LM2596DSADJG ON Semiconductor, LM2596DSADJG Datasheet - Page 8

• Manufacturer Part Number: LM2596DSADJG
• Description: IC REG SW STP-DWN 3A D2PAK-5
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of LM2596DSADJG

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.23 ~ 37 V
• Current - Output: 3A
• Frequency - Switching: 150kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: D²Pak, TO-263 (5 leads + tab)
• Output Voltage: 1.23 V to 37 V
• Output Current: 3 A
• Input Voltage: 4.5 V to 40 V
• Switching Frequency: 150 KHz
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 95 %
• Isolated/non-isolated: Non Isolated
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

circuit board is very important. Rapidly switching currents
associated with wiring inductance, stray capacitance and
parasitic inductance of the printed circuit board traces can
generate
electromagnetic interferences (EMI) and affect the desired
operation. As indicated in the Figure 15, to minimize
inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.
ground plane construction should be used.
Buck Converter Basics
is the most elementary forward−mode converter. Its basic
schematic can be seen in Figure 16.
time periods. The first one occurs when the series switch is
on, the input voltage is connected to the input of the inductor.
rectifier (or catch diode) is reverse biased. During this
period, since there is a constant voltage source connected
across the inductor, the inductor current begins to linearly
ramp upwards, as described by the following equation:
material in the form of magnetic flux. If the inductor is
properly designed, there is sufficient energy stored to carry
the requirements of the load during the “off” period.
When the power switch turns off, the voltage across the
inductor reverses its polarity and is clamped at one diode
voltage drop below ground by the catch diode. The current
now flows through the catch diode thus maintaining the load
current loop. This removes the stored energy from the
inductor. The inductor current during this time is:
As in any switching regulator, the layout of the printed
For best results, single−point grounding (as indicated) or
The LM2596 is a “Buck” or Step−Down Converter which
The operation of this regulator topology has two distinct
The output of the inductor is the output voltage, and the
During this “on” period, energy is stored within the core
The next period is the “off” period of the power switch.
V
in
voltage
Switch
Power
Figure 16. Basic Buck Converter
I
I
L(on)
L(off)
transients
+
+
D
V
V
IN
OUT
* V
* V
L
L
OUT
L
which
D
t
t
off
on
C
out
can
PCB LAYOUT GUIDELINES
DESIGN PROCEDURE
generate
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R
Load
8
(emitter of the internal switch) of the LM2596 should be
kept to a minimum in order to minimize coupling to sensitive
circuitry.
important to keep the sensitive feedback wiring short. To
assure this, physically locate the programming resistors near
to the regulator, when using the adjustable version of the
LM2596 regulator.
turned on. Regulation of the converter is accomplished by
varying the duty cycle of the power switch. It is possible to
describe the duty cycle as follows:
cycle can also be described as:
of the catch diode voltage and the inductor current.
On the other hand, the PCB area connected to the Pin 2
Another sensitive part of the circuit is the feedback. It is
This period ends when the power switch is once again
For the buck converter with ideal components, the duty
Figure 17 shows the buck converter, idealized waveforms
d +
Figure 17. Buck Converter Idealized Waveforms
I
t on
Switch
V
Power
min
Diode
T
D
Off
(FWD)
, where T is the period of switching.
V
on(SW)
Switch
Power
Switch
Power
On
d +
Power
Switch
Diode
Off
V out
V in
I
pk
Power
Switch
Power
Switch
On
I
Load
Time
Time
(AV)