Diodes ZXLD1374 User Manual

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ZXLD1374

60V HIGH ACCURACY 1.5A BUCK/BOOST/BUCK-BOOST

LED DRIVER CONVERTER WITH AEC-Q100

Description

The ZXLD1374 is a 60V LED driver with integrated 1.5A low side

switch to drive high current LEDs. It is a multi-topology converter

enabling it to operate in Buck, Boost and Buck-boost configurations;

efficiently controlling the current of up to 16-series connected LEDs.

The ZXLD1374 is a modified hysteretic converter using a patent

pending control scheme providing high output current accuracy in all

three topologies. High accuracy dimming is achieved through

DC control and high frequency PWM control.

The ZXLD1374 uses two pins for fault diagnosis. A flag output

highlights a fault, while the multi-level status pin gives further

information on the exact fault.

The ZXLD1374 has been qualified to AEC-Q100 Grade 1 enabling

operation in ambient temperatures from -40 to +125°C

.

Features

• 0.5% Typical Output Current Accuracy

• 6.3 to 60V Operating Voltage Range

• 1.5A Integrated Low Side Switch

• LED Driver Supports Buck, Boost and Buck-Boost Topologies

• Wide Dynamic Range Dimming

• 20:1 DC Dimming

• 1000:1 Dimming Range at 500Hz

• Up to 1MHz Switching

• High Temperature Control of LED Current Using TADJ

• AEC-Q100 Grade 1

• TSSOP-20EP: Available in “Green” Molding Compound (No Br,

Sb) with lead Free Finish/ RoHS Compliant

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

Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.

2. See http://www.diodes.com 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.

Pin Assignments

ADJ 1

REF 2

TA D J 3

SHP 4

STATUS 5

SGND 6

PGND 7

PGND 8

N/C 9

N/C 10

Thermal

Pad

20 GI

19 PWM

18 FLAG

17 ISM

16 VIN

15 VAUX

14 LX

13 LX

12 N/C

11 N/C

Typical Applications Circuit

V

IN

GND

C1

RGI2

R4

TH1

VAUX V IN IS M

PWM GI

ADJ

REF TADJ

SHP SGND PGND

C2 100pF

ZXLD1374

NC

R1

STATUS

LX LX

FLAG

L1

SD1

PSD3200

C

OUT

ZXLD1374

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Pin Descriptions

Name

ADJ 1 I

REF 2 O Internal 1.25V reference voltage output

T

ADJ

3 I

SHP 4 I/O

STATUS 5 O

SGND 6 P

PGND 7, 8 P

N/C 9, 10, 11, 12 —

LX 13, 14 O Low-Side Power-Switch Output

V

VIN

AUX

15 P

16 P

ISM 17 I

FLAG 18 O

PWM 19 I

GI 20 I

EP PAD P

Note: 4. Type refers to whether or not pin is an Input, Output, Input/Output or Power supply pin.

ZXLD1374

Document number: DS35032 Rev. 3 - 2

Type

(Note 4)

Function

Adjust Input (for DC Output Current Control). Connect to REF to set 100% output current.

Drive with dc voltage (125mV<V ADJ pin has an internal clamp that limits the internal

< 2.5V) to adjust output current from 10% to 200% of set value. The

ADJ

node to less than 3V. This prevents the LED and power

switch from delivering too much current should ADJ get overdriven.

Temperature Adjust (Input for LED Thermal Current Control). Connect thermistor/resistor network to this pin to reduce output current above a preset temperature threshold.

Connect to REF to disable thermal compensation function (See section on thermal control).

Shaping capacitor for feedback control loop. Connect 100pF ±20% capacitor from this pin to ground to provide loop compensation

Operation Status Output (analog output). Pin is at 4.5V (nominal) during normal operation. Pin switches to a lower voltage to indicate specific operation warnings or fault conditions (See section on

STATUS output). Status pin voltage is low during shutdown mode.

Signal Ground. Connect to 0V and pins 7 and 8.

Power Ground. Connect to 0V and pin 6 to maximize copper area.

Not Connected Internally. To maximize PCB copper for thermal dissipation connect to pins 7 and 8.

