MIC3205
High-Brightness LED Driver Controller
with Fixed-Frequency Hysteretic Control
General Description
The MIC3205 is a hysteretic, step-down, high-brightness
LED (HB LED) driver with a patent pending frequency
regulation scheme that maintains a constant operating
frequency over input voltage range. It provides an ideal
solution for interior/exterior lighting, architectural and
ambient lighting, LED bulbs, and other general illumination
applications.
The MIC3205 is well suited for lighting applications
requiring a wide input voltage range. The hysteretic control
provides good supply rejection and fast response during
load transients and PWM dimming. The high-side current
sensing and on-chip current-sense amplifier deliver LED
current with
5%
accuracy. An external high-side current-
sense resistor is used to set the output current.
The MIC3205 offers a dedicated PWM input (DIM) which
enables a wide range of pulsed dimming. A high-frequency
switching operation up to 1.5MHz allows the use of smaller
external components minimizing space and cost.
The MIC3205 operates over a junction temperature from
–40°C to +125°C and is available in a 10-pin 3mm x 3mm
®
MLF package.
Data sheets and support documentation are available on
Micrel’s web site at:
www.micrel.com.
Features
4.5V to 40V input voltage range
Fixed operating frequency over input voltage range
High efficiency (90%)
5%
LED current accuracy
High-side current sense
Dedicated dimming control input
Hysteretic control (no compensation!)
Up to 1.5MHz switching frequency
Adjustable constant LED current
Over-temperature protection
–40C to
125C
junction temperature range
Applications
Architectural, industrial, and ambient lighting
LED bulbs
Indicators and emergency lighting
Street lighting
Channel letters
12V lighting systems (MR-16 bulbs, under-cabinet
lighting, garden/pathway lighting)
_________________________________________________________________________________________________________________________
Typical Application
Normalized Switching Frequency
vs. Input Voltage
2.0
I
LED
= 1A
R
CS
= 0.2Ω
1.5
1 LED
L = 22µH
NORMALIZED FREQUENCY
1.0
0.5
4 LED
L = 47µH
6 LED
L = 68µH
10 LED
L = 33µH
0.0
0
9
18
27
36
45
INPUT VOLTAGE (V)
MIC3205 Buck LED Driver
MLF and
MicroLeadFrame
are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
October 2012
M9999-102312-A
Micrel, Inc.
MIC3205
Ordering Information
Part Number
MIC3205YML
Note:
1.
MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Junction Temperature Range
40°C
to
125°C
Package
(1)
10-Pin 3mm x 3mm MLF
Pin Configuration
10-Pin 3mm x 3mm MLF (ML)
Top View
Pin Description
Pin Number
1
2
3
4
5
6
Pin Name
VCC
CS
VIN
VINS
AGND
EN
Pin Function
Voltage Regulator Output. The VCC pin is the output of a linear regulator powered from VIN, which
supplies power to the internal circuitry. A 4.7µF ceramic capacitor is recommended for bypassing. Place
it as close as possible to the VCC and AGND pins. Do not connect to an external load.
Current Sense Input. Negative input to the current sense comparator. Connect an external sense
resistor to set the LED current. Connect the current sense resistor as close as possible to the chip.
Input Power Supply. VIN is the input supply pin to the internal circuitry. Due to high frequency switching
noise, a 10µF ceramic capacitor is recommended for bypassing and should be placed as close as
possible to the VIN and PGND pins. See “PCB
Layout Guidelines.”
VIN Sense. Positive input to the current sense comparator. Connect as close as possible to the current
sense resistor.
Analog Ground. Ground for all internal low-power circuitry.
Enable Input. Logic high (greater than 2V) powers up the regulator. A logic low (less than 0.4V) powers
down the regulator and reduces the supply current of the device to less than 2µA. A logic low pulls down
the DRV pin turning off the external MOSFET. Do not drive the EN pin above VIN. Do not leave floating.
PWM Dimming Input. A PWM input can be used to control the brightness of the LED. Logic high (greater
than 2V) enables the output. Logic low (less than 0.4V) disables the output regardless of the EN state.
Do not drive the DIM pin above VIN. Do not leave floating.
