DC324A - Linear Technology - Datasheet.Directory

DEMO BOARD MANUAL DC324

LTC1876 High Efficiency, Low Cost, 3-Output Power Supply

DESCRIPTION

Demonstration Board DC324 is a high efficiency, low cost design using the LTC1876.

This demo board provides three regulated outputs from a single IC: 3.3V/5A, 5V/5A and

12V/200mA, along with two LDO outputs at 3.3V and 5V. Using only a small number of

surface mount components, this design is ideal for network equipment, notebook

computers and other portable applications that require low profile, small board area and

minimum system cost. High efficiency and low EMI are also achieved by operating the

two main power stages 180° out of phase, which, in turn, results in long battery life and

smaller input capacitors. All three main outputs can be adjusted externally and the 12V

regulator is configured to receive its input from the 3.3V output, the 5V output or an

external supply.

DC324 highlights the capabilities of the LTC1876, which incorporates a dual out-of-

phase, step-down switching controller and a step-up regulator with an internal 1A, 36V

switch. It uses a constant frequency, current mode architecture to provide excellent line

and load regulation for all three outputs. The operating frequency of the step-down

controller is DC programmable from 150kHz to 300kHz and the frequency of the step-up

regulator is fixed at 1.2MHz, allowing the use of tiny, low cost capacitors and inductors.

Protection features of the controller include an overvoltage soft latch, an overcurrent

latch-off (which can be externally defeated) and internal current foldback for overload

situations. At low output currents, two modes of operation are available: Burst Mode

operation to maintain high efficiency and burst disable mode to maintain constant

frequency operation. The controller is also capable of very low dropout operation, with a

99% maximum duty cycle. To be compatible with battery operation, the input range of

this demo board is 7.5V to 24V for the 3.3V and 5V outputs and from 3V to10V for the

12V output. Gerber files for this circuit board are available. Call the LTC factory.

PERFORMANCE SUMMARY (Operating Temperature Range: 0°C to 50°C)

