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| 型号： | LT3512EMS#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/26页 |
| 文件大小： | 0K |
| 描述： | IC REG FLYBK ISO ADJ .42A 16MSOP |
| 标准包装： | 37 |
| 类型： | 回扫，隔离 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调 |
| 输入电压： | 4.5 V ~ 100 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 40kHz ~ 650kHz |
| 电流 - 输出： | 420mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm），12 引线 |
| 包装： | 管件 |
| 供应商设备封装： | 16-MSOP |
LT3512
APPLICATIONS INFORMATION
APPLICATION DESIGN CONSIDERATIONS
Iterative Design Process
The LT3512 uses a unique sampling scheme to regulate
the isolated output voltage. The use of this isolated scheme
requires a simple iterative process to choose feedback
resistors and temperature compensation. Feedback re-
sistor values and temperature compensation resistance
is heavily dependent on the application, transformer and
output diode chosen.
Once resistor values are fixed after iteration, the values
will produce consistent output voltages with the chosen
transformer and output diode. Remember, the turns ratio
of the transformer must be guaranteed within ±1%. The
transformer vendors mentioned in this data sheet can
build transformers to this specification.
Selecting R FB and R REF Resistor Values
Strictly speaking, the above equation defines R FB not as an
absolute value, but as a ratio of R REF . So the next question
is, what is the proper value for R REF ? The answer is that
R REF should be approximately 10k. The LT3512 is trimmed
and specified using this value of R REF . If the impedance of
R REF varies considerably from 10k, additional errors will
result. However, a variation in R REF of several percent is
acceptable. This yields a bit of freedom in selecting stan-
dard 1% resistor values to yield nominal R FB /R REF ratios.
Undervoltage Lockout (UVLO)
A resistive divider from V IN to the EN/UVLO pin imple-
ments undervoltage lockout (UVLO). Figure 7 shows this
configuration. The EN/UVLO pin threshold is set at 1.21V.
V IN
R1
EN/UVLO
The following section provides an equation for setting
R FB and R REF values. The equation should only serve
as a guide. Follow the procedure outlined in the Design
Procedure to set accurate values for R FB , R REF and R TC
using the iterative design procedure.
LT3512
GND
R2
3512 F07
RUN/STOP
CONTROL
(OPTIONAL)
R REF ? N PS ?? ( V OUT + V F ) + V TC ??
R FB =
V IN(UVLO,RISING) =
+ 2.6μA ? R1
V IN(UVLO,FALLING) =
R TC =
RearrangementoftheexpressionforV OUT intheTempera-
ture Compensation section, developed in the Operations
section, yields the following expression for R FB :
V BG
where:
V OUT = Output voltage
V F = Switching diode forward voltage
N PS = Effective primary-to-secondary turns ratio
V TC = 0.55V
This equation assumes:
R FB
N PS
The equation assumes the temperature coefficients of
the diode and V TC are equal, which is a good first order
approximation.
14
Figure 7. Undervoltage Lockout (UVLO)
In addition, the EN/UVLO pin draws 2.6μA when the volt-
age at the pin is below 1.21V. This current provides user
programmable hysteresis based on the value of R1. The
effective UVLO thresholds are:
1.2V ? (R1 + R2)
R2
1.2V ? (R1 + R2)
R2
Figure 7 also shows the implementation of external shut-
down control while still using the UVLO function. The
NMOS grounds the EN/UVLO pin when turned on, and
puts the LT3512 in shutdown with quiescent current draw
of less than 1μA.
Minimum Load Requirement
The LT3512 recovers output voltage information using the
flyback pulse. The flyback pulse occurs once the switch
turns off and the secondary winding conducts current. In
3512fb
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3512HMS#PBF | 功能描述:IC REG FLYBK ISO ADJ .42A 16MSOP RoHS:是 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 |
| LT3512HMS#TRPBF | 功能描述:IC REG FLYBK ISO ADJ .42A 16MSOP RoHS:是 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 |
| LT3512HMSPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic High Voltage Isolated Flyback Converter |
| LT3512IMS#PBF | 功能描述:IC REG FLYBK ISO ADJ .42A 16MSOP 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:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3512IMS#TRPBF | 功能描述:IC REG FLYBK ISO ADJ .42A 16MSOP RoHS:是 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 |
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