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参数资料
| 型号： | LT3844EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST INV PWM 16TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 95% |
| 电源电压： | 4 V ~ 60 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 无 |
| 反相： | 是 |
| 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： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
LT3844
APPLICATIONS INFORMATION
Note that when V IN is high and f SW is high, the transition
losses may dominate. A MOSFET with higher R DS(ON)
and lower C RSS may provide higher ef?ciency. MOSFETs
In continuous mode operation, the average diode cur-
rent is calculated at maximum output load current and
maximum V IN :
with higher voltage V DSS speci?cation usually have higher
R DS(ON) and lower C RSS .
Choose the MOSFET V DSS speci?cation to exceed the
I DIODE ( AVG ) = I OUT ( MAX )
V IN(MAX ) ? V OUT
V IN ( MAX )
maximum voltage across the drain to the source of the
MOSFET, which is V IN(MAX) plus any additional ringing
on the switch node. Ringing on the switch node can be
greatly reduced with good PCB layout and, if necessary,
an RC snubber.
The internal V CC regulator is capable of sourcing up to
40mA which limits the maximum total MOSFET gate
charge, Q G , to 40mA/f SW . The Q G vs V GS speci?cation is
typically provided in the MOSFET data sheet. Use Q G at
V GS of 8V. If V CC is back driven from an external supply,
the MOSFET drive current is not sourced from the internal
regulator of the LT3844 and the Q G of the MOSFET is not
limited by the IC. However, note that the MOSFET drive
current is supplied by the internal regulator when the
external supply back driving V CC is not available such as
during start-up or short-circuit.
To improve ef?ciency and to provide adequate margin
for short-circuit operation, a diode rated at 1.5 to 2
times the maximum average diode current, I DIODE(AVG) ,
is recommended.
Step-Down Converter: Input Capacitor Selection
A local input bypass capacitor is required for buck convert-
ers because the input current is pulsed with fast rise and
fall times. The input capacitor selection criteria are based
on the bulk capacitance and RMS current capability. The
bulk capacitance will determine the supply input ripple
voltage. The RMS current capability is used to keep from
overheating the capacitor.
The bulk capacitance is calculated based on maximum
input ripple, Δ V IN :
The manufacturer’s maximum continuous drain current
speci?cation should exceed the peak switch current,
I OUT(MAX) + Δ I L /2.
C IN ( BULK ) =
I OUT ( MAX ) ? V OUT
Δ V IN ? f SW ? V IN ( MIN )
V OUT IN OUT )
I CIN ( RMS ) = I OUT
Duringthesupplystart-up,thegatedrivelevelsaresetby
the V CC voltage regulator, which is approximately 8V. Once
the supply is up and running, the V CC can be back driven
by an auxiliary supply such as V OUT . It is important not
to exceed the manufacturer’s maximum V GS speci?cation.
A standard level threshold MOSFET typically has a V GS
maximum of 20V.
Step-Down Converter: Recti?er Selection
The recti?er diode (D1 on the Functional Diagram) in a
buck converter generates a current path for the inductor
current when the main power switch is turned off. The
recti?er is selected based upon the forward voltage, re-
verse voltage and maximum current. A Schottky diode is
recommended. Its low forward voltage yields the lowest
power loss and highest ef?ciency. The maximum reverse
voltage that the diode will see is V IN(MAX) .
Δ V IN is typically chosen at a level acceptable to the user.
100mV to 200mV is a good starting point. Aluminum elec-
trolytic capacitors are a good choice for high voltage, bulk
capacitance due to their high capacitance per unit area.
The capacitor’s RMS current is:
( V – V
( V IN ) 2
If applicable, calculate it at the worst-case condition,
V IN = 2V OUT . The RMS current rating of the capacitor
is speci?ed by the manufacturer and should exceed the
calculated I CIN(RMS) . Due to their low ESR (equivalent
series resistance), ceramic capacitors are a good choice
for high voltage, high RMS current handling. Note that the
ripple current ratings from aluminum electrolytic capacitor
manufacturers are based on 2000 hours of life. This makes
3844fb
13
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相关代理商/技术参数 |
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| LT3844IFE | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 4V to 60V Input 16-Pin TSSOP EP |
| LT3844IFE#PBF | 功能描述:IC REG CTRLR BST INV PWM 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) |
| LT3844IFE#TRPBF | 功能描述:IC REG CTRLR BST INV PWM 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: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 |
| LT3844IFEPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Step-Down 4-60V TSSOP16 |
| LT3844IFE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency |
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