L9680 datasheet(49/277 Pages) STMICROELECTRONICS

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L9680

Start-up and power control

276

6.10

VCOREMON external core voltage monitor

The device includes the possibility to monitor the external core voltage of MCU in case an

additional external regulator is used to provide the 1.2V rail. The internal power control state

machine will read the VCCSEL input pin and latch the resulting state upon the VCCBUCK

regulator enters in the VCC_ON state: if VCCSEL is lower than VTH1_L_VCCSEL the VCORE

monitor will be enabled, otherwise, if VCCSEL is higher than VTH1_H_VCCSEL, the VCORE

monitor will be disabled.

In summary:



VCCSEL < VTH1_L_VCCSEL (VCCSEL shorted to ground), to select VCC = 3.3 V and to

enable the VCORE monitor



VTH1_H_VCCSEL < VCCSEL < VTH2_L_VCCSEL (VCCSEL shorted to VCC), to select

VCC = 3.3 V and to disable the VCORE monitor.



VCCSEL > VTH2_H_VCCSEL (VCCSEL shorted to SYNCBOOST), to select VCC = 5 V

and to disable the VCORE monitor.

The VCORE monitor is enabled once the VCC regulator is in VCC_ON state, therefore the

external MCU core voltage regulator (1.2 V) must reach the regulation within 4ms after the

VCC regulator power-up.

Upon latching the VCCSEL state, the VCOREMON activation cannot be changed by the

user.

In case of VCCSEL open pin, an internal pull down current would force VCCSEL to ground

and then the VCORE monitor will be enabled function.

6.11

VSF regulator and control

The L9680 provides a low current linear regulator that can be used in the system design to

bias the external high side safing switch. The regulator output is 20 V nominal (configurable

to 25 V via SPI command). VSF is enabled if any of the ARMxINT signal is asserted, as

shown in Figure 24. The VSF regulator supply input is ERBOOST.

Figure 24. VSF control logic

VSF voltage can be monitored by the user through the internal ADC. Characteristics for this

function are shown in the electrical performance tables.

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