LM5022LEDEVAL National Semiconductor, LM5022LEDEVAL Datasheet - Page 17

• Manufacturer Part Number: LM5022LEDEVAL
• Description: BOARD EVALUATION FOR LM5022
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM5022LEDEVAL

• Current - Output / Channel: 1A
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 40V
• Features: Dimmable
• Voltage - Input: 10 ~ 14V
• Utilized Ic / Part: LM5022
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

12. Plot or evaluate the complete control loop transfer
function: The complete control loop transfer function is ob-
tained by multiplying the power stage and error amplifier
functions together. The bandwidth and phase margin can
then be read graphically or evaluated numerically.
FIGURE 9. Error Amplifier Gain and Phase
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The bandwidth of this example circuit at V
with a phase margin of 66°.
13. Re-evaluate at the corners of input voltage and output
current: Boost converters exhibit significant change in their
loop response when V
tion fixed, the total control loop gain and phase should be
checked to ensure a minimum phase margin of 45° over both
line and load.
Efficiency Calculations
A reasonable estimation for the efficiency of a boost regulator
controlled by the LM5022 can be obtained by adding together
the loss is each current carrying element and using the equa-
tion:
The following shows an efficiency calculation to complement
the circuit design from the Design Considerations section.
Output power for this circuit is 40V x 0.5A = 20W. Input voltage
is assumed to be 13.8V, and the calculations used assume
that the converter runs in CCM. Duty cycle for V
66%, and the average inductor current is 1.5A.
CHIP OPERATING LOSS
This term accounts for the current drawn at the VIN pin. This
current, I
The gate driving loss term from the power MOSFET section
of Design Considerations is included in the chip operating
loss. For the LM5022, I
current, I
lost as this current passes through the internal linear regulator
of the LM5022.
I
tics table. Chip Operating Loss is then:
CC
is typically 3.5 mA, taken from the Electrical Characteris-
FIGURE 10. Overall Loop Gain and Phase
IN
CC
, drives the logic circuitry and the power MOSFETs.
, plus the MOSFET driving current, I
I
GC
= 27 nC x 500 kHz = 13.5 mA
P
Q
IN
IN
I
= V
GC
is equal to the steady state operating
and I
= Q
IN
X (I
O
G
change. With the compensa-
X f
Q
+ I
SW
GC
)
IN
= 16V is 10.5 kHz,
IN
GC
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= 13.8V is
. Power is