ZLED-PCB1 [IDT]
40V LED Driver with Temperature Compensation;
| 型号： | ZLED-PCB1 |
| 厂家： | 
INTEGRATED DEVICE TECHNOLOGY |
| 描述： | 40V LED Driver with Temperature Compensation |
| 文件： | 总22页 (文件大小：900K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ZLED7010
40V LED Driver with
Datasheet
Temperature Compensation
Brief Description
Features
• Capable of 95% efficiency*
The ZLED7010, one of our ZLED Family of LED control
ICs, is an inductive step-down converter that is optimal
for driving a single LED or multiple LEDs (connected in
series) from a voltage source greater than the voltage
rating of the LED. The ZLED7010 operates in continu-
ous mode. Capable of operating efficiently with voltage
supplies ranging from 6 VDC to 40 VDC, it is ideal for
low-voltage lighting applications. The ZLED7010 mini-
mizes current consumption by remaining in a low-current
standby mode (output is off) until a voltage of ≥0.3V is
applied to the ADJI pin.
• Operates in continuous mode with a wide input
range from 6 VDC to 40 VDC
• Integrated 40V power switch
• One-pin on/off or brightness control via DC voltage
or PWM control signal
• Switching frequency: ≤ 1MHz
• Dimming rate: 1200:1 (typical)
• Output current accuracy: 5% (typical)
• Built-in temperature compensation and open-circuit
protection for LEDs
In operating mode, the ZLED7010 can source LEDs with
an output current of ≤ 750mA (≤ 30 watts of output
power*) that is externally adjustable. The ZLED7010’s
integrated output switch and high-side current sensing
circuit use an external resistor to adjust the average out-
put current. LED control is achieved via an external con-
trol signal at the ZLED7010’s ADJI pin, implemented as
a pulse-width modulation (PWM) waveform for a gated
output current or a DC voltage for continuous current.
• Thermal shutdown protection for the ZLED7010
• Very few external components needed for operation
• Broad range of applications: outputs up to ≤750mA
• SOP-8 package
The ZLED7010 provides a temperature compen-
sation function for maintaining stable and reliable
LED operation. LED over-temperature conditions
are detected via a negative temperature coefficient
(NTC) thermistor mounted close to the LEDs. If an
over-temperature condition occurs, the NTC value
reaches the value of a threshold resistor and the
IC reduces LED current automatically. After the
circuit recovers to a safe temperature, current
returns to the set value.
Application Examples
• Illuminated LED signs and other displays
• LED traffic and street lighting (low-voltage)
• Architectural LED lighting, including low-voltage
applications for buildings
• Halogen replacement LEDs (low-voltage)
• LED flood-lighting
• LED backlighting
• General purpose exterior and interior LED lighting,
including applications requiring low-voltage
ADJO outputs and ADJI inputs of consecutive ICs
can be interconnected as a driver chain deploying
the temperature compensation information of the
predecessor. This reduces the part count because
only the first stage of the series requires an NTC.
• General purpose low-voltage industrial applications
ZLED7010 Application Circuit
6 to 40 VDC
RS
VS
D1
1
2
n LED
R3
C1
1μF
NTC
VIN
RNTC
ISENSE
4
3
6
L1
ZLED7010
8
5
RTH
ADJI
LX
47μH
C2
100nF
R2
ADJO
GND
7
50k
Ω
* See section 2.3 and 1.4 for details
© 2016 Integrated Device Technology, Inc.
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April 20, 2016
ZLED7010
40V LED Driver with
Datasheet
Temperature Compensation
SOP-8 Package Dimensions and Pin Assignments
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
Ordering Information
Product Sales Code Description
Package
ZLED7010ZI1R
ZLED7010KIT-D1
ZLED-PCB1
ZLED7010 – 40V LED Driver with Temperature Compensation
ZLED7010 Demo Board with LED on Cool Body 12VAC/VDC
Test PCB with one 3W white HB-LED, cascadable to 1 multiple LED string
SOP8 (Tape & Reel)
Kit
Printed Circuit Board
Printed Circuit Board
ZLED-PCB2
10 unpopulated test PCBs for modular LED string with footprints of 9
common HB-LED types
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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ZLED7010 Datasheet
Contents
1
IC Characteristics.......................................................................................................................................................... 5
1.1.
