2-PHASE DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 663
LTC3736EUF
DESCRIPTION
Demonstration circuit 663 is a 2-phase dual synchro-
nous high efficiency step-down DC/DC converter with
2.7V to 8V input range. It has two outputs: 2.5V (5A
MAX at 5V input) and 1.8V (5A MAX at 5V input). The
demo board features the LTC®3736EUF controller. The
constant frequency current mode architecture with
MOSFET V
DS
sensing eliminates the need for sense re-
sistors and improves efficiency. Out of phase operation
significantly reduces peak input ripple current; thereby
reducing the noise and input capacitor size.
Switching frequency is internally set at 550kHz. For
noise sensitive applications, the converter can be exter-
nally synchronized from 250kHz to 850kHz. The fre-
quency can also be selected with PLLLPF pin. Tying
PLLLPF pin to GND selects 300kHz operation; tying
PLLLPF pin to VIN selects 750kHz operation.
The demo circuit has output tracking, allowing V
OUT2
to
track V
OUT1
during start-up.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Table 1. Performance Summary (T
A
= 25°C)
PARAMETER
Input Voltage Range
V
OUT1
V
IN
= 5V, I
OUT1
= 0A to 5A,
I
OUT2
= 0A to 5A
V
OUT2
V
IN
= 5V, I
OUT1
= 0A to 5A,
I
OUT2
= 0A to 5A
Typical Output Ripple V
OUT1
Typical Output Ripple V
OUT2
Typical Switching Frequency
V
IN
= 3.3V, I
OUT1
= 3A (20MHz BW)
V
IN
= 3.3V, I
OUT2
= 3A (20MHz BW)
PLLLPF Pin Floating
18mV
P–P
26mV
P–P
550kHz
1.8V ±3%
CONDITION
VALUE
2.7V to 8V
2.5V ±3%
QUICK START PROCEDURE
Demonstration circuit 663 is easy to set up to evaluate
the performance of the LTC3736. Refer to Figure 1. for
proper measurement equipment setup and follow the
procedure below:
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.
NOTE:
When
2.
Connect the 2.5V load (Load 1 in Figure 1.) between
Vout1 and GND; connect the 1.8V load (Load 2 in Fig-
ure 1.) between Vout2 and GND. (Initial loads: no
load.)
Connect the DVMs to the input and outputs.
Turn on the input power supply and check for the
proper output voltages. Vout1 should be 2.5V+/-3%.
Vout2 should be 1.8V+/-3%.
3.
4.
With power off, connect the input power supply to Vin
(2.7V-8V) and GND (input return).
1
2-PHASE DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
5.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 663
the output voltage regulation, ripple voltage and other
parameters.
Once the proper output voltages are established, ad-
just the loads within the operating range and observe
Figure 1. Proper Measurement Equipment Setup
2
A
B
C
D
E
VIN
Vin
2.7V - 8V
C20
10uF
10V
E1
4
4
C19
10uF
10V
Burst
Continuous
3
JP1
Mode
2
C3
1uF
10V
R1
10
R2
1M
C1
22uF
10V
C2
22uF
10V
(Opt.)
3
Gnd
E12
Q1B
Si7540DP
1
3
VIN
PGND
25
5
4
Q2B
Si7540DP
7
8
Q2A
Si7540DP
4
2
Q4
Si3447BDV
(Opt.)
1
2
5
6
3
17
22
19
15
10
13
16
9
3
2
7
8
PGOOD
E7
PLLLPF
E9
IPRG2
R5
118K
1%
E11
VIN
R13
10K
2
4
6
5
Q1A
Si7540DP
Q3
Si3447BDV
(Opt.)
6
5
2
1
4
2
3
8
7
20
21
PGND1
SENSE1+
PGND2
SENSE2+
12
11
Vout1
3
5
6
2.5V ( 5A at 5Vin )
E2
C6
+
150uF
4V
Sanyo
C7
10uF
6.3V
L1
1.5uH
IHLP-2525CZ-01
TG1
SW1
BG1
SYNC/FCB
RUN/SS
TRACK
IPRG1
VFB1
ITH1
U1
LTC3736EUF
SGND
TG2
SW2
BG2
PGND
PGOOD
PLLLPF
IPRG2
VFB2
ITH2
L2
1.5uH
IHLP-2525CZ-01
C8
10uF
6.3V
Vout2
1.8V ( 5A at 5Vin )
C9
+
150uF
4V
Sanyo
E3
3
1
6
5
2
1
Gnd
E4
Q5
Si3460DV
(Opt.)
