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| 型号： | LT1339CSW#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 20-SOIC |
| 标准包装： | 1,000 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 150kHz |
| 占空比： | 90% |
| 电源电压： | 最高 60V |
| 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： | 0°C ~ 70°C |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 包装： | 带卷 (TR) |
LT1339
APPLICATIO N S I N FOR M ATIO N
300k
impedance of the I AVG pin. The integrator corner fre-
quency is typically set 1 to 2 orders of magnitude below the
oscillator frequency and follows the relation:
f –3dB = (3.2)(10 – 6 )/C AVG
The average current limit function can be disabled by
shorting the I AVG pin directly to SGND.
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
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
when the soft start pin is pulled to ground. Given the
typical soft start current of 8 μ A and a soft start timing
capacitor C SS , the start-up delay time to full available
average current will be:
sourcing 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 that
supply is almost fully enabled prevents the LT1339 regu-
lator from drawing large currents until the input supply is
able to provide the required power.
If additional hysteresis is desired for the enable function,
an external feedback resistor can be used from the LT1339
regulator output. If connection to the regulator output is
not desired, the 5V REF internal supply pin can be used.
Figure 3 shows a resistor connection on a 48V to 5V
converter that yields a 40V V IN start-up threshold for
regulator enable and also provides about 10% input
referred hysteresis.
V IN
48V
V OUT
5V
OPTION 1
t SS = (1.5)(10 5 )(C SS )
390k
OPTION 2
2
5V REF
Boost Supply
The V BOOST supply is bootstrapped via an external capaci-
tor. This supply provides gate drive to the topside switch
10k
13
LT1339
RUN/SHDN
1339 ? F03
FET. The bootstrap capacitor is charged from 12V IN through
a diode when the switch node is pulled low.
The diode reverse breakdown voltage must be greater than
V IN + 12V IN . The bootstrap capacitor should be at least 100
times greater than the total input capacitance of the
topside FET. A capacitor in the range of 0.1 μ F to 1 μ F is
generally adequate for most applications.
Shutdown Function — Input Undervoltage Detect and
Threshold Hysteresis
The LT1339 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.
Because an LT1339 controlled converter is a power
transfer device, a voltage that is lower than expected on
the input supply could require currents that exceed the
Figure 3. Input Supply Sequencing Programming
The shutdown function can be disabled by connecting the
RUN/SHDN pin to the 12V IN rail. This pin is internally
clamped to 2.5V through a 20k series input resistance and
will therefore draw about 0.5mA when tied directly to 12V.
This additional current can be minimized by making the
connection through an external resistor (100k is typically
used).
Operation with Split Supplies and Supply Sequencing
N-channel power MOSFETs can parasitically turn them-
selves on due to leakage currents or capacitive coupling
onto the MOSFET gate. In shutdown, this is prevented by
active pull-down clamps on the TG and BG driver outputs
of the LT1339. These clamps are active when 12V IN > 0.7V.
The 12V IN power supply for the LT1339 is usually derived
from the converter input supply; however, these supplies
can be independent. If these supplies are independent and
sn1339 1339fas
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1339I | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Power Synchronous DC/DC Controller |
| LT1339IN | 功能描述:IC REG CTRLR BST PWM CM 20-DIP 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 |
| LT1339IN#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-DIP 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 |
| LT1339ISW | 功能描述:IC REG CTRLR BST PWM CM 20-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 |
| LT1339ISW#PBF | 功能描述:IC REG CTRLR BST PWM CM 20-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 |
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