Datasheet - MAP3249 - MagnaChip Semiconductor
Confidential
Datasheet Version 1.2
4-channel LED Driver for High Brightness LEDs
Features
General Description
MAP3249 is a 4-channel LED driver optimized for
LED backlight application targeting mid and large size
LCD module. MAP3249 uses the boost MOSFET
externally and 4-channel current sources internally for
driving high brightness White LEDs.
MAP3249 has 55V absolute Max. rating FB pins and
input voltage is ranged from 8.5V ~ 28V and max LED
current is 200mA per channel.
MAP3249 features internal soft-start and ±2.5%
LED current accuracy including matching between
channels.
MAP3249 has various protections like output overvoltage, LED short/open, open schottky diode, UVLO
and thermal shutdown.
MAP3249 has an unused channel detection function
to not boost the output voltage to OVP at start-up.
MAP3249 is available 16 leads SOIC and E-TSSOP
with Halogen-free (fully RoHS compliant).
Applications
1
8.5V to 28V Input Voltage Range
Drive up to 4 Channels
55V FB Pin Voltage
0.4V Headroom Voltage
200mA Output Current per Channel
±2.5% Current Accuracy
Programmable Boost Switching Frequency
(100KHz ~ 500KHz)
LED Current Set by both
PWM and External DC Voltage
Unused Channel Detection
Boost Over Current Protection
Output Over Voltage Protection
LED Short / Open Protection
Schottky Diode Open Protection
UVLO
High Brightness white LED backlighting for LCD
TVs and monitors
General LED lighting applications
Ordering Information
Part Number
Top
Marking
Ambient
Temperature Range
Package
RoHS Status
MAP3249SIRH
MAP3249TERH
MAP3249
MAP3249
-40℃ to +85℃
-40℃ to +85℃
16Leads SOIC
16Leads E-TSSOP
Halogen Free
Halogen Free
Typical Application
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Datasheet - MAP3249
Confidential
Datasheet Version 1.2
SOIC/ETSSOP-16L
Functional Block Diagram
2
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Pin Configuration
Confidential
Datasheet Version 1.2
16leads
E-TSSOP
16leads
SOIC
Name
1
1
VLDO
Internal 5.2V Regulator Output. Need external capacitor to stabilize.
2
2
COMP
Internal error amplifier compensation (Note 1)
3
3
ADIM
Setting for LED current thru external DC voltage
4
4
ISET
Setting for LED current reference resistor (Note2)
5
5
EN
6
6
FSW
Setting for booster switching frequency (Note 3)
7
7
FB4
LED current sink for Ch4 (Note 4)
8
8
FB3
LED current sink for Ch3 (Note 4)
9
9
FB2
LED current sink for Ch2 (Note 4)
10
10
FB1
LED current sink for Ch1 (Note 4)
11
11
OVP
Output Over voltage sense (Note 5)
12
12
CS
13
13
GATE
Gate driver output for external boost MOSFET
14
14
PWM
PWM signal input for dimming (Note 7)
15
15
GND
Ground
16
16
VIN
Power supply input. Need external bypass capacitor.
Exposed
PAD
3
-
Description
Enable. Active High.
External boost current sense (Note 6)
Connect to GND by multiple vias for heat-sinking purpose (Note 8)
Note 1: Connect external capacitor and resistor to COMP pin. Refer to typical application diagram
Note 2: The resistor value on ISET pin controls the full scale level of sink current on FB- pins. Do not leave this pin open.
Note 3: Connect external resistor to set the oscillator frequency from 100kHz to 500kHz
Note 4: If not used, connect to GND.
Note 5:.Connect center node of resistive voltage divider from output to ground. Refer to a typical application diagram
Note 6: Connect external resistor to GND to sense the external power MOSFET drain current
Note 7: This external PWM signal is used for brightness control
Note 8: Not connected internally.
