DC950A-B - LINEAR TECHNOLOGY

LT3825 AND LT3837

DESCRIPTION

Demonstration circuit 950A is a 30W multi-output syn-

chronous flyback converter in 1/8 brick format featuring

the LT3825 and LT3837. Output voltage sensing is im-

plemented without the use of opto-coupler, by sensing

the voltage across a primary side auxiliary winding. A

load compensation circuit is used to compensate for

voltage drops caused by load currents.

DC950A-A has input voltage range 36V-72V and features

the LT3825.

DC950A-B has input voltage range 9V-36V and features

the LT3837.

Demonstration circuit 950A uses a transformer design

with tapped secondary winding, to achieve higher effi-

ciency and better cross regulation than is possible with a

transformer that uses a separate winding for each out-

put.

Design files for this circuit board are available. Call

the LTC factory.

L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered

trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy

Drive, FilterCAD, Hot Swap, LinearView, µModule, Micropower SwitcherCAD, Multimode

Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No RSENSE, Operational Filter, PanelProtect,

PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT,

UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names

may be trademarks of the companies that manufacture the products.

PERFORMANCE SUMMARY

Specifications are at TA = 25°C

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Range DC950A-A

DC950A-B

OUT

Output Voltage V

OUT1

OUT2

OUT3

4.85

3.20

2.42

3.3V

2.5V

5.15

3.40

2.58

OUT

Output Current (Note: Total output power not to

exceed 30W)

OUT1

(5V output)

OUT2

(3.3V output)

OUT3

(2.5V output)

Efficiency

Efficiency DC950A-A,V

=48V,I

OUT1

=2A,I

OUT1

=3A,I

OUT3

=3A

DC950A-B,V

=24V,I

OUT1

=2A,I

OUT1

=3A,I

OUT3

=3A

EQUIPMENT

8 DMMs

1 DC Supply 0-72V 1A for DC950A-A test

1 DC Supply 0-36V 5A for DC950A-B test

3 Adjustable loads 0-3A

DEMO CIRCUI

950

QUICK START GUID

LT3825 and LT3837

Non-opto Synchronous Fly

back Controlle

LT3825 AND LT3837

GETTING STARTED

Demonstration circuit 950A is easy to set up to evaluate

the performance of the LT3825 and LT3837. Refer to

Figure 1 for proper measurement equipment setup and

follow the procedure below:

With power off, connect the input power supply to Vin

and GND.

With no loads, adjust input voltage to be within the

input voltage range (36V-72V for DC950A-A, 9V-36V

for DC950A-B) and turn on the power at the input.

Check for the proper output voltages. Vout1 = 5V,

Vout2 = 3.3V, Vout3 = 2.5V.

Adjust the loads and study the performance of the

circuit. Note that the load current should not exceed

4A, and the total load on the three outputs should not

exceed 30W continuous power.

Figure 1.

