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参数资料
| 型号： | LT3844IFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/24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
it advisable to further derate the capacitor or to choose a
capacitor rated at a higher temperature than required.
The combination of aluminum electrolytic capacitors and
Output Voltage Programming
A resistive divider sets the DC output voltage according
to the following formula:
R 2 = R 1 ?
– 1 ?
ceramic capacitors is an economical approach to meet-
ing the input capacitor requirements. The capacitor volt-
age rating must be rated greater than V IN(MAX) . Multiple
? V OUT
? 1 . 231 V
?
?
capacitors may also be paralleled to meet size or height
requirements in the design. Locate the capacitor very close
to the MOSFET switch and use short, wide PCB traces to
minimize parasitic inductance.
Step-Down Converter: Output Capacitor Selection
The external resistor divider is connected to the output
of the converter as shown in Figure 2. Tolerance of the
feedback resistors will add additional error to the output
voltage.
Example: V OUT = 12V; R1 = 10k
R 2 = 10 k ?
? 1 ? = 87 . 48 k ? use 86 . 6 k 1 %
The output capacitance, C OUT , selection is based on the
design’s output voltage ripple, Δ V OUT and transient load
requirements. Δ V OUT is a function of Δ I L and the C OUT
? 12 V
? 1 . 231 V
?
?
Δ V OUT
= Δ I L ? ? ESR +
ESR. It is calculated by:
?
?
1 ?
?
( 8 ? f SW ? C OUT ) ?
The V FB pin input bias current is typically 25nA, so use
of extremely high value feedback resistors could cause a
converter output that is slightly higher than expected. Bias
current error at the output can be estimated as:
The maximum ESR required to meet a Δ V OUT design
requirement can be calculated by:
Δ V OUT(BIAS) = 25nA ? R2
V OUT ?
V IN ( MAX ) ?
?
ESR ( MAX ) =
( Δ V OUT )( L )( f SW )
?
V OUT ? ? 1 – ?
Supply UVLO and Shutdown
The SHDN pin has a precision voltage threshold with
hysteresis which can be used as an undervoltage lockout
threshold (UVLO) for the power supply. Undervoltage
Worst-case Δ V OUT occurs at highest input voltage. Use
paralleled multiple capacitors to meet the ESR require-
ments. Increasing the inductance is an option to lower
the ESR requirements. For extremely low Δ V OUT , an ad-
ditional LC ?lter stage can be added to the output of the
lockout keeps the LT3844 in shutdown until the supply
input voltage is above a certain voltage programmed by
the user. The hysteresis voltage prevents noise from falsely
tripping UVLO.
Resistors are chosen by ?rst selecting R B . Then:
? V SUPPLY ( ON )
R A B ? ?
?
– 1 ?
supply.ApplicationNote44hassomegoodtipsonsizing
an additional output ?lter.
L1
V OUT
= R
1 . 35 V
V SUPPLY
?
?
R2
C OUT
R A
V FB PIN
R1
3844 F02
Figure 2. Output Voltage Feedback Divider
SHDN PIN
R B
3844 F03
Figure 3. Undervoltage Lockout Circuit
3844fb
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3845 | 制造商:Cooper Crouse-Hinds 功能描述: |
| LT3845_1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
| LT3845A | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage, Current Mode Switching Regulator Controller Thermal Shutdown |
| LT3845AEFE#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 |
| LT3845AEFE#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 500kHz TSSOP16 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 500kHz, TSSOP16 |
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