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参数资料
| 型号： | LT1767-5 |
| 厂商： | Linear Technology Corporation |
| 元件分类： | 基准电压源/电流源 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 抗辐射高效，5安培开关稳压器 |
| 文件页数： | 10/16页 |
| 文件大小： | 242K |
| 代理商： | LT1767-5 |
10
LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
sn1767 1767fas
suitable, but the ESR should be <1
to ensure it can be
fully recharged during the off time of the switch. The
capacitor value is derived from worst-case conditions of
700ns on-time, 50mA boost current, and 0.7V discharge
ripple. This value is then guard banded by 2x for secondary
factors such as capacitor tolerance, ESR and temperature
effects. The boost capacitor value could be reduced under
less demanding conditions, but this will not improve
circuit operation or efficiency. Under low input voltage and
low load conditions, a higher value capacitor will reduce
discharge ripple and improve start up operation.
SHUTDOWN AND UNDERVOLTAGE LOCKOUT
Figure 4 shows how to add undervoltage lockout (UVLO)
to the LT1767. Typically, UVLO is used in situations where
the input supply is current limited or has a relatively high
source resistance. A switching regulator draws constant
power from the source, so source current increases as
source voltage drops. This looks like a negative resistance
load to the source and can cause the source to current limit
or latch low under low source voltage conditions. UVLO
prevents the regulator from operating at source voltages
where these problems might occur.
R
V
V
A
R
V
)
+ μ
V
V
R
A
H
7
L
H
1
2
1 33
1 33
.
1
3
=
μ
=
(
.
V
H
– Turn-on threshold
V
L
– Turn-off threshold
Example: switching should not start until the input is
above 4.75V and is to stop if the input falls below 3.75V.
V
H
= 4.75V
V
L
= 3.75V
R
V
7
V
A
k
R
V
V
V
k
A
k
1
4 75
.
3 75
.
143
2
1 33
1 33
.
4 75
.
143
3
49 4
=
μ
=
=
(
)
+ μ
=
.
.
Keep the connections from the resistors to the SHDN pin
short and make sure that the interplane or surface capaci-
tance to the switching nodes are minimized. If high resis-
tor values are used, the SHDN pin should be bypassed with
a 1nF capacitor to prevent coupling problems from the
switch node.
SYNCHRONIZATION
The SYNC pin, is used to synchronize the internal oscilla-
tor to an external signal. The SYNC input must pass from
a logic level low, through the maximum synchronization
threshold with a duty cycle between 20% and 80%. The
input can be driven directly from a logic level output. The
synchronizing range is equal to initialoperating frequency
up to 2MHz. This means that minimumpractical sync
frequency is equal to the worst-case highself-oscillating
frequency (1.5MHz), not the typical operating frequency
of 1.25MHz. Caution should be used when synchronizing
above 1.6MHz because at higher sync frequencies the
amplitude of the internal slope compensation used to
APPLICATIO
S I
N
FOR
ATIO
U
W
U
1.33V
GND
V
SW
V
IN
R1
1767 F04
OUTPUT
SHDN
V
CC
IN
LT1767
3
μ
A
R2
C1
+
7
μ
A
Figure 4. Undervoltage Lockout
An internal comparator will force the part into shutdown
below the minimum V
IN
of 2.6V. This feature can be used
to prevent excessive discharge of battery-operated sys-
tems. If an adjustable UVLO threshold is required, the
shutdown pin can be used. The threshold voltage of the
shutdown pin comparator is 1.33V. A 3
μ
A internal current
source defaults the open pin condition to be operating (see
Typical Performance Graphs). Current hysteresis is added
above the SHDN threshold. This can be used to set voltage
hysteresis of the UVLO using the following:
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| LT1767EMS8#PBF | 功能描述:IC REG BUCK ADJ 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#TRPBF | 功能描述:IC REG BUCK ADJ 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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