Diodes ZXLD1360 User Manual

A

Product Line o

f

Diodes Incorporated

ZXLD1360

30V 1A LED DRIVER with AEC-Q100

Description

The ZXLD1360 is a continuous mode inductive step-down converter with integrated switch and high side current sense.

It operates from an input supply from 7V to 30V driving single or multiple series connected LEDs efficiently externally adjustable output current up to 1mA.

The ZXLD1360 has been qualified to AEC-Q100 Grade 1 enabling operation in ambient temperatures from -40°C to 125°C.

The output current can be adjusted by applyi ng a DC voltage or a PWM waveform to the ADJ pin; 100:1 adjustment of output current is possible using PWM control. Applying

0.2V or lower to the ADJ pin turns the output off and switches the device into a low current standby state.

Features

• Simple low parts count

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

or PWM

• High efficiency (up to 95%)

• Wide input voltage range: 7V to 30V

• 40V transient capability

• Qualified to AEC-Q100 Grade 1

• Available in thermally enhanced packages

o TSOT23-5 θ

• Available in Green molding (no Br, Sb) with lead free finish/RoHS compliant

• Up to 1MHz switching frequency

• Typical 4% output current accuracy

JA

82° C/W

Pin Assignments

LX

GND

ADJ

TSOT23-5

Top Vi ew

Typical Application Circuit

R

S

V

ADJ

0.1Ω

IN

S

SET

ZXLD1360

GND

VIN`

7~30V

C1

4.7µF

GND

V

IN

I

SENSE

L1

47µH

LX

ZXLD1360

Document number: DS33471 Rev. 4 - 2

1 of 25

www.diodes.com

March 2011

A

f

Block Diagram

Product Line o

Diodes Incorporated

ZXLD1360

D1

V

IN

C1

4.7µF

ADJ

Voltage

regulator

5V

R

S

V

54 1

IN

R1

0.2V

SENSE

L1

``

Low voltage

detector

LXI

MN

3

R5

R4

200k

1.25V

GND

20k

D1

1.35V

2

R2

R3

Figure 1. Block diagram – With Pin Connections

Pin Descriptions

Name Pin No. Description

LX 1 Drain of NDMOS switch

GND 2 Ground (0V)

Multi-function On/Off and brightness control pin:

• Leave floating for normal operation.(V o I

OUTnom

= 0.1/RS)

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

ADJ 3

• Drive with DC voltage (0.3V < V

OUTnom

I

ADJ

• Drive with PWM signal from open-collector or open-drain transistor, to adjust output current.

• Adjustment range 25% to 100% of I

500Hz

• Connect a capacitor from this pin to ground to increase soft-start time.

(Default soft-start time = 500µs. Additional soft-start time is approximately 500µs/nF)

I

SENSE

VIN

4

5

ZXLD1360

Document number: DS33471 Rev. 4 - 2

Connect resistor RS from this to VIN to define nominal average output current I (Note: R

=0.1V with ADJ pin open circuit)

SMIN

Input voltage (7V to 30V). Decouple to ground with 4.7µF of higher X7R ceramic capacitor close to device

2 of 25

www.diodes.com

ADJ

= V

= 1.25V giving nominal average output current

REF

< 2.5V) to adjust output current from 25% to 200% of

for f>10kHz and 1% to 100% of I

OUTnom

=0.1/RS

for f <

March 2011

A

Product Line o

f

Diodes Incorporated

ZXLD1360

Absolute Maximum Ratings (Voltages to GND Unless Otherwise Stated)

Symbol Parameter Rating Unit

VIN

V

SENSE

VLX

V

ADJ

ILX

P

TOT

TST

TJ

MAX

These are stress ratings only. Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability.

Input Voltage

I

SENSE

Voltage

LX Output Voltage Adjust Pin Input Voltage -0.3 to +6 V

Switch Output Current 1.25 A Power Dissipation

(Refer to Package thermal de-rating curve on page 20)

Storage Temperature -55 to 150 °C Junction Temperature 150 °C

ESD Susceptibility

Rating Unit

Human Body Model 500 V Machine Model <100 V

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

-0.3 to +30

(40V for 0.5 sec)

+0.3 to -5

(measured with respect to VIN)

-0.3 to +30

(40V for 0.5 sec)

1 W

V V V

Thermal Resistance

Symbol Parameter Rating Unit

θ

JA



JB

Junction to Ambient 82

°C/W

Junction to Board 33 °C/W

Recommended Operating Conditions

Symbol Parameter Min Max Units

VIN ILX

V

ADJ

V

ADJoff

t

ONmin_REC

f

LX max

DLX

TA

Notes: 1. ZXLD1360 will operate at higher frequencies but due to propagation delays accuracy will be affected.

