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| 型号： | LTC3851EGN#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 产品培训模块： | LTC3851 Single Output DC/DC Switching Regulator Controller |
| 特色产品： | Wide Input Voltage Range Synchronous Step-Down DC/DC Controller |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 790kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 38 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 ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3851
APPLICATIONS INFORMATION
V MASTER
TO
TK/SS
PIN
R3
R4
TO
V FB
PIN
R3
R4
V OUT
V MASTER
TO
TK/SS
PIN
R1
R2
TO
V FB
PIN
R3
R4
V OUT
3851 F04
(4a) Coincident Tracking Setup
(4b) Ratiometric Tracking Setup
Figure 4. Setup for Coincident and Ratiometric Tracking
what type of bulk capacitor is used, an additional 0.1μF
I
I
ceramic capacitor placed directly adjacent to the INTV CC
TK/SS
D1
D2
+
–
EA
and GND pins is highly recommended. Good bypassing
is needed to supply the high transient currents required
by the MOSFET gate drivers.
0.8V
V FB
D3
3851 F05
High input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the maxi-
Figure 5. Equivalent Input Circuit of Error Ampli?er
mode, the TK/SS voltage is substantially higher than
0.8V at steady-state and effectively turns off D1. D2 and
D3 will therefore conduct the same current and offer
tight matching between V FB and the internal precision
0.8V reference. In the ratiometric mode, however, TK/SS
equals 0.8V at steady-state. D1 will divert part of the bias
current to make V FB slightly lower than 0.8V.
Although this error is minimized by the exponential I-V
characteristic of the diode, it does impose a ?nite amount
of output voltage deviation. Furthermore, when the master
supply’s output experiences dynamic excursion (under
load transient, for example), the slave channel output will
be affected as well. For better output regulation, use the
coincident tracking mode instead of ratiometric.
INTV CC Regulator
The LTC3851 features a PMOS low dropout linear regulator
(LDO) that supplies power to INTV CC from the V IN supply.
INTV CC powers the gate drivers and much of the LTC3851 ’s
internal circuitry. The LDO regulates the voltage at the
INTV CC pin to 5V.
The LDO can supply a peak current of 50mA and must
be bypassed to ground with a minimum of 2.2μF ceramic
capacitor or low ESR electrolytic capacitor. No matter
mum junction temperature rating for the LTC3851 to be
exceeded. The INTV CC current, which is dominated by the
gate charge current, is supplied by the 5V LDO.
Power dissipation for the IC in this case is highest and
is approximately equal to V IN ? I INTVCC . The gate charge
current is dependent on operating frequency as discussed
in the Ef?ciency Considerations section. The junction
temperature can be estimated by using the equations given
in Note 3 of the Electrical Characteristics. For example,
the LTC3851 INTV CC current is limited to less than 14mA
from a 36V supply in the GN package:
T J = 70°C + (14mA)(36V)(110°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 (MODE/PLLIN
= INTV CC ) at maximum V IN .
Topside MOSFET Driver Supply (C B , D B )
An external bootstrap capacitor C B connected to the
BOOST pin supplies the gate drive voltage for the topside
MOSFET. Capacitor C B in the Functional 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
MOSFET. This enhances the MOSFET and turns on the
topside switch. The switch node voltage, SW, rises to V IN
3851fb
16
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相关代理商/技术参数 |
参数描述 |
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| LTC3851EMSE#PBF | 功能描述:IC REG CTRLR BUCK 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:- 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 |
| LTC3851EMSE#PBF | 制造商:Linear Technology 功能描述:Switch Regulator IC 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR CTRL MSOP-16 |
| LTC3851EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC3851EMSE-1#PBF | 功能描述:IC REG CTRLR BUCK 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:- 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 |
| LTC3851EMSE-1#TRPBF | 功能描述:IC REG CTRLR BUCK 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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