MLX10803KDC-AAA-000-RE - Melexis - Datasheet.Directory

IC specification

MLX10803

High power LED driver

3901010803 Page 1/25

Data Sheet

Rev026 Jun/2012

Features

General

 Low cost power LED driver for external n-channel MOSFET

switching transistor

 6V to 32V DC input range

 Applications from mA to several Ampere LED current

 Possible temperature dependent regulation using external

Negative Temperature Coefficient (NTC) resistor

 Small package allows compact module design with

minimised wire runs and short connections to achieve

improved EMC performance

 Built-in randomiser for improved EMC performance

 High temperature operation capable

 Load dump protected to 80V

LED driver

 High energy efficiency

 PWM dimming via VS/PWM pin

 Light output has minimised dependency on supply and

temperature variations

 LED regulation parameters set with external resistors

1

2

3

4

8

7

6

5

VREF

IREF2

IREF1

DRVGATE

RSENSE

ROSC

GND

10803

(SOIC8)

VS/PWM

Ordering Code

Product Code Temperature Code Package Code Option Code Packing Form Code

MLX10803 K DC AAA-000 RE

Legend:

Temperature Code: K for temperature -40°c to 125°c

Package Code: DC for SOIC150Mil

Packing Form: RE for reel

Ordering example: MLX10803KDC-AAA-000-RE

General Description

The MLX10803 is a multi-purpose LED driver for high power LEDs designed for high current and high voltage

applications. The circuit is designed for demanding automotive applications and therefore suitable in all other high

intensity LED applications.

Numerous adjustment possibilities allow for the design of different LED applications using only a few external

components.

The circuit is load dump protected for 80V load dump pulse.

IC specification

MLX10803

High power LED driver

3901010803 Page 2/25

Data Sheet

Rev026 Jun/2012

Table of contents

Features ........................................................................................................... 1

General Description ......................................................................................... 1

Table of contents ............................................................................................. 2

Block diagram .................................................................................................. 3

1.

Typical application data ............................................................................ 4

1.1.

LED driver applications ...................................................................... 4

1.1.1.

Principle complete schematic LED driver diagram ..................... 4

1.1.2.

Principle soft start up LED driver diagram .................................. 5

1.1.3.

LED driver application notes ....................................................... 5

2.

Application pins ......................................................................................... 7

3.

Absolute maximum ratings ........................................................................ 7

4.

Electrical characteristics ........................................................................... 8

5.

ESD/EMI recommendations for MLX10803 ............................................ 11

6.

Automotive test pulses ............................................................................ 12

6.1.

Test pulse definition ......................................................................... 13

7.

LED driving principle ............................................................................... 16

7.1.

General ............................................................................................ 16

7.2.

The principle in detail ....................................................................... 17

7.3.

Switching frequency considerations and constant light output ......... 20

8.

Temperature regulation ........................................................................... 21

9.

Mechanical Data ..................................................................................... 22

9.1.

Mechanical data of the MLX10803 package .................................... 22

10.

Standard information regarding manufacturability of Melexis products with different

soldering processes ....................................................................................... 23

11.

History record ...................................................................................... 24

12.

Disclaimer ........................................................................................... 25

IC specification

MLX10803

High power LED driver

3901010803 Page 3/25

Data Sheet

Rev026 Jun/2012

Block diagram

VS/PWM

IREF2

IREF1

DRVGATE

RSENSE

Debouncing

300

ns

OFF

FF

ON

Monoflop with

pseudo random

generator

OFF Timer

4.2 µs (average value)

at f

OSC

= 2.5 MHz

ON Timer

23.4 µs (average value)

at f

OSC

= 2.5MHz

RC Oscillator

tunable: 0.5 MHz to 5 MHz

frequ. tolerance: ± 20 %

Start OFF

Reference Currents

Trim Logic

(incl. Zener Zaps)

...

I

ref_x

Clamping

max. 12 V

ROSC

GND

POR

Regulator VDD

5.0 V ± 10 %

Power on Reset

VDD

VREF

COMP

Minimal

voltage

selection

4V

divider

1/5

divider

1/10

COMP

Start ON

COMP

20mV

1.25V

IC specification

MLX10803

High power LED driver

3901010803 Page 4/25

Data Sheet

Rev026 Jun/2012

1. Typical application data

1.1. LED driver applications

1.1.1. Principle complete schematic LED driver diagram

ROSC

IREF2

VREF

GND

RSENSE

DRVGATE

VS/PWM

VBAT

GND

100nF

Cap for EMC directly

on the connector

100nF...1uF

NTC

VS/PWM

VREF_SET

IREF1

Cnoise

ROSC

IREF2

VREF

GND

RSENSE

DRVGATE

VS/PWM

Vsup

GND

IREF1

IC specification

MLX10803

High power LED driver

3901010803 Page 5/25

Data Sheet

Rev026 Jun/2012

1.1.2. Principle soft start up LED driver diagram

ROSC

IREF2

VREF

GND

RSENSE

DRVGATE

VS/PWM

VBAT

GND

100nF

Cap for EMC directly

on the connector

100nF...1uF

IREF1

Figure 1:

