elm916da

ELM916DA 450V LED controller
■General description
ELM916DA is high efficiency LED driver control IC, which uses fewer components and drives LED with
constant current. ELM916DA works in open loop and current mode, and can be programmed to operate in either
constant frequency or constant off-time mode. ELM916DA consists of an 8 to 450V linear regulator, which
makes working in wide input voltage range without external low voltage power supply. Internal 0 to 100%
PWM dimming and 0 to 245mV linear dimming help to adjust LED luminance. ELM916DA is suitable for buck
LED drivers; it is capable of providing good stability response because of open loop current mode control and
with the controller, it is able to regulate output current without any compensation outstandingly.
■Features
■Application
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Open loop peak current controller
Constant Current LED Driver
LED string from one to hundreds of diodes
Support linear and PWM dimming interface
Requires few external components
Buck system efficiency
: >90%
Internal linear regulator
: 8 to 450V
Constant off time function
: 50%
(when duty cycle is over)
• Package
: SOP-8
DC/DC LED driver applications
RGB backlighting LED driver
General purpose constant current source
Signage and decorative LED lighting
Chargers
Non-isolation LED bulb
■Maximum absolute ratings
Parameter
VIN voltage power supply
VDD voltage
LD voltage
PWMD voltage
GATE voltage
CS voltage
RT voltage
Power dissipation
Operating ambient temperature
Storage temperature
Symbol
Vin
Vdd
Vld
Vpwmd
Vgate
Vcs
Vrt
Pd
Top
Tstg
Limit
500
Unit
V
36
V
7
V
630
-40 to +85
-55 to +150
mW
°C
°C
Caution: Permanent damage to the device may occur when ratings above maximum absolute ones are used.
■Selection guide
ELM916DA-N
Symbol
a
b
c
Package
Product version
Taping direction
D: SOP-8
A
N: Refer to PKG file
ELM916 D A - N
↑ ↑ ↑
a b c
* Taping direction is one way.
6- 1
Rev.1.4
ELM916DA 450V LED controller
■Pin configuration
SOP-8(TOP VIEW)
1
8
2
7
3
6
4
5
Pin No.
1
2
3
4
5
6
7
Pin name
VIN
CS
GND
GATE
PWMD
VDD
LD
8
RT
Pin description
Input voltage 8 to 450V DC
Sense LED string current
Device ground
Drives the gate of the external MOSFET
Low frequency PWM dimming pin.
Internally regulated supply voltage.
Linear dimming input
Frequency is controlled by external resistor.
It can work with constant off time control
when resistor connect to GATE
■Marking
SOP-8
Mark
ELM916DA
Content
Product name
abc
Assembly lot No.:
000 to 999 repeated
■Standard circuit
Vin
C1
R2
8
7
6
C2
5
RT
VIN
ELM916DA
LD
VDD
CS
GND
PWMD GATE
SBD
R1 *
1
LED1
LED2
L
2
R4 *
3
C3 *
4
R3
* Option R1 for ESD.
Option C3,R4 for blanking time.
6- 2
Rev.1.4
ELM916DA 450V LED controller
■Block diagram
VIN 1
5V
7.5V
HV
Regulator
LDO
●
OSC
8 RT
VDD 6
245mV
+
S
Q
LD 7
●
4 GATE
Driver
R
+
2 CS
TST
3
5
GND
PWMD
■Electrical characteristics
Parameter
Symbol
Test condition
Input DC supply voltage range Vindc Line voltage or DC input voltage
Shut-down mode
Iinsd
PWM_D=GND, Vin=8V
supply current
Internal regulated voltage
Vdd
Vin=8 to 450V
VDD under voltage lockout
UVLO Vin rising
threshold
UVLO hysteresis
ΔUVLO Vin falling
PWMD input high level
Ven(hi) Vin=8 to 450V
PWMD input low level
Ven(lo) Vin=8 to 450V
Current sense pull-in
Vcs-th Vin=8 to 450V, Top=25°C
threshold voltage
Linear dimming pin
Vld
Vin=8 to 450V
voltage range
Top=25°C, Vld=Vdd,
Current sense blanking time
Tblank
Vcs=Vcs-th+50mV after Tblank
Rosc=1MΩ
Oscillator frequency
Fosc
Rosc=226kΩ
Maximum duty cycle
Dmax Vcs=0V, Vin=Open, Vdd=10V
GATE sourcing current
Isource Vgate=0V, Vdd=7.5V
GATE sinking current
Isink
Vgate=Vdd, Vdd=7.5V
GATE rising time
tr
Cgate=500pF, Vdd=7.5V
GATE falling time
tf
Cgate=500pF, Vdd=7.5V
Thermal shutdown
Tsd
temperature
Thermal shutdown hysteresis
Tsh
6- 3
Min.
8
Typ.
