参数资料
型号: LM2595ATPBCKGEVB
厂商: ON Semiconductor
文件页数: 8/25页
文件大小: 0K
描述: EVAL BOARD FOR LM2595ATPBCKG
设计资源: LM2595ATPBCKGEVB BOM
LM2595ATPBCKGEVB Gerber Files
LM2595ATPBCKGEVB Schematic
特色产品: Evaluation Boards & Kits
标准包装: 1
主要目的: DC/DC,步降
输出及类型: 1,非隔离
输出电压: 5V
电流 - 输出: 1A
输入电压: 4.5 ~ 40 V
稳压器拓扑结构: 降压
频率 - 开关: 150kHz
板类型: 完全填充
已供物品:
已用 IC / 零件: LM2595
其它名称: LM2595ATPBCKGEVBOS
LM2595
PCB LAYOUT GUIDELINES
As in any switching regulator, the layout of the printed
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 voltage transients which can generate
electromagnetic interferences (EMI) and affect the desired
operation. As indicated in the Figure 16, to minimize
inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.
For best results, single ? point grounding (as indicated) or
On the other hand, the PCB area connected to the Pin 1
(emitter of the internal switch) of the LM2595 should be
kept to a minimum in order to minimize coupling to sensitive
circuitry.
Another sensitive part of the circuit is the feedback. It is
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
LM2595 regulator.
ground plane construction should be used.
DESIGN PROCEDURE
I L(on) +
d + on , where T is the period of switching.
d + out
Buck Converter Basics
The LM2595 is a “Buck” or Step ? Down Converter which
is the most elementary forward ? mode converter. Its basic
schematic can be seen in Figure 17.
The operation of this regulator topology has two distinct
time periods. The first one occurs when the series switch is
on, the input voltage is connected to the input of the inductor.
The output of the inductor is the output voltage, and the
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:
V IN * V OUT t on
L
During this “on” period, energy is stored within the core
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.
This period ends when the power switch is once again
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:
t
T
For the buck converter with ideal components, the duty
cycle can also be described as:
V
V in
Figure 18 shows the buck converter, idealized waveforms
of the catch diode voltage and the inductor current.
V on(SW)
Power
Switch
L
Power
Switch
Off
Power
Switch
On
Power
Switch
Off
Power
Switch
On
V D (FWD)
V in
D
C out
R Load
Time
Figure 17. Basic Buck Converter
The next period is the “off” period of the power switch.
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:
I pk
I Load (AV)
I min
Power Power
Diode Switch Diode Switch
Time
Figure 18. Buck Converter Idealized Waveforms
I L(off) +
V OUT * V D t off
L
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