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Pin Description
Confidential
Datasheet Version 1.2
Symbol
VVIN
VEN, VCS, VVLDO ,VPWM, VCOMP, VOVP,
VGATE, VISET, VFSW, VADIM
VFB1~4
IFB1~4
TPAD
TJ
TS
ESD
Parameter
Supply Voltage
EN, CS, VLDO, PWM, COMP, OVP, GATE, ISET, FSW, ADIM
pins
FB1 ~ FB4 pins
FB1 ~ FB4 pins
Soldering Lead/ Pad Temperature 10sec
Junction Temperature
Storage Temperature
HBM on All Pins (Note 2)
MM on All Pins (Note 3)
Min
-0.3
Max
30
Unit
V
-0.3
6
V
-0.3
55
200
300
+150
+150
+2000
+200
V
mA
-40
-65
-2000
-200
°C
°C
°C
V
Note 1: Stresses beyond the above listed maximum ratings may damage the device permanently. Operating above the recommended
conditions for extended time may stress the device and affect device reliability. Also the device may not operate normally above the
recommended operating conditions. These are stress ratings only.
Note 2: ESD tested per JESD22A-114.
Note 3: ESD tested per JESD22A-115.
Recommended Operating Conditions (Note 1)
VVIN
IFB1~4
VFB1~4
TA
4
Parameter
Supply Input Voltage
LED Current Sink Pin
LED Current Sink Pin
Ambient Temperature (Note 2)
Min
8.5
90
-40
Max
28
200
55
+85
Unit
V
mA
V
°C
Note 1: Normal operation of the device is not guaranteed if operating the device over outside range of recommended conditions.
Note 2: The ambient temperature may have to be derated if used in high power dissipation and poor thermal resistance conditions.
Package Thermal Resistance (Note 1)
MAP3249SIRH
MAP3249TERH
Parameter
16 Leads SOIC
16 Leads E-TSSOP
Note 1: Multi-layer PCB based on JEDEC standard (JESD51-7)
th
Oct 8 2014
θJA
80
60
θJC
49
19
Unit
℃/W
℃/W
MAP3249 – 4-channel LED Driver for high brightness LEDs
Absolute Maximum Ratings(Note 1)
Confidential
Datasheet Version 1.2
Unless noted, VVIN = 12V, CVIN = 1.0µF, and typical values are tested at TA = 25°C.
Parameter
Test Condition
General Input Output
VVIN
Input Voltage Range
IQ
Quiescent Current
Driving FBs at Min. setting with no load
ISD
Ground Pin Current in
Shutdown
VVIN = 12V, VEN = 0V
No Load Current on FB
VEN
Logic Input Level on
EN pin
VEN_L : Logic Low
VEN_H : Logic High
REN
Pull-down resistor on EN pin
VUVLO
Under Voltage Lockout
Threshold Voltage on VIN pin
Stop threshold
Start threshold
Internal Oscillator
Frequency
RFSW=250 kΩ
RFSW=100 kΩ
Min
Typ
Max
Unit
4
28
10
V
mA
8.5
40
µA
0.8
2.2
250
500
6.5
7.5
V
kΩ
7.0
8.2
V
kHz
Oscillator
fSW
Dmax
Reference
VVLDO
Protection
LDO Voltage
VVIN ≥ 8.5V, 0mA ≤ ILDO ≤ 10mA
TSD
Thermal Shutdown
Temperature
VOVP
Over-Voltage Threshold
on OVP pin
Shutdown Temperature
Hysteresis, ΔTSD
Rising Over-Voltage Limit on OVP pin
Hysteresis, ΔVOVP
VLED_SHORT
tSCP
VCS
5
Max. Duty Cycle
VOPEN
LED Short Protection
Threshold on FB pins
LED Short Protection Time
Boost Over Current Protection
Threshold on CS pin
fSW=500kHz (Note 1, 2)
LED Open Protection
Threshold on FB pins
ILED=90mA
ILED=200mA
180
425
85
200
500
90
220
575
4.95
5.2
5.45
2.35
FB1 ~ FB4
SBD Open Protection
Threshold on OVP pin
LED Current Sink Regulator
VFB1~4
Min. FB1~FB4 Voltage
IFB_max
IFB_leakage
VADIM
Current Accuracy
Current Sink Max. Current
VADIM=2.0V
VPWM=0V, VFB=30V
ADIM Input Voltage Range
PWM Interface
fPWM
PWM Dimming Frequency
VPWM
Logic Input Level on
PWM pin
VPWM_L : Logic Low
VPWM_H : Logic High
tON_MIN
Min. On-Time (Note 1)
fSW=200kHz
RPWM
Pull-down Resistor on PWM pin
VVIN ≥ 8.5V
VVIN ≥ 8.5, VGATE = 0.9* VVLDO
VVIN ≥ 8.5V, VGATE = 0.1* VVLDO
GATE load : 10Ω / 1nF
GATE load : 10Ω / 1nF
fSW=200kHz (Note 1)
Note 1: These parameters, although guaranteed by design, are not tested in mass production.