Absolute Maximum Ratings ................................................................................................................................... 5
Operating Conditions............................................................................................................................................. 5
Electrical Parameters............................................................................................................................................. 5
Characteristic Operating Curves............................................................................................................................ 7
1.2.
1.3.
1.4.
2
Circuit Description......................................................................................................................................................... 9
2.1.
Voltage Supply....................................................................................................................................................... 9
ZLED7010 Standby Mode...................................................................................................................................... 9
Output Current Control........................................................................................................................................... 9
2.2.
2.3.
2.3.1.
2.3.2.
Output Current and RS.................................................................................................................................... 9
PWM Control ................................................................................................................................................ 10
External DC Voltage Control of Output Current............................................................................................ 10
Microcontroller LED Control.......................................................................................................................... 11
2.3.3.
2.3.4.
3
4
Application Circuit Design ........................................................................................................................................... 12
3.1.
External Component – Inductor L1 ...................................................................................................................... 12
External Component – Capacitor C1 ................................................................................................................... 13
External Component – Diode D1 ......................................................................................................................... 13
Output Ripple....................................................................................................................................................... 14
3.2.
3.3.
3.4.
Operating Conditions................................................................................................................................................... 15
4.1.
Thermal Conditions.............................................................................................................................................. 15
Thermal Shut-Down Protection............................................................................................................................ 15
Open-Circuit Protection........................................................................................................................................ 15
External Temperature Compensation of Output Current...................................................................................... 15
4.2.
4.3.
4.4.
5
6
7
8
Chaining Multiple ZLED7010 ICs ................................................................................................................................ 18
ESD/Latch-Up-Protection............................................................................................................................................ 19
Pin Configuration and Package................................................................................................................................... 19
Layout Requirements .................................................................................................................................................. 21
8.1.
Layout Considerations for ADJI (Pin 6)................................................................................................................ 21
Layout Considerations for LX (Pin 8)................................................................................................................... 21
Layout Considerations for VIN (Pin 1) and the External Decoupling Capacitor (C1)............................................. 21
Layout Considerations for GND (Pin 7)................................................................................................................ 21
Layout Considerations for ADJO (Pin 5)............................................................................................................... 21
Layout Considerations for RTH and RNTC (Pins 3 and 4)....................................................................................... 21
Layout Considerations for High Voltage Traces................................................................................................... 21
Layout Considerations for the External Coil (L1) ................................................................................................. 21
Layout Considerations for the External Current Sense Resistor (RS) .................................................................. 21
8.2.
8.3.
8.4.
8.5.
8.6.
8.7.
8.8.
8.9.
9
Ordering Information ................................................................................................................................................... 22
10 Document Revision History......................................................................................................................................... 22
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ZLED7010 Datasheet
List of Figures
Figure 1.1
Figure 1.2
Figure 2.1
Figure 2.2
Figure 2.3
Figure 3.1
Figure 4.1
Figure 4.2
Figure 5.1
Figure 5.2
Figure 7.1
Figure 7.2
Characteristic Operating Curves 1 ................................................................................................................. 7
Characteristic Operating Curves 1 ................................................................................................................. 8
Directly Driving ADJI Input with a PWM Control Signal ................................................................................ 10
External DC Control Voltage at ADJI Pin...................................................................................................... 10
Driving ADJI Input from a Microcontroller ..................................................................................................... 11
Output Ripple Reduction .............................................................................................................................. 14
Temperature Compensation......................................................................................................................... 15
Temperature Compensation Graphs............................................................................................................ 17
ZLED7010 Chain Connections..................................................................................................................... 18
ZLED7010 System Application.................................................................................................................... 18
Pin Configuration ZLED7010........................................................................................................................ 19
SOP-8 Package Drawing.............................................................................................................................. 20
List of Tables
Table 4.1
Pin Description SOP-8.................................................................................................................................. 19
Table 7.2
Package Dimensions SOP-8........................................................................................................................ 20
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ZLED7010 Datasheet
1
IC Characteristics
1.1. Absolute Maximum Ratings
No.
