ZLED7320 [IDT]
High Current 40V LED Driver with Internal Switch;
| 型号： | ZLED7320 |
| 厂家： | 
INTEGRATED DEVICE TECHNOLOGY |
| 描述： | High Current 40V LED Driver with Internal Switch |
| 文件： | 总27页 (文件大小：556K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ZLED7x20
High Current 40V LED
Datasheet
Driver with Internal Switch
Brief Description
Benefits
The ZLED7x20 continuous-mode inductive step-
down converter family is part of our line of LED-
control ICs. It is designed for applications requiring
high brightness and high current. It can efficiently
drive a single LED or multiple series-connected
LEDs from a voltage input higher than the LED for-
ward voltage: Vin = 6 to 40 VDC. It provides an
adjustable output current ≤1.2A, which is set via an
external resistor and controlled by the ZLED7x20’s
integrated high-side output current-sensing circuit
and high speed internal 40V power switch. An
external control signal, which can be a DC voltage,
PWM, or microcontroller-generated waveform, on
the ADJ pin can also be used to linearly adjust a
continuous output current or to control a gated out-
put current.
• High efficiency: up to 98%
• Single pin on/off and brightness control using
DC voltage or PWM
• Very few external components needed for
operation
• Footprint compatible with our ZLED7000
depending on the application.
Available Support
• Evaluation Kit
Physical Characteristics
• Operating junction temperature: -40°C to 125°C
• Switching frequency: up to 1MHz
The output can be turned off by applying a voltage
lower than 0.2V to the ADJ pin, which puts the
ZLED7x20 in a low-current standby state.
ZLED7x20 Family Selection Matrix
Product
ZLED7020
ZLED7320
ZLED7520
ZLED7720
Max. Current Output
Package
SOT89-5
DFN-5
The ZLED7x20 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 pro-
tection. The ZLED7x20 can also minimize bill-of-
material costs because very few external com-
ponents are required for most applications. Only a
resistor, a diode, an inductor, and three capacitors
are needed for a typical basic application.
1.2A
1.0A
0.75A
0.35A
DFN-5
DFN-5
ZLED7x20 Typical Application Circuit
Features
Rs
Vs = 6 to 40 VDC
• Up to 1.2A output current
• Internal 40V power switch
D1
• Wide DC input voltage range 6 to 40 VDC
• Output current accuracy: 3% (typical)
• Dimming ratio: 1200:1
(C3)
LED
String
Vin
I SENSE
• LED open-circuit protection
• Thermal shutdown protection
L1
(C1)
C2
0.1µF
ZLED7x20
LX
33µH to
220µH
ADJ
GND
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20
High Current 40V LED
Datasheet
Driver with Internal Switch
ZLED7x20 Block Diagram
6 to 40 VDC
VS
Rs
D1
4 ISENSE
(C1)
C2
0.1µF
VCC
(C3)
n LED
VDDA
VDDD
5
Power
Supply,
Oscillator,
VIN
L1
1
ISENSE
and Under-
VIN
33µH to
220µH
LX
Voltage
Power
MOS
UV
Detection
ISENSE
And
(UV)
DR
POR
VREF
Driver
SD
SD
500kΩ
3
Shutdown
ADJ
ISENSE
POR
LX
Trim
ZLED7X20
2
GND
Typical Applications
Illuminated LED signs and other displays
Interior/exterior LED lighting
MR16 LED spot lights
LED street and traffic lighting (low voltage)
Architecture/building LED lighting
LED backlighting
Retrofit LED lighting fixtures
General purpose industrial and consumer LED applications
Ordering Information
Product Code Description
Package
ZLED7020ZI1R
ZLED7320ZI1R
ZLED7520ZI1R
ZLED7720ZI1R
ZLED7020 – High Current (1200mA) 40V LED Driver with Internal Switch
ZLED7320 – High Current (1000mA) 40V LED Driver with Internal Switch
ZLED7520 – High Current (750mA) 40V LED Driver with Internal Switch
ZLED7720 – High Current (350mA) 40V LED Driver with Internal Switch
SOT89-5 (Tape & Reel)
DFN-5 (Tape & Reel)
DFN-5 (Tape & Reel)
DFN-5 (Tape & Reel)
Kit
ZLED7020KIT-D1 ZLED7020-D1 Demo Board, 1 ZLED-PCB8 and 5 ZLED7020 ICs
ZLED-PCB8
Test PCB with a 5W white high brightness (HB) LED, cascadable to a multiple LED string Printed Circuit Board (PCB)
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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
ZLED7x20 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
ZLED7x20 Overview............................................................................................................................................ 12
Control of Output Current via External Sense Resistor Rs .................................................................................. 12
Control of Output Current via an External DC Control Voltage on the ADJ Pin ................................................... 12
Additional Requirements if the VIN Input Voltage has a High Slew Rate.............................................................. 13
Control of Output Current via a PWM Signal on the ADJ Pin............................................................................... 13
Control of Output Current via a Microcontroller Signal on the ADJ Pin................................................................ 13
