Analog Devices DC2881A-A User manual

1
DEMO MANUAL DC2881A-A
Rev. 0
DESCRIPTION
LTC7050/LTC3884-1
2-Phase, Dual-Output Synchronous Buck
Converter with Power System Management
Demonstration circuit 2881A-A is a 2-phase dual-output,
high efficiency, high density, synchronous buck converter
with 7V to 14V input range. Each output can supply up
to 30A maximum load current with 1V output. The demo
board features the LT C
®
3884-1controller paired with the
LTC7050 dual smart power stage to provide a 2-phase
buck converter solution. The LTC3884-1 is a dual output
poly phase step-down controller with digital power sys-
tem management. The LTC7050 is a dual monolithic smart
power stage which integrates high speed drivers with low
resistance half-bridge power switches plus comprehensive
monitoring and protection circuitry in an electrically and
thermally optimized package. Please refer to the LTC3884-1
and LTC7050 data sheet for more detailed information.
DC2881A-A powers up to default settings and produces
power based on configuration resistors (or with the
All registered trademarks and trademarks are the property of their respective owners.
BOARD PHOTO
setting in its non-volatile memory) without the need for
any serial bus communication. This allows easy evalua-
tion 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
ADI’s I2C/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 here.
For more details and instructions of LTpowerPlay, please
refer to LTpowerPlay Quick Start Procedure.
Design files for this circuit board are available.
Figure1. Dual-Output LTC7050 + LTC3884-1/DC2881A-A Demo Circuit

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DEMO MANUAL DC2881A-A
Rev. 0
QUICK START PROCEDURE
DC2881A-A is easy to set up to evaluate the performance
of LTC7050 and LTC3884-1. Refer to Figure2 for the
proper measurement equipment setup and follow the
procedure below.
1. With power off, connect the input power supply (7-14V)
to VIN (J1) and GND (J2).
2. Connect the 1.0V output load (Initial load:no load)
between VOUT1 (J5) and GND (J6).
3. Connect the 1.0V output load (Initial load:no load)
between VOUT2 (J3) and GND (J4).
4. Connect the DMMs to the input and outputs. Set default
jumper position:
• JP1: ON
• JP6: 1.5V
• JP7: ON
• JP9: ON
• JP19: ON
• JP20: ON
The dual outputs can be configured to run separately or
together as a single output. The dynamic load is con-
nected to channel 1 by default. It can be connected to
channel 2 by changing R196 and R197. Refer to page 1
of schematic for more details.
• SW1 RUN1: ON
• SW2 RUN2: ON
5. Turn on the input power supply and check for the
proper output voltages. VOUT1 should be 1V ±0.5%
and VOUT2 should be 1V ±0.5%.
6. 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.
7. Connect the dongle and control the output voltages
from the GUI. See LTpowerPlay Quick Start Procedure
for details.
NOTE: When measuring the output or input voltage rip-
ple, 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.
When doing the load transient test, it is recommended
to use a function generator to generate a pulse (~3%
duty cycle with 10Hz~100Hz frequency). Then applying
this pulse to the EXT PULSE (E7) and GND (E8) turrets.
100mV/A is the ratio of the pulse voltage amplitude over
OUTPUT AND ONBOARD E-LOAD CONFIGURATION
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
PARAMETER CONDITION MIN TYP MAX UNITS
Input Voltage Range 7 12 14 V
Output Voltage, VOUT1/2 VIN = 7 to 14V, IOUT1/2 = 0A to 30A 0.6 1 1.8 V
Maximum Output Current, IOUT1/2 VIN = 7 to 14V, VOUT1/2 = 0.6V to 1.8V 30 A
Typical Efficiency of VOUT1/2 VIN = 12V, VOUT1/2 = 1V, IOUT1/2 = 30A 89.5 %
Default Switching Frequency 500 kHz

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DEMO MANUAL DC2881A-A
Rev. 0
the load current step. The maximum load current step
achievable is typically 25A. The dynamic circuit MOSFET
is off when EXT PULSE is floating or grounded. Apply
around 30mV of initial value to EXT PULSE to make the
MOSFET open before the pulse, so that the slew rate of
load current will follow the slew rate of EXT PULSE lin-
early. Refer to the table in the schematic file to optimally
route the voltage sense points during load transient test. It
is highly recommended to monitor the load voltage using
JP21, which is Kelvin connected to C227.
OUTPUT AND ONBOARD E-LOAD CONFIGURATION
Figure2. Proper Measurement Equipment Setup
Figure3. Measuring Output Voltage Ripple
+ –
VOUT GND
COUT
+
–
V
IN
IIN
POWER
SUPPLY
+
+
–
–
+
–
VOUT2
LOAD2
IOUT2
+
–
+
–
+
–
+
–
VOUT1
I
OUT1
+
–
LOAD1
dc2881a-a F02