Proper Measurement Equipment Setup

LT3825 AND LT3837

DC950A-A BILL OF MATERIAL

Item Qty Reference Part Description Manufacture / Part #

REQUIRED CIRCUIT COMPONENTS1

1 1 C38 Capacitor, NP0, 33pF, 50V, 0603 AVX, 06035A330KAT2

2 1 C41 Capacitor, NPO, 330PF, 50V, 0603 AVX, 06035A331KAT

3 1 C1 Capacitor, NPO 330PF 100V 1206 AVX, 12061A331KAT

4 2 C34,C30 Capacitor, X7R, 2200pF, 50V, 0603 AVX, 06035C222JAT

5 3 C19,C31,C32 Capacitor, X5R, 0.1uF, 25V, 0603 AVX, 06033D104KAT2A

6 1 C40 Capacitor, X7R, 1000pF, 50V, 0603 AVX, 06035C102KAT2A

7 1 C36 Capacitor, X5R, 0.47uF, 16V, 0603 AVX, 0603YD474M

8 6 C3,C4,C13,C14,C26,C27 Capacitor, X5R, 47uF, 6.3V, 1210 TDK, 3225X 5R0J476M

9 0 C33,C39 Capacitor, 0603 OPT

10 1 C35 Capacitor, X7R, 3300PF, 50V, 0603 KEMET, C0603C332J5RAC

11 1 C37 Capacitor, NPO, 680PF, 50V, 0603 AVX, 06035A681JAT

12 1 C9 Capacitor, NPO, 150pF, 200V, 1206 AVX, 12062A151KAT2A

13 1 C18 Capacitor, X7R, 22uF, 16V, 1210 TDK, C3225RX7R1C226M

14 2 C20,C21 Capacitor, X7R, 2.2uF, 100V, 1812 TDK, C4532X7R2A225M

15 1 D2 BAS21 Diodes, Inc.,BAS21-7-F

16 2 D8,D6 BAT54 Diodes, Inc.,BAT54-7-F

17 1 D5 BAT54A Diodes, Inc.,BAT54A-7

18 1 D10 BAT54S Diodes, Inc.,BAT54S-7-F

19 1 D9 B0530W Diodes, Inc.,B0530W-7-F

20 0 D4 Zenerdiode, 12V, 5%, SOT23 OPT

21 1 L5 Inductor, 330uH Coilcraft, DO1608C-334MLB

22 1 L6 Inductor, 120uH Wurth Elektronik, 744 032 121

23 1 Q1 MOSFET, n-ch, SO8 Vishay, Si4850EY-T1-E3

24 1 Q3 MOSFET, n-ch, SO8 Vishay, Si4840DY-T1-E3

25 2 Q7,Q9 Transistor, npn, SOT23 Zetex, FMMT619TA

26 3 Q8,Q10,Q12 Transistor, pnp, SOT23 Zetex, FMMT718TA

27 0 Q4 Transistor, npn, SOT23 OPT

28 1 Q5 MOSFET, n-ch, SO8 Vishay, Si4840DY-T1-E3

29 1 Q6 MOSFET, n-ch, SO8 Vishay, Si4488DY-T1-E3

30 1 R11 Resistor, 0 OHMS 0603 VISHAY, CRCW06030000Z0EA

31 1 R2 Resistor, 18 OHMS 1206 VISHAY, CRCW120618R0JNEA

32 2 R21,R16 Resistor, 15 OHMS 0603 VISHAY, CRCW060315R0FKEA

33 1 R15 Resistor, 330 OHMS 0603 VISHAY, CRCW0603330RFKEA

