Linear Technology DC1878A Quick setup guide

dc1878af

DEMO MANUAL DC1878A

Description

LTC3789EGN

8V to 75VIN Buck/Boost

DC/DC Converter

Demonstration circuit 1878A features the LTC3789EGN,

a high efficiency switching step-up/down controller. The

input range has been extended to 75V by using a LTC4444-

5 MOSFET driver on the input side. The minimum input

voltage is 8V. The output voltage is 12V. The board is

capable of delivering up to 5A of output current over the

input voltage range.

The LTC3789EGN is a high performance switching regula-

tor controller designed to regulate the output using input

voltages above, below or equal to the output voltage.

Synchronous operation provides very high efficiency, up

to 97%. Constant frequency current mode architecture

allows phase-lockable frequency from 200kHz to 600kHz. L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of

Linear Technology Corporation. All other trademarks are the property of their respective owners.

performance summary

An accurate output current limit provides support for bat-

tery charging. A wide input and output range with smooth

transfer function through all operating modes makes the

productidealforautomotive,telecomandbattery systems.

The MODE/PLLIN pin can select between pulse-skipping

mode and forced continuous mode operation and allows

the IC to be synchronized to an external clock. A power

good output pin indicates when the output is within 7.5%

of its set point.

Design files for this circuit board are available at

http://www.linear.com/demo

(TA= 25°C)

PARAMETER CONDITIONS VALUE

Minimum Input Voltage 8V

Maximum Input Voltage 75V

Output Voltage VOUT Regulation VIN = 8V – 75V, IOUT = 0A – 5A 12V ± 2%

Maximum Continuous Output Current Some Airflow May Be Needed at High Input Voltage and

Continuous Full Load

Default Operating Frequency R3 = 0Ω 200kHz

External Clock Synchronous Frequency Range 200kHz – 600kHz

Efficiency VIN = 8V to 75V, IOUT = 5A 90.5% to 97%. See Figures 3 and 6

Load Transient See Figure 5

dc1878af

DEMO MANUAL DC1878A

Quick start proceDure

Demonstration circuit 1878A is easy to set up to evalu-

ate the performance of the LTC3789EGN. Please refer to

Figure 1 for proper measurement equipment setup and

follow the procedure below.

1. With power off, connect the input supply, load and

meters as shown in Figure 1. Preset the load to 0A and

VIN supply to 0V.

2. Set the current limit of the input supply high enough

so that the bench supply does not go into current limit

mode. Figure 2 shows input current as a function of

input voltage, at full load. Input current can reach 8A

at 8V input voltage.

3. Place jumper in the following position:

JP1

RUN

4. Turn on the power at the input. Increase VIN to between

8V and 75V. The circuit will start and the output voltage

will regulate at 12V ±2%. The current draw at no load is

typically 18mA to 37mA depending on the input voltage.

5. Apply load and observe output voltage regulation, ripple

voltage, efficiency and other parameters. Efficiency and

power loss at full load is shown in Figure 3. Continuous

operation with full power and high input voltage may

require some airflow.

Auxiliary Supply

The demo board DC1878A has a LTC3803 based flyback

converter to provide 8V/50mA bias voltage for LTC3789

and LTC4444-5. The snubber for the flyback primary wind-

ing provides a voltage that is above the input voltage. A

transistor Q9 is used to provide a small current source

to the top gate driver of LTC4444-5 so that 100% duty

cycle is possible.

If this current source is not used, for example if the flyback

auxiliary supply is replaced by an external 6V to 12Vsupply,

it is necessary to connect BOOST1 to 3.0V (add 3V Zener

diode D11, R11 = 1k, remove R16) and use a level shift

circuit (add D3 = BAS16, R12 = 1k, remove R6) between

TG1 and TINP (due to the 3.25V maximum threshold for

TINP). By setting BOOST1 to 3.0V, the LTC3789 will issue

narrow refresh pulses on BG1 which keeps the top gate

driver powered also in BOOST mode.

In addition, DC1878Ademoboard has layoutfor an optional

bias supply intended for a future monolithic high voltage

buck regulator. Additional information will be provided

when this part is released.

dc1878af

DEMO MANUAL DC1878A

Figure 1. Proper Measurement Equipment Setup

Quick start proceDure

dc1878af

DEMO MANUAL DC1878A

Quick start proceDure

Figure 2. Input Current at Full Load (12V at 5A Output)

Figure 3. Efficiency and Power Loss at Full Load. The Power Loss is Highest at High Input

Voltage Due to the Switching Losses and Drops as Input Voltage Decreases, Until the Inductor

Current Starts to Increase as the Circuit Enters Boost Mode Below 10V Input Voltage

INPUT VOLTAGE (V)

40302010 807060500

EFFICIENCY (%)

POWER LOSS (W)

100

PLOSS

η%

INPUT VOLTAGE (V)

40302010 807060500

CURRENT (A)

