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MIC3291-25YD6
Schematic [ru]
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Micrel MIC3291-18YD6, MIC3291-18YML, MIC3291-25YD6, MIC3291-25YML Schematic [ru]

MIC3291
1.2MHz PWM White LED Driver
with Internal Schottky Diode and
Single-Wire Linear Brightness
Control
General Description
The MIC3291 is a PWM switching boost regulator that is optimized for constant current white LED (WLED) driver applications. The MIC3291 features an internal Schottky diode, allowing an efficient DC/DC solution that requires only four external components.
The MIC3291 allows for a single-wire simple digital interface to control the dimming over 16 steps with a linear scale. The preprogramming feature allows the user to select any one of the 16 WLED current levels as the start up brightness level.
The feedback voltage of the MIC3291 is only 250mV, allowing high efficiency while retaining excellent accuracy for the WLED current.
The MIC3291 implements a constant frequency 1.2MHz PWM control scheme. The high frequency PWM operation saves board space by reducing external component sizes. The 1.2MHz PWM scheme also reduces switching noise and ripple to the input power source.
The 2.5V to 6.5V input voltage range of the MIC3291 allows direct operation from single cell Li-Ion as well as 3 to 4 cell NiCad/NiMH/Alkaline batteries. Battery life is preserved with a low 1µA shutdown current.
The MIC3291 is available in a low profile Thin SOT23 6­pin and 2mm × 2mm MLF temperature range of –40°C to +125°C.
Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com
___________________________________________________________________________________________________________
®
8-pin packages with a junction
.
Features
• Single wire combines 16 level linear brightness and shutdown control
• 18V / 25V OVP options supports up to four and six
WLEDs
• Startup in any one of 16 brightness levels
• Internal Schottky diode
• 2.5V to 6.5V input voltage
• 1.2MHz PWM operation
• Over 500mA switch current
• 250mV reference voltage
• ±5% LED current accuracy
• <1µA shutdown current
• UVLO and over-temperature protection
• Thin SOT23-6L package option
• 2mm × 2mm leadless MLF
o
• –40
C to +125oC junction temperature range
Applications
• Mobile handsets
• LCD handset backlighting
• Digital cameras
• Portable media players/MP3 players
• Portable applications
®
package option
Typical Application
White LED Driver with OVP and Digital Control
MLF and MicroLead Frame are registered trademarks of Amkor Technologies, Inc.
September 2010
M9999-092810
(408) 944-0800
Micrel, Inc. MIC3291
Ordering Information
Part Number
1
Marking Code4 Output Voltage
Over-Voltage
Protection
MIC3291-18YD6 W18F Adjustable 18V
MIC3291-25YD6 W25F Adjustable 25V
MIC3291-18YML
MIC3291-25YML
Notes:
1. Other options available. Contact Micrel Marketing for details.
2. MLF
3. MLF® ● = Pin 1 identifier.
4. Overbar ( ¯ )and Underbar symbols ( _ ) may not be to scale.
®
is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
FWA
FWB
Adjustable 18V
Adjustable 25V
Pin Configuration
Junction
Temperature Range
−40°C to +125°C
−40°C to +125°C
Package
TSOT23-6
TSOT23-6
−40°C to +125°C 2mm × 2mm MLF
−40°C to +125°C 2mm × 2mm MLF
2,3
®
®
2mm × 2mm 8-Pin MLF® (ML)
Pin Description
Pin Number
8-pin MLF
1 6 OUT Output and over-voltage protection (output) 2 3 4 DC Single pin digital control. See diagrams.
4
5
6 3 FB
7 1 SW Switch Node (Input): Internal power BIPOLAR collector. 8 2 GND Ground (Return): Ground.
Pad
®
Pin Number
TSOT23-6 (D6)
(Top View)
SOT23-6
Pin Name Pin Name
5 VIN Supply (Input): 2.5V to 6.5V for internal circuitry.
−
−
GND Ground (Return): Ground.
NC No connect (no internal connection to die)
Feedback (Input): Output voltage sense node. Connect the cathode of the LED to this pin.
−
GND Ground (Return): Backside pad.
(Top View)
September 2010 2
M9999-092810
(408) 944-0800
Micrel, Inc. MIC3291
Absolute Maximum Ratings
Supply Voltage (VIN) .................................................... 7.5V
Switch Voltage (V Digital Control Voltage (V FB Voltage (V Switch Current (I Ambient Storage Temperature (T ESD Rating
(2)
)..................................... –0.3V to 27V
SW
) ..............................–0.3 to VIN
DC
)............................................................. 6V
FB
)........................................................ 2A
SW
................................................................2KV
Electrical Characteristics
TA = +25oC, VIN = 3.6V, V
Symbol Parameter Condition Min. Typ. Max. Units
OUT
= 10V, I
OUT
(1)
Operating Ratings
Supply Voltage (VIN) …………………..……......2.5V to 6.5V
Output Voltage (V
OUT
Junction Temperature Range (T Package Thermal Impedance
)......... –65°C to +150°C
S
θ θ
2mm × 2mm MLF®-8L ................................. 93°C/W
JA
TSOT23-6 ..................................................235°C/W
JA
(4)
= 20mA, unless otherwise noted. Bold values indicate −40°C ≤ T
VIN Supply Voltage Range 2.5 6.5 V V
Under-Voltage Lockout 1.8 2.1 2.4 V
UVLO
I
Quiescent Current VFB >500mV 2 4 mA
VIN
I
SD
V
Feedback Voltage
FB
Shutdown Current (DC Pin Low ) VDC = 0V for > 2ms. 0.01
(±5%)
Feedback Input Current VFB = 250mV
IFB
D
Maximum Duty Cycle
MAX
Line Regulation Load Regulation
2.5V ≤ V 5mA ≤ I
≤ 4.5V
IN
≤ 20mA
OUT
ISW Switch Current Limit VIN = 3.6V
VDC DC Pin Thresholds
High Low
IDC DC Pin Current VDC = 3.6V 5 10
V
= 2.8V to 5.5V
t
t
t
t t t
t
T
Shutdown Pulse Width
shutdown
MODE_UP
MODE_DOWN
Turn-On Delay Time VIN = 2.8V to 5.5V
start_up
Programming Pulse Width Low VIN = 2.8V to 5.5V
prog_low
prog_high
Minimum Delay for Mode Change
delay
prog_setup
Count UP Mode Pulse Width
Count Down Mode Pulse Width
Programming Pulse Width High VIN = 2.8V to 5.5V
First Pulse Window for Preprogramming
IN
= Low
V
DC
V
= 2.8V to 5.5V
IN
V
= Low
DC
V
= 2.8V to 5.5V
IN
V
= Low
DC
V
= 2.8V to 5.5V
IN
V
= High
DC
VIN = 2.8V to 5.5V
fSW Oscillator Frequency 1 1.2 1.35 MHz
(3)
) …………….… ...............(VIN to V
) …… .... −40°C to +125°C
J
≤ +125°C.
