L584 查看數據表（PDF） - STMicroelectronics

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L584

MULTIFUNCTION INJECTION INTERFACE

STMicroelectronics 

Figure 9 : Application circuit showing how two separate supplies can be used.

L584

In this application it is assumed that the 5V supply

for L584 is taken from a logic supply, which is al-

ready protected, against load dump transients and

vol-tage reversal.

Pin 1 must be left

alwaLys lower than

open, as

46V even

shown in fig. 9, if VS is

during the voltage tran-

sienRts.

Note that toff is also related to the required current

ripple ∆I on the peak or on the holding current level

by :

toff = –

ln (Io – ∆I) RL + Voff

Io RL + Voff

Where : Io is the initial current valuein OFF condition

(equal to Ip or IH in accordance to the current level

considered),

VOFF = VDIODE + VCEQ1

RL is the series resistance value of the induc-

tance L :

Therefore C2 can be dimensioned directly by :

C2 =

IREF L

12

ln (Io – ∆I) RL + VOFF

RL Io RL + VOFF

Note that toff is the same for both the peak and hold-

ing current.

ton time is given by :

L Von – R(I1 – ∆I)

ton = R ln Von – RI1

where : I1 is the final current value in ON condition

(equal to Ip or IH in accordance to the current level

considered),

R = RL + RSENSE

Von = VS – VCEsatQ2

If the constant times are respectively

L

L

R > 20 toff and R > 20 ton

it is possible to consider a purely inductive load and

therefore :

∆I

∆I

toff = L Vo ; ton = L Von

11/13

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