IOUT

IIN

dc1878af

DEMO MANUAL DC1878A

Quick start proceDure

Figure 4. Output Ripple Voltage Measured Across COUT1

100mV

dc1878af

DEMO MANUAL DC1878A

Quick start proceDure

Figure 5. Load Transient Response

dc1878af

DEMO MANUAL DC1878A

Quick start proceDure

Figure 6. Efficiency at Various Input Voltages

LOAD (A)

4321 50

EFFICIENCY (%)

100

12V

16V

24V

36V

48V

60V

72V

76V

dc1878af

DEMO MANUAL DC1878A

Figure 7. Output Current Limit (The Easiest Way to

Do This Test Is with an Active Load in Voltage Mode)

Quick start proceDure

LOAD (A)

4321 650

VOUT (V)

dc1878af

DEMO MANUAL DC1878A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

1 1 CC1 CAP, 0603 470pF 10% 50V NPO AVX 06035A471KAT

2 1 CC2 CAP, 0603 0.01µF 10% 50V X7R AVX 06035C103KAT2A

3 0 CF1, C31, C32, C37, CF CAP, 0603 OPTION OPTION

4 0 CIN1, COUT11, CIN11, COUT21, CIN21 CAP, OPTION OPTION

5 1 CIN2 CAP, 150µF 100V ELEC SUN ELEC. 100ME150AX

6 1 COUT1 CAP, 330µF 20% 16V OSCON SUN ELECT. 16SEP330M+T

7 0 COUT2 CAP, 330µF 20% 16V OSCON OPTION SUN ELECT. 16SEP330M+T OPTION

8 1 CSS CAP, 0603 4700pF 10% 50V X7R AVX 06035C472KAT2A

9 2 C1,C2 CAP, 1210 22µF 10% 25V X5R MURATA GRM32ER61E226KE15L

10 0 C3, C21, C23, C25, C27, C28 CAP, 1210 OPTION OPTION

11 1 C4 CAP, 0603 0.22µF 10% 25V X7R AVX 06033C224KAT2A

12 3 C5, C6, C9 CAP, 1210 2.2µF 10% 100V X7R MURATA GRM32ER72A225KA35L

13 0 C7, C8, C29, C30, C33 CAP, 1210 2.2µF 10% 100V X7R OPTION MURATA GRM32ER72A225KA35L OPTION

14 1 C10 CAP, 0603 4.7µF 20% 6.3V X5R TAIYO YUDEN JMK 107 BJ457MA-T

15 1 C11 CAP, 0603 33pF 10% 50V NPO AVX 06035A330KAT2A

16 0 C12, C13 CAP, 1206 OPTION OPTION

17 3 C14, C16, C26 CAP, 0603 0.1µF 10% 50V X7R AVX 06035C104KAT2A

18 1 C15 CAP, 0805 1µF 20% 16V X5R AVX 0805YD105MAT2A

19 1 C17 CAP, 0603 1nF 10% 50V COG AVX 06035A102KAT2A

20 2 C18, C20 CAP, 1206 10µF 20% 10V X7R AVX 1206ZC106MAT2A

21 2 C19, C24 CAP, 0603 1µF 20% 16V X7R AVX 0603YC105MAT2A

22 1 C22 CAP, 0603 0.22µF 20% 16V X7R TAIYO YUDEN EMK107BJ224MA

23 0 C34 CAP, 0603 0.1µF 10% 50V X7R OPTION AVX 06035C104KAT2A OPTION

24 0 C35 CAP, 0603 47nF 10% 25V X7R OPTION AVX 06033C473KAT2A OPTION

25 0 C36 CAP, 1210 47µF 10% 10V X7R OPTION MURATA GRM32ER71A476KE15L OPTION

26 3 D2, D9, D12 DIODE, SWITCHING, 200mW, SOT23 DIODES INC. BAS16

27 0 D3, D10, D11 DIODE, OPTION SOT-23 OPTION

28 2 D4, D14 DIODE, SWITCHING, 350mW, SOT23 DIODES INC. BAS21

29 1 D5 DIODE, SCHOTTKY DIODES INC. B1100

30 1 D6 DIODE, SCHOTTKY, SMA DIODES INC. B240A-13-F

31 1 D7 DIODE, SCHOTTKY DIODES INC. DFLS160

32 1 D8 DIODE, ZENER, 5.1V, SOT23 DIODES INC. BZX84C5V1-7-F

33 1 D13 DIODE, ZENER, 6.8V, SOT23 DIODES INC. BZX84C6V8

34 1 D15 DIODE, 1.0A HIGH VOLTAGE SCHOTTKY

BARRIER RECTIFIER

DIODES INC. DFLS1100

35 1 JP1 HEADER, SINGLE ROW, 3 PIN, 2mm SAMTEC TMM103-02-L-S

36 0 JP2 HEADER, SINGLE ROW, 3 PIN, 2mm

OPTION

SAMTEC TMM103-02-L-S OPTION

37 4 J1, J2, J3, J4 JACK, BANANA KEYSTONE 575-4

