Texas Instruments Incorporated AN-2061 User's Guide
AN-2061 LM3445 A19 Edison Retrofit Evaluation Board
1 Introduction
The evaluation board included in this shipment converts 85VACto 135VACinput and drives five to thirteen
series connected LED’s at the currents listed in the Evaluation Board Operating Conditions section. This is
a two-layer board using the bottom and top layer for component placement. The board is surrounded by a
larger area allowing for extra test points and connectors for ease of evaluation. The actual board size is
contained inside the larger outer area and can be cut out for the smallest size possible. The evaluation
board can be modified to adjust the LED forward current and the number of series connected LEDs. The
topology used for this evaluation board eliminates the need for passive power factor correction and results
in high efficiency and power factor with minimal component count which results in a size that can fit in a
standard A19 Edison socket. This board also operates correctly and dims smoothly using most standard
triac dimmers. Output current is regulated within ±15% of nominal from circuit to circuit and over line
voltage variation. For details on the LM3445 IC, see the LM3445 Triac Dimmable Offline LED Driver Data
Sheet (SNVS570).
A bill of materials shown in Table 2 describes the parts used on this demonstration board. A schematic
and layout have also been included along with measured performance characteristics including EMI/EMC
data. The above restrictions for the input voltage are valid only for the demonstration board as shipped
with the schematic below. for detailed information regarding the LM3445 device, see the LM3445 Triac
Dimmable Offline LED Driver Data Sheet (SNVS570). The board is currently set up to drive five to thirteen
series connected LEDs, but the evaluation board may be modified to accept more series LEDs. Refer to
the tables in this document to modify the board to accept more LEDs and/or adjust for different current
levels.
User's Guide
SNVA442C–June 2010–Revised May 2013
2 Evalution Board Operating Conditions
VIN= 85VACto 135V
5 to 13 series connected LEDs as configured with the currents listed below:
• Can drive up to 18 series LEDs (see table)
• I
• I
• I
• I
• I
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= 340 mA (5 LEDs)
LED
= 300 mA (7 LEDs)
LED
= 260 mA (9 LEDs)
LED
= 230 mA (11 LEDs)
LED
= 205 mA (13 LEDs)
LED
AC
SNVA442C–June 2010–Revised May 2013 AN-2061 LM3445 A19 Edison Retrofit Evaluation Board
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1
R15 C15
FLTR2
R2
R7
DIM
R9
COFF
C13
R1
R3
D7
Q1
R8
ASNS
FLTR1
DIM
COFF
FLTR2
BLDR
VCC
GND
GATE
ISNS
LM3445
1
2
3
4
5
10
9
8
7
6
V+
C8
V
CC
R22
D8
R12
R14
+
VLED+
VLED±
L1
C6
D2
V+
LINE NEUTRAL
LINE EMI FILTER
Q4
D4
C4
C3
V
CC
COFF
R16
C12
L2
C2
C
OFF
Current Source
C1
L3
C5
R4
C10
C14
RT1
F1
R6
R24
R5C9
D1
Simplified LM3445 Schematic
3 Simplified LM3445 Schematic
www.ti.com
WARNING
The LM3445 evaluation boards have no isolation or any type of
protection from shock. Caution must be taken when handling
evaluation board. Avoid touching evaluation board, and removing
any cables while evaluation board is operating. Isolating the
evaluation board rather than the oscilloscope is highly
recommended.
This LM3445 evaluation PCB is a non-isolated design. The ground
connection on the evaluation board is NOT referenced to earth
ground. If an oscilloscope ground lead is connected to the
evaluation board ground test point for analysis, and AC power is
applied, the fuse (F1) will fail open. The oscilloscope should be
powered via an isolation transformer before an oscilloscope
ground lead is connected to the evaluation board.
WARNING
2
AN-2061 LM3445 A19 Edison Retrofit Evaluation Board SNVA442C–June 2010–Revised May 2013
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1
4
3
2
10
7
8
9
I
SNS
FLTR1
GATE
BLDR
COFF
V
CC
ASNS
DIM
5 6FLTR2 GND
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4 Pin-Out
Pin No Name Description
1 ASNS PWM output of the triac dim decoder circuit. Outputs a 0 to 4V PWM signal with a duty cycle proportional to
2 FLTR1 First filter input. The 120Hz PWM signal from ASNS is filtered to a DC signal and compared to a 1 to 3V,
3 DIM Input/output dual function dim pin. This pin can be driven with an external PWM signal to dim the LEDs. It
4 COFF OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the
5 FLTR2 Second filter input. A capacitor tied to this pin filters the PWM dimming signal to supply a DC voltage to
6 GND Circuit ground connection.
7 ISNS LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the
8 GATE Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the
9 V
10 BLDR Bleeder pin. Provides the input signal to the angle detect circuitry as well as a current path through a
Figure 1. 10-Pin VSSOP
Table 1. Pin Description 10 Pin VSSOP
the triac dimmer on-time.
5.85 kHz ramp to generate a higher frequency PWM signal with a duty cycle proportional to the triac
dimmer firing angle. Pull above 4.9V (typical) to tri-state DIM.
may also be used as an output signal and connected to the DIM pin of other LM3445 or LED drivers to dim
multiple LED circuits simultaneously.
constant OFF time of the switching controller.
control the LED current. Could also be used as an analog dimming input.
maximum LED current.
buck controller.
Input voltage pin. This pin provides the power for the internal control circuitry and gate driver.
CC
switched 230Ω resistor to ensure proper firing of the triac dimmer.
Pin-Out
SNVA442C–June 2010–Revised May 2013 AN-2061 LM3445 A19 Edison Retrofit Evaluation Board
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Copyright © 2010–2013, Texas Instruments Incorporated
3
LM3445 Evaluation Board Schematic
5 LM3445 Evaluation Board Schematic
www.ti.com
4
AN-2061 LM3445 A19 Edison Retrofit Evaluation Board SNVA442C–June 2010–Revised May 2013
Copyright © 2010–2013, Texas Instruments Incorporated
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