PARAMETER
Input voltage
SYMBOL
CONDITIONS
MIN
-0.3
VIN - 5
0
TYP
MAX
50
UNIT
1.1.1
VIN
V
V
V
V
Vin >5V
Vin <5V
VIN + 0.3
VIN + 0.3
50
1.1.2
ISENSE voltage
VISENSE
1.1.3
1.1.4
LX output voltage
VLX
-0.3
VADJ, VADJO
,
Control pin input voltage
-0.3
6
V
RTH, RNTC
1.1.5
1.1.6
1.1.7
1.1.8
Switch output current
Power dissipation
ILX
Ptot
900
1.2
mA
W
SOP-8
Storage temperature
Junction temperature
TST
-55
150
150
°C
°C
Tj MAX
1.2. Operating Conditions
No.
1.2.1
1.2.2
PARAMETER
Operating temperature
Input voltage
SYMBOL
TOP
CONDITIONS
MIN
-40
6
TYP
MAX
+85
40
UNIT
°C
VIN
V
1.3. Electrical Parameters
Production testing is at 25°C. At other temperatures within the specified operating range, functional operation of
the chip and specified parameters are guaranteed by characterization, design, and process control.
Test conditions are Tamb = 25°C; VIN = 12V except as noted.
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
Quiescent supply current
with output off
1.3.1
IINQoff
ADJI pin grounded
40
60
80
μA
Quiescent supply current
with output switching
1.3.2
1.3.3
IINQon
ADJI pin floating
450
95
600
101
μA
Measured on ISENSE pin
with respect to VIN; ADJI pin
floating
Mean current sense
threshold voltage
VSENSE
91
mV
1.3.4
1.3.5
Sense threshold hysteresis
ISENSE pin input current
VSENSEHYS
ISENSE
±15
8
%
VSENSE = 0.1V
10
μA
Measured on ADJI pin with
pin floating
1.3.6
1.3.7
Internal reference voltage
VREF
1.2
V
V
External control voltage
range on ADJI pin for DC
brightness control
VADJI
0.3
1.2
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ZLED7010 Datasheet
No.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNIT
DC voltage on ADJI pin to
switch chip from active (ON)
state to quiescent (OFF)
state
1.3.8
VADJIoff
VADJI falling
0.15
0.2
0.25
V
DC voltage on ADJI pin to
switch chip from quiescent
(OFF) state to active (ON)
state
1.3.9
VADJIon
VADJI rising
0.2
0.25
0.3
V
RTH and RNTC pin offset
voltage
1.3.10
VOS
ILXmean
ILX(leak)
10
mV
Continuous LX switch
current
1.3.11
1.3.12
0.65
0.75
1
A
LX switch leakage current
μA
No temperature compen-
sation, ADJI pin floating
1.3.13
ADJO terminal voltage
VADJO
1.20
V
IADJO=30μA
1.3.14
1.3.15
LX Switch ON resistance
RLX
0.9
1.5
Ω
Continuous LX switch
current
ILXmean
0.65
A
Resistance between ADJI
pin and VREF
1.3.16
1.3.17
RADJI
500
kΩ
PWM frequency =100Hz
PWM amplitude=5V,
Vin=15V, L=27μH, driving
1 LED
Brightness control range at
low frequency PWM signal
DPWM(LF)
1200:1
PWM frequency =10kHz
PWM amplitude=5V,
Vin=15V, L=27μH, driving
1 LED
Brightness control range at
high frequency PWM signal
1.3.18
1.3.19
DPWM(HF)
13:1
154
ADJI pin floating L=100μH
(0.82Ω) IOUT=350mA @
VLED=3.4V, driving 1 LED
Operating frequency
fLX
kHz
1.3.20
1.3.21
Minimum switch ON time
Minimum switch OFF time
TONmin
LX switch ON
LX switch OFF
200
200
ns
ns
TOFFmin
Recommended maximum
operating frequency
1.3.22
1.3.23
fLXmax
1
MHz
Recommended duty cycle
range of output switch at
fLXmax
DLX
0.2
0.8
Internal comparator
propagation delay
1.3.24
1.3.25
1.2.26
TPD
TSD
50
140
20
ns
°C
°C
Thermal shutdown
temperature
Thermal shutdown
hysteresis
TSD-HYS
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ZLED7010 Datasheet
1.4. Characteristic Operating Curves
The curves are valid for the typical application circuit and Tamb = 25°C unless otherwise noted.
