Analog Devices ADI Power LTC7871 Quick setup guide

1
DEMO MANUAL DC2886A
Rev. A
DESCRIPTION
LTC7871/LTC7060
48V-to-14V, 6-Phase, 2.5kW Bidirectional Supply/
Charger
All registered trademarks and trademarks are the property of their respective owners.
Demonstration circuit 2886A is a high power, high effi-
ciency six-phase bidirectional converter featuring the
LTC
®
7871 and LTC7060. The terminals labeled VHIGH
and VLOW are either inputs or outputs depending on the
direction of power flow. When the switch at SW1 is in the
BUCK position, VLOW provides a 14V output and VHIGH is
the input with a range of 30V to 70V. When the switch
is in the BOOST position, VHIGH provides a 48V output
and VLOW is the input with a range of 10V to 14V. The
maximum VLOW current is 180A in both directions. The
maximum output power is 2.5kW when operating as a
buck within the input voltage range. When operating as
a boost, the maximum output power is 2.4kW when the
input voltage is 14V. External airflow is required when
operating at maximum power. The MOSFETs in each
phase are driven by the LTC7060 half bridge driver. Each
LTC7060 gate driver is placed next to the MOSFETs and
receives a PWM signal from the LTC7871.
The inductor current for each phase is sensed with a low
1mΩ sense resistor using a highly accurate AC/DC cur-
rent sensing architecture with low power dissipation. The
LTC7871’s constant-current loop provides a DC current
limit for the current flowing in or out of the V
LOW
terminal
depending on the state of the BUCK pin. This current can
be programmed with the SETCUR pin and monitored with
the IMON pin.
The DC2886A provides a SPI compatible serial port. With
a DC2026C (Linduino
®
One) demo board and QuikEval™
software on a host computer, the user can:
• Margin the regulated VLOW or VHIGH up or down.
•Margin the DC current limit up or down with the
SETCUR pin.
•Adjust the frequency spread and modulation rate of
the spread spectrum circuit, when spread spectrum
isenabled.
•Monitor the operational status and faults of
theLTC7871.
Additional features of the DC2886A include:
• Pin selectable light load operating modes
– Buck:FCM, pulse-skipping and Burst Mode
®
Operation
– Boost: FCM and pulse-skipping
• SYNC and CLKOUT pins
•Optional jumper to enable spread spectrum modulation
• RUN, FAULT, PGOOD and PWNEN pins
•BUCK pin to externally control the direction of
powerflow
• Footprint for an optional heatsink
Design files for this circuit board are available.

2
DEMO MANUAL DC2886A
Rev. A
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Buck Mode
VHIGH Supply Range 30 48 70 V
VLOW Output Voltage 13.6 14.0 14.4 V
ILOW(MAX) 180 A
fSWITCH Operating Frequency 150 kHz
Efficiency VHIGH = 48V
ILOW = 180A
400LFM Airflow
97.5 %
Boost Mode
VLOW Supply Range 10 12 14 V
VHIGH Output Voltage 46.9 48.4 49.8 V
IHIGH(MAX) VLOW = 14V
VLOW = 12V
VLOW = 10V
51
44
35
A
fSWITCH Operating Frequency 150 kHz
Efficiency VLOW = 14V
IHIGH = 51A
400LFM Airflow
97.2 %
BOARD PHOTO

3
DEMO MANUAL DC2886A
Rev. A
Figure1. Proper Measurement Equipment Setup for BUCK Mode
QUICK START PROCEDURE
Instructions for operating the DC2886A are below.
NOTE:Use short and thick cables with a sufficient current
rating. If batteries are used when testing the demo board,
always use suitable circuit breakers for safety.
Constant-Voltage (CV) Buck Mode
1. Refer to the connection diagram shown in Figure1.
2. Place SW1 in the BUCK position.
3. Connect the input supply to VHIGH and the load to
VLOW. Next connect the voltmeters to monitor VHIGH
and VLOW.
4. Turn on the V
HIGH
supply. With no load, slowly increase
the VHIGH supply until VHIGH reaches 30V. At this point,
14V should appear on VLOW. The regulation limits are
shown in the Performance Summary section.
5. Next, increase VHIGH to 48V. Recheck the regulation.
6. Apply load up to 180A across VLOW. Recheck
theregulation.
7. After the basic performance has been verified, the
other aspects of performance can be measured
andobserved.
NOTE:
MONITOR VHIGH ACROSS
C54 OR C61 FOR ACCURATE
EFFICIENCY MEASUREMENTS.
NOTE:
MONITOR VLOW ACROSS
C72 OR C66 FOR ACCURATE
EFFICIENCY MEASUREMENTS.
–
+
–
+
IHIGH
ILOW
VHIGH
SUPPLY
LOAD
–
+
PLACE SW1 IN BUCK POSITION
VLOW
VHIGH
+–
dc2886a F01

