Analog Devices EVAL-LT8355-1-AZ User manual

1
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
DESCRIPTION
LT8355-1
60VIN/120VOUT Dual LED
Controller with SSFM
All registered trademarks and trademarks are the property of their respective owners.
Evaluation board EVAL-LT8355-1-AZ is a high voltage
dual LED controller featuring the LT
®
8355-1. Channel 1
is assembled as a boost LED driver and channel 2 as a
buck-boost mode LED driver. Either channel can be altered
to a boost LED driver or buck-boost mode LED driver
by adjusting the FB network and LED connection. EVAL-
LT8355-1-AZ drives a single string of LEDs per channel
when the input is between 8V and 18V. Channel 1 drives
up to 72V of LEDs at 450mA and channel 2 drives up to
30V of LEDs at 1A. EVAL-LT8355-1-AZ has an undervolt-
age lockout (UVLO) set at 6.2V falling and 7.5V rising.
EVAL-LT8355-1-AZ features PWM dimming, analog dim-
ming, shutdown, open LED and short LED fault protection
and reporting.
EVAL-LT8355-1-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 on each channel for up to 32W boost
output for channel 1 and up to 30W buck-boost mode
output for channel 2 as assembled. The open LED over-
voltage protection (OVP) uses the IC’s constant voltage
regulation loop to limit the LED+ to LED–voltage if the
LED string is opened to approximately 81V for channel 1
and 36V for channel 2.
The input and output filters on EVAL-LT8355-1-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-LT8355-1-AZ. For
best efficiency and PWM dimming performance, the EMI
filters can be removed.
The LT8355-1’s integrated PWMTG high-side PMOS driv-
ers assist with PWM dimming of the connected LEDs. The
LED strings can be PWM-dimmed for accurate brightness
control with externally generated PWM signals for highest
achievable dimming ratios. They can also utilize LT8355-
1’s internally generated PWM feature for up to 128:1
exponential dimming. When running PWM dimming, the
SSFM aligns itself with the PWM signal for flicker-free
operation of each channel’s LED string. This applies to
both internal and external PWM dimming. The LT8355-1
uses CTRL1 analog dimming for channel 1, and CTRL2
and IADJ2 pins for two-pin analog dimming for channel 2.
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-LT8355-1-AZ. Modifications can
be made to convert the channels to boost, buck-boost
mode and buck mode LED drivers, and maintain low EMI,
PWM dimming and fault diagnostic features. Buck mode,
buck-boost mode and boost LED driver schematics are
provided in the data sheet. Please consult the data sheet
or the applications team regarding how to customize
EVAL-LT8355-1-AZ.
The LT8355-1 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-LT8355-1-AZ. The
LT8355IUFDM-1 is assembled in a 28-lead side solderable
plastic QFN package with a thermally enhanced exposed
ground pad and is AEC-Q100 qualified for automotive
applications. Proper board layout is essential for maxi-
mum performance. See the data sheet section “Designing
the Printed Circuit Board”.
Design files for this circuit board are available.

2
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
BOARD PHOTO
Figure1. EVAL-LT8355-1-AZ Demo Board
PARAMETER CONDITION MIN TYP MAX UNITS
Input Voltage PVIN Range Operating 8 18 V
Switching Frequency (fSW, 100% to 125% SSFM) R40 = 86.6k 250 312 kHz
ILED 8V < PVIN < 18V, CTRL1, CTRL2, ADJ2 Turrets = Float
CH1: RS2 = 0.56Ω, VLED ≤ 72V
CH2: RS4 = 0.25Ω, VLED ≤ 30V
450
1
mA
A
Open LED Protection (LED+ to LED–) CH1: R14 = 0, R11 = 1M, R10 = 15k
CH2: R52 = 287k, R53 = 10k, R47 = 10k
81
36
V
V
Peak Efficiency (SSFM ON) PVIN =12V, CH1:VLED = 72V, ILED = 450mA, CH2:VLED = 30V, ILED = 1A
with Filters
without Filters
90
91
%
%
Peak Switch Current Limit CH1: RS1 = 0.013Ω
CH2: RS3 = 0.012Ω
7.7
8.3
A
A
Internally-Generated PWM Dimming Range 0.5V < VPWM < 1.5V 1/128 100 %
Internally-Generated PWM Dimming Frequency R40 = 86.6k 250 Hz
PVIN Undervoltage Lockout (UVLO) Falling R33 = 499k, R34 = 127k 6.2 V
PVIN Enable Turn-On (EN) Rising 7.5 V
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
eval-lt8355-1-az F01

