Linear Technology DC1839A Quick setup guide

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dc1839af
DEMO MANUAL DC1839A
DESCRIPTION
LTC3634
15V Dual 3A Monolithic
Step-Down Regulator Board
for DDR Power
Demonstration circuit 1839A is a dual output regulator
focused specifically for DDR memory power applications.
It’s builtbasedonthe LTC3634,a highvoltage dualchannel,
controlled on-time monolithic synchronousbuck regulator.
TheDC1839A hasan inputvoltage rangeof 3.6Vto 15V.The
output voltage of the first channel, VDDQ, of the DC1839A
has three fixed voltage settings; 1.5V, 1.8V, and 2.5V, and
is capable of delivering up to 3A of output current. The
second channel, VTT, is set to regulate to half the voltage
on the VDDQIN pin, which can be either the channel1
output or an external reference voltage. It can source or
sink a maximum of 3A. The LTC3634 also provides a 10mA
buffered output of half VDDQIN – VTTR, which is used to
providethe reference voltage needed for DDR applications.
With the use of a timing resistor, the DC1839A can have its
operating frequency programmed from 500kHz to 4MHz,
or the DC1839A can be easily synchronized to an external
clock, due to an internal phase-locked loop. The DC1839A
VDDQ outputcan operatein eitherBurst Mode
®
operation or
L, LT, LTC, LTM, μModule, 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.
PERFORMANCE SUMMARY
forced continuous mode. In Burst Mode operation, which
is the preferred mode of low load current operation, the DC
supply current is typically only 1.3mA (both channels) at
no load (sleep mode), and less than 15μA in shutdown. In
Burst Mode operation or continuous mode operation, the
DC1839A is a very efficient circuit at high load currents:
over 80% for either channel. The LTC3634 is also capable
of in-phase or 180° out-of-phase operation, and to allow
its output to track an external voltage, either coincidentally
or ratiometrically. The LTC3634 comes in a 28-pin QFN or
leaded package, which each having an exposed pad on
the bottom side of the IC for better thermal performance.
All of these features make the DC1839A an ideal circuit
for powering DDR memory applications.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETER CONDITIONS VALUE
Minimum Input Voltage 3.6V
Maximum Input Voltage 15V
Output Voltage VOUT1 – VDDQ VIN = 3.6V to 15V, IOUT1 = 0A to 3A 1.5V ±2% (1.47V to 1.53V)
1.8V ±2% (1.764V to 1.836V)
2.5V ±2% (2.45V to 2.55V)
Typical Output Ripple VDDQ VIN = 12V, IOUT1 = 3A (20MHz BW) < 20mVP-P
Output Voltage VOUT2 – VTT VIN = 3.6V to 15V, IOUT2 = 0A to ±3A VOUT1 = 1.5V 0.75V ±3% (0.7275V to 0.7725V)
VOUT1 = 1.8V 0.9V ±3% (0.873V to 0.927V)
VOUT1 = 2.5V 1.25V ±3% (1.2125V to 1.2875V)
Typical Output Ripple VTT VIN = 12V, IOUT2 = ±3A (20MHz BW) < 20mVP-P
Nominal Switching Frequencies RT = 324k 1MHz
Burst Mode-to-CCM transition Channel 1: VIN = 12V, VOUT1 = 1.8V, fSW = 1 MHz IOUT1 = 1.6A
INTVCC 3.3V
VTTR VDDQIN = 2.5V 1.25V

