ZLED7330 [IDT]
High Current 40V LED Driver with Switch Dimming;
| 型号： | ZLED7330 |
| 厂家： | 
INTEGRATED DEVICE TECHNOLOGY |
| 描述： | High Current 40V LED Driver with Switch Dimming |
| 文件： | 总22页 (文件大小：615K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ZLED7x30
High Current 40V LED Driver
with Switch Dimming
Datasheet
Brief Description
Features
• Switch dimming with multiple levels
The ZLED7x30 continuous-mode inductive step-
down converter family is one of our ZLED LED-
control ICs. It is designed for applications requiring
high brightness and high current. The ZLED7x30
can efficiently drive a single LED or multiple
series-connected LEDs from a voltage input higher
than the LED forward voltage (Vin = 8.5 to
40VDC). It provides an adjustable output current
(1.2A maximum), which is set via an external
resistor and controlled by the ZLED7x30’s
integrated high-side output current-sensing circuit
and high speed internal 40V power switch. Its low
conducting impedance ensures high system effi-
ciency.
• Three modes for output level settings
• Up to 1.2A output current
• Internal 40V power switch
• Wide DC input voltage range 8.5 to 40 VDC
• Output current accuracy: 5% (typical)
• LED open-circuit protection
• Thermal shutdown protection
Benefits
• High efficiency: up to 98%
• Very few external components needed for
operation
The ZLED7x30 provides a switch dimming func-
tion. It detects external switch action to adjust out-
put current, allowing dimming functionality to be
achieved without changing the original lighting sys-
tem circuitry.
• Adds switch dimming function to existing
installation
Available Support
• Evaluation Kit
The switch dimming is implemented in either two-
level mode or three-level mode. The output current
of every level and the total number of levels are
customer selected by setting the corresponding
input conditions of DIM1 and DIM2 pin.
Physical Characteristics
• Operating temperature: -40°C to 105°C
• Switching frequency: up to 1MHz
• SOP-8 package
The ZLED7x30 enables diverse industrial and
consumer lighting applications requiring high
driving currents, wide operating voltage range,
high efficiency, and variable brightness control. It
offers over-temperature and LED open-circuit
protection. The ZLED7x30 can also minimize bill-
of-material costs because very few external
components are required for most applications.
Only a resistor, a diode, an inductor, and three
ZLED7x30 Family Selection Matrix
Product
ZLED7030
ZLED7330
ZLED7530
ZLED7730
Max. Current Output
Package
SOP-8
SOP-8
SOP-8
SOP-8
1.2A
1.0A
0.75A
0.35A
capacitors are needed for
application.
a
typical basic
ZLED7x30 Typical Application Circuit
Rs
Switch
D1
Vs = 8.5 to 40 VDC
(C3)
LED
String
Vin
I SENSE
L1
33 to 220 µH
ZLED7x30
C1
≥220µF
C2
0.1µF
LX
DIM1
DIM2
GND/Floating
GND/Floating
GND
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30
High Current 40V LED Driver
with Switch Dimming
Datasheet
ZLED7x30 Block Diagram
6 to 40 VDC
VS
Rs
D1
ISENSE
2
(C1)
C2
0.1µF
VCC
(C3)
n LED
VDDA
1
Power
Supply,
Oscillator
and
Under-
Voltage
VDDD
VIN
L1
8
VCC
ISENSE
VREF
33µH to
220µH
VIN
LX
Power
MOS
UV
Detection
(UV)
ISENSE
And
Driver
DR
POR
CLK
SD
SD
S
SD
Dim
Select
Shut-
down
Analog
Dim
Logic
6
Trim
DIM1
DIM2
ZLED7x30
5
7
GND
Typical Applications
Illuminated LED signs and other displays
LED street and traffic lighting (low voltage)
Architecture/building LED lighting
LED backlighting
Interior/exterior LED lighting
MR16 LED spot lights
Retrofit LED lighting fixtures
General purpose industrial and consumer LED applications
Ordering Information
Product Sales Code Description
Package
ZLED7030ZI1R
ZLED7330ZI1R
ZLED7530ZI1R
ZLED7730ZI1R
ZLED7030KIT-D1
ZLED-PCB8
ZLED7030 – High Current (1200mA) 40V LED Driver with Switch Dimming
ZLED7330 – High Current (1000mA) 40V LED Driver with Switch Dimming
ZLED7530 – High Current (750mA) 40V LED Driver with Switch Dimming
ZLED7730 – High Current (350mA) 40V LED Driver with Switch Dimming
ZLED7030-D1 Demo Board, 1 ZLED-PCB8 and 5 ZLED7030 ICs
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
Kit
Test PCB with one 5W white High Brightness (HB) LED, cascadable to one
multiple LED string
Printed Circuit Board (PCB)
Corporate Headquarters
6024 Silver Creek Valley Road
San Jose, CA 95138
Sales
Tech Support
www.IDT.com/go/support
1-800-345-7015 or 408-284-8200
Fax: 408-284-2775
www.IDT.com/go/sales
www.IDT.com
DISCLAIMER Integrated Device Technology, Inc. (IDT) reserves the right to modify the products and/or specifications described herein at any time, without notice, at IDT's sole discretion. Performance
specifications and operating parameters of the described products are determined in an independent state and are not guaranteed to perform the same way when installed in customer products. The
information contained herein is provided without representation or warranty of any kind, whether express or implied, including, but not limited to, the suitability of IDT's products for any particular purpose, an
implied warranty of merchantability, or non-infringement of the intellectual property rights of others. This document is presented only as a guide and does not convey any license under intellectual property
rights of IDT or any third parties.
