QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392
HIGH EFFICIENCY DUAL REGULATOR
1
LTC1628 or LTC3728
DESCRIPTION
Demonstration circuit 392 is a dual output, step-down,
synchronous buck converter featuring either the 150kHz
to 300kHz LTC1628EUH controller (DC392A-A), the
250kHz to 550kHz LTC3728EUH (DC392A-B) or 250kHz
to 550kHz LTC3728LUH (DC392A-C). All three ICs come
in a 5mm
×
5mm QFN package with an exposed pad for
low thermal impedance. The input voltage is from 7V up
to 24V. Output 1 is 5V with loads up to 4A and output 2
is 3.3V with loads up to 5A.
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary
PARAMETER CONDITION VALUE
Minimum Input Voltage 7V
Maximum Input Voltage 24V
V
OUT1
V
IN
= 7V to 24V, I
OUT1
= 0A to 4A 5V ±1%
V
OUT2
V
IN
= 7V to 24V, I
OUT1
= 0A to 5A 3.3V ±1%
Switching Frequency (LTC1628)
Switching Frequency (LTC3728)
Jumper selectable
Jumper selectable
150kHz–300kHz
250kHz–550kHz
QUICK START PROCEDURE
Demonstration circuit 392 is easy to set up to evaluate
the performance of the LTC1628 or LTC3728. Refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below:
NOTE:
The input voltage range should be 7V–24V in-
stead of 5V-24V as shown on the board.
NOTE:
When measuring the input or output voltage rip-
ple, 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 2 for
proper scope probe technique.
1.
With the power off, place the jumpers as shown in
Figure 1.
NOTE:
The STBY and FLTCPL jumpers apply only to
demo circuit 392A-A (featuring the LTC1628). These
jumpers are not used for the DC392A-B or
DC392A-C which feature the LTC3728.
2.
Connect the loads at Vout1 and Vout2. The loads
can be up to 4A for Vout1 and 5A for Vout2. Pre-set
the loads to 0A.
3.
Set Vin to 12V (recommended). The rated input
voltage range is from 7V to 24V.
4.
Remove the RUN1 jumper to switch on the Vout1
channel. The nominal output voltage of Vout1
should be 5V ±0.1V.
Increase load current on Vout1 to 4A. At 12V input
voltage, the input current should be less than 2A.
Slowly increase the input voltage to 24V. At 24V in-
put, the input current should be less than 1.1A.
5.
Decrease the load current of Vout1 to 0A. Reduce
the input voltage to 12V.
6.
Remove the RUN2 jumper to switch on the Vout2
channel. The output voltage of Vout2 should be
3.3V ±0.05V.
7.
Increase load current on Vout2 to 5A. At 12V input
voltage, the input current should be less than 1.8A.
Slowly increase the input voltage to 24V. At 24V in-
put, the input current should be less than 1.0A.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392
HIGH EFFICIENCY DUAL REGULATOR
2
+
–
+
–
+
–
+
–
LOAD
+
–
+
–
LOAD
+–
+– +–
Figure 1. Proper Measurement Equipment Setup
VIN
GND
Figure 2. Scope Probe Placement for
Measuring Input or Output Ripple
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 392
HIGH EFFICIENCY DUAL REGULATOR
3
SP
SP
5V @ 4A
5V to 2 4V
3.3V @ 5A
392A-A
ASSEMBLY
392A-B
LTC1628EUH
LTC3728EUH
U1
Table:
CDEP105-4R3MC-88
L1 L2
CDEP105-4R3MC-88
IHLP-2525CZ-01-2.2uH IHLP-2525CZ-01-2.2uH
VOSENSE
Output
Dual Single
Output
ITH
Output
Dual
Output
Single
1
0
FSET
FCB
0
STBY
1
1
01
1
1
RUN2
0
0
RUN1
FLTCPL
0
2,3
Ref.
Pin
Single Output
Short
1,2Pin Pin
1,2
Short
JP8 PinShort
Dual Output
Short
Jumpers Select
2,3
JP7
1,2
Pin
JP3
2,3
Short
1,2
JP2
JP6
Ref.
1,2
JP1
JP5
Jumpers Select
1,2JP4
1,2
R3
0.006 ohm
0.008 ohm
0.006 ohmIHLP-2525CZ-01-2.2uHLTC3728LUH392A-C IHLP-2525CZ-01-2.2uH
R14
20K
1%
D2
CMDSH-3
21 R8
10
C15
0.01uF
E2
Gnd
+
C11
33uF,35V
Sanyo
C10
1uF
D4
MBRM140T3
(Opt.)
