LITEON LSP3312

LSP3312
1A LED Driver with Internal Switch
Features
General Description
Simple low parts count
Internal 40V NDMOS switch
1A output current
Single pin on/off and brightness control
Using DC voltage or PWM
Soft-start
High efficiency (up to 97%)
Wide input voltage range ：6V to 40V
The LSP3312 is a continuous mode
inductive step-down converter, designed for
driving single or multiple series connected
LEDs efficiently from a voltage source higher
than the LED voltage. The device operates
from an input supply between 6V and 40V
and provides and externally adjustable
output current of up to 1A. Depending upon
supply voltage and external components,
this can provide up to 30 watts of output
power.
The LSP3312 includes the output switch and
a high-side output current sensing circuit,
which uses and external resistor to set the
nominal average output current.
Output current can be adjusted below the set
values, bye applying an external control
signal to the VSET pin.
The VSET pin will accept either a DC
voltage or a PWM waveform.
The soft-start time can be increased using
an external capacitor from the VSET pin to
ground.
Applying a voltage of 0.2V or lower to the
VSET pin turns the output off and switches
the device into a low current standby state.
Output shutdown
Up to 1MHz switching frequency
Inherent open-circuit LED protection
Typical 5% output current accuracy
Package ： SOT23-5L,ESOP-8L
Applications
Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Typical Application Circuit
D1
Rs
0.3Ω
VIN (6V -40V )
IS EN SE
V IN
LSP3312
LX
V S ET
C1
10uF
L1
100uH
Floating
LSP3312 Rev. Preliminary 0.1
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2010/08/23
LSP3312
1A LED Driver with Internal Switch
Ordering Information
LSP3312-X X X
Output Voltage :
Blank : ADJ
Package :
C5：SOT23-5L
R8：ESOP-8L
Device
Package Code
Package
LSP3312-C5A
LSP3312-R8A
C5
R8
SOT23-5L
ESOP-8L
Packing :
A : Tape & Reel
Tape & Reel
Part Number
Quantity
Suffix
3000
2500
A
A
Pin Assignments
ESOP-8L
(TOP View)
SOT23-5L
(Top View)
LX
5
1
GND
2
VSET
3
4
VIN
ISENSE
VIN
1
ISENSE
2
AGND
3
VSET
4
Exposed
Pad on
Backside
8
PGND
7
PGND
6
LX
5
LX
Pin Descriptions
Pin Number
SOT23-5L
1
2
ESOP-8L
5,6
Name
3
7,8
LX
GND
AGND
PGND
3
4
VSET
4
2
ISENSE
5
1
VIN
9
Exposed
LSP3312 Rev. Preliminary 0.1
Description
Drain of NDMOS switch
Ground
Analog Ground
Power Ground
Multi-function On/Off and brightness control pin:
Leave floating for normal operation.
Drive to voltage below 0.1V to turn off output current
Drive with DC voltage (0.4V < VSET< 2.4V) to adjust output
current from 16% to 100% of IOUT nom
Drive with PWM signal from open-collector or open-drain
transistor, to adjust output current. Adjustment range 1% to
100% of IOUT nom for f < 500Hz
Connect a capacitor from this pin to ground to increase softstart time.
(Default soft-start time = 0.1ms. Additional soft-start time is
approx.1.5ms/nF)
Connect resistor RS from this pin to VIN to define nominal
average output current IOUTnom =0.1/Rs
(Note: RSMIN = 0.1_ with VSET pin open-circuit)
Input voltage (6V to 40V). Decouple to ground with 4.7µF or
higher X7R ceramic capacitor close to device.
This pin has to connect to ground.
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LSP3312
1A LED Driver with Internal Switch
Block Diagram
D1
VIN
L1
Rs
VIN
ISENSE
LX
GM
C1
Preregulator
LDO1
5V
LDO2
5V-Drv
Low voltage
detector
OTP
1.2V
BG
Logic
&
Driver
Ref
VSET
VSET
GND
R2
EN
Internal
Enable
I Limit
R3
Absolute Maximum Ratings
Parameter
Input Voltage Range
LX,ISENSE Pin voltage
VSET Pin voltage
Power Dissipation, PD
Thermal Resistance(Junction to Case),θjC
Thermal Resistance(Junction to
Environment) ,θjA
Storage Temperature Range
Maximum Junction Temperature
SOT23-5L
ESOP-8L
SOT23-5L
ESOP-8L
Value
Unit
-0.3 to 40
-0.3 to 40
-0.3 to 6
V
V
V
mW
°C/W
°C/W
°C/W
°C/W
°C
°C
130
TBD
250
TBD
-65 to +150
150
Recommended Operating Conditions
Parameter
Input Supply Voltage
Operating Junction Temperature
LSP3312 Rev. Preliminary 0.1
Min
Max
Unit
6
-20
36
+125
V
°C
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LSP3312
1A LED Driver with Internal Switch
Electrical Characteristics
(VIN = 16V, TA= 25°C unless otherwise specified.)
