AS3834 datasheet(12/21 Pages) AMSCO

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AS3834

Datasheet

8.2 VDDH_HC resistor

Figure 10. VDDH_HC resistor

Pin VDDH_HC is connected to an internal 3.3V voltage regulator. In order to keep the power dissipation of this regulator low, it is recommended

to connect pin VDDH_HC to the power supply Vin with a resistor. The resistor should guarantee sufficient voltage drop so that the remaining

voltage at pin VDDH_HC is approximately 5V. The power dissipation of the RVDDH_HC hat to be considered.

Typical values for RVVDH2 are:

VIN = 13V:

RVDDH_HC= 150Ω / 0.5W

VIN = 24V:

RVDDH_HC= 380Ω / 1.5W

8.3 Safety features

8.3.1

Undervoltage lockout

In order to avoid startup of the Boost controller at low supply voltage an undervoltage lockout function is implemented. The boost controller only

turns on when the voltage at pin UVLO exceeds VUVLO. Once the boost controller is turned on a current source IUVLO_Hyst is activated which

increases the UVLO voltage and so shifts the turn off voltage level.

Figure 11. Undervoltage lockout

VDDH

_HC

–

50mA

--------------------

(EQ 2)

V DDH

_HC

50mA

(

)

VDDH

_HC

(EQ 3)

AS3834 Datasheet(PDF) 12 Page - ams AG