TM
MP3204
1.3MHz Fixed Frequency
5 White LED Driver with Open LED Protection
The Future of Analog IC Technology
TM
DESCRIPTION
The MP3204 is a step-up converter designed
for driving up to 5 series white LEDs from a
single cell Lithium Ion battery. The MP3204
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. The OV pin
monitors the output voltage and turns off the
converter if an over-voltage condition is present
due to an open circuit condition.
The MP3204 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload. The MP3204 is available in a small
6-pin TSOT23 package.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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
Open Load Shutdown
Available in a TSOT23-6 Package
Cell Phones
Handheld Computers and PDAs
Digital Still Cameras
Small LCD Displays
APPLICATIONS
EVALUATION BOARD REFERENCE
Board Number
EV3204DJ-00A
Dimensions
1.9”X x 1.8”Y x 0.4”Z
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
V
IN
5V
Efficiency vs
LED Current
LED1
LED2
EFFICIENCY (%)
LED3
6
1
SW
5
OV
4
2
IN
EN
LED4
LED5
EN
MP3204
FB
GND
3
88
87
86
85
84
83
82
81
80
79
78
77
4 LEDs
5 LEDs
3 LEDs
V
IN
=3.6V
5
10
15
LED CURRENT (mA)
20
MP3204 Rev. 1.4
10/8/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
1
TM
MP3204 – 6V, 1.3MHz WHITE LED DRIVER
PACKAGE REFERENCE
TOP VIEW
SW
GND
FB
1
2
3
6
5
4
IN
OV
EN
ABSOLUTE MAXIMUM RATINGS
(1)
SW, OV Pins ...............................
–
0.5V to +28V
All Other Pins..............................
–
0.3V to +6.5V
Storage Temperature ..............
–
55°C to +150°C
Recommended Operating Conditions
(2)
IN Supply Voltage.............................. 2.5V to 6V
Output Voltage....................................V
IN
to 21V
Operating Temperature .............
–
40°C to +85°C
Thermal Resistance
Part Number*
MP3204DJ
*
Package
TSOT23-6
Temperature
–40°C to +85°C
(3)
TSOT23-6.............................. 220 .... 110..
°C/W
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.
θ
JA
θ
JC
For Tape & Reel, add suffix –Z (eg. MP3204DJ–Z)
For RoHS Compliant Packaging, add suffix –LF
(eg. MP3204DJ–LF–Z)
ELECTRICAL CHARACTERISTICS
V
IN
= V
EN
= 5V, T
A
= +25°C, unless otherwise noted.
Parameters
Operating Input Voltage
Supply Current (Shutdown)
Supply Current (Quiescent)
Switching Frequency
Maximum Duty Cycle
Under Voltage Lockout
IN Under Voltage Lockout
Under Voltage Lockout
Hysteresis
Open Lamp Shutdown
Threshold
Enable
EN Threshold
EN Threshold
EN Hysteresis
EN Input Bias Current
Feedback
FB Voltage
FB Input Bias Current
Output Switch
SW On-Resistance
(4)
SW Current Limit
Thermal Shutdown
(4)
Note:
4) Guaranteed by design, not tested.
Symbol
V
IN
Condition
V
EN
= 0V
V
FB
= 0.15V
Min
2.5
Typ
0.1
690
1.3
92
2.25
92
Max
6
1
750
1.5
Units
V
µA
µA
MHz
%
V
mV
V
f
SW
V
FB
= 0V
UVLO
V
IN
Rising
1.0
85
2.45
V
OV
V
OV
Rising
V
EN
Rising
V
EN
Rising, V
IN
= 2.5V
V
EN
= 0V, 5V
94
–600
1.0
0.8
28
1.35
90
1
104
–300
0.5
350
160
114
1.6
V
V
mV
μA
mV
nA
Ω
mA
°C
V
FB
= 0.1V
R
ON
Duty Cycle = 60%
MP3204 Rev. 1.4
10/8/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
2
TM
MP3204 – 6V, 1.3MHz WHITE LED DRIVER
PIN FUNCTIONS
Pin #
1
2
3
Name Description
SW
GND
FB
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 MP3204 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.
Over Voltage Input. OV measures the output voltage for open circuit protection. Connect OV to
the output at the top of the LED string.
Input Supply. This pin must be locally bypassed.
4
5
6
EN
OV
IN
OPERATION
The MP3204 uses constant frequency, peak
current mode boost regulator architecture to
regulate a series of white LEDs. The operation
of the MP3204 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 sub-
harmonic oscillations at duty cycles greater
than 50%, 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. 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. This is the
manner in which the peak current level keeps
the output in regulation. If the feedback voltage
begins to drop, the output of the error amplifier
increases. This results in more current flowing
through the power FET, thus increasing the
power delivered to the output.
FB
3
+
-
-
+
AMPLIFIER
CONTROL
LOGIC
M1
1 SW
104mV
PWM
COMPARATOR
-
+
+
CURRENT
SENSE
AMPLIFIER
1.3MHz
OSC
2 GND
Figure 1—Functional Block Diagram
MP3204 Rev. 1.4
10/8/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
3
TM
MP3204 – 6V, 1.3MHz WHITE LED DRIVER
APPLICATION INFORMATION
V
IN
2.5V to 6V
CMDSH-3
LED1
LED2
6
IN
EN
1
SW
OFF ON
4
2
MP3204
OV
FB
5
3
LED3
GND
Figure 2—Driving 3 White LEDs
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 of up to 1µF may be used.
A 22µH inductor with low DCR (inductor
resistance) is recommended for improved
efficiency. A 1µF ceramic capacitor is
recommended for the input capacitance in the
real system. Schottky diodes have fast recovery
times and a low forward voltage and are also
recommended. Schottky diodes with ratings of
100mA to 200mA are sufficient for use with the
MP3204. The switching characteristics during
normal operation can be seen in Figure 3. The
MP3204 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.
V
SW
5V/div.
V
OUT
RIPPLE
(AC COUPLED)
50mV/div.
I
L
100mA/div.
Figure 3—Steady-State Operation
(V
IN
=3.6V, 3 LEDs, 20mA)
MP3204 Rev. 1.4
10/8/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
4
TM
MP3204 – 6V, 1.3MHz WHITE LED DRIVER
Table 1—I
LED
vs. R1
I
LED
(mA)
1
5
10
15
20
R1 (Ω)
104
20.8
10.4
6.93
5.2
Figure 4 shows the startup behavior of the
MP3204. 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.
V
EN
5V/div.
V
OUT
5V/div.
I
IN
100mA/div.
Figure 4—Startup Waveforms
(V
IN
=3.6V, 3 LEDs, 20mA)
Figure 5 shows the dependence on current limit
versus duty cycle.
500
Analog and Digital Dimming
There are three different ways to control
dimming for the MP3204 during normal
operation. The first way uses a DC voltage to
control the feedback voltage, which 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.
V
DC
LED1
CURRENT LIMIT (mA)
400
LED2
300
200
100
0
LED3
MP3204
FB
3
0
20
40
60
80
DUTY CYCLE (%)
100
Figure 5—Current Limit vs. Duty Cycle
Setting the LED Current
The LED current is controlled by the feedback
resistor, R1, as shown in Figure 2. The current
through the LEDs is equal to 104mV/R1. Table
1 shows the selection of resistors for a given
LED current.
Figure 6—Dimming Control Using a DC
Voltage
MP3204 Rev. 1.4
10/8/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
5
京公网安备 11010802033920号
EEWORLD
