Datasheet

DocID18279 Rev 5 25/37
ST1CC40 Application information
37
 Switching losses due to turning ON and OFF. These are derived using Equation 29:
Equation 29
where T
RISE
and T
FALL
represent the switching times of the power element that causes the
switching losses when driving an inductive load (see Figure 14). T
SW
is the equivalent
switching time.
Figure 14. Switching losses
Quiescent current losses.
Equation 30
Example (see Section : Example):
V
IN
= 12 V, V
FW_LED
= 3.5 V, n
LED
= 2, I
LED
= 700 mA
The typical output voltage is:
Equation 31
R
DSON_HS
has a typical value of 95 m and R
DS(on)_LS
is 69 m at 25 °C.
For the calculation we can estimate R
DS(on)_HS
= 140 m and R
DS(on)_LS
= 100 mas
a consequence of T
J
increase during the operation.
T
SW_EQ
is approximately 12 ns.
I
Q
has a typical value of 1.5 mA at V
IN
= 12 V.
P
SW
V
IN
I
OUT
T
RISE
T
FALL
+
2
---------------------------------------- - F
SW
V
IN
= I
OUT
T
SW_EQ
F
SW
   =
AM14826v1
P
Q
V
IN
I
Q
=
V
OUT
n
LED
V
FW_LED
V
FB
+ 7,1V==