Auxiliary Positive Supply to Internal Switch Gate Driver. Connect to V

, or auxiliary supply from 6V to 15V supply to reduce internal power dissipation (Refer to

IN

application section for more details).

>24V; to reduce power dissipation, V

At V

IN

can be connected to a 12V to 15V auxiliary power supply

AUX

(see Applications section). Decouple to ground with capacitor close to device (refer to Applications section).

Input Supply to Device (6.3V to 60V). Decouple to ground with capacitor close to device (refer to Applications section).

Current Monitor Input. Connect current sense resistor between this pin and V The nominal voltage, V

, across the resistor is 218mV fixed in Buck mode and initially 225mV in Boost

SENSE

IN.

and Buck-Boost modes, varying with duty cycle.

Flag Open Drain Output. Pin is high impedance during normal operation. Pin switches low to indicate a fault, or warning condition.

Digital PWM Output Current Control. Pin driven either by open Drain or push-pull 3.3V or 5V logic levels. Drive with frequency higher than 100Hz to gate output ‘on’ and ‘off’ during dimming control. The device enters standby mode when PWM pin is driven with logic low level for more than 15ms nominal (Refer to application section for more details).

Gain Setting Input. Used to set the LED current in Boost and Buck-Boost modes. In

Buck mode operation the GI pin must be connected to ADJ.

For

Boost and Buck-boost modes, connect to resistive divider from ADJ to SGND. This defines the ratio of

switch current to LED current (see application section). The GI pin has an internal clamp that limits the internal

node to less than 3V. This provides some failsafe should the GI pin get overdriven.

Exposed Pad. Connect to 0V plane for electrical and thermal management.

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Functional Block Diagram

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ZXLD1374

Document number: DS35032 Rev. 3 - 2

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Absolute Maximum Ratings (Voltages to GND unless otherwise specified.)

Symbol Parameter Rating Unit

‡

-0.3 to +65 V

‡

-0.3 to +65 V

‡

-0.3 to +65 V

)

ISM

‡

-0.3 to +65 V

-0.3 to +5 V

V

PWM

, V

VIN

V

AUX

V

ISM

V

Current Monitor Sense Voltage (VIN-V

SENSE

VLX

ILX

I

STATUS

V

FLAG

, V

ADJ

TADJ

Input Supply Voltage Relative to GND

Auxiliary Supply Voltage Relative to GND

Current Monitor Input Relative to GND

Low Side Switch Output Voltage to GND

Low Side Switch Continuous Output Current 1.8 A

Status Pin Output Current ±1 mA

Flag Output Voltage to GND (Note 5) -0.3 to +40 V

Other Input Pins to GND (Note 5) -0.3 to +5.5 V

, VGI

ESD HBM Human Body Model ESD Protection 500 V

ESD CDM Charged Device Model ESD Protection 1000 V

TJ

TST

Note: 5. For correct operation SGND and PGND should always be connected together.

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

Maximum Junction Temperature 150 °C

Storage Temperature -55 to +150 °C

Package Thermal Data

Junction-to-Ambient, JA (Note 6)

Junction-to-Case, JC

Note: 6. Measured on High Effective Thermal Conductivity Test Board" according JESD51.

ZXLD1374

Document number: DS35032 Rev. 3 - 2

Thermal Resistance Package Unit

TSSOP-20EP

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28 °C/W

4 °C/W

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Recommended Operating Conditions (@T

Symbol Parameter Performance/Comment Min Max Unit

Input Supply Voltage Range

VIN

V

SENSE

V

I

STATUS

I

V

f

t

PWMH/L

V

Notes: 7. Device is guaranteed to have started up by 6.5V and as such the minimum applied supply voltage has to be above 6.5V (plus any noise margin). The ZXLD1374 will, however, continue to function when the input voltage is reduced from ≥ 8V down to 6.3V. When operating with input voltages below 8V the output current and device parameters may deviate from their normal values; and is dependent on power MOSFET switch, load and ambient temperature conditions. To ensure best operation in Boost and Buck-boost modes with input voltages, V between 6.5 and 12V a suitable boot-strap network on V V

8. V be applied to V

9. The device contains circuitry to control the switching frequency to approximately 400kHz. The maximum and minimum operating frequency is not tested.

