L9965P datasheet(86/104 Pages) STMICROELECTRONICS

86 / 104 page

4.1.2

12 V DC-DC with MCU and ERBST mounted

The Figure 30 shows a typical application diagram for a pyro-fuse system supplied by a low current DC-DC

regulator, using the ERBST regulator and interfaced with a generic MCU.

Figure 30. Application circuit: 12 V DC-DC with MCU and ERBST mounted

Arming logic

Deployment

driver

3V3 int

regulator

ER boost regulator

ER discharge

switch

Global configuration and

control, ADC, bias and

diagnostics

5V or 3.3V

FAULTN

CWUP

NCS

SCLK

SDI/MOSI

SDO/MISO

Power management, diagnostics and monitoring

CIN

LERBST

DERBST

CER1

RDCH

PYRO

FUSE

VIO

PGND

CER2

RFAULTN

CVIO

CPF

CPR

MCU

CFAULTN

12V

DC-DC

Signal from MCU

RCHG

MCU

PMIC

The CER electrolytic capacitors are connected to ERBST regulator that charge them to a higher voltage respect to

battery level VBAT. In this case the ERBST power limit function can be used to limit the ERBST input power and

so the power required to the 12 V DC-DC regulator.

ERDCHSW pin is used to allow CER controlled discharge for safety and diagnostic purposes. RDCHG sets the limit

current for the discharge phase.

Note:

See the dedicated Application Note.

L9965P

Application scenarios

DS14702 - Rev 4

page 86/104

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