Instrukcja obsługi Microchip MIC3231TE-Sepic
Microchip
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MIC3231TE-Sepic
Przeczytaj poniżej 📖 instrukcję obsługi w języku polskim dla Microchip MIC3231TE-Sepic (7 stron) w kategorii nieskategoryzowany. Ta instrukcja była pomocna dla 11 osób i została oceniona przez 6 użytkowników na średnio 4.8 gwiazdek
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Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2009 M9999-071609-A
(408) 944-0800
General Description
The MIC3230/1 are constant current boost switching
controllers specifically designed to power one or more
strings of high power LEDs. The MIC3230/1 have an input
voltage range from 6V to 45V and are ideal for a variety of
applications.
The MIC3230/1 utilizes an external power device which
offers a cost conscious solution for driving high power LED
applications. Power consumption has been minimized
through the implementation of a 250mV feedback voltage
reference providing an accuracy of ±3%. The MIC3230/1
are dimmable via a PWM input signal and also features an
enable pin for low power shutdown.
The LED current is regulated by keeping the voltage drop
across the current sense resistor (R7) constant. The LED
current can be set by selecting the value of R7. In this
version of the eval board, the output current is limited to
750mA.
Multiple MIC3230 ICs can be synchronized to a common
operating frequency by connecting the ICs together
through the SYNC pin. This feature is only good on the
MIC3230. The clocks of these synchronized devices can
be used together which help reduce noise and errors in a
system.
The MIC3231 offers a dither feature to assist in the
reduction of EMI. This is particularly useful in sensitive
EMI applications, and provides for a reduction in emissions
by approximately 10dB.
Table 1 provides a summary of the eval board
specifications. The evaluation board schematic is shown in
Figure 1 and the parts list is shown in the Bill of Materials
table.
The switching frequency is determined by the selection of
R1. The chart in Figure 2 can be used to select the
desired frequency. The board is set at approximately
500kHz.
Requirements
1. Voltage source capable of supplying 50 Watts
2. Load: LED, resistive or electronic load
3. Scope
4. Voltage meter
5. (Optional) Function generator for PWM Dimming
Precautions
The evaluation board does not have input reverse polarity
protection. Applying a negative voltage at the VIN terminal
may damage the board. When the controller is off there is
a current path through the inductor and the flyback diode
to the output. No current limit exists for this current path so
care must be taken not to short circuit the output.
How it works
The MIC3230/1 evaluation board is set to operate as a
boost converter, which requires the output voltage to be
greater than the input voltage. It is important to have the
series LED forward voltage drops be greater than the input
voltage because when the converter is off the input is
connected to the output through the inductor (L1) and
diode (D1). VIN is effectively applied across the LEDs and
will turn on if the series sum of their forward voltage drop is
not greater than VIN. For 100% duty cycle, simply pull
PWMD high or leave open. For a different LED current
change R7 using the following equation. When R7 is
0.62Ω, the LED current is equal to 0.4A. The evaluation
board is currently set to this output current value.
7R
V
IREF
LED = Where VREF = 0.25V
PWM Dimming
A PWM signal applied to the PWMD pin turns the current
to the load LEDs on and off. When PWMD is high the
MIC3230/1 is enabled and the boost converter regulates
the LED current by keeping the voltage drop across R7
constant. When PWMD is low the converter turns off and
the LED current discharges the output caps and LED
current stops.
Ordering Information
Part Number Description
MIC3230ML
BOOST EV
Boost evaluation board for the
MIC3230YML IC
MIC3231ML
BOOST EV
Boost evaluation board for the
MIC3231YML IC
Specyfikacje produktu
| Marka: | Microchip |
| Kategoria: | nieskategoryzowany |
| Model: | MIC3231TE-Sepic |
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