Analog Devices EVAL-LT8356-1-AZ Guida rapida alla configurazione

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

DESCRIPTION

LT8356-1

100VIN/120VOUT LED

Controller with SSFM

Evaluation board EVAL-LT8356-1-AZ is a high voltage

LED controller featuring the LT

8356-1. It is assembled

as a buck-boost mode LED driver but can be altered to a

boost LED driver by adjusting the FB network and LED-

connection. EVAL-LT8356-1-AZ drives a single string of

LEDs up to 36V at 1A when the input is between 8V and

36V. It has an undervoltage lockout (UVLO) set at 6.5V

falling and 7.5V rising. The evaluation board features

PWM dimming, analog dimming, shutdown, open LED

and short LED fault protection and reporting.

EVAL-LT8356-1-AZ runs at 250kHz switching frequency

and features spread spectrum frequency modula-

tion(SSFM) modulating its switching frequency from

250kHz to 310kHz to reduce EMI emissions. Small ceramic

input and output capacitors are used to save space and

cost. A high voltage 100V external power switch and 100V

catch diode are used for up to 36W buck-boost mode

output as assembled. The open LED overvoltage protec-

tion (OVP) uses the IC’s constant voltage regulation loop

to limit the LED+ to LED–voltage to approximately 41V if

the LED string is opened. The VOUT, if referenced to GND,

will jump to VIN + 41V if the LED string is opened.

The input and output filters on EVAL-LT8356-1-AZ help

further reduce its EMI. These filters consist of a small

ferrite bead or inductor and high frequency ceramic

capacitors. A small resistor on the gate pin of the power

MOSFET is used to reduce high frequency EMI. These

filters, combined with proper board layout and SSFM, are

very effective in reducing EMI to comply with CISPR25

class 5 limits. Please follow the recommended layout and

the four-layer PCB thickness of EVAL-LT8356-1-AZ. For

best efficiency and PWM dimming performance, the EMI

filters can be removed. All registered trademarks and trademarks are the property of their respective owners.

The LT8356-1’s integrated PWMTG high-side PMOS

driver assists with PWM dimming of the connected LEDs.

The LED string can be PWM-dimmed for accurate bright-

ness control with an externally generated PWM signal

for highest achievable dimming ratio. It can also utilize

LT8356-1’s internally generated PWM feature for up to

128:1 exponential dimming. When running PWM dim-

ming, the SSFM aligns itself with the PWM signal for

flicker-free operation of the LED string. This applies to

both internal and external PWM dimming. The LT8356-1

uses CTRL and IADJ pins for two-pin analog dimming.

The input undervoltage lockout (UVLO), LED current,

output overvoltage protection (OVP), and switching

frequency, can all be easy adjusted with simple resis-

tor changes to EVAL-LT8356-1-AZ. Modifications can be

made to convert the board from buck-boost mode LED

driver to boost and buck mode LED Driver, and maintain

low EMI, PWM dimming and fault diagnostic features.

Buck mode and boost LED Driver schematics are pro-

vided in the data sheet. Please consult the data sheet

or the applications team regarding how to customize

EVAL-LT8356-1-AZ.

The LT8356-1 data sheet gives a complete description

of the part, operation, and applications information. The

data sheet must be read in conjunction with this demo

manual for evaluation board EVAL-LT8356-1-AZ. The

LT8356IUDCM-1 is assembled in a 20-lead side sol-

derable plastic QFN package with a thermally enhanced

exposed ground pad. Proper board layout is essential

for maximum performance. See the data sheet section

“Designing the Printed Circuit Board”.

Design files for this circuit board are available.

