MP4008
High-Brightness, High-Current Accuracy
WLED Controller
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MP4008 is a current-mode controller
designed for driving high brightness light
emitting diodes (LEDs) with a wide input
voltage from 9V to 28V. It can be used in boost
and SEPIC topologies.
The MP4008 drives an external MOSFET with a
fixed frequency architecture to regulate the LED
current, which is measured through an external
current-sense resistor. The LED current
feedback voltage is 280mV. The switching
frequency is fixed to 180kHz. The cycle-bycycle current limit can be programmed by the
sense resistor on CS.
The MP4008 employs fast PWM dimming to the
LED current with a high dimming ratio.
Integrated protection features include undervoltage lockout, over-voltage protection, overcurrent protection, short LED protection, short
output
protection,
short
inductor/diode
protection, and OTP.
The MP4008 is available in a SOIC-8 package.
Constant Current WLED Driver
280mV Feedback Voltage with ±1.8%
Accuracy
9V to 28V Input Voltage
Leading Edge Blanking for Current Sense
Frequency Fixed to 180kHz
Fast PWM Dimming
Soft Start
Over-Voltage Protection
Short LED Protection
Short Output Protection
Over-Current Protection
Short Inductor/Diode Protection
VIN UVLO
Thermal Shutdown
Available in a SOIC-8 Package
APPLICATIONS
LCD Backlighting
DC/DC LED Driver
General Illumination
Industrial Lighting
Automotive/ Decorative LED Lighting
All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For
MPS green status, please visit the MPS website under Quality Assurance.
“MPS” and “The Future of Analog IC Technology” are registered trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
ORDERING INFORMATION
Part Number*
Package
Top Marking
MP4008GS
SOIC-8
See Below
* For Tape & Reel, add suffix –Z (e.g. MP4008GS–Z)
TOP MARKING
MP4008: Part number
LLLLLLLL: Lot number
MPS: MPS Prefix
Y: Year code
WW: Week code
PACKAGE REFERENCE
TOP VIEW
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
ABSOLUTE MAXIMUM RATINGS (1)
VIN……............................................... -0.3V to 30V
VGATE...................................................-0.3V to 19V
All other pins.....................................-0.3V to 6.5V
Junction temperature………………………..150C
Lead temperature……………………………260C
(2)
Continuous power dissipation (TA = +25°C)
SOIC-8...………..……………………..……….1.3W
Recommended Operating Conditions
(3)
IN supply voltage (VIN) ……………………………….9V to 28V
Operating junction temp. TJ…….-40C to +125C
MP4008 Rev. 1.01
12/8/2016
Thermal Resistance
(4)
θJA
θJC
SOIC-8………………………….96 ...... 45... C/W
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 produce an excessive die temperature,
causing the regulator to go into thermal shutdown. Internal
thermal shutdown circuitry protects the device from
permanent damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
ELECTRICAL CHARACTERISTICS
VIN = 24V, TA = +25C, unless otherwise noted.
Parameters
Symbol
Operating input voltage
VIN
Supply current (quiescent)
IQ
VIN under-voltage lockout
VIN under-voltage lockout hysteresis
VIN
UVLO
Condition
Min
9
VFB = 500mV
0.9
VIN rising
VIN_UVLO_HYS
Feedback
FB feedback voltage
VFB
FB input current
IFB
Typ
Max Units
28
V
1.1
1.3
mA
8.6
9
V
600
275
VFB = 280mV
280
-0.1
mV
285
mV
0.1
μA
Oscillator
Oscillator frequency
fOSC
Maximum duty cycle
DMAX
PWM Dimming
PWM low threshold
VPWMI-LO
VPMWI falling
PWM high threshold
VPWMI-HI
VPMWI rising
PWM pull-down resistance
90
180
kHz
96
%
0.8
1.5
RPWM
V
V
1
MΩ
GATE
GATE high threshold
VGATE
12
GATE output rise time
TRISE
CGATE = 1nF, VIN = 12V
40
ns
GATE output fall time
TFALL
CGATE = 1nF, VIN = 12V
40
ns
Current Sense
Current limit value
VCL
Duty = 0
OCP detect voltage
VOCP
Over-current protection
Leading edge blanking time
435
13
485
13.8
535
485
V
mV
mV
TBLANK
100
200
300
ns
Transconductance of error amplifier
GEA
380
440
500
μA/V
Maximum sourcing/sinking current
IEA
Soft-start current
Time for COMP saturated protection
detection
ISS
Compensation
MP4008 Rev. 1.01
12/8/2016
TCOMP
80
VFB < 0.8*REF
15
21
2048
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μA
27
μA
cycle
4
MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 24V, TA = +25C, unless otherwise noted.
