参数资料
| 型号： | LT1680ISW#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 16-SOIC |
| 标准包装： | 47 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 200kHz |
| 占空比： | 90% |
| 电源电压： | 4 V ~ 60 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 ~ 85°C |
| 封装/外壳： | 16-SOIC（0.295"，7.50mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1328 (CN2011-ZH PDF) |
LT1680
APPLICATIO S I FOR ATIO
200
180
160
140
120
100
80
60
40
3
C CT = 0.68nF
C CT = 1nF
C CT = 1.5nF
C CT = 2.2nF
7 11 15 19 23 27 31 35 39 43 47
TIMING RESISTOR (k ? )
1680 F02
capacitor C SS , the start up delay time to full available
average current will be:
t SS = (1.5)(10 5 )(C SS )
Shutdown Function —Input Undervoltage Detect
and Threshold Hysteresis
The LT1680 RUN/SHDN pin uses a bandgap generated
reference threshold of about 1.25V. This precision thresh-
old allows use of the RUN/SHDN pin for both logic-level
shutdown applications and analog monitoring applica-
tions such as power supply sequencing.
Figure 2. Operating Frequency vs R CT , C CT
Average Current Limit
The average current limit function is implemented using
an external capacitor (C AVG ) connected either from the
I AVG pin to the V C pin or from the I AVG pin to SGND. This
capacitor forms a single-pole integrator with the 50k ?
output impedance of the I AVG pin. Precise integration
frequencies can be determined using a ground reference
integration capacitor using the relation:
f – 3dB = (3.2)(10 – 6 )/C AVG
Connecting a capacitor from the I AVG pin to the V C pin uses
an internal gain block to form an active integrator circuit,
minimizing the required capacitance for stable operation.
A typical value for this integration capacitor is 220pF from
I AVG to V C .
Shorting the I AVG pin to SGND will disable the average
current limit function.
Soft Start Programming
The current control pin (V C ) limits sensed inductor current
to zero at voltages less than a transistor V BE , to full average
Because an LT1680 controlled converter is a power trans-
fer device, a voltage that is lower than expected on the
input supply could require currents that exceed the sourc-
ing capabilities of that supply, causing the system to lock-
up in an undervoltage state. Input supply start-up protection
can be achieved by enabling the RUN/SHDN pin using a
resistor divider from the input supply to ground. Setting
the divider output to 1.25V when the supply is almost fully
enabled prevents the LT1680 regulator from drawing large
currents until the input supply is able to supply the
required power.
If additional hysteresis is desired for the enable function,
an external feedback resistor can be used from the LT1680
regulator output. If connection to the regulator output is
not desired, the 5V REF internal supply pin can be used.
Figure 3 shows an input supply sequencing configuration
on a 24V input converter. This configuration yields an
enable condition of 90% V IN (~ 21.5V) with about 10%
threshold hysteresis.
The shutdown function can be disabled by connecting the
RUN/SHDN pin to the 12V IN rail. This pin is internally
V IN
24V
current limit at V C = V BE + 1.8V. This generates a 1.8V full
regulation range for average load current. An internal
voltage clamp forces the V C pin to a V BE – 100mV above
the SS pin voltage. This 100mV “dead zone” assures 0%
duty cycle operation at the start of the soft start cycle or
160k
390k
10k
16
11
5V REF
LT1680
RUN/SHDN
1680 F03
when the soft start pin is pulled to ground. Given the
typical soft start current of 8 μ A and a soft start timing
10
Figure 3. Input Supply Sequencing Programming
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| LT1681ESW | 功能描述:IC SYNCHRONOUS FWRD CTRLR 20SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 电源控制器，监视器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 应用:多相控制器 输入电压:- 电源电压:9 V ~ 14 V 电流 - 电源:- 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（5x5） 包装:带卷 (TR) |
| LT1681ESW#PBF | 功能描述:IC SYNCHRONOUS FWRD CTRLR 20SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电源控制器，监视器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 应用:多相控制器 输入电压:- 电源电压:9 V ~ 14 V 电流 - 电源:- 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（5x5） 包装:带卷 (TR) |
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| LT1681ESW#TRPBF | 功能描述:IC SYNCHRONOUS FWRD CTRLR 20SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电源控制器，监视器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 应用:多相控制器 输入电压:- 电源电压:9 V ~ 14 V 电流 - 电源:- 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:40-WFQFN 裸露焊盘 供应商设备封装:40-TQFN-EP（5x5） 包装:带卷 (TR) |
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