Linear Technology DC1480A Quick setup guide

1
dc1480af
DEMO MANUAL DC1480A
DESCRIPTION
LTC3865EUH-1
Dual 5A Synchronous Buck
Converter with Pin Selectable Outputs
Demonstration circuit 1480A is a dual output synchronous
buck DC/DC converter featuring the LTC
®
3865EUH-1. The
input voltage range is from 4.5V to 14V. The outputs are
3.3V/5A and 1.8V/5A. Each output voltage can be precisely
programmed to a preset value within 1% error with the
VID pins. The demo board uses a high density, two sided
drop-in layout. The package of LTC3865EUH-1 is a small,
low thermal impedance 5mm × 5mm 32-Lead QFN.
The light load operation mode of the converter is de-
termined with the MODE/PLLIN pin. Use JP1 jumper to
select Burst Mode
®
operation, pulse-skipping mode or
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
PARAMETER CONDITION VALUE
Input Voltage Range 4.5V to 14V
Output Voltage, VOUT1 VIN = 4.5V to 14V, IOUT1 = 0A to 5A 3.3V ±1%
Output Voltage, VOUT2 VIN = 4.5V to 14V, IOUT2 = 0A to 5A 1.8V ±1%
Maximum Output Current, IOUT1 VIN = 4.5V to 14V, VOUT1 = 3.3V 5A
Maximum Output Current, IOUT2 VIN = 4.5V to 14V, VOUT2 = 1.8V 5A
Typical Full Load Efficiency, Channel 1 VIN = 12V, VOUT1 = 3.3V, IOUT1 = 5A 91.6%
Typical Full Load Efficiency, Channel 2 VIN = 12V, VOUT2 = 1.8V, IOUT2 = 5A 86.6%
Typical Switching Frequency 500kHz
PERFORMANCE SUMMARY
forced continuous mode operation. Switching frequency
is preset at about 500kHz. This frequency can be modi-
fied by changing R5 value at the FREQ pin. The converter
can also be externally synchronized from 250kHz to
770kHz through MODE/PLLIN pin (SYNC terminal on the
board). To shut down a channel, force its RUN pin below
1.2V (Jumper: OFF). The power good output (PGOOD1
or PGOOG2 terminal) is low when that channel output
exceeds ±10% regulation window.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)

2
dc1480af
DEMO MANUAL DC1480A
QUICK START PROCEDURE
Demonstration circuit 1480A is easy to set up to evaluate
the performance of the LTC3865EUH-1. Refer to Figure 1
for the proper measurement equipment setup and follow
the procedure below:
Jumper positions:
JP1 (MODE): PS
JP2, JP3 (RUN1/RUN2): ON
1. With power off, connect the input power supply to VIN
(4.5V to 14V) and GND (input return).
2. Connect the load #1 between VOUT1 and GND (Initial
load: no load); connect the load #2 between VOUT2 and
GND (Initial load: no load).
3. Connect the DVMs to the input and outputs.
4. Turn on the input power supply and check for the proper
output voltages. With current VID pin setting, VOUT1
should be 3.3V ±1%; VOUT2 should be 1.8V ±1%.
5. Once the proper output voltages are established,
adjust the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
parameters.
6. If necessary, change the resistor options on VID pins
for other output voltages according to Table 1.
Note 1. When measuring the output or input voltage ripple, do not use the
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.
Note 2. To accurately measure the output voltages and efficiency, measure
VOUT1 and VOUT2 on output capacitors COUT2 and COUT4 directly.
OUTPUT VOLTAGE PROGRAMMING
The output voltages of both channels can be programmed
to preset values. There are two VID pins for each channel:
VID11, VID12 for VOUT1, and VID21, VID22 for VOUT2. See
Table 1 for details.
Table 1. Output Voltage Programming
VID11/VID21 VID12/VID22 VOUT1/VOUT2 (V)
INTVCC INTVCC 5V (VIN ≥ 5V)
INTVCC FLOAT 3.3V
INTVCC GND 2.5V
FLOAT INTVCC 1.8V
FLOAT FLOAT 0.6 or External Divider
FLOAT GND 1.5V
GND INTVCC 1.2V
GND FLOAT 1V
GND GND 1.1V

