MP3398AGS [MPS]
Step up, 4 strings, Max. 350mA/string Analog and PWM dimming, White LED Controller;
| 型号： | MP3398AGS |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Step up, 4 strings, Max. 350mA/string Analog and PWM dimming, White LED Controller |
| 文件： | 总20页 (文件大小：1022K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MP3398A
Step up, 4 strings, Max. 350mA/string
Analog and PWM dimming, White LED Controller
DESCRIPTION
FEATURES
The MP3398A is a step-up controller with 4
current channels, which is designed to drive
WLED arrays for large-size LCD-panel
backlighting applications. It is flexible to expand
the number of LED channels by two or more
ICs in parallel sharing a single inductive power
source.
4-String, Max 350mA/String WLED Driver
5V to 28V Input Voltage Range
2.5% Current Matching Accuracy Between
Strings
Programmable Switching Frequency
PWM and Analog Dimming Mode
Cascading Capability with a Single Power
Source
The MP3398A uses peak-current mode with
fixed switching frequency. The frequency is
programmable by an external setting resistor.
The MP3398A drives an external MOSFET to
boost up the output voltage from a 5V to 28V
input supply. It regulates the current in each
LED string to the value set by an external
current-setting resistor.
LED Open and Short LED Protection
Programmable Over-Voltage Protection
Recoverable Thermal Shutdown Protection
Over Current Protection
Inductor/Diode short Protection
Under-Voltage Lockout
SOIC16, TSSOP16-EP and SOIC20
Packages
The MP3398A applies 4 internal current
sources for current balance. The current
matching can achieve 2.5% regulation accuracy
between strings. Its low regulation voltage on
LED current sources reduces power loss.
APPLICATIONS
Desktop LCD Flat Panel Displays
Flat Panel Video Displays
2D/3D LCD TVs and Monitors
The MP3398A can support both analog and
PWM dimming independently to meet the
different dimming-mode request. In addition,
rich protection modes are also integrated
including OCP, OTP, UVP, OVP, LED
short/open protection, inductor/diode short
protection.
All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For
MPS green status, please visit MPS website under Quality Assurance.
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks
of Monolithic Power Systems, Inc.
The MP3398A is available in SOIC16,
TSSOP16-EP and SOIC20 packages.
TYPICAL APPLICATION
MP3398A Rev. 1.04
5/26/2017
www.MonolithicPower.com
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© 2017 MPS. All Rights Reserved.
1
STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
ORDERING INFORMATION
Part Number
Package
Top Marking
MP3398AGS*
MP3398AGF**
MP3398AGY***
SOIC16
TSSOP16-EP
SOIC20
See Below
See Below
See Below
* For Tape & Reel, add suffix –Z (e.g. MP3398AGS–Z);
** For Tape & Reel, add suffix –Z (e.g. MP3398AGF–Z);
*** For Tape & Reel, add suffix –Z (e.g. MP3398AGY–Z);
TOP MARKING (MP3398AGS)
MPS: MPS prefix:
YY: year code;
WW: week code:
MP3398A: part number;
LLLLLLLLL: lot number;
TOP MARKING (MP3398AGF)
MPS: MPS prefix:
YY: year code;
WW: week code:
MP3398A: part number;
LLLLLL: lot number;
TOP MARKING (MP3398AGY)
MPS: MPS prefix:
YY: year code;
WW: week code:
MP3398A: part number;
LLLLLLLLL: lot number;
MP3398A Rev. 1.04
5/26/2017
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2017 MPS. All Rights Reserved.
2
STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
PACKAGE REFERENCE
TOP VIEW
TOP VIEW
1
2
3
4
16
15
14
13
COMP
VCC
1
16
COMP
EN
VCC
VIN
EN
PWM
GND
OSC
VIN
2
3
4
15
14
13
GATE
ISENSE
PWM
GND
OSC
GATE
ISENSE
OVP
Exposed Pad
Connect to GND
5
6
12
11
VP
O
5
6
12
11
ISET
ADIM
LED4
LED1
LED2
LED3
LED1
LED2
LED3
ISET
ADIM
7
8
10
9
7
8
10
9
LED4
SOIC16
TSSOP16-EP
SOIC20
ABSOLUTE MAXIMUM RATINGS (1)
VIN .............................................. -0.3V to +30V
VGATE........................................... -0.3V to +6.5V
VCC............................................ -0.3V to +6.8V
VLED1 to VLED4 .................................. -1V to +55V
VISENSE......................................... -0.5V to +6.5V
All Other Pins............................... –0.3V to VCC
Thermal Resistance (4)
SOIC16……………………………80……35....°C/W
θJA θJC
TSSOP16-EP……………………45…….10….°C/W
SOIC20
……………………72...... 30... C/W
Notes:
1) Exceeding these ratings may damage the device. The voltage
is measured with a 20MHz bandwidth limited oscilloscope.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-to-
ambient 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.
