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參數(shù)資料
| 型號： | LTC1775IGN |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 2 A SWITCHING CONTROLLER, 165 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SSOP-16 |
| 文件頁數(shù)： | 16/24頁 |
| 文件大?。?/td> | 289K |
| 代理商： | LTC1775IGN |
16
LTC1775
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)
:
V
V
R
R
SEC MIN
(
)
.
+
1 19
1
4
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:
t
V
V
f
ON MIN
(
OUT
IN
)( )
)
(
<
If the duty cycle falls below what can be accommodated by
the minimum on-time, the LTC1775 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 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
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:
t
V
A
C
s
F C
μ
DELAY
SS
SS
=
μ
=
(
1 4
3
0 5
.
.
/
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-
tional Diagram).
Figure 9. RUN/SS Pin Interfacing
3.3V
OR 5V
RUN/SS
D1
C
SS
1775 F09
RUN/SS
C
SS
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.
APPLICATIOU
W
U
U
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| LTC1775CGN | Quadruple 2-Input Positive-NAND Gate 14-TVSOP -40 to 85 |
| LTC1775CS | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
| LTC1775I | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
| LTC1775IS | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
| LTC1775 | High Power Current Mode Synchronous Step-Down Switching Regulator(大功率，同步電流模式步降開關(guān)穩(wěn)壓器) |
相關(guān)代理商/技術(shù)參數(shù) |
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| LTC1775IGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1775IGN#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1775IGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1775IS | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1775IS#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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