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参数资料
| 型号： | LT3748HMS#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/30页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO CM 16MSOP |
| 产品培训模块： | LT3748 100V Flyback Controller |
| 标准包装： | 37 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 电源电压： | 5 V ~ 100 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 150°C |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm），12 引线 |
| 包装： | 管件 |
| 配用： | 732-3308-ND - BOARD EVAL FOR LT3748 732-3305-ND - BOARD EVAL FOR LT3748 |
| 相关产品： | 732-2669-2-ND - TRANS FLYBACK LT3748 20UH SMD 732-2669-6-ND - TRANS FLYBACK LT3748 20UH SMD 732-2668-6-ND - TRANS FLYBACK LT3748 14UH SMD 732-2667-6-ND - TRANS FLYBACK LT3748 500UH SMD 732-2666-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2665-6-ND - TRANS FLYBACK LT3748 12UH SMD 732-2664-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2663-6-ND - TRANS FLYBACK LT3748 15UH SMD 732-2662-6-ND - TRANS FLYBACK LT3748 8UH SMD 732-2661-6-ND - TRANS FLYBACK LT3748 8UH SMD 更多... |
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LT3748
APPLICATIONS INFORMATION
Soft-Start
The LT3748 contains an optional soft-start function that
is enabled by connecting an explicit external capacitor
between the SS pin and ground. Internal circuitry prevents
the control voltage at the V C pin from exceeding that on
the SS pin.
The soft-start function is engaged whenever power at
V IN is removed, or as a result of either undervoltage
lockout, overcurrent in the sense resistor or thermal
(overtemperature) shutdown. The SS node is then
discharged to roughly 600mV. When this condition is
removed, a nominal 5μA current acts to charge up the SS
node towards roughly 2.2V. For example, a 0.1μF soft-start
capacitor will place a 0.05V/ms limit on the turn-on ramp
rate at the V C node.
ENABLE and Undervoltage Lockout (UVLO)
A resistive divider from V IN to the EN/UVLO pin implements
undervoltage lockout (UVLO). The EN/UVLO pin threshold
is set at 1.223V. In addition, the EN/UVLO pin draws 2.4μA
when the voltage at the pin is below 1.223V. This current
provides user programmable hysteresis based on the value
of R1. The effective UVLO thresholds are:
Minimum Load Requirement
The LT3748 recovers output voltage information using
the flyback pulse that occurs once the external MOSFET
turns off and the secondary winding conducts current. In
order to regulate the output voltage, the LT3748 needs to
sample the flyback pulse. The LT3748 delivers a minimum
amount of energy even during light load conditions to
ensure accurate output voltage information. The minimum
delivery of energy creates a minimum load requirement
on the output of approximately 2% of maximum load.
The minimum operating frequency at minimum load is
approximately 42kHz.
Alternatively, a Zener diode sufficiently rated to handle the
minimum load power can be used to provide a minimum
load without decreasing efficiency in normal operation. In
selecting a Zener diode for this purpose, the Zener voltage
should be high enough that the diode does not become the
load path during transient conditions but the voltage must
still be low enough that the MOSFET and output voltage
ratings are not exceeded when the Zener functions as the
minimum load.
INTV CC Pin Considerations
V IN(UVLO,RISING) =
1.223V ? (R1 + R2)
R2
+ 2.4μA ? R1
The INTV CC pin powers the internal circuitry and gate
driver of the LT3748. Three unique configurations exist
for regulation of the INTV CC pin as shown in Figure 11.
V IN(UVLO,FALLING) =
1.223V ? (R1 + R2)
R2
In the first configuration, the internal LDO drives the
INTV CC pin internally from the V IN supply. In the second
configuration, the V IN supply directly drives the INTV CC
Figure 10 shows the implementation of external shutdown
control while still using the UVLO function. The NMOS
grounds the EN/UVLO pin when turned on, and puts the
LT3748 in shutdown with a quiescent current draw of
less than 1μA.
pin through a direct connection bypassing the internal
LDO. Use this optional configuration for voltages lower
than 20V. In the third configuration, an external supply or
third winding drives the INTV CC pin. Use this option when
a voltage supply exists lower than the input supply but
EN/UVLO
V IN
R1
higher than the regulated INTV CC voltage. Using a lower
voltage supply provides a more efficient source of power
for internal circuitry and reduces power dissipation in
the LT3748.
LT3748
GND
R2
RUN/STOP
CONTROL
(OPTIONAL)
When calculating the minimum input voltage required for
a valid INTV CC , or the power dissipated in the LT3748, it is
useful to know how much current will be drawn from the
3748 F10
Figure 10. Undervoltage Lockout (UVLO)
INTV CC LDO during normal operation. The easiest way to
calculate this current is to use the gate charge (Q G ) for the
3748fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3748HMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748IMS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT3748IMS#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LT3748IMSPBF | 制造商:Linear Technology 功能描述:100V Isolated Flyback Controller MSOP16 |
| LT3748IMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
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