DC1184A - Demo Manual

DEMO CIRCUIT 1184A
QUICK START GUIDE
LTC3860EUH
DUAL OUTPUT
SYNCHRONOUS BUCK CONVERTER
DESCRIPTION
Demonstration circuit DC1184A is a dual output voltage
mode synchronous buck converter featuring the
LTC3860EUH. This board provides two outputs of
1.2V/25A and 1.8V/25A from an input voltage of 10V to
14V at a switching frequency of 500kHz. The power
stage consists of the Renesas R2J20602NP which is a
tri-state PWM compatible 8mm x 8mm DrMOS and a
0.47uH 13.2mm x 12.8mm iron powder type inductor
from Wurth. An on-board 5V LT1616 buck regulator
provides the 5V bias for the LTC3860 and the DrMOS.
The demo board uses a high density, two sided drop-in
layout. The power components, excluding the bulk output and input capacitors, fit within a 1.5” x 1.25” area
on the top layer. The control circuit resides in a
0.75” x 0.75” area on the bottom layer. The package
style for the LTC3860EUH is a 32-lead 5mm x 5mm
QFN.
Table 1.
The main features of the board are listed below:
• Differential amplifier for remote sensing VOUT1
which is setup for 1.2V.
• Optional components for single output dual
phase operation.
• CLKIN pin for synchronization to an external
clock which can be used in conjunction with
optional PHSMD resistors and CLKOUT pin for
up to 12-phase operation.
• TRACK/SS pins for external coincident rail
tracking.
• RUN pins and PGOOD pins for each phase.
• For each phase, optional footprints for an
LTC4449 gate driver and two top FETs and two
bottom FETs.
Design files for this circuit board are available. Call
the LTC factory.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
10V
Maximum Input Voltage
14V
Output Voltage VOUT1
IOUT1 = 0A TO 25A, VIN = 10V to 14V
1.2V ± 1.75%
Output Voltage VOUT2
IOUT2 = 0A TO 25A, VIN = 10V to 14V
1.8V ± 1.75%
Nominal Switching Frequency
500kHz
Efficiency
VOUT1 = 1.2V, IOUT1 = 25A, VIN = 12V
87.8% typical
See Figure 2
VOUT2 = 1.8V, IOUT2 = 25A, VIN = 12V
91.0% typical
1
LTC3860EUH
QUICK START PROCEDURE
Demonstration circuit 1184A is easy to set up to evaluate the performance of the LTC3860EUH. Refer to Figure 1 for the proper measurement equipment setup and
follow the procedure below:
1.
2.
3.
Place jumpers in the following positions:
JP1
RUN1
ON
JP2
RUN2
ON
JP3
INT 5V
ON
JP4
+5V SELECT
INT
With power off, connect the input power supply
to VIN and GND. Turn on the power at the input
and increase the input voltage to 10V or higher.
Check for the proper output voltages:
Vout1 = 1.179V to 1.221V
Vout2 = 1.769V to 1.832V
4.
Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
Do not apply load between the VOS1+ and
VOS1- pins or between the VO2+ and VO2- pins. These
pins are only intended to sense the output voltage
across COUT4 and COUT10 respectively. Heavy load
currents applied across these pins may damage the
converter.
Note 1.
Use J9 and J10 to monitor the output voltage ripple. J9 will measure the ripple across COUT2 and
J10 will measure the ripple across COUT8. Connect J9
and J10 to the oscilloscope with a short coaxial cable.
To avoid excessive noise pickup, keep the length of the
cable to a minimum.
Note 2.
SINGLE OUTPUT / DUAL PHASE OPERATION
A single output / dual phase converter may be preferred
for high output current applications. The benefits of
single output / dual phase operation is lower ripple current through the input and output capacitors, improved
load step response and simplified thermal design. To
implement single output / dual phase operation, make
the following modifications:
1. Select phase 1 to be the master and
phase 2 the slave since the differential
amplifier already senses VOUT1.
2. Stuff R16 with 0 Ohms to disable the error
amp for phase 2.
3. Stuff 0 Ohms at R49 to tie COMP1 to
COMP2 and remove the redundant compensation components.
4. Stuff R20 with 0 Ohms.
5. Remove 0 Ohm resistor at R25 to release
IAVG from ground.
