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| 型号： | LT1767EMS8-2.5 |
| 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： | 13/16页 |
| 文件大小： | 242K |
| 代理商： | LT1767EMS8-2.5 |
13
LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
sn1767 1767fas
APPLICATIO
S I
N
FOR
ATIO
U
Notice that the catch diode’s forward voltage contributes
a significant loss in the overall system efficiency. A larger,
lower V
F
diode can improve efficiency by several percent.
P
INDUCTOR
= (I
LOAD
) (L
DCR
)
L
DCR
= Inductor DC resistance (assume 0.1
)
P
INDUCTOR
= (1) (0.1) = 0.1W
Typical thermal resistance of the board is 35
°
C/W. At an
ambient temperature of 65
°
C,
T
j
= 65 + 40 (0.4) + 35 (0.39) = 95
°
C
If a true die temperature is required, a measurement of the
SYNC to GND pin resistance can be used. The SYNC pin
resistance across temperature must first be calibrated,
with no device power, in an oven. The same measurement
can then be used in operation to indicate the die tempera-
ture.
W
U
FREQUENCY COMPENSATION
Before starting on the theoretical analysis of frequency
response, the following should be remembered – the
worse the board layout, the more difficult the circuit will be
to stabilize. This is true of almost all high frequency analog
circuits, read the ‘LAYOUT CONSIDERATIONS’ section
first. Common layout errors that appear as stability prob-
lems are distant placement of input decoupling capacitor
and/or catch diode, and connecting the V
C
compensation
to a ground track carrying significant switch current. In
addition, the theoretical analysis considers only first order
non-ideal component behavior. For these reasons, it is
important that a final stability check is made with produc-
tion layout and components.
The LT1767 uses current mode control. This alleviates
many of the phase shift problems associated with the
inductor. The basic regulator loop is shown in Figure 7,
with both tantalum and ceramic capacitor equivalent cir-
cuits. The LT1767 can be considered as two g
m
blocks, the
error amplifier and the power stage.
Figure 8 shows the overall loop response with a 330pF V
C
capacitor and a typical 100
μ
F tantalum output capacitor.
The response is set by the following terms:
Error amplifier:
DC gain set by g
m
and R
L
= 850
μ
500k=425.
Pole set by C
F
and R
L
= (2
π
500k 330p)
–1
= 965Hz.
Unity-gain set by C
F
and g
m
= (2
π
330p 850
μ
–1
)
–1
=
410kHz.
Power stage:
DC gain set by g
m
and R
L
(assume 10
) = 2.5 10 = 25.
Pole set by C
OUT
and R
L
= (2
π
100
μ
10)
–1
= 159Hz.
Unity-gain set by C
OUT
and g
m
= (2
π
100
μ
2.5
–1
)
–1
=
3.98kHz.
Tantalum output capacitor:
Zero set by C
OUT
and C
ESR
= (2
π
100
μ
0.1)
–1
= 15.9kHz.
Figure 8. Overall Loop Response
Figure 7. Model for Loop Response
–
+
1.2V
V
SW
V
C
LT1767
GND
1767 F07
R1
OUTPUT
ESR
C
F
C
C
R
C
500k
ERROR
AMPLIFIER
FB
R2
C1
CURRENT MODE
POWER STAGE
g
m
= 2.5mho
g
m
=
850
μ
mho
+
ESL
CERAMIC
TANTALUM
C1
FREQUENCY (Hz)
G
80
60
40
20
0
–20
–40
P
180
150
120
90
60
30
0
1767 F10
GAIN
PHASE
V
OUT
= 5V
C
OUT
= 100
μ
F, 0.1
C
C
= 330pF
R
C
/C
F
= N/C
I
LOAD
= 500mA
10
1k
10k
1M
100
100k
相关PDF资料 |
PDF描述 |
|---|---|
| LT1767EMS8-3.3 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
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| LT1767EMS8E-2.5 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
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| LT1767 | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1767EMS8-3.3 | 功能描述:IC REG BUCK 3.3V 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 |
| LT1767EMS8-3.3#PBF | 功能描述:IC REG BUCK 3.3V 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 |
| LT1767EMS8-3.3#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LT1767EMS8-3.3#TR | 功能描述:IC REG BUCK 3.3V 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 |
| LT1767EMS8-3.3#TRPBF | 功能描述:IC REG BUCK 3.3V 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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