(2)
Continuous Power Dissipation (TA = 25°C)
SOIC16....................................................1.56W
TSSOP16-EP………………………………2.78W
SOIC20 ………………………………… 1.74W
Junction Temperature..............................150°C
Lead Temperature ...................................260°C
ESD Capability Human Body Mode (all pins)
.................................................................3.5kV
3) The device is not guaranteed to function outside of its
operating conditions.
Recommended Operating Conditions (3)
Supply Voltage VIN ............................. 5V to 28V
LED Current (Backlight) ...........10mA to 350mA
Operating Junction Temp. (TJ). -40°C to +125°C
4) Measured on JESD51-7, 4-layer PCB.
MP3398A Rev. 1.04
5/26/2017
www.MonolithicPower.com
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
ELECTRICAL CHARACTERISTICS (5)
VIN =12V, VEN = 5V, TA = 25°C, unless otherwise noted.
Parameters
Symbol Condition
Min
5
Typ
Max
28
Units
V
Operating Input Voltage
Supply Current (Quiescent)
VIN
VIN=12V, VEN=5V, no load
without switching
VIN=12V, VEN=5V, no load
with switching
IQ
IOP
IST
1.2
1.35
3
1,5
mA
Supply Current (Operation)
Supply Current (Shutdown)
LDO Output Voltage
5.5
0.5
mA
μA
V
VEN=0V, VIN=12V
0.01
6
VEN=5V, 7V<VIN<28V,
0<IVCC<10mA
VCC
5.4
3.6
6.6
4.4
VCC UVLO Threshold
VCC UVLO Hysteresis
EN High Voltage
VIN_UVLO Rising Edge
4
V
mV
V
200
VEN_HIGH VEN Rising
1.8
EN Low Voltage
VEN_LOW
VEN Falling
0.6
V
STEP-UP CONVERTER
Gate Driver Impedance
(Sourcing)
Gate Driver Impedance
(Sinking)
VCC=6V,VGATE=6V
4.5
2.5
7
5
Ω
Ω
VCC=6V,IGATE=10mA
ROSC= 115kΩ
ROSC= 374kΩ
459
150
1.20
540
180
1.23
93
621
210
1.26
kHz
kHz
V
Switching Frequency
fSW
OSC Voltage
VOSC
DMAX
Maximum Duty Cycle
%
Cycle By Cycle ISENSE
Current Limit
Max Duty Cycle
145
180
230
mV
COMP Source Current Limit
COMP Sink Current Limit
COMP Trans-conductance
CURRENT DIMMING
ICOMP SOLI 1V<COMP<1.9V
ICOMP SILI 1V<COMP<1.9V
70
17
μA
μA
GCOMP
ΔICOMP=±10μA
400
μA/V
PWM Input Low Threshold
PWM Input High Threshold
VPWM_LO VPWM Falling
0.75
V
V
VPWM_HI
Adim_L
VPWM Rising
RISET=9.72k
1.25
0.44
Analog Dimming Input Low
Threshold
Analog Dimming Input High
Threshold
0.38
1.44
0.41
1.49
V
V
Adim_H
1.54
LED CURRENT REGULATION
ISET Voltage
VISET
ILED
1.195
31.3
1.22
32.3
1.245
33.3
V
mA
%
LEDX Average Current
Current Matching (5)
RISET=30.5kΩ
ILED=33.2mA
2.5
VCC Max Current Limit
LED FET Resistance
Icc_Limit
R_LED
50
75
1.7
100
mA
Ω
ILED=10mA
MP3398A Rev. 1.04
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5/26/2017
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© 2017 MPS. All Rights Reserved.
STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN =12V, VEN = 5V, TA = 25°C, unless otherwise noted.
