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参数资料
| 型号： | LTC3714EG#TR |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC STP-DWN CNTRLR W/OPAMP 28SSOP |
| 标准包装： | 2,000 |
| 应用： | 控制器，Intel Pentium? |
| 输入电压： | 4 V ~ 36 V |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 1.75 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC3714EGTR |
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LTC3714
APPLICATIONS INFORMATION
t DELAY =
C SS = ( 1.3s/μF ) C SS
Soft-StartandLatchoffwiththeRUN/SSPin
The RUN/SS pin provides a means to shut down the
LTC3714 as well as a timer for soft-start and overcurrent
latchoff. Pulling the RUN/SS pin below 1.5V puts the
LTC3714 into a low quiescent current shutdown (I Q ≤
30μA). Releasing the pin allows an internal 1.2μA internal
current source to charge up the external timing capacitor
C SS . If RUN/SS has been pulled all the way to ground,
there is a delay before starting of about:
1.5V
1.2μA
When the voltage on RUN/SS reaches 1.5V, the LTC3714
begins operating with a clamp on ITH of approximately
0.9V. As the RUN/SS voltage rises to 3V, the clamp on ITH
is raised until its full 2.4V range is available. This takes an
additional 1.3s/μF, during which the load current is folded
back until the output reaches 50% of its final value. The
pin can be driven from logic as shown in Figure 7. Diode
D1 reduces the start delay while allowing C SS to charge
up slowly for the soft-start function.
After the controller has been started and given adequate
time to charge up the output capacitor, C SS is used as a
short-circuit timer. After the RUN/SS pin charges above 4V,
if the output voltage falls below 75% of its regulated value,
then a short-circuit fault is assumed. A 1.7μA current then
begins discharging C SS . If the fault condition persists until
the RUN/SS pin drops to 3.5V, then the controller turns
off both power MOSFETs, shutting down the converter
permanently. The RUN/SS pin must be actively pulled
down to ground in order to restart operation.
The overcurrent protection timer requires that the soft-start
timing capacitor C SS be made large enough to guarantee
that the output is in regulation by the time C SS has reached
the 4V threshold. In general, this will depend upon the
size of the output capacitance, output voltage and load
current characteristic. A minimum soft-start capacitor
can be estimated from:
C SS > C OUT V OUT R SENSE (10 –4 [F/Vs])
Generally 0.1μF is more than sufficient.
Overcurrent latchoff operation is not always needed or
desired. Load current is already limited during a short-
circuit by the current foldback circuitry and latchoff op-
eration can prove annoying during troubleshooting. The
feature can be overridden by adding a pull-up current of
>5μA to the RUN/SS pin. The additional current prevents
the discharge of C SS during a fault and also shortens
the soft-start period. Using a resistor to V IN as shown in
Figure 7a is simple, but slightly increases shutdown cur-
rent. Connecting a resistor to INTV CC as shown in Figure
7b eliminates the additional shutdown current, but requires
a diode to isolate C SS . Any pull-up network must be able
to pull RUN/SS above the 4.5V maximum threshold that
arms the latchoff circuit and overcome the 4μA maximum
discharge current.
INTV CC
3.3V OR 5V
D1
V IN
RUN/SS
R SS *
R SS *
D2*
RUN/SS
C SS
C SS
3714 F07
*OPTIONAL TO OVERRIDE
OVERCURRENT LATCHOFF
(7a)
(7b)
Figure 7. RUN/SS Pin Interfacing with Latchoff Defeated
3714f
19
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| LTC3716EG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 36-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: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 |
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