4
DEMO MANUAL DC2886A
Rev. A
5. Next, increase VLOW to 14V. Recheck the regulation.
6. Apply load up to 51A across VHIGH. Recheck
theregulation.
7. After the basic performance has been verified, the
other aspects of performance can be measured
andobserved.
Note:When measuring the output voltage or input
voltage ripple, be sure to measure directly across an
output or input capacitor. Do not use the ground lead
on the oscilloscope probe. See Figure3.
Constant-Voltage (CV) Boost Mode
1. Refer to the connection diagram in Figure2.
2. Place SW1 in the BOOST position.
3. Connect the input supply to VLOW and the load to
VHIGH. Next connect the voltmeters to monitor VLOW
and VHIGH.
4. Turn on the VLOW supply. With no load, slowly increase
the VLOW supply until VLOW reaches 10V. At this point,
48V should appear on the output. The regulation limits
are shown in the Performance Summary section.
Figure2. Proper Measurement Equipment Setup for BOOST Mode
NOTE:
MONITOR VHIGH ACROSS
C54 OR C61 FOR ACCURATE
EFFICIENCY MEASUREMENTS.
NOTE:
MONITOR VLOW ACROSS
C72 OR C66 FOR ACCURATE
EFFICIENCY MEASUREMENTS.
–
+
IHIGH
ILOW
PLACE SW1 IN BOOST POSITION
VLOW
VHIGH
+–
dc2886a F02
LOAD
–
+
–
+
VLOW
SUPPLY
QUICK START PROCEDURE

5
DEMO MANUAL DC2886A
Rev. A
Constant-Current (CC) Mode
The DC2886A can operate as a constant-current source
when operating either as a buck or a boost. There are the
setup instructions.
1. For buck operation, setup DC2886A as shown in
Figure 1. For boost operation, setup DC2886A as
shown in Figure2. The load will need to have a con-
stant-voltage mode.
2. If the converter is setup as a buck, the CV setting for
the load should be 10V or less. If the converter is setup
as a boost, the CV setting should be 40V or less.
3. Connect a bench voltage source to the SETCUR pin as
shown in Figure4. This could be either a DC voltage
or the output of a pulse generator.
4. Monitor SETCUR, IMON and ILOW or IHIGH while adjust-
ing the SETCUR voltage. Figure17 shows an example.
For buck to boost or boost to buck transition testing,
setup the DC2886A as shown in Figure5.
QUICK START PROCEDURE
+ –
VOUT GND
COUT
Figure3. How to Measure the Output or Input Voltage Ripple
DC VOLTAGE OR
PULSE
GENERATOR
dc2886a F04
+
–
DMM OR
OSCILLOSCOPE
ILOW(MAX) = SETCUR/(K • RSNS) • # PHASES
GIVEN: K = 20 (ILIM = ¾ V5), RSNS = 1mΩ, # PHASES = 6
ILOW(MAX) = SETCUR • 300
IMON = ILOW/300 + 1.25V
ILOW IS POSITIVE DURING BUCK OPERATION, NEGATIVE DURING BOOST OPERATION
Figure4. Using SETCUR Pin to Control DC Current

