SN3350
40V LED driver with internal switch
General Description
The SN3350 is a continuous mode inductive step-down
converter, designed for driving a single LED or multiple
series connected LEDs efficiently from a voltage source
higher than the LED voltage. The chip operates from an
input supply between 6V and 40V and provides an
externally adjustable output current of up to 750mA.
Depending upon supply voltage and external components,
this can provide up to 30 watts of output power.
The SN3350 includes an integrated output switch and a
high-side output current sensing circuit, which uses an
external resistor to set the nominal average output current.
Output current can be adjusted linearly by applying an
external control signal to the ADJ pin. The ADJ pin will
accept either a DC voltage or a PWM waveform. This will
provide either a continuous or a gated output current.
Applying a voltage of 0.2V or lower to the ADJ pin turns
the output off and switches the chip into a low current
standby state.
The chip is assembled in SOT23-5 and SOT89-5 package.
SOT23-5 is available for 350mA output current application;
SOT89-5 is available for 700mA output current application.
Features
Simple low parts count
Internal 40V power switch
Wide input voltage range: 6V to 40V
Up to 750mA output current（SOT89-5 package）
High efficiency (up to 95% )
Typical 1200：1 dimming rate
Typical 5% output current accuracy
Single pin on/off and brightness control using DC
voltage or PWM
Up to 1MHz switching frequency
Inherent open-circuit LED protection
Thermal shutdown protection circuitry
Two packages available for different current
Applications
Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Illuminated sign
Application Circuit
March 2009 Ver1.0
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SI-EN Technology
SN3350
Pin Configurations
Package
LX
Pin
Configurations
1
5
V
IN
SOT23-5
GND
2
ADJ
3
4
I
SENSE
SOT89-5
Pin Description
Pin Name
LX
GND
NO.
1
2
Drain of power switch
Ground (0V)
Multi-function On/Off and brightness control pin:
* Leave floating for normal operation.(V
ADJ
= V
REF
= 1.2V giving nominal average output current
I
OUT nom
=0.1/R
S
)
* Drive to voltage below 0.2V to turn off output current
* Drive with DC voltage (0.3V<V
ADJ
<1.2V) to adjust output current from 25% to 100% of I
OUTnom
* Drive with PWM signal to adjust output current.
* When driving the ADJ pin above 1.2V, the current will be clamped to 100% brightness
automatically.
Connect resistor R
S
from this pin to V
IN
to define nominal average output current I
OUTnom
=0.1/R
S
Input voltage (6V to 40V). Decouple to ground with 1μF or higher X7R ceramic capacitor close to
device
Description
ADJ
3
I
SENSE
V
IN
4
5
March 2009 Ver1.0
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SN3350
Ordering information
Order Number
SN3350IS05E-01
SN3350IS05E-02
SN3350IP05E-01
SN3350IP05E-02
SN3350
---------
I
S
05
Quantity per reel
3,000
3,000
2,500
2,500
E
- 0X
Bin code
01: bin 1
V
SENSE
=91mV to 101mV
02: bin 2
V
SENSE
=99mV to 110mV
Environmental code
E: ROHS
Pin code
05: 5 pin
Package Type
S:SOT23-5
Operating temperature range
I: Industry Standard
SN3350
----------
I
P
05
E – 0X
Bin code
01: bin
V
SENSE
=91mV to 101mV
02: bin
V
SENSE
=99mV to 110mV
Environmental code
E: ROHS
Pin code
05: 5 pin
Package Type
P:SOT89-5