PARAMETERS CONDITIONS VALUE

Step-Down Channels (VOUT = 5V and 3.3V); Limited by

External MOSFET Drive and Breakdown Requirement

5.2V to 30VInput Voltages

Step-Up Channel (VOUT = 12V) 2.6V to 11V

Step-Down Channel 1; Externally Adjustable 5.00V ± 0.10V

Step-Down Channel 2; Externally Adjustable 3.30V ± 0.07V

Step-Up Channel; Externally Adjustable 12.00V ± 0.24V

5V Linear Regulator 5.00V ± 4%

Output Voltages

3.3V Linear Regulator 3.30V ± 4%

Step-Down Channels 0 to 5A, 6A Peak

VIN2 = 3.3V 200mA

Load Currents

Step-Up Channel

VIN2 = 10V 600mA

PARAMETERS CONDITIONS VALUE

Step-Down Channels; Externally Adjustable; FREQSET Pin

Tied to INTVCC

300kHzFrequencies

Step-Up Channel; Fixed 1.2MHz

Step-Down Channel 1; 20MHz BW; VIN = 15V; IO = 5A 60mVP-P

Step-Down Channel 2; 20MHz BW; VIN = 15V; IO = 5A 60mVP-P

Output Ripple Voltages

Step-Up Channel; 20MHz BW; VIN2 = 5V; IO = 200mA 50mVP-P

Step-Down Channel 1; VIN = 7.5V to 24V ±5mV

Step-Down Channel 2; VIN = 7.5V to 24V ±5mV

Line Regulation

Step-Up Channel; VIN = 3.3V to 10V ±5mV

Step-Down Channel 1; VIN = 15V; VOUT1 = 5.00V; IO = 0 to 5A −60mV

Step-Down Channel 2; VIN = 15V; VOUT2 = 3.30V; IO = 0 to 5A −60mV

Load Regulation

Step-Up Channel; VIN = 5V; VOUT3 = 12.00V; IO = 0 to 200mA −10mV

Supply Current VIN = 15V; All Three Channels On; EXTVCC = VOUT1 80µA*

Shutdown Current VIN = 15V; STBYMD = 0 20µA

Standby Current VIN = 15V; 1MΩ Resistor from STBYBD to VIN; 5V INTVCC and

3.3V LDO On; RUN/SS1 = RUN/SS2 = AUXSD = 0

170µA

Efficiency VIN = 15V; VIN2 = VOUT1; 4A Load at 5V Channel (Not Including

the Supply Current to 12V Channel); 5A Load at 3.3V

Channel; 200mA at 12V Channel

90%

*400µA including the supply current from EXTVCC. Dynamic supply current is higher

due to the gate charge being delivered at the switching frequency. See the LTC1876 data

sheet for more information.

TYPICAL PERFORMANCE CHARACTERISTICS

1; 5V Channel (Both 3.3V and 12V Channels are OFF)

Vin(V) Iin(A) Vout(V) Iout(A) Eff.(%)

15 0.004 5.02 0 0

15 0.01 5.01 0.015 50.1

15 0.023 5 0.052 75.36232

15 0.041 4.99 0.102 82.76098

15 0.182 4.99 0.496 90.66081

15 0.356 4.98 1.004 93.63146

15 0.706 4.98 2.003 94.19207

15 1.066 4.98 3.002 93.49568

15 1.44 4.98 4.002 92.26833

15 1.822 4.97 4.99 90.74387

2; 3.3V Channel (Both 5V and 12V Channels are OFF)

Vin(V) Iin(A) Vout(V) Iout(A) Eff.(%)

15 0.004 3.38 0 0

15 0.008 3.37 0.014 39.31667

15 0.017 3.356 0.051 67.12

15 0.03 3.346 0.102 75.84267

15 0.131 3.339 0.505 85.81145

15 0.251 3.337 1.004 88.98667

15 0.488 3.335 2.003 91.2569

15 0.735 3.334 3.002 90.78157

15 0.995 3.329 4.001 89.24174

15 1.264 3.32 4.99 87.37764

3; 12V Channel (Both 5V and 3.3V Channels are OFF)

Vin(V) Iin(mA) Vout(V) Iout(mA) Eff.(%)

5 6 11.96 0 0

5 46 11.97 14 72.86087

5 145 11.95 51 84.06207

5 280 11.94 101 86.13857

5 336 11.94 122 86.70714

5 392 11.94 142 86.50408

5 452 11.94 163 86.11593

5 502 11.94 181 86.1012

5 563 11.94 201 85.25542

100

0.01 0.1 1 10

Efficiency of 5V

Efficiency of 3.3V

Load Current (A)

Vin=15V

10 100 1000

Efficiency of 12V

Load Current (mA)

Vin2=5V

MEASUREMENT SETUP

The circuit shown in Figure 1 provides three fixed voltages: 5V, 3.3V and 12V, at

currents of up to 5A, 5A and 200mA, respectively. Figure 2 illustrates the correct

measurement setup to be used to verify the typical numbers found in the Performance

Summary table. Small spring clip leads are very convenient for small-signal bench testing

but should not be used at the current and impedance levels associated with this switching

regulator. Soldered wire connections are requited to properly ascertain the performance

of this demonstration board. Do not tie the grounds together off the test board.

The six jumpers on the left side of the board are settable as follows: the center pin is

connected to ground when the jumper is in the rightmost position. The center pin is

connected to a positive bias source when the jumper is in the leftmost position. The

jumper below L2 at the lower right side of the board is used to select the input supply for

the step-up channel. VOUT2 (3.3V) is selected if this jumper is in the leftmost position and

VOUT1 (5V) is selected if it is in the rightmost position. This jumper should be left off

when a separate power supply is used through the VIN2 terminal near the jumper. Refer to

the Jumper Configuration table for jumper functions.