1
Note 2: tscp =
× 4096
fsw
th
Oct 8 2014
0.6
V
V
ms
0.63
V
0.09
0.2
V
0.1
V
0.4
ILED=120mA
Current Sink Leakage Current
Boost MOSFET GATE Driver
VGATE
GATE Drive Voltage
ISOURCE
GATE Source Current
ISINK
GATE Sink Current
tRISE
GATE Output Rising Time
tFALL
GATE Output Falling Time
Soft Start
tSS
Soft Start Time
2.65
8.192
0.57
V
°C
8.5
VSBDOPEN
IFB
150
25
2.5
0.1
%
-2.5
V
+2.5
200
%
mA
5
uA
0.9
2.0
V
0.1
2.0
0.8
kHz
2.2
V
7
us
250
500
kΩ
4.95
35
30
5.2
5.45
0.1
0.1
0.5
0.5
V
mA
mA
us
us
8.5
13.0
ms
MAP3249 – 4-channel LED Driver for high brightness LEDs
Electrical Characteristics
Confidential
Datasheet Version 1.2
Unless otherwise noted, VIN = 12V, Cin=220uF, Cout=100uF, RISET=10kΩ, RFSW=250kΩ and TA = 25°C.
VADIM. vs. ILED
VADIM. vs. VFB(Headroom)
0.65
200
190
0.60
180
170
0.55
150
VHR [V]
ILED [mA]
160
140
130
0.50
0.45
0.40
120
110
0.35
100
90
0.30
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
0.9
1.0
1.1
1.2
1.3
VADIM [V]
1.4
1.5
1.6
1.7
1.8
1.9
2.0
VADIM [V]
Temp. vs ISD
Temp. vs IQ
10
65
6
ISD, Shutdown Current [A]
IQ, Quiescent current (mA)
8
6
4
2
0
55
45
35
25
-50
-30
-10
10
30
50
70
90
110
130
-50
-30
-10
10
o
Temp. vs UVLO
90
110
130
70
90
110
130
Temp. vs FSW
FOSC_200kHz, Frequency (200kHz) [kHz]
VUVLO, Under Voltage Lockout [V]
70
220
7.8
7.4
VUVLO_H
7.0
6.6
VUVLO_L
6.2
5.8
210
200
190
180
-50
-30
-10
10
30
50
70
o
Temperature [ C]
th
50
Temperature [ C]
8.2
Oct 8 2014
30
o
Temperature ( C)
90
110
130
-50
-30
-10
10
30
50
o
Temperature [ C]
MAP3249 – 4-channel LED Driver for high brightness LEDs
Typical Operating Characteristics
Confidential
Datasheet Version 1.2
Unless otherwise noted, VIN = 12V, Cin=220uF, Cout=100uF, RISET=10kΩ, RFSW=250kΩ and TA = 25°C.
