MIC3203-1YM [MICREL]
High-Brightness LED Driver Controller with High-Side Current Sense; 高亮度LED驱动器控制器，具有高边电流检测
| 型号： | MIC3203-1YM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | High-Brightness LED Driver Controller with High-Side Current Sense |
| 文件： | 总21页 (文件大小：725K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC3203/MIC3203-1
High-Brightness LED Driver Controller
with High-Side Current Sense
General Description
Features
The MIC3203 is a hysteretic, step-down, constant-current,
High-Brightness LED (HB LED) driver. It provides an ideal
solution for interior/exterior lighting, architectural and
ambient lighting, LED bulbs, and other general illumination
applications.
• 4.5V to 42V input voltage range
• High efficiency (>90%)
• ±5% LED current accuracy
• MIC3203: Dither enabled for low EMI
• MIC3203-1: Dither disabled
• 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
The MIC3203 is well suited for lighting applications
requiring a wide-input voltage range. The hysteretic control
gives good supply rejection and fast response during load
transients and PWM dimming. The high-side current
sensing and on-chip current-sense amplifier delivers LED
current with ±5% accuracy. An external high-side current-
sense resistor is used to set the output current.
The MIC3203 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
MIC3203 offers frequency dither feature for EMI control.
• −40°C to +125°C junction temperature range
Applications
• Architectural, industrial, and ambient lighting
• LED bulbs
• Indicators and emergency lighting
• Street lighting
The MIC3203 operates over a junction temperature from
−40°C to +125°C and is available in an 8-pin SOIC
package.
A dither disabled version MIC3203-1 is also available in
the same package as the MIC3203.
• Channel letters
• 12V lighting systems (MR-16 bulbs, under-cabinet
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
lighting, garden/pathway lighting)
_________________________________________________________________________________________________________________________
Typical Application
MIC3203 Step-down LED Driver
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
M9999-032910-A
March 2010
Micrel, Inc.
MIC3203
Ordering Information (1)
Part Number
MIC3203YM
MIC3203-1YM
Note:
Marking
Junction Temperature Range
−40°C to +125°C
Package
8-Pin SOIC
8-Pin SOIC
PWM
Dither
MIC3203YM
MIC3203-1YM
Non-Dither
−40°C to +125°C
1. YM® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
8-Pin SOIC
MIC3203/MIC3203-1
Pin Description
Pin Number Pin Name Pin Function
Voltage Regulator Output. The VCC pin supplies the power to the internal circuitry. The VCC in the output
of a linear regulator which is powered from VIN. A 1µF ceramic capacitor is recommended for bypassing
and should be placed as close as possible to the VCC and AGND pins. Do not connect to an external
load.
1
2
VCC
CS
Current-Sense Input. The CS pin provides the high-side current sense to set the LED current with an
external sense resistor.
Input Power Supply. VIN is the input supply pin to the internal circuitry and the positive input to the
current sense comparator. Due to the high frequency switching noise, a 10µF ceramic capacitor is
recommended to be placed as close as possible to VIN and the power ground (PGND) pin for
bypassing. Please refer to layout recommendations.
3
4
VIN
AGND
Ground pin for analog circuitry. Internal signal ground for all low power sections.
Enable Input. The EN pin provides a logic level control of the output and the voltage has to be 2.0V or
higher to enable the current regulator. The output stage is gated by the DIM pin. When the EN pin is
pulled low, the regulator goes to off state and the supply current of the device is greatly reduced (below
1µA). In the off state, during this period the output drive is placed in a "tri-stated" condition, where
MOSFET is in an “off” or non-conducting state. Do not drive the EN pin above the supply voltage.
5
EN
PWM Dimming Input. The DIM pin provides the control for brightness of the LED. A PWM input can be
used to control the brightness of LED. DIM high enables the output and its voltage has to be at least
2.0V or higher. DIM low disables the output, regardless of EN “high” state.
6
7
DIM
Power Ground Pin for Power FET. Power Ground (PGND) is for the high-current switching with
hysteretic mode. The current loop for the power ground should be as small as possible and separate
from the Analog ground (AGND) loop. Refer to the layout considerations for more details.
PGND
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. Due to the high frequency switching and high voltage associated with this pin, the
switch node should be routed away from sensitive nodes.
8
DRV
M9999-032910-A
March 2010
2
Micrel, Inc.
