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参数资料
| 型号： | LT3758EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK INV 10DFN |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 电源电压： | 5.5 V ~ 100 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 |
| 产品目录页面： | 1340 (CN2011-ZH PDF) |
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LT3758/LT3758A
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. The LT3758 contains an undervoltage
lockout comparator A8 and an overvoltage lockout com-
parator A9 for the INTV CC supply. The INTV CC undervoltage
(UV) threshold is 4.5V (typical), with 0.5V hysteresis, to
ensure that the MOSFETs have sufficient gate drive voltage
before turning on. The logic circuitry within the LT3758 is
also powered from the internal INTV CC supply.
The INTV CC overvoltage 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 overvolt-
age threshold, 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 im-
mediately adjacent to the IC pins with a minimum of 4.7μF
ceramic 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 LT3758 does not exceed its
maximum junction temperature rating. The junction tem-
perature T J can be estimated using the following equations:
T J = T A + P IC ? θ JA
T A = ambient temperature
The LT3758 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 LT3758 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 LT3758 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
4.7V INTV CC is shown in Figure 2.
140
300kHz
120
100
80
60
θ JA = junction-to-ambient thermal resistance
P IC = IC power consumption
40
20
1MHz
= V IN ? ( I Q + I DRIVE )
I Q = V IN operation I Q = 1.6mA
0
1
10
V IN (V)
100
3758 F02
I DRIVE = average gate drive current = f ? Q G
f = switching frequency
Figure 2. Recommended Maximum Q G vs V IN at Different
Frequencies to Ensure INTV CC Higher Than 4.7V
Q G = power MOSFET total gate charge
3758afd
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| LT3758EMSE#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) |
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