MIC2196 LED Driver
Evaluation Board
Boost LED Driver w/PWM DIM Control
General Description
The MIC2196 current mode boost controller is used to
implement a LED Driver with PWM DIM control (Figure 1).
The LED series string is pulsed on and off by the PWM
DIM input signal to provide true PWM dimming. When
pulsed on the LED, current is regulated by the high
frequency current mode boost converter. The converter is
designed as a constant current not a constant voltage
output boost converter. The under voltage lockout is used
to prevent operation below about 9.5V. The input of the
converter is 12V nominal and the output can be from 17V
to 30Vdc. The LED current can be set by selecting the
value of R3 (Table 2). The maximum input voltage to the
MIC2196 is 16V. Table 1 provides a summary of the
specifications. The evaluation board schematic is shown in
Figure 1 and the parts list is shown in the Bill of Materials
table.
Specifications
Max
V
IN
Output voltage
Output current
Power out
efficiency
Output ripple
Switching Freq
PWM control
PWM Frequency
100%
5kHz
300Hz
1Vpp
400kHz
0
0Hz
16Vdc
30Vdc
1amp
30W
Typ
12Vdc
22Vdc
700mA
17W
92%
Min
10Vdc
17Vdc
0
0
a current path through the inductor and through the fly
back 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
Switch Q3, turns off and on the current to the load. When
the load current is turned on the boost converter regulates
the load current by keeping the IR drop across
R10+Q3_R
DSON
constant. Q3’s R
DSON
is a low (about 1/10
of R10) compared to R10. When the load is off the
converter turns off (FB pin is pulled high by R14). When
the load current is turned off the input is connected to the
output through L1 and D1. For 100% duty cycle, simply
keep PWM DIM high (5V). For a different LED current
change R3 using the following equation. When R3 is 2.15K
the LED current is at 1A.
V
FB
=
V
REF
=
Where:
V
REF
= 1.245
V
Z
= 7.5V
R3 = 2.43k. (used on evaluation board)
R14 = 15k
R10 = 330mΩ
Q3
RDSON
= 34mΩ
R3
2.15k
2.21k
2.26k
2.32k
2.37k
2.43k
2.49k
2.55k
2.61k
I_LED Measured
1.02amps
920mA
860mA
792mA
744mA
700mA
616mA
536mA
490mA
Table 2. R3 Values
I_LED Calculated
1A
930mA
870mA
810mA
760mA
700mA
640mA
580mA
520mA
R3
V
Z
+
I
LED
×
(R10
+
Q3
RDSON
)
R3
+
R14
(Approximate)
Table 1. Design Specifications
Requirements
1. Voltage source at 3A
2. Pulse generator: TTL output, 100-300 HZ variable duty
cycle
3. Load: LED string (series), a resistive or a electronic
load (constant resistance mode)
Precautions
The evaluation board does not have input reverse polarity
protection. Applying a negative voltage at the V
IN
terminal
may damage the board. When the controller is off there is
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
January 2007
1
M9999-013107-A
Micrel, Inc.
MIC2196 LED Driver Evaluation Board
I_LED vs. R3
1050
1000
950
900
850
800
mA
750
700
650
600
550
500
2.15 2.21 2.26 2.32 2.37 2.43 2.49 2.55 2.61
R3(kohm)
Quick-Start Guide
1. Connect a load between V
OUT
and RTN. (LED series
string or resistive load)
2. 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.
3. Connect 12V to V
IN
and GND.
4. Use a current probe to measure the load current.
Plot 1. I_LED vs R3
January 2007
2
M9999-013107-A
Micrel, Inc.
MIC2196 LED Driver Evaluation Board
Figure 1. Schematic Diagram
Bill of Materials
Item
Z1
Part Number
TZMC33
TZS4714
FLZ33VCC
Q1
Q2
Q3
D1
L1
C1
C2
C4
C5
C6
C3, C7,
C9
C8
LED
R1, R17
R2
BC846A
BC846AMTF
SI4484EY
SI4850EY
SI3434DV
SI3424DV
PDS540
SSC54
CDR7D43MN-4R7NC.
594D476X9035D2T
GRM32DF51H106ZA01
C3216X7R1H106M.
594D106X9035D2T
594D156X9035D2T
VJ0805Y102KXAMT
VJ0603Y102KXAMT
GRM21BR71C105KA01B
VJ0805S105KXJAT
VJ0603Y101KXAMT
LEW E3A
CRCW06031002FRT1
CRCW08051501FRT1
Manufacturer
Vishay
(1)
Vishay
(1)
Faichild Semiconductor
Diodes, Inc.
(3)
Vishay Siliconix
(1)
Vishay Siliconix
(1)
Diodes, Inc.
(1)
Vishay
(1)
(2)
Description
33V, 500mW, SOD-80, Zener diodes
Qty.
1
65v/100mA, NPN Silicon transistor
MOSFET
N-MOSFET, 30V, 330 mil-Ohms
Schottky Diodes, 40V, 5A
4.7µH, 6A inductor
47µF/35V, D case
10µF/50V, 1210
10µF/35V, D case
15µF/35V, D case
1000pF, 50V, X7R ceramic cap
1000pF, 50V, X7R ceramic cap
1µF/25V, ceramic cap
100pF, 50V, X7R ceramic cap
OPEN
10K, 0603, 1%
1.5K, 0805, 1%
1
1
1
1
1
1
1
1
1
1
3
1
0
2
1
Sumida
(4)
Vishay Sprague
(1)
MuRata
(5)
TDK
(6)
Vishay Sprague
(1)
Vishay Sprague
(1)
Vishay Vitramon
(1)
Vishay Vitramon
(1)
MuRata
(5)
Vishay Victramon
(1)
Vishay Vitramon
(1)
OSRAM
(7)
Vishay Dale
(1)
Vishay Dale
(1)
January 2007
3
M9999-013107-A
Micrel, Inc.
Item
R3
R4
R6
R7
R8
R9
R10
R11
R14
R15
R16
Z2
IC1
Notes:
1. Vishay: www.vishay.com
2. Fairchild Semiconductor: www.fairchildsemi.com
3. Diodes, Inc.: www.diodes.com
4. Sumida: www.sumida.com
5. Murata:: www.murata.com
6. TDK: www.tdk.com
7. Osram: osram.com
8.
Micrel, Inc.: www.micrel.com
MIC2196 LED Driver Evaluation Board
Part Number
CRCW06032431FRT1
CRCW06031000FRT1
CRCW06031821FRT1
CRCW06032200FRT1
WSL1210-R010-F
WSL2010-R010-F
CRCW08055R11FRT1
WSL1210-R330-F
WSL2010-R330-F
CRCW08052742FRT1
CRCW06031502FRT1
CRCW06031003FRT1
CRCW06031961FRT1
LM4041CYM3-ADJ
MIC2196YM
Manufacturer
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Description
2.43K, 0603, 1%.
100 Ohm , 0603, 1%
1.82K, 0603, 1%
220Ω, 0603, 1%.
10mΩ, 1210
5.11Ω, 0805, 1%.
330mΩ, 1210, 1%.
27.4K, 0805, 1%
15K, 0603, 1%
100K, 0603, 1%
1.96K, 0603, 1%
Precision shunt Voltage references
Boost controller
Qty.
1
1
1
1
1
1
1
1
1
1
1
1
1
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Vishay Dale
(1)
Micrel, Inc.
(8)
Micrel, Inc.
(8)
January 2007
4
M9999-013107-A
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