3
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
QUICK START PROCEDURE
Evaluation board EVAL-LT8355-1-AZ is easy to set up
to evaluate the performance of the LT8355-1. Follow the
procedure below.
1. With power off, connect a string of LEDs that will
run with forward voltage less than or equal to 72V
(at 450mA) to the LED1+ and LED1– (boost) turrets
and another string of LEDs that will run with forward
voltage less than or equal to 30V(at 1A) to the LED2+
and LED2– (buck-boost) turrets as shown in Figure2.
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 18V.
3. Turn the input power supply on and make sure the
voltage is between 8V and 18V for proper operation
at max LED current.
4. Observe the LED strings running at the programmed
LED current.
5. To change the brightness with analog dimming, the
CTRL1 pin is used for channel 1 and CTRL2 and IADJ2
pins are used for channel 2. The product of the offset
CTRL and IADJ pin voltages sets 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 respective PWM turret for channel 1 and chan-
nel2. 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 respec-
tivePWM pin for channel 1 and channel 2 between
0.5Vand 1.5V to vary the duty ratio of the internal
PWMgenerator.

4
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
eval-lt8355-1-az F02
Figure2. Setup Drawing for EVAL-LT8355-1-AZ: Channel 1 as Boost LED Driver, and Channel 2 as Buck-Boost Mode LED Driver (See
Boost LED Driver Setup Section for More Information on Boost Topology)
QUICK START PROCEDURE

5
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
Full-scale LED current sense threshold voltage
(V
ISP
toV
ISN
) for LT8355-1 is 250mV, which sets full-
scale LED current according to Equation 1.
ILED =
250mV
R
SENSE
(1)
The LED current sense threshold voltage can be trimmed
to be lower than 250mV when analog dimming is desired.
This includes but is not limited to, when a single sense
resistor is used for multiple designs with different current
levels needed for each design, and when low current level
is required at start-up and increases at steady state, etc.
For configurations where the LED current sense threshold
(VISP to VISN) is configured for 75mV or lower via CTRL
or IADJ pin, an additional resistor connecting VREF to FB
is needed to allow for proper start-up of the LT8355-1
(see Figure3). Refer to data sheet for more information.
See Equation 2 and Equation 3 to set resistor values for
boost and buck-boost mode topologies.
START-UP WITH LOW VISP TO VISN
VOUT
eval-lt8355-1-az F03
VREF VOUT VREF VIN
FB
FB
R1 R2 40k
10k
10k
10k
R1
Q
(a) Boost (a) Buck-Boost
Figure3. Proper Star-Up Configuration
Boost: Calculate R1 and R2 to set desired VOUT_OVP volt-
age and VFB to 400mV at VIN_MIN.
VIN_MIN =400mV +40µA –
1.6V
R1 R2
VOUT_OVP =1.2V+120µA
–
800mV
R1 R2
(2)
Buck-Boost: Calculate R1 to set VLED_OVP (VOUT – VIN) to
desired OVPvoltage.
VLED_OVP BE =V+120µA •
R1
(3)
EVAL-LT8355-1-AZ has channel 1 assembled as a boost
LED driver and channel 2 as a buck-boost mode LED
driver. With minor adjustments channel 2 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.
BOOST LED DRIVER SETUP
To configure EVAL-LT8355-1-AZ channel 2 as a boost
LED driver, remove R53, R52, Q2, FB10, C38 and C49.
Install 0Ω for R46 and 1M for R48. Consult the data sheet
for OVP calculations and details about the FB pin. Connect
the LED string from LED+ to LED– (GND boost).
Note that when EVAL-LT8355-1-AZ is reconfigured
as a boost LED driver, other components may need
to be adjusted depending on their voltage rating and
powercapabilities.

