IS31LT3938 T8 Lighting DEMO Board Guide

IS31LT3938 T8 Lighting DEMO Board Guide
Description
IS31LT3938 LED driver IC is a peak current
detection buck converter which operates in
constant off time mode. It operates over a very
wide input voltage supply range of 10VDC to
450VDC or 110VAC/220VAC.
IS31LT3938 incorporates the special feature
of power sequencing by detecting OFF-ON
cycles of the main power switch. When the
switch is cycled within a 4 second period
(typical) the device automatically switches the
power sequencing level to the next step. As a
result, power sequencing can be achieved
without replacing any wiring in the original
system. There are multiple modes of power
sequencing that the user may configure, 2
steps or 3 steps, as well as different levels of
power sequencing via the external pins DIM1
and DIM2.
Features







User configurable power sequencing
levels
3% output current accuracy
Over current, voltage and temperature
protection
High efficiency (typical up to 95%)
Wide
input
voltage
range:
10VDC-450VDC or 85Vac-265Vac
Linear and PWM dimming
Very few external components

LED array(12 LEDs in series)
Recommended Input and Output Ratings


Input: 85~265VAC
Output: 12LEDs in series(38V)/410mA
Absolute Maximum Ratings
≤ 265VAC power supply
≤ 42V Vout (Total Vf)
Caution: Do not exceed the conditions listed above,
otherwise the board will be damaged or the output
will be limited.
Procedure
The IS31LT3938 DEMO Board is fully
assembled and tested. Follow the steps listed
below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
1) Connect the positive terminal of the LEDs
to the LED+ pin of the DEMO and the
negative terminal of the LEDs to the LEDpin of the DEMO.
2) Connect the input pins (L and N) of the
DEMO via the main power switch to AC
power supply.
3) Turn on the power supply.
Detailed description
Switchable Power Levels
Applications



DC/DC or AC/DC LED driver applications
Signal and decorative LED lighting
backlighting LED driver
Order information
Part Number
Package Type
IS31LT3938-GRLS2-EBT8
SOP-8
Quick Start
Recommended Equipment

