LED5000PHR STMicroelectronics, LED5000PHR Datasheet - Page 38

• 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 - alternative topologies
6.2
38/51
Positive buck-boost
Positive buck-boost fits those applications that require a buck-boost topology (i.e. the input
voltage range crosses the output voltage value) and where the inverting buck-boost is not
suitable because of the main constraints for the final application (refer to
consequence the inverting buck-boost is the preferred option because it requires less
components and it has higher efficiency compared to the positive buck-boost topology.
Figure 28. Positive buck-boost
The positive buck-boost implementation (
external power switch than inverting buck-boost. The device is not floating, referred to GND,
and it is supplied with the input voltage of the application (the input voltage in inverting buck-
boost topology is instead V
the output voltage during the switching activity so V
input voltage.
The equations for the positive buck-boost are similar to those seen for the inverting.
Equation 58
where the ideal duty cycle D
Equation 59
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 60
while its average current level is equal to:
V
IN
I
SW
I
SW
=
IN
-------------------------- -
1 D
IDEAL
–
-V
I
LOAD
Doc ID 023951 Rev 1
OUT
REAL
V
for the buck-boost converter is:
, refer to
OUT
D
V
+
IDEAL
REF
I
------------------- -
RIPPLE
=
Figure 28
2
V
=
IN
Chapter 6.1
----------------------------- -
V
=
IN
----------------------------
1 D
V
-------------------------- -
1 D
+
D
–
OUT
–
) requires one more diode and an
V
I
IDEAL
OUT
LOAD
OUT
IDEAL
REAL
can be higher than the maximum
for details). LED5000 does not see
+
-------------
2
V
IN
L
---------
f
SW
D
Chapter 6.1
LED5000
AM13512v1
). As a