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参数资料
| 型号： | LTC1625IS |
| 厂商： | Linear Technology |
| 文件页数： | 15/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 165kHz |
| 占空比： | 99% |
| 电源电压： | 3.9 V ~ 36 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： | -40°C ~ 85°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
LTC1625
APPLICATIO N S I N FOR M ATIO N
(
)
t DELAY = ?
? 1 . 4 V ?
? C SS SS
V SEC ( MIN ) ? 1 . 19 V ? 1 + ?
= 0 . 5 s / μ F C
? 3 μ A ?
When the voltage on RUN/SS reaches 1.4V the LTC1625
begins operating with a clamp on I TH at 0.8V. As the
voltage on RUN/SS increases to approximately 3.1V, the
clamp on I TH is raised until its full 2.4V range is restored.
This takes an additional 0.5s/ μ F. During this time the load
current will be folded back to approximately 30mV/R DS(ON)
until the output reaches half of its final value.
Diode D1 in Figure 7 reduces the start delay while allowing
C SS to charge up slowly for the soft start function. This
diode and C SS can be deleted if soft start is not needed. The
RUN/SS pin has an internal 6V zener clamp (See Func-
tional Diagram).
then V SEC will droop. An external resistor divider from
V SEC to the FCB pin sets a minimum voltage V SEC(MIN) :
? R 4 ?
? R 3 ?
If V SEC drops below this level, the FCB voltage forces
continuous operation until V SEC is again above its
minimum.
Minimum On-Time Considerations
Minimum on-time t ON(MIN) is the smallest amount of time
that the LTC1625 is capable of turning the top MOSFET on
and off again. It is determined by internal timing delays and
the amount of gate charge required to turn on the top
MOSFET. Low duty cycle applications may approach this
3.3V
OR 5V
RUN/SS
RUN/SS
minimum on-time limit and care should be taken to ensure
that:
D1
C SS
C SS
1625 F07
t ON ( MIN ) <
V OUT
( V IN )( f )
Figure 7. RUN/SS Pin Interfacing
FCB Pin Operation
When the FCB pin drops below its 1.19V threshold,
continuous synchronous operation is forced. In this case,
the top and bottom MOSFETs continue to be driven
regardless of the load on the main output. Burst Mode
operation is disabled and current reversal is allowed in the
inductor.
In addition to providing a logic input to force continuous
operation, the FCB pin provides a means to regulate a
flyback winding output. It can force continuous synchro-
nous operation when needed by the flyback winding,
regardless of the primary output load.
The secondary output voltage V SEC is normally set as
shown in Figure 5a by the turns ratio N of the transformer:
V SEC ? (N + 1)V OUT
However, if the controller goes into Burst Mode operation
If the duty cycle falls below what can be accommodated by
the minimum on-time, the LTC1625 will begin to skip
cycles. The output voltage will continue to be regulated,
but the ripple current and ripple voltage will increase.
The minimum on-time for the LTC1625 is generally about
0.5 μ s. However, as the peak sense voltage (I L(PEAK) ?
R DS(ON) ) decreases, the minimum on-time gradually
increases up to about 0.7 μ s. This is of particular concern
in forced continuous applications with low ripple current
at light loads. If the duty cycle drops below the minimum
on-time limit in this situation, a significant amount of
cycle skipping can occur with correspondingly larger
current and voltage ripple.
Efficiency Considerations
The efficiency of a switching regulator is equal to the
output power divided by the input power ( × 100%). Per-
cent efficiency can be expressed as:
%Efficiency = 100% – (L1 + L2 + L3 + ...)
and halts switching due to a light primary load current,
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1625IS#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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 |
| LTC1625IS#PBF | 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR 16-SOIC |
| LTC1625IS#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1625IS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1625ISPBF | 制造商:Linear Technology 功能描述:No RSENSE Current Mode Regulator SOIC16 |
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