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参数资料
| 型号： | LT3825EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO 16-TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 88% |
| 电源电压： | 11 V ~ 18 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 ~ 125°C |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LT3825
APPLICATIONS INFORMATION
I SC ? ( R SEC + R DS(ON) )
DC MIN = t ON(MIN) ? f OSC <
duringthecurrentcomparatorsenseaction(currentmode
switching).
AN19 provides a method for empirically tweaking frequency
compensation. Basically it involves introducing a load
current step and monitoring the response.
Slope Compensation
This part incorporates current slope compensation. Slope
compensation is required to ensure current loop stability
when the DC is greater than 50%. In some switcher con-
trollers, slope compensation reduces the maximum peak
current at higher duty cycles. The LT3825 eliminates this
problem by having circuitry that compensates for the slope
compensation so that maximum current sense voltage is
constant across all duty cycles.
Minimum Load Considerations
At light loads, the LT3825 derived regulator goes into
forced continuous conduction mode. The primary-side
switch always turns on for a short time as set by the
t ON(MIN) resistor. If this produces more power than the
load requires, power will flow back into the primary during
the “off” period when the synchronization switch is on.
This does not produce any inherently adverse problems,
though light load efficiency is reduced.
Maximum Load Considerations
The current mode control uses the V C node voltage and
amplified sense resistor voltage as inputs to the current
comparator. When the amplified sense voltage exceeds
the V C node voltage, the primary-side switch is turned off.
In normal use, the peak switch current increases while
FB is below the internal reference. This continues until
V C reaches its 2.56V clamp. At clamp, the primary-side
MOSFET will turn off at the rated 98mV V SENSE level. This
repeats on the next cycle.
It is possible for the peak primary switch currents as
referred across R SENSE to exceed the max 98mV rating
because of the minimum switch-on time blanking. If the
voltage on V SENSE exceeds 206mV after the minimum
turn-on time, the SFST capacitor is discharged, causing
the discharge of the V C capacitor. This then reduces the
peak current on the next cycle and will reduce overall
stress in the primary switch.
Short-Circuit Conditions
Loss of current limit is possible under certain conditions
such as an output short circuit. If the duty cycle exhib-
ited by the minimum on time is greater than the ratio of
secondary winding voltage (referred-to-primary) divided
by input voltage, then peak current is not controlled at
the nominal value. It ratchets up cycle-by-cycle to some
higher level. Expressed mathematically, the requirement
to maintain short-circuit control is:
V IN ? N SP
where:
t ON(MIN) = primary-side switch minimum on-time
I SC = short-circuit output current
NSP = secondary-to-primary turns ratio (N SEC /N PRI )
Other variables as previously defined
Trouble is typically encountered only in applications with a
relatively high product of input voltage times secondary-
to-primary turns ratio and/or a relatively long minimum
switch on time. Additionally, several real world effects such
as transformer leakage inductance, AC winding losses, and
output switch voltage drop combine to make this simple
theoretical calculation a conservative estimate. Prudent
design evaluates the switcher for short-circuit protection
and adds any additional circuitry to prevent destruction.
3825fe
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT382B | 制造商:EDSYN 功能描述:TIP CONICAL 0.5X15.8MM |
| LT383 | 制造商:EDSYN 功能描述: |
| LT3837 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low VIN, 8A DC/DC μModule Regulator |
| LT3837EFE | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin TSSOP EP |
| LT3837EFE#PBF | 功能描述:IC REG CTRLR FLYBK ISO 16-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
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