34 2 R9,R29 Resistor, 1.00k, 0603 VISHAY, CRCW06031K0FKED

35 1 R14 Resistor, 1.00k, 0805 VISHAY, CRCW08051K0FKED

36 1 R22 Resistor, 3.01K, 0603 VISHAY, CRCW06033011FRT6

37 1 R30 Resistor, 4.64K, 0603 VISHAY, CRCW06034K64FKED

38 3 R19,R23,R28 Resistor, 10.0K, 0603 VISHAY, CRCW060310K0FKED

39 1 R12 Resistor, 28.7K, 0805 VISHAY, CRCW080528K7FKED

40 1 R25 Resistor, 100K, 0603 VISHAY, CRCW0603100KJNEA

41 1 R27 Resistor, 150K, 0603 VISHAY, CRCW0603150KJNEA

42 1 R5 Resistor, 22 OHM, 1206 VISHAY, CRCW120622ROJNEA

43 1 R17 Resistor, 0.025 OHM 1% 1206 IRC, LRF1206LF-01-R025-F

44 1 R26 Resistor, 1.00K, 0603 VISHAY, CRCW06031K00FKEA

45 1 R6 Resistor, 47K, 1206 VISHAY, CRCW120647K0JNEA

46 1 R13 Resistor, 402K, 0805 VISHAY, CRCW0805402KFKEA

47 0 R4,R18 Resistor, 1206 OPT

48 1 R8 Resistor, 91 OHMS 0805 VISHAY, CRCW080591R0FKEA

49 1 R20 Resistor, 14.7K, 0603 VISHAY, CRCW060314K7FKEA

50 1 R24 Resistor, 12.4K, 0603 VISHAY, CRCW060312K4FKEA

LT3825 AND LT3837

51 1 T2 Gatedrive transformer Pulse Engineering, PA0173

52 1 T1 EFD20 Flyback transformer Pulse Engineering, PA2046NL

53 1 U1 LT3825EFE#PBF Linear Technology,

LT3825EFE#PBF

ADDITIONAL DEMO BOARD CIRCUIT COMPO NENTS2

1 1 C8 Capacitor, electrolytic, 12UF, 100V Sanyo, 100ME12AX+TS

2 3 C7,C17,C23 Capacitor, TANT, 100uF, 6.3V, 3528 Kemet, T520B107M006ASE070

3 1 C43 Capacitor, X7R, 4700pF 250V, 1812 MURATA,

GA343DR7GD472KW01L

4 3 L1,L3,L4 Inductor, 0.2uH Cooper, FP2-S200

5 1 L2 Inductor, 4.7u H Cooper, HCP0703-4R7-R

HARDWARE-FOR DEMO BOARD ONLY:

1 4 (STAND-OFF), STAND-OFF, NYLON 0.50" KEYSTONE, 8833(SNAP ON)

2 6 E1-E6 Turret, 0.094" Mill-Max, 2501-200-80-00-00-07-0

Notes:

1. Required Circuit Component s are those parts that are required to implement the circuit function

2. Additional Demo Board Circuit Component s are those parts that provide added functionality for the demo

board but

are not required in the actual circuit.

