4
Rev. 0
Figure 4. Demo Setup with PC
USB to I
2
C/PMBus
DONGLE DC1613A
LTC7050 DEMO BOARD
DC2881A-A
USB CABLE
V
IN
12-PIN (J14)
CONNECTOR
DC2881A-A F04
LOAD1
V
OUT1
LOAD2
V
OUT2
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 V
OUT
, 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 V
IN
is present.
Efficiency measurement
Headers JP12 – JP16 are kelvin connected close to the
power stage for ideal efficiency measurement. For total
V
OUT1/2
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
V
IN
•I
IN
+
(V
DRV
•I
DRV
)
Optionally, FILTERED SW1 (JP12) can be used as the V
OUT
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 I
REF
voltage.