1.1.3. LED driver application notes

The MLX10803 is optimised for the use of low cost coils and n-channel MOSFETs. For a standard application with

1 LED and an average current of 350mA, a coil of about 100µH…220µH and ≤ 1Ω DC resistance should be

chosen. The sense resistor should have a value between 0.27Ω…0.47Ω / 250mW.

As a general rule: for higher load current lower inductance of the coil is needed because higher currents lengthen

the charging time of the coil. Thus, switching frequencies may become lower than 20kHz which is often not desired.

It is possible to set the peak current and the average current of the LED by variation of the RSENSE resistor, the

coil value and the internal oscillator frequency (ROCS resistor).

The flyback diode that carries the load current during the passive state (driver OFF) should be a fast switching and

low intrinsic capacitance diode like ES1D or BYG80 in order to avoid parasitic spikes on RSENSE. The diode must

be able to carry the LED current flowing during the OFF time of the driver.

The n-channel MOSFET should have low intrinsic capacitances, a drain-source voltage suitable for the application

and must be able to carry the current flowing through the LED(s) during the ON time. To decrease the time of

transistor switching and to improve the thermal behaviour of the module, the lines between transistor and IC should

be minimised.

For applications that use an NTC resistor for temperature sensing, the NTC value has to be selected according to

the application requirements. For most applications, a NTC value up to 470kΩ will be suitable.

In case of longer lines between the IC and the coil (which should be avoided because of EMI), a capacitor might be

placed in parallel to RSENSE to avoid crosstalk and parasitic switching. Well chosen parameters for external

components can help to avoid such conditions. The goal should be to unload the coil as much as possible during

the selected off time (see also chapter 7).

IC specification

MLX10803

High power LED driver

3901010803 Page 6/25

Data Sheet

Rev026 Jun/2012

To reduce an influence of noise which can be coupled to sensitive reference pins IREF1, IREF2 it is possible to

connect noise-filtering capacitors in parallel to IREF1 and IREF2 resistors (see Figure 1, Cnoise capacitors). The

coupling also should be reduced as much as possible by proper routing of IREF1 and IREF2 stripes on PCB.

IREF2 resistor should be placed as close as possible to IREF2 pin and stripe from IREF1 pin to NTC resistor

should be shielded by GND stripe.

The schematic diagram under Figure 1 is used in applications where the LED is controlled by external control

electronics. A PWM with a frequency between 30Hz..5kHz can be applied to the VS/PWM pin in order to

dim the light output. This frequency is limited by the time needed for recharging the coil and monoflop time selected

by the resistor connected to ROSC as well as by the IC settling time after POR. This function can be used to

achieve different light outputs or also be used in a temperature down regulation.

It is recommended to have the PWM frequency at least 5-10 times lower than the selected driver switching

frequency.

Diode is placed between DRVGATE and VS/PWM IC pins serves as discharger of gate of FET transistor. Thus,

having switched off IC at VS/PWM voltage=0 DRVGATE turns to Z-state. Charge that was stored in gate capacitor

runs down to VS/PWM module pin via the diode.

The minimum schematic diagram under Figure 2 is sufficient for all applications with a constant light output.

We also recommend to compare with our other circuits in the MLX108xx family and study these application notes

for suitable solutions.

IC specification

MLX10803

High power LED driver

3901010803 Page 7/25

Data Sheet

Rev026 Jun/2012

2. Application pins

Nr.

Name Function

1 VREF Analogue input, setting of LED peak current

2 ROSC External resistor sets internal Oscillator frequency. Sets the average discharge time of the coil

3 IREF1 External NTC resistor for temperature down regulation

4 IREF2 External resistor sets the temperature breakpoint when the NTC resistor starts down regulation

5 RSENSE External sense resistor pin for peak current detection

6 GND Ground

7 DRVGATE Pin driving the gate of the switching transistor

8 VS/PWM Supply Voltage / PWM signal

3. Absolute maximum ratings

Parameter

Symbol

Condition

Min

Max

Unit

Power supply (VS/PWM) vs DC

max. 2h

-0.3

32

36

V

Power supply, non operational function

max. 0.5s (Load dump)

vsmax

max 0.5s

36

80

V

Input current in protection circuitry on any pin iprot In case of

maximum

supply ratings

-10 10 mA

Input voltage on RSENSE pin virsense normal

operation

-0.3 11

Input voltage on IREF1, IREF2, VREF pins vrefmax without external

resistor

protected by

external 47k

resistor

-0.3

-80

(0.5s)

