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参数资料
| 型号： | LT1767EMS8-3.3 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 3 A SWITCHING REGULATOR, 1500 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | PLASTIC, MSOP-8 |
| 文件页数： | 11/16页 |
| 文件大小： | 242K |
| 代理商： | LT1767EMS8-3.3 |
11
LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
sn1767 1767fas
APPLICATIO
S I
N
FOR
ATIO
U
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
insufficient slope compensation. Application Note 19 has
more details on the theory of slope compensation.
W
U
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 maximum
efficiency, 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. Shorten-
ing this path will also reduce the parasitic trace inductance
of approximately 25nH/inch. At switch off, this parasitic
inductance produces a flyback spike across the LT1767
switch. When operating at higher currents and input
voltages, with poor layout, this spike can generate volt-
ages across the LT1767 that may exceed its absolute
maximum rating. A ground plane should always be used
under the switcher circuitry to prevent interplane coupling
and overall noise.
Board layout also has a significant effect on thermal
resistance. Soldering the exposed pad to as large a copper
area as possible and placing feedthroughs under the pad
to a ground plane, will reduce die temperature and in-
crease the power capacity of the LT1767. For the
nonexposed package, Pin 4 is connected directly to the
pad inside the package. Similar treatment of this pin will
result in lower die temperatures.
THERMAL CALCULATIONS
Power dissipation in the LT1767 chip comes from four
sources: switch DC loss, switch AC loss, boost circuit
current, and input quiescent current. The following
formulas show how to calculate each of these losses.
These formulas assume continuous mode operation, so
they should not be used for calculating efficiency at light
load currents.
Switch loss:
P
R
V
V
ns I
V
f
SW
SW OUT
OUT
IN
OUT
IN
=
) (
)
+
(
)( )( )
2
17
Boost current loss for V
BOOST
= V
OUT
:
P
V
I
V
BOOST
OUT
OUT
IN
=
(
)
2
50
/
Quiescent current loss:
(
R
SW
= Switch resistance (
≈
0.27
when hot)
17ns = Equivalent switch current/voltage overlap time
f = Switch frequency
Example: with V
IN
= 10V, V
OUT
= 5V and I
OUT
= 1A:
P
V
Q
IN
=
)
0 001
.
P
W
P
W
P
W
SW
BOOST
=
(
Q
=
(
)( ) ( )
+
(
+
=
( ) (
)
=
)
( )( )
(
)
=
)
=
0 27 1
.
5
10
17 10
1 10 1 25 10
0135
.
0 21 0 34
.
5
1 50
/
10
0 05
.
10 0 001
0 01
.
2
9
6
2
.
.
.
Figure 5. High Speed Switching Path
1767 F05
5V
L1
SW
V
IN
LT1767
D1
C1
C3
V
IN
HIGH
FREQUENCY
CIRCULATING
PATH
LOAD
The V
C
and FB components should be kept as far away as
possible from the switch and boost nodes. The LT1767
pinout has been designed to aid in this. The ground for
these components should be separated from the switch
current path. Failure to do so will result in poor stability or
subharmonic like oscillation.
相关PDF资料 |
PDF描述 |
|---|---|
| LT1767EMS8E-1.8 | SWITCH ROLLER LEVER |
| LT1767EMS8E-2.5 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1767EMS8-5 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1767 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LT1767-1.8 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1767EMS8-5 | 功能描述:IC REG BUCK 5V 1.5A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1767EMS8-5#PBF | 功能描述:IC REG BUCK 5V 1.5A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1767EMS8-5#PBF | 制造商:Linear Technology 功能描述:Switching Regulator IC |
| LT1767EMS8-5#TR | 功能描述:IC REG BUCK 5V 1.5A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1767EMS8-5#TRPBF | 功能描述:IC REG BUCK 5V 1.5A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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