EVALED2000P STMicroelectronics, EVALED2000P Datasheet - Page 29

• Manufacturer Part Number: EVALED2000P
• Description: LED Lighting Development Tools LED2000 3A 850KHz 3.0V to 18V Eval BRD
• Manufacturer: STMicroelectronics

Specifications of EVALED2000P

• Product Category: LED Lighting Development Tools
• Rohs: yes
• Product: Evaluation Boards
• Operating Supply Voltage: 3 V to 18 V
• For Use With: LED2000

LED2000
The inductor current ripple during ON and OFF phases can be written as:
●
Equation 40
●
Equation 41
where DCR
The pulse-by-pulse current limitation is effective to implement constant current protection
when:
Equation 42
From
current protection becomes more critical the lower the V
In fact, in short-circuit condition the voltage applied to the inductor during the OFF-time
becomes equal to the voltage drop across parasitic components (typically the DCR of the
inductor and the R
the voltage applied at the inductor is maximized and is approximately equal to V
In general, the worst case scenario is heavy short-circuit at the output with maximum input
voltage.
Equation 43
considering T
Equation 44
where T
At higher input voltage I
escalate. As a consequence, the system typically meets
higher than the nominal value thanks to the increased voltage drop across stray
components. In most of the application conditions the pulse-by-pulse current limitation is
effective to limit the inductor current. Whenever the current escalates, a second level current
protection called “Hiccup mode” is enabled. Hiccup protection offers an additional protection
against heavy short-circuit conditions at very high input voltage even considering the spread
I
I
L TOFF
L TON
I
I
I
ON phase
OFF phase
L TON
L TON
L TON
Equation 40
SW
Equation 40
=
=
=
=
=
=1/f
V
------------------------------------------------------------------------------------------------------- T
L
–
------------------------------------------------------------------- - T
–
---------------------------------------------------------------------------------------------- - T
V
------------------------------------------------------------------------------ - T
IN
is the series resistance of the inductor.
ON
IN
DCR
V
I
L TOFF
SW
–
OUT
–
V
which has already been reduced to its minimum.
DCR
OUT
L
and
DSON
and considering the nominal f
+
+
R
and
L
DCR
–
L
DSON LS
Equation 41
+
DCR
L
of the low-side switch) since VOUT is negligible, while during T
R
L TON
Equation 41
DSON HS
L
L
L
+
L
R
+
Doc ID 023432 Rev 3
DSON LS
R
may be higher than I
DSON HS
I
SW
it can be seen that the implementation of the constant
I
–
in overcurrent conditions can be simplified to:
ON MIN
90ns
I
I
OFF
ON
–
------------------------------------------------------------------- - 1.18 s
V
--------- 90ns
SW
L
DCR
IN
.
L
L TOFF
+
R
OUT
L
Equation 42
DSON LS
and so the inductor current can
and the higher the V
Application information
I
at a current level
IN
IN
.
.
29/40
ON