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| 型号： | LT3957EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/28页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 36VQFN |
| 特色产品： | LT?3957/LT?3958 Converters |
| 标准包装： | 61 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.6 V ~ 40 V |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz ~ 1MHz |
| 电流 - 输出： | 5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
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LT3957
APPLICATIONS INFORMATION
The Internal Power Switch Current
For control and protection, the LT3957 measures the
internal power MOSFET current by using a sense resistor
(R SENSE ) between GND and the MOSFET source. Figure 3
shows a typical waveform of the internal switch current
(I SW ).
Due to the current limit (minimum 5A) of the internal power
switch, the LT3957 should be used in the applications
that the switch peak current I SW(PEAK) during steady state
normal operation is lower than 5A by a suf?cient margin
(10% or higher is recommended).
The LT3957 switching controller incorporates 100ns
timing interval to blank the ringing on the current sense
signal across R SENSE immediately after M1 is turned on.
This ringing is caused by the parasitic inductance and
capacitance of the PCB trace, the sense resistor, the diode,
and the MOSFET. The 100ns timing interval is adequate
for most of the LT3957 applications. In the applications
that have very large and long ringing on the current sense
signal, a small RC ?lter can be added to ?lter out the excess
ringing. Figure 4 shows the RC ?lter on the SENSE1 and
SENSE2 pins. It is usually suf?cient to choose 22Ω for
R FLT and 2.2nF to 10nF for C FLT . Keep R FLT ’s resistance
low. Remember that there is 65μA (typical) ?owing out of
the SENSE2 pin. Adding R FLT will affect the internal power
switch current limit threshold:
On-Chip Power Dissipation and Thermal Lockout (TLO)
The on-chip power dissipation of LT3957 can be estimated
using the following equation:
P IC ≈ I 2SW ? D ? R DS(ON) + V 2PEAK ? I SW ? ? ? 200pF/A +
V IN ? (1.6mA + ? ? 10nC)
where R DS(ON) is the internal switch on-resistance which
can be obtained from the Typical Performance Characteris-
tics section. V SW(PEAK) is the peak switch off-state voltage.
The maximum power dissipation P IC(MAX) can be obtained
by comparing P IC across all the V IN range at the maximum
output current . The highest junction temperature can be
estimated using the following equation:
T J(MAX) ≈ T A + P IC(MAX) ? 42°C/W
It is recommended to measure the IC temperature in steady
state to verify that the junction temperature limit is not
exceeded. A low switching frequency may be required to
ensure T J(MAX) does not exceed 125°C.
If LT3957 die temperature reaches thermal lockout
threshold at 165°C (typical), the IC will initiate several
protective actions. The power switch will be turned off.
A soft-start operation will be triggered. The IC will be en-
abled again when the junction temperature has dropped
by 5°C (nominal).
LT3957
I SW _ILIM = ? 1 ?
? ? ? 5A
?
?
65μA ? R FLT ?
48mV
SENSE1
SENSE2
R FLT
C FLT
SGND
I SW
DT S
I SW
I SW(PEAK)
t
3957 F04
Figure 4. The RC Filter on SENSE1 Pin and SENSE2 Pin
T S
3957 F03
Figure 3. The Switch Current During a Switching Cycle
3957f
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3957EUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3957IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3957IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
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