4
DEMO MANUAL DC2881A-A
Rev. 0
Figure4. Demo Setup with PC
USB to I2C/PMBus
DONGLE DC1613A
LTC7050 DEMO BOARD
DC2881A-A
USB CABLE VIN
12-PIN (J14)
CONNECTOR DC2881A-A F04
LOAD1
VOUT1
LOAD2
VOUT2
INPUT POWER
SUPPLY
OUTPUT AND ONBOARD E-LOAD CONFIGURATION
Connecting a PC to DC2881A-A
You can use a PC to reconfigure the power management
features of LTC3884-1 such as:nominal VOUT, margin set
points, OV/UV limits, temperature fault limits, sequenc-
ing parameters, the fault log, fault responses, GPIOs
and other functionalities. The DC1613A dongle may be
plugged when VIN is present.
Efficiency measurement
Headers JP12 – JP16 are kelvin connected close to the
power stage for ideal efficiency measurement. For total
VOUT1/2 rail efficiency, including controller and SPS bias
conversion losses, use the setup shown in Figure5. Check
the following setup before measurement:
• JP 20 removed
• Bleeder resistors R85 and R200 removed
•Resistors R196 and R197 removed
To measure the efficiency of LTC7050, refer to the setup
in Figure6. In this setup, the controller, SPS, and IREF
biases are provided externally so as to not load the 12V
input. Additionally, the SPS bias power loss from the
external power source is added to the efficiency calcula-
tion as shown below.
η=
V
OUT
•I
OUT
VIN •IIN+(V
DRV •IDRV )
Optionally, FILTERED SW1 (JP12) can be used as the VOUT
measurement to obtain efficiency of just the SPS (without
inductor losses). JP12 is connected to the switching node
of channel 1 through a filter composed of R173 and C26
to obtain the average voltage at the switch node. Check
the following setup before measurement:
• JP19 and JP 20 both removed
• JP7 set to OFF
• JP9 set to OFF and JP6 removed
• Bleeder resistors R85 and R200 removed
•Resistors R196 and R197 removed
• R167 and R168 removed
•Apply a 5V power supply between turrets of E35 and
E36 for driving power. Measure the voltage and the
current for driving power loss.
•Apply a 5V power supply between turrets of E39 and
E36 for controller power.
•Apply a 1.5V power supply between turrets of E40 and
E41 for IREF voltage.

5
DEMO MANUAL DC2881A-A
Rev. 0
Figure5. Measuring Setup for DC2881 Efficiency
OUTPUT AND ONBOARD E-LOAD CONFIGURATION
I
IN
POWER
SUPPLY
+
+
–
–
+
–
I
OUT1
+
–
LOAD1
VOUT1
V
IN1
+–
+–
dc2881a-a F05

6
DEMO MANUAL DC2881A-A
Rev. 0
Figure6. Measuring Setup for LTC7050 Efficiency
OUTPUT AND ONBOARD E-LOAD CONFIGURATION
VOUT1
V
IN1
+–
+–
IIN
POWER
SUPPLY
+
+
–
–
+
–
I
OUT1
+
–
LOAD1
POWER
SUPPLY
+ –
POWER
SUPPLY
POWER
SUPPLY +
+
–
V
DRV
IDRV
+
–
+
–
dc2881a-a F06

