Linear Technology LTC3618EUF Quick setup guide

1
dc1726f
DEMO MANUAL DC1726
DESCRIPTION
LTC3618EUF
Dual ±3A Synchronous Buck
Regulator for DDR Termination
Demonstration circuit 1726 is a dual high efficiency
monolithic step-down (buck) DC/DC switching regulator
designed for double-data-rate (DDR) memory termina-
tion in computer systems. The VDDQ output is capable
of sourcing and sinking up to 3A with output voltages of
1.5V, 1.8V, 2.5V plus an optional voltage, selected using
jumpers. The VTT output can also source and sink up
to 3A with an output voltage equal to half of the VDDQ
voltage, half of the input voltage or half of an externally
applied voltage, selected using a jumper. An additional low
current output (VTTR) equal to the VTT voltage capable of
sourcing and sinking up to 10mA is included. Input voltage
range is from 2.25V to 5.5V with overvoltage protection
for transients exceeding 6.5V. Switching frequency is set
to 1MHz although it can be programmed up to 4MHz and
can be synchronized to an external clock for noise sensi-
tive applications.
Jumpers are included for selecting either internal or exter-
nal compensation and jumpers for low quiescent current
shutdown for each regulator. Other jumpers allow select-
ing internal or external soft-start, selecting the switching
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
phase between the two regulators and selecting external
frequency synchronizing, and forced continuous or pulse
skipping modes of operation for the VDDQ regulator only.
Terminals are provided for connecting an input supply,
output loads and voltmeters. Other terminals include
external sync input, external reference input, external
tracking input, and separate power good outputs that
pull low at start-up and when the VDDQ or VTT output is
outside a voltage window.
TheLTC
®
3618 used onthisboardishousedina24-pin4mm
×4mm thermally enhanced QFN package. The LTC3618
is also available in a 24-pin TSSOP package.
The LTC3618 data sheet gives a complete description of
the part, operation and application information and should
be read in conjunction with this quick start guide.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETERS CONDITION TYPICAL VALUE
Input Voltage Range (VIN) 2.25V to 5.5V
VDDQ Output Voltages (1.5V, 1.8V, 2.5V) VIN = 3.3V ±2.5%
VTTR Output Voltage VIN = 3.3V VDDQIN • 0.5 ±2%
VTT Output Voltage VIN = 3.3V VTTR ±6mV
Load Regulation (Each Regulator) VIN = 3.3V, 0 to 3A Load 5mV
Maximum Output Current (Each Regulator) VIN = 3.3V ±3A
Switching Frequency 1MHz ±20%
Output Voltage Ripple VIN = 3.3V, 0 to 3A Load 10mVP-P
Efficiency VIN = 3.3V, VDDQ = 1.8V, 2A Load 88%
Efficiency VIN = 3.3V, VTT = 900mV, 2A Load 80.5%