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

PERFORMANCE SUMMARY

Specifications are at TA= 25°C

PARAMETER CONDITION MIN TYP MAX UNITS

Input Voltage PVIN Range Operating 8 36 V

Switching Frequency (fSW, SSFM ON) R6 = 110k 250 310 kHz

ILED RS2 = 0.25Ω, 8V < PVIN < 36V, VLED ≤ 36V,

CTRL and ADJ Turrets = Float

1 A

Open LED Protection (LED+ to LED–) R8 = 10k, R20 = 10k, R22 = 340k 41 V

Peak Efficiency (SSFM ON) PVIN = 12V, VLED = 36V, ILED = 1A with Filters

PVIN = 12V, VLED = 36V, ILED = 1A without Filters

91.5

Peak Switch Current Limit RS1 = 0.01Ω 10 A

Internally-Generated PWM Dimming Range 0.5V < VPWM < 1.5V 1/128 100 %

Internally-Generated PWM Dimming Frequency R6 = 110k 260 Hz

PVIN Undervoltage Lockout (UVLO) falling R4 = 499k, R5 = 127k 6.5 V

PVIN Enable Turn-On (EN) rising R4 = 499k, R5 = 127k 7.5 V

BOARD PHOTO

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

QUICK START PROCEDURE

Evaluation board EVAL-LT8356-1-AZ is easy to set up

to evaluate the performance of the LT8356-1. Follow the

procedure below:

1. With power off, connect a string of LEDs that will run

with forward voltage less than or equal to 36V(at 1A)

to the LED+ and LED– (buck-boost) turrets on the PCB

as shown in Figure1.

2. With power off, connect the input power supply to the

PVIN and GND turrets. Make sure that the DC input

voltage will not exceed 36V.

3. Turn the input power supply on and make sure the

voltage is between 8V and 36V for proper operation

at max LED current.

4. Observe the LED string running at the programmed

LED current.

5. To change the brightness with analog dimming, the

CTRL and IADJ pins are used. The product of the offset

CTRL and IADJ pin voltages set the current when the

two voltages vary between 0.5V and 1.5V. Please refer

to data sheet for more details.

6. To changethe brightnesswith externalPWM dimming,

attach a rectangular waveform with varying duty cycle

to the PWM turret. The ON and OFF voltages should

be above 1.6V and below 0.4V, respectively.

7. To change the brightness with internally generated

PWM dimming, adjust the voltage at the PWM pin

between 0.5V and 1.5V to vary the duty ratio of the

internal PWM generator.

Figure1. Setup Drawing for EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver

(*See Boost LED Driver Setup Section for More Information on Boost-Only Topology)

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

BOOST LED DRIVER SETUP

EVAL-LT8356-1-AZ is assembled as a buck-boost mode

LED Driver, but with minor adjustments can be reconfig-

ured as a boost LED driver. In buck-boost mode, the LED

connection is at VIN, and a level shifter is used for the FB

network. In a boost LED Driver, the LED- connection is

at GND and a resistor divider is used for the FB network.

To configure EVAL-LT8356-1-AZ as a boost LED driver,

remove R20, R22, Q3, FB2, C12 and C11. Install 0Ω for

R14 and 1M for R9. Consult the data sheet for OVP cal-

culations and details about the FB pin. Connect the LED

string from LED+ to LED–(GND boost) as seen inFigure2.

Note that when EVAL-LT8356-1-AZ is reconfigured

as a boost LED Driver, other components may need

to be adjusted depending on their voltage rating and

powercapabilities.

Figure2. EVAL-LT8356-1-AZ as a Boost LED Driver

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

TEST RESULTS

Figure3. EVAL-LT8356-1-AZ as Buck-Boost Mode LED

Driver Efficiency vs Input Voltage

Figure4. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver

Internal 260Hz 2% PWM Dimming with EMI Filters and

SSFMON: 12VIN, 36VLED, 1A

Efficiency vs VIN

= 250kHz

SSFM = ON

LED

= 1A

LED

= 36V

WITH EMI FILTERS

WITHOUT EMI FILTERS

INPUT VOLTAGE (V)

100

EFFICIENCY (%)

EVAL-83561 F03

Internal PWM Dimming

20µs/DIV

50A/DIV

PWMTG

50V/DIV

5A/DIV

LED

1A/DIV

EVAL-83561 F04

2µs/DIV

LED

1A/DIV

EVAL-83561 F05

500:1

1,000:1

2,000:1

5,000:1

External PWM Dimming

Figure5. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver

External 150Hz PWM Dimming with EMI Filters and SSFM ON:

12VIN, 36VLED, 1A

Figure6. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver:

50% to 100% to 50% Load Step Transient Response, 12VIN

Transient Response

= 250kHz

SSFM = ON

500µs/DIV

ILED

500mA/DIV

CTRL

500mV/DIV

EVAL-83561 F06

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

Figure7. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver Board

Thermal Image with Filters and SSFM ON: 12VIN, 36VLED, 1A

TEST RESULTS

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

Figure8. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver Conducted Emissions (Voltage Method): 12VIN, 36VLED, 1A (SSFM ON)

