QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 663
2-PHASE DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
1
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 CONDITION VALUE
Input Voltage Range 2.7V to 8V
V
OUT1
V
IN
= 5V, I
OUT1
= 0A to 5A,
I
OUT2
= 0A to 5A
2.5V ±3%
V
OUT2
V
IN
= 5V, I
OUT1
= 0A to 5A,
I
OUT2
= 0A to 5A
1.8V ±3%
Typical Output Ripple V
OUT1
V
IN
= 3.3V, I
OUT1
= 3A (20MHz BW) 18mV
P–P
Typical Output Ripple V
OUT2
V
IN
= 3.3V, I
OUT2
= 3A (20MHz BW) 26mV
P–P
Typical Switching Frequency PLLLPF Pin Floating 550kHz
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:
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 power off, connect the input power supply to Vin
(2.7V-8V) and GND (input return).
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.)
3.
Connect the DVMs to the input and outputs.
4.
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%.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 663
2-PHASE DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
2
5.
Once the proper output voltages are established, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
parameters.
Figure 1. Proper Measurement Equipment Setup
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 663
2-PHASE DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
3
Figure 2. Scope Probe Placement for Measuring Input or Output Ripple
Figure 3. Efficiency vs Load Current (Burst Mode, 550kHz)
40
50
60
70
80
90
100
1 10 100 1k 10k
LOAD CURRENT (mA)
Vin=3.3V
Vo=2.5V
Vo=1.8V
A
A
B
B
C
C
D
D
E
E
4 4
3 3
2 2
1 1
NOTES:
UNLESS OTHERWISE SPECIFIED
Mode
Continuous
Burst
1.8V ( 5A at 5Vin )2.5V ( 5A at 5Vin )
(Opt.)
(Opt.)
(Opt.)
(Opt.)
(Opt.)
Circuit That Meets Customer-Supplied Specifications;
LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY
Linear Technology Has Made A Best Effort To Design A
Supplied For Use With Linear Technology Parts.
This Circuit Is Proprietary To Linear Technology And
Circuit Board Layout May Significantly Affect Circuit
Applications Engineering For Assistance.
Application. Component Substitution And Printed
However, It Remains The Customer's Responsibility To
Performance Or Reliability. Contact Linear Technology
Verify Proper And Reliable Operation In The Actual
Customer Notice
DEMO 663A LTC3736EUF
LTC3736EUF 2-Phase Dual Synchronous Step-Down Converter
LINEAR TECHNOLOGY CORPORATION
1630 McCARTHY BLVD.
MILPITAS, CA. 95035
408-432-1900
408-434-0507 FAX
1 1Monday, December 01, 2003
Title
Size Document Number Rev
Date: Sheet of
VINVIN
VIN
R4
187K
1%
R1
10
R12
10K
R2
1M
C15
(Opt.)