DC950A-B BILL OF MATERIAL

Item Qty Reference Part Description Manufacture / Part #

REQUIRED CIRCUIT COMPONENTS1

1 1 C38 Capacitor, NP0, 33pF, 50V, 0603 AVX, 06035A330KAT2

2 1 C41 Capacitor, NPO, 330PF, 50V, 0603 AVX, 06035A331KAT

3 1 C1 Capacitor, NPO 330PF 100V 1206 AVX, 12061A331KAT

4 2 C34,C30 Capacitor, X7R, 2200pF, 50V, 0603 AVX, 06035C222JAT

5 3 C19,C31,C32 Capacitor, X5R, 0.1uF, 25V, 0603 AVX, 06033D104KAT2A

6 1 C40 Capacitor, X7R, 1000pF, 50V, 0603 AVX, 06035C102KAT2A

7 1 C36 Capacitor, X5R, 0.47uF, 16V, 0603 AVX, 0603YD474M

8 6 C3,C4,C13,C14,C26,C27 Capacitor, X5R, 47uF, 6.3V, 1210 TDK, 3225X5R0J476M

9 0 C33,C39 Capacitor, 0603 OPT

10 1 C35 Capacitor, X7R, 3300PF, 50V, 0603 KEMET, C0603C332J5RAC

11 1 C37 Capacitor, NPO, 680PF, 50V, 0603 AVX, 06035A681JAT

12 1 C9 Capacitor, NPO, 560pF, 100V, 1206 AVX, 12061A561KAT2A

13 0 C18 Capacitor, 1210 OPT

14 2 C20,C21 Capacitor, X7R, 4.7uF, 50V, 1812 TDK,C4532X7R1H475MT

15 1 D2 BAS21 Diodes, Inc.,BAS21-7-F

16 2 D8,D6 BAT54 Diodes, Inc.,BAT54-7-F

17 1 D5 BAT54A Diodes, Inc.,BAT54A-7

18 1 D10 BAT54S Diodes, Inc.,BAT54S-7-F

19 1 D9 B0530W Diodes, Inc.,B0530W-7-F

20 1 D4 Zenerdiode, 11V, 5%, SOT23 Vishay, BZX84C11-V

21 1 L5 Inductor, 330uH Coilcraft, DO1608C-334MLB

22 1 L6 Inductor, 120uH Wurth Elektronik, 744 032 121

23 1 Q1 MOSFET, n-ch, SO8 Vishay, Si4850EY-T1-E3

24 1 Q3 MOSFET, n-ch, SO8 Vishay, Si4840DY-T1-E3

25 2 Q7,Q9 Transistor, npn, SOT23 Zetex, FMMT619TA

26 3 Q8,Q10,Q12 Transistor, pnp, SOT23 Zetex, FMMT718TA

LT3825 AND LT3837

27 1 Q4 Transistor, npn, SOT23 MMBT3904L T

28 1 Q5 MOSFET, n-ch, SO8 Renesas, HAT2165H

29 1 Q6 MOSFET, n-ch, SO8 Vishay, Si7852DP-T1-E3

30 1 R11 Resistor, 0 OHMS 0603 VISHAY, CRCW06030000 Z0EA

31 1 R2 Resistor, 18 OHMS 1206 VISHAY, CRCW120618R0JNEA

32 2 R21,R16 Resistor, 15 OHMS 0603 VISHAY, CRCW060315R0FKEA

33 1 R15 Resistor, 330 OHMS 0603 VISHAY, CRCW0603330RFKEA

34 2 R9,R29 Resistor, 1.00k, 0603 VISHAY, CRCW06031K0FKED

35 1 R14 Resistor, 1.00k, 0805 VISHAY, CRCW08051K0FKED

36 1 R22 Resistor, 3.01K, 0603 VISHAY, CRCW06033011 FRT6

37 1 R30 Resistor, 4.64K, 0603 VISHAY, CRCW06034K64FKED

38 3 R19,R23,R28 Resistor, 10.0K, 0603 VISHAY, CRCW060310K0FKED

39 1 R12 Resistor, 28.7K, 0805 VISHAY, CRCW080528K7FKED

40 1 R25 Resistor, 100K, 0603 VISHAY, CRCW0603100 K JNEA

41 1 R27 Resistor, 150K, 0603 VISHAY, CRCW0603150 K JNEA

42 1 R5 Resistor, 22 OHM, 1206 VISHAY, CRCW120622ROJNEA

43 2 R17,R18 Resistor, 0.015 OHM 1% 1206 IRC, LRF12 06-01-R015-F

44 1 R26 Resistor, 750 OHMS, 0603 VISHAY, CRCW0603750RFKEA

45 1 R4 Resistor, 4.7k, 1206 VISHAY, CRCW12064K70FKEA

46 1 R13 Resistor, 121K, 0805 VISHAY, CRCW0805121KFKEA

47 0 R6 Resistor, 1206 OPT

48 1 R8 Resistor, 22.1 OHMS 080 5 VISHAY, CRCW080522R1FKEA

49 1 R20 Resistor, 22.1K, 0603 VISHAY, CRCW060322K1FKEA

50 1 R24 Resistor, 13.0K, 0603 VISHAY, CRCW060313K0FKEA

51 1 T2 Gatedrive transformer Pulse Engineering, PA0173

52 1 T1 EFD20 Flyback transformer Pulse Engineering, PA2047NL

53 1 U1 LT3837EFE#PBF Linear Technology,

LT3837EFE#PBF

ADDITIONAL DEMO BOARD CIRCUIT COMPO NENTS2

1 1 C8 Capacitor, electrolytic, 47UF, 50V Sanyo, 50ME47AX+TS

2 3 C7,C17,C23 Capacitor, TANT, 100uF, 6.3V, 3528 Kemet, T520B107M006ASE070

3 1 C43 Capacitor, X7R, 4700pF 250V, 1812 MURATA,

GA343DR7GD472KW01L

4 3 L1,L3,L4 Inductor, 0.2uH Cooper, FP2-S200

5 1 L2 Inductor, 4.7u H Cooper, HCP0703-4R7-R

HARDWARE-FOR DEMO BOARD ONLY:

1 4 (STAND-OFF), STAND-OFF, NYLON 0.50" KEYSTONE, 8833(SNAP ON)

2 6 E1-E6 Turret, 0.094" Mill-Max, 2501-200-80-00 -00-07-0

Notes:

1. Required Circuit Component s are those parts that are required to implement the circuit function

2. Additional Demo Board Circuit Component s are those parts that provide added functionality for the demo

board but

are not required in the actual circuit.