40

80

(0.5s)

V

Input voltage on ROSC pin vroscmax normal

operation

-0.3 Vdd+0.3 V

Input voltage on DRVGATE pin vdrvgatmax idrvgatemax

current must

not be

exceeded

-0.3 22 V

Input/output current on DRVGATE pin idrgatemax pulse mode 500 mA

Junction temperature

Lifetime

Dynamic

Storage temperature

Tjunc

normal

operation.

max. 100h

-40

-55

140

150

°C

Ambient temperature range Tambient normal

operation

-40 125 °C

Thermal resistance junction to ambient rth SOIC8 128.4 K/W

IC specification

MLX10803

High power LED driver

3901010803 Page 8/25

Data Sheet

Rev026 Jun/2012

4. Electrical characteristics

Following characteristics are valid

- for the full temperature range of Tambient = -40°C to +125°C,

- a supply range of 32V ≥ vs > 6V

unless other conditions noted.

With 6V ≥ vs > vporh analogue parameters can not be guaranteed.

Note: The correct operation of the MLX10803 as a switching mode power supply for voltages lower than the

nominal supply voltage is dependent on the forward bias voltage of the used LED.

The user must ensure that at low supply voltage the peak current threshold voltage on the RSENSE pin can

be reached in order to keep the switching principle working.

If several pins are charged with transients above VS/PWM and below GND, the sum of all substrate currents of the

influenced pins should not exceed 10mA for correct operation of the device.

Normal operating supply voltage is supposed to be 13.8V.

Parameter

Symbol

Conditions

Limits

Units

Min

Typ

Max

Global parameters

Maximum current during

80V load dump

ihv vs=80V

10 mA

Normal supply current at

highest DC voltage

inomdch vs=32V

2 mA

Normal supply current inom vs=13.8V

400 700 µA

IC settling time

IC settling time after

power on reset

tsettle 10 µs

Oscillator related parameters

The min/max specification influences inversely all derived timings

Min oscillator frequency foscmin For a selected

external resistor

Rosc of 440kΩ and

room temperature

0.4 0.5 0.6 MHz

Max oscillator frequency foscmax For a selected

external resistor

Rosc of 40kΩ and

room temperature

4.0 5.0 6.0 MHz

Extended min oscillator

frequency

foscext For a selected

external resistor

Rosc of 1200kΩ

and room

temperature

1

0.148 0.184 0.221 MHz

IC specification

MLX10803

High power LED driver

3901010803 Page 9/25

Data Sheet

Rev026 Jun/2012

RESET related parameters

Power on reset level, if

VS/PWM is ramped up

vporh Reset is connected

to the internal Vdd,

but vporh is

measured on pin

VS/PWM

1.5 4 V

Power on reset

hysteresis, if VS/PWM is

drawn down

vporhyst Reset is connected

to the internal Vdd,

but vporhyst is

measured on pin

VS/PWM

0.1 0.7 V

Vdd related parameters (Vdd

used

internal

ly only

)

