- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄374731 > SC4812STRT (Semtech Corporation) Current Mode PWM Controller with Integrated Start-up Circuit and Op Amp PDF資料下載
參數(shù)資料
| 型號： | SC4812STRT |
| 廠商： | Semtech Corporation |
| 英文描述： | Current Mode PWM Controller with Integrated Start-up Circuit and Op Amp |
| 中文描述： | 電流模式PWM控制器，帶有集成啟動電路和運算放大器 |
| 文件頁數(shù)： | 8/15頁 |
| 文件大小： | 219K |
| 代理商： | SC4812STRT |
8
2007 Semtech Corp.
www.semtech.com
SC4812
POWER MANAGEMENT
Applications Information (Cont.)
PCB Layout Guideline
PCB layout is very critical, and the following should be
considered to insure proper operation of the SC4812.
High switching currents are present in applications and
their effect on ground plane must be understood and
minimized.
1) The high power parts of the circuit should be placed
on a board first. A ground plane should be used. Isolated
or semi-isolated areas of the ground plane may be delib-
erately introduced to constrain ground currents to par-
ticular areas, for example the input capacitor and the
main switch FET ground.
2) The loop formed by the Input Capacitor(s) (Cin), the
main transformer and the main switch FET must be kept
as small as possible. This loop contains all the high fast
transient switching current. Connections should be as
wide and as short as possible to minimize loop induc-
tance. Minimizing this loop area will a) reduce EMI, b)
lower ground injection currents, resulting in electrically
“cleaner” grounds for the rest of the system and c)
minimize source ringing, resulting in more reliable gate
switching signals.
3) The connection between FETs and the main trans-
former should be a wide trace or copper region. It should
be as short as practical. Since this connection has fast
voltage transitions, keeping this connection short will
minimize EMI.
4) The output capacitor(s) (Cout) should be located as
close to the load as possible. Fast transient load cur-
rents are supplied by Cout only. Connections between
Cout and the load must be short, wide copper areas to
minimize inductance and resistance.
5) A 0.1uF to 1uF ceramic capacitor should be directly
connected between VCC and GND and a 1uF to 4.7uF.
The SC4812 is best placed over a quiet ground plane
area. Avoid pulse currents in the Cin and the main switch
FET loop flowing in this area. GND should be returned to
the ground plane close to the package and close to the
ground side of (one of) the VCC supply capacitor(s). Under
no circumstances should GND be returned to a ground
inside the Cin and the main switch FET loop. This can be
achieved by making a star connection between the quiet
GND planes that the SC4812 will be connected to and
the noisy high current GND planes connected to the FETs.
6) The feed back connection between the error ampli-
fier and the FB pin should be kept as short as possible,
and the GND connections should be to the quiet GND
used for the SC4812.
7) If an opto-coupler is used for isolation, quiet primary
and secondary ground planes should be used. The same
precautions should be followed for the primary GND plane
as mentioned in item 5. For the secondary GND plane,
the GND plane method mentioned in item 4 should be
followed.
8) All the noise sensitive components such as VCC by-
pass capacitor, COMP resistor/capacitor network, cur-
rent sensing circuitry and feedback circuitry should be
connected as close as possible to the SC4812. The GND
return should be connected to the quiet SC4812 GND
plane.
9) The connection from the OUT of the SC4812 should
be minimized to avoid any stray inductance. If the layout
can not be optimized due to constraints, a small Schottky
diode may be connected from the OUT pin to the ground
directly at the IC. This will clamp excessive negative volt-
ages at the IC.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC4820 | Push-Pull Controller for Isolated Power Supply(用于隔離電源的推挽控制器) |
| SC483 | Dual Synchronous Buck Pseudo Fixed Frequency Power Supply Controller |
| SC483ITSTRT | Dual Synchronous Buck Pseudo Fixed Frequency Power Supply Controller |
| SC486 | Complete DDR1/2/3 Memory Power Supply |
| SC486EVB | Complete DDR1/2/3 Memory Power Supply |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC4819 | 制造商:SEMS SCREWS 功能描述: |
| SC483 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Dual Synchronous Buck Pseudo Fixed Frequency Power Supply Controller |
| SC483ITSTRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Dual Synchronous Buck Pseudo Fixed Frequency Power Supply Controller |
| SC486 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Complete DDR1/2/3 Memory Power Supply |
| SC486EVB | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Complete DDR1/2/3 Memory Power Supply |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。