6
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
TEST RESULTS
Figure4. EVAL-LT8355-1-AZ, Efficiency vs Input Voltage:
Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
Figure5. EVAL-LT8355-1-AZ, Internal 250Hz 10% PWM Dimming with
EMI Filters: 12VIN, Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
Figure6. EVAL-LT8355-1-AZ, External 150Hz PWM Dimming with EMI
Filters: 12VIN, Channel 1, 72VLED 450mA, Channel2, 30VLED 1A
f
SW
= 250kHz
100% TO 125% SSFM
BOTH CHANNELS ON
WITH FILTERS
WITHOUT FILTERS
INPUT VOLTAGE (V)
8
10
12
14
16
18
60
65
70
75
80
85
90
95
100
EFFICIENCY (%)
eval-lt8355-1-az F04
2ms/DIV
V
SW1
50V/DIV
V
SW2
50V/DIV
I
LED1
1A/DIV
I
LED2
1A/DIV
eval-lt8355-1-az F05
ILED1 5k:1
ILED1 2k:1
ILED1 1k:1
ILED1 500:1
ILED2 5k:1
ILED2 2k:1
ILED2 1k:1
ILED2 500:1
2µs/DIV
I
LED1
500mA/DIV
I
LED2
1A/DIV
eval-lt8355-1-az F06

7
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
Figure7. EVAL-LT8355-1-AZ: 50% to 100% to 50%
Load Step Transient Response, 12VIN
f
SW
= 250kHz
100% TO 125% SSFM
200µs/DIV
V
CTRL1,2
5V/DIV
I
LED1
500mA/DIV
I
LED2
500mA/DIV
eval-lt8355-1-az F07
eval-lt8355-1-az F08
Figure8. EVAL-LT8355-1-AZ, Thermal Image with EMI Filters:
12VIN, Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
TEST RESULTS

8
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
TEST RESULTS
Figure9. Conducted Emissions (Voltage Method): 12VIN, Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
Figure10. Conducted Emissions (Current Method): 12VIN, Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
Figure11. Radiated Emissions: 12VIN, Channel 1, 72VLED 450mA, Channel 2, 30VLED 1A
(a) CISPR25 Peak (b) CISPR25 Average
(a) CISPR25 Peak (b) CISPR25 Average
(a) CISPR25 Peak (b) CISPR25 Average
CLASS 5 PEAK LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
108
–20
–10
0
10
20
30
40
50
60
70
80
PEAK CE (dBµV)
eval-lt8355-1-az F09a
CLASS 5 AVERAGE LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
108
–20
–10
0
10
20
30
40
50
60
70
80
AVERAGE CE (dBµV)
eval-lt8355-1-az F09b
CLASS 5 PEAK LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
108
–60
–50
–40
–30
–20
–10
0
10
20
30
40
50
60
PEAK CE (dBµA)
eval-lt8355-1-az F10a
CLASS 5 AVERAGE LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
108
–60
–50
–40
–30
–20
–10
0
10
20
30
40
50
60
AVERAGE CE (dBµA)
eval-lt8355-1-az F10b
CLASS 5 PEAK LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
100
1000
–20
–10
0
10
20
30
40
50
60
PEAK RE (dBµV/m)
eval-lt8355-1-az F11a
CLASS 5 AVERAGE LIMIT
EVAL-LT8355-1-AZ
EVAL-LT8355-1-AZ WITH SHIELD
AMBIENT
FREQUENCY (MHz)
0.1
1
10
100
1000
–20
–10
0
10
20
30
40
50
60
AVERAGE RE (dBµV/m)
eval-lt8355-1-az F11b