Shutdown Mode................................................................................................................................................... 13
ZLED7x20 Protection Features............................................................................................................................ 14
Thermal Shut-down Protection ..................................................................................................................... 14
LED Open Load Protection........................................................................................................................... 14
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.8.1
2.8.2
3
Application Circuit Design ........................................................................................................................................... 15
3.1
3.2
3.2.1
3.2.2
3.3
Applications ......................................................................................................................................................... 15
Thermal Considerations for Application Design................................................................................................... 17
Temperature Effects of Load, Layout, and Component Selection ................................................................ 17
Temperature Effects of Low Supply Voltage VIN........................................................................................... 17
External Component Selection ............................................................................................................................ 17
Sense Resistor Rs........................................................................................................................................ 17
Inductor L1.................................................................................................................................................... 18
Bypass Capacitor C1.................................................................................................................................... 19
De-bouncing Capacitor C2 ........................................................................................................................... 20
Capacitor C3 for Reducing Output Ripple..................................................................................................... 21
Diode D1....................................................................................................................................................... 21
Application Circuit Layout Requirements............................................................................................................. 21
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.4
4
5
ESD Protection............................................................................................................................................................ 22
Pin Configuration and Package................................................................................................................................... 22
5.1
5.2
SOT89-5 Package Pin-out and Dimensions for the ZLED7020 ........................................................................... 22
DFN-5 Package Pin-out and Dimensions for the ZLED7320, ZLED7520 and ZLED7720................................... 24
6
7
8
9
Ordering Information ................................................................................................................................................... 26
Related Documents..................................................................................................................................................... 26
Glossary...................................................................................................................................................................... 26
Document Revision History......................................................................................................................................... 27
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
List of Figures
Figure 1.1 ZLED7x20 Supply Operating Current vs. Input Supply Voltage (VIN = 6 to 40 V)................................................... 7
Figure 1.2 ZLED7x20 Supply Quiescent Shutdown Current vs. Input Supply Voltage (VIN = 6 to 40 V).................................. 7
Figure 1.3 Efficiency (%) vs. Input Supply Voltage (VIN = 6 to 40 V) Per Number of LEDs (Rs=0.10Ω, L1=47μH).................. 8
Figure 1.4 Efficiency vs. Input Supply Voltage (VIN = 6 to 40 V) Per Number of LEDs (Rs=0.15Ω, L1=47μH)........................ 8
Figure 1.5 Efficiency vs. Input Supply Voltage (VIN = 6 to 40 V)‡ Per Number of LEDs (Rs=0.30Ω, L1=47μH)....................... 9
Figure 1.6 Output Current Variation vs. Input Supply Voltage (VIN = 6 to 40 V) Per Number of LEDs (Rs = 0.15Ω, L1 = 47μH)