Timer Capacitor. A capacitor is required from CTIMER to ground sets the target switching frequency
using the equation C
TIMER
=2.22*10
-4
/ F
SW
Power Ground. Ground for the power MOSFET gate driver. The current loop for the power ground
should be as small as possible and separate from the analog ground loop. See “PCB
Layout
Recommendations.”
Gate Drive Output. Connect to the gate of an external N-channel MOSFET. The drain of the external
MOSFET connects directly to the inductor and provides the switching current necessary to operate in
hysteretic mode.
Exposed Pad. Must be connected to a GND plane for best thermal performance.
7
8
9
DIM
CTIMER
PGND
10
EP
DRV
ePAD
October 2012
2
M9999-102312-A
Micrel, Inc.
MIC3205
Absolute Maximum Ratings
(1)
V
IN
to PGND ..................................................
0.3V
to
42V
V
INS
to PGND.........................................
0.3V
to (V
IN
+0.3V)
V
CC
to PGND ................................................
0.3V
to
6.0V
CS to PGND ........................................
0.3V
to (V
IN
0.3V)
EN to AGND ........................................
0.3V
to (V
IN
0.3V)
DIM to AGND ......................................
0.3V
to (V
IN
0.3V)
CTIMER to AGND ..............................
0.3V
to (V
CC
0.3V)
DRV to PGND ....................................
0.3V
to (V
CC
0.3V)
PGND to AGND ..........................................
0.3V
to
0.3V
Junction Temperature ................................................ 150C
Storage Temperature Range ....................
60°C
to
150C
Lead Temperature (Soldering, 10sec) ....................... 260C
ESD Ratings
(3)
HBM ...................................................................... 1.5kV
MM .........................................................................200V
Operating Ratings
(2)
Supply Voltage (V
IN
).......................................... 4.5V to 40V
Enable Voltage (V
EN)
.............................................. 0V to V
IN
Dimming Voltage (V
DIM
)
.................................................................
0V to V
IN
Junction Temperature (T
J
) ........................
40C
to
125C
Junction Thermal Resistance
10-pin 3x3 MLF (
JA
).......................................60.7C/W
10-pin 3x3 MLF (
JC
).......................................28.7C/W
Electrical Characteristics
(4)
V
IN
= V
EN
= V
DIM
= 12V; C
VCC
= 4.7µF; T
J
=
25C;
bold
values indicate
40C
T
J
125C,
unless noted.
Symbol
Input Supply
V
IN
I
S
I
SD
UVLO
UVLO
HYS
VCC Supply
V
CC
Current Sense
∆V
CS
∆t
CS
I
CS
∆V
HYS
Frequency
I
TIMER
V
CTREF
(4*I
TIMER
)/
V
CTREF
CTIMER Pull-up Current
CTIMER Threshold
Frequency Coefficient
(6)
1.776 × 10
-4
66
1.189
2.22 × 10
-4
2.664 × 10
-4
µA
V
A/V
Average Current Sense
Threshold
Current Sense Response
Time
CS Input Current
Sense Voltage Hysteresis
(5)
∆V
CS
=V
INS
V
CS
V
CS
Rising
V
CS
Falling
V
IN
= V
CS
V
IN
=12V, V
LED
=3V,
L=47µH, F
SW
=250kHz,
V
D
= 0.7V, I
LED
= 1A
190
188
200
200
50
70
0.5
46
10
210
212
mV
mV
ns
ns
µA
mV
V
CC
Output Voltage
V
IN
= 12V, I
CC
= 5mA
4.5
5
5.5
V
Input Voltage Range (V
IN
)
Supply Current
Shutdown Current
V
IN
UVLO Threshold
V
IN
UVLO Hysteresis
DRV = Open
V
EN
= 0V
V
IN
Rising
3.2
4
600
4.5
1.3
40
3
2
4.5
V
mA
µA
V
mV
Parameter
Condition
Min.
Typ.
Max.
Units
October 2012
3
M9999-102312-A
Micrel, Inc.
MIC3205
Electrical Characteristics
(4)
(Continued)
V
IN
= V
EN
= V
DIM
= 12V; C
VCC
= 4.7µF; T
J
=
25C;
bold
values indicate
40C
T
J
125C,
unless noted.
