參數(shù)資料
型號(hào)： LTC3806EDE
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： Synchronous Flyback DC/DC Controller
中文描述： 0.05 A SWITCHING CONTROLLER, 290 kHz SWITCHING FREQ-MAX, PDSO12
封裝： 4 X 3 MM, PLASTIC, MO-229WGED, DFN-12
文件頁(yè)數(shù)： 13/20頁(yè)
文件大?。?/td> 241K
代理商： LTC3806EDE
13
LTC3806
3806f
For a minimum input voltage of 36V, the largest duty factor
is:
V
V
+
3 3
15
D
V
MAX
=
=
3 3
.
36
0 579
.
.
and the minimum percentage ripple is:
X
V
D
f L
P
V
kHz
H
W
MIN
IN
MAX
IN
36
P
=
=
μ
=
2
2
2
2
0 579
250
757
11 34
.
20. %
Transformer Core Selection
Once L
P
is known, the type of transformer must be selected.
High efficiency converters generally cannot afford the core
loss found in low cost powdered iron cores, forcing the use
of more expensive ferrite cores. Actual core loss is inde-
pendent of core size for a fixed inductance, but is very
dependent on the inductance selected. As inductance in-
creases, core losses go down. Unfortunately, increased
inductance requires more turns of wire and therefore cop-
per losses will increase. Generally, there is a tradeoff be-
tween core losses and copper losses that needs to be
balanced. In addition, increased winding resistance will
degrade cross regulation.
Ferrite designs have very low core losses and are preferred
at high switching frequencies, so design goals can con-
centrate on copper losses and preventing saturation.
Ferrite core material saturates “hard,” meaning that the
inductance collapses rapidly when the peak design current
is exceeded. This results in an abrupt increase in inductor
ripple current and consequently, output voltage ripple.
Do
not allow the core to saturate!
The maximum peak
primary current occurs at minimum V
IN
:
I
P
V
D
X
PK
IN
)
IN MIN
(
MAX
MIN
2
=
+
1
Current Sense Resistor Selection
The control circuit limits the maximum voltage drop
across the sense resistor to about 120mV (at low duty
cycle), and only about 70mV at a duty cycle of 92% due to
slope compensation. Use Figure 4 and D
MAX
to determine
the maximum allowable drop in the sense resistor. Using
this value calculate:
R
V
I
SENSE
DROP
PK
≤
APPLICATIOU
W
U
U
DUTY CYCLE
0
M
100
150
0.8
3806 F04
50
0
0.2
0.4
0.5
1.0
200
T
A
= 25
°
C
Figure 4. Maximum SENSE Threshold Voltage vs Duty Cycle
Capacitor Selection
In a flyback converter, the input and output current flows
in pulses placing severe demands on the input and output
filter capacitors. The input and output filter capacitors
should be selected based on RMS current ratings and
ripple voltage.
Select an input capacitor with a ripple current rating
greater than:
I
P
V
D
D
RMS
IN
(
IN MIN
MAX
MAX
=
)
–
1
Continuing the example:
I
W
V
A
RMS
RMS
=
=
11 34
36
1 0 579
0 579
.
0 269
.
.
– .
Low effective series resistance and inductance is also
important in the input capacitor since it affects the electro-
magnetic interference suppression. In some instances
high ESR can also produce stability problems because
flyback converters exhibit a negative input resistance
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3806EDE#PBF 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3806EDE#TR 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3806EDE#TRPBF 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3808EDE 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Step Down 2.75V to 9.8V Input 14-Pin DFN EP
LTC3808EDE#PBF 功能描述:IC REG CTRLR BUCK PWM CM 14-DFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
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