QUICK START GUIDE

This demonstration board is easily set up to evaluate the performance of the LTC1876.

Please follow the procedure outlined below for proper operation.

1. Refer to Figure 2 for board orientation and proper measurement equipment setup.

2. Place the jumpers as shown in the diagram. Temporarily leave the STDBY jumper

off.

3. Connect the desired loads between VOUT1, VOUT2 and VOUT3 and their closest GND

terminals on the board. The loads can be up to 5A for VOUT1 and VOUT2 and 200mA

for VOUT3. Soldered wires should be used when load current exceeds 1A in order to

achieve optimum performance.

4. Connect the input power supply to the VIN and GND terminals on the right edge of

the board. Do not increase VIN over 30V or the MOSFETs may be damaged. The

recommended VIN to start is <7V.

12V/O.2A GND 3.3V/5A

3.3V

INTVCC

PGOOD

GND 5V/5A

VIN2

VOUT1

VIN2

VOUT2

VIN

GND

RUN/SS

FREQ

STDBY

FCB

RUN/SS2

AUXSD

LTC1876CG

DEMO CIRCUIT 324A

HIGH EFFICIENCY

LOW COST 3-OUTPUT

POWER SUPPLY

LOAD

–

Figure 2. DC324A Test and Measurement Setup

5. Switch on the step-down channel(s) by removing the RUN/SS1 or RUN/SS2 jumpers.

6. Measure VOUT1 and VOUT2 to verify output voltages of 5.00V ±0.10V and 3.30V

±0.07V, respectively, at load currents of up to 5A each.

7. Connect the jumper below L2 to select the input supply for the step-up channel. Refer

to the Measurement Setup section for proper connection. When VOUT1 or VOUT2 is

selected, reduce the load level of the selected output below 4A or the total load

current of the selected channel may exceed 5A.

8. Switch on the step-up channel by placing the AUXSD jumper in the leftmost position.

Active loads can cause confusing results. Refer to the active load discussion in the

Operation section.

