Diodes ZXLD1366 User Manual

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ZXLD1366

HIGH ACCURACY 1A, 60V LED DRIVER WITH AEC-Q100

Description

The ZXLD1366 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input supply between 6V and 60V and provides an externally adjustable output current of up to 1A.

The ZXLD1366 has been qualified to AECQ100 Grade 1 enabling operation in ambient temperatures from -40°C to +125°C.

The ZXLD1366 uses a high-side output current sensing circuit which uses an external resistor to set the nominal average output current. The output current can be adjusted above, or below the set value, by applying an external control signal to the 'ADJ' pin.

Enhanced output current dimming resolution can be achieved by applying a PWM signal to the ‘ADJ’ pin.

Soft-start can be forced using an external capacitor from the ADJ pin to ground. Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and switches the device into a low current standby state.

Features

• Typically better than 0.8% output current accuracy

• Simple and with low part count

• Single pin on/off and brightness control using DC voltage or

PWM

• PWM resolution up to 1000:1

• High efficiency (up to 97%)

• Switching frequencies up to 1MHz

• Wide input voltage range: 6V to 60V

• Inherent open-circuit LED protection

• Available in thermally enhanced Green molding packages

 SO-8EP   U- DFN3030-6   TSOT25 

 Totally Lead-free & Fully RoHS Compliant (Notes 1 & 2)  Halogen and Antimony Free. “Green” Device (Note 3)

• Qualified to AEC-Q100 Grade 1

 SO-8EP ZXLD1366EN8TC  TSOT25 ZXLD1366ET5TA

= +45°C/W

JA

= +44°C/W

JA

82°C/W

JA = +

Pin Assignments

(TOP VIEW)

1

LX

2

GND

3

ADJ

TSOT25

(TOP VIEW)

LX

1

2

GND

3

ADJ

U-DFN3030-6

(TOP VIEW)

LX

1

2

GND

3

GND

4

ADJ

SO-8EP

Typical Application Circuit

D1

VIN(2 4V)

Rs

0.2V

V

5

IN

I

4

SENSE

V

6

IN

5

GND

4

I

SENSE

V

8

IN

GND

7

6

GND

I

5

SENSE

Applications

• Automotive lighting

• Low voltage industrial lighting

• LED back-up lighting

• Illuminated signs

• Emergency lighting

• SELV lighting

• Refrigeration lights

Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied.

2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green" and Lead-free.

3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds.

ZXLD1366

Document number: DS31992 Rev. 8 - 2

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GND

4.7µFC1

10 0 nF

V

ADJ

IN

I

SENSE

ZXLD1366

GND

L1

LX

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ZXLD1366

Block Diagram



V

IN

R

D1

S

L1

I

SEN SE

-

+

-

+

Low volta ge

detector

C1

4. 7µ F

Gn d

V

54 1

IN

5V

Voltage

regulator

Adj

R1

0.2V

-

+

3

R5

1.25V

50K

D1

R4

20K

600KHz

1.35V

R2

-

+

R3

2

Figure. 1 Pin Connection for TSOT25 Package

Pin Description

Name TSOT25 U-DFN3030-6 SO-8EP Function

LX 1 1 1 Drain of NDMOS switch

GND 2 2, 5 2, 3, 6, 7 Ground (0V)

Multi-function On/Off and brightness control pin:

ADJ 3

I

SENSE

VIN

4

5 6 8

3 4

4 5

Pad - Pad Pad

• Leave floating for normal operation.(V average output current I

OUTnom

• Drive to voltage below 0.2V to turn off output current

• Drive with DC voltage (0.3V < V to 200% of I

OUTnom

• Connect a capacitor from this pin to ground to set soft-start time. Soft start time increases approximately 0.2ms/nF

Connect resistor RS from this pin to VIN to define nominal average output current I

OUTnom

(Note: R

= 0.2V

SMIN

.

/RS

= 0.2V with ADJ pin open-circuit)

Input Voltage (6V to 60V). Decouple to ground with 4.7µF of higher X7R ceramic capacitor close to device.

Exposed Pad (EP) - connected to device substrate. To improve thermal impedance of package the EP must be connected to power ground but should not be used as the 0V (GND) current path. It can be left floating but must not be connected to any other voltage other than 0V.

