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| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 27/48页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 30 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3811
APPLICATIONS INFORMATION
The value of the resistors in the RC ?lter is a tradeoff
between power dissipation and DC accuracy. The power
loss on R1 is:
In general, there are three potential sources of power
dissipation in the LTC3811:
1. The quiescent current consumed by all of the analog
P R 1 =
( V IN – V O ) ? V O
R 1
control circuitry connected to INTV CC
2. Gate drive losses
for a buck converter.
If the value of the ?lter resistor is too low, its power dis-
sipation will rise, resulting in a larger package size and
decreased ef?ciency at light load. If the value of the ?lter
resistor is too high, the input bias current ?owing out of
the SENSE + pin (approximately 1.5μA) could cause the
voltage drop across the resistor to be the same order
of magnitude of the peak sense voltage, which is also
undesirable. A good balance is to use a resistor value of
about 1k. An additional 1k resistor (R2) in the SENSE – path
is used to compensate for the drop in the SENSE + path,
and ideally these two resistors (R1 and R2) should match
one another.
In general, the larger the sense voltage range is, the smaller
the percentage error due to a mismatch in the ?lter resis-
tor IR drops. The current comparators were designed for
low offset and high speed, speci?cally for applications
requiring a small peak sense voltage.
Gate Drive Power Supply Considerations
The LTC3811 user has a choice of how to supply power to
the gate drivers and low voltage analog control circuitry.
The ?rst of these is to use the internal low dropout linear
regulator, LDO, to draw power from V IN and regulate DRV CC
to 6V. The second way of supplying power to the gate
drivers and analog control circuitry is through the EXTV CC
pin. The choice of which supply path to use depends upon
system ?exibility, power dissipation and the maximum
junction temperature in the application.
The internal DRV CC LDO is capable of sourcing up to
100mA, allowing the user to connect multiple power
MOSFETs in parallel on both channels for the high power
3. Losses in the LDO when power is being supplied from
V IN
The steady-state quiescent current of the IC is typically
10mA and ?ows into the INTV CC pin, either through the
LDO from V IN or through an auxiliary power supply con-
nected to the EXTV CC pin.
The second source of power dissipation is the gate drivers
connected to DRV CC . The lower MOSFET gate drivers are
directly connected to DRV CC and the upper ones are con-
nected to DRV CC through the bootstrap diode and ?oating
supply capacitor C B (refer to Functional Diagram). The gate
driver current requirement depends upon the number of
MOSFETs being driven, their total gate charge, Q G(TOT) ,
and the operating frequency, f, of the converter. The total
current required by the low voltage circuitry is the sum of
the DC quiescent current and the gate drive current.
I VCC = 10mA + Q G(TOT) ? f
If the internal LDO in the LTC3811 is used to supply power
to DRV CC and INTV CC , care should be taken to ensure that
the total low voltage current doesn’t exceed the 100mA
limit for the LDO.
Assuming that DRV CC = EXTV CC = INTV CC = 6V, power
dissipation due to the quiescent current and gate drive
losses is:
PV CC = 6V ? (10mA + Q G(TOT) ? f)
The third source of power dissipation occurs in the LDO,
which supplies power to the DRV CC pin when EXTV CC is
less than 4.7V. When power is being drawn from V IN the
power dissipated in the LDO is:
P LDO = (V IN – V DRVCC ) ? (10mA + Q G(TOT) ? f)
density applications. High input voltage applications in
which multiple large MOSFETs are being driven at high
frequencies, however, may cause the maximum junction
temperature rating for the LTC3811 to be exceeded.
3811f
27
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| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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 |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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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