7
DEMO MANUAL DC2881A-A
Rev. 0
Figure9. VOUT1 Load Transient Response at VIN = 12V, VOUT1 = 1V Figure10. VOUT2 Load Transient Response at VIN = 12V, VOUT2 = 1V
Figure7. DC2881 Efficiency vs. Load Current on VOUT1/2
DC2881 VOUT1/2 Efficiency vs Load at
VIN = 12V, fS= 500kHz, 1-Phase
Figure8. LTC7050 Efficiency vs. Load Current on VOUT1/2
LTC7050 VOUT1/2 Efficiency vs Load at
VIN = 12V, fS= 500kHz, 1-Phase
V
OUT
= 1V
V
OUT
= 1.8V
LOAD CURRENT (A)
0
3
6
9
12
15
18
21
24
27
30
70
75
80
85
90
95
100
EFFICIENCY (%)
dc2881a-a F07
L: PA2607.211NL
215nH, 0.29mΩ
L: PA2607.211NL
215nH, 0.29mΩ
V
OUT
= 1V
V
OUT
= 1.8V
LOAD CURRENT (A)
0
3
6
9
12
15
18
21
24
27
30
70
75
80
85
90
95
100
EFFICIENCY (%)
dc2881a-a F08
100µs/DIV
dc2881a-a F10
V
OUT2
(20MHz BW)
20mV/DIV
I
OUT2
0A TO 7.5A, 7.5A/µs
5A/DIV
100µs/DIV
dc2881a-a F09
V
OUT1
(20MHz BW)
20mV/DIV
I
OUT1
0A TO 7.5A, 7.5A/µs
5A/DIV
OUTPUT AND ONBOARD E-LOAD CONFIGURATION

8
DEMO MANUAL DC2881A-A
Rev. 0
Figure11. VOUT1 Voltage Ripple = 17.4mV at
VIN = 12V, VOUT1 = 1V, IOUT1 = 30A
Figure12. VOUT2 Voltage Ripple = 17.4mV at
VIN = 12V, VOUT2 = 1V, IOUT2 = 30A
Figure13. Thermal at VIN = 12V, VOUT1 = 1V, IOUT1 = 30A, VOUT2 = 1V, IOUT2 = 30A, TA= 22°C, No Airflow
2µs/DIV
V
OUT1
(20MHz BW)
20mV/DIV
dc2881a-a F11
2µs/DIV
V
OUT2
(20MHz BW)
20mV/DIV
dc2881a-a F12
OUTPUT AND ONBOARD E-LOAD CONFIGURATION

9
DEMO MANUAL DC2881A-A
Rev. 0
LTpowerPlay SOFTWARE GUI
Figure14. LTpowerPlay Main Interface
LTpowerPlay is a powerful Windows based development
environment that supports Analog Devices power sys-
tem management ICs and µModules, including LTM4675,
LTM4676, LTM4677, LTM4678, LTM4680, LTM4700,
LTC3880, LTC3882, LTC3883, LTC3884 and LTC3888-1.
The software supports a variety of different tasks. You
can use LTpowerPlay to evaluate Analog Devices ICs by
connecting to a demo board system. LTpowerPlay can
also be used in an offline mode (with no hardware pres-
ent) in order to build a multichip configuration file that
can be saved and reloaded at a later time. LTpowerPlay
provides unprecedented diagnostic and debug features.
It becomes a valuable diagnostic tool during board bring-
up to program or tweak the power management scheme
in a system, or to diagnose power issues when bringing
up rails. LTpowerPlay utilizes the DC1613A USB-to-I2C/
SMBus/PMBus controller to communicate with one of
many potential targets, including LTM4675, LTM4676,
LTM4677, LTM4678, LTM4680, LTM4700, LTC3880,
LTC3882, LTC3883, LTC3884 and LTC3888-1’s demo
system, or a customer board. The software also provides
an automatic update feature to keep the software current
with the latest set of device drivers and documentation.
The LTpowerPlay software can be downloaded from here.
To access technical support documents for ADI’s
Digital Power System Management Products, visit the
LTpowerPlay Help menu.

10
DEMO MANUAL DC2881A-A
Rev. 0
The following procedure describes how to use LTpowerPlay
to monitor and change the settings of LTC3884-1.
1. Download and install the LTpowerPlay GUI from here.
2. Launch the LTpowerPlay GUI.
a. The GUI should automatically identify the DC2881A-A.
The system tree on the left hand side should look like this:
b. A green message box shows for a few seconds in the
lower left-hand corner, confirming that LTC3884-1 is
communicating:
c. In the Toolbar, click the R (RAM to PC) icon to read the
RAM from the LTC3884-1. This reads the configuration
from the RAM of LTC3884-1 and loads it into the GUI.
d. If you want to change the output voltage to a different
value, like 1.2V. In the Config tab, type in 1.2 in the
VOUT_COMMAND box, like this:
Then, click the W (PC to RAM) icon to write these reg-
ister values to the LTC3884-1. After finishing this step,
you will see the output voltage will change to 1.2V.
LTpowerPlay QUICK START PROCEDURE