MPS MP3205DJ

TM
MP3205
1.3MHz Fixed Frequency
5 White LED Driver
The Future of Analog IC Technology
TM
DESCRIPTION
FEATURES
The MP3205 is a step-up converter designed
for driving up to 5 series white LEDs from a
single cell Lithium Ion battery. The MP3205
uses current mode, fixed frequency architecture
to regulate the LED current, which is measured
through an external current sense resistor. Its
low 104mV feedback voltage reduces power
loss and improves efficiency.
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•
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The MP3205 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload. The MP3205 is available in a small
5-pin TSOT23 package.
EVALUATION BOARD REFERENCE
Board Number
Dimensions
EV3205DJ-00A
1.9”X x 1.8”Y x 0.4”Z
On Board Power MOSFET
Drives up to 5 Series White LEDs
Up to 87% Efficiency
Over 1MHz Fixed Switching Frequency
Low 104mV Feedback Voltage
Soft-Start/PWM Dimming
UVLO, Thermal Shutdown
Internal Current Limit
Available in a TSOT23-5 Package
APPLICATIONS
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Cell Phones
Handheld Computers and PDAs
Digital Still Cameras
Small LCD Displays Application
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
LED Current
CMDSH-3
VIN
5V
LED1
EFFICIENCY (%)
LED2
LED3
5
EN
4
2
1
IN
EN
LED4
SW
LED5
MP3205
GND
FB
3
88
87
86
85
84
83
82
81
80
79
78
77
4 LEDs
5 LEDs
3 LEDs
VIN=3.6V
5
10
15
LED CURRENT (mA)
MP3205-TAC-S01
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
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© 2005 MPS. All Rights Reserved.
20
MP3205-EC01
1
TM
MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
SW ............................................... –0.5V to +28V
All Other Pins.............................. –0.3V to +6.5V
Storage Temperature ..............–55°C to +150°C
TOP VIEW
SW
1
5
IN
Recommended Operating Conditions
GND
2
FB
3
4
IN Supply Voltage.............................. 2.5V to 6V
Output Voltage....................................VIN to 21V
Operating Temperature .............–40°C to +85°C
EN
Thermal Resistance
MP3205-PD01_TSOT23
(3)
θJA
θJC
TSOT23-5.............................. 220 .... 110.. °C/W
Part Number*
Package
Temperature
MP3205DJ
TSOT23-5
–40°C to +85°C
*
(2)
For Tape & Reel, add suffix –Z (eg. MP3205DJ–Z)
For Lead Free, add suffix –LF (eg. MP3205DJ –LF–Z)
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
ELECTRICAL CHARACTERISTICS
VIN = VEN = 5V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Using Parameter Set Heading
Operating Input Voltage
VIN
Supply Current (Shutdown)
Supply Current (Quiescent)
Switching Frequency
fSW
Maximum Duty Cycle
Undervoltage Lockout
IN Under Voltage Lockout
UVLO
Under Voltage Lockout
Hysteresis
Enable
EN Threshold
EN Threshold
EN Hysteresis
EN Input Bias Current
Feedback
FB Voltage
FB Input Bias Current
Output Switch
SW On-Resistance (4)
RON
SW Current Limit
Thermal Shutdown (4)
Condition
Min
Typ
2.5
VEN = 0V
VFB = 0.15V
VFB = 0V
1.0
85
VIN Rising
0.1
690
1.3
92
2.25
Max
Units
6
1
750
1.5
V
µA
µA
MHz
%
2.45
V
92
VEN Rising
VEN Rising, VIN = 2.5V
1.0
0.8
1.35
mV
1.6
90
VEN = 0V, 5V
VFB = 0.1V
Duty Cycle = 60%
1
94
–600
104
–300
0.5
350
160
114
V
V
mV
µA
mV
nA
Ω
mA
°C
Note:
4) Guaranteed by design.
