LM2575SX-ADJ National Semiconductor, LM2575SX-ADJ Datasheet - Page 13

• Manufacturer Part Number: LM2575SX-ADJ
• Description: IC,SMPS CONTROLLER,VOLTAGE-MODE,BIPOLAR,SIP,5PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM2575SX-ADJ

• Rohs Compliant: NO

INDUCTOR VALUE SELECTION GUIDES
Given:
V
V
I
F = Switching Frequency (Fixed at 52 kHz)
1. Programming Output Voltage (Selecting R1 and R2, as
shown in Figure 2 )
Use the following formula to select the appropriate resistor
values.
R
cient and stability with time, use 1% metal film resistors)
2. Inductor Selection (L1)
A. Calculate the inductor Volt • microsecond constant,
E • T (V • µs), from the following formula:
B. Use the E • T value from the previous formula and match
it with the E • T number on the vertical axis of the Inductor
Value Selection Guide shown in Figure 7 .
C. On the horizontal axis, select the maximum load current.
D. Identify the inductance region intersected by the E • T
value and the maximum load current value, and note the
inductor code for that region.
E. Identify the inductor value from the inductor code, and
select an appropriate inductor from the table shown in Figure
9 . Part numbers are listed for three inductor manufacturers.
The inductor chosen must be rated for operation at the
LM2575 switching frequency (52 kHz) and for a current rating
of 1.15 x I
inductor section in the application hints section of this data
sheet.
LOAD
OUT
IN
1
PROCEDURE (Adjustable Output Voltage Versions)
(Max) = Maximum Input Voltage
can be between 1k and 5k. (For best temperature coeffi-
(Max) = Maximum Load Current
= Regulated Output Voltage
LOAD
. For additional inductor information, see the
13
Given:
V
V
I
F = 52 kHz
1.Programming Output Voltage (Selecting R1 and R2)
R2 = 1k (8.13 − 1) = 7.13k, closest 1% value is 7.15k
2. Inductor Selection (L1)
A. Calculate E • T (V • µs)
B. E • T = 115 V • µs
C. I
D. Inductance Region = H470
E. Inductor Value = 470 µH Choose from AIE part # 430-0634,
Pulse Engineering part # PE-53118, or Renco part
# RL-1961.
LOAD
OUT
IN
(For Continuous Mode Operation) (Continued)
(Max) = 25V
LOAD
EXAMPLE (Adjustable Output Voltage Versions)
(Max) = 1A
= 10V
(Max) = 1A
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