9
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
For the lowest emissions, an EMI shield can be attached
to EVAL-LT8355-1-AZ. The PCB was fabricated with
placeholders for six shield clips that can hold a 61.5mm ×
61.5mm metal shield. Part number for an example shield
can be found in the Parts List section in the Optional EMI
EMISSIONS SHIELD (OPTION)
Figure12. EVAL-LT8355-1-AZ Top Silkscreen Outlining Placement of Shield Clips and EMI Shield on PCB
Filter Components section. The top silkscreen (Figure12)
shows the placeholders for the six-surface mount shield
clips. Emissions can be tested with and without the
removable clip shield.
eval-lt8355-1-az F12

10
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C3, C29 CAP., 100μF, ALUM ELECT, 25V, 20%, 6.3mm × 7.7mm,
D8, SMD, RADIAL, EEEHA, AEC-Q200
PANASONIC, EEEHAE101XAP
2 1 C7 CAP., 1μF, X7R, 25V, 10%, 0805, AEC-Q200 TDK, CGA4J3X7R1E105K125AB
3 1 C8 CAP., 1000pF, X7R, 50V, 10%, 0402, AEC-Q200 MURATA, GCM155R71H102KA37D
4 4 C9-C11, C36 CAP., 4.7μF, X7S, 100V, 10%, 1210, AEC-Q200 MURATA, GCM32DC72A475KE02L
5 2 C14, C42 CAP., 2.2μF, X5R, 25V, 10%, 0603, AEC-Q200 TAIYO YUDEN, TMK107BBJ225KAHT
6 4 C22, C23, C31, C32 CAP., 4.7μF, X7R, 25V, 10%, 1210, AEC-Q200 TAIYO YUDEN, TMF325B7475KMHP
7 1 C33 CAP., 2.2μF, X5R, 10V, 10%, 0603, AEC-Q200 TAIYO YUDEN, LMK107BJ225KAHT
8 1 C34 CAP., 680pF, X7R, 50V, 10%, 0402, AEC-Q200 TDK, CGA2B2X7R1H681K050BA
9 1 C35 CAP., 4.7μF, X5R, 10V, 10%, 0603, AEC-Q200 TAIYO YUDEN, LMK107BJ475KAHT
10 1 C38 CAP., 10μF, X7S, 50V, 10%, 1210, AEC-Q200,
NO SUBS ALLOWED
MURATA, GCM32EC71H106KA03L
11 2 D1, D4 DIODE, SCHOTTKY, 100V, 3A, POWERDI5, AEC-Q101 DIODES INC., PDS3100Q-13
12 1 L2 IND., 15μH, PWR, SHIELDED, 20%, 7.7A, 50.29mΩ,
4040DD, IHLE-5A, AEC-Q200
VISHAY, IHLE4040DDER150M5A
13 1 L4 IND., 10μH, PWR, SHIELDED, 20%, 8.5A, 33.06mΩ,
4040DD, IHLE-5A SERIES, AEC-Q200
VISHAY, IHLE4040DDER100M5A
14 2 M1, M9 XSTR., MOSFET, N-CH, 100V, 37A, POWERPAK
SO-8L,AEC-Q101
VISHAY, SQJA72EP-T1_GE3
15 2 M4, M10 XSTR., MOSFET, P-CH, 100V, 33.6A, POWERPAK
SO-8L,AEC-Q101
VISHAY, SQJ211ELP-T1_GE3
16 1 Q2 XSTR., PNP, 100V, 1A, SOT-23-3, AEC-Q101 DIODES INC., FMMT593QTA
17 3 R1, R35, R36 RES., 100k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402100KFKED
18 4 R5, R13, R39, R43 RES., 100k, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402100KJNED
19 1 R8 RES., 39k, 1%, 1/16W, 0402, AEC-Q200 YAGEO, AC0402FR-0739KL
20 2 R9, R49 RES., 10Ω, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210R0JNED
21 1 R10 RES., 15k, 1%, 1/16W, 0402, AEC-Q200 YAGEO, AC0402FR-0715KL
22 1 R11 RES., 1M, 1%, 1/10W, 0603 VISHAY, CRCW06031M00FKEA
23 1 R14 RES., 0Ω, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2GE0R00X
24 1 R33 RES., 499k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW0603499KFKEA
25 1 R34 RES., 127k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402127KFKED
26 1 R40 RES., 86.6k, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060386K6FKEA
27 1 R42 RES., 30k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040230K0FKED
28 1 R47 RES., 10k, 1%, 1/10W, 0402, AEC-Q200 PANASONIC, ERJ2RKF1002X
29 1 R52 RES., 287k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW0402287KFKED
30 1 R53 RES., 10k, 5%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210K0JNED
31 1 RS1 RES., 0.013Ω, 1%, 1W, 1206, LONG-SIDE TERM,
SENSE,AEC-Q200
ROHM, LTR18EZPFSR013
32 1 RS2 RES., 0.56Ω, 1%, 1/2W, 1206, SENSE, AEC-Q200 PANASONIC, ERJ8BQFR56V
33 1 RS3 RES., 0.012Ω, 1%, 1.5W, 1206, LONG-SIDE TERM,
METAL, SENSE, AEC-Q200
KOA SPEER, WU732B15TTD12L0F
34 1 RS4 RES., 0.25Ω, 1%, 1/2W, 1206, SENSE, AEC-Q200 YAGEO, PT1206FR-7W0R25L
35 1 U1 IC, DUAL LED CONTROLLER, QFN-28, AEC-Q100 ANALOG DEVICES, LT8355IUFDM-1#WPBF