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
2
TM
MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
PIN FUNCTIONS
Pin #
Name Description
1
SW
2
GND
3
FB
4
EN
5
IN
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power
inductor and output rectifier to SW. SW can swing between GND and 25V.
Ground.
Feedback Input. The MP3205 regulates the voltage across the current sense resistor between
FB and GND. Connect a current sense resistor from the bottom of the LED string to GND.
Connect the bottom of the LED string to FB. The regulation voltage is 104mV.
Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns
it off. When not used, connect EN to the input source for automatic startup. The EN pin cannot
be left floating.
Input Supply Pin. Must be locally bypassed.
OPERATION
The MP3205 uses a constant frequency, peak
current mode boost regulator architecture to
regulate the series string of white LEDs. The
operation of the MP3205 can be understood by
referring to the block diagram of Figure 1. At the
start of each oscillator cycle the FET is turned on
through the control circuitry. To prevent subharmonic oscillations at duty cycles greater than 50
percent, a stabilizing ramp is added to the output of
the current sense amplifier and the result is fed into
the positive input of the PWM comparator.
FB
When this voltage equals the output voltage of
the error amplifier the power FET is turned off.
The voltage at the output of the error amplifier is
an amplified version of the difference between
the 104mV reference voltage and the feedback
voltage. In this way the peak current level keeps
the output in regulation. If the feedback voltage
starts to drop, the output of the error amplifier
increases. This results in more current to flow
through the power FET, thus increasing the
power delivered to the output.
+
+
AMPLIFIER
CONTROL
LOGIC
M1
SW
PWM
COMPARATOR
104mV
+
+
GND
CURRENT
SENSE
AMPLIFIER
1.3MHz
OSC
MP3205-F03-BD01
Figure 1—Functional Block Diagram
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
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TM
MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
APPLICATION INFORMATION
VIN
2.5V to 6V
CMDSH-3
5
1
IN
OFF ON
4
2
EN
LED1
SW
LED2
MP3205
GND
LED3
FB
3
MP3205_F02_AP_S01
Figure 2—Driving 3 White LEDs
COMPONENT SELECTION
A typical application circuit can be seen in Figure
2. The 3 white LEDs can be driven from a voltage
supply range of 2.5V to 6V at an output current of
20mA. A 0.22µF output capacitor is sufficient for
most applications but an output capacitor up to
1µF may be used. A 22µH inductor with low DCR
(Inductor resistance) is recommended to improve
efficiency. A 1µF ceramic capacitor is
recommended for the input capacitance in the
real system. Schottky diodes have fast recovery
and a low forward voltage and are recommended.
Schottky diodes rated with 100mA to 200mA
are sufficient for the MP3205. The switching
characteristics during normal operation can be
seen in Figure 3. The MP3205 has internal
soft-start to limit the amount of current through
VIN at startup and to also limit the amount of
overshoot on the output. The current limit is
increased by a fourth every 40µs giving a total
soft-start time of 120µs.
Figure 4 shows the startup behavior of the
MP3205. The ramped voltage that is added to the
current sense amplifier reduces the current output
as the duty cycle increases. As more LEDs are
added, the output voltage rises but the current that
can be delivered to the load is reduced as well.
VEN
5V/div.
VOUT
5V/div.
IIN
100mA/div.
MP3205_F04_WF02
Figure 4—Startup Waveforms
VIN=3.6V, 3 LEDs, 20mA
Figure 5 shows the dependence on current limit
versus duty cycle.
500
CURRENT LIMIT (mA)
VSW
5V/div.
VOUT RIPPLE
(AC COUPLED)
50mV/div.
IL
100mA/div.
400
300
200
100
0
MP3205_F03_WF01
Figure 3—Steady-State Operation
VIN=3.6V, 3 LEDs, 20mA
MP3205 Rev. 1.3
7/13/2005
0
20
40
60
80
DUTY CYCLE (%)
100
MP3205_F05
Figure 5—Current Limit vs. Duty Cycle
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© 2005 MPS. All Rights Reserved.