Parameter
Input Voltage
Output Current
Shutdown Current
Quiescent Current without switching
Mean current sense threshold
Voltage
Sense threshold hysteresis
Isense pin input current
Vset range on VSET pin
DC voltage on VSET pin to enable
DC voltage on VSET pin to disable
LX switch on resistance
LX switch leakage current
Soft start time
Operating frequency
Recommended minimum switch
ON time
Recommended maximum switch
frequency
Max duty circle
Recommended duty cycle range
Internal comparator propagation delay
Over temperature protection
Temp protection hysteresis
Current limit
Symbol
Test Conditions
VIN
ILED
ISD
IQ
Vsense
VSense_
hys
Isense
Ven
Venon
Venoff
RLX
ILX(leak)
Tss
Min
Typ
6
Rs=0.3Ω
Rs=0.1Ω
VSET pin grounded
VSET pin floating, VIN
Measured on Isense pin with
respect to VIN
Vsense = Vin – 0.1
For DC dimming
Ven rising
Ven falling
@ILX=100mA
Max
Unit
40
V
333
95
mA
20
0.6
40
µA
mA
100
105
mV
13
%
8
1.5
µA
V
V
V
Ω
µA
ms
233
KHz
500
ns
0.3
2.5
0.25
0.2
0.3
5
FLX
Vin=16V, Cen = 1nF
Vi=16V, Vo=9.6V (3 LEDS),
L=47µH, ∆I=0.25A (ILED=1A)
Ton_rec
For 4% accuracy
FLXmax
1.0
MHZ
98
DLX
TPD*
TOTP
25
75
45
150
TOTP_hys
IXLmax Peak inductor current
40
1.5
*parameters are not tested at production, but guaranteed by design.
LSP3312 Rev. Preliminary 0.1
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%
%
ns
℃
℃
A
LSP3312
1A LED Driver with Internal Switch
Application Description
Setting nominal average output current with external resistor Rs
The nominal average output current in the LED(s) is determined by the value of the external
current sense resistor (RS) connected between VIN and ISENSE and is given by:
IOUTnom=
0.1
Rs
The table below gives values of nominal average output current for several preferred values of
current setting resistor (RS) in the typical application circuit shown on page1.
RS (Ω)
Nominal average output current (mA)
0.1
0.13
0.15
0.3
1000
760
667
333
The above values assume that he VSET pin is floating and at a nominal voltage of VREF (1.25V).
Note that Rs=0.1Ω is the minimum allowed value of sense resistor under these conditions to
maintain switch current below the specified maximum value. It is possible to use different values of
Rs if the VSET pin is driven from an external voltage.
Capacitor selection
A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in
series with the supply source impedance and lowers overall efficiency. This capacitor has to supply
the relatively high peak current to the coil and smooth the current ripple on the input supply. A
minimum value of 4.7uF is acceptable if the input source is close the device, but higher values will
improve performance at lower input voltages, especially when the source impedance is high. The
input capacitor should be placed as close as possible toe the IC.
For maximum stability over temperature and voltage, capacitors with X7R,X5R, or better dielectric
are recommended. Capacitors with Y5V dielectric are not suitable for decoupling in this application
and should NOT be used.
Inductor selection
Recommended inductor values for the LSP3312 are in the range 33uF to 100uF. Higher values of
inductance are recommended at higher supply voltages in order to minimize errors due to
switching delays, which result in increased ripple and lower efficiency. Higher values of inductance
also result in a smaller change in output current over the supply voltage range. The inductor should
be mounted as close the to device as possible with low resistance connections toe the LX and VIN
pins. The chosen coil should have a saturation current higher than the peak output current and a
continuous current rating above the required mean output current.
LSP3312 Rev. Preliminary 0.1
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LSP3312
1A LED Driver with Internal Switch
The inductor value should be chosen to maintain operating duty cycle and switch ‘on’/’off’ times
within the specified limits over the supply voltage and load current range. The following equations
can be used as a guide.
LX Switch ‘On’ time
TON=
L∆I
VIN − VLED − ILED( RS + RL + RLX )
LX Switch ‘Off’ time
TOFF=
L∆I
VLED + VD + IlED( RS + RL)
Where: L is the coil inductance; RL is the coil resistance; RS is the current sense resistance IlED is
the required LED current ; ∆I is the coil peak-peak ripple current (Internally set to 0.25 x ILED ); VIN
is the supply voltage; VLED is the total LED forward voltage; RLX is the switch resistance (0.3Ω
nominal); VD is the diode forward voltage at the required load current.
Diode selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance
Schottky diode with low reverse leakage at the maximum operating voltage and temperature. They
also provide better efficiency than silicon diodes, due to a combination of lower forward voltage
and reduced recovery time.
It is important to select parts with a peak current rating above the peak coil current and a
continuous current rating higher than the maximum output load current. It is very important to
consider the reverse leakage of the diode when operating above 85°C. Excess leakage will
increase the power dissipation in the device and if close to the load may create a thermal runaway
condition.