ZXLD1374

Document number: DS35032 Rev. 3 - 2

Auxiliary Supply Voltage Range (Note 8)

AUX

Differential Input Voltage

Low Side Switch Output Voltage 60 V

VLX

Low Side Switch Continuous Output Current 1.5 A

ILX

External DC Control Voltage Applied to ADJ Pin to

ADJ

Adjust Output Current

Status Pin Output Current 100 µA

Reference External Load Current REF sourcing current 1 mA

REF

Recommended Switching Frequency Range (Note 9) 300 1000 kHz

fSW

Temperature Adjustment (T

TADJ

Recommended PWM Dimming Frequency Range

PWM

PWM Pulse Width in Dimming Mode PWM input high or low 0.005 10 ms

PWM Pin High Level Input Voltage 2 5.5 V

PWMH

PWM Pin Low Level Input Voltage 0 0.4 V

PWML

Operating Junction Temperature Range -40 +125 °C

TJ

) Input Voltage Range

ADJ

GI Gain Setting Ratio for Boost and Buck-Boost Modes

) below 8V. – A boot-strap network cannot be implemented in buck mode.

AUX

can be driven from a voltage higher than VIN to provide higher efficiency at low VIN voltages, but to avoid false operation; a voltage should not

AUX

in the absence of a voltage at VIN.

AUX

= +25°C, unless otherwise specified.)

A

Normal operation 8

Reduced performance operation (Note 7) 6.3

Normal operation 8

Reduced performance operation (Note 7) 6.3

V

VIN-VISM

, with 0  V

ADJ

 2.5

DC brightness control mode from 10% to 200%

0 450 mV

0.125 2.5 V

0

60 V

V

REF

V

To maintain 1000:1 resolution 100 500 Hz

To maintain 200:1 resolution 100 1000 Hz

Ratio= V

pin is recommended. Performance in Buck mode will be reduced at input voltages (VIN,

AUX

GI/VADJ

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0.20 0.50

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Electrical Characteristics (V

Symbol Parameter Conditions Min Typ Max Units

IN

= V

= 12V, @TA = +25°C, unless otherwise specified.)

AUX

Supply and Reference Parameters

V

I

Q-IN

I

Q-AUX

I

SB-IN

I

SB-AUX

V

ΔV

V

REF_LINE

V

REF-TC

Under-Voltage Detection Threshold

UV-

Normal Operation to Switch Disabled

Under-Voltage Detection Threshold

UV+

Switch Disabled to Normal Operation

Quiescent Current into VIN

Quiescent Current into V

Standby Current into VIN.

Standby Current into V

Internal Reference Voltage No load 1.237 1.25 1.263 V

REF

Change in Reference Voltage with Output

REF

Current

Reference Voltage Line Regulation

Reference Temperature Coefficient

AUX

VIN or V

falling (Note 10)

AUX

rising (Note 10)

AUX

PWM pin floating.

.

Output not switching

PWM pin grounded for more than 15ms

5.2 5.6 6.3

5.5 6 6.5

1.5 3

150 300

90 150

0.7 10

Sourcing 1mA -5

Sinking 25µA 5

VIN = V

, 6.5V < VIN = <60V

AUX

-60 -90

+/-50

V

mA

µA

mV

dB

ppm/°C

DC-DC Converter Parameters

V

ADJ

I

ADJ

VGI

IGI

I

PWM

t

PWMoff

T

SDH

T

SDL

External DC Control Voltage Applied to ADJ Pin to Adjust Output Current (Note 11)

ADJ Input Current (Note 11)

GI Voltage Threshold for Boost and Buck-Boost Modes Selection (Note 11)

GI Input Current (Note 11)

PWM Input Current

PWM Pulse Width (to enter shutdown state)

Thermal Shutdown Upper Threshold (LX output inhibited)

Thermal Shutdown Lower Threshold (LX output re-enabled)

DC brightness control mode 10% to 200%

 2.5V

V

ADJ

= 5.0V

V

ADJ

V

= 1.25V

ADJ

 2.5V

V

GI

= 5.0V

V

GI

V

= 5.5V

PWM

0.125 1.25 2.5 V

100

5

nA µA

0.8 V

100

5

nA µA

36 100 µA

PWM input low 10 15 25 ms

Temperature rising 150 °C

Temperature falling 125 °C

High-Side Current Monitor (Pin ISM)

I

ISM

V

SENSE_acc

V

SENSE-OC

Notes: 10. UVLO levels are such that all ZXLD1374 will function above 6.5V for rising supply voltages and function down to 6.3V for falling supply voltages.

overdriven.