Top=25°C
Max. Unit
450
V
0.1
0.2
mA
6.7
7.5
8.0
V
5.5
6.0
6.5
V
0.8
mV
V
V
255
mV
250
mV
650
ns
2.0
235
500
245
0
250
500
65
20
83
165
165
50
50
95
95
150
150
kHz
kHz
%
mA
mA
ns
ns
155
°C
40
°C
Rev.1.4
ELM916DA 450V LED controller
■Application notes
ELM916DA, buck, boost or buck-boost converter controller with low cost, is specifically designed for driving
multiple LED strings or arrays. It can be operated from either universal 90 to 240Vac or DC voltage between 8
and 450Vdc. ELM916DA is able to drive multiple strings of High-Brightness (HB) LEDs and regulate constant
current to ensure brightness and spectrum of the LEDs. With constant current driving method, LED lifetime
can be lengthened. ELM916DA provides soft start function to reduce inrush current. It is possible to charge
LD capacitor by letting current of 1 to 5uA to flow to the resistor between VDD and LD. The voltage increases
slopingly until it rises the current limit level of CS. By setting suitable resistor in CS, ELM916DA, with feedforward control, is capable of providing constant current to LED series while input voltage varies.
It is possible that while ELM916DA is providing power supply to the internal circuit which consists of high
voltage regulator for generating fixed VDD, ELM916DA is able to serve as a bias supply for low voltage
external circuit.
1. LED driver operation
ELM916DA can operate as basic types of converter controller under dis/continuous non-isolated current mode.
When external power N-Mosfet is turned on by GATE, the input energy would be stored in the inductor through
LED driver. When N-Mosfet is switched off, the energy stored in the inductor would be discharged toward
LED.
The internal power supply activates when voltage of VDD exceeds UVLO threshold. The output current is
controlled current of CS. The current limit level of ELM196DA is set by LD.
To avoid unstable regulation while ELM916DA is adopted in Buck topology, it is required to keep duty ratio
under 50%; the input voltage is required to be designed as 2 times higher than the forward voltage of LEDs.
2. Supply current
The current consumption under operation of ELM916DA is 0.2mA which can be generated from the internal
HV circuit. For ELM916DA, it is not required to use bulky startup resistors which are typically necessary for
offline applications. Moreover, since the internal regulator supplies 7.5V, it is possible that ELM916DA is able
to supply the power continuously. Because the current consumption of ELM916DA is extremely low, the power
consumption can be kept low even if the input voltage of ELM916DA is high.
3. Current detection
The current detection input of ELM916DA is connected to non-inverting inputs of two comparators; inverting
terminal of one comparator is connected to internal 245mV reference while it is connected to LD of the other
one. Outputs of both comparators are connected to OR gate while output of OR gate is connected to reset pin of
the flip-flop. Hence, the comparator whose voltage at inverting terminal is lower controlls when GATE output is
turned off.
The outputs of the comparators also include a 500ns blanking time due to the turn on spike current. Some
solution will add RC filter to prevent this situation.
4. Dimming
There are two types of dimming function of ELM916DA; linear and PWM types:
1) Linear dimming
The linear dimming function of ELM916DA can be adjusted voltage level of LD by changing current limit.
6- 4
Rev.1.4
ELM916DA 450V LED controller
2) PWM dimming
PWM dimming function of ELM196DA can be adjusted by driving PWMD with low frequency square wave .
GATE drive output is zero when PWM signal is low; GATE drive output voltage is produced when PWMD is
high.
5. Operating frequency
The oscillator frequency of ELM916DA is set by RT external resistor. The following chart shows the
connection between RT and frequency.
f(Hz)
100k
20k
0
0 200k
1M
Ω
6. Inductor selection
The coil value can be calculated from the peak of ripple current of the required coil; please refer to the
following formulas.
Since ripple current is usually set to be 30% of LED drive current, the following example is shown based on
30% and the average LED drive current, ILED, is 350mA. The next step would be to determine total forward
voltage of LED. If 10 HB LEDs are in series connection and the forward voltage of average current is set to be
3V, the total voltage descend of LEDs ,VLEDS, would be 30V.
The input voltage from average synchorous circuit is:
Vin=120V×1.414=170V
The switching duty ratio is:
D = Vleds/Vin = 30/170 = 0.176
If the given switching frequency is 50kHz, required ON time of MOSFET transistor would be:
Ton = D/fosc = 3.52μs
The required inductance of coil wouild be: (Vin - Vled)/L × Ton = 30% × Iled
L = (Vin - Vled) × Ton/(0.3 × Iled) = 4.69mH
7. Input bulk capacitor
An input filter capacitor should be designed to hold the rectified AC voltage above twice the LED string
voltage throughout the AC line cycle.
Assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum
value of the bulk input capacitor is given by:
Cmin = Iled × 0.06 × Vled/V2in = 22μF
6- 5
Rev.1.4
ELM916DA 450V LED controller
■Buck topology sample application characteristics
VIN
C1
10μF
R2
390kΩ
SBD
LED2
8
6
5
RT
VIN
ELM916DA
LD
VDD
CS
GND
PWMD GATE
1
2
R4 470Ω
3
4
L
2mH
C3
1nF
R3
0.6Ω
Vin-Average Iin
Vin-Average Iled
400
70
390
Average Iled (mA)
60
Iin (mA)
50
40
30
20
10
0
3.5V, 350mAx3
LED3
7
C2
2.2μF
LED1
R1
1kΩ
380
370
360
350
340
330
320
310
70
80
300
90 100 110 120 130 140 150
70
80
90 100 110 120 130 140 150
Vin (V)
Vin (V)
Vin-Fsw
60.00
58.00
Fsw (kHz)
56.00
54.00
52.00
50.00
48.00
46.00
44.00
42.00
40.00
70
80
90 100 110 120 130 140 150
Vin (V)
6- 6
Rev.1.4
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