Internal supply voltage

range

vdd vs=13.8V 4.5 5.5 V

RSENSE related parameters

Input leakage current ileakrsense vs=13.8V,

vrsense=0V, 5V

-20 20

µ

A

Debounce time after

switching on

tdeb vs=13.8 200 500 ns

VREF related parameters

Leakage current ileakvref vs=13.8V,

vvref=0V, 5V

-20 20

µ

A

DRVGATE cessation

voltage

vswoff

2

vs=13.8V 15 20 25 mV

Sensitive voltage range vvrefrng

2

vs=13.8V vswoff 3.8 V

Linear voltage range vvreflinrng

2

vs=13.8V 0.1 3.8 V

IREF1

related parameters

Output current for

external reference

measurement

iiref1 vs=13.8V,

viref1=viref1rng

46.5 50 52.5

µ

A

Temperature drift of the

current

iiref1drift -0.1 %/

°

C

Sensitive voltage range viref1rng

2

vs=13.8V vswoff 3.6 V

Linear voltage range viref1linrng

2

vs=13.8V 0.1 3.6 V

IREF2 related parameters

Difference of iiref2 to

iiref1

difiref12 vs=13.8V,

viref1=viref2rng

-10 +10 %

Temperature drift of the

current

iiref2drift -0.1 %/

°

C

Sensitive voltage range viref2rng

2

vs=13.8V vswoff 3.6 V

Linear voltage range viref2linrng

2

vs=13.8V 0.1 3.6 V

DRVGATE

related parameters

Max output voltage in ON

state

vmaxdrv Load current 1

µ

A

to GND, vs=13.8V

10 13 V

Output resistance of

push-pull output

Rdrvgateout To GND pin

To VS/PWM pin,

vs=13.8V

3.5

20

7.8

40

15

60

Ω

IC specification

MLX10803

High power LED driver

3901010803 Page 10/25

Data Sheet

Rev026 Jun/2012

ROSC related parameters

3

Output voltage vrosc vs=13.8V 1 1.5 V

Resistance on pin to GND

for 0.5MHz

Roscmin 440 k

Ω

Resistance on pin to GND

for 1MHz

Roscmid 220 k

Ω

Resistance on pin to GND

for 5MHz

Roscmax 40 k

Ω

Resistance on pin to GND

for extended min

oscillator frequency

foscext

Roscext 1200 k

Ω

Monoflop related parameters

Minimum OFF time due to

the implemented jitter

toffmin1mhz Oscillator is set to

1 MHz, in case the

oscillator is put to

an other

frequency,

toffmin1mhz

scales accordingly

9

µ

s

Maximum OFF time due

to the implemented jitter

toffmax1mhz Oscillator is set to

1 MHz, in case the

osc is put to an

other frequency,

toffmax1mhz

scales accordingly

16

µ

s

Average monoflop time

for ON state of transistor

ton1mhz Oscillator is set to

1 MHz

60.5 µs

1

Circuit operation with external resistor Rosc > 1200kΩ is not recommended

2

Guaranteed by design

3

Value for the resistor Rosc to be connected to ROSC pin is derived from the needed monoflop time Tmon

according to the following expression:

)02.0

5.12

][

(2.222][ −⋅=Ω sTmon

kRosc

µ

IC specification

MLX10803

High power LED driver

3901010803 Page 11/25

Data Sheet

Rev026 Jun/2012

5. ESD/EMI recommendations for MLX10803

• In order to minimise EMI, the PCB has to be designed according to EMI guidelines. Additional components

may be needed, other than what is shown in the application diagrams, in order to comply with

the EMI requirements.

• The MLX10803 is an ESD sensitive device and has to be handled according to EN100015 part 1.

• The MLX10803 will fulfil the requirements in the application according to the specification and to DIN 40839

part 1.

• The MLX10803 is designed with ESD protection >1000V HBM according to MIL883D.

IC specification

MLX10803

High power LED driver

3901010803 Page 12/25

Data Sheet

Rev026 Jun/2012

6. Automotive test pulses

The following chapter is valid for a completely assembled module. That means that automotive test pulses are

applied to the module and not to the single IC.

In the recommended application according to chapter 1.1, the reverse polarity diode together with the capacitors

on the supply and the load dump protected IC itself protect the module against the automotive test pulses listed

below.

The exact values of the capacitors for the application have to be figured out according to the automotive and

EMI requirements.

No damage occurs for any of the test pulses. A deviation of the IC’s characteristics is allowed during pulse 1, 2, 4;

the module returns to normal operation after the pulse without any additional action.

During test pulse 3a, 3b, 5 the module operates within characteristic limits.

Parameter

Symbol

Min

Max

Dim

Test condition,

Functional status

Transient test pulses in accordance to ISO7

637

part 1

& 3. Pin VREF goes outside of module via

resistor of 47kΩ

ΩΩ

Ω. Module schematic is according to application notes mentioned in 1.1.1.

Test pulse #1 at module pins VBAT,

VS/PWM. VREF_SET, IC pin IREF1 ->

GND

vpulse1 -100 V 5000 pulses,

functional state C

Test pulse #2 at module pins VBAT,

VS/PWM. VREF_SET, IC pin IREF1 ->

GND

vpulse2 100 V 5000 pulses

functional state C

Test pulse #3a at module pins VBAT,

VS/PWM. VREF_SET, IC pin IREF1 ->

GND

vpulse3a -150 V 1h,

functional state A

Test pulse #3b at module pins VBAT,

VS/PWM. VREF_SET, IC pin IREF1 ->

GND

vpulse3b 100 V 1h,

functional state A

Test pulse #4 at module pin VBAT,

VS/PWM, VREF_SET -> GND

vspulse4

vapulse4

-6

-5

-4

-2.5

V

1 pulse,

functional state C

Test pulse #5 at IC pin VS/PWM -> GND vpulse5 45 85 V functional state C

Description of functional status:

A: All functions of the module are performed as designed during and after the disturbance.