Figure 1.1
Characteristic Operating Curves 1
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ZLED7010 Datasheet
Figure 1.2
Characteristic Operating Curves 1
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ZLED7010 Datasheet
2
Circuit Description
The ZLED7010 is an inductive step-down converter for driving LEDs. It operates in continuous mode, enabling
proper LED current control. The ZLED7010 supports linear or PWM control of the LED current. It provides
temperature compensation to maintain stable and reliable operation of the LEDs. Only a few external components
are needed for typical applications.
2.1. Voltage Supply
The ZLED7010 has an internal regulator that disables the LX output until the voltage supply rises above a start-up
threshold voltage set internally as needed to ensure that the power MOSFET on-resistance is low enough for
proper operation. When the supply voltage exceeds the threshold, the ZLED7010 begins normal operation.
Important: The ZLED7010 must be operated within the operating voltage range specified in section 1.2 to avoid
conditions that could result in thermal damage to the ZLED7010. Operating with the supply voltage below the
minimum can result in a high switch duty cycle and excessive ZLED7010 power dissipation, risking over-
temperature conditions (also see section 4.1 regarding thermal restrictions) which could result in activation of the
ZLED7010’s thermal shut-down circuitry (see section 4.2). With multiple LEDs, the forward drop is typically
adequate to prevent the chip from switching below the minimum voltage supply specification (6V), so there is less
risk of thermal shut-down.
2.2. ZLED7010 Standby Mode
Whenever the ADJI pin voltage falls below 0.2V, the ZLED7010 turns the output off and the supply current drops
to approximately 60μA. This standby mode minimizes current consumption.
2.3. Output Current Control
The LED control current output on the LX pin is determined by the value of external components and the control
voltage input at the ADJI pin. Selection of the external component RS is discussed below, and other external
components are discussed in section 3. The subsequent sections describe the two options for control voltage
input at the ADJI pin: a pulse width modulation (PWM) control signal or a DC control voltage.
The ADJI pin has an input impedance† of 500kΩ ±25%.
2.3.1.
The current sense threshold voltage and the value of the external current sense resistor (RS) between VIN and
SENSE set the output current through the LEDs (IOUT). Equation (1) shows this basic relationship. Unless the ADJ
Output Current and RS
I
pin is driven from an external voltage (see section 2.3.3), the minimum value for RS is 0.13Ω to prevent exceeding
the maximum switch current (see section 1.3).
95mV
IOUT
=
(1)
RS
Where
OUT = Nominal average output current through the LED(s)
I
RS≥0.13Ω
† At room temperature.
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ZLED7010 Datasheet
2.3.2.
PWM Control
The output current on LX can be set to a value below the nominal average value determined by resistor RS by
using an external PWM signal as the control signal applied to the ADJI pin. This control signal must be capable of
driving the ZLED7010’s internal 500kΩ pull-up resistor. See Figure 2.1 for an illustration. The minimum signal
voltage range is 0V to 1.8V; the maximum voltage range is 0V to 5V. See section 1.3 for the specifications for the
signal’s duty cycle DPWM. Any negative spikes on the control signal could interfere with current control or proper
operation of the ZLED7010.