Parameters
Protection
Symbol
OVP threshold
VOVP-TH
OVP threshold hysteresis
VOVP-HYS
SCP protection threshold
VOVP_SCP
Condition
time
Thermal shutdown (5)
for
short-circuit
TOFF
Typ
Max Units
2.6
2.75
2.9
410
FB short protection threshold
Propagation
detection
Min
FB = 620mV
V
mV
210
280
350
mV
0.54
0.58
0.62
V
1
μs
150
°C
NOTE:
5) Guaranteed by design.
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
PIN FUNCTIONS
Pin
Number
Name
1
VIN
2
GND
3
CS
4
GATE
5
PWM
6
COMP
7
FB
8
OVP
MP4008 Rev. 1.01
12/8/2016
Pin Function
Input supply, 9V-28V. VIN is the input of the internal linear regulator. VIN must be
bypassed locally.
Ground.
Switch current sense input. CS is used to sense the current of the external power
FET. It integrates a built-in blanking time to avoid switching noise interruption.
External MOSFET gate driver.
PWM dimming input. Apply a PWM signal on PWM for brightness control. GATE is
disabled when the PWM signal is low. GATE is enabled when the PWM signal is high.
Compensation. COMP is used to compensate the regulation control loop. Connect a
capacitor or a series RC network from COMP to GND. Also, COMP is used for soft
start. When the IC starts up, the current of the internal error amplifier is limited until the
output current reaches 80% of the setting current.
Feedback input, a 280mV internal feedback voltage. Connect a current sense
resistor from FB to GND. If the FB voltage is higher than 580mV for 1µs, short-load
protection is triggered, and the IC latches off.
Over-voltage protection input. Connect a resistor divider from the output to OVP to
program the OVP threshold. When the OVP voltage reaches the high threshold, the
over-voltage protection is triggered. The IC recovers once OVP decreases to the low
threshold.
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
TYPICAL CHARACTERISTICS
VIN = 24V, TA = 25°C, unless otherwise noted.
MP4008 Rev. 1.01
12/8/2016
www.MonolithicPower.com
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, PVIN = 20V, VLED = 70V, ILED = 350mA, L = 100μH, TA = 25°C, unless otherwise noted.
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, PVIN = 20V, VLED = 70V, ILED = 350mA, L = 100μH, TA = 25°C, unless otherwise noted.
VSW
50V/div.
VSW
50V/div.
VSW
50V/div.
PVIN
20V/div.
VCOMP
1V/div.
VCOMP
1V/div.
VOUT
50V/div.
IL
2A/div.
VOUT
50V/div.
IL
2A/div.
VOUT
50V/div.
IL
2A/div.
VSW
50V/div.
VSW
50V/div.
VSW
50V/div.
VPWM
5V/div.
VCOMP
1V/div.
VCOMP
2V/div.
VOUT
50V/div.
VOUT
50V/div.
IL
2A/div.
VOUT
50V/div.
VSW
50V/div.
VSW
50V/div.
VSW
50V/div.
VCOMP
2V/div.
VCOMP
2V/div.
VCOMP
2V/div.
VOUT
50V/div.
VOUT
50V/div.
VOUT
50V/div.
ISHORT
5A/div.
ISHORT
10A/div.
ISHORT
500mA/div.
ILED
200mA/div.
MP4008 Rev. 1.01
12/8/2016
ISHORT
5A/div.
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, PVIN = 20V, VLED = 70V, ILED = 350mA, L = 100μH, TA = 25°C, unless otherwise noted.
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
OPERATION
The MP4008 drives an external MOSFET with
current mode architecture to regulate the LED
current, which is measured through an external
current sense resistor.
The slope compensation is integrated to avoid
sub-harmonic resonance when the duty cycle is
greater than 0.5. The cycle-by-cycle current limit
can be programmed by the sense resistor on CS.
The MP4008 employs a special circuit for
regulating the internal power supply, which
covers a wide input voltage from 9V to 28V. The
switching frequency is fixed at 180 kHz.
The MP4008 integrates under-voltage lockout,
over-voltage protection, over-current protection,
short LED protection, short-circuit protection,
short inductor/diode protection, and OTP.
Figure 1: Functional Block Diagram
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
Soft Start
The MP4008 implements a soft start by limiting
the current capability of the internal error
amplifier during start-up. The COMP voltage
jumps to its clamp voltage (~0.3V) at the
beginning of start-up. The sourcing/sinking
current of the internal error amplifier is limited to
21µA until the FB voltage reaches 0.8 of the
internal reference voltage during start-up (see
Figure 2).