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DEMO MANUAL DC1726
QUICK START PROCEDURE
Figure 1.
Demonstration circuit 1726 allows the user to quickly
evaluate the performance of the LTC3618. Refer to Figure2
for proper measurement equipment setup and follow the
procedure below
1. Place jumpers in the following positions.
JP1 VOUT 1 Select 1.5V
JP5 Track/SS INT SS
JP6 PHASE 180°
JP8 MODE FCM
JP9 COMP 1 INT
JP10 COMP 2 INT
JP11 RUN 1 ON
JP12 RUN 2 ON
JP13 VDDQIN VDDQ
2. With the input power supply turned down and switched
off, connect the supply and digital voltmeters as shown
in Figure 2.
3. Switch on the input supply and adjust for approximately
3.3V on VIN.
4. Verify that the VDDQ output voltage is within the lim-
its shown in the table on page 1 for each of the three
output voltages as selected by JP1, JP2 and JP2. Note:
moving the jumper to JP3 sets VDDQ to the internal
reference voltage of 600mV. Other output voltages can
be programmed by selecting a suitable resistor for R9.
5. To verify VDDQ output voltage tracking. Move JP5 to the
TRACK position (upper) and remove all VOUT1 SELECT
jumpers. Apply an external reference voltage between
100mV and 600mV to TRACK1 terminal. Verify that the
VDDQ output is within ±11mV of the external reference
voltage.
6. Move JP5 to the INT SS position (lower) and place
a jumper on JP2 (1.8V). Verify that the VTTR output
voltage is equal to VDDQ • 0.5 ±2%. Additional VDDQ
voltages can be selected using JP1 or JP3.
7. Verify that the VTT output voltage is equal to the VTTR
voltage±6mV. The error voltage canbe read differentially
by placing the meter leads between the VTTR and VTT
terminals
8. Toevaluate sourcingcurrentfrom VDDQ or VTT outputs,
connect a suitable 10W load in series with an ammeter
between each output terminal and ground. Resistor.
See Figure 2 for resistor connections and resistor value
equation. Verify that the output voltages still meet the
specifications shown in the Performance Summary
section.
9. To evaluate sinking current into the VTT output, connect
a suitable 10W load resistor in series with an ammeter
between the VTT output and the VIN terminals. Verify
that the output voltages meet the specifications in the
Performance Summary section.
The many jumpers on this board allow the user to evaluate
the various features of the LTC3618. Jumpers are used to
select VDDQ output voltages, switch phasing, soft-start,
tracking, on/off, operating mode and compensation. Refer
to the data sheet for information on these functions.
Extra pads are located on the top and bottom of the board
foradding additional input and output capacitors ifdesired.
NOTE. When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the VIN or
VOUT and GND terminals. See Figure 1 for proper scope
probe technique.

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dc1726f
DEMO MANUAL DC1726
QUICK START PROCEDURE
Figure 2. Proper Measurement Equipment Setup
Figure 3. Jumper and Terminal Descriptions
Figure 4. Simplified Block Diagram of Demo Board Showing Output Voltages and Tolerances
5V @ 5A
Input Power Supply
(set to 3.3V)
+
-
V
V
V
VTTR
Output
+
-
A+
-
VDDQ Output
V
+
-
+
-
GND
VTT
Output
+
-
Connection for VTT Sinking Current
Sourcing
R
Rsourcing = –––––
VTT
ILOAD
VIN - VTT
ILOAD
Rsinking = ––––––––
10W Load
Resistor
VTTR Output
VTT ON/OFF
VTT Power Good
VDDQ Vout Select
VDDQ ON/OFF
VDDQ Power Good
VTT COMP
VDDQ COMP
Ext Sync Input
PHASE Select
Ext REF Input
GND
GND
Tracking Input MODE Select
VTT Output
+VIN
GND
GND
VDDQ Output
GND
VDDQ
Regulator
±3A
1%
VDDQ
Output
600mV, ±1.3% Ref
FB1TRACK
/SS
TRACK
Input
EXT
REF
Input
VTTR
±10mA
VTT
Regulator
±3A
JP13
SVIN
VDDQIN
R
R
VDDQ
Program
VDDQ
VTTR
Output
VTT
Output
9775RXWSXW 9''4±2%
VTT output = VTTR ±6mV
VDDQ output = VTRACK ±11mV
P9WRP9
VDDQ output = programmed voltage ±