Input Current

Accuracy of Nominal V

Over-Current Sense Threshold Voltage 300 350 375 mV

11. The ADJ and GI pins have an internal clamp that limits the internal node to less than 3V. This limits the switch current should those pins get

Threshold Voltage

SENSE

Measured into ISM pin and V

V

= 1.25V

ADJ

ISM

= VIN

11 20 µA

±0.25 ±2 %

ZXLD1374

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Electrical Characteristics (cont.) (V

Symbol Parameter Conditions Min Typ Max Units

Output Parameters

V

FLAGL

I

FLAGOFF

V

STATUS

R

STATUS

Low Side Switch Output (LX pins tied together)

I

LX-LG

R

DS(ON)

t

PDHL

t

PDLH

t

LXR

t

LXF

t

STALL

LED Thermal control circuit (TADJ) parameters

V

TADJH

V

TADJL

I

TADJ

Notes: 12. Flag is asserted if V

13. In the event of more than one fault/warning condition occurring, the higher priority condition will take precedence. E.g. ‘Excessive coil current’ and ‘Out of regulation’ occurring together will produce an output of 0.9V on the STATUS pin. The voltage levels on the STATUS output assume the Internal regulator to be in regulation and V this is due to the feedback loop increasing the sense voltage.

14. With the device still in switching mode the LX pin has an over-voltage detection circuit connected to it with a resistance of approximately 1MΩ.

15. If t switched to its nominal operating voltage, before operation is allowed to resume. Restart cycles will be repeated automatically until the operating conditions are such that normal operation can be sustained. If t

ZXLD1374

Document number: DS35032 Rev. 3 - 2

FLAG Pin Low Level Output Voltage Output sinking 1mA 0.5 V

FLAG Pin Open-Drain Leakage Current

STATUS Flag No-Load Output Voltage (Note 13)

Output Impedance of STATUS Output Normal operation 10 k

Low Side Switch Leakage Current

LX Pin MOSFET on Resistance

Propagation Delay High-Low

Propagation Delay Low-High 131 ns

LX Output Rise Time 208 ns

LX Output Fall Time 12 ns

Time to assert ‘STALL’ flag and warning on STATUS output (Note 15)

Upper Threshold Voltage

Lower Threshold Voltage

TADJ Pin Input Current

<2.5V or V

exceeds t

ON

SHP

, LX turns off and then an initiate a restart cycle occurs. During this phase, ADJ is grounded internally and the SHP pin is

STALL

SHP

>3.5V

IN

= V

= 12V, @TA = +25°C, unless otherwise specified.)

AUX

V

FLAG

= 40V

1 µA

Normal operation 4.2 4.5 4.8

Out of regulation (V (Note 12)

VIN under-voltage (V

Switch stalled (tON or t

LX over-voltage state (VLX > 60V)

Over-temperature (TJ > 125°C)

Excess sense resistor current

SENSE

> 0.375V)

(V

Excessive switch current (ISW>1.5A)

Output stage off, V (Note 14)

ILX = 1.5A (tON < 100µs)

out of range)

SHP

< 5.6V)

IN

> 100µs)

OFF

= 60V

LX

3.3 3.6 3.9

2.4 2.7 3.0

1.5 1.8 2.1

0.6 0.9 1.2

60 µA

0.5 0.8

86 ns

V

= 225mV ± 30%, CL = 680pF,

SENSE

R

= 120Ω

L

LX low or high 100 170 µs

Onset of output current reduction (V falling)

Output current reduced to <10% of set value (V

falling)

TADJ

V

= 1.25V

TADJ

<=V

ADJ

. A reduction of the voltage on the STATUS pin will occur when the voltage on VIN is near –

REF

exceeds t

OFF

, the switch will remain off until normal operation is possible.

