DEMO MANUAL DC1753A
LTC3880EUJ
Dual Phase Step-Down
DC/DC Controller with
Digital Power Management
Description
Demonstration circuit 1753A is a dual phase single-output,
synchronous buck converter featuring the LTC
®
3880EUJ,
a dual phase current mode controller with digital power
management. There are two versions of the board available:
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DC1753A-A: senses inductor current across a sense
resistor. Default switching Freq = 350kHz
DC1753A-B: senses inductor current with the inductor
DCR. Default switching Freq = 425kHz
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evaluation of the DC/DC converter aspects of the LTC3880.
To fully explore the extensive digital power management
features of the part, download the LTpowerPlay™ GUI
software 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 the LTpowerPlay for LTC3880 Quick Start Guide.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
LTpowerPlay is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Either version can be populated with the LTC3880EUJ-1,
which allows the user to provide bias power to the IC from
an external power supply.
The output voltage of the board can be programmed from
0.5V to 3.3V, with output current up to 40A. The factory
default setting for the output is 1.8V.
The DC1753A powers up to default settings and pro-
duces power based on configuration resistors without the
need for any serial bus communication. This allows easy
performance summary
SYMBOL
V
IN
V
OUT
V
OUT_ACCURACY
I
OUT
f
SW
, A
f
SW
, B
EFFICIENCY
PARAMETER
Input Supply Range
Output Voltage Range
Output Voltage Accuracy
Output Current Range
Factory Default Switching, Freq: A (R
SENSE
)
Factory Default Switching, Freq: B (DCR)
Peak Efficiency
Specifications are at T
A
= 25°C
CONDITIONS
I
OUT
= 0A to 20A, V
IN
= 6.5V to 24V
I
OUT
= 0A to 20A, V
IN
= 6.5V to 24V
V
OUT
for 0.5V to 3.3V
0
350
425
V
OUT
= 1.8V, See Figures 6 and 7
91.8
MIN
6.5
0.5
TYP
12
1.8
±0.5
40
MAX
24
3.3
UNITS
V
V
%
A
kHz
kHz
%
dc1753af
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DEMO MANUAL DC1753A
Quick start proceDure
Demonstration circuit 1753A makes it easy to evaluate
the performance of the LTC3880. Refer to Figure 3 for
proper measurement equipment setup and follow the
procedure below.
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 output voltage ripple by
touching the probe tip directly across the C20 or C23. See
Figure 5 for the proper scope probe technique.
1. Make sure jumpers are in the following positions:
JUMPER
JP1
JP3
JP4
JP5
POSITION FUNCTION
OFF
ON
OFF
C
Write Protection of LTC3880
LED Indicator
EXTVCC_DRV: External V
CC
for the LTC3880-1
GPIO0B to GPIO1B: Tie GPIOs Together
5. Turn on the RUN switch as desired.
6. Check for the correct output voltages. V
OUT
= 1.8V
± 0.5%.
NOTE: If there is no output, temporarily disconnect
the load to make sure that the load is not set too high.
7. 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.
8. Connect the dongle and control the output voltages
from the GUI. See next section for details.
CONNECTING A PC TO DC1753A
You can use a PC to reconfigure the power management
features of the LTC3880, 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
in regardless of whether or not V
IN
is present.
2. With power off, connect the input power supply to
V
IN
and GND. Connect active load to outputs.
3. Make sure RUN switch is OFF.
4. Turn on the power at the input.
.
NOTE: Make sure that the input voltage does not ex-
ceed 24V.
+12V
Power Supply
USB CABLE
12-PIN J10
USB to
I2C/PMBus Dongle
CONNECTOR
DC1613A
VIN
LTC3880
Demo Board
DC1753A
V
OUT
LOAD
dc1753a F01
Figure 1. Demo Setup with PC
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DEMO MANUAL DC1753A
Quick start proceDure
Plug the dongle into the correct connector. The dongle
can be hot plugged.
DC1613A
Connector
dc1753a F02
Figure 2. Dongle Connector Locations
RUN
SWITCH
V
V
VOUT
Load
SHUNT
A
V
POWER
SUPPLY
dc1753a F03
Figure 3. Dual Phase Single-Output Test Setup
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DEMO MANUAL DC1753A
Quick start proceDure
Combining DC1753A with Other Digital Power Demo
Boards
The DC1753A may be plugged together in a multiboard
array with other digital power boards using J7 and J8.
Measuring Efficiency
To accurately measure efficiency of any configuration, do
the following:
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To use the on-board LDO to drive INTVCC, make the
following modifications to the demo board:
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Set JP4 to ON so that U7 provides the drive to
INTVCC. U7 takes the place of the external power supply.
Install R60.
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To accurately measure efficiency of a demo board contain-
ing an LTC3880-1:
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Remove R65 (bleeder resistor on bottom side of board).
Set JP3 to OFF to disable the regulator that provides
power to LEDs.
Measure VIN across the input ceramic capacitor (C18,
C19). Measure VOUT across the output ceramic capaci-
tor (C24, C25).
Drive INTVCC from an external source through the
pin named: INTVCC/EXTVCC. Install R60, R65 if
installed
Set JP4 to OFF to disable U7.
Set JP3 to OFF to disable the regulator that provides
power to LEDs.
Measure VIN across the input ceramic capacitor (C18,
C19). Measure VOUT across the output ceramic capaci-
tor (C24, C25).
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Evaluating the LTC3880-1
For applications that require the highest possible ef-
ficiency, the LTC3880-1 allows the user to supply the
bias current and gate driver current from an external
power supply. Connect the power supply, 4.8V to 5.2V,
to the INTVCC/EXTVCC pin. Obtain a DC1753A with an
LTC3880-1 installed from your Linear Technology Field
Applications Engineer.
Measuring Output Ripple Voltage
An accurate ripple measurement may be performed by
using the configuration in Figure 5 across C20 or C23.
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DEMO MANUAL DC1753A
Quick start proceDure
JP3
JP4
R60
INTVCC/
EXTVCC
dc1753a F04
Figure 4. Jumper Locations: JP3, JP4, R60, INTVCC/EXTVCC Turret
+
V
OUT
C
OUT
GND
–
dc1753a F05
Figure 5. Measuring Output Voltage Ripple
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