Figure9. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver Conducted Emissions (Current Method): 12VIN, 36VLED, 1A (SSFM ON)

Figure10. EVAL-LT8356-1-AZ as Buck-Boost Mode LED Driver Radiated Emissions: 12VIN, 36VLED, 1A (SSFM ON)

(a) CISPR25 Peak Conducted EMI – Voltage Method (b) CISPR25 Average Conducted EMI – Voltage Method

(a) CISPR25 Peak Conducted EMI – Current Method (b) CISPR25 Average Conducted EMI – Current Method

(a) CISPR25 Peak Radiated EMI (b) CISPR25 Average Radiated EMI

TEST RESULTS

CLASS 5 PEAK LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

108

–20

–10

PEAK CE (dBµV)

EVAL-83561 F08a

CLASS 5 AVERAGE LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

108

–20

–10

AVERAGE CE (dBµV)

EVAL-83561 F08b

CLASS 5 PEAK LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

108

–60

–50

–40

–30

–20

–10

PEAK CE (dBµA)

EVAL-83561 F09a

CLASS 5 AVERAGE LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

108

–60

–50

–40

–30

–20

–10

AVERAGE CE (dBµA)

EVAL-83561 F09b

CLASS 5 PEAK LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

100

1000

–20

–10

PEAK RE (dBµV/m)

EVAL-83561 F10a

CLASS 5 AVERAGE LIMIT

EVAL-LT8356-1-AZ

EVAL-LT8356-1-AZ + SHIELD

AMBIENT

FREQUENCY (MHz)

0.1

100

1000

–20

–10

AVERAGE RE (dBµV/m)

EVAL-83561 F10b

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

EMISSIONS SHIELD (OPTION)

For the lowest emissions, an EMI shield can be attached to

EVAL-LT8356-1-AZ. The PCB was fabricated with place-

holders for six shield clips that can hold a 44mm×44mm

metal shield. Part number for an example shield can

be found in the Parts List section in the Optional EMI

Figure11. EVAL-LT8356-1-AZ Top Silkscreen Outlining Placement of Shield Clips and EMI Shield on PCB

Filter Components section. The Top silkscreen picture,

Figure11, shows the placeholders for the six surface

mount shield clips. Emissions can be tested with and

without the removable clip-shield.

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

PARTS LIST

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 1 C7 CAP., 10μF, X7S, 50V, 10%, 1210, AEC-Q200, NO SUBS ALLOWED MURATA, GCM32EC71H106KA03L

2 1 C5 CAP., 68μF, ALUM ELECT, 50V, 20%, 6.3mm × 7.7mm, SMD,

RADIAL, AEC-Q200

PANASONIC, EEEFN1H680XP

3 1 C6 CAP., 4.7μF, X5R, 10V, 10%, 0603, AEC-Q200 TAIYO YUDEN, LMK107BJ475KAHT

4 1 C8 CAP., 1μF, X7R, 50V, 10%, 0805, AEC-Q200 MURATA, GCM21BR71H105KA03L

5 1 C9 CAP., 1000pF, X7R, 50V, 10%, 0402, AEC-Q200 MURATA, GCM155R71H102KA37D

6 1 C12 CAP., 10μF, X7S, 50V, 10%, 1210, AEC-Q200 MURATA, GCM32EC71H106KA03L

7 1 C13 CAP., 4.7μF, X7S, 100V, 10%, 1210, AEC-Q200 MURATA, GCM32DC72A475KE02L

8 1 C16 CAP., 2.2μF, X6S, 10V, 10%, 0402, AEC-Q200 MURATA, GRT155C81A225KE13D

9 1 C19 CAP., 2.2μF, X5R, 25V, 10%, 0603, AEC-Q200 TAIYO YUDEN, TMK107BBJ225KAHT

10 1 D1 DIODE, SCHOTTKY, 100V, 3A, POWERDI5, AEC-Q101 DIODES INC., PDS3100Q-13

11 1 L2 IND., 15μH, PWR, SHIELDED, 20%, 13.8A, 18.6mΩ,

11.8mm × 10.5mm, XAL1010, AEC-Q200

COILCRAFT, XAL1010-153MEB

12 1 M1 XSTR., MOSFET, N-CH, 100V, 37A, PowerPAK SO-8L, AEC-Q101 VISHAY, SQJA72EP-T1_GE3

13 1 M2 XSTR., MOSFET, P-CH, 100V, 33.6A, PowerPAK SO-8L, AEC-Q101 VISHAY, SQJ211ELP-T1_GE3

14 1 Q3 XSTR., PNP, 100V, 1A, SOT-23-3, AEC-Q101 DIODES INC., FMMT593QTA

15 4 R1, R2, R12, R25 RES., 100k, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402100KJNED

