AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
General Description
Applications
These four key elements, AC-to-DC Power
Stage, LED Driver, LED Emitter Module and
Wireless Connectivity block (enabled by
embedded MCU and RF), form a typical
system configuration for Smart Connected
Lighting (SCL) bulbs. AL1794, a four-channel
Constant Current Regulator (CCR) LED driver
with analog and PWM dimming control, is
targeted for Tunable White/Color SCL
applications. Powered by Constant Voltage
(CV) power source(s) provided by an AC-DC
Power Conversion Block, AL1794 generates
Constant Currents (CC) driving attached LED
emitter strings. The channel currents are
further modulated by analog or digital
PWM signals generated by the associated
external MCU.
Key Merits
VLED2 Input Voltage
Input Voltages for
LED1, 2, 3, and 4
3.3V LDO
LED_Bar Connectors
(Top, Male)
MCU1 Connectors
(Bottom, Male)
Cost-Effectiveness
Dimming Performance
Ease of System Implementation
Key Features
Input voltage range: 6.5VDC to 30VDC
4-Channel LED drivers: Independent
Analog or PWM dimming control for
each channel
Reference Current: Adjustable RSET
Low Standby Power with Enable pin
E-flicker free High PWM Frequency
dimming: 0.1%@1KHz, 0.4%@4KHz,
1.0%@10KHz
UVLO, OTP, Open, and Short protection
Operating Temperature Range: -40°C to
+125°C
Low system BOM cost
U-DFN4030-14 “Green” Moulding
Compound package
AL1794EV1 REV1
July 2015
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1-Channel Dimmable SCL Bulbs
2-Channel Tunable White SCL Bulbs
3-Channel Tunable White SCL Bulbs
4-Channel Tunable White+Color SCL
Bulbs
Smart Connected LED Tubes, Panel
Lights, Troffers, and Ceiling Lights
AL1794 EV1 Specifications
Parameter
VLED1 Input Voltage
IC Pin Test points
XYZ Dimension
Value
6.5VDC to 24VDC (Note 1),
connect to Anode of
LEDs strings
Connect to Anode of
LEDs strings if a
separate voltage for
LEDs stings is required
0.25V (Minimum)
150mA (Maximum)
6pins, Power and LED
Inputs
10pins, PWM Signals
Input
16 test points (J3 and
J4)
1.9 ” x 2.0” x 0.6”
Note 1: Vin(max) for AL1794 is capable of up to 30V,
but Vin(max) for AP2204K (3.3V @ 150mA for MCU
Power) limits the Vin(max) of AL1794EV1 Board to
24V only. If higher than 24V is required for testing,
users can drive Vin up to 30V as long as 3.3V power
output from the AP2204K is NOT used.
Page 1 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
AL1794 IC Pin Assignment
Pin
Part Number
Name
U-DFN4030-14
EN
1
PWM4/GND
2
PWM3/GND
3
PWM2/GND
4
PWM1
5
EN
1
14
VIN
PWM4/GND
2
13
REF
PWM3/GND
3
12
FAULTB
PWM2/GND
4
11
LEDPG
PWM1
5
10
LED4/GND
LED1
6
9
LED3/GND
LED2/GND
7
8
GND
Descriptions
Active-high to Enable, Internally Pulled Down
PWM Signal Input for channel 4, Internally Pulled Down for AL1794. GND for AL1791, AL1792,
and AL1793.
PWM Signal Input for channel 3, Internally Pulled Down for AL1793 and AL1794. GND for AL1791
and AL1792.
PWM Signal Input for channel 2, Internally Pulled Down for AL1792, AL1793, and AL1794. GND
for AL1791.
PWM Signal Input for channel 1, Internally Pulled Down (Tied to GND when this channel is NOT
used).
LED1
6
Channel 1 LED Cathode
LED2/GND
7
Channel 2 LED Cathode for AL1792, AL1793, and AL1794. GND for AL1791.
GND
8
Ground
LED3/GND
9
Channel 3 LED Cathode for AL1793 and AL1794. GND for AL1791 and AL1792.
LED4/GND
10
Channel 4 LED Cathode for AL1794. GND for AL1791, AL1792, and AL1793.
LEDPG
11
LED Power Good Indication. Asserted Low to report insufficient headroom. Needs an external pullup resistor.