Q1A
FDS6982S
2
7
8
1
R5
105 K
1%
E3
Vin
+
C4
150uF,6V
C14
1000pF
+
C8
4.7uF
10V
JP4
1
2
3
C3
1000pF
C13
10uF
35V
C16
100pF
JP5
1
2
3
Q2A
FDS6982S
2
7
8
1
C2
180pF
R13
63.4K
1%
JP6
1
2
3
Q2B
FDS6982S
4
5
6
3
U1
See Table
28
30
31
1
2
3
4
5
6
15
17
14
19
20
21
22
23
24
27
187
8
9
11
12 13
25
26
32
29
10
16
RUN/SS1
SENSE1+
SENSE1-
VOSENSE1
FREQSET
STBYMD
FCB
ITH1
SGND
SW2
BOOST2
TG2
PGND
INTVCC
EXTVCC
BG1
VIN
BOOST1
FLTCPL
BG23.3VOUT
ITH2
VOSENSE2
SENSE2-
SENSE2+ RUN/SS2
SW1
TG1
NC
NC
NC
NC
C9
100pF
JP2
1
2
3
+
C22
180uF,4V
R1
10
C19
180pF
D1
MBRM140T3
(Opt.)
JP1
1
2
3
L1
See Table
C20
1000pF
C12
10uF
35V
C5
0.1uF
C1
0.1uF
Q1B
FDS6982S
4
5
6
3
R11
4.75K
1%
C17
0.1uF
R16
1M
C24
0.01uF
R12
1M
E5
Vout2+
R17
10
R3
See Table
R9
1M
R18
10
R2
10
C25
1uF
R15
0.008
E7
5V LDO
JP3
1
2
3
C32
1uF
JP7
1
2
3
C23
0.1uF
L2
See Table
JP8
1
2
3
E8
3.3V LDO
R4
1M
R7
1M
(Opt.)
R10
8.06K
1%
C6
1500pF
C7
0.1uF
C21
0.01uF
D3
CMDSH-3
21
E1
Vout1+
R6
20K
1%
E4
Gnd
C18
0.01uF
E6
Gnd
A
A
B
B
C
C
D
D
E
E
4 4
3 3
2 2
1 1
SP
SP
5V @ 4A
5V to 24V
3.3V @ 5A
392A-A
ASSEMBLY
392A-B
LTC1628EUH
LTC3728EUH
U1
Table:
CDEP105-4R3MC-88
L1 L2
CDEP105-4R3MC-88
IHLP-2525CZ-01-2.2uH IHLP-2525CZ-01-2.2uH
VOSENSE
Output
Dual Single
Output
ITH
Output
Dual
Output
Single
1
0
FSET
FCB
0
STBY
1
1
01
1
1
RUN2
0
0
RUN1
FLTCPL
0
2,3
Ref.
Pin
Single Output
Short
1,2Pin Pin
1,2
Short
JP8 PinShort
Dual Output
Short
Jumpers Select
2,3
JP7
1,2
Pin
JP3
2,3
Short
1,2
JP2
JP6
Ref.
1,2
JP1
JP5
Jumpers Select
1,2JP4
1,2
R3
0.006 ohm
0.008 ohm
0.006 ohmIHLP-2525CZ-01-2.2uHLTC3728LUH392A-C IHLP-2525CZ-01-2.2uH
DEMO 392A-A,B,C LTC1628EUH or LTC3728EUH
High Efficiency Dual Regulator
LINEAR TECHNOLOGY CORPORATION
1630 McCARTHY BLVD.
MILPITAS, CA 95035
(408) 432-1900
(408) 434-0507 FAX
11Wednesday, July 10, 2002
Title
Size Document Number Rev
Date: Sheet of
R14
20K
1%
D2
CMDSH-3
21 R8
10
C15
0.01uF
E2
Gnd
+
C11
33uF,35V
Sanyo
C10
1uF
D4
MBRM140T3
(Opt.)
Q1A
FDS6982S
2
7
8
1
R5
105K
1%
E3
Vin
+
C4
150uF,6V
C14
1000pF
+
C8
4.7uF
10V
JP4
1
2
3
C3
1000pF
C13
10uF
35V
C16
100pF
JP5
1
2
3
Q2A
FDS6982S
2
7
8
1
C2
180pF
R13
63.4K
1%
JP6
1
2
3
Q2B
FDS6982S
4
5
6
3
U1
See Table
28
30
31
1
2
3
4
5
6
15
17
14
19
20
21
22
23
24
27
187
8
9
11
12 13
25
26
32
29
10
16
RUN/SS1
SENSE1+
SENSE1-
VOSENSE1
FREQSET
STBYMD
FCB
ITH1
SGND
SW2
BOOST2
TG2
PGND
INTVCC
EXTVCC
BG1
VIN
BOOST1
FLTCPL
BG23.3VOUT
ITH2
VOSENSE2
SENSE2-
SENSE2+ RUN/SS2
SW1
TG1
NC
NC
NC
NC
C9
100pF
JP2
1
2
3
+
C22
180uF,4V
R1
10
C19
180pF
D1
MBRM140T3
(Opt.)
