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参数资料
| 型号： | LTC3786EMSE#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 9/34页 |
| 文件大小： | 397K |
| 代理商： | LTC3786EMSE#TRPBF |
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LTC3786
17
3786fa
applicaTions inForMaTion
accounts for the loss caused by reverse recovery current,
is inversely proportional to the gate drive current and has
an empirical value of 1.7.
BothMOSFETshaveI2RlosseswhilethebottomN-channel
equation includes an additional term for transition losses,
which are highest at low input voltages. For high VIN the
high current efficiency generally improves with larger
MOSFETs, while for low VIN the transition losses rapidly
increase to the point that the use of a higher RDS(ON)device
with lower CMILLERactuallyprovideshigherefficiency.The
synchronous MOSFET losses are greatest at high input
voltage when the bottom switch duty factor is low or dur-
ing overvoltage when the synchronous switch is on close
to 100% of the period.
The term (1 +
δ) is generally given for a MOSFET in the
form of a normalized RDS(ON) vs Temperature curve, but
δ = 0.005/°C can be used as an approximation for low
voltage MOSFETs.
CIN and COUT Selection
The input ripple current in a boost converter is relatively
low (compared with the output ripple current), because
this current is continuous. The input capacitor, CIN, volt-
age rating should comfortably exceed the maximum input
voltage. Although ceramic capacitors can be relatively
tolerant of overvoltage conditions, aluminum electrolytic
capacitorsarenot.Besuretocharacterizetheinputvoltage
for any possible overvoltage transients that could apply
excess stress to the input capacitors.
The value of the CIN is a function of the source impedance,
andingeneral,thehigherthesourceimpedance,thehigher
the required input capacitance. The required amount of
input capacitance is also greatly affected by the duty cycle.
High output current applications that also experience high
duty cycles can place great demands on the input supply,
both in terms of DC current and ripple current.
Inaboostconverter,theoutputhasadiscontinuouscurrent,
so COUT must be capable of reducing the output voltage
ripple. The effects of ESR (equivalent series resistance)
and the bulk capacitance must be considered when choos-
ing the right capacitor for a given output ripple voltage.
The steady ripple voltage due to charging and discharging
the bulk capacitance in a single phase boost converter is
given by:
VRIPPLE =
IOUT(MAX) VOUT – VIN(MIN)
(
)
COUT VOUT f
V
where COUT is the output filter capacitor.
The steady ripple due to the voltage drop across the ESR
is given by:
VESR = IL(MAX) ESR
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, aluminum electrolytic and
ceramic capacitors are all available in surface mount
packages. Ceramic capacitors have excellent low ESR
characteristics but can have a high voltage coefficient.
Capacitors are now available with low ESR and high ripple
current ratings (i.e., OS-CON and POSCAP).
Setting Output Voltage
The LTC3786 output voltage is set by an external feedback
resistordividercarefullyplacedacrosstheoutput,asshown
in Figure 3. The regulated output voltage is determined by:
VOUT = 1.2V 1+
RB
RA
Great care should be taken to route the VFB line away
from noise sources, such as the inductor or the SW line.
Also, keep the VFB node as small as possible to avoid
noise pickup.
LTC3786
VFB
VOUT
RB
RA
3786 F03
Figure 3. Setting Output Voltage
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3786EMSE#PBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| LTC3786EUD#PBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC16 |
| LTC3787IGN#TRPBF | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28 |
| LTC3787EGN#TRPBF | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PDSO28 |
| LTC3787EUFD#PBF | SWITCHING CONTROLLER, 585 kHz SWITCHING FREQ-MAX, PQCC28 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3786EUD#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:- 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 |
| LTC3786EUD#PBF | 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 550kHz, QFN16 |
| LTC3786EUD#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) |
| 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) |
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