MIC3203
Absolute Maximum Ratings (1)
Operating Ratings (2)
Supply Voltage (VIN).......................................... 4.5V to 42V
Enable Voltage (VEN) .............................................. 0V to VIN
VIN to PGND .................................................. −0.3V to +45V
VCC to PGND ................................................ −0.3V to +6.0V
Dimming Voltage (VDIM .................................................................0V to VIN
)
CS to PGND........................................ −0.3V to (VIN + 0.3V)
EN to AGND........................................ −0.3V to (VIN + 0.3V)
DIM to AGND ...................................... −0.3V to (VIN + 0.3V)
DRV to PGND ....................................−0.3V to (VCC + 0.3V)
PGND to AGND .......................................... −0.3V to + 0.3V
Junction Temperature ................................................ 150°C
Storage Temperature Range ....................−60°C to +150°C
Lead Temperature (Soldering, 10sec) ....................... 260°C
ESD Ratings (3)
Junction Temperature (TJ) ........................ −40°C to +125°C
Junction Thermal Resistance
SOIC (θJA).......................................................98.9°C/W
SOIC (θJC).......................................................48.8°C/W
HBM......................................................................1.5kV
MM.........................................................................200V
Electrical Characteristics (4)
VIN = VEN = VDIM = 12V; CVCC = 1.0µF; TJ = 25°C, bold values indicate −40°C ≤ TJ ≤ +125°C; unless noted.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
Input Supply
VIN
Input Voltage Range (VIN)
4.5
42
3
V
IS
Supply Current
DRV = open
VEN = 0V
1
mA
µA
V
ISD
Shutdown Current
VIN UVLO Threshold
1
UVLO
VIN rinsing
3.2
4.5
4
4.5
UVLOHYS VIN UVLO Hysteresis
500
mV
VCC Supply
VCC
VCC Output Voltage
VIN = 12V, ICC = 10mA
5
5.5
V
Current Limit
201.4
199
212
212
177
177
35
222.6
225
mV
mV
mV
mV
mV
ns
VCS(MAX)
Current Sense Upper Threshold
VCS(MAX ) = VIN − VCS
VCS(MIN ) = VIN − VCS
168
186
VCS(MIN)
VCSHYS
Sense Voltage Threshold Low
VCS Hysteresis
165
189
VCS Rising
50
Current Sense Response Time
CS Input Current
VCS Falling
70
ns
0.5
10
µA
VIN − VCS = 220mV
Frequency
FMAX
Switching Frequency
1.5
MHz
Dithering (MIC3203)
VDITH
VCS Hysteresis Dithering Range(5)
Frequency Dithering Range(5)
±6
mV
%
FDITHER
% of Switching Frequency
±12
M9999-032910-A
March 2010
3
Micrel, Inc.
MIC3203
Electrical Characteristics (4) (Continued)
VIN = VEN = VDIM = 12V; CVCC = 1.0µF; TJ = 25°C, bold values indicate −40°C ≤ TJ ≤ +125°C; unless noted.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
Enable Input
ENHI
EN Logic Level High
2.0
V
V
ENLO
EN Logic Level Low
0.4
60
1
VEN = 12V
VEN = 0V
µA
µA
EN Bias Current
From EN Pin going high to DRV
going high
Start-Up Time
30
µs
Dimming Input
DIMHI
DIMLO
DIM Logic Level High
2.0
V
V
DIM Logic Level Low
0.4
50
1
20
DIM Bias Current
µA
VDIM = 0V
From DIM Pin going high to DRV
going high
DIM Delay Time
450
ns
FDIM
Maximum Dimming Frequency
20
kHz
External FET Driver
Pull Up, ISOURCE = 10mA
Pull Down, ISINK = -10mA
Rise Time, CLOAD = 1000pF
Fall Time, CLOAD = 1000pF
2
1.5
13
7
DRV On-Resistance
Ω
DRV Transition Time
Thermal Protection
ns
TLIM
Over-Temperature Shutdown
TJ Rising
160
20
°C
TLIMHYS
Notes:
Over-Temperature Shutdown Hysteresis
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. Specification for packaged product only.
5. Guaranteed by design.
M9999-032910-A
March 2010
4
Micrel, Inc.