FAULTB
12
Fault Report. Asserted Low to report faulty conditions. Needs an external pull-up resistor.
REF
13
Reference Current Setting through External Resistor (RSET)
VIN
14
Voltage Input
Exposed pad. Internally connected to GND.
Exposed PAD
Exposed PAD
It should be externally connected to GND and thermal mass for enhanced thermal impedance.
It should not be used as electrical conduction path.
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AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
Evaluation Board
Figure 1: Top View
Figure 2: Bottom View
Connector Pin Definition:
1. Power and Ground Terminals (3 pins)
1) VLED1 - AL1794 VIN, 3.3V LDO Input, and Emitter String Power Input to Anode of
Emitter Strings. – Upper left corner (Top View)
2) VLED2 - Emitter String Power Input to Anode of Emitter Strings.
3) GND - Ground
2. LED_BAR Connectors (6 pins) - (Left to Right Pin Sequence)
1) LED1 (IN) - Connected to Cathode of Emitter String #1 - Right most pin (Top View)
2) LED2 (IN) - Connected to Cathode of Emitter String #2
3) LED3 (IN) - Connected to Cathode of Emitter String #3
4) LED4 (IN) - Connected to Cathode of Emitter String #4
5) VLED1 (OUT) - Emitter String Power Input to Anode of Emitter Strings.
6) VLED2 (OUT) - Emitter String Power Input to Anode of Emitter Strings.
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AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
3. MCU1 Connectors (10 pins) - (Left to Right Pin Sequence)
1) GND Ground - Leftmost pin (Top View)
2) 3.3V (OUT) - 3.3V (output for MCU Power); Generated by AP2204K-3.3 (WIDE INPUT
VOLTAGE
RANGE,
150mA
ULDO
REGULATOR,
http://diodes.com/datasheets/AP2204.pdf) with Vin(max) at 24V.
3) LEDPG (OUT) LED Power Good signal
4) FAULTB (OUT) FaultB, active low, indication of fault occurrence
5) EN (IN) Enable AL1794 to turn ON
6) PWM4 (IN) PWM signal for Channel #4
7) PWM3 (IN) PWM signal for Channel #3
8) PWM2 (IN) PWM signal for Channel #2
9) PWM1 (IN) PWM signal for Channel #1
10) GND
4. Test Points
1) VLED1
Connected to VLED1
2) VLED2
Connected to VLED2
3) GND_1, GND_2, GND_3, GND_4 Connected to GND
4) EN
Connected to AL179x Pin#1
5) PWM4
Connected to AL179x Pin#2
6) PWM3
Connected to AL179x Pin#3
7) PWM2
Connected to AL179x Pin#4
8) PWM1
Connected to AL179x Pin#5
9) LED1
Connected to AL179x Pin#6
10) LED2
Connected to AL179x Pin#7
11) LED3
Connected to AL179x Pin#9
12) LED4
Connected to AL179x Pin#10
13) LEDPG
Connected to AL179x Pin#11
14) FAULTB
Connected to AL179x Pin#12
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Page 4 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
Board Setup Procedure
The channel current ratio for Channel 1, 2, 3 and 4 are fixed at 1:1:0.75:0.25. The default
Channel Current of LED1, LED2, LED3 and LED4, are preset at 250mA, 250mA, 187.5mA and
62.5mA, respectively with Rset (R601) of 12KΩ. Users can change the current setting by
replacing Rset to obtain desired current value as follows:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Ensure that the DC source is switched OFF or disconnected.
Connect the DC line wires of power supply to VIN and GND terminals on the board.
Connect the anode wire of external LED string to VLED1 of the board.
Connect the cathode wire of the external LED emitter strings to relevant LED channels
inputs (LED1, LED2, LED3, LED4) of the board.
Make sure the length of both anode/cathode wires connected between AL1794EV1 and
LEDs strings is minimized (less than 1 inch) to reduce wire inductance and improve ringing
performance.
Ensure that the area around the board is clear and safe, and preferably that the board and
LEDs are enclosed in a transparent safety cover.
Turn on the main DC Power switch.
Send proper PWM Signal pattern and then turn ON the EN pin (High) to enable the
AL1794 IC.
LED strings should light up according to the Dimming pattern driven by PWM signals.
