MP24183
1A, 55V, Programmable Frequency
White LED Driver
END OF LIFE, REFER TO MP2483
DESCRIPTION
FEATURES
The MP24183 is a 55V, 1A, white LED driver
suitable for either step-down or inverting
step-up/down applications. It achieves 1A peak
output current over a wide input supply range
with excellent load and line regulation. Current
mode operation provides fast transient
response and eases loop stabilization. Fault
condition protection includes thermal shutdown,
cycle-by-cycle peak current limiting, input over
voltage protection, open strings protection and
output short circuit protection.
The MP24183 incorporates both DC and PWM
dimming onto a single control pin. The separate
input reference ground pin allows for direct
enable and/or dimming control for a positive to
negative power conversion.
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The MP24183 requires a minimum number of
readily available standard external components
and is available in a 10-pin 3mm x 3mm QFN
package.
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1A Maximum Output Current
Unique Step-up/down Operation (BuckBoost Mode)
Wide 4.5V to 55V Operating Input Range for
Step-Down Applications (Buck Mode)
0.28Ω Internal Power MOSFET Switch
Adjustable Switching Frequency
Analog and PWM Dimming
0.198V Reference Voltage
5μA Shutdown Mode
No minimum LED required
Stable with Low ESR Output Ceramic
Capacitors
Cycle-by-Cycle Over Current Protection
Thermal Shutdown Protection
Open Strings Protection
Input Over Voltage Protection
Output Short Circuit Protection
Available in 10-Pin 3x3 QFN Package
APPLICATIONS
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General LED Illuminations
LCD Backlight Panels
Handheld Computers
Automotive Internal Lighting
Portable Multimedia Players
Portable GPS Devices
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.
TYPICAL APPLICATION
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
1
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
ORDERING INFORMATION
Part Number*
MP24183DQ
Package
3x3 QFN10
Top Marking
Free Air Temperature (TA)
-40C to +85C
* For Tape & Reel, add suffix –Z (e.g. MP24183DQ–Z).
For RoHS compliant packaging, add suffix –LF (e.g. MP24183DQ–LF–Z)
PACKAGE REFERENCE
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance (4)
Supply Voltage VDD – VSS .............................60V
VSW – VSS .............................. -0.3V to VIN + 0.3V
VBST .....................................................VSW + 6V
VOVP – VSS ...................................... -0.3V to +6V
VEN – VINGND ................................... -0.3V to +6V
VDIM – VINGND .................................. -0.3V to +6V
VINGND – VSS ................................... -0.3V to 60V
Continuous Power Dissipation (TA = +25°C) (2)
………………………………………………....2.5W
Junction Temperature .............................. 150C
Lead Temperature ................................... 260C
Storage Temperature ............... -65C to +150C
3x3 QFN10 ............................. 50 ...... 12 ... C/W
θJA
θJC
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device function is not guaranteed outside of the
recommended operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
Recommended Operating Conditions (3)
Supply Voltage VDD – VSS ................ 4.5V to 55V
Operating Junct. Temp (TJ) ..... -40C to +125C
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
2
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
ELECTRICAL CHARACTERISTICES
VIN = 12V, TA = +25C, all voltages with respect to VSS, unless otherwise noted.
Parameters
Feedback Voltage
Feedback Current
Switch-On Resistance (5)
Switch Leakage
Current Limit (5)
Oscillator Frequency
Symbol
VFB
IFB
RDS(ON)
Fold-back Frequency
Maximum Duty Cycle
Minimum On-Time (5)
Under Voltage Lockout Threshold Rising
Under Voltage Lockout Threshold Hysteresis
EN Input Current
EN OFF Threshold (w/Respect to INGND)
EN ON Threshold (w/Respect to INGND)
Minimum EN Dimming Threshold
Maximum EN Dimming Threshold
Supply Current (Quiescent)
Supply Current (Quiescent) at EN Off
Thermal Shutdown (5)
Open LED OV Threshold
Open LED OV Hysteresis
4.5V VIN 55V
VFB = 0.22V
Min
0.188
-50
Typ
0.198
2.0
Units
V
nA
mΩ
μA
A
fSW_default
VFB = 0.19V,
Rset=100kΩ
VFB = 0.19V, Rset
open
VFB = 0V, VOVP=0V
VFB = 0.19V
0.5
MHz
1
1.05
tON
3
IQ
Ioff
VOVP_ th
VOVP_ hys
Max
0.208
50
280
VEN = 0V, VSW = 0V
fSW
Default oscillator frequency
Condition
VEN = 2V
VEN Falling
VEN Rising
VFB = 0V
VFB = 0.2V
VEN = 2V, VFB = 1V
VEN=0V
1.35
250
90
100
3.3
100
2.1
1.65
3.6
0.4
0.6
1.25
1.1
0.7
1.4
0.8
3.4
150
1.2
60
0.6
0.8
1.5
1.0
15
1.3
MHz
kHz
%
ns
V
mV
μA
V
V
V
V
mA
μA
°C
V
mV
Notes:
5) Guaranteed by design.
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
3
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
PIN FUNCTIONS
Pin #
Name
1
VDD
2
3
4
5
6
7
8
9
10
Description
Supply Voltage. The MP24183 operates from a +4.5V to +55V unregulated input (with
respect to VSS). C1 is needed to prevent large voltage spikes from appearing at the input.