............................................................................................................................................................................... 9
Figure 1.7 Sense Voltage vs. Operating Temperature (Rs=0.10Ω, L1=47μH, VIN = 40 V) .................................................... 10
Figure 1.8 Dimming Rate with 100Hz Square Wave Control Signal (PWM) at ADJ Pin (current rise time=7.85μs) ............. 10
Figure 1.9 LED Open-Circuit Protection (Rs=0.30Ω, L1=47μH, VIN = 24 V).......................................................................... 11
Figure 3.1 Basic ZLED7x20 Application Circuit with Output Current Determined only by Rs ................................................ 15
Figure 3.2 Basic ZLED7x20 Application Circuit with Output Current Controlled by External DC Voltage.............................. 15
Figure 3.3 Basic ZLED7x20 Application Circuit with Output Current Set by External Square Wave Voltage (PWM) ............ 16
Figure 3.4 Basic ZLED7x20 Application Circuit with Output Current Controlled by External Microcontroller Signal.............. 16
Figure 5.1 ZLED7020 Pin Configuration – SOT89-5 Package............................................................................................... 22
Figure 5.2 SOT89-5 Package Dimensions for the ZLED7020 ............................................................................................... 23
Figure 5.3 ZLED7320, ZLED7520 & ZLED7720 Pin Configuration — DFN-5 Package......................................................... 24
Figure 5.4 DFN-5 (DFN4*4-05L) Package Dimensions for the ZLED7320, ZLED7520 & ZLED7720 ................................... 25
List of Tables
Table 3.1 Recommended Values for Sense Resistor Rs (ADJ pin floating at nominal voltage VREF=1.2V).......................... 17
Table 5.1 ZLED7020 Pin Descriptions—SOT89-5 Package................................................................................................. 22
Table 5.2 ZLED7320, ZLED7520 & ZLED7720 Pin Descriptions — DFN-5 Package.......................................................... 24
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
1
IC Characteristics
Note: Exceeding the maximum ratings given in this section could cause operation failure and/or cause permanent
damage to the ZLED7x20. 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
VIN<5V
VIN+0.3V
1.1.3
1.1.4
1.1.5
1.1.6
1.1.7
1.1.8
1.1.9
LX pin output voltage
ADJ pin input voltage
LX pin switch output current
Power dissipation
VLX
VADJ
ILX
50
6
V
-0.3
V
1.5
0.5
A
PTOT
W
ESD performance
Human Body Model
±3.5
-55
kV
°C
K/W
K/W
°C
Junction temperature
TJ
150
100
130
150
Junction to ambient thermal
resistance
SOT89-5 package
DFN5 package
RθJA
1.1.10 Storage temperature
TS
1.2
Operating Conditions
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
1.2.1
Operating junction
temperature
TJ
-40
125
°C
1.2.2
Input voltage (also see
specification 1.1.1)
VIN
6
40
V
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
1.3
Electrical Parameters
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
CONDITIONS
MIN
TYP
MAX
UNIT
1.3.1
Quiescent supply current
IINQoff
Output off—ADJ pin
grounded
90
120
160
μA
IINQon
Output switching—ADJ pin
floating
450
100
600
103
μA
1.3.2
Mean current sense
threshold voltage
VSENSE
97
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
ADJ pin floating
Internal reference voltage
measured at ADJ pin
VREF
1.2
1.3.6
1.3.7
1.3.8
Resistance between VREF
and ADJ pin
RADJ
VADJ
500
KΩ
External DC brightness
control voltage on ADJ pin
0.3
1.2
V
DC on-off control voltage on
ADJ pin for switching
ZLED7x20 from active state
to quiescent state
VADJoff
VADJ falling
VADJ rising
0.15
0.2
0.25
V
V
1.3.9
DC off-on control voltage on
ADJ pin for switching
ZLED7x20 from quiescent
state to active state
VADJon
0.2
0.25
0.3
1.3.10
LX switch continuous
current
ILXmean_0
ILXmean_3
ILXmean_5
ILXmean_7
ILX(leak)
RLX
ZLED7020
ZLED7320
ZLED7520
ZLED7720
1.2
1.0
0.75
0.35
1
A
A
A
A
1.3.11
1.3.12
1.3.13
1.3.14
1.3.15
LX switch leakage current
LX switch on resistance
Minimum switch on time
Minimum switch off time
Dimming rate
μA
Ω
0.27
200
200
0.4
tONmin
LX switch on
LX switch off
ns
ns
tOFFmin
DDIM
1 LED, f =100Hz, Vin=15V,
L1 = 27μH
1200:1
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
1.3.16
Recommended operating
frequency maximum
fLXmax
1
MHz
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
50
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
ZLED7x20 Supply Operating Current vs. Input Supply Voltage (VIN = 6 to 40 V)
600
500
400
300
200
100
0
5
10
15
20
25
30
35
40
Vin(V)
Figure 1.2
ZLED7x20 Supply Quiescent Shutdown Current vs. Input Supply Voltage (VIN = 6 to 40 V)
250
200
150
100
50
0
5
10
15
20
25
30
35
40
Vin(V)
© 2016 Integrated Device Technology, Inc.
