DEMO MANUAL DC1989B-B
LTM4676AEY
Dual 13A or Single 26A µModule Regulator
with Digital Power System Management
3× LTM4676A, 75A
DESCRIPTION
Demonstration circuit 1989B-B is a high efficiency, high
density, µModule regulator with 4.5V to 17V input range.
The output voltage is adjustable from 0.5V to 4V, and it can
supply 75A maximum load current. The demo board has
three
LTM
®
4676A
µModule regulators, and the LTM4676A
is a dual 13A or single 26A step-down regulator with PMBus
power system management. Please see LTM4676A data
sheet for more detailed information
DC1989B-B powers up to default settings and produces
power based on configuration resistors without the need
for any serial bus communication. This allows easy evalu-
ation of the DC/DC converter. To fully explore the extensive
power system management features of the part, download
the GUI software LTpowerPlay™ onto your PC and use
LTC’s I
2
C/SMBus/PMBus dongle DC1613A to connect to
the board. LTpowerPlay allows the user to reconfigure the
part on the fly and store the configuration in EEPROM, view
telemetry of voltage, current, temperature and fault status
GUI Download
The software can be downloaded from:
http://www.linear.com/ltpowerplay
For more details and instructions of LTpowerPlay, please
refer to LTpowerPlay GUI for LTM4676A Quick Start Guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1989B-B
L,
LT, LTC, LTM, Linear Technology, the Linear logo, Dust Networks and Dust are registered
trademarks and LTpowerPlay is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
Figure 1. 3× LTM4676A; 75A DC1989B-B Demo Circuit
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DEMO MANUAL DC1989B-B
PERFORMANCE SUMMARY
PARAMETER
Input Voltage Range
Output Voltage, V
OUT0
Maximum Output Current, I
OUT0
Typical Efficiency
Default Switching Frequency
V
IN
= 4.5 to 17V, I
OUT0
= 0A to 75A
V
IN
= 4.5 to 17V, V
OUT
= 0.5V to 4V
V
IN
= 12V, V
OUT
= 1V, I
OUT
= 75A
Specifications are at T
A
= 25°C
CONDITION
VALUE
4.5V to 17V
0.5V to 4V, Default: 1V
75A
80%
350kHz
QUICK START PROCEDURE
Demonstration circuit 1989B-B is easy to set up to evaluate
the performance of the LTM4676AEY. Refer to Figure 2
for the proper measurement equipment setup and follow
the procedure below.
1. With power off, connect the input power supply to V
IN
(4.5V to 17V) and GND (input return).
2. Connect the 1V output load between V
OUT0
and GND
(Initial load: no load).
3. Connect the DVMs to the input and outputs. Set default
switch position: SW1: ON; SW2: ON.
4. Turn on the input power supply and check for the proper
output voltages. V
OUT0
should be 1V ±1%.
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.
6. Connect the dongle and control the output voltages
from the GUI. See “LTpowerPlay GUI for the LTM4676A
Quick Start Guide” for details.
Note: When measuring the output or input voltage ripple,
do not use the long ground lead on the oscilloscope probe.
See Figure 3 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.
Connecting a PC to DC1989B-B
You can use a PC to reconfigure the power management
features of the LTM4676A such as: nominal V
OUT
, margin
set points, OV/UV limits, temperature fault limits, sequenc-
ing parameters, the fault log, fault responses, GPIOs and
other functionality. The DC1613A dongle may be plugged
when V
IN
is present.
NUMBER OF LTM4676/LTM4676A µMODULE
REGULATORS ON THE BOARD
1× LTM4676
1× LTM4676A
1× LTM4676
2× LTM4676A
3× LTM4676A
4× LTM4676A
1× LTM4676 (+ 3× LTM4620A)
1× LTM4676 (+ 3× LTM4630)
1× LTM4676A (+ 3× LTM4620A)
1× LTM4676A (+ 3× LTM4630)
Table 1. LTM4676/LTM4676A Demo Cards for Up to 130A Point-of-Load Regulation
MAXIMUM OUTPUT CURRENT
13A, 13A
13A, 13A
26A
50A
75A
100A
100A
130A
100A
130A
NUMBER OF OUTPUT VOLTAGES
2
2
1
1
1
1
1
1
1
1
DEMO BOARD NUMBER
DC1811A/DC1811B-A
DC1811B-B
DC2087A
DC1989B-A
DC1989B-B
DC1989B-C
DC2106A-A
DC2106A-B
DC2106B-A
DC2106B-B
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DEMO MANUAL DC1989B-B
QUICK START PROCEDURE
Figure 2. Proper Measurement Equipment Setup
Figure 3. Measuring Output Voltage Ripple
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DEMO MANUAL DC1989B-B
QUICK START PROCEDURE
Figure 4. Demo Setup with PC
Efficiency vs Load Current
100
V
OUT0
= 1V
90
EFFICIENCY (%)
80
70
60
V
IN
= 5V
V
IN
= 12V
0 5
15
25
35
45
55
65
75
LOAD CURRENT (A)
50
Figure 5. Efficiency vs Load Current at V
IN
= 5V and V
IN
= 12V
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DEMO MANUAL DC1989B-B
QUICK START PROCEDURE
V
OUT0
(20MHz BW) [50mV/DIV]
V
OUT0
(20MHz BW) [10mV/DIV]
37.5A TO 75A LOAD STEP
Figure 6. Output Voltage V
OUT0
vs Load Current
(V
OUT0
RANGE = 1)
Figure 7. Output Voltage Ripple at V
IN
= 12V,
V
OUT0
= 1V, I
OUT0
= 75A
Figure 8. Thermal Performance at V
IN
= 12V, V
OUT0
= 1V, I
OUT0
= 75A, T
A
= 23.8°C, Air Flow 200LFM
14
TOTAL CURRENT READBACK (A)
12
PHASE CURRENT (A)
10
8
6
4
2
0
–2
I
OUT_PHASE#1
I
OUT_PHASE#2
I
OUT_PHASE#3
I
OUT_PHASE#4
I
OUT_PHASE#5
I
OUT_PHASE#6
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
LOAD CURRENT (A)
80
70
60
50
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
LOAD CURRENT (A)
Figure 9. Current Sharing at V
IN
= 12V, V
OUT0
= 1V
(Based on the Current Readback)
Figure 10. Total Current Readback vs Load
Current at V
IN
= 12V, V
OUT0
= 1V
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