Figure 2.1
Directly Driving ADJI Input with a PWM Control Signal
1.8V to 5V
ZLED7010
0V
ADJ
ADJO
I
GND
PWM
2.3.3.
External DC Voltage Control of Output Current
The output current on LX can be set to a value below the nominal average value determined by resistor RS by
using an external DC voltage VADJ (0.3 V ≤ VADJ ≤ 1.2V) to drive the voltage at the ADJI pin. This allows adjusting
the output current from 25% to 100% of IOUTnom. See Figure 2.2 for an illustration. The output current can be
calculated using equation (2). If VADJ matches or exceeds VREF (1.2V), the brightness setting is clamped at its
maximum (100%).
Figure 2.2
External DC Control Voltage at ADJI Pin
ZLED7010
ADJI
ADJO
GND
DC
0.079∗VADJ
IOUT _ DC
=
(2)
RS
Where
OUT_DC = Nominal average output current through the LED(s) with a DC control voltage
I
VADJ = External DC control voltage: 0.3V ≤ VADJ ≤ 1.2V
RS ≥0.13Ω
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ZLED7010 Datasheet
2.3.4.
Microcontroller LED Control
The open-drain output of a microcontroller can control current to the LEDs by outputting a PWM control signal to
the ADJI input. See Figure 2.3 for an example circuit.
Figure 2.3
Driving ADJI Input from a Microcontroller
ZLED7010
10k
ADJI
ADJO
MC
GND
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ZLED7010 Datasheet
3
Application Circuit Design
3.1. External Component – Inductor L1
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. Select a coil that has a continuous current rating above the required average output
current to the LEDs and a saturation current exceeding the peak output current. Recommendation: Use inductors
in the range of 15μH to 220μH with saturation current greater than 1A for 700mA output current or saturation
current greater than 500mA for 350mA output current. For higher supply voltages with low output current, select
higher values of inductance, which result in a smaller change in output current across the supply voltage range
(refer to the graphs in section 1.4). See section 8.8 for layout restrictions.
Equations (3) and (4) illustrate calculating the timing for LX switching for the example application circuit shown on
page 2. As given in section 1.3, the minimum period for TON is 200ns; the minimum period for TOFF is also 200ns.
LX Switch OFF Time (TOFF in s)
Where
L ∗∆I
VLED +VD + IAVG
TOFF
=
(3)
(4)
L
Coil inductance in H
∗
(
RS + rL
)
∆I
Coil peak-peak ripple current in A *
Total LED forward voltage in V
VLED
VD
Diode forward voltage at the
required load current in V
LX Switch ON Time (TON in s)
IAVG
RS
Required average LED current in A
External current sense resistance in Ω
Coil resistance in Ω
L ∗∆I
VIN −VLED − IAVG
TON
=
∗
(
RS + rL + RLX
)
rL
VIN
RLX
Supply voltage in V
Switch resistance in Ω
* With the ZLED7010, the current ripple ∆I is internally set to an appropriate value of 0.3 IAVG
.
*
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 relation 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.
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ZLED7010 Datasheet
The following calculation example yields an operating frequency of 122kHz and a duty cycle of 0.33:
Input data: VIN=12V, L=220μH, rL=0.48Ω, VLED=3.4V, IAVG =333mA and VD =0.36V
220µH ∗0.3∗0.333A
TOFF
=
= 5.47µs
(5)
(6)
3.4V + 0.36V + 0.333A∗
(
0.48Ω + 0.3Ω
)
And
220µH ∗0.3∗0.333A
12V − 3.4V − 0.333A∗ 0.3Ω + 0.48Ω + 0.9Ω
TON
=
= 2.73µs
3.2. External Component – Capacitor C1
To improve system efficiency, use a low-equivalent-series-resistance (ESR) capacitor for input decoupling
because this capacitor must pass the input current AC component. The capacitor value is defined by the target
maximum ripple of the supply voltage; the value is given by equation (7).
