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The OD Restart time (t2 in Figure 14), which is the time required to recharge the COD capacitor up to the

VSSDh threshold. The recharge of COD starts when the OD internal MOSFET is turned-off, which happens

when the fault condition has been removed (CIN < VREF - CINhyst) and the voltage on OD reaches the

VSSDl threshold. This time normally covers most of the overall output disable time.

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 (Equation 1), and the Restart time is determined by the internal

current source IOD and by COD (Equation 2 ).

Equation 1

t1≅RON_OD ∙COD∙ln VODVSSDl  

(1)

Equation 2

t2≅COD∙ VSSDh

IOD ∙ln VSSDl−VOD

VSSDh−VOD

(2)

Where VOD = VFLOAT_OD

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 (Equation 3), while the

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

Equation 3

 t1≅COD∙ ROD_ext//RON_OD  ∙ln VOD−Von

VSSDl−Von

(3)

Equation 4

t2≅COD∙ ROD_ext ∙ln VSSDl−VOD

VSSDh−VOD  

(4)

where:

Von= RON_OD 

ROD_ext+RON_OD ∙VCC ; VOD=VCC

PWD5T60

Functional description

DS14558 - Rev 2

page 15/27