3
dc1480af
DEMO MANUAL DC1480A
Rail Tracking
Demonstration circuit 1480A is configured for independent
turn-on of VOUT1 and VOUT2. The ramp rate for VOUT1 is
determined by the TRK/SS1 cap at C6 and the ramp rate
for VOUT2 is determined by the TRK/SS2 capacitor at
C14. This board can be modified on the bench to allow
VOUT1 to track an external signal. It can also be modified
to allow VOUT2 to track VOUT1 or to allow VOUT2 to track
an external signal. Tables 2 and 3 cover the rail tracking
options for each rail.
Table 2. VOUT1 Tracking Options (3.3V)
TRACK1 DIVIDER TRK/SS1 CAPACITOR
CONFIGURATION R7 R9 C6
Soft-Start without Tracking (Original Board) 0Ω Not Stuffed 0.1µF
External Coincident Tracking 45.3kΩ 10kΩ Not Stuffed
Table 3. VOUT2 Tracking Options (1.8V)
TRACK2 DIVIDER TRK/SS2 CAPACITOR
CONFIGURATION R15 R14 R17 C14
Soft-Start without Tracking (Original Board) 0Ω Not Stuffed Not Stuffed 0.1µF
Coincident Tracking to VOUT1 (3.3V) 0Ω 20kΩ 10kΩ Not Stuffed
External Coincident Tracking 20kΩ Not Stuffed 10kΩ Not Stuffed
Figure 1. Proper Measurement Equipment Setup
QUICK START PROCEDURE
+
–
V
+
–
+
–
VIN
SUPPLY
IIN
A
+
IOUT1
A
IOUT2
VIN
A
VOUT1
LOAD
VOUT2
LOAD
VOUT2
VOUT1
+
–
V
+
–
V
+
+
+

4
dc1480af
DEMO MANUAL DC1480A
Figure 2. Measuring Output Voltage Ripple
COUT
VOUT
+ –
GND 1480a F02
QUICK START PROCEDURE
Figure 3. Efficiency vs Load Current (VIN = 12V,
VOUT1 = 3.3V, 500kHz)
Figure 4. Efficiency vs Load Current (VIN = 12V,
VOUT2 = 1.8V, 500kHz)
LOAD CURRENT (A)
0.01
0
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
100
0.1 1 10
1480a F03
VIN = 12V
VOUT = 3.3V
ILOAD = 5A MAX
CCM
PS
BM
LOAD CURRENT (A)
0.01
0
10
20
30
40
50
60
70
80
90
EFFICIENCY (%)
100
0.1 1 10
1480a F04
VIN = 12V
VOUT = 1.8V
ILOAD = 5A MAX
CCM
PS
BM

