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MIC2843AYMT View Datasheet(PDF) - Micrel

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MIC2843AYMT Datasheet PDF : 13 Pages
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Micrel Inc.
High Current Parallel Operation
U1 MIC2843AYMT
VIN
C1
RSET
Low
Dropout
Linear
Driver
END
PWM
Control
Figure 11. High Current LED Driver Circuit
The linear drivers are independent of each other and can
be used individually or paralleled in any combination for
higher current applications. A single WLED can be
driven with all 6 linear drivers by connecting D1 through
D6] in parallel to the cathode of the WLED as shown in
Figure 11. This will generate a current 6 times the
individual channel current and can be used for higher
current WLEDs such as those used in flash or torch
applications. The current is set by the RSET resistor, and
can be calculated by the following equation.
ILED (mA) = 6 * 410 * D / RSET (k).
D is the duty cycle of the LED current during PWM
dimming. When the device is fully on the duty cycle
equals 100% (D = 1). Figure 12 shows the response
time of the six paralleled linear drivers configured for
800mA to the enable signal, while Figure 13 shows the
turn off response. With a RSET resistor of 1.65k, each
linear driver is set to 250mA, with all 6 linear drivers
connected in parallel, the MIC2843A is capable of
driving a total current of 1.5A.
MIC2843A
Figure 12. Current Response to a Rising Enable Signal
(Six Paralleled Channels)
Figure 13. Current Response to a Falling Enable Signal
(Six Paralleled Channels)
Input Capacitor
The MIC2843A is a high-performance, high bandwidth
device. Stability can be maintained using a ceramic input
capacitor of 1µF. Low-ESR ceramic capacitors provide
optimal performance at a minimum amount of space.
X5R or X7R dielectrics are recommended for the input
capacitor. Y5V dielectrics lose most of their capacitance
over temperature and are therefore, not recommended.
June 2009
10
M9999-062909-C
 

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