6
DEMO MANUAL DC2886A
Rev. A
External Bulk Capacitance
Additional bulk capacitance may be required across the
input for either power flow direction, especially if operating
at or near full load with supply cables longer than 2 feet.
Depending on the supply cable inductance, when operat-
ing as a boost, an extra 10mF of bulk capacitance across
VLOW may be required. When operating as a buck, an extra
1mF of bulk capacitance across VHIGH may be required.
For buck/boost transition testing, this extra capacitance
should be added across both inputs. Likely choices for
the external capacitance are either aluminum electrolytic
or super capacitors with sufficient voltage rating.
Thermal Considerations
With full continuous load on the output in either direc -
tion at room temperature ambient, 400LFM of airflow
is recommended with full load. All the efficiency curves
and thermal images shown in the Typical Performance
Characteristics section were taken with this amount of
airflow from an adjustable external fan. To further aid with
thermals, the DC2886A has three optional footprints for
a board mounted heatsink and DC fan. The heatsinks are
placed at HS1–HS3 on the bottom layer underneath the
power stages for phases 1and 2, phases 3 and 4 and
phases 5 and 6. The DC fan is mounted over the heat-
sink. Terminals labeled V
FAN1
–V
FAN3
provide the fans with
power from VLOW. See Figure6 for details.
Figure5. Typical Setup for the Buck/Boost Transition Test
DC2886A
VLOW
dc2886a F05
VHIGH
GND
SETCUR
BUCK
+
–
+
E-LOAD
CV MODE
VLOW
SUPPLY
+
VHIGH
SUPPLY
E-LOAD
CV MODE
PULSE
GENERATOR
VSETCUR
IPROBE CLOW
~10mF
CHIGH
~1mF
QUICK START PROCEDURE
Figure6. DC2886A Optional Heatsink and Fan Mounting Assembly Drawing (Fan May Be
Powered from VLOW by Plugging Its Connector to the Terminals Labeled VFAN1 to VFAN3)
4–40 × 3/8” STANDOFF
4–40 × 1/2” SCREW
4–40 ×3/8” SCREW INSULATING WASHER
HEATSINK
60mm ×10mm FAN
INSULATING WASHER
PCB
COMPONENTS
THERMALLY CONDUCTIVE
INSULATION
SUGGESTED COMPONENTS:
FAN: DELTA ELECTRONICS EFB0612HHA
HEATSINK: AAVID THERMALLOY 241204B92200G

7
DEMO MANUAL DC2886A
Rev. A
SPI Interface
To control or monitor the DC2886A from QuikEval on a
host computer, follow these steps:
1. Refer to Figure7.
2. If QuikEval is already installed, download the latest
software by selecting Tools →Update Program. If
QuikEval is not installed, then click on this link.
3. Connect J6 of the DC2886A to a DC2026C with a 14-pin
ribbon cable.
4. Connect the DC2026C to the host computer with a
USBcable.
QUICK START PROCEDURE
5. Refer to the demo manual of the DC2026C for further
details.
6. Apply a voltage within the specified input range to
either VHIGH or VLOW depending on the direction of
power flow.
7. Start QuikEval on the host computer.
8. Use QuikEval to monitor and control the LTC7871. The
LTC7871 QuikEval GUI is shown in Figure8. The dash-
board is on the left and an optional design tool is on
the right.
a. To read the status, either press the Read Once button
or the Read Continuously button in the dashboard.
Figure7. Connecting the DC2886A to a Host Computer (Refer to DC2026C Demo Manual for More Details)
Figure8. LTC7871 QuikEval GUI (Design Tool Only Available When Enabled from the File Menu)
14-PIN
RIBBON
CABLE
USB
CABLE DC2026C*
(Linduino ONE)
HOST
COMPUTER/
QuikEval
dc2886a F07
DC2886A
NOTES:
POWER MUST BE APPLIED TO VLOW OR VHIGH
TO ALLOW COMMUNICATION BETWEEN THE
DC2886A AND THE DC2026C.
*THE DC2886A COULD BE CONNECTED TO EITHER
THE DC2026C OR DC590B, BUT THE DC2026C
IS PREFERRED FOR FUTURE USE.