ADJ

= 0.2V/RS)

< 2.5V) to adjust output current from 25%

ADJ

LX

MN

= V

= 1.25V giving nominal

REF

ZXLD1366

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Absolute Maximum Ratings (Note 4) (@T

Symbol Parameter Rating Unit

VIN

V

SENSE

VLX

V

ILX

P

TOP

TST

TJ

Note: 4 All voltages unless otherwise stated are measured with respect to GND.

5. V

Caution: Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only; functional operation of the device at conditions between maximum recommended operating conditions and absolute maximum ratings is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time.

ESD Susceptibility Rating Unit

Human Body Model 500 V

Machine Model 75 V

Caution: Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling and transporting these devices. The human body model is a 100pF capacitor discharge through a 1.5k resistor pin. The machine model is a 200pF capacitor discharged directly into each pin.

Input Voltage -0.3 to +65 V

I

Voltage (Note 5)

SENSE

LX Output Voltage -0.3 to +65 V

Adjust Pin Input Voltage -0.3 to +6 V

ADJ

Switch Output Current 1.25 A

Power Dissipation (Refer to Package thermal de-rating curve on

TOT

page 25)

Operating Temperature -40 to +125 °C

Storage Temperature -55 to +150 °C

Junction Temperature +150 °C

MAX

is measured with respect to V

SENSE

.

IN

= +25°C, unless otherwise specified.)

A

+0.3 to -5 V

TSOT25 1

U-DFN3030-6 1.8

SO-8EP 2.2

ZXLD1366

W

Thermal Resistance

Symbol Parameter

JA

JB

JC

Junction to Ambient 82 45 44

Junction to Board 33 — —

Junction to Case — 7 14

TSOT25 SO-8EP U-DFN3030-6

Rating

Unit

°C/W

Recommended Operating Conditions

Symbol Parameter Min Max Units

Input voltage (Note 6) 6 60 V

VIN

Maximum recommended continuous/RMS switch current 1 A

ILX

V

ADJOFF

t

OFFMIN

t

ONMIN

f

LX MAX

D

LX(LIMIT)

TOP

Notes: 6. VIN > 16V to fully enhance output transistor. Otherwise out current must be derated - see graphs. Operation at low supply may cause excessive heating due to increased on-resistance. Tested at 7V guaranteed for 6V by design.

7. 100% brightness corresponds to V proportionally.

8. ZXLD1366 will operate at higher frequencies but accuracy will be affected due to propagation delays.

ZXLD1366

Document number: DS31992 Rev. 8 - 2

External control voltage range on ADJ pin for DC brightness control (Note 7) 0.3 2.5 V

ADJ

DC voltage on ADJ pin to ensure devices is off 0.25 V

Minimum switch off-time

Minimum switch on-time

Recommended maximum operating frequency (Note 8)

Duty cycle range 0.01 0.99

DLX

Recommended duty cycle range of output switch at f

LXMAX

800 ns

625 kHz

0.3 0.7

Operating Temperature range -40 +125 °C

ADJ

= V

ADJ(nom)

= V

. Driving the ADJ pin above V

REF

will increase the V

REF

threshold and output current

SENSE

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Electrical Characteristics (Test conditions: (@ V

Symbol Parameter Condition Min Typ Max Unit

VSU

VSD

I

INQoff

I

INQon

V

SENSE

V

SENSEHYS

I

SENSE

V

REF

ΔV

REF

V

ADJ

V

ADJoff

V

ADJon

R

ADJ

I

LXmean

RLX

I

LX(leak)

D

PWM(LF)

Brightness control range 1000:1

DC

ADJ

tSS

fLX

t

ONmin

t

OFFmin

Notes: 9. Static current of device is approximately 700 µA, see Graph, Page 16

10. 100% brightness corresponds to V proportionally.

