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参数资料
| 型号： | LT3757IDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK INV 10DFN |
| 产品培训模块： | LT3757 and LT3758 - Boost, Flyback, SEPIC and Inverting Controllers |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 2.9 V ~ 40 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
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LT3757/LT3757A
APPLICATIONS INFORMATION
(T J ? T A ) 1.28W
( θ JA ? V IN )
I DRIVE(MAX) = ? I Q = ? 1.6mA
INTV CC RegulatorBypassingandOperation
An internal, low dropout (LDO) voltage regulator produces
the 7.2V INTV CC supply which powers the gate driver,
as shown in Figure 1. If a low input voltage operation is
expected (e.g., supplying power from a lithium-ion battery
or a 3.3V logic supply), low threshold MOSFETs should
be used. The LT3757 contains an undervoltage lockout
comparator A8 and an overvoltage lockout comparator
A9 for the INTV CC supply. The INTV CC undervoltage (UV)
threshold is 2.7V (typical), with 100mV hysteresis, to
ensure that the MOSFETs have sufficient gate drive voltage
before turning on. The logic circuitry within the LT3757 is
also powered from the internal INTV CC supply.
The INTV CC overvoltage (OV) threshold is set to be 17.5V
(typical) to protect the gate of the power MOSFET. When
INTV CC is below the UV threshold, or above the OV thresh-
old, the GATE pin will be forced to GND and the soft-start
operation will be triggered.
The INTV CC regulator must be bypassed to ground imme-
diately adjacent to the IC pins with a minimum of 4.7μF cera-
mic capacitor. Good bypassing is necessary to supply the
high transient currents required by the MOSFET gate driver.
In an actual application, most of the IC supply current is
used to drive the gate capacitance of the power MOSFET.
The on-chip power dissipation can be a significant concern
when a large power MOSFET is being driven at a high fre-
quency and the V IN voltage is high. It is important to limit
the power dissipation through selection of MOSFET and/
or operating frequency so the LT3757 does not exceed its
maximum junction temperature rating. The junction tem-
perature T J can be estimated using the following equations:
The LT3757 uses packages with an Exposed Pad for en-
hanced thermal conduction. With proper soldering to the
Exposed Pad on the underside of the package and a full
copper plane underneath the device, thermal resistance
( θ JA ) will be about 43°C/W for the DD package and 40°C/W
for the MSE package. For an ambient board temperature of
T A = 70°C and maximum junction temperature of 125°C,
the maximum I DRIVE (I DRIVE(MAX) ) of the DD package can
be calculated as:
V IN
The LT3757 has an internal INTV CC I DRIVE current limit
function to protect the IC from excessive on-chip power
dissipation. The I DRIVE current limit decreases as the V IN
increases (see the INTV CC Minimum Output Current vs V IN
graph in the Typical Performance Characteristics section).
If I DRIVE reaches the current limit, INTV CC voltage will fall
and may trigger the soft-start.
Based on the preceding equation and the INTV CC Minimum
Output Current vs V IN graph, the user can calculate the
maximum MOSFET gate charge the LT3757 can drive at
a given V IN and switch frequency. A plot of the maximum
Q G vs V IN at different frequencies to guarantee a minimum
4.5V INTV CC is shown in Figure 2.
As illustrated in Figure 2, a trade-off between the operating
frequency and the size of the power MOSFET may be needed
in order to maintain a reliable IC junction temperature.
300
250
T J = T A + P IC ? θ JA
T A = ambient temperature
θ JA = junction-to-ambient thermal resistance
P IC = IC power consumption
= V IN ? ( I Q + I DRIVE )
200
150
100
50
300kHz
1MHz
I Q = V IN operation I Q = 1.6mA
I DRIVE = average gate drive current = f ? Q G
0
0
5
10
15
20
V IN (V)
25
30
35
40
3757 F02
f = switching frequency
Q G = power MOSFET total gate charge
10
Figure 2. Recommended Maximum Q G vs V IN at Different
Frequencies to Ensure INTV CC Higher Than 4.5V
3757afd
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3757IDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Controller |
| LT3757IMSE | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Flyback Controller 2.9V to 40V Input 10-Pin MSOP EP 制造商:Linear Technology 功能描述:CONTROLLER |
| LT3757IMSE#PBF | 功能描述:IC REG CTRLR PWM CM 10-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) |
| LT3757IMSE#TRPBF | 功能描述:IC REG CTRLR PWM CM 10-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) |
| LT3757IMSEPBF | 制造商:Linear Technology 功能描述:Boost Flyback SEPIC Controller MSOP10EP |
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