B: All functions of the module are performed as designed during and after the disturbance:

However, one or more can deviate from specified tolerance. All functions return automatically

to normal limits after exposure is removed. Memory functions shall remain class A.

C: A function of the module is not performed as designed during disturbance but returns automatically to

a normal operation after the disturbance.

IC specification

MLX10803

High power LED driver

3901010803 Page 13/25

Data Sheet

Rev026 Jun/2012

6.1. Test pulse definition

Test Pulse 1

Ri = 10 Ω

vpulse1

10%

90%

1µs

2ms

200ms

<100µs

0.5s…5s

12V

V

t

Test Pulse 2

Ri=10 Ω

200ms

1µs

50µs

0.5…5s

10%

90%

vpulse2

12V

V

t

IC specification

MLX10803

High power LED driver

3901010803 Page 14/25

Data Sheet

Rev026 Jun/2012

Test Pulse 3a

Ri = 50 Ω

12V

vpulse3a

100µs

10ms 90ms

10%

90%

5ns

100ns

t

V

Test Pulse 3b

Ri = 50 Ω

12V

vpulse3b

100µs

10ms 90ms

90%

10%

5ns

100ns

t

V

IC specification

MLX10803

High power LED driver

3901010803 Page 15/25

Data Sheet

Rev026 Jun/2012

Test Pulse 4 (Cranking)

Ri = 0.01Ω

12V

vapulse4

vspulse4

5ms 0.5-20s

V

t

15ms 50

ms

100 ms

Test Pulse 5 (Load Dump)

Ri = 0.5…4Ω

90%

10%

Pulse 5

80V

td = 40...400ms

tr = 0.1...10ms

12V

V

t

vpulse5

IC specification

MLX10803

High power LED driver

3901010803 Page 16/25

Data Sheet

Rev026 Jun/2012

7. LED driving principle

7.1. General

The LED is driven by a switched mode power supply using an inductor as the energy storage element. This method

has several advantages. The supply voltage has to be set down to the forward bias voltage of the LED. In ordinary

applications this is achieved by a resistor with the following drawbacks:

- A resistor dissipates power which is transformed to heat

- Efficiency is reduced drastically

- The light output of the LED is dependent on the supply and the temperature of the resistor

The MLX10803 avoids these disadvantages as shown by the following calculation with L=220µH, R

SENSE

= 0.1 Ω:

Supposed:

V

bat

= 13.8V

V

fLED

≈ 3.4V example 1; 8V example2;

I

fLED

≈ 4A

V

f1

≈ 0.9V (reverse polarity diode)

V

f2

≈ 0.9V (free wheel diode)

V

RSENSE

≈ 0.4V (@I

fLED

, R

SENSE

=0.1 Ω)

V

RDS ON

≈ 0.04V (@I

fLED

)

V

Coil

≈ 0.2V (@I

fLED

)

Efficiency using a simple resistor or load dump regulation:

Efficiency n:

%29≈=

BAT

fLED

V

n

example1;

%58≈

example2;

Efficiency using the MLX10803:

The following calculation is an approximation only, due to the fact that coil current is not constant. It is therefore

calculated with average currents.

1) During OFF time, the coil acts as the storage element and delivers its energy to the flyback diode

and the LED:

%75

2

1

≈

++

=

CoilffLED

fLED

VVV

V

n

example1;

%88≈

example 2;

2) During ON time, current flows through the reverse polarity diode, LED, coil , FET driver and RSENSE,

which causes the following voltage drops:

%69

1

2

≈

++++

=

RSENSERDSonCoilffLED

fLED

VVVVV

V

n

example1;

%84≈

example 2

;

3) ON and OFF times are in ratio of roughly 30:70 for example 1 and 65:35 for example 2:

Efficiency n:

%733.07.0

21

≈⋅+⋅= nnn

example1;

%87≈

example2;

IC specification

MLX10803

High power LED driver

3901010803 Page 17/25

Data Sheet

Rev026 Jun/2012

7.2. The principle in detail

After powering on the MLX10803 the switch becomes open and the current through the LED starts to rise. The rate

of current raise is limited by the value of the coil. When the current through the LED reaches half of a maximum

value, the ON timer is started, and if during 58.5 clocks of the internal oscillator the maximum current value through

the LED is not reached, the driver switches off. This maximum current is adjusted by the resistors on the IREF2,

IREF1 or voltage applied to VREF pins (voltage on these pins is divided by 5). The minimum of these voltages is

taken as a reference. The driver is switched off for a monoflop time, which is equal to 9…16 pulses of oscillator.

The frequency of the oscillator can be set by the customer using the Rosc value using such formula:

)44.4][/(2.222][ +Ω= kRoscMHzFosc

.