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dc1839af
DEMO MANUAL DC1839A
QUICK START PROCEDURE
The DC1839A is easy to set up to evaluate the performance
of the LTC3634. For a proper measurement equipment
configuration, set up the circuit according to the diagram
in Figure 1.
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 the proper scope probe
technique in Figure 2.
Please follow the procedure outlined below for proper
operation.
1. Connect the input power supply to the VIN and GND
terminals. Connect the loads between the VOUT and GND
terminals. Refer to Figure 1 for the proper measurement
equipment setup.
Before proceeding to operation, insert jumper shunts
XJP1 and XJP2 into the OFF positions of headers JP1
and JP2, shunt XJP3 into the forced continuous mode
(FCM) position of MODE header JP3, shunt XJP4 into
the 180° (out-of-phase) position of PHASE header JP4,
shunt XJP5 into the soft-start positions of TRACK/SS
header JP5, and shunt XJP6 into the VOUT1 voltage
options of choice of header JP6: 1.2V, 1.5V, or 1.8V.
2. Apply 5V at VIN. Measure both VOUTs; they should read
0V. If desired, one can measure the shutdown supply
current at this point. The supply current should be less
than 30μA in shutdown.
3. Turn on VOUT1, VDDQ, and VOUT2, VTT, by shifting shunts
XJP1 and XJP2 from the OFF positions to the ON posi-
tions. Both output voltages should be within a tolerance
of ±1%.
4. Vary the input voltage from 3.6V to 15V, the channel 1
load current from 0 to 3A, and the channel 2 load cur-
rent from 0 to ±3A (The VTT channel sinks as well as
sources current. An easy way to test this capability is
shown in the test set-up diagram; connect a variable
resistor from VIN to VOUT, along with an ampmeter. The
current will be VIN minus VOUT divided by the variable
resistor value). VDDQ output voltage tolerance should
be within ±2%, whereas the output voltage tolerance
of VTT should be within ±3%.
5. Set the load current of both outputs to 3A and the input
voltage to 12V, then measure each output ripple voltage
(refer to Figure 2 for proper measurement technique);
they should each measure less than 20mVAC. Also,
observe the voltage waveform at either switch node
(pins 16 and 17 for channel 1, and 23 and 24 for chan-
nel 2) of each regulator. (Both switch node waveforms
should be rectangular in shape and 180°out-of-phase
with each other). The switching frequencies should be
between 800kHz and 1.2MHz (T = 1.25μs and 0.833μs).
6. Withthe board under proper operation, observethe load
regulation, efficiency, in-phase operation (by changing
jumper XJP4 to the 90° position), or BurstMode op-
eration (by changing jumper XJP3 to the Burst Mode
position).
7. (Optional) Moving the zero ohm resistor at RVDDQ,
inserting it into RDDQIN, and applying a voltage to turret
VDDQIN allows channel2 output voltage (VTTR) to be
adjusted to any desired voltage (to one-half the voltage
at VDDQIN).
When finished, insert shunts XJP1 and XJP2 to the OFF
position(s) and disconnect the power.
Warning: If the power for the demo board is carried in
long leads, the input voltage at the part could ring, which
could affect the operation of the circuit or even exceed
the maximum voltage rating of the IC. To eliminate the
ringing, a small Poscap capacitor (for instance, AVX part
number TPSY226M035R0200) is inserted on the pads
between the input power and return terminals on the bot-
tom of the demo board. The (greater) ESR of the Poscap
will dampen the (possible) ringing voltage due to the use
of long input leads. On a normal, typical PCB, with short
traces, this capacitor is not needed.

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DEMO MANUAL DC1839A
VS
VARIABLE
RESISTOR
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup

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DEMO MANUAL DC1839A
QUICK START PROCEDURE
Figure 3. LTC3634 DC1839A Efficiency
Figure 2. Measuring Input or Output Ripple
GND VIN
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
10
90
70
50
30
80
60
40
20
0
dc1839a F03
3.01.5 2.51.0 2.00.5
VIN = 12V
VDDQ = 2.5V
VTT = 1.25V
fSW = 1MHz
Burst Mode OPERATION
L1 = 1μH
L2 = 0.47μH
VISHAY 2020BZ

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dc1839af
DEMO MANUAL DC1839A
QUICK START PROCEDURE
Figure 4. VDDQ Load Step Response Figure 5. VTT Load Step Response
Figure 6. LTC3634 DC1839A Start-Up with Soft-Start
VIN = 12V
VDDQ = 1.8V
3A LOAD STEP (0A TO 3A)
FORCED CONTINUOUS MODE
fSW = 1MHz
EXTERNAL COMPENSATION: RITH1 = 18.2k, CITH1 = 680pF
TRACE 3: OUTPUT VOLTAGE (50mV/DIV AC)
TRACE 4: OUTPUT CURRENT (1A/DIV)
dc1839a F04
VIN = 12V
VTT = 0.9V
±3A LOAD STEP (–3A TO 3A)
FORCED CONTINUOUS MODE
fSW = 1MHz
EXTERNAL COMPENSATION: RITH2 = 15k, CITH2 = 1000pF
TRACE 3: OUTPUT VOLTAGE (50mV/DIV AC)
TRACE 4: OUTPUT CURRENT (2A/DIV)
dc1839a F05
VIN = 12V
VDDQ = 1.8V
VTT = 0.9V
3A LOAD (EACH)
FORCED CONTINUOUS MODE
fSW = 1MHz
CSS = 4700pF
TRACE 1: VDDQ OUTPUT (500mV/DIV)
TRACE 2: VTT OUTPUT (500mV/DIV)
TRACE 3: VTTR OUTPUT (1V/DIV)
TRACE 4: VRUN VOLTAGE (2V/DIV)
dc1839a F06