Temp. vs VLDO
Temp. vs ILED
123
122
5.3
IFBX, FB current [mA]
VLDO, Low Dropout Voltage [V]
5.4
5.2
5.1
5.0
121
120
119
IFB1
IFB2
IFB3
IFB4
118
5.0
117
-50
-30
-10
10
30
50
70
90
110
130
-50
-30
-10
o
10
30
90
110
130
Temp. vs VPWM
2.2
2.2
2.0
2.0
VPWM, PWM Threshold Voltage [V]
VEN, Enable Threshold Voltage [V]
70
Temperature [ C]
Temp. vs VEN
7
50
o
Temperature [ C]
1.8
VEN_H
1.6
1.4
1.2
VEN_L
1.0
0.8
1.8
1.6
VPWM_H
1.4
1.2
VPWM_L
1.0
0.8
-50
-30
-10
10
30
50
70
90
110
130
-50
-30
-10
10
o
30
50
70
90
110
130
o
Temperature [ C]
Temperature [ C]
Temp. vs Vcs
Temp. vs OVP
2.65
0.63
VCS, Boost Over Current Protection
Threshold Voltage [V]
VOVP, Over Voltage Proction
Threshold Voltage [V]
2.60
2.55
2.50
VOVP_H
2.45
2.40
VOVP_L
2.35
2.30
-50
-30
-10
10
30
50
70
o
Temperature [ C]
th
0.61
0.60
0.59
0.58
0.57
2.25
Oct 8 2014
0.62
90
110
130
-60
-40
-20
0
20
40
60
o
Temperature [ C]
80
100
120
140
MAP3249 – 4-channel LED Driver for high brightness LEDs
Typical Operating Characteristics
Confidential
Datasheet Version 1.2
Unless otherwise noted, VIN = 12V, Cin=220uF, Cout=100uF, RISET=10kΩ, RFSW=250kΩ and TA = 25°C.
8
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Typical Operating Characteristics
Confidential
Datasheet Version 1.2
Unless otherwise noted, VIN = 12V, Cin=220uF, Cout=100uF, RISET=10kΩ, RFSW=250kΩ and TA = 25°C.
9
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Typical Operating Characteristics
Confidential
Datasheet Version 1.2
PARALLEL OPERATION
CURRENT MODE BOOST SWITCHING
CONTROLLER OPERATION
The MAP3249 employs current mode control boost
architecture that has a fast current sense loop and a
slow voltage feedback loop. Such architecture achieves
a fast transient response that is essential for the LED
backlight application.
DYNAMIC HEADROOM CONTROL
The MAP3249 features a proprietary Dynamic
Headroom Control circuit that detects the lowest
voltage from any of the FB1-FB4 pins. This lowest
channel voltage is used as the feedback signal for the
boost controller. Since all LED stacks are connected in
parallel to the same output voltage, the other FB pins
will have a higher voltage, but the regulated current
source circuit on each channel will ensure that each
channel has the same current.
INTERNAL 5.2V REGULATOR
10
The MAP3249 has built-in 5.2V LDO regulator to supply
internal analog and logic blocks. The LDO is powered up
when the EN pin is Logic High. A 2.2uF bypass capacitor is
required on the VLDO pin for stable operation of the LDO.
DIMMING SCHEME
The brightness control of the LEDs is performed by a
pulse-width modulation of the channel current. When a
PWM signal is applied to the PWM pin, the current
generators are turned on and off mirroring the PWM pin
behavior.
When PWM signal stays at low level (<0.8V), the
MAP3249 turns off the boost circuitry, but internal
circuit is enabled so the MAP3249 increases the output
voltage promptly.
Min. PWM dimming on-time of MAP3249 is Max. 10us at
200kHz boost switching frequency. Thus, following table
shows Min. PWM dimming duty-cycle at various PWM
input frequency at 200kHz boost switching frequency.
fPWM [Hz]
100
200
300
400
500
1000
1500
2000
Min. Duty-cycle
0.30%
0.40%
0.43%
0.48%
0.50%
0.70%
1.20%
1.70%
Even the MAP3249 has 4 channels and 200mA LED
current capability per channel, 2 channels and 400mA
application can be supported by tying 2FBs into 1ch, so
the LED current capability can be increased to 400mA.
LED CURRENT ADJUSTMENT
The MAP3249 sets the LED current through the
voltage level on the ADIM pin. ADIM pin voltage vs.
LED current is as following table.
The RISET/1% resistor must be connected between
the ISET pin and ground.
Ω
RISET 10 kΩ
ADIM Voltage [V]
LED Current [mA]
0.9
90
1.0
100
1.2
120
1.4
140
1.6
160
1.8
180
2.0
200
The relationship between ADIM pin voltage, RISET
value and LED current is defined by following equation.