11. Ratio of maximum brightness to minimum brightness before shutdown V

ZXLD1366

Document number: DS31992 Rev. 8 - 2

Internal regulator start-up threshold 4.85 5.20 V

Internal regulator shutdown threshold 4.40 4.75 V

Quiescent supply current with output off ADJ pin grounded 65 108 µA

Quiescent supply current with output switching (Note 9)

Mean current sense threshold voltage (Defines LED current setting accuracy)

Sense threshold hysteresis ±15 %

I

/ΔT Temperature coefficient of V

Resistance between ADJ pin and V

pin input current V

SENSE

Internal reference voltage

REF

External control voltage range on ADJ pin for DC brightness control (Note 7)

DC voltage on ADJ pin to switch device from active (on) state to quiescent (off) state

DC voltage on ADJ pin to switch device from quiescent (off) state to active (on) state

REF

Continuous LX switch current 1 A

LX switch ‘On’ resistance

LX switch leakage current 5 µA

Duty cycle range of PWM signal applied to ADJ pin during low frequency PWM dimming mode

DC Brightness control range (Note 8) 5:1

Soft start time

Operating frequency (See graphs for more details)

Minimum switch ‘ON’ time LX switch ‘ON’ 130

Minimum switch ‘OFF’ time LX switch ‘OFF’ 70

ADJ

= V

ADJ(nom)

= V

= 24V, TA = +25°C, unless otherwise specified.)

IN

ADJ pin floating, L = 68µH, 3 LEDs, f = 260kHz

Measured on I respect to V

= 18V

V

IN

= V

SENSE

IN

SENSE

IN VADJ

-0.2

pin with

= 1.25V;

Measured on ADJ pin with pin floating

50 ppm/°C

0.3 2.5 V

V

falling

ADJ

V

rising

ADJ

0 < V V

ADJ

> V

< V

REF

+100mV

REF

@ ILX = 1A

PWM frequency < 300Hz PWM amplitude = V

REF

Measured on ADJ pin

Time taken for output current to reach 90% of final value after voltage on ADJ pin has risen above 0.3V. Requires external capacitor 22nF. See graphs for more details

ADJ pin floating L = 68µH (0.2V)

I

OUT

= 1A @ V

LED

= 3.6V

Driving 3 LEDs

. Driving the ADJ pin above V

REF

= 1.25/0.3. V

REF

will increase the V

REF

externally driven to 2.5V, ratio 10:1.

REF

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1.6 mA

195 200 205 mV

4 10 µA

1.25 V

0.15 0.20 0.27 V

0.20 0.25 0.30 V

30

10.4

0.50 0.75 

0.001 1.000 V

2 ms

260 kHz

threshold and output current

SENSE

ZXLD1366

50

14.2

65

18.0

k

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ZXLD1366

Device Description

The device, in conjunction with the coil (L1) and current sense resistor (RS), forms a self-oscillating continuous-mode buck converter.

Device Operation

(refer to Figure 1 - Block diagram and Figure 2 Operating waveforms).

V

IN

LX voltage

SENSE voltage

Coil current

Comparator input voltage

Comparator output

0V

V

IN

0V

0.15V

V

ADJ

5V

0V

ADJ

Tof f Ton

170mV

200mV230mV

V

SENSE-

V

SENSE+

I

+15%

OUTnom

I

OUTnom

I

-15%

OUTnom

0.15V

ADJ

Figure 2 Theoretical Operating Waveforms

Operation can be best understood by assuming that the ADJ pin of the device is unconnected and the voltage on this pin (V

) appears

ADJ

directly at the (+) input of the comparator.

When input voltage V

is first applied, the initial current in L1 and RS is zero and there is no output from the current sense circuit. Under this

IN

condition, the (-) input to the comparator is at ground and its output is high. This turns MN on and switches the LX pin low, causing current to

flow from V

across R

to ground, via RS, L1 and the LED(s). The current rises at a rate determined by VIN and L1 to produce a voltage ramp (V

IN

. The supply referred voltage V

S

is forced across internal resistor R1 by the current sense circuit and produces a proportional

SENSE

current in internal resistors R2 and R3. This produces a ground referred rising voltage at the (-) input of the comparator. When this reaches

the threshold voltage (V

which bypasses internal resistor R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of V

), the comparator output switches low and MN turns off. The comparator output also drives another NMOS switch,

ADJ

.

When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to V

and diode forward voltages to produce a falling voltage at the input of the comparator. When this voltage returns to V

output switches high again. This cycle of events repeats, with the comparator input ramping between limits of V

. The current decays at a rate determined by the LED(s)

IN

, the comparator

ADJ

± 15%.