Parameters
Symbol
Condition
ILED=330mA
ILED=60mA
Min
Typ
800
285
Max Units
mV
mV
LEDX Regulation Voltage
PROTECTION
VLEDX
OVP(Over Voltage Protection)
Threshold
OVP(Over Voltage Protection)
Threshold HYS
VOVP_OV
Rising Edge
1.20
1.23 1.26
80
V
HYS
mV
VOVP_HYS
OVP UVLO threshold
VOVP_UV
VLEDX_UV
Step-up Converter Fails
30
75
120
280
mV
mV
LEDX UVLO Threshold
120
200
LEDX Over Voltage Threshold
VLEDX_OV
5.8
6.3
6.8
V
LED Short Fault Cycles
T_LED_OV
4096
Latch-Off Current Limit
Thermal Protection Threshold
Thermal Protection Hysteresis
Notes:
VLMT
TST
560
640
150
25
720
mV
°C
°C
5) Matching is defined as the difference of the maximum to minimum current divided by 2 times average currents.
MP3398A Rev. 1.04
5/26/2017
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
TYPICAL CHARACTERISTICS
MP3398A Rev. 1.04
5/26/2017
www.MonolithicPower.com
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 30V, L = 33µH, ILED=120mA/String, 4 strings, TA = 25°C, unless otherwise noted.
MP3398A Rev. 1.04
5/26/2017
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, VOUT = 30V, L = 33µH, TA = 25°C, unless otherwise noted.
MP3398A Rev. 1.04
5/26/2017
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
PIN FUNCTIONS
TSSOP16-EP
&SOIC16
Pin #
SOIC20
Pin #
Name Description
Step-up Converter Compensation Pin. This pin compensates the regulation
control loop. Connect a ceramic capacitor from COMP to GND.
1
2
1
2
COMP
EN
Enable Control Input. A voltage greater than 1.8V will turn the part on and less
than 0.6 V will turn the part off. Do not let this pin float.
Input Signal for PWM Brightness Control. By applying a PWM signal on this
pin, the LED current can be chopped and the average current is equal to
Iset*D_dim (I_set is the LED current value set by a resistor connected to PIN
6; D_dim is the duty cycle of the PWM dimming duty cycle). Make sure the
PWM amplitude voltage level > VPWM_HI and the low level voltage < VPWM_HI
.
The input PWM signal frequency mainly determines the LED current dimming
ratio. Lower dimming frequency, smaller dimming current can be gotten. In
general, 200Hz to 2kHz can be used to cover most of the customers’ LED
current dimming requests. Internally weakly pulled to GND if this pin is floated.
If PWM dimming is not required, pulling this pin to high
voltage(1.25V<Vpwm<5V),
3
3
PWM
4
5
5
7
GND Ground.
Switching Frequency Set. Connect a resistor between OSC and GND to set
the step-up converter switching frequency. The voltage at this pin is regulated
OSC
to 1.23V. The clock frequency is proportional to the current sourced from this
pin.
LED Current Set. Tie a current-setting resistor from this pin to ground to
program the current in each LED string. This pin voltage is regulated to
1.225V. The LED current is proportional to the current through the ISET
resistor.
6
7
8
9
ISET
Signal Input for Analog Brightness Control. The LED current amplitude is
determined by this pin and the input signal can be either a PWM signal or a
DC voltage signal. An internal RC filter (10Mohm resistor and 100pF
capacitor) is integrated to this pin. So, if a PWM signal applied to this
pin, >20kHz frequency is recommended to get a better PWM signal filtering
performance and make sure the amplitude voltage is higher than 1.5V and low
level voltage is less than 0.4V. For DC signal input, please apply a DC input
signal range from 0.4V to 1.5V to linearly set the LED current from 0% to
100%. Internally weakly pulled to GND if this pin is floated. If Analog dimming
is not required, pulling this pin to high voltage(1.54V<Vpwm<5V),
ADIM
LED String 4 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 4 cathode to this pin.
8
9
10
11
12
13
LED4
LED3
LED2
LED1
LED String 3 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 3 cathode to this pin.
LED String 2 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 2 cathode to this pin.
10
11
LED String 1 Current Input. This pin is the open-drain output of an internal
dimming control switch. Connect the LED String 1 cathode to this pin.
Over-Voltage Protection Input. Connect a resistor divider from output to this
12
14
OVP pin to program the OVP threshold. When this pin voltage reaches 1.23V, the
MP3398A triggers Over Voltage Protection mode.
