DC1185B-A Datasheet DC1185B-A | P1-P3

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

DESCRIPTION

LTC3850EUF

Dual Phase/Dual Output

Synchronous Buck Converter

Demonstration circuit 1185 is a dual phase/dual output

synchronous buck converter featuring the LTC3850EUF.

The demo board comes in two versions. The output volt

ages for version DC1185B-A are 2.0V/10A and 1.8V/10A.

The output voltages for version DC1185B-B are 1.5V/15A

and 1.2V/15A. The input voltage range is 6.5V to 14V for

both versions. For applications that have a 5V ±0.5V input,

the board has an optional resistor to tie the INTVCC pin

to the VIN pin.

The demo board uses a high density, 2-sided drop-in layout.

The power components excluding the bulk output and input

capacitors, fit within a 1.35" × 0.75" area on the top layer.

The control circuit resides in a 0.60" × 0.75" area on the

bottom layer. The package style for the LTC3850EUF is a

4mm × 4mm 28-lead QFN with an exposed ground pad.

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

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

owners.

Note: Q1-Q4 MOSFETs changed on September 10, 2013.

See Schematic Diagram.

PERFORMANCE SUMMARY

The main features of the board include an internal 5V linear

regulator for bias, RUN pins for each output, an EXTVCC

pin and a PGOOD signal. The board can be configured

for either CCM (original setting), Burst Mode

, or pulse-

skipping operation with the MODE jumper. The board

also has optional resistors for single output/dual phase

operation, rail tracking, DCR sensing and synchronization

to an external clock.

Design files for this circuit board are available at

http://www.linear.com/demo

Specifications are at T

= 25°C

PARAMETER CONDITION VALUE

Minimum Input Voltage 6.5V

Maximum Input Voltage 14V

Version DC1185B-A

Output Voltage V

OUT1

= 0A to 10A 2.0V ±2%

Output Voltage V

OUT2

= 0A to 10A 1.8V ±2%

Nominal Switching Frequency 500kHz

Full-Load Efficiency

(See Figure 3 for Efficiency Curves)

OUT1

= 2.0V, I

OUT1

= 10A, V

= 12V

OUT2

= 1.8V, I

OUT2

= 10A, V

= 12V

90.2%

89.5%

Version DC1185B-B

Output Voltage V

OUT1

= 0A to 15A 1.5V ±2%

Output Voltage V

OUT2

= 0A to 15A 1.2V ±2%

Nominal Switching Frequency 400kHz

Full-Load Efficiency

(See Figure 4 for Efficiency Curves)

OUT1

= 1.5V, I

OUT1

= 15A, V

= 12V

OUT2

= 1.2V, I

OUT2

= 15A, V

= 12V

88.1%

86.5%

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

QUICK START PROCEDURE

Demonstration circuit 1185 is easy to set up to evaluate

the performance of the LTC3850EUF. Refer to Figure 1

for the proper measurement equipment setup and follow

the procedure below:

Note: When measuring the output or input voltage ripple,

care must be taken to avoid a long ground lead on the

oscilloscope probe. See Figure 2 for the proper scope

probe technique. Short, stiff leads need to be soldered

to the (+) and (–) terminals of an output capacitor. The

probe’s ground ring needs to touch the (–) lead and the

probe tip needs to touch the (+) lead.

Place jumpers in the following positions:

JP1 RUN1 ON

JP2 RUN2 ON

JP3 MODE CCM

With power off, connect the input power supply to VIN

and GND.

Turn on the power at the input.

Note: Make sure that the input voltage does not exceed 15V.

Check for the proper output voltages.

Version DC1158B-A:

OUT1

= 1.960V to 2.040V

OUT2

= 1.764V to 1.836V

Version DC1158B-B:

OUT1

= 1.470V to 1.530V

OUT2

= 1.176V to 1.224V

Once the proper output voltages are established, adjust

the loads within the operating range and observe the

output voltage regulation, ripple voltage, efficiency and

other parameters.

Note:

Do not apply load across the VOSn+ and VOSn–

turrets. These turrets are only intended to Kelvin sense

the output voltage across COUT1 and COUT4. Heavy load

currents may damage the output voltage sense traces.

Figure 1. Proper Measurement Equipment Setup

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

QUICK START PROCEDURE

SINGLE OUTPUT/DUAL PHASE OPERATION

VOU T

GND

COUT

Figure 2. Measuring Output Voltage Ripple

A single output/dual phase converter may be preferred

for high output current applications. The benefits of

single output/dual phase operation is lower ripple current

through the input and output capacitors, improved load

step response and simplified thermal design. To implement

single output/dual phase operation, make the following

modifications:

1. Tie VOUT1 to VOUT2 by tying together the exposed

copper pads near J3 and J5 at the edge of the board.

Use a piece of heavy copper foil.

2. Tie ITH1 to ITH2 by stuffing 0Ω at R49.

3. Tie VFB1 to VFB2 by stuffing 0Ω at R50.

4. Tie TRK/SS1 to TRK/SS2 by stuffing 0Ω at R52.

5. Tie RUN1 to RUN2 by stuffing 0Ω at R55.

6. Remove the redundant ITH compensation network and

VFB divider.

LOAD CURRENT (A)

EFFICIENCY (%)

2.0V

1.8V

4 6 8

10 12

QTOP: RJK030DPB

QBOTTOM: RJK0330DPB

L: TOKO FDU0650-R56M = P3

0.56µH, DCR = 2.45mΩ, 3.2mΩ MAX

SENSE

= 3mΩ

LOAD CURRENT (A)

EFFICIENCY (%)

1.2V

6 9 12

15 18

QTOP: RJK030DPB

QBOTTOM: RJK0330DPB

L: VITEC 59PR9875

0.4µH, DCR = 0.47mΩ ±10%

SENSE

= 2mΩ

1.5V

2.0V/10A and 1.8V/10A Efficiency at V

= 12V and f

= 500kHz 1.5V/15A and 1.2V/15A Efficiency at V

= 12V and f

= 400kHz

Figure 3. Efficiency Curves for the DC1185B-A Figure 4. Efficiency Curves for the DC1185B-B

P1-P3 P4-P6 P7-P9 P10-P10

DC1185B-A

Mfr. #:

Buy DC1185B-A

Manufacturer:

Analog Devices Inc.

Description:

Power Management IC Development Tools LTC3850EUF Demo Board - 4.5V ? VIN ? 14V

Lifecycle:

New from this manufacturer.

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DC1185B-A