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ZLED7x20 Datasheet
Figure 1.3
Efficiency (%) vs. Input Supply Voltage (VIN = 6 to 40 V)† 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)
Figure 1.4
Efficiency vs. Input Supply Voltage (VIN = 6 to 40 V)‡ Per Number of LEDs (Rs=0.15Ω, L1=47μH)
1
Rs=0.15Ω
0.95
1LED
0.9
3LED
0.85
7LED
0.8
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
‡ Minimum V depends on number of LEDs.
in
© 2016 Integrated Device Technology, Inc.
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ZLED7x20 Datasheet
Figure 1.5
Efficiency vs. Input Supply Voltage (VIN = 6 to 40 V)‡ Per Number of LEDs (Rs=0.30Ω, L1=47μH)
1
0.95
0.9
Rs=0.30Ω
1LED
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)
Figure 1.6
Output Current Variation vs. Input Supply Voltage (VIN = 6 to 40 V)§ 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)
§ Minimum V depends on number of LEDs.
in
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
Figure 1.7
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)
Figure 1.8
Dimming Rate with 100Hz Square Wave Control Signal (PWM) at ADJ Pin (current rise time=7.85μs)
Timebase -3.00 ms Trigger C1 HFR
1.00ms/div Stop
50 MS/s Edge
-50mV
Positive
500kS
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7x20 Datasheet
Figure 1.9
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
ZLED7x20 Datasheet
2
Circuit Description
2.1
ZLED7x20 Overview
The ZLED7x20 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 = 6 to 40 VDC; see section 3.2.2 for
important details). The ZLED7x20 provides an adjustable output current (1.2A maximum for ZLED7020; 1.0A
maximum for ZLED7320; 0.75A maximum for ZLED7520; 0.35A maximum for ZLED7720), which is nominally set
via an external sense resistor Rs and controlled by the ZLED7x20’s integrated high-side output current-sensing
circuit and output switch. An external control signal (e.g., DC voltage, PWM waveform, or microprocessor signal)
on the ADJ pin can be used to linearly adjust the output for continuous, variable, or gated-output current. See
page 2 for a block diagram of the ZLED7x20.
The output can be turned off by applying a voltage ≤0.2V (typical) to the ADJ pin, which puts the ZLED7x20 in a
low-current standby state. See section 2.7 for a description of this shutdown mode.
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 referenced 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
OUTnom, the nominal average output current. Equation (1) can be used to calculate the nominal output current,
I
which is the LX switch output current ILX if the ADJ pin is floating (VADJ = VREF =1.2V). See section 3.3.1 for
recommended values for Rs in a typical basic application and section 3.4 for layout guidelines for Rs. Note that
the peak IOUTnom including ripple (see section 3.3.5) must not exceed the maximum current specifications (1.3.10).
0.1V
IOUTnom
=
(1)
Rs
2.3
Control of Output Current via an External DC Control Voltage on the ADJ Pin
An external DC voltage (VADJ) input on the ADJ pin can control brightness by setting the output current to a value
below the nominal average current IOUTnom determined by RS. With this method, the output current can be adjusted
from 25% to 100% of IOUTnom. The DC voltage source must be capable of driving the ADJ pin’s input impedance
RADJ (500kΩ ± approximately 25%; internal pull-up resistor to VREF). See Figure 3.2 for a typical application circuit.
The nominal average output current IOUTdc resulting from an external DC control voltage VADJ can be calculated via
equation (2) where 0.3V≤ VADJ ≤1.2V:
0.083∗ VADJ
IOUTdc
=
(2)
RS
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ZLED7x20 Datasheet
Brightness is 100% if VADJ = VREF, the internal reference voltage, which can be measured on the ADJ pin when it is
floating (1.2V, typical). If VADJ ≥ 1.2V, the current is automatically clamped at 100% brightness.
Note: Absolute maximum VADJ= 6V.
2.4
Additional Requirements if the VIN Input Voltage has a High Slew Rate
The analog dimming input ADJ can be used for implementing a soft-start function of the LEDs by connecting a
capacitor to ground. The soft-start time constant is determined by the product of the internal pull-up resistor
(500kΩ typical) and the external capacitor.
