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参数资料
| 型号： | LT3844EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/24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
two losses. Calculate the maximum conduction losses of
the MOSFET:
V GS of 8V. If V CC is back driven from an external supply,
the MOSFET drive current is not sourced from the internal
= DC
? 1 ? DC MAX ? ?
? I OUT(MAX ) ?
P COND MAX ?
? R DS ( ON )
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
( k )( V OUT ) 2 ( I OUT ( MAX ) ) ( C RSS )( f SW )
( 1 ? DC M AX )
Note that R DS(ON) has large positive temperature depen-
dence. The MOSFET manufacturer’s data sheet contains
a curve, R DS(ON) vs Temperature. Calculate the maximum
transition losses:
P TRAN =
where k is a constant inversely related to the gate driver
current, approximated by k = 2 for LT3844 applications.
The total maximum power dissipation of the MOSFET is
the sum of these two loss terms:
P FET(TOTAL) = P COND + P TRAN
To achieve high supply ef?ciency, keep the P FET(TOTAL) to
less than 3% of the total output power. Also, complete
a thermal analysis to ensure that the MOSFET junction
temperature is not exceeded.
T J = T A + P FET(TOTAL) ? θ JA
where θ JA is the package thermal resistance and T A is the
ambient temperature. Keep the calculated T J below the
maximum speci?ed junction temperature, typically 150°C.
Note that when V OUT is high (>20V), the transition losses
may dominate. A MOSFET with higher R DS(ON) and lower
C RSS may provide higher ef?ciency. MOSFETs 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
maximum voltage across the drain to the source of the
MOSFET, which is V OUT plus the forward voltage of the
recti?er, typically less than 1V.
external supply back driving V CC is not available such as
during start-up or short-circuit.
The manufacturer’s maximum continuous drain current
speci?cation should exceed the peak switch current which is
the same as the inductor peak current, I L(MAX) + Δ I L /2.
During the supply start-up, the gate drive levels are set by
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.
Boost Converter: Recti?er Selection
The recti?er is selected based upon the forward voltage,
reverse voltage and maximum current. A Schottky diode
is recommended for its low forward voltage and yields the
lowest power loss and highest ef?ciency. The maximum
reverse voltage that the diode will see is V OUT . The average
diode current is equal to the maximum output load current,
I OUT(MAX) . A diode rated at 1.5 to 2 times the maximum
average diode current is recommended. Remember boost
converters are not short-circuit protected.
Boost Converter: Output Capacitor Selection
In boost mode, the output capacitor requirements are
more demanding due to the fact that the current waveform
is pulsed instead of continuous as in a buck converter.
The choice of component(s) is driven by the acceptable
ripple voltage which is affected by the ESR, ESL and bulk
capacitance. The total output ripple voltage is:
Δ V OUT OUT ( MAX ) ?
= I
The internal V CC regulator is capable of sourcing up to
40mA which limits the maximum total MOSFET gate
? 1
? f SW ? C OUT
+
ESR ?
1 ? DC MAX ? ?
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
where the ?rst term is due to the bulk capacitance and the
second term due to the ESR.
3844fb
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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