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参数资料
| 型号： | LT1766IGN#TR |
| 厂商： | Linear Technology |
| 文件页数： | 22/30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
For output voltages of 5V, V C2 is approximately 5V. During
switch turn on, V C2 will fall as the boost capacitor C2 is
dicharged by the BOOST pin. In the previous BOOST Pin
section, the value of C2 was designed for a 0.7V droop in
V C2 = V DROOP . Hence, an output voltage as low as 4V would
still allow the minimum 3.3V for the boost function using
the C2 capacitor calculated. If a target output voltage of
12V is required, however, an excess of 8V is placed across
the boost capacitor which is not required for the boost
function but still dissipates additional power.
What is required is a voltage drop in the path of D2 to
achieve minimal power dissipation while still maintaining
minimum boost voltage across C2. A zener, D4, placed in
series with D2 (see Figure 9), drops voltage to C2.
Example : the BOOST pin power dissipation for a 20V input
to 12V output conversion at 1A is given by:
For an FE package with thermal resistance of 45°C/W,
ambient temperature savings would be, T(ambient) savings
= 0.116W ? 45°C/W = 5c. For a GN Package with thermal
resistance of 85°C/W, ambient temperature savings would
be T/(ambient) savings = 0.116 ? 85°C/W = 10c. The 7V
zener should be sized for excess of 0.116W operation. The
tolerances of the zener should be considered to ensure
minimum V C2 exceeds 3.3V + V DROOP .
Input Voltage vs Operating Frequency Considerations
The absolute maximum input supply voltage for the
LT1766 is speci?ed at 60V. This is based solely on internal
semiconductor junction breakdown effects. Due to internal
power dissipation, the actual maximum V IN achievable in
a particular application may be less than this.
A detailed theoretical basis for estimating internal power
P BOOST =
12 ? (1 / 36) ? 12
20
= 0 . 2 W
loss is given in the section, Thermal Considerations. Note
that AC switching loss is proportional to both operating
frequency and output current. The majority of AC switching
If a 7V zener D4 is placed in series with D2, then power
dissipation becomes :
loss is also proportional to the square of input voltage.
For example, while the combination of V IN = 40V, V OUT
= 5V at 1A and f OSC = 200kHz may be easily achievable,
P BOOST =
12 ? (1 / 36) ? 5
20
= 0 . 084 W
D2
D2
D4
simultaneously raising V IN to 60V and f OSC to 700kHz is
not possible. Nevertheless, input voltage transients up to
60V can usually be accommodated, assuming the result-
ing increase in internal dissipation is of insuf?cient time
duration to raise die temperature signi?cantly.
A second consideration is controllability. A potential limita-
tion occurs with a high step-down ratio of V IN to V OUT , as
Min t ON =
V IN
C3
BOOST
V IN
LT1766
SHDN
SYNC
GND
SW
BIAS
FB
V C
C2
D1
L1
R1
R2
+
V OUT
C1
this requires a correspondingly narrow minimum switch
on time. An approximate expression for this (assuming
continuous mode operation) is given as follows:
V OUT + V F
V IN ( f OSC )
where:
V IN = Input voltage
R C
C C
C F
V OUT = Output voltage
V F = Schottky diode forward drop
f OSC = Switching frequency
1766 F09
Figure 9. Boost Pin, Diode Selection
A potential controllability problem arises if the LT1766 is
called upon to produce an on time shorter than it is able
to produce. Feedback loop action will lower then reduce
1766fc
22
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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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