MIC3203
Typical Characteristics
Normalized LED Currents
vs. Input Voltage
Efficiency
vs. Input Voltage
Efficiency
vs Input Voltage
1.03
1.02
1.01
1
100
90
100
90
L=150µH
ILED=1A
10LED
8LED
6LED
2LED 4LED
1LED
80
80
4LED
6LED
4LED
6LED
0.99
0.98
0.97
8LED
8LED
10LED
70
70
10LED
L=68µH
ILED=1A
L=150µH
ILED=1A
60
0
5
10
15
20
25
30
35
40
45
60
0
5
10 15 20 25 30 35 40 45
INPUT VOLTAGE (V)
0
5
10
15
20
25
30
35
40
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Frequency
vs. Input Voltage
Normalized LED Currents
vs Input Voltage
Frequency
vs Input Voltage
350
300
250
200
150
100
50
700
600
500
400
300
200
100
0
1.03
1.02
1.01
1
L=150µH
ILED=1A
L = 68µH
ILED = 1A
L=68µH
ILED=1A
4LED
4LED
2LED
1LED
2LED
0.99
0.98
0.97
1LED
2LED
1LED
4LED
6LED
25
8LED
10LED
40
10LED
8LED
6LED
6LED
8LED
30
10LED
0
0
5
10
15
20
30
35
45
0
5
10
15
20
25
35
40
45
0
5
10
15
20
25
30
35
40
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Duty Cycle
Duty Cycle
vs. Input Voltage
vs Input Voltage
Supply Current
vs. Input Voltage
100
75
50
25
0
100
75
50
25
0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
TA = 25°C
ILED = 0A
1LED
1LED
2LED
4LED
2LED
4LED
6LED
6LED
8LED
5
L=68µH
ILED=1A
L=150µH
ILED=1A
8LED
5
0
5
10 15 20 25 30 35 40 45
10LED
40
10LED
40
INPUT VOLTAGE (V)
0
10
15
20
25
30
35
45
0
10
15
20
25
30
35
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
M9999-032910-A
March 2010
5
Micrel, Inc.
MIC3203
Typical Characteristics (Continued)
VCC vs. Input Voltage
Enable Threshold
vs. Input Voltage
Current-Sense Voltage
vs. Input Voltage
250
200
150
100
50
6.0
5.0
4.0
3.0
2.0
1.0
0.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
TA = 25°C
ILED = 0A
ICC = 0A
TA = 25°C
ILED = 0A
ICC = 0A
VCS_MIN
VCS_MAX
L = 100µH
ILED = 1A
0
0
5
10 15 20 25 30 35 40 45
0
5
10 15 20 25 30 35 40 45
0
5
10 15 20 25 30 35 40 45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Shutdown Current
vs. Input Voltage
ICC Limit
vs. Input Voltage
Enable Current
vs. Enable Voltage
40
35
30
25
20
15
10
5
160
140
120
100
80
200
180
160
140
120
100
80
TA = 25°C
ILED = 0A
60
TA = 25°C
60
40
TA = 25°C
VCC = 4.2V
ILED = 0A
40
20
0
20
0
-5
0
0
5
10 15 20 25 30 35 40 45
0
5
10 15 20 25 30 35 40 45
0
5
10 15 20 25 30 35 40 45
ENABLE VOTLAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Supply Current
vs. Temperature
VCC
vs. Temperature
Enable Threshold
vs. Temperature
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ON
VIN = 12V
ICC = 0A
OFF
VIN = 12V
ILED = 0A
-40 -20
0
20
40
60
80 100 120
-40 -20
0
20
40
60
80 100 120
-40 -20
0
20
40
60
80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
M9999-032910-A
March 2010
6
Micrel, Inc.
MIC3203
Typical Characteristics (Continued)
Shutdown Current
vs. Temperature
Enable Current
vs. Temperature
Current-Sense Voltage
vs. Temperature
250
200
150
100
50
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
50
45
40
35
30
25
20
15
10
5
VCS_MAX
VCS_MIN
VIN = 12V
EN = VIN
VIN = 12V
EN = 0V
∆_VCS
ILED
ILED = 1A
0
0
-40 -20
0
20
40
60
80 100 120
-40 -20
0
20
40
60
80 100 120
-40 -20
0
20
40
60
80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
Switching Frequency
vs. Temperature
UVLO Threshold
vs. Temperature
Thermal Shutdown
vs. Input Voltage
OFF
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
180
160
140
120
100
80
160
140
120
100
80
ON
ON
OFF
60
60
VIN = 12V
1ILED
ILED = 1A
L = 100µH
40
40
20
20
0
0
-40 -20
0
20
40
60
80 100 120
-40 -20
0
20
40
60
80 100 120
0
5
10 15 20 25 30 35 40 45
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
M9999-032910-A
March 2010
7
Micrel, Inc.
