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| 型号： | LT3759HMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST INV PWM 12-MSOP |
| 标准包装： | 37 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 1.6 V ~ 42 V |
| 降压： | 无 |
| 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 ~ 150°C |
| 封装/外壳： | 12-TSSOP （0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 管件 |
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LT3759
APPLICATIONS INFORMATION
T SS = C SS ?
Besides start-up, soft-start can also be triggered by
INTV CC undervoltage lockout and/or thermal lockout, which
causes the LT3759 to stop switching immediately. The SS
pin will be discharged by Q3. When all faults are cleared
and the SS pin has been discharged below 0.2V, a 10μA
current source I S2 starts charging the SS pin, initiating a
soft-start operation.
The soft-start interval is set by the soft-start capacitor
selection according to the equation:
1.25V
10μA
FBX Frequency Foldback
When V OUT is very low during start-up or a short-circuit
fault on the output, the switching regulator must operate
at low duty cycles to maintain the power switch current
within the current limit range, since the inductor current
decay rate is very low during switch off time. The minimum
on-time limitation may prevent the switcher from attaining
a sufficiently low duty cycle at the programmed switch-
ing frequency. So, the switch current will keep increasing
through each switch cycle, exceeding the programmed
current limit. To prevent the switch peak currents from
exceeding the programmed value, the LT3759 contains
a frequency foldback function to reduce the switching
frequency when the FBX voltage is low (see the Normal-
ized Switching Frequency vs FBX graph in the Typical
Performance Characteristics section).
Some frequency foldback waveforms are shown in the
Typical Applications section. The frequency foldback func-
tion prevents I L from exceeding the programmed limits
because of the minimum on-time.
Loop Compensation
Loop compensation determines the stability and transient
performance. The LT3759 uses current mode control to
regulate the output which simplifies loop compensation.
The optimum values depend on the converter topology, the
component values and the operating conditions (including
the input voltage, load current, etc.). To compensate the
feedback loop of the LT3759, a series resistor-capacitor
network is usually connected from the VC pin to GND.
Figure 1 shows the typical VC compensation network. For
most applications, the capacitor should be in the range of
470pF to 22nF, and the resistor should be in the range of
5k to 50k. A small capacitor is often connected in paral-
lel with the RC compensation network to attenuate the
VC voltage ripple induced from the output voltage ripple
through the internal error amplifier. The parallel capacitor
usually ranges in value from 10pF to 100pF. A practical
approach to design the compensation network is to start
with one of the circuits in this data sheet that is similar
to your application, and tune the compensation network
to optimize the performance. Stability should then be
checked across all operating conditions, including load
current, input voltage and temperature.
SENSE Pin Programming
For control and protection, the LT3759 measures the
power MOSFET current by using a sense resistor (R SENSE )
between GND and the MOSFET source. Figure 2 shows a
typical wave-form of the sense voltage (V SENSE ) across the
sense resistor. It is important to use Kelvin traces between
the SENSE pin and R SENSE , and to place the IC GND as
close as possible to the GND terminal of the R SENSE for
proper operation.
During frequency foldback, external clock synchronization
is disabled to allow the frequency reducing operation to
function properly.
V SENSE
V SENSE(MAX)
Δ V SENSE = χ ? V SENSE(MAX)
V SENSE(PEAK)
DT S
ThermalLockout
If the LT3759 die temperature reaches 165°C (typical),
the part will go into thermal lockout. The power switch
will be turned off. A soft-start operation will be triggered.
The part will be enabled again when the die temperature
has dropped by 5°C (nominal).
t
T S
3759 F02
Figure 2. The Sense Voltage During a Switching Cycle
3759fc
12
For more information www.linear.com/3759
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| LT3759IMSE#PBF | 功能描述:IC REG CTRLR BST INV PWM 12-MSOP 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) |
| LT3759IMSE#TRPBF | 功能描述:IC REG CTRLR BST INV PWM 12-MSOP 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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| LT375-C | 制造商:EDSYN 功能描述: |
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