6. Stuff C16 with 100pF to filter the IAVG
signal.
7. Stuff R60 with 0 Ohms to tie the two RUN
pins together.
8. Stuff R57 with 0 Ohms to tie the two TRK/SS
pins together.
9. Tie VOUT1 to VOUT2 by tying together the
exposed copper pads on the VOUT
shapes with pieces of heavy copper foil.
2
LTC3860EUH
VOUT1
+
V
-
IIN
A
+
VOUT1
load
IOUT1
A
VIN
supply
A
+
+
VOUT2
load
IOUT2
-
+
VIN
V
-
+
V
-
VOUT2
Figure 1. Proper Measurement Equipment Setup
DC1184A
Efficiency at Vin = 12V, Fsw = 500kHz
95
1.8V
90
Efficiency
1.2V
85
80
Parameters and conditions:
● DrMOS = Renesas R2J20602NP.
● L = Wurth 744355147 (0.47uH, DCR= 0.67mOhms +/- 10%).
● No external bias applied; 5V bias for LTC3860 and DrMOS
supplied from on-board 5V LT1616 buck converter.
● Other rail disabled.
● No airflow.
75
70
0
5
10
15
20
25
30
Load current (Amps)
Figure 2. Typical Efficiency Curves
3
E28
DRMBIAS
E19
GND
E15
CLKOUT
E12
TRK/SS2
E13
CLKIN
E8
TRK/SS1
E5
PGOOD1
E4
PGOOD2
OFF
ON
OFF
3
2
JP2
0
R9
R28
(Opt)
0
R24
(Opt)
R51
(Opt)
R50
R57
(Opt)
VDIF1
DRMBIAS2
0
R71
R1B
20K
1%
R3A
499
1%
C3A
2200pF
R77
10.0K
1%
R76
30.1K
1%
C1A
C1B
R49
(Opt)
VOS1+
VOS1-
VDIF1
VCC
7
6
5
4
3
8
33
29
30
R19
(Opt)
COMP1
2
VCC
R29
C14
0.1uF
FB2
SGND
SGND
SGND
COMP2
VSNSP
VSNSN
VSNSOUT
COMP1
FB1
1uF
C7
C6
0.1uF
(Opt)
R30
40.2K
1%
Fswitch = 500kHz typical
C3B
2200pF
R3B
499
1%
100pF
6.34K
1% C2B 680pF
R2B
100pF
R12
(Opt)
R8
(Opt)
VOUT2
U1
LTC3860EUH
6.34K
1% C2A 680pF
R2A
VIN
VCC
C17
(Opt)
R34
(Opt)
(Opt)
R33
23
24
PWMEN1
C16
(Opt)
31
16
19
20
21
22
25
R25
0
(Opt)
PWM1
R32
(Opt)
PWM2
R53
(Opt)
0
TP3
TP2
TP4
DISBL#
NC
NC
PWM
VIN
55
R23
10.0K
C12
1uF
25V
DRMBIAS2
2
53
56
55
2
53
56
DRMDISBL2
VIN
C10
0.22uF
C9
0.22uF
TP1
R17
VCC
R27
(Opt)
R52
(Opt)
R7
(Opt)
DRMDISBL1
R26
59.0K
1%
R20
(Opt)
VCC
C11
(Opt)
PWMEN2
VINSNS
PWM2
ISNS2P
ISNS2N
ISNS1N
ISNS1P
PWM1
R13
59.0K
1%
R10
(Opt)
VCC
R54
(Opt)
R5
DRMDISBL2
VCC
R2
10.0K
C2
1uF
25V
DRMBIAS1
NC
NC
PWM
DISBL#
6. STUFF R60 WITH 0 OHMS.
7. STUFF R57 WITH 0 OHMS.
8. REMOVE REDUNDANT COMPENSATION COMPONENTS.
9. TIE VOUT1 AND VOUT2 SHAPES TOGETHER.
1. FOR VOUT1, APPLY EXCITATION SIGNAL ACROSS R6.
2. FOR VOUT2, APPLY EXCITATION SIGNAL ACROSS
R71 AND CHANGE ITS VALUE TO 10 OHMS.