[V ]
V
× 1000
I LED [mA] = ADIM
RISET [ kΩ]
The MAP3249 offers protection functions to limit excess
LED current increase at abnormal ISET and ADIM pin
voltage. If the ADIM or ISET pin voltage is at following
conditions abnormally, the MAP3249 turns off the GATE
output and internal LED current sink MOSFETs.
V_ISET ≤ 0.3V
V_ADIM ≥ 2.6V
BOOST SWITCHING FREQUENCY
The switching frequency of the MAP3249 should be
programmed between 100kHz and 500kHz by an
external resistor connected between the FSW pin and
ground. Do not leave this pin open. The approximate
operating boost switching frequency can be calculated
by following equation.
f SW [ MHz] =
50
R FSW [kΩ]
If the FSW pin voltage is decreased to below or equal
to 0.6V abnormally the MAP3249 turns off the GATE
output to protect excess switching frequency increase.
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Application Information
Confidential
Datasheet Version 1.2
(1) The MAP3249 has soft-start circuitry internally
and the soft-start time(tss) is typical 8.5ms.
(2)
‘Unused Channel Detection Function’
There can be exist applications which do not use
all the FB pins(4 channel). Conventional multichannel LED drivers boost the output voltage to
OVP level to check open FB(s).
The MAP3249 detects unused FB(s) and
excludes corresponding FB(s) automatically from
headroom control before start-up. The unused
FB(s) must be connected to GND. This ensures
the output voltage is not boosted to OVP level at
start-up. If the unused FB(s) are not connected to
GND, the output voltage is boosted up to OVP level
like conventional boost LED driver.
These features significantly reduce the start-up
current and prevent abnormal operation at start-up.
OUTPUT OVER VOLTAGE PROTECTION
11
To protect the boost converter when the load is open
or the output voltage becomes excessive for any
reason, the MAP3249 features a dedicated overvoltage
feedback input. The OVP pin is connected to the center
tap of a resistive voltage-divider from the high voltage
output. When the OVP pin voltage exceeds typical 2.5V, a
comparator turns off the external power MOSFET. This
switch is re-enabled after the OVP pin voltage drops typical
100mV hysteresis below the protection threshold. This over
voltage protection feature ensures the boost converter failsafe operation when the LED channels are disconnected
from the output.
A 5V zener diode is recommendable to avoid pin
damage when the RVOPL resistor is open abnormally.
The OVP voltage of output voltage can be calculated by
following equation.
R
VOUT _ OVP [V ] = 2.5 × (1 + OVPH )
ROVPL
th
Oct 8 2014
UNDER VOLTAGE LOCKOUT
If the input voltage falls below the UVLO level of
typical 6.5V on the VIN pin, the device will stop
switching and be reset. Operation will restart when the
VIN pin voltage rises to 7.5V. This ensures fail-safe
operation when the input voltage falls below Min. VIN
voltage of IC.
SBD OPEN PROTECTION
When OVP pin voltage is less than 0.1V, the
MAP3249 turns off the GATE output.
This protects the driver from damage if the output
schottky diode is open(defective or poor solder contact).
MAP3249 – 4-channel LED Driver for high brightness LEDs
START-UP
Confidential
Datasheet Version 1.2
The MAP3249 features Over-Current Protection
(OCP) by sensing CS pin voltage. This CS pin is used
for inductor current sensing for current mode control as
well.
If the CS pin voltage exceeds typical 0.6V, the
MAP3249 turns off the GATE output.
The internal OCP sensing voltage decreases with
increase of gate duty-cycle due to internal slope
compensation which ensures stable CCM operation.
Following graph shows the relationship between gate
duty-cycle and internal OCP sensing typical voltage.
The RCS value should be chosen that the output
voltage can be boosted up to OVP level. And the Iout
value should be considered with Max. 3 channel
because the OVP is occurred LED open event only.
Thus,
I IN ( OVP ) [ A] =
VOUT _ OVP × I LED / CH × ( N FB − 1)
η × VIN
η : efficiency
NFB : The number of using channel
(3) Find typical VCS_OCP value at given D(OVP)
VCS _ OCP _ TYP.[V ] = −0.21255 D( OVP ) + 0.56125
(4) Find RCS value
In order to avoid touching the current limit during
normal operation, the voltage across the current
sensing resistor Rcs should be less than 80% of the
worst case current limit voltage.