8
DEMO MANUAL DC2886A
Rev. A
b. QuikEval can margin VLOW, VHIGH and the DC ILOW
current limit up or down by writing to the register
which controls the current source digital to ana-
log converter (IDAC) for the VFB
LOW
, VFB
HIGH
or
SETCUR pins. To use this feature, make sure the
Read Continuously button is not enabled. This but-
ton is gray when not enabled.
c. An optional design tool can be enabled from the
File menu. It calculates the required IDAC value to
margin the V
LOW
, V
HIGH
or DC I
LOW
current limit
to a given value. To use this tool, enter the values
for the feedback divider or SETCUR resistor and
then enter the value for the desired VLOW, VHIGH
or IL(MAX) which is the DC ILOW current limit. The
design tool will then provide the calculated IDAC
value. To update the LTC7871’s registers, enter the
calculated IDAC values in the dashboard and then
press the respective Update button.
QUICK START PROCEDURE
TYPICAL PERFORMANCE CHARACTERISTICS
LOAD CURRENT (A)
0
EFFICIENCY (%)
93
99
97
95
100
98
96
94
100 18060 140
dc2886a F09
20080 16040 12020
AIRFLOW = 400LFM
30VHIGH
48VHIGH
70VHIGH
VLOW = 14V
LOAD CURRENT (A)
0
EFFICIENCY (%)
93
99
97
95
100
98
96
94
100 18060 140
dc2886a F10
20080 16040 12020
AIRFLOW = 400LFM
VLOW ADJUSTED THROUGH
SPI INTERFACE
14VLOW
12VLOW
10VLOW
VHIGH = 48V
LOAD CURRENT (A)
0
EFFICIENCY (%)
93
99
97
95
100
98
96
94
25 4515 35
dc2886a F11
50 5520 4010 305
14VLOW
12VLOW
10VLOW
AIRFLOW = 400LFM
VHIGH = 48V
LOAD CURRENT (A)
0
EFFICIENCY (%)
93
99
97
95
100
98
96
94
25 4515 35
dc2886a F12
50 5520 4010 305
40VHIGH
48VHIGH
56VHIGH
AIRFLOW = 400LFM
VHIGH ADJUSTED THROUGH
SPI INTERFACE
VLOW = 12V
|ILOW| (A)
0
POWER LOSS (W)
10
70
50
30
80
60
40
20
0100 18060 140
dc2886a F13
20080 16040 12020
AIRFLOW = 400LFM
ILOW+(BUCK)
ILOW–(BOOST)
BOOST
BUCK
Figure9. Efficiency While Operating
as a BUCK, Input Voltage Varied,
Converter Setup for FCM, External
Fan Is Used
Figure10. Efficiency While
Operating as a BUCK, Output Voltage
Varied, Converter Setup for FCM,
External Fan Is Used
TA= 25°C, unless otherwise noted.
Figure11. Efficiency While
Operating as a BOOST, Input
Voltage Varied, Converter Setup for
FCM, External Fan Is Used
Figure12. Efficiency While
Operating as a BOOST, Output
Voltage Varied, Converter Setup for
FCM, External Fan Is Used
Figure13. Buck vs Boost Power
Loss Comparison, VHIGH = 48V,
VLOW = 14V, External Fan Is Used

9
DEMO MANUAL DC2886A
Rev. A
TYPICAL PERFORMANCE CHARACTERISTICS
dc2886a F14
AIRFLOW
VHIGH
VLOW
PH6
PH1
L
QB
QT
dc2886a F15
AIRFLOW
VHIGH
VLOW
PH6
PH1
L
QB
QT
dc2886a F16
IMON
200mV/DIV
SETCUR
200mV/DIV
VLOW
10V/DIV
ILOW
50A/DIV
50A
1.28V
10A
20ms/DIV
Boost–to–Buck Transition
50µs/DIV
BUCK
5V/DIV
dc2886a F17
VLOW
2V/DIV
IL
5A/DIV
VHIGH
2V/DIV
VSW
100V/DIV
Figure14. Thermal Image While Operating as a BUCK,
VHIGH = 48V, VLOW = 14V, Load = 180A, Airflow = 400LFM,
External Fan Is Used, DRVCC = 10V, fSWITCH = 150kHz, TA= 23°C
Figure15. Thermal Image While Operating as a BOOST,
VLOW = 14V, VHIGH = 48V, Load = 51A, Airflow = 400LFM,
External Fan Is Used, DRVCC = 10V, fSWITCH = 150kHz, TA= 23°C
Figure16. ILOW Stepped from 10A to 50A with the SETCUR Pin
While Operating in CC BUCK Mode, VHIGH = 48V, VLOW Clamped
at 10V with Electronic Load, 2× 10mF Bulk Capacitance Across
VLOW. ILIM = Float
Figure17. Boost to Buck Transition of the DC2886A Demo Board,
ILOW = 0A, VLOW Clamped at 10V, VHIGH Clamped at 40V

