LED5000PHR STMicroelectronics, LED5000PHR Datasheet - Page 44

• 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
6.4
44/51
Compensation network design for alternative topologies
The small signal analysis for the alternative topologies can be written as:
Equation 74
that shares similar terms with
addition K
(
Equation 75
The RHP (right half plane) zero has the same 20 dB/dec rising gain magnitude as a
conventional zero, but with 90 degree phase drop instead of lead. This characteristic cannot
be compensated with the error amplifier network so the loop gain is designed to roll off at
lower frequency in order to keep its contribution outside the small signal analysis.
the duty cycle. As a consequence the minimum
determines the maximum system bandwidth:
Equation 76
the system phase margin depends on K.
This paragraph provides the equations to calculate the components of the compensation
network once selected the power components and given the BW specification.
Table 10: BB and boost parameters
next calculations of the compensation network.
The DC gain of the total small loop is:
Equation 77
where G
the error amplifier, R
Table 5: Electrical characteristics
from
The calculation of the components composing the compensation network depends on the
relative position of the pole f
Equation 75
Z_RHP
Table 10
(see
m
DX
is the error amplifier transconductance, R
) is a zero in the right half plane:
Equation 75
depends on the topology (different for boost and buck-boost) and
G
CO
CS
s
the internal current sense gain (for these parameters refer to
=
) depends on the equivalent output resistance, inductor value and
R
----------------- -
R
LOAD
p
A
BW BW
CS
0
Doc ID 023951 Rev 1
(see
Equation 1
=
), R
G
Z_RHP
Equation 3
----------------- -
m
1 D
summarizes the K
K
MAX
S
–
Dx
the sensing resistor value, and K
R
=
EA
=
which is valid for the buck (see
R
-------------------------------------------
--- -
K
1
-------------------------------------------------------------
OUT
1
) and the designed bandwidth BW.
1 D
–
---------------------------- -
–
----------------- -
Z_RHP_MIN
Z_RHP
Z_RHP
L
2
s
1 D
1
EA
–
+
D
---------- -
R
R
-----
the equivalent output resistance of
, K
s
over the input voltage range
CS
p
S
2
«
m
1
f
-------- -
, K parameters useful for the
+
SW
------ -
K
6
1
---- -
D
s
z
F
H
s
D
Equation 1
can be calculated
Z_RHP
LED5000
). In