RCS [Ω] = 0.8 ×
VCS _ OCP _ TYP
I L _ peak
Example
12
Vin=24V, Vout_ovp=55V, η=90%, ILED/ch=100mA,
LED string=4X16, fsw=200kHz
VCS _ OCP _ TYP.[V ] = −0.21255 D + 0.56125
RO × D × (1 − D) 2
= 37.5[ µH ]
2 × f SW
In this case, chosen inductance value is 47uH for
CCM operation.
RCS Setting Procedure
LB =
(1) Choose boost inductor value
Once the LED current, the input and output voltage
and the switching frequency are fixed, the inductance
value defining the boundary between DCM and CCM
operation can be calculated as;
LB [H ] =
RO × D × (1 − D ) 2
2 × f SW
where, Ro=Vout/Iout
VIN × D(OVP)
f SW × L
I L _ peak _ CCM = I IN ( OVP ) +
th
Oct 8 2014
(2) Find peak inductor current
I IN ( OVP ) =
VOUT _ OVP × I LED / CH × ( 4 − 1)
I L _ peak _ CCM
= 0 .76[ A]
η × V IN
V IN × D ( OVP )
= I IN ( OVP ) +
= 1 .48[ A]
2 f SW × L
(3) Find typical VCS_OCP value at given D(OVP)
(2) Find peak inductor current at selected boost
inductance
I L _ peak _ DCM =
(1) Choose boost inductor value
VIN × D( OVP )
2 f SW × L
VCS _ OCP _ TYP = −0.21255 D( OVP ) + 0.56125 = 0.441[V ]
(4) Find RCS value
RCS = 0.8 ×
VCS _ OCP _ TYP
I L _ peak
= 0.24[Ω]
MX provides ‘Design spreadsheet for MAP3249
Ver0.0’ for ease external components calculation.
MAP3249 – 4-channel LED Driver for high brightness LEDs
BOOST OVER-CURRENT PROTECTION
Confidential
Datasheet Version 1.2
Open threshold
OVP
LED open protection
In case the voltage on any of LED current sink pins (FB1~4) is below LED open protection threshold due to LED open
during normal operation, the output voltage is boosted up to 100% of OVP level and the MAP3249 automatically excludes
the corresponding channel and remaining string(s) will continue operation.
LED SHORT PROTECTION
13
If the voltage at any of the FB1-4 pins exceeds LED short detection voltage(typ. 8.5V) due to LED short during
normal operation and persists for tscp, the MAP3249 automatically turns off the corresponding channel and remaining
channel(s) will continue operation.
The protection status is latched internally and can be cleared by recycling the EN pin or applying a complete poweron-reset(POR).
When LED(s) is(are) open on any channel, the output voltage is boosted up to OVP level and this can cause
abnormal LED short protection due to high FB voltage. To avoid this abnormal operation, the MAP3249 disables the
LED short protection function with related to Min. FB voltage conditions.
Min. VFB ≥ 2.60V => LED short protection disable
Min. VFB ≤ 2.15V => LED short protection enable
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
LED OPEN PROTECTION
Confidential
Datasheet Version 1.2
14
A capacitor on the VLDO pin begins charing after EN is turned-on. Once the VIN voltage reaches about 7.5V(See
UVLO specification), the internal UVLO is released. The MAP3249 checks the initial open FB(s) and excludes
corresponding FB(s) from headroom control before internal PG signal is set up. The unused FB(s) must be
connected to GND. Internal controller starts boosting with first PWM input and performs soft-start. After soft-start is
end or during soft-start period, the output voltage is boosted up to regulation voltage(total forward voltage of LED
bar + FB Voltage) without touching OVP level and the controller performs headroom control.
The MAP3249 boosts the output voltage only in condition that VIN is applied and EN, PWM and ADIM is turned-on. And
there is no limitation with regard to turn-on sequence. But in case that VIN(input voltage of booster) is applied lastly after
EN, PWM and ADIM is turned-on, the start-up current is increased because the output voltage is boosted from 0V.