Important: If the supply voltage VIN might have a high slew rate (> 1V/µs) when powered on, a resistor that is
≥ 1kΩ must be placed in series with the capacitor to guarantee correct power-on timing for the ZLED7x20 and
proper loading of the current sense trimming data into the appropriate register. This resistor is not necessary if the
capacitor is ≤ 470pF.
If the ADJ pin is controlled from an external voltage source or PWM signal, a series resistor is strongly
recommended for noise immunity reasons and to avoid bulk current injection.
2.5
Control of Output Current via a PWM Signal on the ADJ Pin
An external pulse width modulation (PWM) control signal input on the ADJ pin can be used for brightness or gated
on/off control of the output current by driving the output current to a value below the nominal average current
determined by RS. See Figure 3.3 for a typical application circuit. The PWM or gated on/off control signal can be
within the range of 0 to 5 V. The logic high level must be higher than 1.2V and the logic low level must be below
0.2V. It must be capable of driving the ADJ pin’s input impedance RADJ (approximately 500kΩ; internal pull-up
resistor to VREF).
2.6
Control of Output Current via a Microcontroller Signal on the ADJ Pin
An external control signal from the open drain output of a microcontroller can provide on/off or PWM brightness
control by driving the ADJ pin. See Figure 3.4 for a typical application circuit. Diode D2 and resistor R1 shown in
Figure 3.4 suppress any negative high-amplitude spikes on the ADJ input due to the drain-source capacitance of
the FET in the microcontroller’s output. Negative spikes on the ADJ input could cause output current errors or
unintended ZLED7x20 operation. The signal input to the ADJ pin must be capable of driving the ADJ pin’s input
impedance RADJ (approximately 500kΩ; internal pull-up resistor to VREF).
2.7
Shutdown Mode
If the ADJ pin voltage VADJ is ≤ VADJoff (0.2V ± 0.05V), the supply current and output on the LX pin are quiescent at
a low standby level (IINQoff = 120μA nominal). Raising the ADJ pin voltage so that VADJ ≥ VADJion (0.25V ± 0.05V)
will switch the output back to full operational mode.
© 2016 Integrated Device Technology, Inc.
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ZLED7x20 Datasheet
2.8
ZLED7x20 Protection Features
Thermal Shut-down Protection
2.8.1
The ZLED7x20 automatically protects itself from damage due to over-temperature conditions. If the ZLED7x20’s
temperature exceeds the thermal shutdown threshold (TSD = 150°C, typical), the ZLED7x20 will shut down. To
avoid erratic ZLED7x20 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.
2.8.2
LED Open Load Protection
As a step-down converter, the ZLED7x20 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
ZLED7x20 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.
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ZLED7x20 Datasheet
3
Application Circuit Design
3.1
Applications
The ZLED7x20 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 spotlights, LED street lights, parabolic aluminized reflector (PAR)
LED lights, and other general purpose industrial and consumer LED applications.
Figure 3.1, Figure 3.2, Figure 3.3, and Figure 3.4 demonstrate basic application circuits for the four options for
controlling output current described in section 2.
Figure 3.1
Basic ZLED7x20 Application Circuit with Output Current Determined only by Rs
Rs
Vs = 6 to 40 VDC
D1
C3
LED
String
Vin
I SENSE
L1
C1
C2
0.1µF
ZLED7X20
LX
ADJ
GND
Figure 3.2
Basic ZLED7x20 Application Circuit with Output Current Controlled by External DC Voltage
Rs
Vs = 6 to 40 VDC
C1
D1
C2
0.1µF
C3
Vin
I SENSE
LED
String
L1
ZLED7X20
(0.3V to 1.2V)
ADJ
LX
+
_
DC
GND
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ZLED7x20 Datasheet
Figure 3.3
Basic ZLED7x20 Application Circuit with Output Current Set by External Square Wave Voltage (PWM)
Rs
Vs = 6 to 40 VDC
C1
D1
C2
0.1µF
C3
Vin
I SENSE
LED
String
L1
PWM (0V to ~5V)
ZLED7X20
ADJ
LX
GND
Figure 3.4
Basic ZLED7x20 Application Circuit with Output Current Controlled by External Microcontroller Signal
Rs
Vs = 6 to 40 VDC
C1
D1
C2
0.1µF
C3
Vin
I SENSE
LED
String
R1
10kΩ
L1
ZLED7X20
Micro-
ADJ
LX
processor
GND
D2
GND
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ZLED7x20 Datasheet
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 ZLED7x20’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 (6V), the duty cycle of the output switch will be high and the ZLED7x20 power
dissipation will be at a maximum. Avoid operating the ZLED7x20 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 6V, 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 the ADJ pin is floating and at the nominal voltage of VREF=1.2V.