Both parameters, the peak current threshold voltage and the monoflop time, create an ON/OFF period to form an

average current through the LED. By adjusting these parameters, an adjustment of the average load current is

possible in a wide range.

I

t

Iavg2

Iavg1

Imax2

Imax1

I

t

Iavg1

Iavg2

Imax

T1

T2

Note: The current sense comparator has a typical debouncing time of 300ns as shown in the block diagram. This

delay time prevents the driver from being switched off due to short term switching oscillations. When working with

very short monoflop times, this time has to be taken into account for calculations.

I

t

Imax

Iavg

tmon_off

By applying a PWM signal on VS/PWM, the LED can be dimmed from 0% to 100%.

VS/PWM = L LED permanent OFF

VS/PWM = PWM LED dimmed with PWM between 0% to 100%

VS/PWM = H LED permanent ON

IC specification

MLX10803

High power LED driver

3901010803 Page 18/25

Data Sheet

Rev026 Jun/2012

Dimming is achieved by applying a PWM directly to the module supply or by changing the reference voltage on pin

VREF or the resistor’s value on IREF2 pin.

IC settling times must always be considered in PWM mode. Please refer also to chapter 1.1.3 for

additional PWM frequency considerations.

Limitation of the ON time prevents from exceeding the allowed average current when the power supply voltage is

not sufficient for the current to reach its peak value and restricts in this case duty cycle of switching to 68%.

I

t

Imax

Iavg

tmon_offtmon_on

Imax/2

A pseudo random generator is applied to the monoflop time. The pseudo random generator runs with the clock

derived out of the monoflop time and adds a random distribution on these 3 LSBs. Therefore, the monoflop time

gets a random variation from its value. The EMI behaviour of the complete module is improved due to the variation

of the otherwise fixed switching frequency.

I

t

Imax

Iavg

tmon tmon'

tmon'

The inductance L of a coil describes the amount of magnetic energy that can be stored in it.

Consequently, high inductive coils will be discharged less than low inductive coils in a given time.

Generally the coil can be driven in two different ways:

1) The coil is discharged partially only. That means the coil still carries a significant amount of energy

when going from discharging to charging. In that moment the charging current rises immediately to

the coil current that was flowing just before switching. This is connected with large dI/dt transients on the

RSENSE pin that have a negative impact on EMI. This is mostly preferred way of regulation because of low

influence of supply voltage and coil value on output current. Fast flyback diode is recommended and extra

important in this case.

2) The coil discharged completely. Thus, at the end of a discharging cycle, the coil doesn’t carry energy

anymore. With the next charging cycle, current increases steadily from around zero. This way, large dI/dt

transients are completely avoided.

IC specification

MLX10803

High power LED driver

3901010803 Page 19/25

Data Sheet

Rev026 Jun/2012

Because of randomisation, the discharging time is not constant but varies within a certain range. It must be

ensured that only the longest possible monoflop time completely discharges the coil. Otherwise the coil is

discharged before the monoflop time ends which results in a loss of accuracy.

Conclusion: In most cases the coil is driven in a combination of both ways. A trade off has to be made between

EMI behaviour and maximum allowed LED current. By varying these parameters, an optimum can

be found for every application.

Below are some examples for typical parameter sets given for a 4A LED current and the following application data:

• RSENSE = 0.1 Ω/ 2 watt

• ROSC = 270kΩ

• L = 47µH, 4A minimum, 0.05 Ω

• Normal nFET switch transistor, rds on < 0,01 Ω

Remarks:

• 4A and 0.05 Ω results in 0.8 watt power dissipation over the coil.

• 4A and 0.1 Ω for the RSENSE resistor results in 1.6 watt, but only for 50% of the time in average.

• The LED(s) with this current will dissipate 32 watt if they have 8V forward voltage.

I

t

Imax1

Iavg

Toff

Coil 1

Imax2

Coil 2

Resistance 2

Resistance 1

Coil 1 > Coil 2

Resistance 1 > Resistance 2

IC specification

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High power LED driver

3901010803 Page 20/25

Data Sheet

Rev026 Jun/2012

7.3. Switching frequency considerations and constant light output

As already shown, the switching frequency depends on the peak current as well as on the monoflop time for a

given coil. Furthermore it depends on the coil inductance itself.

Due to the principle of switch mode power supplies, the current through the LED is kept constant for any

supply change. The parameter that changes in order to keep the current constant is the switching

frequency itself. The lower the supply voltage, the lower the switching frequency. Furthermore, the supply

current is affected by supply changes: with an increasing supply voltage the average supply current decreases.