MIC3203
Functional Characteristics
M9999-032410-A
March 2010
8
Micrel, Inc.
MIC3203
Functional Characteristics (Continued)
M9999-032410-A
March 2010
9
Micrel, Inc.
MIC3203
Functional Diagram
Figure 1. MIC3203/MIC3203-1 Block Diagram
Functional Description
The MIC3203 is a hysteretic step-down driver which
regulates the LED current over wide input voltage range.
The frequency of operation depends upon input voltage, total
LEDs voltage drop, LED current and temperature. The
calculation for frequency of operation is given in application
section.
The device operates from a 4.5V to 42V input MOSFET
voltage range and provides up to 0.5A source and 1A
sink drive capability. When the input voltage reaches
4.5V, the internal 5V VCC is regulated and the DRV pin
is pulled high to turn on an external MOSFET if EN pin
and DIM pin are high. The inductor current builds up
linearly. When the CS pin voltage hits the VCS(MAX) with
respect to VIN, the MOSFET turns off and the Schottky
diode takes over and returns the current to VIN. Then the
current through inductor and LEDs starts decreasing.
When CS pin hits VCS(MIN), the MOSFET turns on and the
cycle repeats.
The MIC3203 has an on board 5V regulator which is for
internal use only. Connect a 1µF capacitor on VCC pin to
analog ground.
The MIC3203 has an EN pin which gives the flexibility to
enable and disable the output with logic high and low
signals.
The MIC3203 also has a DIM pin which can turn on and off
the LEDs if EN is in HIGH state. This DIM pin controls the
brightness of the LED by varying the duty cycle of DIM pin
from 1% to 99%.
M9999-032910-A
March 2010
10
Micrel, Inc.
MIC3203
Application Information
Frequency of Operation
The internal block diagram of the MIC3203 is shown in
Figure 1. The MIC3203 is composed of a current-sense
comparator, voltage and current reference, 5V regulator
and MOSFET driver. Hysteretic mode control – also
called bang-bang control – is a topology that does not
employ an error amplifier, using an error comparator
instead.
To calculate the frequency spread across input supply:
ΔIL
VL = L
Δt
L is the inductance, ∆IL is fixed (the value of the hysteresis):
The inductor current is controlled within a hysteretic
window. If the inductor current is too small, the power
MOSFET is turned on; if the inductor current is large
enough, the power MOSFET is turned off. It is a simple
control scheme with no oscillator and no loop
compensation. Since the control scheme does not need
loop compensation, it makes a design easy, and avoids
problems of instability.
VCS(MAX) - VCS(MIN)
ΔIL =
RCS
VL is the voltage across inductor L which varies by supply.
For current rising (MOSFET is ON):
Transient response to load and line variation is very fast
and only depends on propagation delay. This makes the
control scheme very popular for certain applications.
ΔIL
tr =L
VL _RISE
LED Current and RCS
The main feature in MIC3203 is to control the LED
current accurately within ±5% of set current. Choosing a
high-side RCS resistor helps for setting constant LED
current irrespective of wide input voltage range. The
following equation gives the RCS value:
where:
VL_RISE = VIN − ILED × RCS − VLED
For current falling (MOSFET is OFF):
VCS(MAX) + VCS(MIN)
1
2
ΔIL
tf = L
RCS
=
x(
)
ILED
VL _FALL
where:
Table 1. RCS for LED Current
V
L_FALL = VD + ILED × RCS + VLED
R
CS (Ω)
ILED (A)
0.15
0.35
0.5
I2R (W)
0.03
0.07
0.1
Size (SMD)
0603
1
1.33
0.56
0.4
T = tr + tf , FSW
=
T
0805
(V +ILED×RCS+VLED)×(V -ILED×RCS-V
)
D
IN
LED
0805
F
=
SW
L×ΔIL ×(V +V )
D
IN
0.28
0.2
0.7
0.137
0.2
0805
1.0
1206
where :
0.13
0.1
1.5
0.3
1206
•
•
•
•
VD is Schottky diode forward drop
VLED is total LEDs voltage drop
VIN is input voltage
2.0
0.4
2010
0.08
2.5
0.5
2010
0.068
3.0
0.6
2010
ILED is average LED current
For VCS(MAX) and VCS(MIN), refer to the Electrical
Characteristic table.