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TM
MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
Setting the LED Current
The LED current is controlled by the feedback
resistor, R1, in Figure 2. The current through
the LEDs is given by the equation 104mV/R1.
Table 1 shows the selection of resistors for a
given LED current.
signal used in Figure 7 should be 1KHz or
below due to the soft start function.
LED1
LED2
Table 1—ILED vs. R1
ILED (mA)
R1 (Ω)
1
5
10
15
20
104
20.8
10.4
6.93
5.2
Analog and Digital Dimming
There are three different ways to control dimming
for the MP3205 during normal operation. The first
way uses a DC voltage to control the feedback
voltage. This can be seen in Figure 6. As the DC
voltage increases, current starts flowing down R1,
R2 and R3. The loop will continue to regulate the
feedback voltage to 104mV. Thus the current has
to decrease through the LEDs by the same
amount of current as is being injected from the
DC voltage source. With a VDC from 0V to 2V, the
resistor values shown for R2 and R3 can control
the LED current from 0mA to 20mA.
VDC
LED3
PWM
4
MP3205
EN
FB
3
MP3205_F07_S01
Figure 7—PWM Dimming Control Using a
Logic Signal
If the PWM signal is above 1KHz, dimming can
be achieved by using the circuit shown in
Figure 8.
LED1
MP3205
LED2
FB
3
LED3
PWM
LED1
MP3205_F08_S01
MP3205
FB
LED2
Figure 8—Dimming Control Using a Filtered
PWM Signal
LED3
Layout Considerations
Careful attention must be paid to the PCB
board layout and component placement. Proper
layout of the high frequency switching path is
critical to prevent noise and electromagnetic
interference problems. Due to the high
frequency switching the length and area of all
the traces connected to the switch node should
be minimized. Refer to the evaluation board
EV3205DJ-00A for a sample layout of
theBMP3205.
3
MP3205_F06_S01
Figure 6—Dimming Control Using a DC Voltage
Other applications need to use a logic signal to
do the dimming. This can be seen in Figure 7.
The PWM signal is applied to the EN pin of the
MP3205. The LEDs will switch between full load
to completely shut off. The average current
through the LEDs will increase proportionally to
the duty cycle of the PWM signal. The PWM
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
5
TM
MP3205 – 1.3 MHz FIXED FREQUENCY 5 WHITE LED DRIVER
VIN
2.5V to 6V
CMDSH-3
5
IN
4
OFF ON
2
LED1
1
EN
LED2
SW
LED3
MP3205
GND
FB
3
MP3205_F09
Figure 9—LED Driver with Overload Protection
PACKAGE INFORMATION
TSOT23-5
2 .9 0 B S C
3
0 .9 5 0
TYP.
0 .9 5 0
TYP.
CL
2.80BSC
1.60BSC
3
1 0 °T Y P .
(2 p l cs)
+ 4°
- 0°
0°
0.25
±0.10
Ga u g e P l a n e
CL
0.87±0.03
1.00Max.
0 .3 0 0 (M i n )
0 .5 0 0 (M a x)
(5 P L C S )
BSC .
0 .4 0 0
S E A T IN G P L A N E
0.00- 0.10
0 .1 2 7 T Y P .
10°T Y P .
(2 p l c s )
D ime n sio n s a re in millime te rs
Note:
1.Dimens ions and toleranc es are as per A NSI Y 14.5M, 1994.
2. Die is f ac ing up f or mold. Die is f ac ing dow n f or trim/f orm, ie. Rev ers e trim/f orm
3
3. Dimens ions are ex c lus iv e of mold f las h and gate burr.
4.The f ootlength meas uring is bas ed on the gauge plane method.
5. A ll s pec if ic ation c omply to Jedec Spec MO193 Is s ue C.
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP3205 Rev. 1.3
7/13/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
6