参数资料
| 型号： | LTC3786EUD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 18/34页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 16-QFN |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 850kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 38 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： | 16-WFQFN 裸露焊盘 |
| 包装： | 管件 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页当前第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页
LTC3786
APPLICATIONS INFORMATION
t SS = C SS ?
Soft-Start(SSPin)
The start-up of the V OUT is controlled by the voltage on
the SS pin. When the voltage on the SS pin is less than
the internal 1.2V reference, the LTC3786 regulates the VFB
pin voltage to the voltage on the SS pin instead of 1.2V.
Soft-start is enabled by simply connecting a capacitor from
the SS pin to ground, as shown in Figure 4. An internal
10μA current source charges the capacitor, providing a
linear ramping voltage at the SS pin. The LTC3786 will
regulate the V FB pin (and hence, V OUT ) according to the
voltage on the SS pin, allowing V OUT to rise smoothly
from V IN to its final regulated value. The total soft-start
time will be approximately:
1.2V
10μA
LTC3786
SS
C SS
SGND
3786 F04
Figure 4. Using the SS Pin to Program Soft-Start
INTV CC Regulator
The LTC3786 features an internal P-channel low dropout
linear regulator (LDO) that supplies power at the INTV CC
pin from the VBIAS supply pin. INTV CC powers the gate
drivers and much of the LTC3786’s internal circuitry. The
VBIAS LDO regulates INTV CC to 5.4V. It can supply at least
50mA and must be bypassed to ground with a minimum
of 4.7μF ceramic capacitor. Good bypassing is needed to
supply the high transient currents required by the MOSFET
gate drivers.
High input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the
maximum junction temperature rating for the LTC3786
to be exceeded. The power dissipation for the IC is equal
to VBIAS ? I INTVCC . The gate charge current is dependent
on operating frequency, as discussed in the Efficiency
Considerations section. The junction temperature can be
estimated by using the equations given in Note 2 of the
Electrical Characteristics. For example, at 70°C ambient
temperature, the LTC3786 INTV CC current is limited to
less than 20mA in the QFN package from a 40V supply:
T J = 70°C + (20mA)(40V)(68°C/W) = 125°C
In an MSOP package, the INTV CC current is limited to less
than 34mA from a 40V supply:
T J = 70°C + (34mA)(40V)(40°C/W) = 125°C
To prevent the maximum junction temperature from being
exceeded, the input supply current must be checked while
operating in continuous conduction mode (PLLIN/MODE
= INTV CC ) at maximum VBIAS.
Topside MOSFET Driver Supply (C B , D B )
External bootstrap capacitors, C B , connected to the
BOOST pin supplies the gate drive voltage for the topside
MOSFET. Capacitor C B in the Block Diagram is charged
though external diode, D B , from INTV CC when the SW pin
is low. When the topside MOSFET is to be turned on, the
driver places the C B voltage across the gate-source of the
desired MOSFET. This enhances the MOSFET and turns on
the topside switch. The switch node voltage, SW, rises to
V OUT and the BOOST pin follows. With the topside MOSFET
on, the boost voltage is above the output voltage: V BOOST
= V OUT + V INTVCC . The value of the boost capacitor, C B ,
needs to be 100 times that of the total input capacitance
of the topside MOSFET(s). The reverse breakdown of the
external Schottky diode must be greater than V IN(MAX) .
The external diode D B can be a Schottky diode or silicon
diode, but in either case it should have low leakage and fast
recovery. Pay close attention to the reverse leakage at high
temperatures where it generally increases substantially.
The topside MOSFET driver includes an internal charge
pump that delivers current to the bootstrap capacitor from
the BOOST pin. This charge current maintains the bias
voltage required to keep the top MOSFET on continuously
during dropout/overvoltage conditions. The Schottky/
silicon diode selected for the topside driver should have a
reverse leakage less than the available output current the
charge pump can supply. Curves displaying the available
charge pump current under different operating conditions
can be found in the Typical Performance Characteristics
section.
3786fa
18
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3787EUFD#PBF | IC REG CTRLR BST PWM CM 28-QFN |
| LTC3788IUH#TRPBF | IC REG CTRLR BST PWM CM 32-QFN |
| LTC3789EGN#PBF | IC REG CTRLR BST PWM CM 28-SSOP |
| LTC3801BES6#TRM | IC REG CTRLR BUCK PWM TSOT23-6 |
| LTC3802EGN | IC REG CTRLR BUCK PWM VM 28-SSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3786IMSE#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP 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) |
| LTC3786IMSE#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP 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) |
| LTC3786IUD#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-QFN 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) |
| LTC3786IUD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-QFN 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) |
| LTC3787EGN#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
发布紧急采购，3分钟左右您将得到回复。