JP1
1
2
3
L1
See Table
C20
1000pF
C12
10uF
35V
C5
0.1uF
C1
0.1uF
Q1B
FDS6982S
4
5
6
3
R11
4.75K
1%
C17
0.1uF
R16
1M
C24
0.01uF
R12
1M
E5
Vout2+
R17
10
R3
See Table
R9
1M
R18
10
R2
10
C25
1uF
R15
0.008
E7
5V LDO
JP3
1
2
3
C32
1uF
JP7
1
2
3
C23
0.1uF
L2
See Table
JP8
1
2
3
E8
3.3V LDO
R4
1M
R7
1M
(Opt.)
R10
8.06K
1%
C6
1500pF
C7
0.1uF
C21
0.01uF
D3
CMDSH-3
21
E1
Vout1+
R6
20K
1%
E4
Gnd
C18
0.01uF
E6
Gnd
Itm Qty. Reference Part Manufacture
1 2 C9,C16 CAP., NPO 100pF 50V AVX, 06035A101JAT1A 0603
2 2 C2,C19 CAP., NPO 180pF 50V AVX, 06035A181JAT1A 0603
3 3 C3,C20,C14 CAP., NPO 1000pF 25V AVX, 06033A102JAT1A 0603
4 1 C6 CAP., X7R 1500pF 50V AVX, 06035C152KAT1A 0603
5 4 C15,C18,C21,C24 CAP., X7R 0.01uF 10V AVX, 0603ZC103KAT1A 0603
6 5 C1,C5,C7,C17,C23 CAP., X7R 0.1uF 10V AVX, 0603ZC104MAT1A 0603
7 3 C10,C25,C32 CAP., X5R 1uF 6.3V TAIYO YUDEN, JMK107BJ105MA 0603
8 1 C8 CAP., TANT 4.7uF 10V AVX, TACR475M010R 0805
9 2 C12,C13 CAP., Y5V 10uF 35V TAIYO YUDEN, GMK325F106ZH 1210
10 1 C11 CAP., SP 33uF 35V SANYO, 35CV33BS
11 1 C4 CAP., SP 150uF 6.3V PANASONIC, EEFUE0J151R CASE-D
12 1 C22 CAP., SP 180uF 4V PANASONIC, EEFUE0G181R CASE-D
13 0 D1,D4 (OPTIONAL) DIODE, SCHOTTKY 40V 1A ON SEMI., MBRM140T3 POWERMITE
14 2 D2,D3 DIODE, SUPER MINI SCHOTTKY CENTRAL SEMI., CMDSH-3 SOD323
15 2 L1,L2 INDUCTOR, SMT 2.2uH VISHAY, IHLP-2525CZ-01-2.2uH
16 8 E1-E8 TESTPOINT, TURRET, .094" MILL-MAX 2501-2
17 8 JP1-JP8 HEADER, 3PIN 1 ROW .079CC COMM-CON 2802S-03-G1
18 8 FOR ( JP1-JP8 ) SHUNT, .079" CENTER COMM-CON CCIJ2MM-138G
19 2 Q1,Q2 MOSFET FDS6982S FAIRCHILD FDS6982S SO8
20 1 R3 RES., CHIP 0.006 1/4W 5% IRC, LRF1206-01-R006-J 1206
21 1 R15 RES., CHIP 0.008 1/4W 5% IRC, LRF1206-01-R008-J 1206
22 5 R1,R2,R8,R17,R18 RES., CHIP 10 1/16W 5% AAC, CR16-100JM 0603
23 1 R11 RES., CHIP 4.75K 1/16W 1% AAC, CR16-4751FM 0603
24 1 R10 RES., CHIP 8.06K 1/16W 1% AAC, CR16-8061FM 0603
25 2 R6,R14 RES., CHIP 20.0K 1/16W 1% AAC, CR16-2002FM 0603
26 1 R13 RES., CHIP 63.4K 1/16W 1% AAC, CR16-6342FM 0603
27 4 R4,R9,R12,R16 RES., CHIP 1M 1/16W 5% AAC, CR16-105JM 0603
28 0 R7 (OPTIONAL) RES., CHIP 1M 1/16W 5% AAC, CR16-105JM 0603
29 1 R5 RES., CHIP 105K 1/16W 1% AAC, CR16-1053FM 0603
30 1 U1 I.C., LTC3728EUH LINEAR, LTC3728EUH 32 PIN MLP
31 4 SCREW, #4-40, 1/4" ANY
32 4 STANDOFF, #4-40 1/4" MICRO PLASTICS 14HTSP101
