DC1347B - Demo Manual

DEMO CIRCUIT 1347B
LTC3633
QUICK START
GUIDE
DESCRIPTION
LTC3633
DUAL CHANNEL 3A15V MONOLITHIC
SYNCHRONOUS STEP-DOWN REGULATOR
BOARD
Demonstration circuit DC1347 is a dual output regulator
consisting of two constant-frequency step-down converters, based on the LTC3633 monolithic dual channel synchronous buck regulator. The DC1347 has an input voltage range of 3.6V to 15V, with each regulator capable of
delivering up to 3A of output current. The DC1347 can
operate in either Burst Mode or forced continuous
mode. In shutdown, the DC1347 can run off of less than
15 uA total. The DC1347 is a very efficient circuit: over
90% for either circuit. The LTC3633 comes in a 28 Pin
QFN or leaded package, which each having an exposed
pad on the bottom-side of the IC for better thermal performance. These features, plus a programmable operating
frequency range from 500 kHz to 4 MHz (2 MHz switching frequency with the RT pin connected to INTVcc),
make the DC1347 demo board an ideal circuit for use industrial or distributed power applications. Gerber files
for this circuit are available. Call the LTC Factory.
QUICK START PROCEDURE
The DC1347 is easy to set up to evaluate the
performance of the LTC3633. For a proper
measurement equipment configuration, set up
the circuit according to the diagram in Figure
1.
NOTE: When measuring the input or output
voltage ripple, 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 the proper
scope probe technique in figure 2.
Please follow the procedure outlined below for
proper operation.
1. Connect the input power supply to the Vin
and GND terminals. Connect the loads between the Vout and GND terminals. Refer to
figure 1 for the proper measurement equipment setup.
Before proceeding to operation, insert jumper
shunts XJP1 and XJP2 into the OFF positions
of headers JP1 and JP2, shunt XJP11 into the
ON position (180°out-of-phase) of PHASE
header JP11, shunts XJP3 and XJP4 into the
soft-start (ss) positions of headers JP3 and
JP4, shunt XJP8 into the forced continuous
mode (FCM) position of MODE header JP8,
shunt XJP14 into the 1 MHz position of the frequency (FREQ) header JP14, shunts XJP12
and XJP13 into the external (EXT) compensation positions of headers JP12 and JP13, and
shunt XJP6 into the Vout1 voltage options of
choice of header JP6: 1.2V, 1.5V, or 1.8V, and
a shunt into the Vout2 voltage option of choice:
2.5V (header JP15), 3.3V (header JP5), or 5V
(header JP7).
2. Apply 5.5V at Vin. Measure both Vouts;
they should read 0V. If desired, one can
measure the shutdown supply current at this
point. The supply current will be less than 100
uA in shutdown.
3. Turn on Vout1 and Vout2 by shifting shunts
XJP1 and XJP2 from the OFF positions to the
ON positions. Both output voltages should be
within a tolerance of +/- 2%.
4. Vary the input voltage from 5.8V (the min.
Vin is dependent on Vout) to 15V, and the load
currents from 0 to 3A. Both output voltages
should be within +/- 4% tolerance.
1
LTC3633
5.
Set the load current of both outputs to 3A and the input voltage to 15V, and then measure each output ripple voltage (refer to figure 2 for proper measurement technique); they should each measure less than 30 mVAC. Also,
observe the voltage waveform at either switch node (pins 23 & 24 for reg.1 and 13 & 14 for reg.2) of each regulator. The switching frequencies should be between 800 kHz and 1.2 MHz (T = 1.25 us and 0.833 us). To realize 2
MHz operation, change the shunt position on header JP14. In all cases, both switch node waveforms should be
rectangular in shape, and 180°out-of-phase with each other. Change the shunt position on header JP11 to set
the switch waveforms in phase with respect to each other. To operate the ckt.s in Burst Mode, change the
shunt in header JP8 to the Burst Mode position. When finished, insert shunts XJP1 and XJP2 to the OFF position(s) and disconnect the power.
Warning - If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the
operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, a small tantalum capacitor (for
instance, AVX part # TPSY226M035R0200) is inserted on the pads between the input power and return terminals on the bottom of the
demo board. The (greater) ESR of the tantalum will dampen the (possible) ringing voltage due to the use of long input leads. On a
normal, typical PCB, with short traces, this capacitor is not needed.