MP3398A Rev. 1.04
5/26/2017
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
PIN FUNCTIONS (continued)
TSSOP16-EP
&SOIC16
Pin #
SOIC20
Pin #
Name Description
Current Sense Input. During normal operation, this pin senses the
voltage across the external-inductor current-sensing resistor (RSENSE
)
13
17
ISENSE for peak-current–mode control and also to limit the inductor current
during every switching cycle. If this pin is not used for cascading
applications, tie this pin to GND; do not let this pin float.
Step-up Converter Power Switch Gate Output. This pin drives the external
power N-MOS device.
14
15
18
19
GATE
Supply Input. VIN supplies the power to the chip, as well as the step-up
converter switch. Drive VIN with a 5V to 28V power source. Must be locally
bypassed.
VIN
The Internal 6V Linear Regulator Output. VCC provides power supply for the
external MOSFET switch gate driver and the internal control circuitry. Bypass
VCC to GND with a ceramic capacitor.
16
20
VCC
NC
4, 6,
15, 16
No Connect.
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
BLOCK DIAGRAM
VCC
Regulator
VIN
GND
-
Control
Logic
GATE
+
PWM
Comparator
Current Sense
Amplifier
200ns
Blank Time
ISENSE
OVP
+
-
OV
Comparator
+
-
Oscillator
OSC
1.23V
100ns
Blanking
+
-
ILIMIT
PWM
STOP
+
-
UP_CLAMP
6.3V
-
Short String
Protection
+
Max
Min
Feedback
Control
-
EA
COMP
EN
+
Ref
Enable
Control
LED1
+
1.225V
-
ISET
Current Control
ADIM
PWM
LED4
Figure 1—Functional Block Diagram
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
OPERATION
reaches the output voltage of the error amplifier
(VCOMP) the external MOSFET turns off.
The MP3398A is a step-up converter with peak-
current mode. It employs 4 channels of current
sources to drive up to 4 strings of white LEDs.
The output voltage of the internal error amplifier
is an amplified signal of the difference between
the reference voltage and the feedback voltage.
The converter automatically chooses the lowest
active LEDX pin voltage to provide a high-
enough bus voltage to power all the LED arrays.
Internal 6V Regulator
The MP3398A includes an internal linear
regulator (VCC). When VIN is greater than 6.5V,
this regulator outputs a 6V power supply to the
external MOSFET switch gate driver and the
internal control circuitry. The VCC voltage drops
to 0V when the chip shuts down. The MP3398A
features under-voltage lockout (UVLO). The
chip is disabled until VCC exceeds the UVLO
If the feedback voltage drops below the
reference, the output of the error amplifier
increases. This results in more current flowing
through the MOSFET, thus increasing the
power delivered to the output. This forms a
closed loop that regulates the output voltage.
threshold.
The
UVLO
hysteresis
is
approximately 200mV.
Under light-load operation, especially in the
case of VOUT ≈ VIN, the converter runs in
pulse-skipping mode where the MOSFET turns
on for a minimum on-time of approximately
200ns, and then the converter discharges the
power to the output for the remaining period.
The external MOSFET remains off until the
output voltage needs to be boosted again.
System Startup
When enabled, the MP3398A checks the
topology connection first. The chip monitors the
over-voltage protection (OVP) pin to see if the
Schottky diode is not connected or if the boost
output is shorted to GND. An OVP voltage of
less than 75mV will disable the chip. The
MP3398A also checks other safety limits,
Dimming Control
including
UVLO
and
over-temperature
protection (OTP), over-current protection after
passing the OVP test. If all the protection tests
pass, the chip then starts boosting the step-up
converter with an internal soft-start.
The MP3398A provides two dimming methods:
PWM or analog dimming mode.
For PWM dimming, apply a PWM signal to
PWM pin. The LED current is chopped by this
PWM signal and the average LED current is
equal to Iset*D_dim where D_dim is the duty
cycle of PWM dimming signal and Iset is the
LED current amplitude.
It is recommended that the enable signal occurs
after the establishment of the input voltage and
PWM dimming signal during the start-up
sequence to avoid large inrush current.
Step-Up Converter
For analog dimming, either a PWM signal or DC
signal can be applied to ADIM pin.
The
converter
operating
frequency
is
programmable (from 100kHz to 500kHz) with a
external resistor connected to the OSC pin.
This helps to optimize the size of external
components and the efficiency.
When a PWM signal is applied to ADIM pin, this
signal will be filtered by the internal RC filter.
