T1
CS
V
IN
36 - 78V
V
OUT
3.3V
SYNC I/O
LM5026
UVLO
PGND AGND
COMP
OUT_A
OUT_B
V
CC
SS
RT
SYNC
REF
TIME
RES
CS
V
IN
DCL
ERROR
AMP and
ISOLATION
Powering and Loading Considerations
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Figure 1. Schematic
3
Powering and Loading Considerations
When applying power to the LM5026 evaluation board certain precautions need to be followed. A mis-
connection can damage the assembly.
4
Proper Connections
When operated at low input voltages the evaluation board can draw up to 3.5A of current at full load. The
maximum rated output current is 30A. Be sure to choose the correct connector and wire size when
attaching the source supply and the load. Monitor the current into and out of the evaluation board. Monitor
the voltage directly at the output terminals of the evaluation board. The voltage drop across the load
connecting wires will give inaccurate measurements, this is especially true for accurate efficiency
measurements.
5
Source Power
The evaluation board can be viewed as a constant power load. At low input line voltage (36V) the input
current can reach 3.5A, while at high input line voltage (78V) the input current will be approximately 1.5A.
Therefore to fully test the LM5026 evaluation board a DC power supply capable of at least 80V and 4A is
required. The power supply must have adjustments for both voltage and current.
The power supply and cabling must present a low impedance to the evaluation board. Insufficient cabling
or a high impedance power supply will droop during power supply application with the evaluation board
inrush current. If large enough, this droop will cause a chattering condition upon power up. This chattering
condition is an interaction with the evaluation board undervoltage lockout, the cabling impedance and the
inrush current.
2
AN-1387 LM5026 Evaluation Board
SNVA117A – September 2005 – Revised May 2013
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