Note: Under the conditions given in Table 3.1, 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 ZLED7020, 0.1Ω for the ZLED7320, 0.13Ω for
the ZLED7520 and 0.27Ω for the ZLED7720. It is possible to use different values of Rs if the ADJ pin is driven
from an external voltage.
To ensure stable output current, use a 1% accuracy resistor with adequate power tolerance and a good
temperature characteristic for Rs.
Table 3.1
Nominal Average Output Current (mA)
1200 (maximum for ZLED7020)
Recommended Values for Sense Resistor Rs (ADJ pin floating at nominal voltage VREF=1.2V)
Value for RS (Ω)
0.082
0.1
1000 (maximum for ZLED7320)
750 (maximum for ZLED7520)
0.13
0.15
0.27
0.3
667
350 (maximum for ZLED7720)
333
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ZLED7x20 Datasheet
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 recom-
mended 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
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.
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Equations (5), (6), (7), and (8) provide an example of calculating tON, tOFF, operating frequency fLX, and duty cycle
D
LX 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
= 5.56µs
(5)
(6)
(7)
(8)
12V − 3.4V − 0.333A *
0.3Ω + 0.26Ω + 0.27Ω
220µH*0.3*0.333A
tOFF
=
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
12V
2.64µs
DLX
=
=
≈
=
≈ 0.3
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 con-
ditions; 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 ZLED7x20’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).
IAVG * tD
IF *DLX
C1MIN
=
=
(9)
∆VMAX
∆VMAX * fLX
Where:
Symbol
IAVG
Description
Average nominal LED string current assuming that the contribution of the IC supply current is negligible.
Discharge time at given AC frequency. Will be a maximum of 10ms (½ period duration) at 50Hz.
tD
Peak rectified supply voltage minus LED string forward voltage or minimum ZLED7x20 supply voltage, whichever is greater.
ΔVMAX
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ZLED7x20 Datasheet
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.
Example: For an application of 3 LEDs driven at 0.33A and supplied with 24VDC, a maximum ripple of 10% is
allowed. The ZLED7x20 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 ZLED7x20 GND pin. Use a 0.1μF, X7R ceramic capacitor to ground for C2.
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ZLED7x20 Datasheet
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 effici-
ency. 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
ZLED7x20 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.
• If the ADJ pin floats, all circuit board traces to the ADJ pin must be as short as possible to reduce noise
pickup.
• Do not lay out high-voltage traces near the ADJ pin because if the board is contaminated, leakage current
can affect the ADJ pin voltage and cause unintended output current. To further reduce this risk, use a
ground ring around the ADJ pin. (Also see section 2.8 regarding the ZLED7x20’s protection circuitry for
preventing excessive output current.)
• To minimize ground bounce, locate the 0.1μF external capacitor C2 as close as possible to the VIN pin and
solder the ZLED7x20’s GND pin directly to the ground plane. (Also, see section 3.3.4 regarding ground
bounce.)
• 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 ZLED7x20’s thermal pad must be grounded.
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ZLED7x20 Datasheet
4
ESD Protection
All pins have an ESD protection of ≥ ±3500V 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
5.1
SOT89-5 Package Pin-out and Dimensions for the ZLED7020
Figure 5.1
ZLED7020 Pin Configuration – SOT89-5 Package
1
5
LX
VIN
2
GND
Thermal Pad
ISENSE
3
4
ADJ
Table 5.1
ZLED7020 Pin Descriptions—SOT89-5 Package
Pin
No.
Description (Also see section 3.3 for layout guidelines)
Drain of internal power switch
LX
1
2
3
4
GND
ADJ
Ground
On/off and brightness control input
ISENSE
Current adjustment input. Resistor RS from ISENSE to VIN determines the nominal average output
current. IOUTnom =0.1V/RS
Thermal Pad
VIN
Connect to GND.
5
Input voltage (6V to 40V).
