If no external pull-up is connected to OD, the external COD capacitor is discharged with a time constant defined by

COD and the internal MOSFET's characteristic (Eq. (1)), and the Restart time is determined by the internal current

source IOD and by COD (Eq. (2)).

t1≅RON_OD⋅COD⋅ln VODVSSDl

(1)

t2≅COD⋅VSSDℎ

IOD ⋅ln VSSDl−VOD

VSSDℎ−VOD

(2)

In case the OD pin is connected to VCC by an external pull-up resistor ROD_ext, the OD discharge time is

determined by the external network ROD_ext COD and by the internal MOSFET's RON_OD (Eq. (3)), while the

Restart time is determined by current in ROD_ext (Eq. (4)).

t1≅COD⋅ ROD_ext//RON_OD ⋅ln VOD−Von

VSSDl−Von

(3)

t1≅COD⋅ROD_ext⋅ln VSSDl−VOD

VSSDℎ−VOD

(4)

Where:

Von= RON_OD

RON_ext+RON_OD;VOD=VCC

STDRIVE601

Comparator and smart shutdown

DS12949 - Rev 2

page 15/26