CAUTION:
1. Make sure the maximum DC input voltage is not higher than 30V DC (if 3.3V Power Output
is NOT used), or 24VDC (if 3.3V Power Output is used).
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AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
2. If different current is required, please modify the Rset (R601) to proper value before start
the Turn-On procedure.
3. The maximum recommended channel current is at 500mA (for channel 1 and 2) with Rset
(R601) at 6KΩ.
4. Channel PWM Dimming patterns are recommended to be spread out to avoid sharp turnon and turn-off rush currents.
5. Though there are various protection mechanism built in AL1794, it is good practice to
check maximum dimming pattern to avoid Thermal Shutdown (when Case Ambient
Temperature exceeds 160ºC). Thermal resistivity θja (Junction-to-Ambient) of AL1794 is
55 ºC/Watt. AL1794 will have to absorb any additional voltage headroom provided by the
VLED power input to the Anodes of Emitter Strings. Therefore, thermal management of
AL1794 must follow the following guidelines:
PDmax (Maximum Power Dissipation)
= (160ºC Junction Shutdown Temperature Ambient Temperature, e.g. 85ºC) / 55ºC/W = 1.364Watts
PAmax (Power to be Absorbed by AL179x) = Σ(VLEDx * Current through the emitter
string * Associated PWM Dimming Duty Cycle)
Thermal Management Guideline
AL1794EV1 REV1
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PAmax < PDmax
Page 6 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
PWM Dimming Linearity Tests
Using PWM Dimming signals to create desired dimming effects had the advantages of reducing
current to desired ratio without changing either CCT (Correlated Color Temperate) of White
emitters or causing Color shifts of Color emitters. To avoid eFlicker ("Dark Stripes on Images"
when taking photos or videos with Smartphones under PWM dimmed Lighting situation), users
can use higher PWM frequency (e.g. 4KHz and above). The dimming linearity performance at
Deep Dimming (less than 1% light output) is very important as human eyes are very sensitive
to low light situations.
For example,
10% of measured light is 30% of perceived light
5% of measured light is 22% of perceived light
1% of measured light is 10% of perceived light
0.1% of measured light is 3% of perceived light
Source: IESNA Lighting Handbook, 9th Edition, (New York; IESNA, 2000), 27-4.
AL1794EV1 REV1
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Page 7 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
Dimming Performances: (PWM Frequency 4KHz, 1KHz, and 10KHz)
1. 4KHz PWM Dimming Current Linearity Test for Channel 1, 2, 3 and 4
(250mA:250mA:187.5mA:62.5mA)
Full-Range (0 - 100%) 4KHz PWM Dimming Performance
Figure 3: 4KHz PWM Dimming Performance
Deep Dimming (0 - 10%) 4KHz PWM Dimming Performance
Deep dimming performance of PWM signals are critical performance factor as human
eyes are more sensitive to brightness change at low light level
Figure 4: 4KHz PWM Dimming Performance below 10% Dimming
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Page 8 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
2. 1KHz PWM Dimming Current Linearity Test for Channel 1, 2, 3 and 4
(250mA:250mA:187.5mA:62.5mA)
Full-Range (0 - 100%) 10KHz PWM Dimming Performance
Figure 5: 1KHz PWM Dimming Performance
Deep Dimming (0 - 10%) 1KHz PWM Dimming Performance
Using 1KHz PWM signal (vs. 4KHz) will further improve Deep Dimming Linearity
performance.