The graph below shows the normalised luminous flux versus the power supply for a standard application with one

white Luxeon III LED driven at 750mA. The parameters are optimised for the 24V board net.

The luminous flux at 24V has been set to 100%. The graph indicates that the light output is minimally dependent on

supply changes over the whole range from 16 to 32V.

MLX10803

Normalized luminous flux Θv/Θv

(24V)

vs. supply voltage

Θv/Θv

(24V)

=f(V

BAT

)

80.00

85.00

90.00

95.00

100.00

105.00

110.00

115.00

120.00

16 18 20 22 24 26 28 30 32

V

BAT

[V]

Θv/Θv

(24V)

[%]

Iled=750mA, fsw=70kHz (@24V)

IC specification

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High power LED driver

3901010803 Page 21/25

Data Sheet

Rev026 Jun/2012

8. Temperature regulation

In normal mode the peak current threshold voltage is defined by the lowest voltage on pins VREF, IREF2 and

IREF1. Usually the resistor connected to IREF2 pin has a small thermal coefficient and the resistor on IREF1 pin

has a big negative temperature coefficient (but they also can be connected vice versa). Both of these pins have an

output current of 50 µA. When the voltage on pin IREF1 falls below the voltage on pin IREF2 or VREF, the voltage

reference for the actual maximum current is taken from pin IREF1. This makes the value of the peak current

sensitive to temperature and prevents overheating of LED or IC. When the voltage on pin IREF1 becomes higher

than voltage on IREF2 or VREF, the reference switches back to IREF2 or VREF pin.

The thermal behaviour of the system should be characterised during the design-in of the product by the user.

For a system that is designed for thermal conditions, temperature down regulation may not be needed. In this case,

It is enough to leave the IREF1 or IREF2 pin unconnected and the internal current source will pull it up to the

voltage Vdd – 0.7V.

System behaviour can be configured to compensate the dependency of LED light output versus temperature. The

example of such compensation is depicted below.

Illustration of a possible temperature regulation

Constant light

Saved energy

40% of the light at 25°C

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120-20

Junction Temperature, TJ(°C)

20

40

80

100

Light output from Amber LED with constant current supply

Compensation current funtion

Thermal protection function

Resulting thermal compensated and protected light output from an Amber LED

60

IC specification

MLX10803

High power LED driver

3901010803 Page 22/25

Data Sheet

Rev026 Jun/2012

9. Mechanical Data

9.1. Mechanical data of the MLX10803 package

Package of the MLX10803: SOIC8 in accordance to the JEDEC standard.

DIMENSIONS

Note

INCHES MILLIMETERS

MIN. NOM. MAX

A .061 .064 .068 1.55 1.63 1.73

A1 .004 .006 .0098 0.127 0.15 0.25

A0 .055 .058 .061 1.40 1.47 1.55

B .0138 .016 .0192 0.35 0.41 0.49

C .0075 .008 .0098 0.19 0.20 0.25

D .189 .194 .196 4.80 4.93 4.98

E .150 .155 .157 3.81 3.94 3.99

e .050 1.27

H .230 .236 .244 5.84 5.99 6.20

h .010 .013 .016 0.25 0.33 0.41

L .016 .025 .035 0.41 0.64 0.89

oc 0

°

5

°

8

°

0

°

5

°

8

°

Degrees

X .085 .093 .100 2.16 2.36 2.54

H

123

8

E/2

D/2

TOP VIEW BOTTOM VIEW

D

e h

Ao

A

SEATING PLANE E

A

1

Angle 45

C

SEE DETAIL A

oc L

SIDEVIEW END VIEW

DETAIL A

IC specification

MLX10803

High power LED driver

3901010803 Page 23/25

Data Sheet

Rev026 Jun/2012

10. Standard information regarding manufacturability of Melexis products

with different soldering processes

Our products are classified and qualified regarding soldering technology, solderability and moisture sensitivity level

according to following test methods:

Reflow Soldering SMD’s (Surface Mount Devices)

• IPC/JEDEC J-STD-020

Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices

(classification reflow profiles according to table 5-2)

• EIA/JEDEC JESD22-A113

Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing

(reflow profiles according to table 2)

Wave Soldering SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)

• EN60749-20

Resistance of plastic- encapsulated SMD’s to combined effect of moisture and soldering heat

• EIA/JEDEC JESD22-B106 and EN60749-15

Resistance to soldering temperature for through-hole mounted devices

Iron Soldering THD’s (Through Hole Devices)

• EN60749-15

Resistance to soldering temperature for through-hole mounted devices

Solderability SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)

• EIA/JEDEC JESD22-B102 and EN60749-21

Solderability

For all soldering technologies deviating from above mentioned standard conditions (regarding peak temperature,

temperature gradient, temperature profile etc) additional classification and qualification tests have to be agreed

upon with Melexis.

