L9963E datasheet(145/184 Pages) STMICROELECTRONICS

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6.8

ISO lines circuit

The following section illustrates the typical analog front end to communicate about the vertical insulated interface.

6.8.1

Transformer-based insulation

The transformer-based insulation is recommended for global communication lines between different modules in a

distributed BMS. It offers better insulation and higher immunity to BCI, being the transformer an intrinsic common

mode filter.

Figure 41. Transformer based ISO lines circuit

L9963E

ISOHp / ISOLp

CCM_KHZ

D_ESD

ISOHm / ISOLm

TRANSF

VCOM

GND_ESD

CCM_MHZ

AGND

CESD_VCOM

Table 81. Transformer-based ISO lines BOM

Components Value

Unit

Max.

tolerance

Rating

Comments

RTERM

Ω

10%

1/16 W

Termination resistance. Differential output signal amplitude can

be calculated with the following equation:

VISODIFF=VCOM RTERM

RDIFF_ISO_OUT

CCM_KHZ

6.8

10%

10 V

Filter common mode noise in the kHz range (inverter

and other power converters). Pole introduced is

fcut_kℎz=

πCCM_KHZ RISODIFF2+RTERM+7.2kΩ .

Do not exceed 10 nF, otherwise common mode settling time

upon ISO port enable will last too long. Connect to AGND.

CCM_MHZ

10%

16 V

Filter common mode noise in the MHz range

for improved BCI immunity. Pole introduced is

fcut_mℎz= 1

2πCCM_MHZRTERM.Donotexceed47pF,

otherwise differential output signal in high frequency mode

might be strongly distorted. Connect to AGND.

CESD_VCOM

µF

10%

16 V

Deviate energy clamped by DESD directly to AGND, preventing

any ESD strike from affecting other PCB components. Total

capacity on the VCOM pin must be equal to 2.2 µF. Hence,

in BMS configuration, the recommended capacity distribution is:

1 µF as CESD_VCOM on the ISOH clamp, 1 µF as CESD_VCOM

on the ISOL clamp, 200 nF as CVCOM directly on the VCOM pin

(refer to Table 73). Connect to GND_ESD

DESD

It must be mounted only for Distributed BMS where isolated

SPI pins are global pins or the ECU.

L9963E

ISO lines circuit

DS13636 - Rev 12

page 145/184

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