Figure 6: 1KHz PWM Dimming Performance below 10% Dimming
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Page 9 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
3. 10KHz PWM Dimming Current Linearity Test for Channel 2
Full-Range (0 - 100%) Dimming Performance
Figure 7: 10KHz PWM Dimming Performance
Deep Dimming (0 - 10%) 10KHz PWM Dimming Performance
Figure 8: 10KHz PWM Dimming Performance 0%-10% Dimming
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Page 10 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
Evaluation Board Schematic
VLED2'
VLED2
VLED1'
VLED1
GND_1 GND_2 GND_3 GND_4
U681 AP2204K
3.3V
C602
100uF/50V
1
3
R602
10K
MCU1
EN
PWM4
PWM3
PWM2
PWM1
GND2
1
3.3V
4
ADJ/NC
C682
4.7uF/10V
JP_EN
PWM1
PWM2
PWM3
PWM4
EN
LEDPG FAULTB
2
3
C621
1uF
4
5
1
6
2
7
3
8
4
9
5
10
6
VIN
PWM4
REF
PWM3
FAULTB
PWM2
LEDPG
PWM1
LED4
LED1
LED2
GD
7
EN
PGND
FAULTB
EN
C681
1.0uF/50V
5
2
3.3Vcc
LEDPG
R608
10K
VOUT
1
3.3V
GND1
R607
10K
VIN
GND
C601
100uF/50V
2
GND
J3
EN
R601 / LED1 / LED2 / LED3 /LED4
PWM4
12K
/ 250mA/250mA /187mA /62mA
PWM3
10K
/ 300mA/300mA /225mA /75mA
PWM2
9K
/ 333mA/333mA /250mA /83mA
PWM1
6K
/ 500mA/500mA /375mA /125mA
LED1
LED2
GND
1
14
C603
13
LED3
R601
0.1uF
6
RES
5
12
4
11
3
10
2
9
1
8
GND
J4
1
U601
AL1794
2
2
3
3
4
4
LED4
5
5
LED3
6
6
LED1
7
7
LED2
8
VLED2
VLED1
LED4
LED3
LED2
LED1
CON3 LED Board
VIN
REF
FAULTB
LEDPG
LED4
LED3
GND
GND'
8
Figure 9: Evaluation Board Schematic
Title
AP1794 Test Fixture
Size
A4
Date:
AL1794EV1 REV1
July 2015
www.diodes.com
Document Number
Rev
2.0
AL179x Test Fixture Rev_2.0
Tuesday , February 17, 2015
Sheet
1
of
1
Page 11 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
Bill of Material
#
1
2
Name
U601
U681
QTY
1
1
Part number
AL1794AFE-13
AP2204K-3.3VTRG1
Manufacturer
Diodes Inc
Diodes Inc
Description
4-Channel LED Driver
Wide-Input (2.5V-24V) 150mA ULDO
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C601
C602
C603
C621
C681
C682
R601 (Rset)
R602
R607
R608
JP_EN
LED_BAR
MCU1
VLED1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
ECA-1HM101
ECA-1HM101
CC0603KRX7R9BB104
CC0805KRX7R9BB104
CC0805KRX7R9BB104
CC0805ZRY5V6BB475
RC0603JR-0712KL
RC0603JR-0710KL
RC0603JR-0710KL
RC0603JR-0710KL
800-10-002-10-001000
800-10-006-10-001000
800-10-010-10-001000
534-1598-2
Panasonic
Panasonic
Yageo
Yageo
Yageo
Yageo
Yageo
Yageo
Yageo
Yageo
Mill-Max
Mill-Max
Mill-Max
Mouser
E-CAP 100uF 50V (8x11.5mm)
E-CAP 100uF 50V (8x11.5mm)
CAP CER 0.1uF 50V X7R 0603
CAP CER 1.0uF 50V X7R 0805
CAP CER 1.0uF 50V X7R 0805
CAP CER 4.7uF 10V X7R 0805
RES 12KΩ 1/10W 5% 0603 SMD
RES 10KΩ 1/10W 5% 0603 SMD
RES 10KΩ 1/10W 5% 0603 SMD
RES 10KΩ 1/10W 5% 0603 SMD
Enable 2 pin SIP header w/Jumper
LED Emitter Output I/O 6pin SIP header
MCU I/O 10pin SIP header
VLED1 Anode Input, Term 0.094”x1/16”
1
1
534-1598-2
534-1598-2
Mouser
Mouser
VLED2 Anode Input, Term 0.094”x1/16”
Ground Input, Term 0.094”x1/16”
17 VLED2
18 GND
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Page 12 of 13
AL1794EV1 User Guide
Quad-Channel Current-Ratio-Optimized LED Driver
with Analog and PWM Dimming
IMPORTANT NOTICE
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DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other
changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any
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convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products
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companies whose products are represented on Diodes Incorporated website, harmless against all damages.
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized
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Products described herein may be covered by one or more United States, international or foreign patents pending. Product names
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This document is written in English but may be translated into multiple languages for reference. Only the English version of this
document is the final and determinative format released by Diodes Incorporated.
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Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems
without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided
in the labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected
to cause the failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or
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concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems,
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Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes
Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2015, Diodes Incorporated
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