Thermally enhanced Low V
FB
Step-Down LED Driver
ADT6780
Thermally enhanced
Low V
FB
Step-Down LED Driver
General Description
ADT6780
The ADT6780 is a thermally enhanced current mode step down LED driver. That is designed
to deliver constant current to high power LEDs. The device is suitable for various high power
LED application due to the wide operating range(VIN 4.5V~28V) and high output
capability(continuous 2A). with a very low feedback voltage(V
FB
=0.2V) power dissipation can
be minimized. Fault condition protection includes cycle-by-cycle current limiting and thermal
shutdown.
The package is available in a standard SOP8-PP(with Exposed pad) package.
Features
• Feedback reference voltage : 0.2V
• Current mode buck LED driver with 925kHz
fixed frequency
• Input voltage range : 4.5V to 28V
• Continuous output current : 2A
• Up to 93% efficiency
• Integrated Power MOSFET switch : 80mΩ
• 10㎂ shutdown mode
• Thermal shutdown & current limit protection
• Under Voltage LOckout
Applications
•
•
•
•
High power LED/IR-LED Lighting
Automotive and Marine Lighting
Architecture Lighting
General Lighting Solutions
Typical Application Circuit
C5
1
L1
BST
SW
3
D1
VOUT
C2
D2
VIN
C1
2
VIN
FB
5
U1
7
R1
EN
EN
COMP
6
C3
8
C4
SS
GND
4
R2
C6
OPTION
Figure 1. Typical Application Circuit
* This specifications are subject to be changed without notice
Jul. 12. 2012 / Preliminary
1/13
http://www.ad-tech.co.kr
Thermally enhanced Low V
FB
Step-Down LED Driver
ADT6780
Part List
Component
U1
D1
L1
C1
C2
C3
C4
C5
R1
R2
IC
Schottky Barrier Diode
Chip inductor
MLCC
MLCC
MLCC
MLCC
MLCC
Chip resistor
Chip resistor
Type
Value (Model)
ADT6780
B230A
6.8uH / 3A
10㎌ / 35V
10㎌ / 10V
8.2㎋
100㎋
10㎋
0.2Ω / 1%
2㏀
Manufacturer
ADTech
DIODES
TDK
-
-
-
-
-
-
-
Pin Description
Pin No.
1
2
3
4
5
6
7
8
Name
BST
VIN
SW
GND
FB
COMP
EN
SS
Description
High-Side Gate Drive Boost Input. This pin acts as the power supply of high-side gate
driving blocks. Connect a 10nF or greater capacitor between SW and BST pin.
Power supply input. Bypass VIN to GND with a suitably large capacitor to eliminate
noise on the input to the IC.
Switching node. The free-wheeling diode is connected between SW and GND.
Ground. Connect the exposed pad on backside to GND.
Feedback voltage input. The regulated FB voltage is 0.2V typically.
Compensation node. COMP is used to compensate the regulation control loop.
Chip enable input. Also this pin functions UVLO input.
Soft start control node. This pin controls the soft start period.
BST
VIN
SW
GND
1
2
3
4
8
7
6
5
SS
EN
COMP
FB
ADT6780
exposed pad
* connect to GND
Package outline
* This specifications are subject to be changed without notice
Jul. 12. 2012 / Preliminary
2/13
http://www.ad-tech.co.kr
Thermally enhanced Low V
FB
Step-Down LED Driver
ADT6780
Functional Block Diagram
EN
7
VIN
2
Current
Sense
Amplifier
+
-
Shutdown
Internal
Regulator
Voltage
Reference
OSC
Regulator
R
S
1 BST
Σ
Current
Limit
+
+
-
FB 5
-
Error
Amplifier
6
COMP
Comparator
Control
LOGIC
Driver
3 SW
Driver
8
SS
4
GND
Figure 2. Functional Block Diagram
Absolute Maximum Ratings
(Note1)
Parameter
Power supply voltage
SW pin voltage
BST pin voltage
All Other Pins
Max. power dissipation (Ta=25℃) (Note2)
Thermal resistance (Note3)
Storage temperature
Junction temperature
Symbol
V
IN
V
SW
V
BST
-
Min.
-0.3
-0.5
-0.3
-0.3
-
-
-65
-
Typ.
-
-
-
-
-
60
-
-
Max.