4
3
18
14
6
23
24
3
4
1
2
5
6
Q6
Si3460DV
(Opt.)
1
Gnd
E5
SYNC/FCB
E6
RUN/SS
E8
2
1
IPRG1
E10
C15
(Opt.)
R3
118K
1%
4
C10
0.01uF
R12
10K
VIN
C16
( Opt. )
R4
187K
1%
C11
220pF
C12
100pF
C13
100pF
C14
220pF
SGnd
E13
C17
( Opt. )
R6
59K
1%
R7
59K
1%
R8
15K
R9
15K
R10
59K
1%
R11
10K
C18
( Opt. )
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
1
Customer Notice
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.
This Circuit Is Proprietary To Linear Technology And
Supplied For Use With Linear Technology Parts.
B
C
D
1630 McCARTHY BLVD.
MILPITAS, CA. 95035
408-432-1900
408-434-0507 FAX
Title
LINEAR TECHNOLOGY CORPORATION
1
NOTES:
UNLESS OTHERWISE SPECIFIED
LTC3736EUF 2-Phase Dual Synchronous Step-Down Converter
Document Number
Size
Date:
DEMO 663A
LTC3736EUF
Sheet
E
Rev
1
Monday, December 01, 2003
1
of
A
Linear Technology Corporation
LTC3736EUF
Bill Of Material
Demo Bd. #663A
6/20/2005
Item Qty Reference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
2
2
1
1
2
2
1
2
0
7
6
1
1
2
2
0
0
1
3
2
3
1
2
1
1
C12,C13
C11,C14
C10
C3
C7,C8
C19,C20
C1
C6,C9
C2,C15-C18
E6-E11,E13
E1-E5,E12
JP1
JP1
L1,L2
Q1,Q2
Q3,Q4 (OPTIONAL)
Q5,Q6 (OPTIONAL)
R1
R11-R13
R8,R9
R6,R7,R10
R2
R3,R5
R4
U1
Part Description
CAP., X7R, 100pF 50V
CAP., X7R, 220pF 50V
CAP., X7R, 0.01uF 25V
CAP., X5R,
1uF 10V
CAP., X7R, 10uF 6.3V
CAP., X5R, 10uF 10V
CAP., X7R, 22uF 10V
CAP., POSCAP, 150uF, 4V
OPTION
TURRET, TEST PIN, .061"
TURRET, TEST PIN, .095"
JUMPER, 0.079"CC, 3PIN
SHUNT
INDUCTOR, 1.5uH
N-and -P MOSFET 12-V (D-S)
P-MOSFET 12-V ( D-S )
N-MOSFET 20-V ( D-S )
RES., CHIP, 10 1/16W 5%
RES., CHIP, 10K 1/16W 5%
RES., CHIP, 15K 1/16W 5%
RES., CHIP, 59K 1/16W 1%
RES., CHIP, 1M 1/16W 5%
RES., CHIP, 118K 1/16W 1%
RES., CHIP, 187K 1/16W 1%
I.C., LTC3736EUF
Manufacture / Part #
AVX, 04025C101MAT
0402
AVX, 04025C221MAT
0402
AVX, 04023C103MAT
0402
TAIYO YUDEN, LMK107BJ105MA 0603
TAIYO TUDEN, JMK316BJ106ML 1206
TDK, C3216X5R1A106KT
TAIYO YUDEN, LMK432BJ226MM 1812
SANYO, 4TPB150MC
C-CASE
MILL-MAX 2308-2-00-44
(counted)
MILL-MAX 2501-2
(counted / sealed)
COMM CON, 2802S-03G2
COMM CON, CCIJ2MM-138GW
VISHAY, IHLP-2525CZ-01-1.5
VISHAY, Si7540DP
POWERPAK SO-8
VISHAY, Si3447BDV
TSOP-6
VISHAY, Si3460DV
TSOP-6
AAC, CR05-100JM
0402
AAC, CR05-103JM
0402
AAC, CR05-153JM
0402
AAC, CR05-5902FM
0402
AAC, CR05-105JM
0402
AAC, CR05-1183FM
0402
AAC, CR05-1873FM
0402
LINEAR, LTC3736EUF
QFN24
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