IDT's products are not intended for use in applications involving extreme environmental conditions or in life support systems or similar devices where the failure or malfunction of an IDT product can be
reasonably expected to significantly affect the health or safety of users. Anyone using an IDT product in such a manner does so at their own risk, absent an express, written agreement by IDT.
Integrated Device Technology, IDT and the IDT logo are trademarks or registered trademarks of IDT and its subsidiaries in the United States and other countries. Other trademarks used herein are the
property of IDT or their respective third party owners. For datasheet type definitions and a glossary of common terms, visit www.idt.com/go/glossary. All contents of this document are copyright of Integrated
Device Technology, Inc. All rights reserved.
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
Contents
1
IC Characteristics.......................................................................................................................................................... 5
1.1
Absolute Maximum Ratings ................................................................................................................................... 5
Operating Conditions ............................................................................................................................................. 5
Electrical Parameters............................................................................................................................................. 6
Typical Operation Graphs...................................................................................................................................... 7
1.2
1.3
1.4
2
Circuit Description ....................................................................................................................................................... 12
2.1
ZLED7x30 Overview............................................................................................................................................ 12
Control of Output Current via External Sense Resistor Rs .................................................................................. 12
Multi-Mode Switch Dimming................................................................................................................................. 12
ZLED7x30 Protection Features............................................................................................................................ 13
Thermal Shut-down Protection ..................................................................................................................... 13
LED Open-Load Protection........................................................................................................................... 13
2.2
2.3
2.4
2.4.1
2.4.2
3
Application Circuit Design............................................................................................................................................ 14
3.1
3.2
3.2.1
3.2.2
3.3
Applications.......................................................................................................................................................... 14
Thermal Considerations for Application Design................................................................................................... 15
Temperature Effects of Load, Layout, and Component Selection................................................................. 15
Temperature Effects of Low Supply Voltage VIN ........................................................................................... 15
External Component Selection............................................................................................................................. 15
Sense Resistor Rs........................................................................................................................................ 15
Inductor L1.................................................................................................................................................... 16
Bypass Capacitor C1.................................................................................................................................... 17
De-bouncing Capacitor C2............................................................................................................................ 19
Capacitor C3 for Reducing Output Ripple..................................................................................................... 19
Diode D1....................................................................................................................................................... 19
Application Circuit Layout Requirements ............................................................................................................. 19
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.4
4
5
6
7
ESD Protection............................................................................................................................................................ 20
Pin Configuration and Package................................................................................................................................... 20
Ordering Information ................................................................................................................................................... 21
Document Revision History......................................................................................................................................... 22
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ZLED7x30 Datasheet
List of Figures
Figure 1.1
Figure 1.2
Figure 1.3
Figure 1.4
Figure 1.5
Figure 1.6
Figure 1.7
Figure 1.8
Figure 3.1
Figure 3.2
Figure 3.3
Figure 5.1
ZLED7x30 Supply Operating Current vs. Input Supply Voltage (VIN = 8.5 to 40V)......................................... 7
Efficiency (%) vs. Input Supply Voltage (VIN = 8.5 to 40V) Per Number of LEDs (Rs=0.10Ω, L1=47μH)........ 7
Efficiency vs. Input Supply Voltage (VIN = 8.5 to 40V) Per Number of LEDs (Rs=0.15Ω, L1=47μH).............. 8
Efficiency vs. Input Supply Voltage (VIN = 8.5 to 40V)‡ Per Number of LEDs (Rs=0.30Ω, L1=47μH)............. 8
Output Current Variation vs. Input Supply Voltage (VIN = 8.5 to 40V) Per Number of LEDs (Rs=0.15Ω, L1=47μH)9
Sense Voltage vs. Operating Temperature (Rs=0.10Ω, L1=47μH, VIN = 40 V) .............................................. 9
Switch Dimming Waveform (Dimming Mode 2)............................................................................................ 10
LED Open-Circuit Protection (Rs=0.30Ω, L1=47μH, VIN = 24 V).................................................................. 11
ZLED7x30 Application Circuit for Switch Dimming ....................................................................................... 14
Basic ZLED7x30 Application Circuit with Output Current Determined only by Rs........................................ 14
ZLED7x30 Application Circuit using a Halogen Electronic Transformer to Operate with AC Line Supply .... 15
ZLED7x30 Pin Configuration........................................................................................................................ 20
List of Tables
Table 2.1
Table 3.1
Table 5.1
Table 5.2
Dimming Configuration Options.................................................................................................................... 13
Recommended Values for Sense Resistor Rs.............................................................................................. 16
ZLED7x30 Pin Descriptions—SOP-8 Package............................................................................................. 20
Package Dimensions SOP-8........................................................................................................................ 21
© 2016 Integrated Device Technology, Inc.