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DEMO MANUAL DC1839A
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 CBST1, CBST2 CAP, 0603, 0.1μF, 10%, 50V, X7R NIC NMC0603X7R104K50TRPF
2 1 CFFW1 CAP, 0402, 10pF, 5%, 25V, NPO NIC NMC0402NPO100J25TRPF
3 2 CIN1, CIN2 CAP, 1210, 47μF, 20%, 16V, X5R TAIYO YUDEN EMK325BJ476MM-T
4 1 CITH1 CAP, 0402, 680pF, 10%, 25V, X7R AVX 04023C681KAT2A
5 1 CITH2 CAP, 0402, 1000pF, 10%, 25V, X7R AVX 04023C102KAT2A
6 5 COUT1-COUT4, COUT6 CAP, 1812, 100μF, 20%, 6.3V, X5R TDK C4532X5R0J107M
7 1 CTTR CAP, 0603, 10nF, 10%, 16V, X7R AVX 0603YC103KAT2A
8 1 CVCC CAP, 0603, 1μF, 10%, 16V, X5R NIC NMC0603X5R105K16TRPF
9 1 L1 IND, 1.0μH VISHAY IHLP2020BZER1R0M01
10 1 L2 IND, 0.47μH VISHAY IHLP2020BZERR47M01
11 1 RFB1 RES, 0402, 34.8kΩ, 1%, 1/16W NIC NRC04F3482TRF
12 1 RITH1 RES, 0402, 18.2kΩ, 1%, 1/16W VISHAY CRCW040218K2FKED
13 1 RITH2 RES, 0402, 15kΩ, 1%, 1/16W VISHAY CRCW040215K0FKED
14 1 RT RES, 0402, 324kΩ, 1%, 1/16W NIC NRC04F3243TRF
15 1 RVDDQ RES, 0402, 0Ω, JUMPER NIC NRC04Z0TRF
16 1 R3 RES, 0402, 11kΩ, 1%, 1/16W NIC NRC04F1102TRF
17 1 U1 IC, MONOLITHIC SYNCHRONOUS STEP-DOWN REGULATOR LINEAR TECH LTC3634EFE
Additional Demo Board Circuit Components
1 0 CC1, CC2 OPTION CAP, 0402, 10pF, 5%, 25V, NPO NIC NMC0402NPO100J25TRPF
2 0 CDDQIN OPTION CAP, 0805, 10μF, 10%, 6.3V, X5R OPTION NIC NMC0805X5R106K6.3TRPLP3KF
3 0 CIN3, CIN4 OPTION CAP, 1210, 47μF, 20%, 16V, X5R TAIYO YUDEN EMK325BJ476MM-T
4 2 CIN5, CIN6 CAP, TANT. 7343, 22μF, 20%, 35V AVX TPSY226M035R0200
5 0 COUT5, COUT8 OPTION CAP, 1812, 100μF, 20%, 6.3V, X5R TDK C4532X5R0J107M OPTION
6 2 COUT7, COUT9 CAP, 0805, 10μF, 10%, 6.3V, X5R NIC NMC0805X5R106K6.3TRPLP3KF
7 1 CTR1 CAP, 0402, 4700pF, 10%, 50V, X7R TDK C1005X7R1H472K
8 0 CTTR1 CAP, 0603, 10nF, 10%, 16V, X7R AVX 0603YC103KAT2A OPTION
9 1 CVCC1 CAP, 0603, 1μF, 10%, 16V, X5R NIC NMC0603X5R105K16TRPF
10 0 RD1, RTR2, RD2, R6, RFREQ,
RDDQIN OPTION
RES, 0402 OPTION
11 2 RPG1, RPG2 RES, 0402, 100kΩ, 5%, 1/16W NIC NRC04J104TRF
12 1 RTR1 RES, 0402, 0Ω, JUMPER NIC NRC04Z0TRF
13 2 R1, R2 RES, 0402, 1MΩ, 5%, 1/16W NIC NRC04J105TRF
14 1 R4 RES, 0402, 17.4kΩ, 1%, 1/16W NIC NRC04F1742TRF
15 1 R5 RES, 0402, 23.2kΩ, 1%, 1/16W NIC NRC04F2322TRF
16 1 R7 RES, 0402, 1kΩ, 1%, 1/16W NIC NRC04F1001TRF
Hardware/Components (For Demo Board Only)
1 17 E1-E17 TURRET MILL-MAX 2501-2-00-80-00-00-07-0
2 4 JP1, JP2, JP4, JP5 HEADER, 3-PIN, 2mm SAMTEC TMM-103-02-L-S
3 1 JP3 HEADER, 3-PIN, DBL ROW 2mm SAMTEC TMM 103-02-L-D
4 1 JP6 HEADER, 4-PIN, DBL ROW 2mm SAMTEC TMM 104-02-L-D
5 6 JP1-JP6 SHUNT, 2mm SAMTEC 2SN-BK-G
PARTS LIST