The LED current amplitude is equal to
Iset*D_Dim where D_dim is the duty cycle of
PWM dimming signal and Iset is the LED
current amplitude. 20kHz or higher PWM signal
is recommended to get the better filtering
performance.
At the beginning of each switching cycle, the
internal clock turns on the external MOSFET (In
normal operation, the minimum turn on time is
200ns). A stabilizing ramp added to the output
of the current sense amplifier prevents sub-
harmonic oscillations for duty cycles greater
than 50 percent. This result is fed into the PWM
comparator. When this resulting voltage
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
When a DC signal is applied to ADIM pin, the
voltage range in 0.4V to 1.5V directly sets the
LED current linearly from 0% to 100%.
marked LED strings shut off completely until the
part restarts. In order to prevent mis-triggering
short LED protection when open LED string or
sharp ADIM, the short LED protection function
is disabled when Vledx of all used LED
channels are higher than 1.5V.
Open String Protection
Open string protection is achieved through the
OVP pin and the LED(1 to 4) pins. If one or
more strings are open, the respective LEDX
pins are pulled to ground and the IC keeps
charging the output voltage until it reaches the
over-voltage protection (OVP) threshold. If the
OVP point has been triggered for >4us, the chip
stops switching and marks the strings which
have an LEDX pin voltage lower than 196mV.
Once marked, the remaining LED strings force
the output voltage back into tight regulation.
The string with the largest voltage drop
determines the output regulation.
Inductor/Diode short Protection
To prevent the IC and external MOSFET
damage when external inductor is shorted,
MP3398A has the protection mode in two
following methods. When inductor is shorted,
the output can not maintain enough energy to
load the LED and the output voltage will drop.
Thus, the COMP (the error amplifier output)
voltage tends to rise till be clamped high, when
it lasts longer than 512 switching cycles the IC
turns off and latches. In some cases that the
COMP voltage can not be clamped to high
when inductor is shorted, the IC also provides
the protection mode by detecting the current
flowing through power MOSFET. In this mode,
when the current sense voltage across sense
resistor (connected between MOSFET and
GND) hits VLMT limit value and lasts for 4
switching cycles, the IC turns off and latches.
The MP3398A will always attempt to light at
least one string. If all strings are open, the
MP3398A shuts down the step-up converter.
The strings will remain in this marked state until
the chip reset.
Short String Protection
The MP3398A monitors the LEDX pin voltages
to determine if a short string fault has occurred.
If one or more strings are shorted, the
respective LEDX pins tolerate high voltage
stress. If an LEDX pin voltage is higher than
6.3V, this condition triggers the detection of a
short string. When a short string faults (LEDX
over-voltage fault) keeps for 4096 switching
clocks, the fault string is marked OFF and
disabled. Once a string is marked OFF, it
disconnects from the output voltage loop. The
Thermal Shutdown Protection
To prevent the IC operate at exceedingly high
temperature, thermal shutdown is implemented
in this chip by detecting the silicon die
temperature. When the die temperature
exceeds the upper threshold TST, the IC
shutdowns and recovers to normal operation
when die temperature drops below lower
threshold. Typically, the hysteresis value is
25°C .
MP3398A Rev. 1.04
5/26/2017
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
APPLICATION INFORMATION
Selecting the Switching Frequency
Choose an inductor that does not saturate under
the worst-case load conditions. Select the
minimum inductor value to ensure that the boost
converter works in continuous conduction mode
with high efficiency and good EMI performance.
Calculate the required inductance value using the
equation:
The switching frequency of the step-up converter
is recommended from 100kHz to 500kHz for
most of application. An oscillator resistor on OSC
pin sets the internal oscillator frequency for the
step-up converter according to the below
equation:
η VOUT D(1D)2
L
67320
2 fSW ILOAD
FSW(kHz)
ROSC(k)
V
IN
For ROSC=374kΩ, the switching frequency is set
to 180kHz.
D 1
VOUT
Where VIN and VOUT are the input and output
voltages, fSW is the switching frequency, ILOAD is
the LED load current, and η is the efficiency.
Setting the LED Current
The LED each string current can be set through
the current setting resistor on the ISET pin.
The switching current is usually used for the peak
current mode control. In order to avoid hitting the
current limit, the voltage across the sensing
resistor RSENSE must measure less than 80% of
8101.22V
ILED(mA)
R
kΩ
ISET
the worst-case current-limit voltage, VSENSE
.
