Instrukcja obsługi Microchip MIC3263YML
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MIC3263YML
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MIC3263 Evaluation Board
Six-Channel WLED Driver for
Backlighting Applications with
Flicker-Free Dimming
Bringing the Power to Light™
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
March 2010 M9999-032410-B
General Description
This evaluation board (EVB) is designed for the MIC3263.
The MIC3263 is a high-efficiency Pulse Width Modulation
(PWM) boost switching regulator that is optimized for
constant-current WLED driver backlighting applications.
The MIC3263 drives six channels of up to ten low-power
WLEDs per channel. Each channel is matched in current
to within ±3% for constant brightness across the screen
and can be programmed from 15mA to 30mA.
The MIC3263 provides a very flexible dimming control
scheme with high accuracy and noise immunity. The
dimming frequency can be set to any value between
100Hz and 20kHz by an external resistor. The dimming
ratio is determined by the duty-cycle of a dimming ratio
control input signal and can be set to one of 16 levels with
a minimum ratio of 1%. The LED dimming current is set by
an external resistor to allow programming of LED current
between 15mA and 30mA.
The dimming ratio of the MIC3263 is fixed to 16
logarithmic levels to better match the sensitivity of the
human eye. Each of the dimming levels has hysteresis to
avoid skipping between levels resulting in Flicker-Free
operation.
The MIC3263 has a programmable PWM switching
frequency from 400kHz to 1.8MHz to allow small inductor
sizes. The 6V to 40V wide-input voltage range of MIC3263
allows direct operation from 6V or high cell count Li-Ion
batteries commonly found in notebook computers.
Precautions
The MIC3263 evaluation board operates as a boost
converter, which requires the output voltage to be greater
than the input voltage. Connect a PWM dimming signal to
the DRC pin. The DRC pin needs an input signal to
operate.
Requirements
1. Voltage source capable of supplying 10W
2. Load: Six LED strings
3. Scope
4. Function generator for PWM Dimming
Getting Started
1. Set the LED current of all six channels by one resistor
RISET (noted as R9 on the EVB). Use 2kΩ for 30mA
and 3kΩ for 20mA. Use the following equation to find
RISET:
LED
60
R =
ISET I
Ω
2. Connect six strings of LEDs from LED out to LED-
RTN. Each one of the six LED strings needs to
connect to one of the LED RTN. The cathode end of
each LED string connects to one of the six LED RTN
pins. The anode end of all the LED strings connects to
LED OUT (VOUT). The number of LEDs in each string
should be from 4 to 10.
3. Connect 12V (or other input voltage) to VIN and GND.
4. Use a current probe to measure the load current and
monitor the switch node with a scope to view the
switching waveform
5. PWM Dimming:
a. Connect a function generator to the
dimming input (DRC pin) 0V to 5V at
100Hz to 40kHz.
b. Adjust the duty-cycle of the function
generator for PWM dimming. The
MIC3263 converts the duty-cycle at the
DRC to one of sixteen dimming ratios
(DR) according to Table 1.
c. Follow the power-on sequence to ensure
all channels turn on.
d. The EVB is set for 30mA LED current. For
a different LED current, change R9 using
the given equation.
Specyfikacje produktu
| Marka: | Microchip |
| Kategoria: | nieskategoryzowany |
| Model: | MIC3263YML |
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