MIC3289 Datasheet, PDF (9/13 Pages) Micrel Semiconductor – 1.2MHz PWM White LED Driver with Internal Schottky Diode and True 1-Wire Digital Control

Micrel, Inc.
MIC3289
Figure 1. MIC3289 Logic State Diagram
With an input supply voltage between 2.5V and 6.5V and
a logic-level LOW applied to the DC pin, the MIC3289
will enter State 0, Shutdown, and remain there
consuming less than 1µA until a logic level high is
applied to the DC pin.
Start Up
Applying a logic-level HIGH to the DC pin initiates the
start-up sequence. After the t_{START_UP} period the
MIC3289 will transition to State 1, the boost drive will
turn on and begin regulating LED drive current at
maximum brightness level 15, and DC pin programming
pulses will cause the brightness level to decrease.
Figure 2. Start-Up Timing
Shutdown
Whenever a logic-level LOW is applied to the DC input
pin for a period greater than or equal to t_SHUTDOWN, the
MIC3289 will return to State 0 entering its power saving
shutdown mode.
Figure 3. Shutdown Timing
Once the device is shutdown, the boost supply is
disabled, and the LEDs are turned off. Brightness level
information stored in the MIC3289 prior to shutdown will
be lost.
Programming Pulse Counter Modes
Referring once again to the state diagram in Figure 1,
notice that there are two programming pulse counting
modes. At power up the MIC3289 defaults to State 1, the
count-down mode. The counting mode can be changed
to State 2, the count-up mode, by pulling the DC pin low
for a period equal to t_{MODE_UP}. Subsequent programming
pulses will then increase the LED brightness one level
for each pair of programming pulses. Figure 4 shows
the timing for the mode change.
March 2007
9
M9999-030407
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