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ZLED7x30 Datasheet
1
IC Characteristics
Note: Exceeding the maximum ratings given in this section could cause operation failure and/or cause permanent
damage to the ZLED7x30. Exposure to these conditions for extended periods may affect device reliability.
1.1 Absolute Maximum Ratings
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
1.1.1
Input voltage (also see
specification 1.2.2)
VIN
-0.3
50
V
1.1.2
ISENSE pin voltage
VISENSE
VIN≥5V
VIN-5V
-0.3V
-0.3
VIN+0.3V
V
V
V
V
VIN<5V
VIN+0.3V
1.1.3
1.1.4
LX pin output voltage
VLX
50
6
DIM1, DIM2 pin input
voltage
VDIM
-0.3
1.1.5
1.1.6
1.1.7
1.1.8
1.1.9
LX pin switch output current
Power dissipation
ILX
1.5
0.5
A
W
Ptot
ESD performance
Human Body Model
±3
kV
°C
Junction temperature
TJ
150
100
Junction to ambient thermal
resistance
K/W
RθJA
1.1.10 Storage temperature
TS
-55
150
°C
1.2
Operating Conditions
No.
1.2.1
1.2.2
PARAMETER
SYMBOL
Tamb
CONDITIONS
MIN
-40
8.5
TYP
MAX
105
40
UNIT
°C
Operating temperature
Input voltage (also see
specification 1.1.1)
VIN
V
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
1.3
Electrical Parameters
Except as noted, test conditions for the following specifications are Tamb = 25°C typical and VIN = 12V unless
otherwise noted.
Production testing of the chip is performed at 25°C unless otherwise stated. Functional operation of the chip and
specified parameters at other temperatures are guaranteed by design, characterization, and process control.
No.
PARAMETER
SYMBOL
IINQoff
CONDITIONS
Output off
MIN
TYP
120
450
100
MAX
140
600
105
UNIT
μA
1.3.1
Quiescent supply current
70
IINQon
Output switching
μA
1.3.2
Mean current sense
threshold voltage
VSENSE
95
mV
1.3.3
1.3.4
1.3.5
Sense threshold hysteresis
ISENSE pin input current
VSENSEHYS
ISENSE
±15
8
%
μA
V
VSENSE = VIN -0.1V
VIN rising
Under-voltage lockout
threshold
VUVLO
5.05
5.85
6.65
1.3.6
1.3.7
Under-voltage lockout
hysteresis
1.65
V
∆VUVLO
Ratio of output current
level to initial current in
Dimming Mode 1
K1
DIM1: Floating
DIM2: GND
Level 1
Level 2
Level 3
Level 1
Level 2
Level 3
Level 1
100
50
%
%
%
%
%
%
%
17
20
23
1.3.8
1.3.9
Ratio of output current
level to initial current in
Dimming Mode 2
K2
DIM1: GND
DIM2: Floating
100
60
28
28
30
32
32
Ratio of output current
level to initial current in
Dimming Mode 3
K3
TS
DIM1: GND
DIM2: GND
100
Level 2
30
2
%
s
1.3.10
1.3.11
Interval time between
external switch actions
LX switch continuous
current
ILXmean_0
ILXmean_3
ILXmean_5
ILXmean_7
ILX(leak)
RLX
ZLED7030
ZLED7330
ZLED7530
ZLED7730
1.2
1.0
0.75
0.35
1
A
A
A
A
1.3.12
1.3.13
1.3.14
1.3.15
1.3.16
LX switch leakage current
LX switch on resistance
Minimum switch on time
Minimum switch off time
μA
Ω
0.3
200
200
0.4
tONmin
LX switch on
LX switch off
ns
ns
tOFFmin
fLXmax
Recommended operating
frequency maximum
1
MHz
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
1.3.17
Recommended output
switch duty cycle range
at fLXmax
DLX
0.3
0.9
1.3.18
1.3.19
1.3.20
Propagation delay of
internal comparator
tPD
TSD
25
150
20
ns
°C
K
Thermal shutdown
temperature
Thermal shutdown
hysteresis
TSD-HYS
1.4
Typical Operation Graphs
The curves are valid for the typical application circuit and Tamb = 25°C unless otherwise noted.
