DC1580A - Demo Manual

DEMO CIRCUIT 1580A
QUICK START GUIDE
LTC3856EUH
HIGH EFFICIENCY POLYPHASE BUCK CONVERTER
DESCRIPTION
Demonstration circuit 1580A is a high efficiency,
polyphase, synchronous buck converter with 4.5V to
14V input range. It can supply 50A maximum load
current at 1.5V output. The demo board uses the
LTC®3856EUH controller. The LTC3856 is a feature-rich single-output dual-phase synchronous buck
controller with on-chip drivers, remote output voltage sensing. This board is setup with sense resistor
configuration with optional inductor DCR sensing
circuit. Temperature compensation function can
guarantee accurate current limit over a wide temperature range with DCR sensing. Stage shedding
function allows the controller to decrease the phase
number to be one at the light load condition in order
to save switching related loss. Adaptive voltage positioning (AVP) can help improve the transient response. The LTC3856 is suitable for input from 4.5V
to 38V and output up to 5V. The LTC3856 can provide high efficiency, high power density and versatile
power solutions for telecom and datacom systems,
industrial and medical instruments, DC power distribution systems and computer systems. The controller is available in 32-pin 5mm × 5mm QFN and 38pin SSOP packages.
Table 1.
The RUN pin (JP1) provides enable feature. To shut
down the converter, one simple way is to force the
RUN pin below 1.2V (JP1: OFF). Use JP3 jumper to
select burst mode, stage shedding mode or forced
continuous mode operation. The phase of CLKOUT
is set by JP2. Switching frequency is pre-set at
about 400KHz, and it can be easily modified from
250KHz to 770KHz. Please see LTC3856 data sheet
for detailed information.
Design files for this circuit board are available. Call
the LTC factory.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
Input Voltage Range
VALUE
4.5V to 14V
Output Voltage, VOUT
VIN = 4.5-14V, IOUT = 0A to 50A
1.5V ±2%
Maximum Output Current, IOUT
VIN = 4.5-14V, VOUT = 1.5V
50A
Typical Efficiency
VIN = 12V, VOUT = 1.5V, IOUT = 50A
87.7%
Typical Switching Frequency
400kHz
1
LTC3856EUH
QUICK START PROCEDURE
Demonstration circuit 1580A is easy to set up to
evaluate the performance of the LTC3856EUH. Refer
to Figure 1 for the proper measurement equipment
setup and follow the procedure below:
1. With power off, connect the input power supply to Vin (4.5V-14V) and GND (input return).
2. Connect the 1.5V output load between Vout
and GND (Initial load: 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. Vout should be
1.5V+/-2%.
5. Once the proper output voltages are established, adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage and other parameters.
Note: When measuring the output or input voltage
ripple, do not use the long ground lead on the oscilloscope probe. See Figure 2 for the proper scope probe
technique. Short, stiff leads need to be soldered to the
