参数资料
| 型号： | LTC3813EG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 27/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 28-SSOP |
| 标准包装： | 47 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 7 V ~ 75 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 ~ 85°C |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
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LTC3813
APPLICATIONS INFORMATION
If the external frequency (f SYNC ) is greater than the oscil-
lator frequency f O , current is sourced continuously, pull-
ing up the PLL/LPF pin. When the external frequency is
less than f O , current is sunk continuously, pulling down
the PLL/LPF pin. If the external and internal frequencies
are the same but exhibit a phase difference, the current
sources turn on for an amount of time corresponding to
the phase difference. Thus the voltage on the PLL/LPF
pin is adjusted until the phase and frequency of the external
and internal oscillators are identical. At this stable operating
point the phase comparator output is open and the ?lter
capacitor C LP holds the voltage. The LTC3813 SYNC pin
must be driven from a low impedance source such as a
logic gate located close to the pin.
The loop ?lter components (C LP , R LP ) smooth out the
current pulses from the phase detector and provide a
stable input to the voltage controlled oscillator. The ?lter
components C LP and R LP determine how fast the loop
acquires lock. Typically R LP = 10kΩ and C LP is 0.01μF
to 0.1μF.
Pin Clearance/Creepage Considerations
The LTC3813 is available in the G28 package which
has 0.0106" spacing between adjacent pins. To
maximize PC board trace clearance between high volt-
age pins, the LTC3813 has three unconnected pins
between all adjacent high voltage and low voltage
pins, providing 4(0.0106") = 0.042" clearance which
will be suf?cient for most applications up to 100V.
For more information, refer to the printed circuit board
design standards described in IPC-2221 (www.ipc.org).
Ef?ciency Considerations
The percent ef?ciency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the ef?ciency and which change would
produce the most improvement. Although all dissipative
elements in the circuit produce losses, four main sources
account for most of the losses in LTC3813 circuits:
1. DC I 2 R losses. These arise from the resistances of the
MOSFETs, inductor and PC board traces and cause
current is maximum at maximum output current and
minimum input voltage. The average input current ?ows
through L, but is chopped between the top and bottom
MOSFETs. If the two MOSFETs have approximately the
same R DS(ON) , then the resistance of one MOSFET can
simply be summed with the resistances of L and the
board traces to obtain the DC I 2 R loss. For example, if
R DS(ON) = 0.01Ω and R L = 0.005Ω, the loss will range
from 15mW to 1.5W as the input current varies from
1A to 10A.
2. Transition loss. This loss arises from the brief amount
of time the bottom MOSFET spends in the saturated
region during switch node transitions. It depends upon
the output voltage, load current, driver strength and
MOSFET capacitance, among other factors. The loss
is signi?cant at output voltages above 20V and can be
estimated from the second term of the P MAIN equa-
tion found in the Power MOSFET Selection section.
When transition losses are signi?cant, ef?ciency can
be improved by lowering the frequency and/or using a
bottom MOSFET(s) with lower C RSS at the expense of
higher R DS(ON) .
3. INTV CC /DRV CC current. This is the sum of the MOSFET
driver and control currents. Control current is typically
about 3mA and driver current can be calculated by:
I GATE = f(Q G(TOP) + Q G(BOT) ), where Q G(TOP) and Q G(BOT)
are the gate charges of the top and bottom MOSFETs.
This loss is proportional to the supply voltage that
INTV CC /DRV CC is derived from, i.e., V IN , V OUT or an
external supply connected to INTV CC /DRV CC .
4. C OUT loss. The output capacitor has the dif?cult job
of ?ltering the large RMS input current out of the syn-
chronous MOSFET. It must have a very low ESR to
minimize the AC I 2 R loss.
Other losses, including C IN ESR loss, Schottky diode D1
conduction loss during dead time and inductor core loss
generally account for less than 2% additional loss. When
making adjustments to improve ef?ciency, the input cur-
rent is the best indicator of changes in ef?ciency. If you
make a change and the input current decreases, then the
ef?ciency has increased. If there is no change in input
current, then there is no change in ef?ciency.
the ef?ciency to drop at high input currents. The input
3813fb
27
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| LTC3813IG#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:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3813IG#TRPBF | 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:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3814EFE-5#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-TSSOP 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 |
| LTC3814EFE-5#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-TSSOP 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) |
| LTC3814IFE-5#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-TSSOP 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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