IF ∗TON
∆VMAX
CMIN
=
(7)
Where
IF
Value of output current
ΔVMAX Maximum ripple of power supply
TON Maximum ON time of MOSFET
In the case of an AC supply with a rectifier, the capacitor value must be chosen high enough to make sure that
the DC voltage does not drop below the maximum forward voltage of the LED string plus some margin for the
voltage drops across the coil resistance, shunt resistor, and ON resistance of the switching transistor.
Recommendation: Use capacitors with X5R, X7R, or better dielectric for maximum stability over temperature and
voltage. Do not use Y5V capacitors for decoupling in this application. For higher capacitance values, aluminum
electrolytic caps with high switching capability should be used. In this case improved performance can be reached
by an additional X7R/X5R bypass capacitor of at least 100nF.
3.3. External Component – Diode D1
For the rectifier D1, select a high-speed low-capacitance Schottky diode with low reverse leakage at the
maximum operating voltage and temperature to ensure maximum efficiency and performance.
Important: Choose diodes with a continuous current rating higher than the maximum output load current and a
peak current rating above the peak coil current. When operating above 85°C, the reverse leakage of the diode
must be addressed because it can cause excessive power dissipation in the ZLED7010.
Note: Silicon diodes have a greater forward voltage and overshoot caused by reverse recovery time, which can
increase the peak voltage on the LX output. Ensure that the total voltage appearing on the LX pin, including
supply ripple, is within the specified range (see section 1.3).
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ZLED7010 Datasheet
3.4. Output Ripple
Shunt a capacitor CLED across the LED(s) as shown in Figure 3.1 to minimize the peak-to-peak ripple current in the
LED if necessary.
Figure 3.1
Output Ripple Reduction
RS
VS
D1
n LED
CLED
VIN
ISENSE
L1
ZLED7010
LX
Low-ESR capacitors should be used because the efficiency of CLED largely depends on its ESR and the dynamic
resistance of the LED(s). For an increased number of LEDs, using the same capacitor will be more effective.
Lower ripple can be achieved with higher capacitor values, but it will increase start-up delay by reducing the slope
of the LED voltage. The capacitor will not affect operating frequency or efficiency. For a simulation or bench
optimization, CLED values of a few μF are an applicable start point for the given configuration.
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ZLED7010 Datasheet
4
Operating Conditions
4.1. Thermal Conditions
Refer to section 1.1 for maximum package power dissipation specifications for the ZLED7010’s SOP-8 package.
Exceeding these specifications due to operating the chip at high ambient temperatures (see section 1.2 for
maximum operating temperature range) or driving over the maximum load current (see section 1.3) can damage
the ZLED7010. The ZLED7010 can be used for LED current applications up to750mA when properly mounted to
a high wattage land pattern. Conditions such as operating below the minimum supply voltage or inefficiency of the
circuit due to improper coil selection or excessive parasitic capacitance on the output can cause excessive chip
power dissipation.
4.2. Thermal Shut-Down Protection
The ZLED7010 includes an on-board temperature sensing circuit that stops the output if the junction exceeds approximately
160°C.
4.3. Open-Circuit Protection
The ZLED7010 is inherently protected if there is an open-circuit in the connection to the LEDs because in this
case, the coil is isolated from the LX pin. This prevents any back EMF from damaging the internal switch due to
forcing the drain above its breakdown voltage.
4.4. External Temperature Compensation of Output Current
The ZLED7010’s temperature compensation feature is useful in applications that require a temperature
compensated LED control current to ensure stability and reliability over temperature, such as high luminance
LEDs. When output current compensation is needed, use an external temperature sensing network, typically with
negative temperature coefficient (NTC) thermistors/diodes, located close to the LED(s) and connected to the RNTC
and Rth inputs. With this circuit configuration, the internal circuitry of the ZLED7010 reduces the output current if
the temperature sensing input indicates a rising temperature.
Figure 4.1
Temperature Compensation
RNTC
ZLED7010
R4
RTH
ADJI
ADJO
R3
NTC
GND
R2
As shown in Figure 4.1, the temperature compensation curve is determined by R2, R3 (NTC) and R4. When the
LED temperature increases, the resistance of R3 decreases. As R3 reaches the point that R3 plus R4 equal R2,
the temperature compensation function starts to work by reducing IOUT
.