(+) and (-) terminals of an output capacitor. The
probe’s ground ring needs to touch the (-) lead and
the probe tip needs to touch the (+) lead.
2
LTC3856EUH
Figure 1. Proper Measurement Equipment Setup
+
COUT
VOUT
-
GND
Figure 2. Measuring Output Voltage Ripple
3
LTC3856EUH
Figure 3. Efficiency vs load current
4
E4
E2
E3
COUT2
100uF
6.3V
VOUT
PGOOD
GND
EXTVCC
SHT 2 EXTVCC
SHT 2 ITEMP
TRK/SS
E9
3
ON
O FF
C2
0.1uF
JP1
1
2
RUN
COUT3
100uF
6.3V
R46
100K
PS
1
COUT4
100uF
6.3V
INTVCC
JP2
BM
MODE
EXTVCC
C50
1uF
1
DEG DEG DEG
4
+ COUT6
330uF
2.5V
JP3
4
+ COUT8
330uF
2.5V
R48
OPT
R65
30.1K
20.0K
R78
0
OPT
R63
C58
+ COUT7
330uF
2.5V
C51
OPT
CCM
R31
8.45K
C42
47pF
3.3nF
R28
OPT
R26
OPT
C38
OPT
VIN
C41
PHASMD
INTVCC 120 90
60
R2
OPT
R3 0
0
2
PLLIN
R77
+ COUT9
330uF
2.5V
OPT
R64
9
DIFFP
EXTVCC
ISET
DIFFOUT
DIFFN
DIFFP
PHASMD
ITEMP
AVP
ITH
VFB
TRK/SS
RUN
R44
OPT
R42
OPT
20
12
11
+ COUT12
OPT
PGOOD
MODE
+ COUT10
330uF
2.5V
INTVCC
49.9k
R66
R79 0
10
6
PHASMD
DIFFN
5
ITEMP
4
3
ITH
AVP
2
1
TRK/SS
VFB
30
FREQ
RUN
LTC3856EUH
U1
R7 100K 1%
PLLIN
CLKOUT
ILIM
13
3
27
15
VIN
+ COUT13
OPT
SW1
26
S2+
7
R39
200
S2-
BG2
19
TG2
SW2
8
R9
1nF
C14
1nF
C15
0
R25
4.7uF
INTVCC
C11
16
18
17
21
23
BG1
TG1
25
24
S1+
32
S1-
R29
200
31
+ COUT14
OPT
SENSE2-
SENSE2+
BG2
SW2
BOOST2
TG2
INTVCC
BG1
BOOST1
SW1
TG1
SENSE1+
SENSE1-
0.1uF
C17
R18
2.2
R40
200
0
R30
200
INTVCC
INTVCC
C21
0.1uF
CMDSH-3
D2
CMDSH-3
D1
C20
0.1uF
4
4
Q4
RJK0330DPB
4
Q3
RJK0305DPB
4
Q2
RJK0330DPB
4
Q1
RJK0305DPB
1
2
3
E1
2
29
FRE Q
28
P LLIN
MODE
14
CLK OUT
PGOOD
22
V IN
5
6
7
8
Q5
RJK0305DPB
4
4
Q7
RJK0305DPB
5
6
7
8
4
Q8
RJK0330DPB
0.22uH
L2
22uF
22uF
L2-
CIN6
CIN4
Q6
RJK0330DPB
0.22uH
L1-
22uF
22uF
L1
CIN5
CIN3
VIN
VIN
R67
10
0.001
RS2
0.001
RS1
R68
10
COUT1
100uF
6.3V
+ COUT11
OPT
S2-
S2+
S1-
S1+
SW2
SW1
TG2
TG1
BG2
BG1
+ COUT5
330uF
2.5V
VOUT
CIN1
+ 180uF
16V
VIN
1
2
E20
3
1
2
3
1
2
3
1
2
3
PGND
33
1
2
3
5
6
7
8
5
6
7
8
1
2
3
5
6
7
8
5
6
7
8
1
2
3
5
6
7
8
5
6
7
8
1
2
3
1
2
CLKOUT
S2-
S2+
S1-
S1+
VIN+
VIN-
GND
E13
SHT 2
GND
VO_SNS+
VO_SNS-
J4
VOUT
1.5V / 50A
J3
E6
J2
VIN
4.5V - 14V
E14
SW2
SW1
TG2
TG1
BG2
BG1
C32
4.7uF
16V
CIN2
+ 180uF
16V
E5
J1
LTC3856EUH
5
SW2
OPT
R51
OPT
S2-
R53
OPT
S1-
R47
OPT
OPT
R62
OPT
R61
L2-
S2+ SHT 1
L1-
S1+ SHT 1
JP5
IOSTEP
C53
100uF
6.3V
S
D
Q9
R73
0.005
G
R74
10K
SUD50N03-09P
1
LOAD STEP CKT
R72
0.005
C54
100uF
6.3V
VOUT
J5
E7
VOUT
IOSTEP
CLK
A ND RS E NS E 2. DO NOT ST UFF
R29 ,R30,R39 A ND R4 0
NOT E:
WHE N DCR S ENS ING IS IM PL EM E NT E D, SHORT RSE NSE 1
SHT 1 S2-
SHT 1 SW2
SHT 1 S1-
SHT 1 SW1
R45
2
3
4
5
SHT 1
OFF3
ON
2
VIN
BIAS 1
1uF
16V
C55
ITEMP
JP4
4
5
OPT
RNTC
OPT
R70
SHDN
3
6
1
R75
6.65K
FB
SW
BOOST
U2
LT1616ES6
VIN
OPT
C52
20K
R71
D4
B0530W
0.022uF
C56
A914BYW-150
L3 15uH
D3
CMDSH-3
OPTIONAL BIAS SUPPY
OPT
R69
ITEMP1
TEMPERATURE COMPENSATION NETWORK FOR DCR SENSING
2
1
OPTIONAL DCR SENSING
GND
2
SW1
C57
10uF
10V
0
R76
EXTVCC SHT 1
LTC3856EUH
6
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