

P15, is always 1, which was stated as an assumption of a normal CRC polynomial. This means that there are 215,

or 32768, possible CRC polynomial values. In actually, the number of possible CRC polynomial will be less than

32758 because some values, such as all 0, do not provide sufficient mixing of the results to be secure.

To authenticate a battery pack using the bq26150, the host must reproduce the CRC calculation in software. This

is done by reading the encrypted device ID and encrypted polynomial coefficients, and encrypted seed. All

values are decrypted by the host to provide the 16-bit polynomial, 16-bit seed, and 96 of the 128 bits of

calculationâs input. The CRC input is:

Device ID [95:0]

Random Challenge [31:0]

Input MSB

Input LSB

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