85~265VAC/50~60Hz power supply
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
The action of the main power switch can be
divided into two types. The first is “normal
switch operation” wherein the switch is
toggled from ON to OFF, remaining OFF for
longer than 4 seconds (typical). The other is
“power sequencing action” wherein the switch
is toggled from ON to OFF and back ON
within 4 seconds (typical).
When the device experiences normal switch
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IS31LT3938 T8 Lighting DEMO Board Guide
operation, it merely powers on in the first state
when the power switch is toggled to ON, and
the device turns off when the main power
switch is changed to OFF.
Power sequencing output current levels are
configured by connecting the DIM1 and DIM2
pins as indicated in the table below：
DIM1
DIM2
Power sequencing levels
Floating
Floating
No Power Sequencing
Floating
GND
2levels：100%-30%-100%
GND
Floating
2levels：100%-50%-100%
GND
GND
3levels:100%-50%-20%-100%
When operating the power switch normally the
device will always power up at 100% output
current.
The operation of the power switch and the
configuration of the DIM1 and DIM2 pins
control the power sequencing process as
follows：
1. When DIM1 and DIM2 pins are both
floating, there is no power sequencing,
and the output current is 100% of the
programmed value when the power is on.
2. When DIM1 is floating and DIM2 is GND,
the output current is：
a) 100% at power on.
b) The first power sequencing action
causes the current to change to 30%.
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
c) A second power sequencing action
causes the current to return to 100%.
d) A fourth power sequencing action has
the same effect as the first power
sequencing action.
e) Subsequent power sequencing actions
causes the cycle to continue.
3. When DIM1 is GND and DIM2 is floating,
the power sequencing is as described in (2)
above, except that the current sequencing
is 100%-50%-100%.
4. When both DIM1 and DIM2 are connected
to GND, the power sequencing is as
described in (2) above, except that the
current
sequencing
is
100%-50%-20%-100%.
If the switch is operated normally, that is,
switched on once after being in the OFF
position for a long time, or if both the DIM1
and DIM2 pins are floating, then the output
current always starts up at the initial value of
100%.
Note: Because the main power switch is used
to initiate the power sequencing function, the
device must have a large enough external
capacitor on VIN to maintain device operation
for 4 seconds. Please refer to the
Applications Examples for specific values.
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IS31LT3938 T8 Lighting DEMO Board Guide
Bill of Materials
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Name
Fuse
X Cap
AL Cap
CBB Cap
AL Cap
SMD Cap
SMD Cap
Inductor
Shielded SMD
Inductor
EPC-13 Inductor
Rectifying Bridge
Zener Diode
FR Diode
Resistor
Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
SMD Resistor
NMOS
PCB
IC
Description
1A,250V,3*10
0.1uF, 275V
33uF±10%,250V
10nF±20%,630V
10uF±10%,400V
10uF±10%,25V,0805
10nF±10%,50V,0805
3mH±10%,8*10mm,Isat≥200mA
Ref Des.
F1
C3,C5
C1,C6
C4
C2
C7
C8
L1,L2
Qty.
1
2
2
1
1
1
1
2
Cost(RMB)
0.1
0.3
0.4
0.15
0.2
0.1
0.04
0.3
4.7uH±10%,5.6*5.6mm,Isat≥1A
L5
1
0.3
0.65mH±5%,Isat≥700mA,EPC-13
1A,1000V,M7,SMA
12V,0.25W,LL-34
1A,600V,ES1J,SMA
NC
220KΩ±5%,1W
NC
300KΩ±1%,0805
7.5MΩ±1%,1206
2.4MΩ±1%,1206
47Ω±5%,0805
1KΩ±1%,0805
1.0Ω±1%,1206
1.2Ω±1%,1206
1.8Ω±1%,1206
4N60,4A/600V,TO-251
230mm x 17mm
IS31LT3938,SOP-8
Total Cost(Exclude IC)
L3,L4
D1-D3,D5-D8
D13
D4,D11
R2,R3
R4,R5
R10,R11
R12
R1
R6
R8
R9
R13
R14
R15
Q1
2
7
1
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1.5
0.35
0.1
0.3
0
0.02
0
0.006
0.008
0.008
0.006
0.006
0.008
0.008
0.008
1.5
0.8
U1
6.518
Note: 1. If the input voltage is single voltage(85~130VAC or 178~265VAC), L5 and D11 can be removed
(short the L5 and eliminate D11) and the efficiency will be higher.
2. If adding the opto-couple as the open output voltage limitation, C2 can use 63V tolerance rating to
saving size and decreasing the output current ripple.
Figure 1. Picture of DEMO Board
NOTE: Physical dimensions are (L x W x H): 230mm x 17mm x 12mm
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
3
IS31LT3938 T8 Lighting DEMO Board Guide
Figure 2. Schematic of DEMO
Board
Figure 3 PCB Layout- Top Layer
Figure 4 PCB Component Placement Guide - Top Layer
Figure 5 PCB Layout- Bottom Layer
Test result
Input
voltage(VAC)
Input
power(W)
PF
Output
current(mA)
Output
voltage(V)
Output
power(W)
Efficiency(%)
85
18.64
0.869
424
38.6
16.37
87.80
90
18.37
0.881
420
38.6
16.21
88.25
100
18.09
0.887
419
38.5
16.13
89.17
110
17.99
0.881
418
38.5
16.09
89.46
120
17.94
0.873
417
38.5
16.05
89.49
130
17.94
0.866
418
38.5
16.09
89.70
180
18.07
0.835
419
38.4
16.09
89.04
200
18.1
0.825
418
38.4
16.05
88.68
220
18.13
0.812
418
38.4
16.05
88.53
240
18.28
0.800
417
38.4
16.01
87.60
265
18.42
0.786
415
38.4
15.94
86.51
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
4
IS31LT3938 T8 Lighting DEMO Board Guide
EMI test
Figure 6. L line
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
5
IS31LT3938 T8 Lighting DEMO Board Guide
Figure 7. N line
Copyright © 2011 integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products
at any time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein.
Customers are advised to obtain the latest version of this device specification before relying on any published information and before placing
orders for products.
Integrated Silicon Solution, Inc. – www.issi.com
R1.0, 9/29/2012
6