2.100% brightness corresponds to V current proportionally.

Input Voltage Range 7 30 V Maximum recommended continuous/RMS switch current 1 A

External control voltage range on ADJ pin for DC brightness control (Note 2)

DC voltage on ADJ pin to ensure devices is off 0.25 V Recommended minimum switch “ON” time 800 ns Recommended maximum operating frequency (Note 1) 625 kHz

0.3 2.5 V

Duty cycle range 0.01 0.99 Ambient operating temperature range -40 125 °C

ADJ

= V

ADJ(nom)

= V

(~1.25V). Driving the ADJ pin above V

REF

will increase the V

REF

SENSE

threshold and output

ZXLD1360

Document number: DS33471 Rev. 4 - 2

3 of 25

www.diodes.com

March 2011

A

Product Line o

f

Diodes Incorporated

ZXLD1360

Electrical Characteristics (Test conditions: V

= 12V, TA = 25°C, unless otherwise specified. Note 3)

IN

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)

Internal regulator start-up threshold Internal regulator shutdown threshold Quiescent supply current with output off ADJ pin grounded 20 40 µA

Quiescent supply current with output switching

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

Sense threshold hysteresis ±15 %

I

pin input current V

SENSE

Internal reference voltage

/ΔT Temperature coefficient of V

External control voltage range on ADJ pin for DC brightness control (Note 2)

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

Resistance between ADJ pin and V

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

D

PWM(LF)

pin during low frequency PWM dimming mode Brightness control range 100:1 Duty cycle range of PWM signal applied to ADJ

D

PWM(HF)

pin during high frequency PWM dimming mode Brightness control range 5:1

REF

VIN rising VIN falling

ADJ pin floating f=250kHz Measured on I with respect to V

= 1.25V

V

ADJ

SENSE

= VIN-0.1

IN

Measured on ADJ pin with pin floating

5.65 V

5.55 V

1.8 5.0 mA

95 100 105 mV

1.25 10 µA

1.25 V

50 ppm/°C

0.3 2.5 V

falling

V

ADJ

rising

V

ADJ

0 < V V

ADJ

> V

< V

REF

+100mV

REF

@ ILX=0.55A

PWM frequency <500Hz PWM amplitude = V

REF

0.15 0.2 0.25 V

0.2 0.25 0.3 V

135

13.5

250

25

0.5 1.0 

0.01 1

Measured on ADJ pin PWM frequency >10kHz

PWM amplitude = V

REF

0.16 1

Measured on ADJ pin Time taken for output

current to reach 90% of final value after voltage on ADJ pin has risen

500 µs

tSS

Soft start time

above 0.3V ADJ pin floating

fLX

Operating frequency (See graphs for more details)

L = 33µH (0.093V)

= 1A @ V

I

OUT

LED

= 3.6V

280 kHz

Driving 1 LED

t

OFFMIN

t

ONMIN

tPD

Notes: 3. Production testing of the device is performed at 25°C. Functional operation of the device and parameters spe cifi ed over a -40°C to +125°C temperature range, are guaranteed by design, characterization and process control.

Minimum switch off-time 200 ns Minimum switch on-time 240 ns Internal comparator propagation delay 50 ns

k

ZXLD1360

Document number: DS33471 Rev. 4 - 2

4 of 25

www.diodes.com

March 2011

A

Product Line o

f

Diodes Incorporated

ZXLD1360

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)

Operation can be best understood by assuming that the ADJ pin of the device is unconnected and the voltage on this pin (VADJ) appears directly at the (+) input of the comparator.

