General Description
The MIC2297 is a 600kHz PWM White LED Driver
optimized for 6 to 10 series WLEDs. With an output
voltage of up to 42V and a guaranteed 1.2A on the internal
power switch, the MIC2297 can easily drive 10 WLEDs at
20mA continuous current. The MIC2297 features WLED
brightness control using the BRT pin and has output over
voltage protection (OVP) to protect the device in case the
WLEDs are disconnected unexpectedly. Available in a tiny
10-pin 2.5mm x 2.5mm x 0.85mm MLF
MIC2297 solution only requires a total of 6 external
components.
The MIC2297 operates at a default (BRT pin is open)
feedback voltage of only 200mV. The low feedback
voltage reduces the power dissipation from the external
current
efficiency.
When brightness control is required, the MIC2297 features
brightness control by applying a DC voltage to the BRT
pin. When applying a DC voltage to the BRT pin, the
feedback voltage is equal to the BRT voltage divided by 5.
This feature essentially increases or decreases the
feedback voltage from its default value (200mV), changing
the WLED current to control the WLED brightness.
Alternatively, a PWM signal may also be applied to the
BRT pin for brightness control. When a PWM signal (1kHz
recommended) is applied to the BRT pin, the WLEDs are
dimmed depending on the duty cycle and the peak voltage
of the signal. The PWM frequency can range from 1kHz to
1MHz. The selected PWM frequency does not affect the
WLED brightness. Assuming a 1V PWM signal is applied,
as the duty cycle decreases, the feedback voltage
decreases, thus reducing the WLED current.
Requirements
The MIC2297 evaluation board requires an input power
source that is capable of delivering greater than 1.2A at
2.5V.
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the V
may damage the device.
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
May 2008
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
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The MIC2297 evaluation board is tailored for a single or
dual Li-Ion input source. The input voltage should never
exceed 10V.
Getting Started
Note: For detailed specifications, please refer to the
MIC2297 Datasheet at www.micrel.com.
Ordering Information
408
MIC2297-42YML EV
600kHz 42V OVP PWM White LED Driver
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
1. Connect an external supply to V
2. Enable/Disable the MIC2297. To enable the
3. DCV
4. PWM
Part Number
input voltage to the V
terminals of the evaluation board, paying careful
attention to polarity and supply voltage (2.5V ≤ V
≤ 10V). An ammeter may be placed between the
input supply and the V
evaluation board to accurately monitor the input
current.
resistance can reduce the voltage supplied to the
input; therefore, the supply voltage at the V
terminal should be monitored.
MIC2297, apply a 1.5V or greater voltage signal to
the EN (J2) terminal. To disable the device, pull
the EN (J2) pin below 0.4V. The evaluation board
is configured with a jumper (JP1) from V
enable pin and a 10k pull-down resistor to ground
to conveniently turn the part on or off. Connecting
the jumper (JP1) will enable the MIC2297, while
removing the jumper will disable the part.
brightness with a DC voltage, see the DVC
Brightness Control section.
brightness with a PWM Signal, see the PWM
Brightness Control section.
MIC2297 Evaluation Board
Brightness
Brightness
The
ammeter
Evaluation board with the
Control.
Control.
MIC2297 42V device
IN
IN
Description
(J1) and ground (J4)
and/or
(J1) terminal to the
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