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參數(shù)資料
| 型號： | SC604AIMLTRT |
| 廠商： | Semtech Corporation |
| 英文描述： | Low Noise, High Efficiency Regulated White LED Driver |
| 中文描述： | 低噪聲，高效率調(diào)控白光LED驅(qū)動器 |
| 文件頁數(shù)： | 11/18頁 |
| 文件大小： | 375K |
| 代理商： | SC604AIMLTRT |
11
2005 Semtech Corp.
www.semtech.com
SC604A
POWER MANAGEMENT
Methods for Setting LED Current (Cont.)
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Note: 1) “N” is the number of NMOS transistors used for brightness control.
Table 4 - Summary of LED Current Control
Figure 3 - PWM Example Circuit
Method 4.
LED current may also be controlled by applying a PWM
signal to any of the CTRL2, CTRL1 and CTRL0 inputs. The circuit in
Figure 3 turns 4 LEDs on and off by applying a PWM signal to the
CTRL0 input. This circuit uses resistor R
to set the on state
current and the average LED current is then proportional to the
percentage of on-time when the CTRL0 pin is a logic low. Average
LED current is approximately equal to:
I
AVG
= (t
ON
z
I
LED_ON
)/(t
ON
+ t
OFF
)
The recommended PWM frequency is between 100Hz and 500Hz.
Due to start up delay and ramp up time, frequency >500Hz will
result in error in the average value of I
. Frequency <100Hz can
naturally cause the LEDs to blink visibly.
In PWM applications where ILED4 is not used, keep ILED4 pin 13
open. Connecting ILED4 to ground can result in the charge pump
operating in open loop mode. Connecting ILED4 to V
will work
but will cause shutdown current I
Q
to increase to approximately
V
IN
/ 100k.
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相關(guān)代理商/技術(shù)參數(shù) |
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