38 1 L1 IND, 19µH PULSE PA2050.193NL

39 0 L2 IND, 22µH OPTION TDK VLF10040T-220M2R5 OPTION

40 4 MH1, MH2, MH3, MH4 STANDOFF, SNAP ON KEYSTONE_8834

dc1878af

DEMO MANUAL DC1878A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

41 1 Q1 XSTR, FDC2512 N-CHANNEL MOSFET FAIRCHILD FDC2512

42 1 Q2 XSTR, MOSFET N-CHANNEL 100V VISHAY SiR870DP

43 2 Q3, Q5 XSTR, MOSFET N-CHANNEL 20V VISHAY SiR496DP-T1-GE3

44 1 Q4 XSTR, MOSFET N-CHANNEL 100V VISHAY SiR882DP

45 1 Q6 XSTR, SMALL SIGNAL NPN SOT-23 DIODES INC. MMBTA42-7

46 0 Q8, Q13 XSTR, MOSFET N-CHANNEL 20V OPTION VISHAY SiR496DP-T1-GE3 OPTION

47 1 Q9 XSTR, SMALL SIGNAL PNP SOT-23 DIODES INC. MMBTA92-7

48 0 Q14, Q15 XSTR, MOSFET N-CHANNEL 100V OPTION VISHAY SiR882DP OPTION

49 1 RC RES, 0603 14.7kΩ 1% 1/10W VISHAY CRCW060314K7FKEA

50 1 RFB1 RES, 0603 113kΩ 1% 1/10W VISHAY CRCW0603113KFKEA

51 1 RFB2 RES, 0603 8.06kΩ 1% 1/10W VISHAY CRCW06038K06FKEA

52 1 R1 RES, 0805 5.6Ω 1% 1/10W VISHAY CRCW08055R60FKNEA

53 1 R2 RES, 3720 0.01Ω 2% 1W THIN FILM RECH. RL3720WT-R010-F

54 3 R3, R4, R44 RES, 0603 100Ω 5% 1/10W VISHAY CRCW0603100RJNEA

55 1 R5 RES, 0805 4.7Ω 1% 1/10W VISHAY CRCW08054R70FKNEA

56 8 R6, R11, R16, R21, R25, R27, R32, R50 RES, 0603 0Ω JUMPER VISHAY CRCW06030000Z0EA

57 3 R7, R15, R20 RES, 0603 100kΩ 1% 1/10W VISHAY CRCW0603100KFKEA

58 2 R8, R26 RES, 0603 10Ω 5% 1/10W VISHAY CRCW060310R0JNEA

59 2 R9, R10 RES, 0603 1kΩ 1% 1/10W VISHAY CRCW06031K00FKEA

60 0 R12, R19, R22, R23, R33-R36, R51 RES, 0603 OPTION OPTION

61 2 R13, R14 RES, 0603 154kΩ 1% 1/10W VISHAY CRCW0603154KFKEA

62 0 R17 RES, 0805 0Ω JUMPER OPTION VISHAY CRCW08050000Z0EA OPTION

63 1 R18 RES, 3720 0.012Ω 2% 1W THIN FILM TECH. RL3720WT-R012-F

64 1 R24 RES, 0603 10kΩ 1% 1/10W VISHAY CRCW060310K0FKEA

65 0 R28, R29 RES, 1206 OPTION OPTION

66 1 R30 RES, 1206 64.9kΩ 1% 1/10W VISHAY CRCW120664K9FKEA

67 1 R31 RES, 0603 12.1kΩ 1% 1/10W VISHAY CRCW060312K1FKEA

68 1 R37 RES, 0603 14kΩ 1% 1/10W VISHAY CRCW060314K0FKEA

69 1 R38 RES, 1206 220kΩ 5% 1/4W VISHAY CRCW1206220KJNEA

70 1 R39 RES, 1206 100kΩ 1% 1/10W VISHAY CRCW1206100KFKEA

71 1 R40 RES, 0603 22.1kΩ 1% 1/10W YAGEO RC0603FR-0722KIL

72 1 R41 RES, 0603 1.58kΩ 1% 1/10W VISHAY CRCW06031K58FKEA

73 1 R42 RES, 0603 10Ω 1% 1/8W VISHAY CRCW060310R0FKEA

74 1 R43 RES, 1206 0.30Ω 1% 1/8W IRC LR1206LF-01-R300-F

75 1 R45 RES, 0603 24.9kΩ 1% 1/10W NIC NRC06F2492TRF

76 2 R46, R47 RES, 0603 33.2kΩ 1% 1/10W VISHAY CRCW060333K2FKEA

77 1 R48 RES, 0603 5.6kΩ 1% 1/10W VISHAY CRCW06035K49FKEA

78 0 R49, R55, R56 RES, 0603 0Ω JUMPER OPTION VISHAY CRCW06030000Z0EA OPTION

79 0 R52 RES, 0603 2MΩ 1% 1/10W OPTION VISHAY CRCW06032M00FKEA OPTION

80 0 R53 RES, 0603 102kΩ 1% 1/10W OPTION VISHAY CRCW0603102KFKEA OPTION

81 0 R54 RES, 0603 11.3kΩ 1% 1/10W OPTION VISHAY CRCW060311K3FKEA OPTION

82 4 TP1, TP2, TP3, TP7 TURRET MILL-MAX 2308-2-00-80-00-00-07-0

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