STALL

TADJ

560 625 690 mV

380 440 500 mV

1 µA

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RENT

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Typical Characteristics

3

2.5

1500

1250

900

750

SWITCHING FREQUENCY (kHz)

2

ENTt (mA)

1.5

1

PPL S

0.5

0

6 1218 24 303642 485460

SUPPLY VOLTAGE (V)

Figure 1 Supply Current vs. Supply Voltage

700

1400

650

600

1200

550

500

1000

450

400

I

LED

800

350

300

Switc hing Frequency

600

250

LED CURRENT (mA)

200

T = 25°C

150

100

50

0

0 0.5 1 1.5 2 2.5

ADJ VOLTAGE

A

V = V = 24V

AUX IN

8LEDs

µ

L = 33 H GI = 0.23 R = 300m

S

400

200

Ω

0

Figure 3 Buck-Boost LED Current, Switching Frequency vs. V

1500

ADJ

SWITCHING FREQUENCY (kHz)

1000

I

LED

750

Switching

500

LED CURRENT (mA)

250

0

Frequency

T = 25°C

A

V = V = 12V

AUX IN

2LEDs

µ

L = 33 H

Ω

R = 300m

S

0

0.5 ADJ VOLTAGE (V)

1

1.5

2

Figure 2 Buck LED Current, Switching Frequency vs. V

700 650

600

550

500

450

(mA)

400

I

LED

350

300

Switching Frequency

250

LED

200

150

100

50

0

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5

ADJ VOLTAGE

T = 25°C

A

V = V = 12V

AUX IN

12 LEDs

µ

L = 33 H

Ω

R = 300m

S

Figure 4 Boost LED Current, Switching Frequency vs. V

2.5

600

450

300

150

0

ADJ

700

600

500

400

300

200

100

ADJ

SWIT

HING F

E UEN

Y(kHz)

0

1250

1000

750

500

LED CURRENT (mA)

250

0

0 102030405060708090100

PWM DUTY CYCLE (%)

Figure 5 I vs. PWM Duty Cycle

LED

Figure 6 I

vs. Time - PWM Pin Transient Response

LED

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R

REFERENC

OLTAG

P

O

R

TCH ON-R

TANC

UTY

Typical Characteristics (cont.)

100%

80%

60%

DIMMI

40%

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ZXLD1374

1.252

1.2515

1.251

E (V)

1.2505

1.25

E V

1.2495

20%

1.249

LED

0%

0 250 500 750 1000 1250

T PIN VOLTAGE (mV)

ADJ

Figure 7 LED Current vs. T Voltage

ADJ

0.9

0.8

Ω

E ( )

0.7

0.6

ESIS

0.5

1.2485

1.248

-40 -25 -10 5 20 35 50 65 80 95 110 125 JUNCTION TEMPERATURE (°C)

Figure 8 V vs. Temperature

REF

100%

T = 25C

90%

80%

A

L = 33µH R = 150m

S

Buck Mode 2 LEDS

70%

60%

°

Ω

50%

0.4

D

40%

0.3

SWI

0.2

WE

0.1

0

-40 -25 -10 5

V = 12V I = 1.3A

LX

20 35 50 65 80 95 110 125

JUNCTION TEMPERATURE (°C)

Figure 9 R vs. Temperature

DS(ON)

IN

30%

20%

10%

0%

6 121824303642485460

INPUT VOLTAGE (V)

Figure 10 Duty Cycle vs. Input Voltage

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Typical Characteristics – Buck Mode – R

1.65

T = 25°C

A

V = V

AUX IN

1.60

1.55

(A)

L = 33µH R = 146m

S

Ω

1.50

1.45

L

1 LED

3 LEDs 5 LEDs

1.40

= 146m, L = 35µH, I

S

9 LEDs

= 1.5A

LED

11 L ED s

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13 LEDs

7 LEDs

ZXLD1374

15 LEDs

1.35 61218243036424854

INPUT VOLTAGE (V)