Figure 1.1 ZLED7x30 Supply Operating Current vs. Input Supply Voltage (VIN = 8.5 to 40V)
600
500
400
300
200
100
0
5
10
15
20
25
30
35
40
Vin(V)
Figure 1.2
Efficiency (%) vs. Input Supply Voltage (VIN = 8.5 to 40V)† Per Number of LEDs (Rs=0.10Ω, L1=47μH)
1
0.95
0.9
Rs=0.10Ω
1LED
3LED
7LED
10LED
0.85
0.8
0.75
0.7
0.65
0.6
5
10
15
20
25
30
35
40
Vin(V)
† Minimum V depends on number of LEDs.
in
© 2016 Integrated Device Technology, Inc.
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ZLED7x30 Datasheet
Figure 1.3
Efficiency vs. Input Supply Voltage (VIN = 8.5 to 40V)‡ Per Number of LEDs (Rs=0.15Ω, L1=47μH)
1
0.95
0.9
Rs=0.15Ω
1LED
3LED
7LED
10LED
0.85
0.8
0.75
0.7
0.65
0.6
5
10
15
20
25
30
35
40
Vin(V)
Figure 1.4
Efficiency vs. Input Supply Voltage (VIN = 8.5 to 40V)‡ Per Number of LEDs (Rs=0.30Ω, L1=47μH)
1
Rs=0.30Ω
1LED
0.95
0.9
3LED
0.85
0.8
7LED
10LED
0.75
0.7
0.65
0.6
5
10
15
20
25
30
35
40
Vin(V)
‡ Minimum V depends on number of LEDs.
in
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April 20, 2016
ZLED7x30 Datasheet
Figure 1.5
Output Current Variation vs. Input Supply Voltage (VIN = 8.5 to 40V)§ Per Number of LEDs
(Rs=0.15Ω, L1=47μH)
0.7
0.69
0.68
0.67
0.66
0.65
0.64
0.63
0.62
0.61
0.6
Rs=0.15Ω
1LED
3LED
7LED
10LED
5
10
15
20
25
30
35
40
Vin(V)
Figure 1.6
Sense Voltage vs. Operating Temperature (Rs=0.10Ω, L1=47μH, VIN = 40 V)
99.4
99.2
99.0
98.8
98.6
98.4
98.2
98.0
97.8
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110
Temperature (°C)
§ Minimum V depends on number of LEDs.
in
© 2016 Integrated Device Technology, Inc.
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ZLED7x30 Datasheet
Figure 1.7 demonstrates a typical switch dimming waveform. Channel 1 (blue) is the supply voltage. Channel 4
(magenta) shows the output current at 100%, then 60%, and then 30%.
Figure 1.7
Switch Dimming Waveform (Dimming Mode 2)
100%
60%
30%
Timebase -1.04 s Trigger C1 DC
Roll
1.00s/div Stop
-150mV
500kS
50 kS/s Edge Negative
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
Figure 1.8
LED Open-Circuit Protection (Rs=0.30Ω, L1=47μH, VIN = 24 V)
Timebase
Roll
500kS
-5.2 s Trigger C1 DC
5.00s/div Stop 15.0V
10 kS/s Edge Negative
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
2
Circuit Description
2.1
ZLED7x30 Overview
The ZLED7x30 is a continuous-mode inductive step-down converter LED driver for driving single or multiple series-
connected LEDs from a voltage input higher than the LED voltage (Vin = 8.5 to 40VDC; see section 3.2.2 for
important details). The ZLED7x30 provides an adjustable output current (1.2A maximum for ZLED7030; 1.0A
maximum for ZLED7330; 0.75A maximum for ZLED7530; 0.35A maximum for ZLED7730) , which is nominally set via
an external sense resistor Rs and controlled by the ZLED7x30’s integrated high-side output current-sensing circuit
and output switch. The ZLED7x30 detects external switching action on the supply line to adjust the output current in
different modes on different levels.
Only a resistor, a diode, an inductor, and three capacitors are needed for a typical basic application. Refer to the
application circuits in section 3 for the location of the components referred to in the following sections.
2.2
Control of Output Current via External Sense Resistor Rs
External sense resistor Rs, which is connected between the VIN and ISENSE pins as shown in Figure 3.1, sets IOUTnom
,
the nominal average output current. Equation (1) can be used to calculate the nominal output current, which is the LX
switch output current ILX if no switch dimming condition is valid. See section 3.3.1 for recommended values for Rs in a
typical basic application and section 3.4 for layout guidelines for Rs.
0.1V
IOUTnom
=
(1)
Rs
2.3
Multi-Mode Switch Dimming
The ZLED7x30 detects external switching action on the supply line to adjust output current, allowing dimming
functionality to be achieved without changing the original lighting system circuitry. The switch dimming is implemented
in either two-level mode or three-level mode. The output current of each level and the total number of levels are
customer selected by setting the corresponding input conditions on the DIM1 and DIM2 pins. See page 1 for a typical
application using the DIM1 and DIM2 pins.
