MIC2297-42YML EV Micrel, MIC2297-42YML EV Datasheet - Page 2

• Manufacturer Part Number: MIC2297-42YML EV
• Description: Power Management IC Development Tools 1.2MHz 1.2A PWM Boost Converter - Evaluation Board
• Manufacturer: Micrel
• Type: PWM Controllersr

Specifications of MIC2297-42YML EV

• Product: Evaluation Boards
• Tool Is For Evaluation Of: MIC2297
• Input Voltage: 2.5 V to 10 V
• Output Voltage: 42 V
• Description/function: Evaluation Board
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Output Current: 1.2 A
• For Use With: MIC2297

LED Current Setting
There are 10 WLEDs provided with the evaluation board.
Two of the WLEDs (D1 and D2) may be by-passed by
placing a jumper on JP3. The WLED current (I
to the feedback voltage (V
by the R3 resistance value. The evaluation board is
provided with R3 equal to 10Ω. The brightness level is
proportional to I
changes the I
DCV Brightness Control
The brightness level can be set by applying a DC voltage
(BRT) to the BRT pin. When a DC voltage is applied to the
BRT pin, the feedback voltage is changed from the default
value of 200mV to:
Assuming BRT equals 1V, then V
ILED may be calculated by:
Similarly, if BRT equals 2V, then V
the I
The feedback voltage can be changed using the BRT pin.
Changing the feedback voltage changes the WLED
current, which will change the WLED brightness. Refer to
the Figure 1 and Figure 2 for reference.
Micrel, Inc.
May 2008
LED
Figure 1. BRT = 1V, V
may be calculated by:
I
V
I
I
I
I
I
I
LED
LED
LED
LED
LED
LED
LED
FB
= BRT / 5
= V
= V
= 200mV / 10Ω
= 20mA
= V
= 400mV / 10Ω
= 40mA
LED
FB
FB
FB
, therefore changing the brightness level.
LED
/ R3
/ R3
/ R3
. Programming the feedback voltage
FB
TIME (400µs/div)
FB
= 200mV by default) divided
= 200mV, I
FB
FB
will be 200mV and
will be 400mV and
LED
= 20mA
LED
(1)
(2)
) is equal
2
PWM Brightness Control
The brightness level can also be set by applying a PWM
signal to the BRT pin. To calculate the feedback voltage
when a PWM signal is applied to the BRT pin, use the
following formula:
V
cycle. If V
be calculated by:
The I
Similarly, if the V
V
The I
With PWM brightness control, the MIC2297 has great
versatility since brightness may be set anywhere from 0 to
100 percent. Refer to the following figures for reference.
PEAK
FB
can be calculated by:
LED
LED
is the peak of the PWM voltage and D is the duty
Figure 2. BRT = 2V, V
V
V
V
I
I
I
V
V
I
I
I
can then be calculated by:
can then be calculated by:
LED
LED
LED
LED
LED
LED
FB
FB
FB
FB
FB
PEAK
= V
= 1V / 5 * 0.01
= 2mV
= 1V / 5 * 0.5
= 100mV
= V
= 2mV / 10Ω
= 200µA
= V
= 100mV / 10Ω
= 10mA
is 1V and the duty cycle is 1%, then V
PEAK
FB
FB
PEAK
/ R3
/ R3
/ 5 * D
is 1V and the duty cycle is 50%, then
TIME (400µs/div)
FB
MIC2297 Evaluation Board
= 400mV, I
LED
M9999-053008-A
= 40mA
(3)
FB
can