10
DEMO MANUAL DC2886A
Rev. A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 R7 RES., 10k , 5%, 1/10W, 0603 SAMSUNG, RC1608J103CS
YAGEO, RC0603JR-0710KL
2 1 R10 RES., 1k , 5%, 1/10W, 0603 SAMSUNG, RC1608J102CS
YAGEO, RC0603JR-071KL
3 6 R67, R400, R403, R406, R409, R412 RES., 1Ω, 1%, 1/10W, 0603 YAGEO, RC0603FR-071RL
4 1 R36 RES., 48.7k , 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF4872V
VISHAY, CRCW060348K7FKEA
5 6 R39, R40, R43, R49, R93, R103 RES., 1.5k , 1%, 1/10W, 0603 NIC, NRC06F1501TRF
VISHAY, CRCW06031K50FKEA
6 8 R18, R123, R398, R399, R402,
R405, R408, R411
RES., 100k , 1%, 1/10W, 0603, AEC-Q200 NIC, NRC06F1003TRF
PANASONIC, ERJ3EKF1003V
VISHAY, CRCW0603100KFKEA
7 1 R430 RES., 12.7k , 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF1272V
VISHAY, CRCW060312K7FKEA
8 6 RS1, RS2, RS3, RS4, RS5, RS6 RES., 0.001Ω, 1%, 1W, 2512, METAL, SENSE,
AEC-Q200
VISHAY, WSL25121L000FEA
9 5 R8, R9, R418, R428, R469 RES., 10k , 1%, 1/10W, 0603, AEC-Q200 KOA SPEER, RK73H1JTTD1002F
PANASONIC, ERJ3EKF1002V
VISHAY, CRCW060310K0FKEA
VISHAY, CRCW060310K0FKEB
10 2 R454, R455 RES., 0.01Ω, 1%, 1/2W, 1210, SENSE, AEC-Q200 YAGEO, RL1210FR-070R01L
11 1 R431 RES., 499k , 1%, 1/8W, 0805, AEC-Q200 NIC, NRC10F4993TRF
PANASONIC, ERJ6ENF4993V
VISHAY, CRCW0805499KFKEA
12 1 R29 RES., 2.2Ω, 1%, 1/4W, 1206, AEC-Q200 VISHAY, CRCW12062R20FKEA
13 1 R44 RES., 37.4k , 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ-3EKF3742
PANASONIC, ERJ3EKF3742V
VISHAY, CRCW060337K4FKEA
14 1 R1 RES., 3.01MΩ, 1%, 1/8W, 0805, AEC-Q200 VISHAY, CRCW08053M01FKEA
15 1 R2 RES., 210k , 1%, 1/8W, 0805, AEC-Q200 VISHAY, CRCW0805210KFKEA
16 6 R31, R32, R53, R65, R97, R98 RES., 16.9k , 1%, 1/8W, 0805, AEC-Q200 STACKPOLE ELECT., INC., RMCF0805FT16K9
VISHAY, CRCW080516K9FKEA
17 6 R419, R420, R421, R422, R423,
R424
RES., 10Ω, 1%, 1/10W, 0603 NIC, NRC06F10R0TRF
PANASONIC, ERJ3EKF10R0V
ROHM, MCR03EZPFX10R0
VISHAY, CRCW060310R0FKEA
YAGEO, RC0603FR-0710RL
18 1 R11 RES., 3.01k , 1%, 1/10W, 0603 VISHAY, CRCW06033K01FKEA
YAGEO, RC0603FR-073K01L
19 1 R17 RES., 30.1k , 1%, 1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF3012V
VISHAY, CRCW060330K1FKEA