The output current is set at the initial 100% value determined by the sense resistor Rs the first time that power is
supplied to the chip. After the initial power up sequence, the chip adjusts the output current according to the external
switch action. After the lowest current level, the current cycles back to the initial value if subsequent switch action is
detected. If the power is switched off for longer than 2 seconds, the device will return to its initial state and the output
current will be set to the initial value the next time that power is applied.
There are two types of switch action: a normal switch, which has an off-time between each subsequent switch action
longer than 2s, and a dimming switch, which has an off-time between each subsequent switch less than 2s.
© 2016 Integrated Device Technology, Inc.
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ZLED7x30 Datasheet
The dimmed average output current is given by
0.1V
(2)
IOUT dim = KX
∗
Rs
Where
KX = Current ratio to initial current (see section 1.3).
The input conditions on the DIM1 and DIM2 pins set the number of current levels and the current ratio relative to the
initial average current for the dimming switch (DS) sequences as shown in Table 2.1.
Table 2.1
Dimming Configuration Options
Dimming Mode
DIM1
Floating
Floating
GND
DIM2
Floating
GND
Dimming Ratio K
No dimming
(100%)
100% 1st DS 50% 2nd DS 20% 3rd DS 100% …
100% 1st DS 60% 2nd DS 30% 3rd DS 100% …
100% 1st DS 30% 2nd DS 100% …
1
2
3
Floating
GND
GND
If a normal switch is detected or if DIM1 and DIM2 are both floating, the output current goes back to the initial state of
100% nominal average output current. Since ZLED7x30 needs to count the time for more than 2 seconds after the
switch is off during a normal switch, one capacitor (C1) equal to or greater than 220μF is required to keep the chip
working in low quiescent current mode during this part of the off-time.
2.4
ZLED7x30 Protection Features
Thermal Shut-down Protection
2.4.1
The ZLED7x30 automatically protects itself from damage due to over-temperature conditions. If the ZLED7x30’s
temperature exceeds the thermal shutdown threshold (TSD = 150°C, typical), the ZLED7x30 will shutdown. To avoid
erratic ZLED7x30 operation, a 20K hysteresis (TSD-HYS) is applied that prevents it from returning to operation until its
temperature falls below the hysteresis threshold (TSD - TSD-HYS). Also refer to section 3.2 for additional thermal
considerations.
2.4.2
LED Open-Load Protection
As a step-down converter, the ZLED7x30 has inherent open-load circuit protection. Since the L1 inductor is
connected in series with the LED string, the current flow is interrupted if the load is open and the LX output of the
ZLED7x30 will not be damaged. This provides an advantage over other products such as boost converters, for which
the internal switch can be damaged by back EMF forcing the drain above its breakdown voltage.
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x30 Datasheet
3
Application Circuit Design
3.1
Applications
The ZLED7x30 is designed for applications requiring features such as high-speed switching, variable brightness
control, operation with voltages up to 40V, high efficiency, or protection from over-temperature, or open LED circuit
conditions.
Typical applications include MR16/MR11 LED spot lights, LED street lights, parabolic aluminized reflector (PAR) LED
lights, and other general purpose industrial and consumer LED applications.
Figure 3.1 shows the minimum configuration for switch dimming applications. Figure 3.2 demonstrates the basic
application circuit with the additional capacitors C1 and C3 for enhanced performance. For dimensioning of the
current sense resistor, see section 2. An example of operation with a halogen lamp electronic transformer is shown in
Figure 3.3.
Figure 3.1
ZLED7x30 Application Circuit for Switch Dimming
Switch
Rs
D1
Vs = 8.5 to 40 VDC
(C3)
LED
String
Vin
I SENSE
L1
33 to 220 µH
ZLED7X30
C1
≥220µF
C2
0.1µF
LX
DIM1
DIM2
GND/Floating
GND/Floating
GND
Figure 3.2
Basic ZLED7x30 Application Circuit with Output Current Determined only by Rs
Rs
Vs = 8.5 to 40 VDC
D1
(C3)
LED
String
Vin
I SENSE
L1
33 to 220 µH
ZLED7X30
(C1)
C2
0.1µF
LX
DIM1
DIM2
GND
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ZLED7x30 Datasheet
Figure 3.3
ZLED7x30 Application Circuit using a Halogen Electronic Transformer to Operate with AC Line Supply
Rs
D1
D1
D2
Switch
(C3)
LED
String
Vin
I SENSE
Halogen
Electronic
L1
110/220 VAC
33 to 220 µH
ZLED7X30
Transformer
C1
≥220µF
C2
0.1µF
LX
DIM1
DIM2
GND/Floating
GND/Floating
GND
D3
D4
3.2
Thermal Considerations for Application Design
3.2.1
Temperature Effects of Load, Layout, and Component Selection
Do not exceed the package power dissipation limits by driving high load currents or by operating the chip at high
ambient temperatures. Power dissipation also increases if the efficiency of the circuit is low as could result from
selecting the wrong coil or from excessive parasitic output capacitance on the switch output. See the layout
guidelines in section 3.4.
