LED5000PHR STMicroelectronics, LED5000PHR Datasheet - Page 35

• 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

LED5000
Since the maximum operating voltage of the LED5000 is 48 V, according to
maximum input voltage of the application is 48-18.7=29.3 V
The output voltage is given by:
Equation 52
where the ideal duty cycle D
Equation 53
However, due to power losses (mainly switching and conduction losses), the real duty cycle
is always higher than this. The real value (which can be measured in the application) should
be used in the following formulas.
The peak current flowing in the embedded switch is:
Equation 54
while its average current level is equal to:
Equation 55
This is due to the fact that the current flowing through the internal power switch is delivered
to the output only during the OFF phase.
The switch peak current must be lower than the minimum current limit of the overcurrent
protection (see
current must be lower than the rated DC current of the device.
As a consequence, the maximum output current is:
Equation 56
where I
The current capability is reduced by the term (1-D
cycle of 0.5, and considering an average current through the switch of 3 A, the maximum
output current deliverable to the load is 1.5 A.
The
buck-boost topology. The input voltage ranges from 10 to 26 V and it can drive a string
composed of 10 LEDs with1 A DC.
Figure 24
SW MAX
shows the schematic circuit for an LED current source based on inverting
represents the rated current of the device.
Section Table 5.: Electrical characteristics
I
SW
=
-------------------------- -
1 D
IDEAL
–
I
LOAD
Doc ID 023951 Rev 1
I
LOAD MAX
REAL
V
for the buck-boost converter is:
OUT
D
+
IDEAL
I
SW
I
------------------- -
RIPPLE
=
I
2
–
SW MAX
=
V
=
IN
-------------------------- -
1 D
----------------------------- -
V
–
I
=
IN
LOAD
Application notes - alternative topologies
–
----------------------------
1 D
V
-------------------------- -
1 D
REAL
–
REAL
D
–
OUT
–
V
I
LOAD
IDEAL
1 D
OUT
IDEAL
–
REAL
) and so, for example, with a duty
REAL
for details) while the average
+
-------------
2
V
IN
L
---------
f
SW
D
Equation 51
35/51
the