Power Return Pin. Connect to the lowest potential in the circuit, which is typically the anode
of the Schottky rectifier. This pin is the voltage reference for the regulated output voltage.
VSS
For this reason care must be taken in its layout. This node should be placed outside of the
D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into
the part. The exposed pad is also connected to this pin.
Over Voltage Protection Pin. Use a voltage divider to program OVP threshold. When the
OVP pin voltage reaches the shutdown threshold 1.2V, the switch will be turned off and will
recover when OVP voltage decreases sufficiently. When the OVP pin voltage (with respect
OVP
to VSS) is lower than 0.4V and FB pin voltage is lower than 0.1V, the chip reecognizes this
as short circuit condition and the operating frequency will be folded back. Program the OVP
pin voltage from 0.4V to 1.2V for normal operation.
LED Current Feedback Input. MP24183 regulates the voltage across the current sensing
resistor between FB and VSS. Connect the current sensing resistor from the bottom of the
FB
LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The
regulation voltage is 0.198V.
Output of error amplifier. Connect a 1nF or larger capacitor on COMP to improve the
COMP
stability and to provide a soft on at start up and PWM dimming.
Frequency Set Pin. Connect a resistor to VSS to set the switching frequency and an 1nF
RSET capacitor to VSS to bypass the noise. Leaving this pin open gets a default operating
frequency 1.35MHz.
On/Off Control Input and Dimming Command Input. A voltage greater than 0.6V will turn on
the chip. Both DC and PWM dimming are implemented on this pin. When the EN/DIM pin
EN/DIM voltage (with respect to INGND) rises from 0.7V to 1.4V, the LED current will change from
0% to 100% of the maximum LED current. To use PWM dimming, apply a 100Hz to 2kHz
square wave signal with amplitude greater than 1.4V to this pin.
INGND Input Ground Reference. This pin is the reference for the EN/DIM signal.
Bootstrap. A capacitor is connected between SW and BST pin to form a floating supply
BST
across the power switch driver. A 100nF or larger ceramic capacitor is recommended to
provide sufficient energy to drive the power switch’s gate above the supply voltage.
Switch Output. SW is the source of the internal MOSFET switch. Connect this pin to the
SW
power inductor and the cathode of the Schottky rectifier.
Exposed pad should be connected to VSS in step up/down mode.
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
4
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
TYPICAL PERFORMANCE CHARACTERISTICS
VIN=20V, ILED=0.7A, two 3W LED in series, step down application, unless otherwise noted.
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
5
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN=20V, ILED=0.7A, two 3W LED in series, step down application, unless otherwise noted.
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
6
MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
FUNCTIONAL BLOCK DIAGRAM
Figure 1—Functional Block Diagram
MP24183 Rev. 1.0
8/28/2008
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2008 MPS. All Rights Reserved.
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MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
END OF LIFE, REFER TO MP2483
OPERATION
The MP24183 is a current mode regulator. The
EA output voltage is proportional to the peak
inductor current.
At the beginning of a cycle, M1 is off. The EA
output voltage is higher than the current sense
amplifier output, and the current comparator’s
output is low. The rising edge of the 1.35MHz
CLK signal sets the RS Flip-Flop. Its output
turns on M1 thus connecting the SW pin and
inductor to the input supply.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier. Ramp
compensation is summed to the Current Sense
Amplifier output and compared to the Error
Amplifier output by the PWM Comparator.
When the sum of the Current Sense Amplifier
output and the Slope Compensation signal
exceeds the EA output voltage, the RS FlipFlop is reset and M1 is turned off. The external
Schottky rectifier diode (D1) conducts the
inductor current.
If the sum of the Current Sense Amplifier output
and the Slope Compensation signal does not
exceed the EA output for a whole cycle, then
the falling edge of the CLK resets the Flip-Flop.
The output of the Error Amplifier integrates the
voltage difference between the feedback and
the 0.198V reference. The polarity is a FB pin
voltage lower than 0.198V increases the EA
output voltage. Since the EA output voltage is
proportional to the peak inductor current, an
increase in its voltage also increases the
current delivered to the output.
Open LED Protection
If the LED is open, there is no voltage on the
FB pin. The duty cycle will increase until
V(VDD)-V(VSS) reaches 55V or OVP-VSS
reaches the shutdown threshold set by the
external resistor divider. The top switch will turn
off till the voltage V(VDD)-V(VSS) and OVPVSS decreases sufficiently.
MP24183 Rev. 1.0
8/28/2008
Dimming Control
The MP24183 allows both DC and PWM
dimming. When the voltage on EN is less than
0.6V, the chip is turned off. For analog
dimming, when the voltage on EN is from 0.7V
to 1.4V, the LED current will change from 0% to
100% of the maximum LED current. If the
voltage on EN pin is higher than 1.4V,
maximum LED current will be generated. For
PWM dimming, its amplitude (VDIM – VINGND)
must exceed 1.4V. The PWM frequency is
recommended in range of 100Hz to 2kHz to get
a good dimming linearity.
Output Short Circuit Protection
The MP24183 integrates output short circuit
protection. When the output is shorted to VSS,
the voltage on OVP pin which detects the
output voltage gets smaller than 0.4V, and FB
pin senses no voltage (