ADJ

Switching Thresholds

With V

respect to V

I

OUTnom

Nominal ripple current is ±30mV/R

= V

ADJ

= 200mV/R

, the ratios of R1, R2 and R3 define an average V

REF

). The average output current I

IN

S

switching threshold of 200mV (measured on the I

SENSE

is then defined by this voltage and RS according to:

OUTnom

S

SENSE

pin with

)

ZXLD1366

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ZXLD1366

Device Description (cont.)

Actual operating waveforms

= 15V, R

V

IN

Output Current (Ch 3) and LX voltage (Ch 2)

= 0.2Ω, L = 68µH Normal operation.

S

V

= 30V, R

IN

Output Current (Ch 3) and LX voltage (Ch 2)

= 0.2Ω, L = 68µH Normal operation.

S

V

= 60V, R

IN

Output Current (Ch 3) and LX voltage (Ch 2)

= 0.2Ω, L = 68µH Normal operation.

S

Adjusting Output Current

The device contains a low pass filter between the ADJ pin and the threshold comparator and an internal current limiting resistor (50k nom)

between ADJ and the internal reference voltage. This allows the ADJ pin to be overdriven with either DC or pulse signals to change the

switching threshold and adjust the output current.

V

SENSE

Details of the different modes of adjusting output current are given in the applications section.

Output Shutdown

The output of the low pass filter drives the shutdown circuit. When the input voltage to this circuit falls below the threshold (0.2V nom.), the

internal regulator and the output switch are turned off. The voltage reference remains powered during shutdown to provide the bias current

for the shutdown circuit. Quiescent supply current during shutdown is nominally 60A and switch leakage is below 5A.

ZXLD1366

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T

PUT CURRENT

A

0

OUT

PUT CUR

RENT

A

TIO

F

FIC

C

Y

Diodes Incorporated

ZXLD1366

Typical Operating Conditions

SUPPLY VOLTAGE (V)

) (

1.100

1.080

1.060

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L E Ds 13 LEDs 15 LEDs

1.040

1.020

OU

1.000

0.980 0 10 20 30 40 50 60

Output Current, L = 68µH

1

8

6

N (%)

4

2

DEVI

0

-2

-4

-6

-8

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L EDs 13 LEDs 15 LEDs

-10 0 102030405060

SUPPLY VOLTAGE (V)

Output Current Deviation, L = 68µH

100

1 LED

95

90

85

(%)

80

75

IEN

3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L E Ds 13 LEDs 15 LEDs

70

E

65

60

55

50

0 102030405060

SUPPLY VOLTAGE (V)

Efficiency, L = 68µH

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TCH

N

G F

R

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UENCY

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U

T

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ZXLD1366

Typical Operating Conditions (cont.)

500

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L E Ds 13 LEDs 15 LEDs

z)

(k

E

I

SWI

450

400

350

300

250

200

150

100

50

0

0 102030405060

SUPPLY VOLTAGE (V)

Switching Frequency, L = 68µH

100

90

80

70

60

LE (%)

50

40

D

30

20

10

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L ED s 13 LEDs 15 LEDs

0

0 102030405060

SUPPLY VOLTAGE (V)

Duty Cycle, L = 68µH

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OUTP

C

R

A

OUT

PUT CUR

RENT

A

TIO

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ZXLD1366

Typical Operating Conditions (cont.)

1.100

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L ED s 13 LEDs 15 LEDs

)

ENT (

1.080

1.060

1.040

U

1.020

UT

1.000

0.980

0.960 0 102030405060

SUPPLY VOLTAGE (V)

Output Current, L = 100µH

10

8

6

N (%)

4

2

DEVI

0

-2

1 LED 3 LEDs

-4

5 LEDs 7 LEDs

-6

9 LEDs 11 L E Ds 13 LEDs

-8

-10

15 LEDs

0 102030405060

SUPPLY VOLTAGE (V)

Output Current Deviation, L = 100µH

1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs 11 L ED s 13 LEDs 15 LEDs

0 102030405060

SUPPLY VOLTAGE (V)

Efficiency, L = 100µH

ZXLD1366

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