MIC3232 Evaluation Board
High Voltage Boost HBLED Driver with
PWM Dimming Control
Bringing the Power to Light™
General Description
The MIC3232 is a constant current boost switching
controller specifically designed to power one or more
strings of high power LEDs. The MIC3232 has an input
voltage range from 6V to 45V and is ideal for a variety of
applications. The MIC3232 is the fixed 400kHz version of
the MIC3230, in a 10-pin MSOP package.
The MIC3232 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 MIC3232 is
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
1A.
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.
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 MIC3232 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 MIC3232 is off, the input is
connected to the output through the inductor (L1) and
diode (D1). The input voltage (V
IN
) is effectively applied
across the LEDs and will turn on if V
IN
is greater than the
sum of the forward voltage drops across the LED string.
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
to 0.4A. The evaluation board is currently set to this
output current value.
I
LED
=
V
REF
R7
Where V
REF
= 0.25
PWM Dimming
A PWM signal applied to the PWMD pin turns the current
to the LEDs on and off. When PWMD is high, the MIC3232
is enabled and the boost converter regulates the LED
current by keeping the voltage drop across the R7 resistor
constant. When PWMD is low the converter turns off and
the LED current discharges the output capacitors and the
LED current stops.
Ordering Information
Part Number
MIC3232YMM EV
Description
Evaluation board for the MIC3232YML
IC
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
Micrel, Inc.
Quick-Start Guide
1. Connect a load (LED series string or resistive load)
between V
OUT
and LED RTN (this is not the same as
ground).
2. Connect 12V (or other input voltage) to V
IN
and
GND.
3. Use a current probe to measure the load current.
and Monitor the Switch node with a scope to view
the switch waveform
4. PWM Dimming:
a. For no PWM dimming, leave the PWMD
terminal open
b. For PWM DIMMING connect a function
generator to the PWM DIM input and GND
(not RTN). Set the output at 0-5V square
wave pulse at 300Hz. Make sure the pulse
goes all the way to 0V.
MIC3232 Evaluation Board
R
SET
– Current Limit Sensing
The MIC3232 features current limit sensing. Current limit
is set through the external resistor, R6, by the following
equation:
I
S
=0.5V = R6 × I
Q1
Where, I
Q1
is the peak FET current that will trigger the
current limit, the Default setting for the evaluation board
is R6 = 75mΩ with the current limit set at 6.7A.
OVP – Setting the over voltage protection
OVP is set with the R9 resistor, according to equation:
OVP
=
1.245 V
=
(
R9
×
V
O,MAX
)
(
R8
+
R9
)
On the evaluation board, these values have been set to:
R9=2kΩ and R8=100kΩ and V
O,MAX
= 64V.
R4
1/2 W
C3
1000pF
100V
J1
VIN
R1
L1
47µH
C1
4.7uF
50V
1
MIC3232YMM
MSOP-10
VIN
EN
PWMD
OVP
DRV
IS
IADJ
4
7
9
D1
SS5P10-E3
R8
J6
+Vout to LED
J3
EN
J4
PWMD Dim
2
3
Q1
SI7148DP
R5
Vfb=0.25V
R7
1/4W
R6
1/2 W
R9
6
5
C6
2.2uF
100V
C7
2.2uF
100V
R10
OPEN
COMP
VDD
PGND
R3
C4
10nF
J2
GND
C5
10uF
6.3V
10
8
J7
LED RTN
Figure 1. Schematic Diagram
July 2009
2
M9999-071609-A
(408) 944-0800
Micrel, Inc.
MIC3232 Evaluation Board
Bill of Materials
Item
U1
Q1
D1
L1
C1
C5
Part number
MIC3232-YMM
Si7148DP-T1
SS5P10-E3
MSD1278-473ML
GRM32ER71H475KA88L
GRM21BR61A106KE19L
LMK212BJ106KD-T
C0805C106K8PACTU
C3
OR
C6,C7
OR
C4
OR
R1,R8
R3
R4
R9
R5
R6
R7
R10
Notes:
1. DigiKey: www.digikey.com
2. Murata: www.murata.com
3. Vishay: www.vishay.com
4. AVX: www.avx.com
5. TDK: www.tdk.com
6. Diodes, Inc.: www.diodes.com
7. Sumida: www.sumida.com
8. International Rectifier: www.irf.com
9. Micrel, Inc: www.micrel.com
Manufacturer
Micrel.Inc
Vishay Siliconix.
Vishay corp
Coilcraft
Murata
Murata
Taiyo Yuden
Kemet
Vishay Vitramon
Murata
TDK
TDK
Murata
Vishay Vitramon
Murata
Vishay Dale
Vishay Dale
Vishay Dale
Vishay Dale
Vishay Dale
Vishay Dale
Vishay Dale
Part Description
Constant Current Boost control for Hi Power LED
N Channel 75V MOSFET
5A, 100V schottky diode
47µH, rate 5.2A inductor
4.7µF/50V, 1210, Ceramic capacitor
10uF/10V, 0805, ceramic capacitor
Quant
1
1
1
1
1
1
OR
OR
VJ0805Y102KXBAT.
GRM2195C2A102JA01B.
C2012X7R2A102K
C4532X7R2A225K
GRM32ER72A225KA35L.
VJ0603Y103KXBAT.
GRM188R71H103KA01D.
CRCW0603100KFKEA.
CRCW06030000FKEA.
CRCW20102R00FKEF
CRCW06032K00FKEA.
CRCW12064990FKEA.
WSL2010-R0750-FKEA
CRCW1206R620JNTALR.
1nF/100V,0805, Ceramic capacitor
1
2.2µF/100V,1812, Ceramic capacitor
2.2uF/100V, 2220, Ceramic capacitor
10nF/50V, 0603, Ceramic capacitor
100kΩ, 0603, 1%
0Ω, 0603
2Ω, 1/2W, 2010
2kΩ, 0805
499Ω, 1206
0.075Ω, 1/2W, 1812
0.620Ω, 1/4W, 1206
Open
2
1
2
1
1
1
1
1
1
1
July 2009
4
M9999-071609-A
(408) 944-0800
stm32/stm8
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