BODE PLOT SETUP:
1. STUFF R16 WITH 0 OHMS.
2. STUFF R49 WITH 0 OHMS.
3. STUFF R20 WITH 0 OHMS.
4. REMOVE 0 OHM RESISTOR AT R25.
5. STUFF C16 WITH 100PF.
MODIFICATIONS FOR SINGLE OUTPUT / DUAL PHASE
OPERATION WHERE PHASE 1 = MASTER:
RBB
10.0K
1%
R16
(Opt)
VCC
RBA
20K
1%
R1A
20K
1%
R75
10.0K
1%
R15
(Opt)
VCC
0
R70
VOUT2
COMP1
R60
(Opt)
DRMBIAS1
R61
(Opt)
R3
100K
C4
1000pF
C1
1000pF
R4
100K
VCC
R21
10.0K
VCC
3
2
RUN2 1
JP1
RUN1 1
4
ON
R1
2.2
7
GH
NOTE: UVL0 = 9V, Typical
32
58
VIN
VLDRV
2.2
R18
VDRIVE
VDRIVE
VIN
C8
4.7uF
10V
0805
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
C3
1uF
25V
X5R
U2
R2J20602NP
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
VSWH
C13
1uF
25V
X5R
0603
U3
R2J20602NP
59
21
40
41
42
43
44
45
46
47
48
49
50
CIN8
22uF
16V
59
21
40
41
42
43
44
45
46
47
48
49
50
CIN2
22uF
16V
1210
SW2
C15
0.22uF
R73
0
CIN7
22uF
16V
L2
1. ALL RESISTORS ARE IN OHMS, 0603.
2. ALL CAPACITORS ARE IN MICROFARAD, 0603.
R63
1.00K
1%
VOUT2
0.47uH
744355147
Wurth Electronik
R31
2.87K
1%
R62
1.00K
1%
VOUT1
VIN
L1
0.47uH
744355147
Wurth Electronik
R11
2.87K
1%
SW1
C5
0.22uF
R72
0
CIN1
22uF
16V
1210
CIN3
(Opt)
1210
VOUT2
R14
10
COUT10
100uF
6.3V
COUT11
(Opt)
1210
COUT5
(Opt)
1210
R6
10
E3
VOS1+
VOS1E11
COUT4
100uF
6.3V
VOS1-
VOUT1
VOS1+
+
+
CIN6
180uF
16V
(Opt)
COUT2
330uF
2.5V
7343
+
+
+
COUT3
330uF
2.5V
7343
CIN5
180uF
16V
16SVP180MX
J5
VOUT1-
J4
VOUT1+
1.2V / 25A
E2
VIN-
J2
GND
J1
VIN
10V - 14V
E20
VO2-
E14
VO2+
+
COUT7
330uF
2.5V
7343
+
COUT8
330uF
2.5V
7343
+
COUT9
330uF
2.5V
7343
J8
VOUT2-
J7
VOUT2+
1.8V / 25A
5. USE E14 AND E20 TO MONITOR THE DC VOLTAGE
OF VOUT2 WITH ANY DMM.
4. USE E3 AND E11 TO MONITOR THE DC VOLTAGE OF
VOUT1. ONLY USE A BATTERY POWERED DMM.
3. DO NOT CONNECT SCOPE GROUND TO E11.
2. ONLY APPLY LOAD FROM J7 TO J8 ON VOUT2.
NOTE: 1. ONLY APPLY LOAD FROM J4 TO J5 ON VOUT1.
COUT1
330uF
2.5V
7343
CIN4
(Opt)
1210
E1
VIN+
04/14/10
Mike S.
VIN
01/11/10
Mike S.
Value Change: R74, R76, Q1, Q2, Q11 & Q12.
DATE
06/22/09
APPROVED
Mike Shriver
6
DESCRIPTION
PRODUCTION
Value Change: R2A, R2B, R30, R26, R13, COUT17,
COUT22, C30 & C31. (FSwitch 400kHz to 500kHz)
4
-
REVISION HISTORY
5
REV
NOTE: UNLESS OTHERWISE SPECIFIED.