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The IOUT current with temperature compensation can be calculated with the following equations:
For 0.3V ≤ VADJI ≤ 1.2V:
0.079V ∗VADJI
R3 + R4
(8)
(9)
IOUT _ DC
=
=
∗
RS
R2
For VADJI > 1.2V:
0.095V
RS
R3 + R4
IOUT _ DC
∗
R2
R3 and R4 determine the slope of temperature compensation. If R4 is just 0Ω, the slope is solely driven by the
NTC component’s characteristic β-constant. Larger values of R4 will decrease the slope.
When dimensioning R2, consider that larger values will make the RTH pin more noise sensitive and lower values
will increase power consumption therefore values from 1k to 100k are recommended. For a selected temperature
compensation threshold, larger R3 and R4 require larger R2 to match and vice versa.
Also see section 5 regarding driver chains and temperature compensation.
Figure 4.2 shows some examples of current-temperature curves resulting from different dimensioning of the three
resistors.
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ZLED7010 Datasheet
Figure 4.2
Temperature Compensation Graphs
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ZLED7010 Datasheet
5
Chaining Multiple ZLED7010 ICs
Figure 5.1 shows a typical circuit for chaining multiple ZLED7010s using the ADJI and ADJO pins and a
temperature sensing network of R2, R4, and R3, which is an NTC component. Note that only one temperature
sensing network is needed.
When R3+R4 > R2, VADJO = VADJI.
When R3+R4 < R2, the ADJO pin outputs the ADJI input voltage with temperature compensation information.
Figure 5.1
ZLED7010 Chain Connections
RNTC
RNTC
ZLED7010
ZLED7010
R4
RTH
RTH
ADJO
ADJI
ADJO
ADJI
R3
NTC
R2
GND
GND
100pF
100pF
100pF
100pF
In Figure 5.2, note that each ZLED7010 can drive up to three slave ICs in the next stage. Using more than three
stages to maintain current coherence is not recommended. Up to thirteen ZLED7010 can be connected in one
system.
Figure 5.2
ZLED7010 System Application
RS-2
D1-2
VS
n2 LED
RS-1
D1-1
ISENSE
VIN
RNTC
C1-2
VS
L1-2
ZLED7010
RTH
LX
ADJO
n1 LED
L1-1
R3
NTC
VIN
RNTC
ISENSE
C1-1
ADJI
GND
ZLED7010
RTH
LX
C2
ADJI
ADJO
R2
GND
RS-3
D1-3
VS
n3 LED
L1-3
VIN
RNTC
ISENSE
C1-3
ZLED7010
RTH
LX
ADJO
ADJI
GND
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ZLED7010 Datasheet
6
ESD/Latch-Up-Protection
All pins have an ESD protection of >± 2000V according the Human Body Model (HBM) except for pin 8, which has
a protection level of >± 1000V. The ESD test follows the Human Body Model with 1.5 kΩ/100 pF based on MIL
883-G, Method 3015.7.
Latch-up protection of >± 100mA has been proven based on JEDEC No. 78A Feb. 2006, temperature class 1.
7
Pin Configuration and Package
Figure 7.1
Pin Configuration ZLED7010
VIN
ISENSE
RTH
LX
GND
ADJI
ADJO
RNTC
Table 4.1
Pin Description SOP-8
No.
Pin
Name
Description
VIN
1
Supply voltage (6V to 40V)—see section 8 for layout considerations.
Nominal average output current is set by the value of a resistor RS connected from ISENSE to VIN. See
section 2.3.1 for details.
ISENSE
2
3
Threshold input from external temperature sensing network. Sets the starting temperature of temperature
compensation via an external resistor. See section 4.4 for details.
RTH
RNTC
ADJO
ADJI
GND
LX
4
NTC input from external temperature sensing network. See section 4.4 for details.