C17
( Opt. )
C12
100pF
C1
22uF
10V
E3
Vout2
C2
22uF
10V
E5
Gnd
C7
10uF
6.3V
R13
10K
U1
LTC3736EUF
5
81
2
3
4
7
6
9
10
11
12
16
15
14
13
17
18
19
20
21
22
23
24
25
VIN
ITH2ITH1
IPRG2
PLLLPF
SGND
VFB2
TRACK
PGOOD
SW2
SENSE2+
PGND2
PGND
TG2
RUN/SS
BG2
TG1
SYNC/FCB
BG1
PGND1
SENSE1+
SW1
IPRG1
VFB1
PGND
E4
Gnd
C14
220pF
R9
15K
E1
Vin
2.7V - 8V
C11
220pF
L2
1.5uH
IHLP-2525CZ-01
R6
59K
1%
+
C9
150uF
4V
Sanyo
C13
100pF
Q3
Si3447BDV 3
1
2
4
5
6
C18
( Opt. )
R8
15K
R3
118K
1%
R10
59K
1%
C8
10uF
6.3V
R11
10K
C3
1uF
10V
E10
IPRG1
R5
118K
1%
JP1
1
2
3
C19
10uF
10V
C10
0.01uF
E8
RUN/SS
C20
10uF
10V
Q2B
Si7540DP
3
4
5
6
Q5
Si3460DV 3
1
2
4
5
6
E13
SGnd
+
C6
150uF
4V
Sanyo
E6
SYNC/FCB
Q2A
Si7540DP
1
2
7
8
L1
1.5uH
IHLP-2525CZ-01
E11
IPRG2
Q1A
Si7540DP
1
2
7
8
Q6
Si3460DV
3
1
2
4
5
6
C16
( Opt. )
E2
Vout1
Q1B
Si7540DP
3
4
5
6
E9
PLLLPF
E7
PGOOD
R7
59K
1%
Q4
Si3447BDV
3
1
2
4
5
6
E12
Gnd
Linear Technology Corporation
LTC3736EUF
Bill Of Material
Demo Bd. #663A
6/20/2005
Item Qty Reference Part Description Manufacture / Part #
1 2 C12,C13 CAP., X7R, 100pF 50V AVX, 04025C101MAT 0402
2 2 C11,C14 CAP., X7R, 220pF 50V AVX, 04025C221MAT 0402
3 1 C10 CAP., X7R, 0.01uF 25V AVX, 04023C103MAT 0402
4 1 C3 CAP., X5R, 1uF 10V TAIYO YUDEN, LMK107BJ105MA 0603
5 2 C7,C8 CAP., X7R, 10uF 6.3V TAIYO TUDEN, JMK316BJ106ML 1206
6 2 C19,C20 CAP., X5R, 10uF 10V TDK, C3216X5R1A106KT
7 1 C1 CAP., X7R, 22uF 10V TAIYO YUDEN, LMK432BJ226MM 1812
8 2 C6,C9 CAP., POSCAP, 150uF, 4V SANYO, 4TPB150MC C-CASE
9 0 C2,C15-C18 OPTION
10 7 E6-E11,E13 TURRET, TEST PIN, .061" MILL-MAX 2308-2-00-44 (counted)
11 6 E1-E5,E12 TURRET, TEST PIN, .095" MILL-MAX 2501-2 (counted / sealed)
12 1 JP1 JUMPER, 0.079"CC, 3PIN COMM CON, 2802S-03G2
13 1 JP1 SHUNT COMM CON, CCIJ2MM-138GW
14 2 L1,L2 INDUCTOR, 1.5uH VISHAY, IHLP-2525CZ-01-1.5
15 2 Q1,Q2 N-and -P MOSFET 12-V (D-S) VISHAY, Si7540DP POWERPAK SO-8
16 0 Q3,Q4 (OPTIONAL) P-MOSFET 12-V ( D-S ) VISHAY, Si3447BDV TSOP-6
17 0 Q5,Q6 (OPTIONAL) N-MOSFET 20-V ( D-S ) VISHAY, Si3460DV TSOP-6
18 1 R1 RES., CHIP, 10 1/16W 5% AAC, CR05-100JM 0402
19 3 R11-R13 RES., CHIP, 10K 1/16W 5% AAC, CR05-103JM 0402
20 2 R8,R9 RES., CHIP, 15K 1/16W 5% AAC, CR05-153JM 0402
21 3 R6,R7,R10 RES., CHIP, 59K 1/16W 1% AAC, CR05-5902FM 0402
22 1 R2 RES., CHIP, 1M 1/16W 5% AAC, CR05-105JM 0402
23 2 R3,R5 RES., CHIP, 118K 1/16W 1% AAC, CR05-1183FM 0402
24 1 R4 RES., CHIP, 187K 1/16W 1% AAC, CR05-1873FM 0402
25 1 U1 I.C., LTC3736EUF LINEAR, LTC3736EUF QFN24
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