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参数资料
| 型号： | LT1765-1.8 |
| 厂商： | Linear Technology Corporation |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | Isolated Flyback Switching Regulator with 9V Output |
| 中文描述： | 隔离反激式开关稳压9V输出 |
| 文件页数： | 9/20页 |
| 文件大小： | 247K |
| 代理商： | LT1765-1.8 |
LT1765/LT1765-1.8/LT1765-2.5/
LT1765-3.3/LT1765-5
9
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INDUCTOR CHOICE AND MAXIMUM OUTPUT
CURRENT
Maximum output current for an LT1765 buck converter is
equal to the maximum switch rating (I
P
) minus one half
peak to peak inductor ripple current. The LT1765 maintains
a constant switch current rating at all duty cycles. (Patent
Pending)
For most applications, the output inductor will be in the
1
μ
H to 10
μ
H range. Lower values are chosen to reduce the
physical size of the inductor, higher values allow higher
output currents due to reduced peak to peak ripple current.
The following formula gives maximum output current for
continuous mode operation, implying that the peak to
peak ripple (2x the term on the right) is less than the
maximum switch current.
Figure 3. Output Ripple Voltage Waveform
V
USING 47
μ
F, 0.1
TANTALUM CAPACITOR
(10mV/DIV)
V
(5V/DIV)
V
USING 2.2
μ
F
CERAMIC CAPACITOR
(10mV/DIV)
0.2
μ
s/DIV
1765 F03
APPLICATIOU
W
U
U
I
OUT MAX
ContinuousMode
)
=
I
V
V
V
L f V
2
P
OUT
IN
OUT
)
IN
–(
)(
–
)
For V
IN
= 8V, V
OUT
= 5V and L = 3.3
μ
H,
I
A
OUT MAX
(
)
.
.
.
.
=
( )
(
)(
)
(
)
( )
=
=
3
5 8 5
2 3 3 10
1 25 10
8
3
0 23
2 77
6
6
Note that the worst case (minimum output current avail-
able) condition is at the maximum input voltage. For the
same circuit at 15V, maximum output current would be
only 2.6A.
Inductor Selection
The output inductor should have a saturation current
rating greater than the peak inductor current set by the
current comparator of the LT1765. The peak inductor
current will depend on the output current, input and output
voltages and the inductor value:
V
V
( )( )(
2
V
IN
= Maximum input voltage
f = Switching frequency, 1.25MHz
If an inductor with a peak current lower than the maximum
switch current of the LT1765 is chosen a soft-start circuit
in Figure 10 should be used. Also, short-circuit conditions
should not be allowed because the inductor may saturate
resulting in excessive power dissipation.
Also, consideration should be given to the resistance of
the inductor. Inductor conduction loses are directly pro-
portional to the DC resistance of inductor. Sometime, the
manufacturers will also provide maximum current rating
based on the allowable losses in the inductor. Care should
be taken, however. At high input voltages and low DCR,
excessive switch current could flow during shorted output
condition.
Suitable inductors are available from Coilcraft, Coiltronics,
Dale, Sumida, Toko, Murata, Panasonic and other
manufacturers.
I
I
V
PEAK
OUT
OUT
IN
OUT
)
IN
=
+
(
)
Table 2. Surface Mount Solid Tantalum Capacitor ESR
and Ripple Current
E Case Size
AVX TPS, Sprague 593D
AVX TAJ
D Case Size
AVX TPS, Sprague 593D
C Case Size
AVX TPS
ESR (Max,
)
0.1 to 0.3
0.7 to 0.9
Ripple Current (A)
0.7 to 1.1
0.4
0.1 to 0.3
0.7 to 1.1
0.2 (typ)
0.5 (typ)
Figure 3 shows a comparison of output ripple for a ceramic
and tantalum capacitor at 200mA ripple current.
相关PDF资料 |
PDF描述 |
|---|---|
| LT1765-3.3 | CONTACT |
| LT1765-5 | TERMINAL |
| LT1765 | Isolated Flyback Switching Regulator with 9V Output |
| LT1765-2.5 | Isolated Flyback Switching Regulator with 9V Output |
| LT1767-2.5 | Direct mounting on the PCB, Crimping connection, Discrete wire connectors; HRS No: 544-0063-6 00; No. of Positions: 15; Connector Type: Wire; Contact Gender: Male; Contact Spacing (mm): 2; Terminal Pitch (mm): 2; Termination Style: IDC; Current Rating(Amps)(Max.): 1; Contact Mating Area Plating: Tin; Operating Temperature Range (degrees C): -30 to 85; General Description: Housing; Straight; Direct PCB mounting; For AWG#26 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1765-2.5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 3A, 1.25MHz Step-Down Switching Regulator |
| LT1765-3.3 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 3A, 1.25MHz Step-Down Switching Regulator |
| LT1765-5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 3A, 1.25MHz Step-Down Switching Regulator |
| LT1765EFE | 功能描述:IC REG BUCK ADJ 3A 16TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1765EFE#PBF | 功能描述:IC REG BUCK ADJ 3A 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
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