L9961 datasheet(25/63 Pages) STMICROELECTRONICS

25 / 63 page

3.5

Current conversion routine

The current conversion routine can be enabled by programming the CSA_EN bit: if disabled, the ADC, the

monitoring functions and coulomb counting are not available.

Enabling the current conversion routine increases VB current consumption by IVB_NORM_DELTA_CSA.

3.5.1

Current sense ADC (ISENSEP/ISENSEM)

L9961 integrates a current sense amplifier and a fully differential sigma-delta ADC, capable of performing

continuous acquisition of the pack current using an external shunt resistor connected between ISENSEP and

ISENSEM pins.

Each sample acquisition lasts TCUR_FILTER (programmable via T_CUR_FILTER field) and a new acquisition starts

upon completion of the previous conversion.

The latest sample acquired by the ADC is available in the CUR_INST_MEAS register, encoded in 2’s

complement.

The CSA comes with a native gain error of CSAGAIN_ERR. To furtherly improve the accuracy, L9961 offers the

possibility to perform end of line calibration using a single setpoint. By programming the CSA_GAIN_FACTOR

The end of line calibration procedure is the following:

Read the CSA_GAIN_FACTOR register and store the factory correction factor KGAIN_FACTORY in a

temporary variable

CSA_GAIN_FACTOR register is decoded as follows:

CSA_GAIN_FACTOR decode

CSA_GAIN_FACTORdecimal=b15*20+b14*2−1+b13*2−2+…+b0*2−15

(2)

Force a precise and stable VCSA_CAL voltage on the ISENSEP-ISENSEM pair

Enable the CSA and the Coulomb counter by programming CSA_EN = 1 and CC_ACC_EN = 1

Let the Coulomb counter acquire at least 30 samples in order to eliminate any superimposed noise

Download the Coulomb counter data as described in Section 3.5.2 Coulomb counting and extract the

VCSA_MEAS average value

Calculate the gain correction factor KGAIN_CAL

CSA gain correction factor definition

KGAINCAL= VCSACAL

VCSAMEAS

(3)

Calculate the End Of Line correction factor KGAIN_EOL and write it into the CSA_GAIN_FACTOR register

CSA end of line correction factor calculation

KGAINEOL=KGAINFACTORYKGAINCAL

(4)

Push the data into the NVM following the procedure described in the Non-Volatile Memory (NVM)

Total conversion error (TCE) can be computed as the following formula (see CSA total conversion error) where

the gain error CSAGAIN can be either CSAGAIN_ERR or CSAGAIN_ERR_CAL depending if end of line calibration is

performed or not.

L9961

Current conversion routine

DS14012 - Rev 1

page 25/63

L9961 датащи(PDF) 25 Page - STMicroelectronics

L9961 датащи(HTML) 25 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

датащи скачать

ссылки URL