Figure 3: Dimming Signal Filtered from GATE
Protection
The MP4008 includes under-voltage lockout,
over-voltage protection, short-load protection,
short-circuit protection, over-current protection,
and short inductor/diode protection. If fault
conditions are detected, GATE and COMP are
pulled down.
A. Under-Voltage Lockout
The MP4008 integrates VIN UVLO. The internal
circuit does not work until the VIN voltage
reaches the UVLO rising threshold. The
hysteresis of VIN UVLO is 600mV.
B. Over-Voltage Protection
Figure 2: Soft-Start Process
PWM Dimming
PWM dimming is achieved by applying a PWM
signal on the PWM pin.
Over-voltage protection is detected by the
voltage of OVP. When the OVP voltage rises to
its high threshold, the over-voltage protection is
triggered, and GATE and COMP are pulled low.
The IC recovers once the OVP voltage
decreases to its low threshold.
When the PWM signal is high, GATE is enabled,
and the external dimming MOSFET is turned on
by the driving signal, which is filtered from GATE
(see Figure 3). The output of the internal error
amplifier is connected to the external
compensation network, and the LED current is
regulated accurately.
C. Short-Load Protection
When the PWM signal goes low, the GATE
signal is disabled. Meanwhile, the output of the
internal error amplifier is disconnected from the
compensation network, and the COMP voltage is
held by the external capacitor. The dimming
MOSFET turns off to prevent the output voltage
from being discharged.
D. Short-Circuit Protection
The internal oscillator is synchronized by the
PWM dimming signal to achieve good
performance with a small dimming ratio.
MP4008 Rev. 1.01
12/8/2016
In a short-load condition, a large short current is
detected by the FB sense resistor. If the FB
sensed voltage is higher than 580mV and lasts
for 1µs, the short-load protection is triggered;
GATE and COMP are pulled low, and the IC
latches off.
In a short-circuit condition, the output voltage is
pulled low and no current is sensed on FB. If the
following conditions are satisfied, OVP < 280mV,
FB < 0.3*REF, and COMP > 1V, the short-circuit
protection is triggered. GATE and COMP are
pulled low, and the IC latches off.
Figure 4 shows the circuit for short-circuit
protection. It uses a PMOS for both PWM
dimming and short-circuit protection. When LED+
is shorted to GND, GATE pulls low, and the
PMOS turns off to cut off the short loop.
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
Figure 4: Short-Circuit Protection Scheme
E. Over-Current Protection (Short Inductor/
Diode Protection)
The MP4008 implements a cycle-by-cycle current
limit function for protection. In normal operation,
the over-current protection is recoverable.
In unexpected cases (inductor or diode shorts),
when the voltage of CS, which is detected by an
external CS sense resistor, hits the latch-off
current limit value within the 300ns turn-on time
for 7 consecutive cycles, the over-current
protection is triggered; GATE and COMP are
pulled low, and the IC latches off.
F. LED- to GND Short Protection
In an LED- to GND short condition, the FB
senses no current which causes the COMP to
charge to its saturated value. If COMP remains
saturated for 2048 switching cycles, and FB is
below 30% of the internal reference, protection is
triggered; GATE and COMP are pulled low, and
the IC latches off.
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
APPLICATION INFORMATION
LED Current Setting
The LED current is set by the LED current sense
resistor (RFB). See Equation (1):
RFB
280mV
ILED
VIN (VO VIN)
V O I L fS
(2)
Where, Δ IL is the peak-to-peak current of the
inductor current. Design theΔIL to be 30% to 60%
of the inductor average current. See Equation (3):
IL_AVG=
VO ILED
VIN
(3)
Ensure the inductor saturated current is greater
than the inductor peak current. See Equation (4):
1
IL_PK=IL_AVG+ IL
2
(4)
Current Sense Resistor Setting
The cycle-by-cycle current limit and slope
compensation are both integrated. The current
limit value is programmed by the external CS
resistor, which connects from CS to GND. The
maximum value of the CS sense resistor can be
set using Equation (5):
0.435-0.27 D
RCS1( )
IL_pk
(5)
Where, D is the duty cycle of the GATE signal in
CCM. See Equation (6):
D 1
VIN
VO
(6)
IL_PK is the peak current of the inductor.