16 1 R4 RES., 499k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402499KFKED

17 1 R5 RES., 127k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402127KFKED

18 1 R6 RES., 110k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603110KFKEA

19 1 R7 RES., 16k, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040216K0JNED

20 2 R8, R20 RES., 10k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210K0FKED

21 1 R19 RES., 10Ω, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210R0JNED

22 1 R22 RES., 340k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402340KFKED

23 1 RS1 RES., 0.01Ω, 1%, 1.5A, 1206, LONG-SIDE TERM., METAL,

SENSE, AEC-Q200

SUSUMU, KRL3216E-C-R010-F-T1

24 1 RS2 RES., 0.25Ω, 1%, 1/2W, 1206, SENSE, AEC-Q200 YAGEO, PT1206FR-7W0R25L

25 1 U1 IC, LED DRIVER CTRLR, QFN-20 ANALOG DEVICES, LT8356IUDCM-1#WPBF

Optional EMI Filter Components

26 1 C3 CAP., 10μF, X7S, 50V, 10%, 1210, AEC-Q200,

NO SUBS ALLOWED

MURATA, GCM32EC71H106KA03L

27 1 C11 CAP., 0.1μF, X7R, 50V, 10%, 0603, AEC-Q200 TDK, CGA3E2X7R1H104K080AA

28 1 C18 CAP., 0.1μF, X7S, 100V, 10%, 0603, AEC-Q200 TDK, CGA3E3X7S2A104K080AB

29 2 FB1, FB2 IND., 330Ω AT 100MHz, FERRITE BEAD, 25%,

1.8A, 80mΩ, 0805, 1LN

TAIYO YUDEN, FBMH2012HM331-T

30 1 L1 IND., 4.7μH, PWR, SHIELDED, 20%, 11A, 14.4mΩ,

6.76mm × 6.56mm, XAL6060, AEC-Q200

COILCRAFT, XAL6060-472MEB

31 1 R10 RES., 10Ω, 5%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060310R0JNEA

32 0 FB3-FB5 IND., OPTION, FERRITE BEAD, 1210

33 0 C1 CAP., OPTION, 0402

DEMO MANUAL EVAL-LT8356-1-AZ

Rev. A

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

34 0 C2 CAP., OPTION, 1206

35 0 C4 CAP., OPTION, 1210

36 0 C10, C17 CAP., OPTION, 0603

37 0 CL1-CL6 OPTION, WE-SHC CABINET CLIP 6.5mm × 0.8mm × 1.27mm WURTH, 369 000 00

38 0 SH1 OPTION, WE-SHC CABINET SHIELD 44.37mm × 44.37mm WURTH, 369 074 06S

Optional Electrical Components

39 0 C1, C23-C25 CAP., OPTION, 0402

40 0 C4, C14, C20-C22 CAP., OPTION, 1210

41 0 C15 CAP., OPTION, ALUM. ELECT., SMD

42 0 D2, D3 DIODE, OPTION, SOD-323F

43 0 R3, R11, R13, R14, R18,

R21, R23, R24, R26

RES., OPTION, 0402

44 0 R9 RES., OPTION, 0603

Hardware: For Demo Board Only

45 7 E1-E7 TEST POINT, TURRET, 0.094" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2501-2-00-80-00-00-07-0

46 4 E8-E11 TEST POINT, TURRET, 0.064" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2308-2-00-80-00-00-07-0

47 2 J1, J2 CONN., BANANA JACK, FEMALE, THT, NON-INSULATED,

SWAGE, 0.218

KEYSTONE, 575-4

48 4 MH1-MH4 STANDOFF, NYLON, SNAP-ON, 0.50" KEYSTONE, 8833

PARTS LIST

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