L9965P datasheet(90/104 Pages) STMICROELECTRONICS

90 / 104 page

4.2

Device positioning in BMS application

The L9965P can be interfaced with the companion chip L9965C which performs the function of monitoring HV

battery current, detecting short circuit and triggering pyro-fuse deployment. It also acts as an SPI controller,

forwarding frames sent by MCU to L9965P.

L9965P is identified in the BMS chipset by the BMS_ID bit field located in the BMS_ID register. It is possible to

read the IC version in the CHIP_ID register.

Depending on the source of main supply, the devices can be mounted in HV or LV domain: L9965C, due to its

specific purpose, will always lie in the HV domain, while L9965P can be mounted in either of the two, depending

on the user’s hardware and limitations, if any.

In the HV domain, supply can be sourced from an HV battery through an isolated DC-DC converter and shared

between L9965P and L9965C (Figure 33 configuration "a").

•

Pros:

–

Possible to avoid usage of ER boost regulator and related external components.

–

Deployment trigger pins direct connection to L9965C.

–

L9965C acts as a SPI controller to route commands from the MCU.

•

Cons:

–

SPI signals suffer a higher delay.

Some pyro-fuse switches might not be compatible with the above solution and require the driving section to be in

the LV ground domain (Figure 33 configuration "b").

•

Pros:

–

Direct connections to MCU’s SPI.

–

Compatibility with all pyro-fuse switches.

•

Cons:

–

Cannot avoid ER boost usage (unless minimum VBAT can be guaranteed).

–

Requires additional components (isolators to interface with L9965C).

Figure 33. Pyro-fuse driver positioning

(a)

(b)

L9965P

Application scenarios

DS14702 - Rev 4

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