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AD8240YRM-REEL 参数 Datasheet PDF下载

AD8240YRM-REEL图片预览
型号: AD8240YRM-REEL
PDF下载: 下载PDF文件 查看货源
内容描述: LED驱动器/监控器 [LED Driver/Monitor]
分类和应用: 驱动器监控
文件页数/大小: 12 页 / 258 K
品牌: AD [ ANALOG DEVICES ]
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AD8240
USING/EVALUATING THE AD8240 LED DRIVER MONITOR
Shunt Resistor Selection
The shunt resistor is chosen by the equation
SETUP
In order to set up and evaluate the AD8240, the following
components and equipment are needed:
A shunt resistor (typically 0.1 Ω to 0.5 Ω depending on the
load). See the Shunt Resistor Selection section.
A transistor (the type depends on the load)
Two capacitors
LED load
5 V reference voltage
9 V to 27 V supply
Oscilloscope
Digital voltmeter (DVM)
R
SHUNT
0.2 V
I
LOAD
For example if the load is expected to be 500 mA, the shunt
value should be equal to or less than 0.4 Ω. This keeps the
output of the current sense amplifier from being greater than
4.8 V in normal operation to prevent noise from causing the
output to latch off.
Circuit Configuration
Connect the pass transistor, capacitors, and LED load(s) as
shown in Figure 3. It is important to note that the value of C
M
should be at least 22 nF to ensure circuit stability.
The LED lamp should be configured to expect 12 V. This is
the result of selecting the series/parallel combinations of LEDs
and series resistors. The series resistors can be used to adjust
for LED supplier brightness variations from lot to lot.
Connect 5 V to Pin 2 (5 V reference) and at least 9 V to Pin 5
(V
PLUS
). It may be necessary to raise the V
PLUS
voltage to more
than 13 V, depending on the drop across the pass transistor, for
the output to be regulated at 12 V. This varies according to the
application and the pass transistor type.
.
R
SHUNT
V
BATT
V
PLUS
5
C
M
SHUNT
6
7
CL
47nF
V
O
8
BASE 22nF
R
SENSE
V
SENSE
1
10k
5V
REFERENCE
2
R1
350k
LATCH-OFF
DRIVER
PWM
3
R2
250k
04824-0-003
4
GND
Figure 3. Connections for Typical Applications
Rev. 0 | Page 6 of 12