The application of Wave Soldering for SMD’s is allowed only after consulting Melexis regarding assurance of

adhesive strength between device and board.

Melexis is contributing to global environmental conservation by promoting lead free solutions. For more information

on qualifications of RoHS compliant products (RoHS = European directive on the Restriction Of the use of certain

Hazardous Substances) please visit the quality page on our website: http://www.melexis.com/quality.aspx

IC specification

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High power LED driver

3901010803 Page 24/25

Data Sheet

Rev026 Jun/2012

11. History record

Rev. No. Change Date

1 1 Creation with MLX10801 specifications as base 25.07.04

2 1 Gone through document VAR,ALX,RAH,LIW 02.08.04

3 1 4-th pin recast from TEST to VREF - linear dimming 07.08.04

4 1 Revision of kick off meeting

5 1 Revision before release RAH

6 1 Improved packing information RAH

7 1 Improved block diagram 7.10.04

8 1 Design implementation review 15.01.05

9 1 Updated schematic diagrams 16.01.05

10 1 Pin order changed 3.02.05

11 1 Temperature code changed to “K”, Vmaxdrv changed, Oscillator related parameters

changed, VREF related parameters changed, ROSC related parameters changed

13.06.05

12 1 Cosmetic changes 17.06.05

13 1 Cosmetic changes 21.06.05

14 1 VREF related parameters are changed 12.07.05

15 1 Pins’ names changed: RE_REF  VREF, NTC  IREF1, SETNTC  IREF2, VS 

VS/PWM. Corresponding parameters’ names changed. RSENSE related parameters

changed

3.08.05

16 1 LED driver applications changed 18.08.05

17 1 Block diagram changed, Electrical characteristics: Global parameters, Monoflop

related parameters, RSENSE related parameters, IREF1 related parameters, IREF2

related parameters, VREF related parameters changed, LED driving principle: The

principle in detail changed

21.09.05

2 Internal review 23.09.05

18 1 Chapter 7.3. changed: graph added, cosmetic changes 23.09.05

2 Cosmetic changes 28.09.05

3 Soldering information is changed 31.10.05

19 1 Internal review 28.11.05

20 1 Monoflop related parameters changed, IREF1, IREF2, VREF related parameters

changed

6.01.06

21 1 Figure1, Figure2 changed, 4. Electrical characteristics: changed, 8. Temperature

regulation: figure added

23.03.06

22 1 “TBD” removed, cosmetic changes 6.04.06

2 RESET related parameters changed, ROSC related parameters changed 6.04.06

3 Cosmetic changes 14.04.06

4 Chapter 8, Illustration of a possible temperature regulation changed 16.08.06

5 Cosmetic changes 17.08.06

23 1 Chapter 4 (parameters table ) changed 25.09.06

24 1 Iref1 related parameters changed, Iref2 related parameters changed, DRVGATE

related parameters changed, Absolute maximum ratings changed

7.12.06

25 1 Oscillator related parameters, ROSC related parameters changed 2.10.07

26 1 Disclaimer, logo, information regarding solderability 11.06.12

IC specification

MLX10803

High power LED driver

3901010803 Page 25/25

Data Sheet

Rev026 Jun/2012

12. Disclaimer

Devices sold by Melexis are covered by the warranty and patent indemnification provisions

appearing in its Term of Sale. Melexis makes no warranty, express, statutory, implied, or by

description regarding the information set forth herein or regarding the freedom of the described

devices from patent infringement. Melexis reserves the right to change specifications and prices

at any time and without notice. Therefore, prior to designing this product into a system, it is

necessary to check with Melexis for current information. This product is intended for use in

normal commercial applications. Applications requiring extended temperature range, unusual

environmental requirements, or high reliability applications, such as military, medical life-support

or life-sustaining equipment are specifically not recommended without additional processing by

Melexis for each application.

The information furnished by Melexis is believed to be correct and accurate. However, Melexis

shall not be liable to recipient or any third party for any damages, including but not limited to

personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect,

special incidental or consequential damages, of any kind, in connection with or arising out of the

furnishing, performance or use of the technical data herein. No obligation or liability to recipient

or any third party shall arise or flow out of Melexis’ rendering of technical or other services.

For the latest version of this document, go to our website at

www.melexis.com

Or for additional information contact Melexis Direct:

Europe, Africa, Asia: America:

Phone: +32 1367 0495 Phone: +1 248 306 5400

E-mail: sales_europe@melexis.com E-mail: sales_usa@melexis.com

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