3.2.2
Temperature Effects of Low Supply Voltage VIN
Until the supply input voltage on the VIN pin has risen above the internally-set startup threshold, the ZLED7x30’s
internal regulator disables the drive to the internal power MOSFET output switch. Above this threshold, the MOSFET
on-resistance is low enough for the chip to start to operate; however, if the supply voltage remains below the
specified minimum (8.5V), the duty cycle of the output switch will be high and the ZLED7x30 power dissipation will be
at a maximum. Avoid operating the ZLED7x30 under such conditions to reduce the risk of damage due to exceeding
the maximum die temperature. When driving multiple LEDs, their combined forward voltage drop is typically high
enough to prevent the chip from switching when VIN is below 8.5V, so there is less risk of thermal damage.
3.3
External Component Selection
Note: Also see section 3.4 for layout guidelines for the following external components.
3.3.1 Sense Resistor Rs
Table 3.1 gives values for Rs under normal operating conditions in the typical application shown in Figure 3.1. These
values assume that no dimming condition is valid. Under the conditions given the table, in order to maintain the switch
current below the maximum value specified in section 1, 0.082Ω is the minimum value for Rs for the ZLED7030, 0.1Ω
for the ZLED7330, 0.13Ω for the ZLED7530 and 0.27Ω for the ZLED7730.
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To ensure stable output current, use a 1% accuracy resistor with adequate power tolerance and a good temperature
characteristic for Rs.
Table 3.1
Recommended Values for Sense Resistor Rs
Nominal Average Output Current (mA)
Value for RS (Ω)
1200 (maximum for ZLED7030)
1000 (maximum for ZLED7330)
750 (maximum for ZLED7530)
667
0.082
0.1
0.13
0.15
0.27
0.3
350 (maximum for ZLED7730)
333
3.3.2
Inductor L1
The recommended range for the L1 inductor is 33μH to 220μH. Select the inductor value for L1 as needed to ensure
that switch on/off times are optimized across the load current and supply voltage ranges. If the application requires a
high supply voltage and low output current, inductance values at the high end of this range are recommended to
minimize errors due to switching delays, which can reduce efficiency and increase ripple on the output. Also see
section 3.4 for layout considerations for L1. Equations (3) and (4) can be used to calculate tON and tOFF
.
On Time for LX Switch (tONmin>200ns):
L * ∆I
tON
=
(3)
(4)
VIN −VLED − IAVG * (RS + rL + RLX )
Off Time for LX Switch (tOFFmin>200ns):
L * ∆I
tOFF
=
VLED + VD + IAVG * (RS + rL )
Where:
Symbol
Description
L
L1 coil inductance in H
ΔI
L1 coil peak-peak ripple current in A (internally set to 0.3 ∗ IAVG
Supply voltage in V
)
VIN
VLED
IAVG
Rs
rL
Total forward voltage in V for LED string
Nominal average LED current in A
External current sense resistor in Ω
L1 coil resistance in Ω
RLX
VD
LX switch resistance in Ω
D1 diode forward voltage at the required load current in V
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The inductance value has an equivalent effect on tON and tOFF and therefore affects the switching frequency. For the
same reason, the inductance has no influence on the duty cycle, for which the relationship of the summed LED
forward voltages n * VF to the input voltage VIN is a reasonable approximation. Because the input voltage is a factor in
the ON time, variations in the input voltage affect the switching frequency and duty cycle.
To achieve optimum performance, duty cycles close to 0.5 at the nominal average supply voltage are preferable for
improving the temperature stability of the output current.
Equations (5), (6), (7), and (8) provide an example of calculating tON, tOFF, operating frequency fLX, and duty cycle DLX
when using a 220μH inductor for L1 and VIN=12V, Rs = 0.30Ω, rL=0.26Ω, VLED=3.4V, IAVG =333mA, VD=0.36V, and
RLX=0.27Ω.
Example:
220µH ∗ 0.3 ∗ 0.333A
tON
=
= 2.64µs
(5)
(6)
(7)
(8)
12V − 3.4V − 0.333A ∗
(
0.3Ω + 0.26Ω + 0.27Ω
)
220µH ∗ 0.3∗ 0.333A
tOFF
=
= 5.56µs
3.4V + 0.36V + 0.333A∗
(
0.30Ω + 0.26Ω
)
1
1
fLX
=
=
= 121.8kHz
TON + TOFF 2.64µs + 5.56µs
VLED
VIN
TON
3.4V
2.64µs
DLX
=
=
≈
=
≈ 0.3
12V TON + TOFF 2.64µs + 5.56µs
For the L1 inductor, use a coil with a continuous current rating higher than the required mean output current and a
saturation current that exceeds the peak output current by 30% to 50% for robustness against transient conditions;
e.g., during start-up.