Output for control signal for LED driver chain applications
Output current control pin—see section 2.3 for details
Ground (0V)—see section 8.4 for layout considerations
Power switch drain
5
6
7
8
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ZLED7010 Datasheet
Figure 7.2
SOP-8 Package Drawing
Table 7.2
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
E
E1
e
3.800
5.800
0.100
1.450 Typical
0.350
1.270 Typical
0.490
0.250
5.000
L
0.400
0°
1.270
8°
c
0.178
θ
D
4.800
The SOP-8 package has a thermal resistance (junction to ambient) of RθJA = 128 K/W.
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ZLED7010 Datasheet
8
Layout Requirements
8.1. Layout Considerations for ADJI (Pin 6)
For applications in which the ADJI pin is unconnected, minimize the length of circuit board traces connected to
ADJI to reduce noise coupling through this high impedance input.
8.2. Layout Considerations for LX (Pin 8)
Minimize the length of circuit board traces connected to the LX pin because it is a fast switching output.
8.3. Layout Considerations for VIN (Pin 1) and the External Decoupling Capacitor (C1)
The C1 input decoupling capacitor must be placed as close as possible to the VIN pin to minimize power supply
noise, which can reduce efficiency. See section 3.2 regarding capacitor selection.
8.4. Layout Considerations for GND (Pin 7)
The ZLED7010 GND (ground) pin must be soldered directly to the circuit board’s ground plane to minimize
ground bounce due to fast switching of the LX pin.
8.5. Layout Considerations for ADJO (Pin 5)
When the application requires a driver chain of multiple ZLED7010s, noise might be coupled in if there are longer
PCB traces from the driving ADJO pin to next stage ADJI pin. In this case, a 200pF (maximum) capacitor must be
connected between the line and ground to filter out the noise. The best practice is to connect one capacitor each
close to the ADJO output pin and the next stage ADJI input pins. The total capacitance in addition to the parasitic
capacitance from the ADJO pin to ground must not exceed 200pF. See Figure 5.1.
8.6. Layout Considerations for RTH and RNTC (Pins 3 and 4)
The PCB trace from R2 to the RTH pin should be as short as possible to minimize noise coupling. Because the
NTC thermistor R3 is mounted close to the LEDs and remote from the ZLED7010, the PCB trace from R3 to RNTC
pin is longer and more susceptible to noise. A 100nF capacitor from the RNTC pin to ground and close to the RNTC
pin is recommended to filter the noise and provide protection against high voltage transients.
8.7.
Layout Considerations for High Voltage Traces
Avoid laying out any high voltage traces near the ADJ pin to minimize the risk of leakage in cases of board
contamination, which could raise the ADJ pin voltage resulting in unintentional output current. Leakage current
can be minimized by laying out a ground ring around the ADJ pin.
8.8. Layout Considerations for the External Coil (L1)
The L1 coil must be placed as close as possible to the chip to minimize parasitic resistance and inductance,
which can reduce efficiency. The connection between the coil and the LX pin must be low resistance.
8.9. Layout Considerations for the External Current Sense Resistor (RS)
Any trace resistance in series with RS must be taken into consideration when selecting the value for RS.
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9
Ordering Information
Product Sales Code Description
Package
ZLED7010ZI1R
ZLED7010KIT-D1
ZLED-PCB1
ZLED7010 – 40V LED Driver with Temperature Compensation
ZLED7010 Demo Board with LED on Cool Body 12VAC/VDC
SOP8 (Tape & Reel)
Kit
Test PCB with one 3W white HB-LED, cascadable to one multiple LED string Printed Circuit Board
ZLED-PCB2
10 unpopulated test PCBs for modular LED string with footprints of 9
common HB-LED types
Printed Circuit Board
10 Document Revision History
Revision
1.0
Date
Description
June 10, 2010
August 12, 2010
April 20, 2016
Production release version
1.1
Revision to equation (5) for Toff. Update for contact information.
Changed to IDT branding.
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
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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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Device Technology, Inc. All rights reserved.
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