M9999-032910-A
March 2010
11
Micrel, Inc.
MIC3203
Given an inductor value, the size of the inductor can be
determined by its RMS and peak current rating.
Inductor
According to the above equation, choose the inductor to
make the operating frequency no higher than 1.5MHz.
The following Tables give a reference inductor value and
corresponding frequency for a given LED current. For
space-sensitive applications, smaller inductor with higher
switching frequency could be used but efficiency of the
regular will be reduced.
V
CS(MAX) - VCS(MIN)
ΔIL
= 2×
= 0.18
IL
VCS(MAX) + VCS(MIN)
1
IL(RMS) = IL2 +
ΔIL2 ≈ IL
12
Table 2. Inductor for VIN = 12V, 1 LED
1
IL(PK) =IL + ΔIL =1.09IL
RCS (Ω)
1.33
0.56
0.4
ILED (A)
0.15
0.35
0.5
L (µH)
220
100
68
FSW (kHz)
2
474
439
where:
IL is inductor average current.
461
0.28
0.2
0.7
47
467
1.0
33
475
Select an inductor with saturation current rating at least 30%
higher than the peak current.
0.13
0.1
1.5
22
463
2.0
15
522
MOSFET
0.08
0.068
2.5
12
522
MOSFET selection depends upon the maximum input
voltage, output LED current and switching frequency.
3.0
10
533
The selected MOSFET should have 30% margin on
maximum voltage rating for high reliability requirements.
Table 3. Inductor for VIN = 24V, 4 LEDs
The MOSFET channel resistance RDSON is selected such
that it helps to get the required efficiency at the required LED
currents as well as meets the cost requirement.
RCS (Ω)
1.33
0.56
0.4
ILED (A)
0.15
0.35
0.5
L (µH)
470
220
150
100
68
FSW (kHz)
474
426
Logic level MOSFETs are preferred as the drive voltage is
limited to 5V.
447
0.28
0.2
0.7
470
The MOSFET power loss has to be calculated for proper
operation. The power loss consists of conduction loss and
switching loss. The conduction loss can be found by:
1.0
493
0.13
0.1
1.5
47
463
2.0
33
507
LOSS(CON) =IR2MS(FET) ×RDSON
0.08
0.068
2.5
27
496
P
3.0
22
517
IRMS(FET) =ILED × D
VTOTAL _LED
D =
Table 4. Inductor for VIN = 36V, 8 LEDs
V
IN
RCS (Ω)
1.33
0.56
0.4
ILED (A)
0.15
0.35
0.5
L (µH)
470
220
150
100
68
FSW (kHz)
495
446
467
0.28
0.2
0.7
490
1.0
515
0.13
0.1
1.5
47
485
2.0
33
530
0.08
0.068
2.5
27
519
3.0
22
541
M9999-032910-A
March 2010
12
Micrel, Inc.
MIC3203
The switching loss occurs during the MOSFET turn-on
and turn-off transition and can be found by:
The input capacitor current rating can be considered as
ILED/2 under the worst condition D = 50%.
LED Ripple Current
V ×ILED ×FSW
IN
The LED current is the same as inductor current. If LED ripple
current needs to be reduced then place a 4.7µF/50V ceramic
capacitor across LED.
P
=
×(Qgs2 + Qgd)
LOSS(TRAN)
IDRV
VDRV
IDRV
=
RGATE
Frequency Dithering
The MIC3203 is designed to reduce EMI by dithering the
switching frequency ±12% in order to spread the frequency
spectrum over a wider range. This lowers the EMI noise
peaks generated by the switching regulator.
where:
RGATE is total MOSFET resistance, Qgs2 and Qgd can be
found in a MOSFET manufacturer datasheet.
Switching regulators generate noise by their nature and they
are the main EMI source to interference with nearby circuits. If
the switching frequency of a regulator is modulated via
frequency dithering, the energy of the EMI is spread among
many frequencies instead of concentrated at fundamental
switching frequency and its harmonics. The MIC3203
modulates the VCS(MAX) with amplitude ±6mV by a pseudo
random generator to generate the ±12% of the switching
frequency dithering to reduce the EMI noise peaks.