3.3.3
Bypass Capacitor C1
The bypass capacitor C1 has two functions: maintaining operating voltage and bypassing the current ripple of the
switching converter. In general, low ESR capacitors must be used.
If the circuit is supplied by rectified line voltage, C1 must provide enough charge to maintain the ZLED7x30’s
minimum operating voltage as well as the forward voltage of the LED string to keep the application working even if
the rectified supply voltage periodically drops below these values. A rough estimate for the minimum capacity needed
can be calculated with equation (9).
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IAVG *tD
∆VMAX
IF ∗ DLX
∆VMAX ∗ fLX
C1MIN
=
=
(9)
Where:
Symbol
Description
IAVG
Average nominal LED string current assuming that the contribution of the IC supply current is
negligible.
tD
ΔVMAX
Discharge time at given AC frequency. Will be a maximum of 10ms (½ period duration) at 50Hz.
Peak rectified supply voltage minus LED string forward voltage or minimum ZLED7x30 supply
voltage, whichever is greater.
Example: For an application with 3 LEDs with 3.2V forward voltage each driven at 0.33A and supplied with rectified
24VAC, a minimum bypass capacitor C1 of 220μF or 330μF might be adequate. Compared to the calculation, a
safety margin of about 50% must be added to consider temperature effects and aging.
0.33A*10ms
(10)
C1MIN
=
= 135µF
24V * 2 − 3* 3.2V
A second function of C1 is to bypass the current ripple of the switching converter and thus prevent it from disturbing a
stable IC supply or backlash on the power supply circuit. For this reason even in DC-supplied applications, the use of
an adequate C1 might be useful. The defining parameters are now as shown in equation (11):
IAVG *tON
C1MIN
=
(11)
Vripple
Where:
Symbol
Description
IAVG
tON
Average nominal LED string current.
ON time of the internal MOSFET output switch.
Note: tON must be longer than tONmin=200ns.
Vripple
Permissible voltage ripple on the supply voltage.
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Example: For an application of 3 LEDs driven at 0.33A and supplied with 24VDC, a maximum ripple of 10% is
allowed. The ZLED7x30 is operated at 150kHz with a duty cycle of 0.4 leading to an ON time of 2.67μs. As calculated
in equation 12, a capacitor C1 of 470nF may be adequate, again including a safety margin of about 50%.
0.33A* 2.67µs
C1MIN
=
= 367nF
(12)
24V *0.1
To achieve maximum stability over temperature and voltage, an X7R, X5R, or better dielectric is recommended while
Y5V must be avoided.
3.3.4
De-bouncing Capacitor C2
External capacitor C2 minimizes ground bounce during switching of the internal MOSFET output switch. Ground
bounce is typically caused by parasitic inductance and resistance due to the distance between the grounds for the
power supply and the ZLED7x30 GND pin. Use a 0.1μF, X7R ceramic capacitor to ground for C2.
3.3.5
Capacitor C3 for Reducing Output Ripple
If required, the C3 can be used to reduce peak-to-peak ripple current in the LED string. Low ESR capacitors should
be used because the efficiency of C3 largely depends on its ESR and the dynamic resistance of the LEDs. For an
increased number of LEDs, using the same capacitor will be more effective. Lower ripple can be achieved with higher
capacitor values, but this will increase start-up delay by reducing the slope of the LED voltage as well as cause
increased current during converter start-up. The capacitor will not affect operating frequency or efficiency. For a
simulation or bench optimization, C3 values of a few μF are an applicable starting point for the given configuration.
Ripple current reduction is approximately proportional to the value of C3.
3.3.6
Diode D1
The flyback diode D1 must have a continuous current rating greater than the maximum output load current and a
peak current rating higher than the peak L1 coil current. Important: Use a low-capacitance, fast Schottky diode that
has low reverse leakage at the maximum operating temperature and maximum operating voltage for the application
to avoid excess power dissipation and optimize performance and efficiency. For silicon diodes, there is a concern that
the higher forward voltage and increased overshoot from reverse recovery time could increase the peak LX pin
voltage (VLX). The total voltage VLX (including ripple voltage) must not be >50V.
3.4
Application Circuit Layout Requirements
The following guidelines are strongly recommended when laying out application circuits:
• Important: Locate the L1 inductor and the C1 input decoupling capacitor as close as possible to the ZLED7x30
to minimize parasitic inductance and resistance, which can compromise efficiency. Use low resistance
connections from L1 to the LX and VIN pins.
• All circuit board traces to the LX pin must be as short as possible because it is a high-speed switching node.