11
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Optional EMI Filter Components
36 0 C1, C27 CAP., OPTION, 0402
37 0 C2, C28 CAP., OPTION, 1206
38 4 C5, C6, C30, C45 CAP., 10μF, X7R, 25V, 10%, 1210, AEC-Q200 TDK, CGA6P1X7R1E106K250AC
39 2 C15, C43 CAP., 0.1μF, X7S, 100V, 10%, 0603, AEC-Q200 TDK, CGA3E3X7S2A104K080AB
40 0 C19-C21, C47, C48 CAP., OPTION, 0603
41 1 C49 CAP., 0.1μF, X7R, 50V, 10%, 0603, AEC-Q200 TDK, CGA3E2X7R1H104K080AA
42 3 FB4, FB9, FB10 IND., 330Ω AT 100MHz, FERRITE BEAD, 25%, 1.8A,
80mΩ, 0805, 1LN
TAIYO YUDEN, FBMH2012HM331-T
43 0 FB5 IND., FERRITE BEAD, OPT, 0805
44 2 L1, L3 IND., 8.2μH, PWR, SHIELDED, 20%, 8A, 26.4mΩ,
6.56mm × 6.36mm, XAL6060, AEC-Q200
COILCRAFT, XAL6060-822MEC
45 2 R7, R41 RES., 10Ω, 5%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW060310R0JNEA
46 0 CL1-CL6 OPTION, WE-SHC CABINET CLIP
6.5mm × 0.8mm × 1.27mm
WURTH, 369 000 00
47 0 SH1 OPTION, WE-SHC SHIELDIY 61.5mm × 61.5mm WURTH, 360002
Optional Electrical Components
48 0 C17, C18, C25, C41,
C46, C50, C51
CAP., OPTION, 0402
49 0 C12, C13, C16, C37,
C39, C40, C44
CAP., OPTION, 1210
50 0 C24 CAP., OPTION, ALUM. ELECT., SMD
51 0 D2, D3, D5, D6 DIODE, OPTION, SOD-323F
52 0 FB1-FB3, FB6-FB8 IND., OPTION, FERRITE BEAD, 1210
53 0 Q1 XSTR., OPTION, PNP, SOT-23
54 0 R3, R6, R12, R19-
R22, R25, R32,
R37, R38, R44-R46,
R50, R51, R59
RES., OPTION, 0402
55 0 R48 RES., OPTION, 0603
Hardware: For Demo Board Only
56 10 E1-E4, E8-E13 TEST POINT, TURRET, 0.094" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2501-2-00-80-00-00-07-0
57 5 E14-E18 TEST POINT, TURRET, 0.064" MTG. HOLE, PCB 0.062" THK MILL-MAX, 2308-2-00-80-00-00-07-0
58 2 J1, J2 CONN., BANANA JACK, FEMALE, THT, NON-INSULATED,
SWAGE, 0.218"
KEYSTONE, 575-4
59 4 MP1-MP4 STANDOFF, NYLON, SNAP-ON, 0.50" KEYSTONE, 8833
PARTS LIST

