DEMO MANUAL DC1839A
LTC3634
15V Dual 3A Monolithic
Step-Down Regulator Board
for DDR Power
DESCRIPTION
Demonstration circuit 1839A is a dual output regulator
focused specifically for DDR memory power applications.
It’s built based on the LTC3634, a high voltage dual channel,
controlled on-time monolithic synchronous buck regulator.
The DC1839A has an input voltage range of 3.6V to 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, V TT, 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
provide the 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 output can operate in either Burst Mode® operation or
PERFORMANCE SUMMARY
PARAMETER
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
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.
(TA = 25°C)
CONDITIONS
VALUE
Minimum Input Voltage
3.6V
Maximum Input Voltage
Output Voltage VOUT1 – VDDQ
15V
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)
Output Voltage VOUT2 – V TT
VIN = 3.6V to 15V, IOUT2 = 0A to ±3A
< 20mVP-P
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 V TT
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
3.3V
INTVCC
VTTR
VDDQIN = 2.5V
1.25V
dc1839af
1
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 positions. 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 current 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 channel 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. With the board under proper operation, observe the load
regulation, efficiency, in-phase operation (by changing
jumper XJP4 to the 90° position), or Burst Mode operation (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 bottom 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.
dc1839af
2
DEMO MANUAL DC1839A
QUICK START PROCEDURE
VS
VARIABLE
RESISTOR
Figure 1. Proper Measurement Equipment Setup
dc1839af
3
DEMO MANUAL DC1839A
QUICK START PROCEDURE
GND
VIN
Figure 2. Measuring Input or Output Ripple
100
90
EFFICIENCY (%)
80
70
60
50
VIN = 12V
VDDQ = 2.5V
V TT = 1.25V
fSW = 1MHz
Burst Mode OPERATION
L1 = 1μH
L2 = 0.47μH
VISHAY 2020BZ
40
30
20
10
0
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
2.5
3.0
dc1839a F03
Figure 3. LTC3634 DC1839A Efficiency
dc1839af
4
DEMO MANUAL DC1839A
QUICK START PROCEDURE
dc1839a F05
dc1839a F04
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)
Figure 4. VDDQ Load Step Response
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)
Figure 5. V TT Load Step Response
dc1839a F06
VIN = 12V
VDDQ = 1.8V
V TT = 0.9V
3A LOAD (EACH)
FORCED CONTINUOUS MODE
fSW = 1MHz
CSS = 4700pF
TRACE 1: VDDQ OUTPUT (500mV/DIV)
TRACE 2: V TT OUTPUT (500mV/DIV)
TRACE 3: VTTR OUTPUT (1V/DIV)
TRACE 4: VRUN VOLTAGE (2V/DIV)
Figure 6. LTC3634 DC1839A Start-Up with Soft-Start
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5
DEMO MANUAL DC1839A
PARTS LIST
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
dc1839af
6
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
D
[1]
E6
E9
E15
E12
E10
E1
E2
[1]
0
RTR2
OPT
RTR1
R7
1k
1%
JP2
3
2
1
VIN
3
90°
SS
CTR1
4700pF
OFF
ON
CC1
10pF
OPT
JP1
RUN1
3
2
1
5
4
R1
1M
OPT
RD2
RPG1
100K
INTVCC
1 ITH1
2 TRACKSS1
5 PHMODE
7 MODE/SYNC
22 INTVCC
6 RUN1
9 RUN2
RITH2
15k
1%
OPT
RT
324k
1%
RFREQ
CITH2
1000pF
INTVCC
CITH1 CC2
680pF 10pF
OPT
RITH1
18.2k
1%
CVCC
1uF
0603
VIN
[1] CIN5 AND CIN6 ARE INSERTED ON THE DC1839A 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 ARE 0402.
JP5
3
TRACKSS
1
TRACK
2
2
1
180°
JP4
6
4
2
INTVCC
JP3
MODE
1M
R2
CIN2
47uF
16V
1210
PHASE
5
BURST MODE 1
SYNC 3
OFF
ON
RUN2
CIN4
47uF
16V
1210
OPT
(FORCED FCM
CONTINUOUS
MODE)
INTVCC
CIN6
22uF
35V
7343
CVCC1
1uF
0603
+
NOTES: UNLESS OTHERWISE SPECIFIED
TRACK1
GND
GND
SYNC
INTVCC
PGOOD1
VIN1
3.6V - 15V
CIN1
47uF
16V
1210
VIN
U1
LTC3634EFE
L1 1.0uH
L2 0.47uH
3
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
JW
TOM G.
2
SCALE = NONE
APP ENG.
PCB DES.
APPROVALS
2.5V
R3
11k
1%
JP6
RVDDQ
0
RFB1
34.8k
1%
VISHAY
IHLP-2020BZERR47M01
CBST2
0.1uF
VISHAY
IHLP-2020BZER1R0M01
CBST1
0.1uF
CUSTOMER NOTICE
CTTR
10nF
0603
VON2 15
VFB2 12
17
SW2 16
SW2
BOOST2 20
VON1 28
VFB1 3
SW1 27
SW1 26
BOOST1 23
VDDQIN 13
RPG2
100K
INTVCC
14
CIN3
47uF
16V OPT
1210
ITH2
CIN5
22uF
35V
7343
RT
8
+
PGOOD1 4
SGND
10
E17
VIN1 25
VIN1 24
VIN2 19
VIN2 18
PGND
29
VIN2
PGOOD2 11
VTTR
21
2
OPT
RD1
10pF
CFFW1
DATE:
N/A
SIZE
COUT3
100uF
6.3V
1812
COUT4
100uF
6.3V
1812
IC NO.
1
CTTR1
10nF
0603
OPT
COUT9
10uF
6.3V
0805
E3
E16
E13
E5
E7
E14
COUT7 E4
10uF
6.3V
0805
E11
E8
TOM G.
DATE
06-08-11
GND
GND
VTTR
10mA
VTT
3A
GND
GND
VDDQ
3A
VDDQIN
PGOOD2
APPROVED
Thursday, June 30, 2011
1
LTC3634EFE
DEMO CIRCUIT 1839A
SHEET 1
1
REV.
OF 1
DUAL DDR MONOLITHIC
SYNCHRONOUS STEP-DOWN REGULATOR
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900 www.linear.com
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
COUT8
100uF
6.3V
1812
OPT
COUT5
100uF
6.3V
1812
OPT
PRODUCTION
CDDQIN
10uF
0805
OPT
REVISION HISTORY
DESCRIPTION
TECHNOLOGY
COUT6
100uF
6.3V
1812
1.5V USER SELECT
R6
R5
23.2k OPT
1%
VDDQ SEL
INTVCC
TITLE: SCHEMATIC
COUT2
100uF
6.3V
1812
1.8V
R4
17.4k
1%
OPT
RDDQIN
1
REV
COUT1
100uF
6.3V
1812
__
ECO
2
1
3
4
3
VIN
6
5
4
8
7
5
A
B
C
D
DEMO MANUAL DC1839A
SCHEMATIC DIAGRAM
dc1839af
7
DEMO MANUAL DC1839A
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 application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1839af
8
Linear Technology Corporation
LT 0711 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
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