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITIONS
VALUE
Minimum Input Voltage
3.6V
Maximum Input Voltage
15V
Run
RUN Pin = GND
Shutdown
RUN Pin = VIN
Operating
1.2V ±4% (1.152V – 1.248V)
Output Voltage VOUT1
VIN = 3.6V to 15V, IOUT1 = 0A to 3A
1.5V ±4% (1.44V - 1.56V)
1.8V ±4% (1.728V – 1.872V)
Typical Output Ripple VOUT1
Output Regulation VOUT1
VIN = 12V, IOUT1 = 3A (20 MHz BW)
< 30mVP–P
Line
±1%
Load
±1%
2.5V ±4% (2.4V – 2.6V)
3.3V ±4% (3.168V – 3.432V)
5V ±4% (4.8V – 5.2V)
Output Voltage VOUT2
VIN = 3.6V to 15V, IOUT2 = 0A to 3A
Typical Output Ripple VOUT2
VIN = 12V, IOUT2 = 3A (20 MHz BW)
< 30mVP–P
Line
±1%
Load
RT Pin connected to 324k
RT Pin = INTVCC
Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 1 MHz
Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 1 MHz
Channel 1: Vin = 12V, Vout1 = 1.8V, Fsw = 2 MHz
Channel 2: Vin = 12V, Vout2 = 3.3V, Fsw = 2 MHz
Phase Pin = INTVCC
Phase Pin = GND
±1%
1 MHz
2 MHz
Iout1 = 1.3A
Iout2 = 850 mA
Iout1 = 800 mA
Iout2 = 500 mA
Out-of-Phase
In Phase
3.3V
2.5V
Output Regulation VOUT2
Nominal Switching Frequencies
Burst Mode Operation
Phase
INTVCC
V2P5
2
LTC3633
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
3
LTC3633
Figure 3. VOUT1 Load Step Response
VIN = 12V, VOUT1 = 1.8V, 3A Load Step (0.1A <-> 3A)
Forced Continuous Mode FSW = 2 MHz
External Compensation: Rith = 13k, Cith = 220 pF
Trace 3: Output Voltage (100mV/div AC)
Trace 4: Output Current (1A/div)
4
LTC3633
Figure 4. VOUT2 Load Step Response
VIN = 12V, VOUT2 = 3.3V, 3A Load Step (0.1A <-> 3A)
Forced Continuous Mode FSW = 2 MHz
External Compensation: Rith = 13k, Cith = 220 pF
Trace 3: Output Voltage (100mV/div AC)
Trace 4: Output Current (1A/div)
5
LTC3633
95
90
Vo2 = 3.3V
85
Efficiency (%)
Vo1 = 1.8V
80
75
70
Vin = 12V
fsw = 1 MHz
Burst Mode
L1 =1 uH
L2 = 2.2 uH
2020BZ Vishay
65
60
0.00E+00
5.00E-01
1.00E+00
1.50E+00
2.00E+00
Load Current (A)
Figure 5. LTC3633 DC1347 Efficiency
6
2.50E+00
3.00E+00
E2
E15
E6
E4
E1
E16
[1]
+ CIN6
22uF
35V
7343
[1]
+ CIN5
22uF
35V
7343
CIN4
47uF
16V
OPT
1210
5
6
CIN3
47uF
16V
OPT
1210
3
4
VIN
VIN
JP6
1
2
1.8V
1.5V
CIN2
47uF
16V
1210
INTVCC
1M
D1
INT
EXT
10pF
CFFW1
OPT
2MHz
(INT.)
1MHz
JP12
3
2
1
L1 1.0uH
3
3
0.1uF
CBST1
R1 1M
JP3
JP14
2. ALL RESISTOR AND CAPACITOR CASE SIZE ARE 0402.
VIN
11
9
12
14
13
17
18
LT C3633EUFD
U1
ITH2
FB2
VON2
SW2
SW2
BOOST2
V2P5
RUN2
6
RPG2
100K
R2
2.2uH
VIN
3
2
1
TRACK
SS
CC2
10pF
OPT
INTVCC
220pF
CITH2
RITH2
13K
1%
6
D2
3
2
1
JP8
JP13
ITH2
10pF
R4
84.5K
1%
INTVCC
5
3
1
R8 11.5K 1%
R6 18.7K 1%
5V
3.3V
2.5V
COUT4
22uF
6.3V
1206
VOUT2
RTR4
OPT
JP7
JP5
CLDO
1uF
OPT
R11
10k
COUT6
10uF
6.3V
0805
JP15
RTR2 0
FCM (FORCED CONTINUOUS MODE)
SY NC
COUT2
22uF
6.3V
1206
C2P5
1uF
R10 26.7K 1%
BURST MODE
INTVCC
INT
EXT
OFF
ON
CFFW2
OPT
JP2
RUN2
MODE
VISHAY
IHLP-2020BZER2R2M01
0.1uF
L2
JP4
CBST2
1M
3
2
1
TRACK/SS2
4
RT
324K
1%
VIN
CTR2
4700pF
2
220pF
CITH1
ITH1
FB1
VON1
SW1
SW1
BOOST1
PHMODE
RUN1
1uF
1uF
CVCC
CVCC1
3
INTVCC
INTVCC
RITH1
13K
1%
26
28
25
23
24
20
2
3
RPG1
100K
CTR1
4700pF
27
2
1
FREQ
CC1
10pF
OPT
VISHAY
IHLP-2020BZER1R0M01
JP1
ITH1
OFF
2
VIN
TRACK
[1] CIN5 AND CIN6 ARE INSERTED ON DC1347 TO DAMPEN THE (POSSIBLE) RINGING VOLTAGE DUE
TO THE USE OF LONG INPUT LEADS. ON A NORMAL, TYPICAL PCB, WITH SHORT TRACES,
CIN5 AND CIN6 ARE NOT NEEDED.
R9 14.7K 1%
R7 19.6K 1%
R3
29.4K
1%
R5 29.4K 1%
COUT1
22uF
6.3V
1206
1.2V
CIN1
47uF
16V
1210
VOLTAGE SELECT
COUT5
10uF
6.3V
0805
JP11
3
2
1
ON
1
RPHMDE
RUN1
INTVCC
PHASE
COUT3
22uF
6.3V
1206
OFF
ON
RTR3
OPT
VOUT1
RTR1 0
NOTES: UNLESS OTHERWISE SPECIFIED,
V51 - V6.3
VIN2
V51 - V6.3
VIN1
GND
GND
3A
VOUT1
PGOOD1
TRACK1
E9
2
1
TRACK/SS1
SS
1
PGOOD1
21
22
PVIN1
PVIN1
RT
5
INTVCC
INTVcc
19
GND
7
TRACK/SS1
E10
TRACK/SS2
10
PGND
29
8
PGOOD2
15
16
PVIN2
PVIN2
MODE/SYNC
4
E12
E14
E7
E5
E13
E3
E8
E11
VOUT2
V2P5
GND
PGOOD2
TRACK2
SYNC
GND
GND
A3
INTVCC
LTC3633
7
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