If the PWM signal remains logic low for over than 16.4ms(1/fsw * 8192) at 500kHz boost switching frequency during
normal operation, the controller regards it as dim-zero condition. Because of discharge of output capacitor through the
OVP sensing resistors during the dim-zero time, the output voltage getting declined. The MAP3249 performs soft-start as
soon as PWM signal rises to boost the output voltage rapidly.
The controller stops switching right after EN is turned-off.
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
OPERATION TIMING CHART
Confidential
Datasheet Version 1.2
Boost MOSFET
Inductor
The critical parameters for selection of a MOSFET
are:
The inductor value should be decided before system
design. Because the selection of the inductor affects
the operating mode of CCM(Continuous Conduction
Mode) or DCM(Discontinuous Conduction Mode).
The inductance value defining the boundary between
DCM and CCM operation can be calculated as;
LB [H ] =
RO × D × (1 − D ) 2
2 × f SW
1. Maximum drain current rating, ID(MAX)
2. Maximum drain to source voltage, VDS(MAX)
3. On-resistance, RDS(ON)
4. Gate source charge QGS and gate drain charge QGD
5. Total gate charge, QG
The maximum current through the power MOSFET
happens when the input voltage is minimum and the
output power is maximum. The maximum RMS current
through the MOSFET is given by;
where, Ro=Vout/Iout
In CCM operation, inductor size should be bigger,
even though the ripple current and peak current of
inductor can be small. In DCM operation, even ripple
current and peak current of inductor should be large
while the inductor size can be smaller.
The inductor DC current or input current can be
calculated as following equations.
V
× I OUT
I IN [ A] = OUT
η × V IN
15
I RMS ( MAX ) = I IN ( MAX ) × D MAX
The off-state voltage of the MOSFET is approximately
equal to the output voltage plus the diode Vf. Therefore,
VDS(MAX) of the MOSFET must be rated higher than the
maximum output voltage(OVP voltage).
The power losses in the MOSFET can be separated
into conduction losses and switching losses. The
conduction loss, Pcond, is the I2R loss across the
MOSFET. The conduction loss is given by;
PCOND = R DS (ON ) × I RMS 2 × k
η – Efficiency of the boost converter
Then the duty ratio is,
− V IN + V D
V
D = OUT
VOUT + V D
VD – Forward voltage drop of the output rectifying
diode
When the boost converter runs in DCM ( L < LB), it
takes the advantages of small inductance and quick
transient response. The inductor peak current is,
V ×D
I L _ peak _ DCM = IN
f SW × L
The converter will work in CCM if L > LB, generally the
converter has higher efficiency under CCM and the
inductor peak current is,
I L _ peak _ CCM = I IN +
V IN × D
2 f SW × L
where k is the temperature coefficient of the MOSFET.
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 loss.
PSW =
+
QGS1 × RG
× V DS × I IN × f SW
V DR − VTH
QGD × RG
× V DS × I IN × f SW
V DR − V PLT
where VTH is the threshold voltage, VPLT is the plateau
voltage, RG is the gate resistance, VDS is the drainsource voltage, VDR is the drive voltage
The total gate charge, QG, is used to calculate the
gate drive loss. The expression is
PDR = QG × V DR × f SW
Fast switching MOSFETs can cause noise spikes
which may affect performance. To reduce these spikes
a drive resistor can be placed between GATE pin and
the MOSFET gate.
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
EXTERNAL COMPONENTS SELECTION
Confidential
Datasheet Version 1.2
Schottky diodes are the ideal choice for MAP3249
due to their low forward voltage drop and fast
switching speed. Make sure that the diode has a
voltage rating greater that the possible maximum
output voltage. The diode conducts current only when
the power switch is turned off.
Layout Consideration
A gate drive signal output from GATE pin becomes
noise source, which may cause malfunction of IC due to
cross talk if placed by the side of an analog line. It is
recommended to avoid placing the output line especially
by the side of CS, ADIM, ISET, FSW, OVP, COMP pins
as far as possible.
(1) SOIC
Input Capacitor
In boost converter, input current flows continuously
into the inductor; AC ripple component is only
proportional to the rate of the inductor charging, thus,
smaller value input capacitors may be used. Ensure the
voltage rating of the input capacitor is suitable to
handle the full supply range.
