参数资料
型号: MIC3289-24YD6 TR
厂商: Micrel Inc
文件页数: 10/15页
文件大小: 0K
描述: IC LED DRIVR WHITE BCKLGT TSOT-6
标准包装: 1
恒定电流:
拓扑: PWM,升压(升压)
输出数: 1
内部驱动器:
类型 - 主要: 背光,闪灯/白光
类型 - 次要: 白色 LED
频率: 1MHz ~ 1.35MHz
电源电压: 2.5 V ~ 6.5 V
安装类型: 表面贴装
封装/外壳: SOT-23-6 细型,TSOT-23-6
供应商设备封装: TSOT-23-6
包装: 标准包装
工作温度: -40°C ~ 125°C
产品目录页面: 1082 (CN2011-ZH PDF)
其它名称: 576-3041-6
Micrel, Inc.
To change the state back to Count Down Mode, pull the
DC pin low for a period equal to t MODE_DOWN (420μs to
500μs). Now the internal circuitry will remain in Count
Down Mode until changed to Count Up as described
previously.
MIC3289
shown in Figure 7 below. When issuing multiple
brightness level adjustment commands to the DC pin,
ensure both t PROG_LOW and t PROG_HIGH are within 1μs and
32μs.
To maintain operation at the current brightness level
simply maintain a logic level high signal at the DC pin.
Figure 5. Mode Change to Count Down
Programming the Brightness Level
MIC3289 is designed to start driving the output LEDs
(t START_UP ) in 140μs at the maximum brightness level of
15. After start up, the internal control logic is ready to
decrease the LED brightness upon receiving
programming pulses (negative edges applied to DC pin).
Since MIC3289 starts in Count Down Mode, the
brightness level is decreased one level by applying two
programming pulses, as shown in Figure 6. Each
programming pulse has a high (t PROG_HIGH ) and a low
(t PROG_LOW ) pulse width that must be between 1μs to
32μs. Note that n+1 number of pulses are needed to
decrease brightness by n level(s) since the first clock
pulse is ignored. Ignoring the first clock pulse is
necessary in order that Mode Change (t MODE_UP ,
t MODE_DOWN ) pulses do not result in adjustments to the
Figure 7. Decreasing Brightness Several Levels
As mentioned, MIC3289 can be programmed to set LED
drive current to produce one of 16 distinct brightness
levels. The internal logic keeps track of the brightness
level with an Up/Down counter circuit. The following
section explains how the brightness counter functions
with continued programming edges.
Counter Roll-Over
The MIC3289 internal up/down counter contains
registers from 0 to 15. When the brightness level is at 0
and a programming pulse forces the brightness to step
down, then the counter will roll-over to level 15. This is
illustrated in Figure 8 below.
brightness level. The MIC3289 internal circuit can be
changed from Count Down Mode to Count Up Mode and
DC:
Edge Ignored
vice versa. The user may elect to send a Mode Change
as shown in Figure 4 to set the MIC3289 to step up the
DOWN
COUNT
6
6
5
4
3
2
1
0
15
14
13
12
brightness level with subsequent programming pulses.
For proper operation, ensure the DC pin has remained
high for at least t DELAY (140μs) before issuing a mode
change command.
15
OUTPUT
LEVEL
0
Figure 8. Down Counter Roll-over
Similarly, when the counter mode is set to Count Up and
a programming pulse forces the brightness level to step
up from level 15, then the counter will roll-over to level 0
as illustrated in figure 9.
Figure 6. Brightness Programming Pulses
Brightness programming pulses are not restricted to just
one pair at a time. Multiple level changes can be set as
June 2007
10
M9999-061807
(408) 944-0800
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