5
dc1480af
DEMO MANUAL DC1480A
PARTS LIST
ITEM QUANTITY REFERENCE-DESCRIPTION DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 CIN1 Cap, Alum 39µF 16V 20% OSCON-C6 OSCON 16SVP39M
2 2 CIN3, CIN2 Cap, X5R 10µF 16V 20% 1206 Taiyo Yuden EMK316BJ106ML
3 2 COUT1, COUT3 Cap, X5R 10µF 6.3V 10% 1206 Taiyo Yuden JMK316BJ106KL-T
4 2 COUT2, COUT4 Cap, POSCAP 220µF 4V 20% Sanyo 4TPE220MF
5 4 C1, C5, C10, C15 Cap, X7R 1000pF 50V 10% 0603 AVX 06035C102KAT1A
6 5 C3, C6, C7, C12, C14 Cap, X7R 0.1µF 25V 10% 0603 AVX 06033C104KAT2A
7 2 C4,C13 Cap, X5R 1µF 6.3V 10% 0603 Taiyo Yuden JMK107BJ105KA-T
8 1 C8 Cap, X5R 4.7µF 16V 20% 0805 Taiyo Yuden EMK212BJ475MG
9 1 C9 Cap, NPO 220pF 25V 10% 0603 AVX 06033A221KAT2A
10 1C11 Cap, X7R 470pF 50V 5% 0603 AVX 06035C471JAT1A
11 1C16 Cap, X5R 1µF 16V 20% 0805 Taiyo Yuden EMK212BJ105MG
12 2D1, D2 Schottky Diode, 30V CMDSH-3 Central Semi. CMDSH-3TR
13 2L1, L2 Inductor, 2.2µH IHLP-2525CZ-01 Vishay IHLP-2525CZERM01 2R2uH
14 2 Q2, Q1 Dual MOSFET N-Channel, 30V Siliconix Vishay Si4816BDY
15 2 RS1, RS2 Res, LRC 0.006 0.25W 5% 1206 IRC LRF1206-01-R006-J
16 3 R1, R33, R38 Res, Chip 10k 0.06W 5% 0603 Vishay CRCW060310K0JNEA
17 7 R2, R6, R7, R11, R15, R16, R21 Res, Chip 0Ω 1/16W 1A 0603 Vishay CRCW06030000Z0EA
18 4 R3, R4, R18, R20 Res, Chip 100 0.06W 5% 0603 Vishay CRCW0603100RJNEA
19 1R5 Res, Chip 162k 0.06W 1% 0603 Vishay CRCW0603162KFKEA
20 1R8 Res, Chip 2.2 0.06W 5% 0603 Vishay CRCW06032R20JNEA
21 1R10 Res, Chip 24.9k 0.06W 1% 0603 Vishay CRCW060324K9FKEA
22 1R13 Res, Chip 15k 0.06W 5% 0603 Vishay CRCW060315K0JNEA
23 2R19, R22 Res, Chip 100k 0.06W 5% 0603 Vishay CRCW0603100KJNEA
24 1U1 IC, Voltage Regulator QFN (32) (UH) 5mm × 5mm Linear Technology LTC3865EUH-1
Additional Circuit Components
1 2 CIN5,CIN4 Cap, 0805
2 1 C2 Cap, 0603
3 2 Q3, Q4 (SyncFet) N-Channel, Dual Fairchild FDS6982AS
4 20 R9, R12, R14, R17, R23, R24
R25, R26, R27, R28, R29, R30, R31
R32, R34, R35, R36, R37, R39, R40
Res, 0603
Hardware Demo Board Only
1 17 E1, E2, E3 ,E4, E5, E6, E7, E8, E9, E10 Turret, Testpoint 0.094” Mill Max 2501-2-00-80-00-00-07-0
2 E11, E12, E13, E14, E15, E16, E17
3 1 JP1 Headers, 4 Pins 2mm Ctrs. Samtec TMM-104-02-L-S
4 2 JP2, JP3 Headers, 3 Pins 2mm Ctrs. Samtec TMM-103-02-L-S
5 3 XJP1, XJP2, XJP3 Shunt, 2mm Ctrs. Samtec 2SN-BK-G
6 4 MH1 to MH4 Stand-Off, Nylon 0.25” Tall Keystone, 8831(Snap On)
7 1 FAB, 1480A_ Rev0 Demo Circuit 1480A
8 2 Stencil 1480A Stencil #1480A

6
dc1480af
DEMO MANUAL DC1480A
SCHEMATIC DIAGRAM

7
dc1480af
DEMO MANUAL DC1480A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, noresponsibility is assumed for its use. Linear Technology Corporation makes no representation
that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM

8
dc1480af
DEMO MANUAL DC1480A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2010
LT 1010 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union direc-
tive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation