- 您现在的位置：买卖IC网 > PDF目录15253 > LTC1775IS#TRPBF (Linear Technology)IC REG CTRLR BUCK PWM CM 16-SOIC PDF资料下载
参数资料
| 型号： | LTC1775IS#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SOIC |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 165kHz |
| 占空比： | 99% |
| 电源电压： | 4.3 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： | 带卷 (TR) |
LTC1775
APPLICATIO S I FOR ATIO
? C SS = ( ) C SS
t DELAY = ?
0 . 5 s / μ F
V SEC ( MIN ) ? 1 . 19 V ? 1 +
?
Run/Soft Start Function
The RUN/SS pin is a dual purpose pin that provides a soft
start function and a means to shut down the LTC1775. Soft
start reduces surge currents from V IN by gradually in-
creasing the controller’s current limit I TH(MAX) . This pin
can also be used for power supply sequencing.
Pulling the RUN/SS pin below 1.4V puts the LTC1775 into
a low quiescent current shutdown (I Q < 30 μ A). This pin can
be driven directly from logic as shown in Figure 9. Releas-
ing the RUN/SS pin allows an internal 3 μ A current source
to charge up the soft-start capacitor C SS . If RUN/SS has
been pulled all the way to ground there is a delay before
starting of approximately:
? 1 . 4 V ?
? 3 μ A ?
When the voltage on RUN/SS reaches 1.4V the LTC1775
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 80mV/R DS(ON)
until the output reaches half of its final value.
Diode D1 in Figure 9 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-
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 main 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
and halts switching due to a light main load current, 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 LTC1775 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
minimum on-time limit and care should be taken to ensure
that:
tional Diagram).
3.3V
OR 5V
D1
RUN/SS
RUN/SS
t ON ( MIN ) <
V OUT
( V IN )( f )
C SS
C SS
If the duty cycle falls below what can be accommodated by
the minimum on-time, the LTC1775 will begin to skip
1775 F09
Figure 9. 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 under light
loads is allowed in the inductor.
16
cycles. The output voltage will continue to be regulated,
but the ripple current and ripple voltage will increase.
The minimum on-time for the LTC1775 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
相关PDF资料 |
PDF描述 |
|---|---|
| RMM15DRMH-S288 | CONN EDGECARD 30POS .156 EXTEND |
| VE-B7Y-EW-F2 | CONVERTER MOD DC/DC 3.3V 66W |
| LTC1775IS#TR | IC REG CTRLR BUCK PWM CM 16-SOIC |
| EBC35DRES-S734 | CONN EDGECARD 70POS .100 EYELET |
| LTC1435IS#PBF | IC REG CTRLR BUCK PWM CM 16-SOIC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1778EGN | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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: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) |
| LTC1778EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC1778EGN#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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: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) |
| LTC1778EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC1778EGN-1 | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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: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) |
发布紧急采购，3分钟左右您将得到回复。