L9679P datasheet(47/272 Pages) STMICROELECTRONICS

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L9679P

Start-up and power control

271

6.8

SATBUCK regulator

The SATBUCK regulator provides a nominal 7.2 V regulated output voltage at startup for the

remote satellite and wheel speed interface circuitry and the VCC buck regulator. The buck

regulator is enabled automatically by the power control state machine. This regulator is

protected against short circuits. Should the user need a higher voltage range for the remote

sensor interface, a specific SPI command allows the output voltage to be increased at 9 V

nominal by setting the SAT_V bit. Fault status is available through SPI in the Fault Status

smaller less expensive external components. Moreover, the synchronous buck regulator

integrates the external recirculation diode.

Figure 22. SATBUCK regulator state diagram

6.9

VCC buck regulator

The VCC buck regulator also operates at 1.882 MHz and is user selectable to either 3.3 V or

5 V nominal output voltage. The user can select the output voltage through the VCCSEL

pin. To select 5 V operation, the user must bias VCCSEL to a level higher than

VTH2_H_VCCSEL for instance SyncBoost. For 3.3 V operation, the VCCSEL pin must be

biased to a level lower than VTH2_L_VCCSEL. An internal weak pull down is connected to

VCCSEL to ensure the input remains at ground potential in case of open pin. The internal

power control state machine will read the VCCSEL input pin and latch the resulting state

upon the SATBUCK voltage reaches the good value (SATBUCK_OK = 1). Upon latching the

VCCSEL state, the VCC buck regulator cannot be changed by the user.

The VCC regulator has over and under voltage detections and shutdown capability and it is

also protected against short circuits. During start-up an internal pull up current is enabled in

order to detect a potential VCC pin open fault trough the over voltage detection. This pull up

current is disabled once in VCC_ON or VCC_SHUTDOWN states. During normal operation,

VCC_ON state, the VCC pin open fault is quickly detected through the Under Voltage

Detection Low to prevent any MCU damage.

L9679P 数据表(PDF) 47 Page - STMicroelectronics