J
237
86
500
1.1
1
250 450
0.5
0.5
263
90 %
750
1200
0.4
μA
mV
nA
%
mA
V
μA
1260
100
420
140
1 1
140
35
160
500
µs
µs
µs
µs
32 32
50
µs µs
µs
µs
OVP
)
September 2010 3
M9999-092810
(408) 944-0800
Micrel, Inc. MIC3291
Electrical Characteristics
TA = +25oC, VIN = 3.6V, V
Symbol Parameter Condition Min. Typ. Max. Units
VD Schottky Forward Drop ID = 150mA IRD Schottky Leakage Current VR = 30V
V
Over-Voltage Protection
OVP
Tj
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, T junction-to-ambient thermal resistance, θ temperature, and the regulator will go into thermal shutdown.
2. IC devices are inherently ESD sensitive. Handling precautions required. Human body model, 1.5kΩ in series with 100pF.
3. This device is not guaranteed to operate beyond its specified operating rating.
4. Specification for packaged product only.
Over-Temperature Threshold Shutdown
OUT
= 10V, I
(4)
(Continued)
= 20mA, unless otherwise noted. Bold values indicate −40°C ≤ T
OUT
3291- 18 only (nominal voltage) 3291- 25 only (nominal voltage)
15
22.1
≤ +125°C.
J
0.8 1 V 4
16.5 18
23.5 25
150
, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die
JA
μA
°C
J(Max)
V
, the
September 2010 4
M9999-092810
(408) 944-0800
Micrel, Inc. MIC3291
)
)
)
Typical Characteristics
Feedback Voltage
vs. Brightness Level
275 250 225 200 175 150 125 100
75 50
FEEDBACK VOLTAGE ( mV
25
0
0 1 2 3 4 5 6 7 8 9 10 11 1213 1415
BRIGHTNESS LEVEL (0-15)
6 Series White LED
100
90
80
70
60
50
40
30
EFFICIENCY (%)
20
10
0
Efficiency
VIN = 4.2V
VIN = 3.6V
L = 22µH
= 0.27µF
C
OUT
0 5 10 15 20 25
WHITE LED CURRENT (mA)
Peak Switch Current
vs. In put Volta ge
1000
900
800
700
600
500
400
FEEDBACK VOLTAGE ( mV
300
200
2.53 3.544.5 55.5
INPUT VOLTAGE (V)
VIN = 2.8V
6 Series White LED
100
90
80
70
60
50
40
30
EFFICIENCY (%)
20
10
0
Efficiency
VIN = 2.8V
VIN = 4.2V
V
= 3.6V
IN
L = 10µH C
= 0.27µF
OUT
0 5 10 15 20 25
WHI TE LED CURR E NT (mA)
3 Series White LED
100
90
80
70
60
50
40
EFFICIENCY (%)
30
20
10
0
Efficiency
= 3.6V
V
IN
VIN = 4.2V
0 5 10 15 20 25
WHITE LE D CURRENT (mA)
VIN = 2.8V
L = 22µH
= 0.27µF
C
OUT
Input Curren t
vs. Input Voltage
350
300
250
200
150
100
INPUT CURRENT (mA)
50
6 LEDs
3 LEDs
0
2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
L=10µH
3 Series White LED
100
90
80
70
60
50
40
30
EFFICIENCY (%)
20
10
0
Efficiency
VIN = 2.8V
= 3.6V VIN = 4.2V
V
IN
L = 10µH
= 0.27µF
C
OUT
0 5 10 15 20 25
WHITE LED CURRENT (mA )
Feedback Voltage
vs. In put Voltage
260
258
256
254
252
250
248
246
244
FEEDBACK VOLTAGE ( mV
242
240
2.533.544.555.56
INPUT VOLTAGE (V)
Current Limit
vs. Input Voltage
1
0.95
0.9
0.85
0.8
0.75
0.7
CURRENT LIMIT (A)
0.65
0.6
2.6 3.1 3.6 4.1 4.6 5.1 5.6 6.1 6.6
INPUT VOLTAGE (V)
September 2010 5
M9999-092810
(408) 944-0800
Micrel, Inc. MIC3291
Functional Characteristics
September 2010 6
M9999-092810
(408) 944-0800
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