C18
4.7uF
10V
0805
5
BOOT
R74
30.1K
1%
1
9
VIN
14
VCC
27
SS2
11
SS1
CLKIN
26
PWMEN1
17
PGOOD2
FREQ
10
PGOOD1
CLKOUT
12
RUN2
PHSMD
13
RUN1
IL1M1
IAVG
28
ILIM2
18
PWMEN2
15
CGND
57
CGND
57
VCIN
4
VCIN
1
6
51
GL
52
CGND
CGND
CGND
1
6
51
7
3
GH
CGND
CGND
CGND
8
9
10
11
12
13
14
15
16
17
18
19
20
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
GL
58
VIN
VLDRV
3
54
Reg5V
8
9
10
11
12
13
14
15
16
17
18
19
20
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
VIN
52
54
Reg5V
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
5
BOOT
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
ECO
LTC3860EUH
4
OFF
ON
C24
1uF
R40
2.2
VDRIVE
C21
1uF
R35
2.2
VDRIVE
4
5
6
7
GND
IN
VLOGIC
VCC
9
GND
BG
TS
TG
BOOST
3
2
1
8
0
R64
C20
0.22uF
4
Q6
RJK0330DPB
4
Q1
RJK0305DPB
1 2 3
5
1 2 3
5
4
4
Q2
RJK0305DPB
1 2 3
5
1 2 3
5
3
2
JP3
INT 5V1
VIN
PWM2
0805
4.7uF
C22
4
5
6
7
D6
C26
1uF
GND
IN
VLOGIC
VCC
2
4
5
9
GND
BG
TS
TG
BOOST
3
2
1
8
GND
SHDN
VIN
FB
SW
BOOST
U6
LT1616ES6
U5
LTC4449EDCB
CMDSH-3
3
6
1
0
R65
R45
6.65K
1%
R46
20K
1%
C25
0.22uF
4
1 2 3
5
15uH
A914BYW-150M
D4
B0530W-7-F
L3
5
1 2 3
CMDSH-3
D3
4
Q13
RJK0330DPB
5V BIAS
0.22uF
C23
Q11
RJK0305DPB
C27
10uF
10V
0805
5
1 2 3
5
1 2 3
VCC
C28
1uF
4
4
Q12
RJK0305DPB
CIN9
22uF
16V
1210
10
R47
Q14
RJK0330DPB
SW2
VIN
VIN
CIN12
22uF
16V
1210
CIN10
22uF
16V
1210
3
0 C29
1uF
R48
EXT
JP4
+5V SELECT
1
INT
2
CIN11
22uF
16V
1210
Q7
RJK0330DPB
SW1
OPTIONAL DISCRETE GATE DRIVER AND MOSFETS FOR PHASE 2
PWM1
4.7uF
0805
C19
U4
LTC4449EDCB
CMDSH-3
D5
OPTIONAL DISCRETE GATE DRIVER AND MOSFETS FOR PHASE 1
VDRIVE
E26
GND
E25
VDRIVE
R37
10.0K
GND
ISTEP1
JP5
10mV / A
5% DUTY CYCLE MAX.
PULSED LOAD1 CURRENT
R39
0.010
1%
2010
Q4
SUD50N03-12P
R41
10.0K
R68
(Opt)
PWMEN2
R66
(Opt)
PWMEN1
(Opt)
R69
(Opt)
R67
DRMDISBL2
DRMDISBL1
PWM ENABLE CIRCUIT FOR
NON-THREE STATE
COMPATIBLE DRMOS
E24
GND
E23
PULSE GEN2
5% DUTY CYLCE MAX.
GND
ISTEP2
JP6
10mV / A
5% DUTY CYCLE MAX.
PULSED LOAD2 CURRENT
R44
0.010
1%
2010
Q9
SUD50N03-12P
DYNAMIC LOAD CIRCUIT FOR VOUT2
E22
GND
E21
PULSE GEN1
5% DUTY CYLCE MAX.
DYNAMIC LOAD CIRCUIT FOR VOUT1
+
+
COUT18
(Opt)
7343
COUT13
(Opt)
7343
+
+
COUT19
(Opt)
7343
COUT14
(Opt)
7343
+
+
COUT20
(Opt)
7343
COUT15
(Opt)
7343
COUT21
(Opt)
1210
COUT16
(Opt)
1210
VOUT1
COUT22
100uF
6.3V
1210
VOUT2
COUT17
100uF
6.3V
1210
C31
4.7uF
10V
(Opt)
0805
C30
4.7uF
10V
(Opt)
0805
J10
J9
VOUT2
VOUT1
LTC3860EUH
5
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