When input voltage V circuit. Under this 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 by VIN and L1 to produce a voltage ramp (V

resistor R1 by the current sense circuit and produces a proportional current in internal resistors R2 and R3. T his produces a ground referred rising voltage at the (-) input of the comparator. When this reaches the threshold voltage (V

comparator output switches low and MN turns off. The comparator output also drives another NMOS switch, which bypasses internal resistor R3 to provide a controlled amount of hysteresis. The hysteresis is set by R3 to be nominally 15% of V

When MN is off, the current in L1 continues to flow via D1 and the LED(s) back to V determined by the LED(s) and diode forward voltages to produce a falling voltage at the input of the co mparator. When this

voltage returns to V ramping between limits of V

Switching thresholds

With V I

SENSE

I

OUTnom

Nominal ripple current is ±15mV/RS

= V

ADJ

REF

pin with respect to VIN). The average output current I

= 100mV/RS

Adjusting output current

The device contains a low pass filter between the ADJ pin and the threshold comparator and an internal current limiting resistor (200kV nom) between ADJ and the internal reference voltage. T his allows the ADJ pin to be overdriven with either

DC or pulse signals to change the V comprising three sections, each with a cut-off frequency of nominally 4kHz.

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 shutdo wn 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. Quiesce nt supply current during shutdown is nominally 20mA and switch leakage is below 5mA.

ZXLD1360

Document number: DS33471 Rev. 4 - 2

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

IN

to ground, via RS, L1 and the LED(s). The current rises at a rate determined

IN

) across RS. The supply referred voltage V

SENSE

IN

, the comparator output switches high again. This cycle of events repeats, with the comparator inpu t

ADJ

± 15%.

ADJ

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

is then defined by this voltage and RS according to:

OUTnom

switching threshold and adjust the output current. The filter is third order,

SENSE

5 of 25

www.diodes.com

switching threshold of 100mV (measured on the

SENSE

is forced across internal

SENSE

. The current decays at a rate

), the

ADJ

.

ADJ

March 2011

A

f

Device Description

Product Line o

Diodes Incorporated

ZXLD1360

SENSE voltage

Coil current

Comparator input voltage

Comparator output

LX voltage

V

IN

0V

V

IN

0V

0.15V

ADJ

V

ADJ

5V

0V

Toff Ton

85mV

100mV115mV

V

SENSE-

V

SENSE+

0.15V

I

OUTnom

I

OUTnom

I

OUTnom

ADJ

+15%

-15%

Figure 2. Operating Waveforms

ZXLD1360

Document number: DS33471 Rev. 4 - 2

6 of 25

www.diodes.com

March 2011

A

Product Line o

f

Diodes Incorporated

ZXLD1360

Device Description (cont.)

Actual operating waveforms [VIN=15V, RS=0.1V, L=33µH]

Normal operation. Output current (Ch1) and LX voltage (Ch2)

Actual operating waveforms [V

Normal operation. Output current (Ch1) and LX voltage (Ch2)

ZXLD1360

Document number: DS33471 Rev. 4 - 2

=30V, RS=0.1V, L=33µH]

IN

7 of 25

www.diodes.com

March 2011

A

f

y

Typical Operating Characteristics

Product Line o

Diodes Incorporated

ZXLD1360

1060

1040

1020

1000

980

960

Output Current (mA)

940

920

900

0 510

600

500

ZXLD1360 Output Current

ZXLD1360 Switching Frequenc

L = 33µH

15

20 25 30 35

Supply Voltage V (V)

L = 33µH

IN

5 LEDs4 LEDs3 LEDs2 LEDs1 LED

10%

8% 6%

4% 2% 0%

-2%

-4%

Output Current Deviation (%)

-6%

-8%

-10% 0 510

8 LEDs7 LEDs6 LEDs

100

90

80

ZXLD1360 Output Current

L = 33µH

15

20 25 30 35

Supply Voltage V (V)

ZXLD1360 Duty Cycle

L = 33µH

IN

5 LEDs4 LEDs3 LEDs2 LEDs1 LED

8 LEDs7 LEDs6 LEDs

400

300

200

Switching Frequency (kHz)

100

0

0 510

15

20 25 30 35

Supply Voltage V (V)

IN

5 LEDs4 LEDs3 LED s2 LEDs1 LED

8 LEDs7 LEDs6 LEDs

70 60 50

40

Duty Cycle (%)

30 20 10

0

0 510

15

20 25 30 35

Supply Voltage V (V)

IN

5 LEDs4 LEDs3 LEDs2 LEDs1 LED

8 LEDs7 LEDs6 LEDs

ZXLD1360

Document number: DS33471 Rev. 4 - 2

8 of 25

www.diodes.com

March 2011