Operating temperature range
I: Industry Standard
Operating Temperature Range
-40 °C to 85°C
-40 °C to 85°C
-40 °C to 85°C
-40 °C to 85°C
V
SENSE
91mV to 101mV
99mV to 110mV
91mV to 101mV
99mV to 110mV
March 2009 Ver1.0
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SN3350
Absolute maximum ratings
Symbol
V
IN
V
ISENSE
V
LX
V
ADJ
I
LX
P
tot
T
OP
T
ST
T
j MAX
R
θ
JA
Parameter
Input voltage
I
SENSE
voltage
LX output voltage
Adjust pin input voltage
Switch output current
Power dissipation
Operating temperature
Storage temperature
Junction temperature
Junction to ambient
ESD Susceptibility(human body mode)
Rating
-0.3V to +50V
V
IN
+0.3V to V
IN
-5V ,V
IN
>5V
V
IN
+0.3V to -0.3V,V
IN
<5V
-0.3V to +50V
-0.3V to +6V
800mA@SOT89-5;400mA@ SOT23-5
1.2w @SOT89-5;600mw@SOT23-5
-40 to 85°C
-55 to 150°C
150°C
200°C/W @SOT23-5; 45°C/W @SOT89-5
2kV
Electrical characteristics (test conditions: V
IN
=12V, Tamb=25°C unless otherwise stated) (*)
Symbol
V
IN
I
INQoff
I
INQon
V
SENSE
V
SENSEHYS
I
SENSE
V
REF
V
ADJ
V
ADJoff
V
ADJon
R
ADJ
I
LXmean
Input voltage
Quiescent supply current with output off
Quiescent supply current with output
switching
Mean current sense threshold voltage
Sense threshold hysteresis
I
SENSE
pin input current
Internal reference voltage
External control voltage range on ADJ pin
for dc brightness control
DC voltage on ADJ pin to switch chip from
active (on) state to quiescent (off) state
DC voltage on ADJ pin to switch chip from
quiescent (off) state to active (on) state
Resistance between ADJ pin and V
REF
Continuous LX switch current
SOT23-5 package
SOT89-5 package
V
ADJ
falling
V
ADJ
rising
V
SENSE
= 0.1V
Measured on ADJ pin
with pin floating
0.3
0.15
0.2
0.2
0.25
500
0.35
0.65
ADJ pin grounded
ADJ pin floating
SN3350-01
SN3350-02
91
99
Parameter
Conditions
Min.
6
40
60
450
95
105
±15
8
1.2
1.2
0.25
0.3
10
Typ.
Max.
40
80
600
101
110
Unit
V
μA
μA
mV
%
μA
V
V
V
V
KΩ
A
March 2009 Ver1.0
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SN3350
Electrical characteristics (test conditions: V
IN
=12V, Tamb=25°C unless otherwise stated) (*)
(continued)
Symbol
I
LX(leak)
R
LX
D
PWM(LF)
Parameter
LX switch leakage current
LX Switch ‘On’ resistance
Brightness control range at low
frequency PWM signal
Brightness control range at low
frequency PWM signal
PWM frequency =100Hz PWM
amplitude=5V,Vin=15V,
L=27uH, Driving 1 LED
PWM frequency =10KHz PWM
amplitude=5V,Vin=15V,
L=27uH, Driving 1 LED
ADJ pin floating
L=100μH (0.82Ω) I
OUT
=350mA
@ V
LED
=3.4V Driving 1 LED
LX switch ‘ON’
LX switch ‘OFF’
0.9
1200:1
Conditions
Min.
Typ.
Max.
1
1.5
Unit
μA
Ω
D
PWM(HF)
13:1
f
LX
T
ONmin
T
OFFmin
f
LXmax
D
LX
T
PD
T
SD
T
SD-HYS
NOTES:
Operating frequency
Minimum switch ‘ON’ time
Minimum switch ‘OFF’ time
Recommended
maximum
operating frequency
Recommended duty cycle range
of output switch at f
LXmax
Internal comparator propagation
delay
Thermal shutdown temperature
Thermal shutdown hysteresis
154
200
200
1
0.3
0.7
50
140
20
0.9
KHz
ns
ns
MHz
ns
°C
°C
(*) Production testing of the chip is performed at 25
°
C. Functional operation of the chip and parameters specified are guaranteed by design,
characterization and process control in other temperature
March 2009 Ver1.0
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SI-EN Technology
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