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ZLED7x20 Datasheet
Figure 5.2
SOT89-5 Package Dimensions for the ZLED7020
D
A
D1
E1
E
b1
L
e
b
c
e1
Dimension (mm)
Symbol
Min
Max
A
b
1.400
0.320
0.360
0.350
4.400
1.400
2.300
3.940
1.600
0.520
0.560
0.440
4.600
1.800
2.600
4.250
b1
c
D
D1
E
E1
e
1.500 Typical
e1
L
2.900
0.900
3.100
1.100
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ZLED7x20 Datasheet
5.2
DFN-5 Package Pin-out and Dimensions for the ZLED7320, ZLED7520 and ZLED7720
Figure 5.3
ZLED7320, ZLED7520 & ZLED7720 Pin Configuration — DFN-5 Package
1
LX
5
VIN
5
1
2
3
2
3
GND
ADJ
4
4
ISENSE
TOP
BOTTOM
Table 5.2
ZLED7320, ZLED7520 & ZLED7720 Pin Descriptions — DFN-5 Package
Pin
No.
Description (Also see section 3.3 for layout guidelines)
Drain of internal power switch
LX
1
2
3
4
GND
ADJ
Ground
On/off and brightness control input
ISENSE
Current adjustment input. Resistor RS from ISENSE to VIN determines the nominal average output
current. IOUTnom =0.1V/RS
Thermal Pad
VIN
Connect to GND.
5
Input voltage (6V to 40V).
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ZLED7x20 Datasheet
Figure 5.4
DFN-5 (DFN4*4-05L) Package Dimensions for the ZLED7320, ZLED7520 & ZLED7720
B
j
i
k
A
k1
h
g
D
f
e
m
n
C
Dimension (mm)
Symbol
Min
3.95
3.95
0.70
0.37
0.75
2.17
Max
4.05
4.05
0.80
0.47
0.95
2.42
A
B
C
D
e
f
g
h
i
1.50
0.41
0.51
0.55
1.70
1.75
j
k
k1
m
n
1.40
1.55
0.000
0.050
0.200
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ZLED7x20 Datasheet
6
Ordering Information
Ordering Information
Product Sales Code Description
Package
ZLED7020ZI1R
ZLED7320ZI1R
ZLED7520ZI1R
ZLED7720ZI1R
ZLED7020KIT-D1
ZLED-PCB8
ZLED7020 – High Current (1200mA) 40V LED Driver with Internal Switch
SOT89-5 (Tape & Reel)
ZLED7320 – High Current (1000mA) 40V LED Driver with Internal Switch
ZLED7520 – High Current (750mA) 40V LED Driver with Internal Switch
ZLED7720 – High Current (350mA) 40V LED Driver with Internal Switch
ZLED7020-D1 Demo Board, 1 ZLED-PCB8 and 5 ZLED7020 ICs
DFN-5 (Tape & Reel)
DFN-5 (Tape & Reel)
DFN-5 (Tape & Reel)
Kit
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
HB LED types
Printed Circuit Board (PCB)
7
Related Documents
Document
ZLED7x20 Feature Sheet
ZLED7020 Application Note—PCB Layout
Visit the ZLED7x20 product pages at http://www.IDT.com/ or contact your nearest sales office for the latest
version of these documents.
8
Glossary
Term
Description
ESD
EMF
ESR
PWM
Electrostatic Discharge
Electromagnetic Force
Equivalent Series Resistance
Pulse Width Modulation
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ZLED7x20 Datasheet
9
Document Revision History
Revision
1.00
Date
Description
June 27, 2011
August 9, 2011
August 12, 2011
First issue.
1.10
Update to Demo Kit description.
1.20
Update to include ZLED7520 & ZLED7720.
Update for Demo Kit description
1.30
1.40
February 6, 2012
June 11, 2014
Update to include operating junction temperature.
Update to add new section 2.4 regarding requirements if VIN has a high slew rate.
Updates for cover and page header imagery.
Updates for IDT contact information.
Addition of “Related Documents” and “Glossary” sections.
April 20, 2016
Changed to IDT branding.
Corporate Headquarters
Sales
Tech Support
www.IDT.com/go/support
6024 Silver Creek Valley Road
San Jose, CA 95138
www.IDT.com
1-800-345-7015 or 408-284-8200
Fax: 408-284-2775
www.IDT.com/go/sales
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.
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