12
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
SCHEMATIC DIAGRAM
2. ALL CAPACITORS 0603.
1. ALL RESISTORS 5%, 0402. NOTES: UNLESS OTHERWISE SPECIFIED.
8V - 18V 450mA
72VLED
GND
PVIN
V12 V11
Vo1
I12 I11
7.5EN 6.2UVLO
IF L1 IS REMOVED, TIE INPUT TO VIN PIN
PVIN
VREF
VIN1
INTVCC
VIN1
E8
LED1-
GND
BOOST
C10 4.7uF 1210 100V
TP3
D3
OPT
SOD-323F
M1 SQJA72EP
52
4
1
3
R25 OPT
R11 1M 0603 1%
TP24
VEXT1
D1
PDS3100Q
21 3
TP6
U1-2
LT8355IUFDM-1
CTRL1
6FB1 4
GATE1 28
FAULT1
7ISN1 2
ISP1 3
PWM1
10
PWMTG1 1
SENSEN1 26
SENSEP1 27
VC1 5
VIN
16
EN/UVLO
15
FB1 OPT
R12 OPT
C6
10uF 1210
25V
E2
LED1-
VIN1
BUCK-BOOST
R33
499k
1%
0603
FB2 OPT
C20 OPT
L1
8.2uH
XAL6060-822MEC
12
R6 OPT C17
OPT 0402
TP8
EN/UVLO
FB3 OPT
C1 OPT 0402
R1
100K
1%
R21 OPT
M4
SQJ211ELP
52
4
1 3
C18 OPT 0402
C22 4.7uF 25V 1210
R10
15k
1% R22
OPT
C12 OPT 1210
RS1 0.013
0612
C2 OPT 1206
C21 OPT
C16 OPT 1210
TP7
R34 127k
1%
TP1
C13 OPT 1210
E16
PWM1
R20 OPT
C11 4.7uF 1210 100V
C19 OPT
C8 1000pF
R5
100k
+
C24
OPT
R13
100k
J1 E12
PVIN
E13
GND
R8 39k
Q1 OPT
3 2
1
E1
LED1+
FB5 OPT
0805
+
C3 100uF 25V
EEEHAE101XAP
R3 OPT
TP11
VC1
J2
C14
2.2uF
C7
1uF
0805
25V
E14
CTRL1
R14
0
C23 1210 25V 4.7uF
C5
10uF 1210
25V
TP9
RS2
0.56
1206
R7
10
0603
C9 4.7uF 1210 100V
E10
CH1 OUT
TP10
GND
C25
OPT
0402
R9 10
FB4
FBMH2012HM331-T
L2
15uH
IHLE4040DDER150M5A
TP5
FAULT1
_____
C15 0.1uF 100V
D2
OPT
SOD-323F
R19
OPT
SW1 OUT1
VREF
FB1
OUT1
VIN1
FB1
VREF
VIN1 SW1