Symbol
Enable Input
EN
HI
EN
LO
I
EN
t
START
EN Logic Level High
EN Logic Level Low
EN Bias Current
Start-Up Time
V
EN
= 12V
V
EN
= 0V
From EN pin going high to DRV
going high
2.0
0.4
V
DIM
= 12V
V
DIM
= 0V
From DIM pin going high to DRV
going high
% of switching frequency
Pull-Up, I
SOURCE
= 10mA
Pull-Down, I
SINK
= -10mA
Rise Time, C
LOAD
= 1000pF
Fall Time, C
LOAD
= 1000pF
T
J
Rising
450
2
4
1.5
13
7
160
20
20
50
1
65
20
2.0
0.4
60
1
V
V
µA
µA
µs
Parameter
Condition
Min.
Typ.
Max.
Units
Dimming Input
DIM
HI
DIM
LO
I
DIM
t
DIM
f
DIM
DIM Logic Level High
DIM Logic Level Low
DIM Bias Current
DIM Delay Time
Maximum Dimming Frequency
V
V
µA
µA
ns
%
Ω
Ω
ns
ns
C
C
External FET Driver
R
ON
t
DRV
DRV On-Resistance
DRV Transition Time
Thermal Protection
T
LIM
T
LIMHYS
Notes:
1.
2.
3.
4.
5.
6.
Exceeding the absolute maximum rating can damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.
Specification for packaged product only.
See “Sense
Voltage Hysteresis Range”
in the “Application
Information”
section.
See “Frequency
of Operation”
in the “Application
Information”
section.
Overtemperature Shutdown
Overtemperature Shutdown Hysteresis
October 2012
4
M9999-102312-A
Micrel, Inc.
MIC3205
Typical Characteristics
Efficiency (I
LED
= 1A)
vs. Input Voltage
100
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
9
18
27
36
45
0
9
18
27
36
45
I
LED
= 0A
T
A
= 25°C
V
IN
Supply Current
vs. Input Voltage
1.0
V
IN
Shutdown Current
vs. Input Voltage
V
EN
= 0V
I
LED
= 0A
T
A
= 25°C
V
IN
SHUTDOWN CURRENT (µA)
V
IN
SUPPLY CURRENT (mA)
95
EFFICIENCY (%)
90
85
80
75
70
65
60
1 LED
L = 22µH
4 LED
L = 47µH
6 LED
L = 68µH
10 LED
L = 33µH
0.8
0.6
0.4
0.2
0.0
0
9
18
27
36
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
V
CC
Output Voltage
vs. Input Voltage
6.0
2.0
T
A
= 25°C
I
LED
= 1A
5.5
Normalized Switching Frequency
vs. Input Voltage
1.10
I
LED
= 1A
R
CS
= 0.2Ω
1.5
1 LED
L = 22µH
I
LED
Output Current
vs. Input Voltage
T
A
= 25°C
R
CS
= 0.2Ω
1.05
NORMALIZED FREQUENCY
5.0
1.0
I
LED
OUTPUT CURRENT (A)
V
CC
OUTPUT VOLTAGE (V)
1.00
1 LED
L = 22µH
0.95
4 LED
L = 47µH
0.90
0
9
18
27
36
45
4.5
0.5
4 LED
L = 47µH
6 LED
L = 68µH
10 LED
L = 33µH
6 LED
L = 68µH
4.0
0
9
18
27
36
45
0.0
0
9
18
27
36
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
CTIMER Current
vs. Input Voltage
70
V
EN
= V
IN
T
A
= 25°C
1.5
Enable Threshold
vs. Input Voltage
100
Enable Bias Current
vs. Input Voltage
ENABLE BIAS CURRENT (µA)
V
EN
= V
IN
T
A
= 25°C
I
LED
= 0A
I
LED
= 1A
T
A
= 25°C
CTIMER CURRENT (µA)
68
ENABLE THRESHOLD (V)
1.2
RISING
80
66
0.9
FALLING
60
64
0.6
40
62
0.3
HYST
0.0
20
60
0
9
18
27
36
45
0
0
9
18
27
36
45
0
9
18
27
36
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
October 2012
5
M9999-102312-A
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