Figure 11 Load Current vs. Input Voltage and Number of LED

1200

T = 25°C

A

V = V

AUX IN

1000

z)

L = 33µ H R = 146m

S

Ω

(k

800

600

ING F

400

SWI

200

1 LED

0

6 12182430 3642485460

3 LEDs

5 LEDs

7 LEDs

INPUT VOLTAGE (V)

11 L E Ds9 LEDs

13 LEDs

15 LEDs

Figure 12 Frequency vs. Input Voltage and Number of LED

100%

15 LEDs

95%

5 LEDs

90%

60

IEN

EFFI

85%

80%

75%

3 LEDs

1 LED

11 L EDs9 LEDs7 LEDs

13 LEDs

70%

T = 25°C

A

V = V

65%

60%

6

12 18 24 30 36 42 48 54 60

AUX IN

L = 33µ H R = 146m

S

Ω

Input Voltage (V)

Figure 13 Efficiency vs. Input Voltage and Number of LED

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Typical Characteristics – Buck Mode – R

0.825

0.800

T = 25°C

A

V = V

AUX IN

L = 33µ H R = 291m

S

Ω

= 291m, L = 35µH, I

S

= 750mA

LED

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ZXLD1374

0.775

1 LED

3 LEDs

5 LEDs

7 LEDs 11 LEDs

9 LEDs

13 LEDs

15 LEDs

0.750

LED CURRENT (A)

0.725

0.700

0.675 6 12182430 3642 4854 60

INPUT VOLTAGE (V)

1000

900

800

700

600

500

T = 25°C

A

V = V

AUX IN

L = 33µ H R = 291m

S

Figure 14 I vs. Input Voltage and Number of LED

Ω

3 LEDs

5 LEDs

LED

7 LEDs

9 LEDs

11 L EDs

13 LEDs

15 LEDs

400

FREQUENCY (kHz)

300

1 LED

200

100

100%

0

6

12 18 24 30 36 42 48

Figure 15 Frequency ZXLD1374 - Buck Mode = L = 47 H

5 LEDs

7 LEDs

INPUT VOLTAGE (V)

9 LEDs

11 L ED s

μ

13 LEDs

54

15 LEDs

60

95%

90%

3 LEDs

85%

1 LED

I

E

80%

75%

70%

T = 25°C

A

V = V

65%

60%

6

AUX IN

L = 33µ H R = 291m

S

12

Ω

18

24

30 36

42

48 54 60

INPUT VOLTAGE (V)

Figure 16 Efficiency vs. Input Voltage and Number of LED

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Typical Characteristics – Boost Mode – R

0.358

0.347

0.336

(A)

0.325

0.314

L

= 150m, L = 33µH, I

S

= 325mA, GI

LED

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= 0.21

RATIO

°

T = 25C

A

L = 33µ H

Ω

R = 150m

S

R = 33k

Ω

GI1

R = 120k

GI2

Ω

ZXLD1374

0.303

6 LEDs

0.292 12 17 22 27 32

8 LEDs

10 LEDs

INPUT VOLTAGE (V)

Figure 17 I vs. Input and Number of LED

LED

700

650

600

z)

550

(k

500

450

400

F

350

300

250

200

6 LEDs

8 LEDs

12 17 22

10 LEDs

27 32 37 42 47

INPUT VOLTAGE (V)

Figure 18 Frequency vs. Input Voltage and Number LED

100%

12 LEDs

14 LEDs

16 LEDs

37 42 47

T = 25C

°

A

L = 33µ H R = 150m

Ω

S

R = 33k

Ω

GI1

R = 120k

GI2

14 LEDs

Ω

16 LEDs

16 LEDs14 LEDs12 LEDs10 LEDs8 LEDs6 LEDs

95%

90%

IE

85%

EFFI

T = 25C

°

A

L = 33µH

80%

75%

12 17 22 27 32 37 42 47

R = 150m

S

R = 33k

GI1

R = 120k

GI2

Ω

INPUT VOLTAGE (V)

Figure 19 Efficiency vs. Input Voltage and Number of LED

ZXLD1374

Document number: DS35032 Rev. 3 - 2

12 of 39

www.diodes.com

September 2012