The total power loss is:
PLOSS(TOT) =PLOSS(CON) + P
LOSS(TRAN)
The MOSFET junction temperature is given by:
TJ = PLOSS(TOT) ×RθJA + TA
The TJ must not exceed maximum junction temperature
under any conditions.
Freewheeling Diode
The free wheeling diode should have the reverse voltage
rating to accommodate the maximum input voltage. The
forward voltage drop should be small to get the lowest
conduction dissipation for high efficiency. The forward
current rating has to be at least equal to LED current. A
Schottky diode is recommended for highest efficiency.
Input Capacitor
The ceramic input capacitor is selected by voltage rating
and ripple current rating. To determine the input current
ripple rating, the RMS value of the input capacitor can be
found by:
ICIN(RMS) = ILED × D × (1- D)
The power loss in the input capacitor is:
P
= I2
× CIN
CIN(RMS)
ESR
LOSS(CIN)
M9999-032910-A
March 2010
13
Micrel, Inc.
MIC3203
placed as close to the LED as possible.
PCB Layout Guidelines
Warning!!! To minimize EMI and output noise, follow
these layout recommendations.
MOSFET
Place the MOSTET as close as possible to the MIC3203 to
avoid the trace inductance. Provide sufficient copper area on
MOSFET ground to dissipate the heat.
PCB Layout is critical to achieve reliable, stable and
efficient performance. A ground plane is required to
control EMI and minimize the inductance in power,
signal and return paths.
Diode
Place the Schottky diode on the same side of the board as
the IC and input capacitor.
The following guidelines should be followed to insure
proper operation of the MIC3203 regulator.
The connection from the Schottky diode’s Anode to the
switching node must be as short as possible.
IC
Use thick traces to route the input and output power
lines.
The diode’s Cathode connection to the RCS must be keep as
short as possible.
Signal and power grounds should be kept separate and
connected at only one location.
RC Snubber
If a RC snubber is needed, place the RC snubber on the
same side of the board and as close to the Schottky diode
as possible.
Input Capacitor
Place the input capacitors on the same side of the board
and as close to the IC as possible.
RCS (Current-Sense Resistor)
Keep both the VIN and PGND traces as short as
possible.
VIN pin and CS pin must be as close as possible to RCS.
Make a Kelvin connection to the VIN and CS pin respectively
for current sensing.
Place several vias to the ground plane close to the input
capacitor ground terminal, but not between the input
capacitors and IC pins.
Trace Routing Recommendation
Use either X7R or X5R dielectric input capacitors. Do not
use Y5V or Z5U type capacitors.
Keep the power traces as short and wide as possible. One
current flowing loop is during the MOSFET ON time, the
traces connecting the input capacitor CIN, RCS, LEDs,
Inductor, the MOSFET and back to CIN. The other current
flowing loop is during the MOSFET OFF time, the traces
connecting RCS, LED, inductor, free wheeling diode and back
to RCS. These two loop areas should kept as small as
possible to minimize the noise interference,
Do not replace the ceramic input capacitor with any
other type of capacitor. Any type of capacitor can be
placed in parallel with the input capacitor.
If a Tantalum input capacitor is placed in parallel with the
input capacitor, it must be recommended for switching
regulator applications and the operating voltage must be
derated by 50%.
Keep all analog signal traces away from the switching node
and its connecting traces.
In “Hot-Plug” applications, a Tantalum or Electrolytic
bypass capacitor must be placed in parallel to ceramic
capacitor to limit the over-voltage spike seen on the
input supply with power is suddenly applied. In this case
an additional Tantalum or Electrolytic bypass input
capacitor of 22µF or higher is required at the input power
connection if necessary.
Inductor
Keep the inductor connection to the switch node
(MOSFET drain) short.
Do not route any digital lines underneath or close to the
inductor.
To minimize noise, place a ground plane underneath the
inductor.
Output Capacitor
If LED ripple current needs to be reduced then place a
4.7µF/50V capacitor across LED. The capacitor must be
M9999-032910-A
March 2010
14
Micrel, Inc.
MIC3203
Ripple Measurements
To properly measure ripple on either input or output of a
switching regulator, a proper ring in tip measurement is
required. Standard oscilloscope probes come with a
grounding clip, or a long wire with an alligator clip.
