参数资料
型号: LTC3642IDD-3.3#PBF
厂商: Linear Technology
文件页数: 16/22页
文件大小: 0K
描述: IC REG BUCK SYNC 3.3V 50MA 8DFN
标准包装: 121
类型: 降压(降压)
输出类型: 固定
输出数: 1
输出电压: 3.3V
输入电压: 4.5 V ~ 45 V
PWM 型: Burst Mode?
电流 - 输出: 50mA
同步整流器:
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 8-WFDFN 裸露焊盘
包装: 管件
供应商设备封装: 8-DFN-EP(3x3)
LTC3642
APPLICATIONS INFORMATION
The undervoltage lockout requirement on V IN can be
satisfied with a resistive divider from V IN to the RUN and
HYST pins. Choose R1 = 2M and calculate R2 and R3 as
follows:
3. Keep the switching node, SW, away from all sensitive
small signal nodes. The rapid transitions on the switching
node can couple to high impedance nodes, in particular
V FB , and create increased output ripple.
1.21V
V IN(RISING) – 1.21V ? ?
1.1V
V IN(FALLING) – 1.1V ? ?
?
R2 = ??
?
?
R3 = ??
?
?
? ? R1 = 224k
?
? ? R1 – R2 = 90.8k
4. Flood all unused area on all layers with copper. Flooding
with copper will reduce the temperature rise of power
components. You can connect the copper areas to any
DC net (V IN , V OUT , GND or any other DC rail in your
system).
Choose standard values for R2 = 226k and R3 = 91k. The
I SET pin should be left open in this example to select maxi-
mum peak current (115mA). Figure 9 shows a complete
schematic for this design example.
V IN
C IN
2
5
7
4
V IN SW
LTC3642
HYST
SS I SET
RUN V FB
1
6
3
L1
R1
R2
V OUT
C OUT
V IN
24V
1μF
2M
V IN SW
LTC3642
RUN I SET
100μH
V OUT
3.3V
50mA
10μF
C SS
GND
8, 9
R SET
3642 F10a
226k
SS
750k
91k
HYST
GND
V FB
240k
L1
3642 F09
V IN
C IN
C OUT
V OUT
Figure 9. 24V to 3.3V, 50mA Regulator at 250kHz
PC Board Layout Checklist
R1
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3642. Check the following in your layout:
R SET
C SS
GND
R2
1. Large switched currents flow in the power switches
and input capacitor. The loop formed by these compo-
nents should be as small as possible. A ground plane
is recommended to minimize ground impedance.
2. Connect the (+) terminal of the input capacitor, C IN , as
close as possible to the V IN pin. This capacitor provides
the AC current into the internal power MOSFETs.
VIAS TO GROUND PLANE
VIAS TO INPUT SUPPLY (V IN )
OUTLINE OF LOCAL GROUND PLANE
Figure 10. Layout Example
3642 F10b
3642fc
16
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