13
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
SCHEMATIC DIAGRAM
30VLED
250kHz
V22
V21
Vo2
I22 I21
1A
1. ALL RESISTORS 5%, 0402. 2. ALL CAPACITORS 0603. NOTES: UNLESS OTHERWISE SPECIFIED.
INTVCC
PVIN
VREF
VIN2
INTVCC
INTVCC
C37 OPT 1210
C28 OPT 1206 C43
0.1uF 100V
D6
OPT
SOD-323F
TP27
SGND
R47 10k 1%
E4
LED2+
C39 OPT 1210
R36 100K 1%
E15
CTRL2
TP25
VEXT2
C40 OPT 1210
R42 30k
U1-1
LT8355IUFDM-1
CTRL2
8FB2 18
GATE2 23
IADJ2
9
INTVCC 22
ISN2 20
ISP2 19
GND 29
PWM2
11
PWMTG2 21
RT
12
SENSEN2 25
SENSEP2 24
FAULT2
13
VC2 17
VREF
14
C42
2.2uF
M10 SQJ211ELP
1 25 3
4
C36 4.7uF 1210 100V
R45 OPT
FB9
FBMH2012HM331-T
TP18
TP17
VC2
R37 OPT
C38 10uF 1210 50V
C44 OPT 1210
TP16
INTVCC
C50 OPT 0402
TP19
R38 OPT
C30 10uF 1210 25V
C51 OPT 0402
C34 680pF
L3
8.2uH
XAL6060-822MEC
12
D4
PDS3100Q
21 3
+
C29 100uF 25V
EEEHAE101XAP
R49 10
FB10
FBMH2012HM331-T
C31 4.7uF 25V 1210
E3
LED2-
VIN2
BUCK-BOOST
R51 OPT
TP20
L4
10uH
IHLE4040DDER100M5A
E9
LED2-
GND
BOOST
TP23
GND
R32
OPT
TP26
VREF
RS3 0.012 0612
C32 1210 25V 4.7uF
C45 10uF 1210 25V
R52 287K
TP21
R50 OPT
E11
CH2 OUT
R35 100K 1%
R48 OPT 0603
M9 SQJA72EP
52
4
1
3
C41
OPT 0402
C35 4.7uF 10V
R53
10k
R43
100k
FB6 OPT
R44 OPT
RS4 0.25
1206
R39
100k
R59 OPT
R41
10
0603
C46 OPT 0402
FB7 OPT
Q2 FMMT593Q
3 2
1
C48 OPT
E18
IADJ2
R46
OPT
TP13
FAULT2
______
C27 OPT 0402
C33 2.2uF 10V
FB8 OPT
D5
OPT
SOD-323F
C47 OPT
TP22
E17
PWM2
C49 0.1uF 50V
R40
0603
86.6k
SW2 OUT2
FB2VREF
VREF
VREF
OUT2
VIN2
FB2
VIN2 SW2

14
DEMO MANUAL EVAL-LT8355-1-AZ
Rev. 0
 ANALOG DEVICES, INC. 2022
10/22
www.analog.com
ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection
circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
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conditions set forth below (“Agreement”) unless you have purchased the Evaluation Board, in which case the Analog Devices Standard Terms and Conditions of Sale shall govern. Do not use the Evaluation
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Customer a free, limited, personal, temporary, non-exclusive, non-sublicensable, non-transferable license to use the Evaluation Board FOR EVALUATION PURPOSES ONLY. Customer understands and
agrees that the Evaluation Board is provided for the sole and exclusive purpose referenced above, and agrees not to use the Evaluation Board for any other purpose. Furthermore, the license granted
is expressly made subject to the following additional limitations:Customer shall not (i) rent, lease, display, sell, transfer, assign, sublicense, or distribute the Evaluation Board;and (ii) permit any Third
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