Unfortunately, for high-frequency measurements, this
ground clip can pick-up high-frequency noise and
erroneously inject it into the measured output ripple.
The standard evaluation board accommodates a home
made version by providing probe points for both the
input and output supplies and their respective grounds.
This requires the removing of the oscilloscope probe
sheath and ground clip from a standard oscilloscope
probe and wrapping a non-shielded bus wire around the
oscilloscope probe. If there does not happen to be any
non-shielded bus wire immediately available, the leads
from axial resistors will work. By maintaining the shortest
possible ground lengths on the oscilloscope probe, true
ripple measurements can be obtained.
Figure 2. Low Noise Measurement
M9999-032910-A
March 2010
15
Micrel, Inc.
MIC3203
Evaluation Board Schematic
M9999-032910-A
March 2010
16
Micrel, Inc.
MIC3203
Bill of Materials
Item
Part Number
Manufacturer
AVX(1)
Description
Qty.
12105C475KAZ2A
GRM32ER71H475KA88L
12105C475KAZ2A
GRM32ER71H475KA88L
C3225X7S1H475M
08053D105KAT2A
GRM21BR71E105KA99L
C2012X7R1E105K
(Open) 08055A271JAT2A
(Open) GRM2165C2A271JA01D
SK36-TP
C1, C5
4.7µF/50V, Ceramic Capacitor, X7R, Size 1210
2
Murata(2)
AVX(1)
Murata(2)
TDK(3)
AVX(1)
Murata(2)
TDK(3)
AVX(1)
Murata(2)
MCC(4)
Fairchild(5)
Diodes, Inc.(6)
TDK(3)
C2
4.7µF/50V, Ceramic Capacitor, X5R, Size 1210
1
1µF/25V, Ceramic Capacitor, X5R, Size 0805
1µF/25V, Ceramic Capacitor, X7R, Size 0805
1
1
C3
C4
D1
270pF/50V, Ceramic Capacitor NPO, Size 0805
60V, 3A, SMC, Schottky Diode
1
1
SK36
SK36-7-F
L1
SLF10145T-680M1R2
FDS5672
68µH, 1.2A, 0.14Ω, SMT, Power Inductor
1
1
M1
Fairchild(7)
MOSFET, N-CH, 60V, 12A, SO-8
Stackpole
R1
CSR 1/2 0.2 1% I
0.2ꢀ Resistor, 1/2W, 1%, Size 1206
1
Electronics, Inc(8)
R2, R3
R4
CRCW08051003FKEA
CRCW08050000FKEA
(Open) CRCW08052R20FKEA
CRCW08051002FKEA
Vishay(9)
Vishay(9)
Vishay(9)
Vishay(9)
100kꢀ Resistor, 1% , Size 0805
0ꢀ Resistor, 1%, Size 0805
2.2ꢀ Resistor, 1%, Size 0805
10kꢀ Resistor, 1% , Size 0805
2
1
1
1
R5
R6
High Brightness LED Driver Controller with High-Side
Current Sense
U1
MIC3203YM
Micrel, Inc.(10)
1
Notes:
1. AVX: www.avx.com.
2. Murata: www.murata.com.
3. TDK: www.tdk.com.
4. MCC: www.mccsemi.com.
5. Fairchild: www.fairchildsemi.com.
6. Diodes Inc. : www.diodes.com.
7. Fairchild : www.Fairchildsemi.com.
8. Stackpole Electronics: www.seielect.com.
9. Vishay: www.vishay.com.
10. Diodes Inc. : www.diodes.com.
11. Micrel, Inc.: www.micrel.com.
M9999-032910-A
March 2010
17
Micrel, Inc.
MIC3203
PCB Layout Recommendation
Top Assembly
Top Layer
M9999-032910-A
March 2010
18
Micrel, Inc.
MIC3203
PCB Layout Recommendation (Continued)
Bottom Layer
M9999-032910-A
March 2010
19
Micrel, Inc.
MIC3203
Package Information
8-Pin SOIC
M9999-032910-A
March 2010
20
Micrel, Inc.
MIC3203
Recommended Landing Pattern
8-Pin SOIC
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2010 Micrel, Incorporated.
M9999-032910-A
March 2010
21
相关型号：
©2020 ICPDF网 联系我们和版权申明