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| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 28/48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 total power dissipation is the sum of these two and
the junction temperature can then be estimated using the
following equation:
T J = T A + (P VCC + P LDO ) ? R θ JA
As an example, consider a 2-phase, single-output applica-
tion with a 12V input voltage and a 1.2V output at up to
30A (15A/phase), using the QFN version of the LTC3811.
The upper power MOSFETs are the Renesas RJK0305DPB
(one per phase) and the lower power MOSFETs are the
RJK0301DPB (one per phase). The upper MOSFETs have
a typical R DS(ON) = 10mΩ at V GS = 4.5V and a typical Q G =
8nC. The lower MOSFETs have a typical R DS(ON) = 3mΩ at
V GS = 4.5V and a typical Q G = 32nC. The total gate charge
is therefore 80nC and the operating frequency is 500kHz.
With a maximum ambient temperature of 70°C and a
thermal resistance of 34°C/W for the QFN package,
I DRVCC = 10mA + 500kHz ? 80nC = 50mA
P DRVCC = 6V ? (10mA + 500kHz ? 80nC) = 300mW
P LDO = (12V – 6V) ? (10mA + 500kHz ? 80nC)
= 300mW
T J = 70°C + (0.3 + 0.3) ? 34°C/W = 90°C
A 20°C rise in the junction temperature and a maximum LDO
current of 50mA are acceptable numbers but could be im-
proved upon by using the EXTV CC pin to supply power to the
gate drivers. The use of an auxiliary supply connected to the
EXTV CC pin would reduce the junction temperature rise by
a factor of 2, resulting in a max junction temperature of:
T J = 70°C + 0.3 ? 34°C/W = 80°C
For applications where the internal LDO is being used to
supply power to the IC, to prevent the maximum junction
temperature from being exceeded the input supply cur-
rent should be monitored at maximum V IN in continuous
conduction mode (i.e., with MODE/SYNC connected to
INTV CC ).
Using the EXTV CC Pin to Supply Power to the LTC3811
The LTC3811 contains an internal P-channel MOSFET
switch connected between the EXTV CC and DRV CC pins.
When the voltage applied to EXTV CC exceeds 4.5V, the
internal LDO is turned off and the PMOS switch turns on,
connecting the EXTV CC pin to the DRV CC pin and thereby
supplying the internal analog and digital circuitry and
MOSFET gate drive power. Do not apply greater than 7V
to the EXTV CC pin (its absolute maximum rating) and en-
sure that EXTV CC < V IN + 0.3V when using the application
circuits shown. If an external voltage source is applied to
the EXTV CC pin when the V IN supply is not present, a diode
can be placed in series with the LTC3811’s V IN pin and a
Schottky diode between the EXTV CC pin and the V IN pin,
to prevent current from backfeeding into V IN through the
PMOS body diodes.
Signi?cant energy gains can be realized by power-
ing DRV CC and INTV CC from an auxiliary supply, since
the V IN current resulting from the driver and analog
control circuitry currents will be scaled by the ratio:
Duty Cycle/Ef?ciency
The following list summarizes the three possible connec-
tions for EXTV CC :
1. EXTV CC left open (or grounded). This will cause DRV CC
and INTV CC to be powered from the internal 6V LDO,
resulting in a signi?cant ef?ciency penalty and excess
power dissipation at high input voltages.
2. EXTV CC connected to an external supply. If an external
supply is available in the 5V to 7V range it may be used
to power EXTV CC , provided it is capable of satisfying
the gate drive and control IC current requirements. V IN
must be greater than or equal to the voltage applied to
the EXTV CC pin.
3. EXTV CC connected to an output-derived boost network.
For 3.3V and other low voltage regulators, ef?ciency
gains can still be realized by connecting EXTV CC to
an output-derived voltage which has been boosted to
greater than 4.5V but less than 7V. This can be done
with a capacitive charge pump shown in Figure 16.
Power MOSFET and Schottky Diode (Optional)
Selection
Two external power MOSFETs must be selected for each
controller in the LTC3811: one N-channel MOSFET for the
top (main) switch, and one N-channel MOSFET for the
bottom (synchronous) switch.
3811f
28
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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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