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参数资料
| 型号： | LT1766IGN#TR |
| 厂商： | Linear Technology |
| 文件页数： | 18/30页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.5A 16SSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.2 V ~ 54 V |
| 输入电压： | 5.5 V ~ 60 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 1.5A |
| 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： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-SSOP |
| 其它名称： | LT1766IGNTR |
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LT1766/LT1766-5
APPLICATIONS INFORMATION
Keep the connections from the resistors to the shutdown
pin short and make sure that interplane or surface ca-
pacitance to the switching nodes are minimized. If high
resistor values are used, the shutdown pin should be
bypassed with a 1000pF capacitor to prevent coupling
problems from the switch node. If hysteresis is desired
in the undervoltage lockout point, a resistor, R FB , can
be added to the output node. Resistor values can be
calculated from:
compensation used to prevent subharmonic switching is
reduced. This type of subharmonic switching only occurs
at input voltages less than twice output voltage. Higher
inductor values will tend to eliminate this problem. See
Frequency Compensation section for a discussion of an
entirely different cause of subharmonic switching before
assuming that the cause is insuf?cient slope compensa-
tion. Application Note 19 has more details on the theory
of slope compensation.
R HI = R LO [ V IN ? 2 . 38 ( Δ V / V OUT + 1 ) + Δ V
2 . 38 ? R LO ( 5 . 5 μ A )
R FB = ( R HI ) ( V OUT / Δ V )
25k suggested for R LO
]
At power-up, when V C is being clamped by the FB pin (see
Figure 2, Q2), the sync function is disabled. This allows
the frequency foldback to operate in the shorted output
condition. During normal operation, switching frequency is
controlled by the internal oscillator until the FB pin reaches
0.6V, after which the SYNC pin becomes operational. If no
[ ( ) ]
2 . 38 – 25 k ( )
(
)
V IN = Input voltage at which switching stops as input
voltage descends to trip level
Δ V = Hysteresis in input voltage level
Example: output voltage is 5V, switching is to stop if input
voltage drops below 12V and should not restart unless input
rises back to 13.5V. Δ V is therefore 1.5V and V IN = 12V.
Let R LO = 25k.
25 k 12 ? 2 . 38 1 . 5 / 5 + 1 + 1 . 5
R HI =
5 . 5 μ A
= 25 k ( 10 . 41 ) = 116 k
2 . 24
R FB = 116 k 5 / 1 . 5 = 387 k
SYNCHRONIZING
The SYNC input must pass from a logic level low, through
synchronization is required, this pin should be connected
to ground.
LAYOUT CONSIDERATIONS
As with all high frequency switchers, when considering
layout, care must be taken in order to achieve optimal
electrical, thermal and noise performance. For maxi-
mum ef?ciency, switch rise and fall times are typically
in the nanosecond range. To prevent noise both radiated
and conducted, the high speed switching current path,
shown in Figure 5, must be kept as short as possible.
This is implemented in the suggested layout of Figure 6.
Shortening this path will also reduce the parasitic trace
inductance of approximately 25nH/inch. At switch off, this
parasitic inductance produces a ?yback spike across the
LT1766 switch. When operating at higher currents and
input voltages, with poor layout, this spike can generate
voltages across the LT1766 that may exceed its absolute
the maximum synchronization threshold with a duty cycle
between 10% and 90%. The input can be driven directly
LT1766
L1
5V
from a logic level output. The synchronizing range is equal
to initial operating frequency up to 700kHz. This means
HIGH
that minimum practical sync frequency is equal to the
worst-case high self-oscillating frequency (228kHz), not
V IN
C3
FREQUENCY
CIRCULATING
PATH
D1 C1
LOAD
the typical operating frequency of 200kHz. Caution should
be used when synchronizing above 265kHz because at
higher sync frequencies the amplitude of the internal slope
Figure 5. High Speed Switching Path
1766 F05
1766fc
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1766IGN-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:5.5V to 60V 1.5A, 200kHz Step-Down Switching Regulator |
| LT1767 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.4A, 500kHz Step-Down Switching Regulator |
| LT1767-1.8 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 1.5A, 1.25MHz Step-Down Switching Regulators |
| LT1767-2.5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 1.5A, 1.25MHz Step-Down Switching Regulators |
| LT1767-3.3 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 1.5A, 1.25MHz Step-Down Switching Regulators |
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