• To minimize ground bounce, locate the 0.1μF external capacitor C2 as close as possible to the VIN pin and
solder the ZLED7x30’s GND pin directly to the ground plane. (Also, see section 3.3.4 regarding ground
bounce.)
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ZLED7x30 Datasheet
• Because Rs is typically a low value resistor, it is important to consider the resistance of the traces in series with
RS as part of the total current sense resistance. Use traces that are as short and wide as possible to minimize
this effect.
• The ZLED7x30’s DIM pins are high impedance inputs. When left floating, these pins are pulled up to 3.3V by
internal circuitry. Avoid running high voltage traces close to the DIM pins.
4
ESD Protection
All pins have an ESD protection of ≥ ±3000V according to the Human Body Model (HBM). The ESD test follows the
Human Body Model with 1.5 kΩ/100 pF based on MIL 883-H, Method 3015.8.
5
Pin Configuration and Package
Figure 5.1
ZLED7x30 Pin Configuration
VIN
LX
ISENSE
GND
DIM1
DIM2
NC
NC
Table 5.1
ZLED7x30 Pin Descriptions—SOP-8 Package
Pin
No.
Description (Also see section 3.3 for layout guidelines)
VIN
1
2
Input voltage (8.5V to 40V).
ISENSE
Current adjustment input. Resistor RS from ISENSE to VIN determines the nominal average output
current. IOUTnom =0.1V/RS
NC
NC
3
4
Not connected; keep floating.
Not connected; keep floating.
Set the number of current levels and current ratio of each level of switch dimming function as follows:
DIM2
DIM1
5
6
DIM1 Pin
Floating
Floating
GND
DIM2 Pin
Floating
GND
Dimming Mode
No dimming
Three levels: 100%, 50%, 20%
Three levels: 100%, 60%, 30%
Two levels: 100%, 30%
Floating
GND
GND
GND
LX
7
8
Connect to GND.
Drain of internal power switch
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ZLED7x30 Datasheet
SOP8 Package Dimensions
Table 5.2
Package Dimensions SOP-8
Dimension (mm)
Dimension (mm, except θ)
Symbol
Symbol
Min
Max
1.750
0.250
Min
Max
4.000
6.240
A
A1
A2
b
1.350
0.100
E
E1
e
3.800
5.800
1.450 Typical
1.270 Typical
0.350
0.178
4.800
0.490
0.250
5.000
L
0.400
0°
1.270
8°
c
θ
D
The SOP-8 package has a thermal resistance (junction to ambient) of RθJA = 128 K/W.
6
Ordering Information
Ordering Information
Product Sales Code Description
Package
ZLED7030ZI1R
ZLED7330ZI1R
ZLED7530ZI1R
ZLED7730ZI1R
ZLED7030KIT-D1
ZLED-PCB8
ZLED7030 – High Current (1200mA) 40V LED Driver with Switch Dimming
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
SOP-8 (Tape & Reel)
Kit
ZLED7330 – High Current (1000mA) 40V LED Driver with Switch Dimming
ZLED7330 – High Current (750mA) 40V LED Driver with Switch Dimming
ZLED7330 – High Current (350mA) 40V LED Driver with Switch Dimming
ZLED7030 Demo Kit 12VAC/VDC, including 1 ZLED-PCB8
Test PCB with one 5W white High Brightness (HB) LED, cascadable to one
multiple LED string
Printed Circuit Board (PCB)
ZLED-PCB2
10 unpopulated test PCBs for modular LED string with footprints of 9 common Printed Circuit Board (PCB)
HB LED types
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ZLED7x30 Datasheet
7
Document Revision History
Revision
1.0
Date
Description
14th June, 2011
9th August, 2011
First issue.
1.1
Second issue. Updated Demo Kit description. Updated Typical Application Circuit,
Figures 3.1, 3.2 and 3.3.
1.2
16th August, 2011
April 20, 2016
Third issue. Updated to include ZLED7530 & ZLED7730.
Updated Demo Kit description
Changed to IDT branding.
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www.IDT.com/go/support
1-800-345-7015 or 408-284-8200
Fax: 408-284-2775
www.IDT.com/go/sales
www.IDT.com
DISCLAIMER Integrated Device Technology, Inc. (IDT) reserves the right to modify the products and/or specifications described herein at any time, without notice, at IDT's sole discretion. Performance
specifications and operating parameters of the described products are determined in an independent state and are not guaranteed to perform the same way when installed in customer products. The
information contained herein is provided without representation or warranty of any kind, whether express or implied, including, but not limited to, the suitability of IDT's products for any particular purpose, an
implied warranty of merchantability, or non-infringement of the intellectual property rights of others. This document is presented only as a guide and does not convey any license under intellectual property
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Integrated Device Technology, IDT and the IDT logo are trademarks or registered trademarks of IDT and its subsidiaries in the United States and other countries. Other trademarks used herein are the
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