For RSET=8.2kΩ, the LED current is set to
120mA. Please do not leave ISET pin open.
0.8 VSENSE
RSENSE
Selecting the Input Capacitor
IL(PEAK)
The input capacitor reduces the surge current
drawn from the input supply and the switching
noise from the device. The input capacitor
impedance at the switching frequency should be
VOUT ILOAD V (VOUT V )
IN
IN
IL(PEAK)
ηV
2LF VOUT
IN
SW
Where IL(PEAK) is the peak value of the inductor
current. VSENSE is shown in Figure 2.
less than the input source impedance to prevent
the high-frequency switching current from
passing through to the input. Use ceramic
capacitors with X5R or X7R dielectrics for their
low ESR and small temperature coefficients. For
most applications, use a 4.7μF ceramic capacitor
in parallel with a 220µF electrolytic capacitor.
Selecting the Inductor and Current Sensing
Resistor
The MP3398A requires an inductor to supply a
higher output voltage while being driven by the
input voltage. A larger value inductor results in
less ripple current, resulting in lower peak
inductor current and reducing stress on the N-
channel MOSFET. However, the larger value
inductor has a larger physical size, higher series
resistance, and lower saturation current.
Figure 2—VSENSE vs Duty Cycle
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
Selecting the Power MOSFET
Where VTH is the threshold voltage, VPLT is the
plateau voltage, RG is the gate resistance, and
The MP3398A is capable of driving a wide variety
of N-channel power MOSFETS. The critical
parameters of selection of a MOSFET are:
VDS is the drain-source voltage. Please note that
calculating the switching loss is the most difficult
part in the loss estimation. The formula above
provides a simplified equation. For more accurate
estimates, the equation becomes much more
complex.
1. Maximum drain-to-source voltage, VDS(MAX)
2. Maximum current, ID(MAX)
3. On-resistance, RDS(ON)
4. Gate source charge QGS and gate drain
charge QGD
The total gate charge, QG, is used to calculate
the gate drive loss. The expression is
5. Total gate charge, QG
PDR QG VDR fSW
Ideally, the off-state voltage across the MOSFET
is equal to the output voltage. Considering the
voltage spike when it turns off, VDS(MAX) should be
greater than 1.5 times of the output voltage.
Where VDR is the drive voltage.
Selecting the Output Capacitor
The output capacitor keeps the output voltage
ripple small and ensures feedback loop stability.
The output capacitor impedance must be low at
the switching frequency. Ceramic capacitors with
X7R dielectrics are recommended for their low
ESR characteristics. For most applications, a
4.7μF ceramic capacitor in parallel with a 22μF
electrolytic capacitor will suffice.
The maximum current through the power
MOSFET occurs at the minimum input voltage
and the maximum output power. The maximum
RMS current through the MOSFET is given by
IRMS(MAX) IIN(MAX) DMAX , where:
VOUT V
IN(MIN)
DMAX
VOUT
Setting the Over Voltage Protection
The open string protection is achieved through
the detection of the voltage on the OVP pin. In
some cases, an LED string failure results in the
feedback voltage always zero. The part then
keeps boosting the output voltage higher and
higher. If the output voltage reaches the
programmed OVP threshold, the protection will
be triggered.
The current rating of the MOSFET should be
greater than 1.5xIRMS
The ON resistance of the MOSFET determines
the conduction loss, which is given by:
2
Pcond IRMS RDS (on) k
Where k is the temperature coefficient of the
MOSFET.
To ensure the chip functions properly, select the
resistor values for the OVP resistor divider to
provide an appropriate set voltage. The
recommended OVP point is about 1.1 to 1.2
times higher than the output voltage for normal
operation.
The switching loss is related to QGD and QGS1
which determine the commutation time. QGS1 is
the charge between the threshold voltage and
the plateau voltage when a driver charges the
gate, which can be read in the chart of VGS vs. QG
of the MOSFET datasheet. QGD is the charge
during the plateau voltage. These two
parameters are needed to estimate the turn-on
and turn-off losses.
RHIGH
VOVP 1.23(1
)
RLOW
Selecting Dimming Control Mode
The MP3398A provides two different dimming
methods.
QGS1 RG
PSW
VDS IIN fSW
VDS IIN fSW
1. Direct PWM Dimming
VDR VTH
QGD RG
VDR VPLT
An external PWM dimming signal is employed to
achieve PWM dimming control. Apply a PWM
dimming signal (in the range of 100Hz to 20kHz)
to the PWM pin. The minimum recommended
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
amplitude of the PWM signal is 1.5V and the low
level should be less than 0.4V.