JUMPER CONFIGURATION

Left Right Open

RUN/SS Over-Current Latch-Off

of Channel 1 Defeated

Channel 1 Shut Off Over-Current Latch-Off

of Channel 1 Enabled

FREQ 300kHz for Channels 1

and 2

150kHz for Channels 1

and 2

230kHz for Channels 1

and 2

STDBY 5V and 3.3V LDOs

Turned On

Channels 1 and 2 Shut

Off

Channels 1 and 2

Released

FCB Discontinuous Operation

Enabled at Channels 1

and 2

Forced Continuous

Operation at Channels 1

and 2

Do Not Leave This

Jumper Open

RUN/SS2 Over-Current Latch-Off

of Channel 2 Defeated

Channel 2 Shut Off Over-Current Latch-Off

of Channel 2 Enabled

AUXSD Channel 3 Enabled Channel 3 Shut Off Channel 3 Shut Off

VIN2 VIN2 = VOUT2 Selected VIN2 = VOUT1 Selected A Separate Supply

Selected through VIN2

Terminal

Linear Technology Corporation

LTC1876CG

Bill Of Material

Demo Bd. #324A

6/16/2005

12:09 PM

Item Qty Reference Part Description Manufacture / Part #

1 6 C1,C4,C7,C16,C21,C29 Capacitor, X7R 0.1uF 10V 20% AVX 0603ZC104MAT2A

2 2 C2,C20 Capacitor, NPO 27pF 25V 5% AVX 06033A270JAT1A

3 2 C3,C19 Capacitor, NPO 1000pF 25V 5% AVX 06033A102JAT1A

4 1 C5 Capacitor, Alum 33uF 35V 10% OSCON 35CV33BS

5 1 C6 Capacitor, Spcl. Poly. 47uF 6.3V 20% PANASONIC EEFCD0J470R

6 1 C8 Capacitor, Tant. 4.7uF 10V 20% AVX TACR475M010R

7 1 C9 Capacitor, NPO 220pF 25V 5% AVX 06033A221JAT1A

8 1 C10 Capacitor, Spcl. Poly. 56uF 4V 20% PANASONIC EEFCD0G560R

9 4 C11,C24,C25,C26 Capacitor, Y5V 1uF 10V 80% AVX 0603ZG105ZAT2A

10 3 C12,C13,C18 Capacitor, X7R .01uF 10V 10% AVX 0603ZC103KAT1A

11 2 C14,C17 Capacitor, NPO 33pF 50V 10% AVX 06035A330KAT1A

12 1 C15 Capacitor, NPO 470pF 25V 5% AVX 06033A471JAT1A

13 1 C22 Capacitor, Tant. 10uF 20V 20% AVX TPSB106M020

14 1 C23 Capacitor, X7R 2.2uF 25V 20% AVX 12103C225MAT2A

15 0 C27 (Optional) Capacitor, X7R 10uF 35V 20% Taiyo Yuden GMK325BJ106M

16 1 C28 Capacitor, X5R 10uF 25V 20% Taiyo Yuden TMK432BJ106MN-T

17 2 C30,C31 Capacitor, Y5V 10uF 35V 20% Taiyo Yuden GMK325F106ZH

18 2 D1,D4 Diode, Rectifier, 40V / 40Amp Diodes Inc. B140B-13

19 1 D3 Schottky (Comm-Anode) Zetex BAT54ATA

20 1 D5 Schottky Diode Central Semi. Corp CMDSH-3

21 6 XJP1-XJP2,XJP4-XJP7 SHUNT, .079" CENTER COMM-CON CCIJ2MM-138G

22 7 JP1-JP7 Headers, 3 pins Comm-Conn. 2870MS-03G2

23 2 L2,L1 Inductor, 4.6uH Sumida CEP123-4R6MC

24 1 L3 Inductor, 10uH TOKO A920CY-100M

25 2 Q1,Q2 Mosfet N-Chan. Dual Fairchild FDS6990A

26 2 R1,R13 Resistor, LRC 0.010 0.25W 1% IRC LRF1206-01-R010-F

27 3 R3,R9,R14 Resistor, Chip 1M 0.06W 5% AAC CR16-105JM

28 2 R4,R10 Resistor, Chip 20K 0.06W 1% AAC CR16-2002FM

29 1 R5 Resistor, Chip 105K 0.06W 1% AAC CR16-1053FM

30 6 R6,R17-R21 Resistor, Chip 10 0.06W 5% AAC CR16-100JM

31 1 R7 Resistor, Chip 15K 0.06W 5% AAC CR16-153JM

32 1 R8 Resistor, Chip 6.8K 0.06W 5% AAC CR16-682JM

33 1 R11 Resistor, Chip 63.4K 0.06W 1% AAC CR16-6342FM

34 1 R12 Resistor, Chip 10.2K 0.06W 1% AAC CR16-1022FM

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Linear Technology Corporation

LTC1876CG

Bill Of Material

Demo Bd. #324A

6/16/2005

12:09 PM

Item Qty Reference Part Description Manufacture / Part #

35 1 R15 Resistor, Chip 86.6K 0.06W 1% AAC CR16-8662FM

36 1 R16 Resistor, Chip 100K 0.06W 5% AAC CR16-104JM

37 11 TP1-TP11 Turret, Testpoint Mill Max 2501-2

38 1 U1 I.C., LTC1876CG Linear Tech. Corp. LTC1876CG

39 4 Stand-Off Nylon-Hex 4-40 1/4" Keystone 1902A

40 4 Screw,#4-40 1/4" Any

41 1 PRINTED CIRCUIT BOARDS DEMO BOARD DC324A

42 1 STENCIL STENCIL DC324A

Note:please return empty reels.

Thanks.

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