The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will
increase the peak voltage on the LX output. If a silicon diode is used, care should be taken to
ensure that the total voltage appearing on the LX pin including supply ripple, does not exceed the
specified maximum value.
LSP3312 Rev. Preliminary 0.1
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LSP3312
1A LED Driver with Internal Switch
Typical Performance Characteristics
1.Quiescent Current vs Input
2.Shutdown Current vs Input
4.Duty Cycle vs LED Current
(PWM=200Hz)
3.Feedback Voltage vs Vin
5.ILED vs VSET
(VIN=16V,3 LEDs,47uH,Rs=0.15Ω)
LSP3312 Rev. Preliminary 0.1
6.ILED vs VSET
(VIN=16V,3 LEDs,100uH,Rs=0.3Ω)
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LSP3312
1A LED Driver with Internal Switch
Typical Performance Characteristics
(Continued)
7.Steady State Waveforms
8.Start up Waveforms
9.Dimming Waveforms (PWM=50%)
LSP3312 Rev. Preliminary 0.1
10.Pulse skip mode
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LSP3312
1A LED Driver with Internal Switch
Typical Performance Characteristics
(Continued)
11.Efficiency vs Input Voltage
(Rs=0.3Ω,L=100uH)
12.Efficiency vs Input Voltage
(Rs=0.15Ω,L=47uH)
14.Operating Frequency vs Input Voltage
(Rs=0.3Ω,L=100uH)
13.Efficiency vs Input Voltage
(Rs=0.1Ω,L=33uH)
15. Operating Frequency vs Input Voltage
(Rs=0.15Ω,L=47uH)
LSP3312 Rev. Preliminary 0.1
16. Operating Frequency vs Input Voltage
(Rs=0.1Ω,L=33uH)
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LSP3312
1A LED Driver with Internal Switch
Marking Information
SOT23-5L
XXVYW
XX V YW
Date Code
Y：Year(9=2009,0=2010 ,1=2011,2=2012 ...)
W：Week
Week
Code#
Week
Code#
Week
Code#
Week
Code#
1
1
14
E
27
T
40
g
2
2
15
F
28
U
41
h
3
3
16
G
29
V
42
I
4
4
17
H
30
W
43
m
5
5
18
J
31
X
44
n
6
6
19
K
32
Y
45
p
7
7
20
L
33
Z
46
q
8
8
21
M
34
a
47
s
9
9
22
N
35
b
48
t
10
A
23
P
36
c
49
u
11
B
24
Q
37
d
50
v
12 13
C
D
25 26
R
S
38 39
e
f
51 52/53
w
x
Output Voltage
Blank=ADJ
Product Code
AK：LSP3312
ESOP-8L
LOGO
LSC
LSP3312
VYYWWUZ
Part ID
V YYWW UZ
Internal Code
Date code
YY：Year(09=2009,10=2010,11=2011,12=2012...)
WW：Week(01~53)
Output Voltage
Blank:ADJ
LSP3312 Rev. Preliminary 0.1
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LSP3312
1A LED Driver with Internal Switch
Package Information
(All Dimensions in min)
SOT23-5L
SEATING PLANE
D
b
L
E
L1
E1
c
e
L2
e1
M1
A
A2
M2
A1
Symbol
A
A1
A2
b
c
D
E
E1
e
e1
L
L1
L2
∠M1
∠M2
GAUGE PLANE
Min
1.05
0.05
1.00
0.30
0.08
2.80
2.60
1.50
0.30
3°
6°
LSP3312 Rev. Preliminary 0.1
Dimensions In Millimeters
Typ
1.20
0.10
1.10
2.90
2.80
1.60
0.95 BSC
1.90 BSC
0.45
0.60 REF
0.25 BSC
5°
8°
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Max
1.35
0.15
1.20
0.50
0.22
3.00
3.00
1.70
0.55
7°
10°
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LSP3312
1A LED Driver with Internal Switch
Package Information
(All Dimensions in min) (Continued)
H
E
E1
ESOP-8L
D1
θ
L
VIEW “A”
ο
7 (4х)
D
B
C
Symbol
A
A1
A2
B
C
D
D1
E
E1
e
H
L
θ
Dimensions In Millimeters
Min
Nom
Max
1.35
0.05
1.35
0.33
0.19
4.70
3.202
3.80
2.313
5.80
0.38
0ο
ο
A1
e
0.015 х45
A
A2
7ο(4х)
1.60
1.75
0.15
1.55
0.51
0.25
5.10
3.402
4.00
2.513
1.45
0.41
0.20
4.90
3.90
1.27TYP.
5.99
0.71
LSP3312 Rev. Preliminary 0.1
6.30
1.27
8ο
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VIEW “A”
Dimensions In Inches
Min
Nom
Max
0.053
0.063
0..002
0.053
0.057
0.013
0.016
0.0075
0.008
0.185
0.196
0.126
0.148
0.154
0.091
0.050TYP.
0.228
0.236
0.015
0.028
0ο
0.069
0.006
0.061
0.020
0.010
0.200
0.134
0.160
0.099
0.248
0.050
8ο
2010/08/23