The slope compensation is integrated to avoid
sub-harmonic resonance when the duty is larger
than 0.5 in CCM. Equation (7) must be satisfied:
RCS2() 9.7 10-2
MP4008 Rev. 1.01
12/8/2016
VL(V) VO max VIN min
(1)
Selecting the Inductor
Select an inductor that allows the circuit to work
in continuous conduction mode (CCM). See
Equation (2):
L=
Where, VL is the voltage across the inductor when
GATE is off. See Equation (8):
L(H)
VL(V)
(8)
The CS resistance must be less than RCS1 and RCS2.
Over-Voltage Protection Setting
Choose a voltage divider (R1 and R2 in typical
application) to set the over-voltage protection
threshold. See Equation (9):
VOVP 2.75V
R1 R2
R2
(9)
Set the OVP point 10%-20% higher than the
maximum output voltage in normal operation.
Selecting the MOSFET and Diode
There are two MOSFETs for MP4008 application:
One is for the boost converter (the power
MOSFET), and the other is for PWM dimming
(the dimming MOSFET).
Choose a power MOSFET with breakdown
voltage at least 20% higher than the OVP point to
ensure safety in all conditions.
The RMS current of the MOSFET can be
calculated using Equation (10):
IRMS= D (IL _ AVG2
1
IL2 )
12
(10)
Where, D is the duty cycle.
Choose a dimming MOSFET with a voltage
rating 20% higher than the OVP point, and a
current rating about 3-5 of the LED current.
Choose a diode with a voltage rating greater than
the OVP point (at least 20% higher), and a
current rating greater than the LED current.
Selecting the Input Capacitor
The input capacitor reduces the surge current
drawn from the input supply and the switching
noise from the device. Use a ceramic capacitor
with an X7R dielectric, low ESR, and small
temperature coefficient.
(7)
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
Select a capacitor to limit the input voltage
ripple( Δ VIN) to less than 5% to 10% of its DC
value. See Equation (11):
IL
CIN
8 VIN fs
(11)
Selecting the Output Capacitor
The output capacitor limits the output voltage
ripple Δ VO (normally less than 1% to 5% of its
DC value) and ensures feedback loop stability.
See Equation (12):
COUT
ILED (VO VIN)
V O f s V O
(12)
Compensation Network Setting
The MP4008 implements peak-current-mode
control to regulate the LED current through a
compensation network on COMP. Usually, an
RCC network is adopted for most applications
(see Figure 5).
The zero of the compensation network is calculated
using Equation (15):
fZ_EA=
1
2 CZ RCOMP
(15)
The pole of this compensation network is
calculated using Equation (16):
fP_EA=
1
2 CP RCOMP
(16)
The power stage of the boost converter is
calculated using Equation (17):
1
fP_PS=
2 (
VO
//(RLED _ AC RFB )) COUT
ILED
(17)
Where, VO is the output voltage, ILED is the LED
current, and COUT is the output capacitance.
The right-half-plane (RHP) zero of the boost
converter stage is calculated using Equation (18):
VO
ILED
2 L
(1-D)2
fRHP_Z=
(18)
Choose a cross frequency (fc) below 1/5 of fRHP_Z to
get the RCOMP value. See Equation (19):
RCOMP=
RLED_AC+RFB fc COUT 2
RFB
GEA (1 D) GCS
(19)
Where, GCS is the conductance of the CS circuit.
The zero of the compensation network is used to
compensate the power-stage pole. See Equation
(20):
Figure 5: Compensation Network
The transfer function of the compensation
network is calculated using Equation (13).
Assume CZ>>CP.
EA(s)
GEA RFB
1
1 s CZ RCOMP
RFB+RLED_AC s CZ 1 s CP RCOMP
(13)
Where, GEA is the transconductance of the internal
error amplifier (GEA = 440µA/V), and RLED_AC is the
dynamic resistor of the LED load. RLED_AC is
calculated using Equation (14):
RLED_AC=
MP4008 Rev. 1.01
12/8/2016
VLED
ILED
CZ=
1
2 fPS _ P RCOMP
(20)
The pole of the compensation network is used to
compensate the RHP zero. See Equation (21):
CP=
1
2 fRHP _ Z RCOMP
(21)
(14)
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
TYPICAL APPLICATION CIRCUIT
Figure 6: Boost Application
Figure 7: SEPIC Application
MP4008 Rev. 1.01
12/8/2016
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MP4008─ HIGH-BRIGHTNESS, HIGH-CURRENT ACCURACY WLED CONTROLLER
PACKAGE INFORMATION
SOIC-8
NOTICE: The information in this document is subject to change without notice. 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.
MP4008 Rev. 1.01
12/8/2016
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