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4

RD-0608

t_LO_on

t_HO_off

DT1

IFBTH

50%

50%

50%

50%

t_LO_off

DT2

t_HO_on

HO

LO

IFB

50%

Fig. 3 IRS2540/1/01/11 Control Signals, Iavg=1.2A

Fig. 4 IRS2540/1/01/11 Time Delayed Hysteresis

The switching continues to regulate the current at an average value determined as follows: when the output

combination of L1 and COUT is large enough to maintain a low ripple on IFB (less than 100mV), Iout(avg) can be

calculated:

RCS

VIFBTH

avg

Iout

=

)

(

Having load current programmable from 350mA to 1.5A, series and parallel combinations of resistors must be used

to correctly set the current as well as distribute power accordingly. Equivalent resistances for each current setting

are calculated as follows:

Ω

=

=

43

.

1

350

5

.

0

350

mA

V

R

mA

Ω

=

=

71

.

0

700

5

.

0

700

mA

V

R

mA

Ω

=

=

5

.

0

1

5

.

0

1

A

V

R

A

Ω

=

=

33

.

0

5

.

1

5

.

0

5

.

1

A

V

R

A

(A)

(B)

Fig. 2 (A) Storing Energy in Inductor

(B) Releasing Stored Inductor Energy