参数资料
| 型号： | LTC4081EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/24页 |
| 文件大小： | 0K |
| 描述： | IC USB POWER MANAGER 10-DFN |
| 标准包装： | 2,500 |
| 功能： | 电源管理 |
| 电池化学： | 锂离子（Li-Ion）、锂聚合物（Li-Pol） |
| 电源电压： | 3.75 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 供应商设备封装： | 10-DFN（3x3） |
| 包装： | 带卷 (TR) |
LTC4081
APPLICATIO S I FOR ATIO
Power conscious designs may want to use thermistors whose
room temperature value is greater than 10k. Vishay Dale has a
number of values of thermistor from 10k to 100k that follow
the “R-T Curve 1.” Using different R-T curves, such as Vishay
Dale “R-T Curve 2”, is also possible. This curve, combined with
LTC4081 internal thresholds, gives temperature trip points of
The nearest 1% value for R NOM is 8.66k. This is the value used
to bias the NTC thermistor to get cold and hot trip points of
approximately 0°C and 40°C respectively. To extend the delta
between the cold and hot trip points, a resistor, R1, can be
added in series with R NTC (see Figure 5). The values of the
resistors are calculated as follows:
R NOM =
R 1 = ?
approximately0°C(falling)and40°C(rising),adeltaof40°C.
This delta in temperature can be moved in either direction by
changing the value of R NOM with respect to R NTC . Increasing
R NOM will move both trip points to higher temperatures. To
calculate R NOM for a shift to lower temperature for example,
use the following equation:
R COLD ? R HOT
3 . 266 ? 0 . 5325
? 0 . 5325 ?
? 3 . 266 ? 0 . 5325 ? ?
? ( R COLD ? R HOT ) ? R HOT
R NOM =
R COLD
3 . 266
? R NTC at 25 ° C
where R NOM is the value of the bias resistor and R HOT and
R COLD are the values of R NTC at the desired temperature trip
points. Continuing the example from before with a desired
R NOM =
? R NTC at 25 ° C
R COLD ? R HOT 10 k ? ( 2 . 816 ? 0 .44086 )
R NOM = =
? ( 2 . 816 ? 0 . 4086 ) ? 0 . 4086
R 1 = 10 k ? ?
whereR COLD istheresistanceratioofR NTC atthedesiredcold
temperature trip point. If you want to shift the trip points to
higher temperatures use the following equation:
R HOT
0 . 5325
where R HOT is the resistance ratio of R NTC at the desired hot
temperature trip point.
Here is an example using a 100k R-T Curve 2 thermistor
from Vishay Dale. The difference between the trip points is
40°C, from before, and we want the cold trip point to be 0°C,
trip point of 50°C:
3 . 266 ? 0 . 5325 3 . 266 ? 0 . 5325
= 8 . 8 k , 8 . 87 k is the nearest 1 % value .
? 0 . 5325 ?
? 3 . 26 6 ? 0 . 5325 ? ?
= 604 Ω , 604 is the nearest 1 % value .
V CC
R NOM
which would put the hot trip point at 40°C. The R NOM needed
is calculated as follows:
8.87k
0.76 ? V CC
TOO COLD
R NOM =
R COLD
3 . 266
? R NTC at 25 ° C
R1
604 Ω
6
NTC
=
2 . 816
3 . 266
? 10 k = 8 . 62 k
T
R NTC
10k
TOO HOT
0.35 ? V CC
+
NTC_ENABLE
0.016 ? V CC
–
4081 F05
Figure 5. NTC Circuits
4081f
19
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| LTC4085 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency Battery Charger/USB Power Manager |
| LTC4085-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:USB Power Manager with Ideal Diode Controller and 4.1V Li-Ion Charger |
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