MOSFET driving signals are not used; the boost
converter can be only driven by the master IC.
Do not leave the ISENSE pin of the slave IC floating;
tie it to ground. Apply the EN and DIM signals to
both ICs.
Table 1—The Range of PWM Dimming Duty
fPWM(Hz)
100<f200
200<f500
500<f1k
1k<f2k
2k<f5k
5k<f10k
10k<f20k
Dmin
Dmax
0.30%
0.75%
1.50%
3.00%
7.50%
15.00%
30.00%
100%
100%
100%
100%
100%
100%
100%
Layout Considerations
The circuit layout for the MP3398A requires
special attention to reduce EMI noise.
The loop from the external MOSFET (M1),
through the output diode (D1) and the output
capacitor (C2, C3) carry a high-frequency pulse
current and must be as small and short as
possible (See Figure 3).
2. Analog Dimming
For analog dimming, apply a PWM signal or a
DC voltage signal to ADIM pin. An internal RC
filter (10Mohm resistor and 100pF capacitor) is
integrated to this pin. So, if a PWM signal applied
to this pin, >20kHz frequency is recommended to
get a better PWM signal filtering performance
and make sure the amplitude voltage is higher
than 1.5V and low level voltage is less than 0.4V
with >15mV/ns slope rate for falling/rising edge.
For DC signal input, please apply a DC input
signal range from 0.4V to 1.5V to linearly set the
LED current from 0% to 100%.
Figure 3—Layout Consideration
All logic signals refer to the signal ground. in
order to reduce the noise affection, it is
recommend to separate the power ground(PGND)
and signal ground(GND), then connect PGND
and GND together.
Expanding LED Channels
The MP3398A can expand the number of LED
channels by using two or three MP3398A in
parallel. To connect two MP3398A for a total of 8
LED strings, tie the VCC pins of the master IC
and the slave IC together to power the slave IC
internal logic circuitry. Tie the COMP pins of the
slave IC and the master IC together to regulate
the voltage of all 8 strings LEDs. The slave IC
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
TYPICAL APPLICATION CIRCUITS
Figure 4: 4 string, 12 LED in series, 120mA/string application
(Some components are reasonably adjustable based on real case)
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
PACKAGE INFORMATION
SOIC16
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
TSSOP16-EP（with external thermal pad）
PIN 1 ID
TOP VIEW
RECOMMENDED LAND PATTERN
SEE DETAIL"A"
FRONT VIEW
SIDE VIEW
DETAIL "A"
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD
FLASH, PROTRUSION OR GATE BURR.
3) PACKAGE WITDH DOES NOT INCLUDE INTERLEAD
FLASH OR PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER
FORMING) SHALL BE 0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-153,
VARIATION ABT.
BOTTOM VIEW
6) DRAWING IS NOT TO SCALE.
MP3398A Rev. 1.04
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STEPUP, 4 STRINGS, MAX. 350MA/STRING ANALOG ANDPWM DIMMING, WHITELEDCONTROLLER
SOIC20
0.024
(0.61)
0.050
(1.27)
0.496(12.60)
0.512(13.00)
20
11
0.079
(2.00)
0.291
(7.40)
0.299
(7.60)
0.394
(10.00)
0.418
0.370
(9.40)
(10.60)
PIN 1 ID
1
10
TOP VIEW
RECOMMENDED LAND PATTERN
0.093(2.35)
0.104(2.65)
SEATING PLANE
0.009(0.23)
0.013(0.33)
0.013(0.33)
0.020(0.51)
0.050(1.27)
BSC
0.004(0.10)
0.012(0.30)
SEE DETAIL "A"
FRONT VIEW
SIDE VIEW
0.010(0.25)
0.030(0.75)
x 45o
NOTE:
1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN
BRACKET IS IN MILLIMETERS.
GAUGE PLANE
0.010(0.25) BSC
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSIONS OR GATE BURRS.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSIONS.
4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING)
SHALL BE0.10 MILLIMETERS MAX.
0.016(0.41)
0.050(1.27)
0o-8o
5) DRAWING CONFORMS TO JEDEC MS-013, VARIATION AC.
6) DRAWING IS NOT TO SCALE.
DETAIL "A"
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.
MP3398A Rev. 1.04
5/26/2017
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20
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