30
V
IN
+ 0.3
V
SW
+ 6
+6
2.08
-
+150
+150
Unit
V
V
V
V
W
℃/W
℃
℃
P
D
Θ
JA
T
STG
T
J.MAX
Note1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
Note2. Derate 17mW/℃ above +25℃. This is recommended to operate under this power dissipation specification.
Note3. Measured on JESD51-7, 4-layer PCB
Operating Ratings
Parameter
Power supply voltage
Output voltage
Operating temperature
Junction temperature
Symbol
V
IN
V
OUT
T
OPR
T
J
Min.
4.5
0.2
-40
-
Typ.
12.0
-
-
-
Max.
28.0
16
+85
+125
Unit
V
V
℃
℃
* This specifications are subject to be changed without notice
Jul. 12. 2012 / Preliminary
3/13
http://www.ad-tech.co.kr
Thermally enhanced Low V
FB
Step-Down LED Driver
ADT6780
Electrical Characteristics (Ta=25℃, V
IN
=12V, unless otherwise noted)
Parameters
Supply current (shutdown)
Supply current (quiescent)
Feedback voltage
Error Amplifier Voltage Gain
Error Amplifier Transconductance
High-Side Switch On Resistance (Note4)
Low-Side Switch On Resistance (Note4)
High-Side Switch Leakage Current
Peak Current Limit
Current sense to COMP transconductance
Oscillator frequency
Fold-back frequency
Maximum Duty cycle
Minimum On time
UVLO rising threshold
UVLO threshold hysteresis
EN threshold voltage
Enable pull-up current
Soft-Start Period
Thermal shutdown (Note4)
D
MAX
T
ON
G
CS
F
SW
Symbol
I
OFF
I
Q
V
FB
A
EA
G
EA
R
ON.H
R
ON.L
Condition
V
EN
= 0V
V
EN
= 3V, V
FB
= 1.4V
4.5V
≤
V
IN
≤
28V,
V
COMP
< 2V
-
ΔI
COMP
=
±10㎂
-
-
V
EN
= 0V , V
SW
= 0V
Duty=50%
-
-
V
FB
= 0V
V
FB
= 0.15V, IO=1A
-
V
EN
rising
-
-
V
EN
= 0V
C4 = 100㎋
-
Min.
-
-
0.184
-
-
-
-
-
-
-
-
-
76
-
2.00
-
0.8
-
-
-
Typ.
10
0.7
0.200
750
750
80
10
0.1
3
11
925
125
86
100
2.35
250
1.1
2.0
3
145
Max.
-
-
0.216
-
-
-
-
10
-
-
-
-
99
-
2.70
-
1.4
-
-
-
Unit
㎂
㎃
V
V/V
㎂/V
mΩ
Ω
㎂
A
A/V
㎑
㎑
%
㎱
V
㎷
V
㎂
㎳
℃
Note4. guaranteed by design.
* This specifications are subject to be changed without notice
Jul. 12. 2012 / Preliminary
4/13
http://www.ad-tech.co.kr
Thermally enhanced Low V
FB
Step-Down LED Driver
ADT6780
Typical Operating Characteristics
VIN=12V, Load : 1A / one 4W White LED and Ta=25℃, unless otherwise noted
100%
95%
90%
Efficiency
VIN=6V
V
SW
10V/div
VIN=12V
VIN=24V
V
OUT
(AC)
20mV/div
I
INDUCTOR
0.5A/div
Steady State Operation
Efficiency (%)
85%
80%
75%
70%
65%
60%
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1㎲/div
LED Current (A)
VFB vs Die Temperature
0.216
0.212
0.208
0.204
0.200
0.196
0.192
0.188
0.184
-40
-20
0
20
40
60
80
100
120
Switching Frequency vs Die Temperature
1050
Switching Frequency (kHz)
1000
Feedback Voltage (V)
950
900
850
800
750
-40
-20
0
20
40
60
80
100
120
Temperature (℃)
Temperature (℃)
Output Short
4.0
Peak Current vs Duty
3.5
Inductor Peak Current (A)
4㎲/div
V
OUT
2V/div
3.0
V
SW
10V/div
I
INDUCTOR
2A/div
2.5
2.0
1.5
1.0
0
20
40
60
80
100
Duty (%)
* This specifications are subject to be changed without notice
Jul. 12. 2012 / Preliminary
5/13
http://www.ad-tech.co.kr
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