A capacitor with low ESR should be chosen to
minimize heating effects and improve system efficiency.
Output Capacitor
16
The output capacitor acts to smooth the output
voltage and supplies load current directly during the
conduction phase of the power switch. Output ripple
voltage consists of the discharge of the output
capacitor during the FET ton period and the voltage
drop due to load current flowing through the ESR of the
output capacitor. The ripple voltage is shown in
following equation.
∆VOUT =
I OUT × D
+ I OUT × ESR
C OUT × f SW
Assume a ceramic capacitor is used. The minimum
capacitance needed for a given ripple can be estimated
by following equation.
COUT =
(V IN − VOUT ) × I OUT
VOUT × f SW × ∆VOUT
Loop Compensation
The MAP3249 controls in current mode. Current mode
easily achieves compensation by consisting simple
single pole from double pole that LC filer makes at
voltage mode. In general, crossover frequency is
selected from 1/3 ~ 1/6 range of the switching
frequency. If fc is large, there is possibility of oscillation
to occur, although time response gets better.
On the other hand, if fc is small, time response will be
bad, while it has improved stability, which may cause
over shoot or under shoot in abnormal condition.
th
Oct 8 2014
(2) ETSSOP
- Exposed pad shoud be tied to GND with
multiple vias
MAP3249 – 4-channel LED Driver for high brightness LEDs
Output Rectifying Diode
Confidential
Datasheet Version 1.2
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature.
The maximum power dissipation can be calculated by
the following formula:
Pd (MAX ) =
TJ (MAX ) −T A
θ JA
where TJ(MAX) is the maximum junction temperature, TA
is the ambient temperature, and θJA is the junction to
ambient thermal resistance.
The maximum power dissipation depends on the
operating ambient temperature for fixed TJ(MAX) and
thermal resistance, θJA. For the MAP3249 packages,
the derating curve in following graph allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
17
For a typical application, the operation power of the IC
can be calculated roughly by;
Pd = (VIN ⋅ I IN ) + (VFB1 ⋅ I FB1 +    + VFB4 ⋅ I FB4 ) ⋅ DPWM
where VIN represents the input voltage at the VIN pin of
the IC and IIN represents the current flow into the VIN
pin of the IC. DPWM is duty cycle of PWM input signal.
th
Oct 8 2014
MAP3249 – 4-channel LED Driver for high brightness LEDs
Thermal Consideration
Confidential
Datasheet Version 1.2
MAP3249 – 4-channel LED Driver for high brightness LEDs
Physical Dimensions
18
16 Leads E-TSSOP
Dimension (mm)
Symbol
Min
Nom
Max
A
-
-
1.20
A1
0.00
-
0.15
A2
0.80
b
0.19
-
0.30
C
0.09
-
0.20
D
4.90
-
5.10
D1
2.20
-`
-
E
6.40 BSC
E1
4.30
-
4.50
E2
2.20
-
-
e
L
th
0.65 BSC
0.45
-
L1
1.00 REF
L2
0.25 REF
Θ1
Oct 8 2014
1.05
0°
-
0.75
8°
Confidential
Datasheet Version 1.2
MAP3249 – 4-channel LED Driver for high brightness LEDs
16 Leads SOIC
19
MagnaChip Semiconductor Ltd. doesn’t not recommend the use of its products in hostile environments, including, without limitation,
aircraft, nuclear power generation, medical appliances, and devices or systems in which malfunction of any product can reasonably
be expected to result in a personal injury. Seller’s customers using or selling Seller’s products for use in such applications do so at
their own risk and agree to fully defend and indemnify Seller.
MagnaChip reserves the right to change the specifications and circuitry without notice at any time. MagnaChip does not consider
responsibility for use of any circuitry other than circuitry entirely included in a MagnaChip product.
is a registered trademark of MagnaChip Semiconductor Ltd.
MagnaChip Semiconductor Ltd.
891, Daechi-Dong, Kangnam-Gu, Seoul, 135-738 Korea
Tel : 82-2-6903-3451 / Fax : 82-2-6903-3668 ~9
www.magnachip.com
th
Oct 8 2014
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising