LED5000PHR STMicroelectronics, LED5000PHR Datasheet - Page 30

• Manufacturer Part Number: LED5000PHR
• Description: Current & Power Monitors & Regulators 3A monolithic Conv 850kHz Synch
• Manufacturer: STMicroelectronics

Specifications of LED5000PHR

• Rohs: yes
• Product: Current Regulators
• Supply Voltage - Max: 48 V
• Supply Voltage - Min: 5.5 V
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Package / Case: HPSO-8
• Accuracy: +/- 3 %
• Input Voltage Range: 5.5 V to 48 V
• Output Current: 23 uA
• Sensing Method: High or Low Side
• Supply Current: 1.7 mA

Application notes - buck conversion
30/51
Equation 45
where DCR
drop across the external rectifying diode.
The pulse-by-pulse current limitation is effective to implement constant current protection
when:
Equation 46
From
current protection becomes more critical the lower is 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 forward voltage of the diode) since V
voltage applied the inductor is maximized and it is approximately equal to V
In general the worst case scenario is heavy short-circuit at the output with maximum input
voltage. The
Equation 47
considering T
Equation 48
where T
At high input voltage I
escalate. As a consequence, the system typically meets the
higher than the nominal value thanks to the increased voltage drop across stray
components. In most 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. The hiccup protection offers an additional
protection against heavy short-circuit condition at very high input voltage even considering
the spread of the minimum conduction time of the power element. In case the hiccup current
level (6.2 A typical) is triggered the switching activity is prevented for 16 msec typ. (see
hiccup time in
Figure 19
applied at the output at the maximum input voltage.
Equation 44
I
L TOFF
SW
shows the operation of the constant current protection when a short-circuit is
=1/f
L
Equation 44
is the series resistance of the inductor and V
ON
=
Table 5: Electrical characteristics
SW
–
------------------------------------------------------------------ - T
that has been already reduced to its minimum.
DCR
and
considering the nominal f
I
L TON
Equation 45
L TON
L
I
L TON
=
and
I
V
-------------------------------------------------------------------------- - T
L
+
IN
could be higher than I
V
Doc ID 023951 Rev 1
=
Equation 45
–
FW DIODE
–
---------------------------------------------------------------------------------------- T
DCR
V
OUT
we can gather that the implementation of the constant
L
I
L TON
+
L
+
R
DCR
DSON HS
SW
in overcurrent conditions can be simplified to:
SW
=
–
L
90ns
.
L
).
I
L TOFF
I
+
L TOFF
V
I
OUT
FW DIODE
–
------------------------------------------------------------------ - 1.18 s
ON MIN
DCR
is negligible, while during T
FWDIODE
OUT
and so the inductor current could
Equation 46
L
and the higher is V
V
-------- - 90ns
I
OFF
L
L
+
IN
is the forward voltage
V
FW DIODE
at a current level
IN
.
IN
LED5000
.
ON
the