Microchip MIC2298-15YML Handleiding

Microchip Niet gecategoriseerd MIC2298-15YML

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MIC2298 Evaluation Board
3.5A I
SWMIN
,1MHz, High Power LED
Driver 3 Preset LED Current Setting
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2008 M9999-062508-B
General Description
This board enables the evaluation of the MIC2298, a fully
integrated 7W net output minimum High Power white LED
driver. The board includes components necessary to set
the LED current to 20%, 50% and 100% of the nominal
LED current (1A). The external inputs also allow the LED
current to be programmed either with additional resistors
or voltages on the DIM or BRT pins. Also the enable pin
can be driven to force the part into low I
Q
mode.
The MIC2298, 1MHz, Integrated Step up current regulator,
allows the use of small and very few external components
to create a compact boosted supply up to 30V. The
evaluation board has been configured with three fixed
current settings chosen using JP1 and all externally
programmable inputs are accessible via board pins.
Requirements
The MIC2298 evaluation board requires an input power
source that is able to deliver at least 5A over the desired
input voltage range. For the load, an electronic load (E-
Load) capable of constant voltage testing is required or a
high power LED mounted on a fan cooled heat sink. Note
that stability measurements must be carried out on an LED
load as E-Loads do not have the same dynamic
characteristics of a high power LED.
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the V
IN
(J1)
terminal may damage the device.
The load current is only regulated if connected between
V
OUT
and FB terminals, the GND terminal close to the V
OUT
terminal is provided for voltage measurements only.
The MIC2298 has a maximum input voltage rating of 10V
therefore, the supply voltage should never exceed this
value.
Getting Started
1. Connect the input supply to the input terminals.
Take note of the polarity to prevent damage. An
ammeter can be used in-line with the VIN terminal
to measure input current. The Input voltage should
be measured at the input terminals to account for
any drops in test leads and amp meter.
2. Ensuring the jumper JP1 is at the top position
(50% load), connect the load to the output
terminals: +VO connects to the positive E-Load
input or Anode of the test LED, FB connects to the
negative E-Load input or the Cathode of the test
LED.
A low impedance ammeter can be connected in-
line with the +VO terminal for current
measurements. The output voltage should be
measured between the evaluation board terminals
+VO and GND (to measure converter efficiency) or
+VO and FB (to measure the voltage of the LED
load).
3. Connect a normally closed (NC) momentary
switch between enable and GND or alternatively,
connect a pulse generator set to output a 2V pulse
of 300ms every 3s to the enable input.
4. Switch on the E-Load (if using), pulse generator
and then the input supply. Measurements can now
be taken of efficiency, switching waveform and
output current regulation. When testing 1A load
(JP1 open), ensure that these are only pulse tests
to prevent damage to the LED. LED manufac-
turers recommend <10% duty cycle and 3s period.
Ordering Information
Part Number Description
MIC2298-15YML EV Evaluation Board with MIC2298-
15YML 15V OVP Device
Micrel, Inc. MIC2298 Evaluation Board
June 2007
2 M9999-062508-B
Evaluation Board
Board Description
By default, the board is set to give 500mA nominal current
into two series connected Power LEDs (JP1 at 50%
position). If the load is not present, the over voltage
protection (OVP) will limit V
OUT
to prevent damage to the
MIC2298. JP1 can be removed to set the load current
higher to 1A (Flash) or moved to 20% to set a lower
200mA current (Torch). Care should be taken as removing
the jumper will result in the maximum LED drive current of
1A.
The external pins can be driven to set any current between
the minimum and maximum values. See Table 1 below.
The nominal current setting can be reduced by choosing a
larger value for R1 (current sense resistor). The 100%
current level can be set by using the following equation:
I
LED100%
= 0.2V/R1
The values in the table will scale with the nominal 100%
current setting. So for example, if the 100% current is set
to 500mA, 0Ω on BRT will set LED current to 100mA,
50kΩ to 250mA etc.
DIM Voltage LED Current
BRT = Open 40mA to 1A
0V to 200mV BRT = GND 0 to 200mA
BRT Voltage LED Current
0V to 1V DIM = 200mV 200mA to 1A
BRT Resistance LED Current
0Ω to 100kΩ DIM = 200mV 200mA to 1A
Table 1. MIC2298 Dimming Methods
Board Performance
High Power White LED Driver
V
IN
= 3.6V; Efficiency ~ 85% at full load (Peak > 87%)
-50
-40
-30
-20
-10
0
10
20
30
40
50
1 10 100 1000
FREQUENCY (kHz)
Bode Plot 4.7µH
(1A LED Load)
-180
-144
-108
-72
-36
36
72
108
144
180
Gain (3V
IN
)
Gain (4.2V
IN
)
Phase (3V
IN
)
Phase (4.2V
IN
)
-50
-40
-30
-20
-10
0
10
20
30
40
50
1 10 100 1000
FREQUENCY (kHz)
Bode Plot 2.2µH
(1A LED Load)
-180
-144
-108
-72
-36
36
72
108
144
180
Gain (3V
IN
)
Gain (4.2V
IN
)
Phase (3V
IN
)
Phase (4.2V
IN
)
Stability 4.7µH Inductor Stability 2.2µH Inductor
Micrel, Inc. MIC2298 Evaluation Board
June 2007
3 M9999-062508-B
0
100
200
300
400
500
600
700
800
900
1000
1100
DIM VOLTAGE (mV)
LED Current
vs. DIM Voltage
0 40 80 120 160 200
0
100
200
300
400
500
600
700
800
900
1000
1100
0 20 40 60 80 100 120 140
LED Current
vs. RBRT
V
IN
= 3.6V
LED Current Programming (VDIM) LED Current Programming (BRT)
Switching Waveforms (BRT – GND) PWM Programming
0
50
100
150
200
250
0 20 40 60 80 100
Duty Cycle (%)
LED Current
vs. DC (on EN Pin)
0
200
400
600
800
1000
1200
0 5 10 15 20 25 30 35
Duty Cycle (%)
LED Current
vs. DC (on BRT Pin)
LED Current Programming
(100Hz PWM on Enable)
LED Current Programming
(1kHz PWM on BRT)

Product specificaties

Merk: Microchip
Categorie: Niet gecategoriseerd
Model: MIC2298-15YML

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