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dc1839af
DEMO MANUAL DC1839A
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.
SCHEMATIC DIAGRAM
5 5
4 4
3 3
2 2
1 1
DD C C B B A A
[1]
3.6V - 15V
10mA
NOTES: UNLESS OTHERWISE SPECIFIED
[1] CIN5 AND CIN6 ARE INSERTED ON THEDC1839A TO DAMPEN THE (POSSIBLE)
RINGING VOLTAGE DUE TO THE USE OF LONG INPUT LEADS. ON A NORMAL, TYPICAL PCB, WITH SHORT TRACES, CIN5 AND CIN6 ARE NOT NEEDED.
2. ALL RESISTOR AND CAPACITOR CASE SIZE ARE0402.
IHLP-2020BZERR47M01
3A
VISHAY
IHLP-2020BZER1R0M01
VISHAY
3A
(FORCED
CONTINUOUS MODE)
30603060
OPT
OPT
2.5V 1.8V 1.5V USER SELECT
VDDQSEL
0603 0603
[1] OPT
OPT
1
11
DUAL DDR MONOLITHIC
JW
TOM G.
N/A
LTC3634EFE
DEMO CIRCUIT 1839A
SYNCHRONOUS STEP-DOWN REGULATOR
Thursday,June30,2011
SIZE DATE:
.VER.ONCI
SHEET OF
TITLE:
APPROVALS
PCBDES.
APPENG.
TECHNOLOGY
Fax: [phone] Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGYHAS MADE ABEST EFFORTTO DESIGNA
CIRCUIT THAT MEETSCUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER,IT REMAINSTHECUSTOMER'S RESPONSIBILITYTO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTIONAND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLYAFFECTCIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGYAPPLICATIONS ENGINEERINGFOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEARTECHNOLOGY AND
SCHEMATIC
SUPPLIEDFOR USE WITHLINEAR TECHNOLOGYPARTS.
SCALE = NONE
www.linear.com
TOM G.
PRODUCTION 11-80-601
__
REVISION HISTORY
ETADNOITPIRCSED APPROVEDECO REV
INTVCC
INTVCC
VIN VIN
VIN
INTVCC INTVCC
INTVCC
VIN
INTVCC
RD2 OPT
E16 GND
+
CIN6 22uF 35V 7343
JP2
ON OFF
RUN21
3
2
CIN1 47uF 16V 1210
E10
INTVCC
E17
VIN2
JP5
TRACKSS
SS
TRACK 1
3
2
CBST2 0.1uF
R6
OPT
CVCC1
1uF
RT
324k
1%
CFFW1
10pF
R5 23.2k 1%
RTR2
OPT
RVDDQ
0
E4 VDDQ
100uF COUT8
6.3V 1812
R2
1M
RPG2 100K
CIN4 47uF 16V 1210
10uF
CDDQIN
OPT
0805
E9
TRACK1 100uF
COUT2
6.3V 1812
R3
11k
1%
100uF
COUT3
6.3V
1812
CITH1
680pF
100uF COUT4
6.3V 1812
E13 VTTR
E12
SYNC
E1
PGOOD1
L1 1.0uH
E2
VIN1
CIN2 47uF 16V 1210
CVCC
1uF
E11 VDDQIN
E8 PGOOD2
RDDQIN
OPT
RITH1
18.2k
1%
10uF
COUT9
6.3V
0805
100uF
COUT1
6.3V 1812
RFREQ
OPT
R1
1M
CITH2
1000pF
L2 0.47uH
+
CIN5 22uF
35V 7343
RITH2
15k
1%
E5 VTT
100uF COUT5
6.3V
1812
JP4
180°
90°
PHASE1
3
2
R7
1k 1%
CBST1
0.1uF
CTTR1 10nF
OPT
E14 GND
JP6
1 2
3 4
5 6
7 8
100uF
COUT6
6.3V 1812
10uF
COUT7
6.3V
0805
E7 GND
U1
LTC3634EFE
4
5 6
8
7 9
10
13
11
12
14
15
16
17
18
19
20
21
22
23
24
25
26 27 28
1
2
3
29
PGOOD1
PHMODE RUN1
RT
MODE/SYNC RUN2
SGND
VDDQIN
PGOOD2
VFB2
ITH2
VON2
SW2 SW2
VIN2
VIN2
BOOST2
VTTR
INTVCC
BOOST1
VIN1
VIN1
SW1 SW1
VON1
ITH1 TRACKSS1
VFB1
PGND
CC1
10pF OPT
CTTR
10nF
RPG1
100K
E15
GND
JP1
ON OFF
RUN11
3 2
E3 GND
CC2
10pF
OPT
JP3
MODE
FCM
BURSTMODE
SYNC 1 2
3 4
5 6
R4 17.4k
1%
RFB1 34.8k
1%
RTR1
0
E6
GND
CIN3 47uF
16V
1210
CTR1
4700pF
RD1
OPT

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dc1839af
DEMO MANUAL DC1839A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011
LT 0711 • 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
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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-
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