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DEMO MANUAL DC1726
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C3 CAP., X7R, 0.01μF, 50V, 20% 0603 AVX, 06035C103MAT2A
2 4 CIN1, CIN2, CIN3, CIN4 CAP., X7R, 22μF, 6.3V, 20% 1206 AVX, 12066C226MAT2A
3 2 COUT1, COUT2 CAP., X5R, 47μF, 6.3V, 20% 1210 AVX, 12106D476MAT2A
4 2 L1, L2 INDUCTOR, 1μH COILCRAFT, XFL4020-102MEB
5 1 RT RES., CHIP, 402k, 1/16W, 5% 0603 VISHAY, CRCW0603402KFKEA
6 1 R1 RES., CHIP, 845k, 1/16W, 1% 0603 VISHAY, CRCW0603845KFKEA
7 1 R3 RES., CHIP, 562k, 1/16W, 1% 0603 VISHAY, CRCW0603562KFKEA
8 1 U1 IC., LTC3618EUF UF-24 LINEAR TECH., LTC3618EUF#PBF
Additional Demo Board Circuit Components
1 3 C1, C2, CFFW1 CAP., C0G, 10pF, 25V, 20% 0603 AVX, 06033A100MAT2A
2 1 C4 CAP., X7R, 0.1μF, 50V, 20% 0603 AVX, 06035C104MAT2A
3 1 CIN6 CAP., TANT., 100μF 10V, 20% 7343 AVX, TPSW107M010Y0150
4 0 COUT5, COUT6, CIN5 (OPT) CAP., 7343
5 1 CITH1 CAP., NPO, 470pF, 25V, 20% 0805 AVX, 08053A471MAT2A
6 1 CITH2 CAP., NPO, 680pF, 25V, 20% 0805 AVX, 08053A681MAT2A
7 2 COUT3, COUT4 CAP., X7R, 10μF, 6.3V, 20% 0805 AVX, 08056C106MAT2A
8 0 COUT7, COUT8 (OPT) CAP., 1210
9 1 CSS1 CAP., X7R, 0.01μF, 50V, 20% 0603 AVX, 06035C103MAT2A
10 1 CFILT CAP., X7R, 1μF, 10V, 20% 0603 AVX, 0603ZD105MAT2A
11 1 RFILT RES., CHIP, 24Ω, 1/16W, 5% 0603 VISHAY, CRCW060324R0JNEA
12 1 RITH1 RES., CHIP, 15.4k, 1/16W, 1% 0805 VISHAY, CRCW080515K4FKEA
13 1 RITH2 RES., CHIP, 10k, 1/16W, 1% 0805 VISHAY, CRCW080510K0FKEA
14 1 RTR1 RES., CHIP, 100k, 1/16W, 1% 0603 VISHAY, CRCW0603100KFKEA
15 2 RPG1, RPG2 RES., CHIP, 100k, 1/16W, 5% 0603 VISHAY, CRCW0603100KJNEA
16 1 RSS1 RES., CHIP, 4.7M, 1/16W, 5% 0603 VISHAY, CRCW06034M70JNEA
17 0 RTR3, R9, RM1, RM2 (OPT) RES., 0603
18 1 R5 RES., CHIP, 422k, 1/16W, 1% 0603 VISHAY, CRCW0603422KFKEA
19 1 R7 RES., CHIP, 267k, 1/16W, 1% 0603 VISHAY, CRCW0603267KFKEA
Hardware/Components (For Demo Board Only)
1 2 JP11, JP12 HEADER, 3 PIN 0.079 SINGLE ROW SAMTEC, TMM-103-02-L-S
2 4 JP5, JP6, JP8, JP13 HEADER, 2x3 PIN 0.079 DOUBLE ROW SAMTEC, TMM-103-02-L-D
3 2 JP9, JP10 HEADER, 2x2 PIN 0.079 DOUBLE ROW SAMTEC, TMM-102-02-L-D
4 4 JP1-JP4 HEADER, 2 PIN 0.079 SINGLE ROW SAMTEC, TMM-102-02-L-S
5 9 XJP1, XJP5, XJP6, XJP8-XJP13 SHUNT, .079" CENTER SAMTEC, 2SN-BK-G
6 14 E1-E14 TESTPOINT, TURRET, 0.094" pbf MILL-MAX, 2501-2-00-80-00-00-07-0
7 4 MH1-MH4 STANDOFF, NYLON, 0.25, 1/4" KEYSTONE, 8831 (SNAP ON)
PARTS LIST

5
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DEMO MANUAL DC1726
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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6
dc1726f
DEMO MANUAL DC1726
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011
LT 0811 • 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
directive 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