LM5088MH-1EVAL/NOPB National Semiconductor, LM5088MH-1EVAL/NOPB Datasheet - Page 2

• Manufacturer Part Number: LM5088MH-1EVAL/NOPB
• Description: LM5088MH-1 EVAL BOARD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM5088MH-1EVAL/NOPB

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Power - Output: -
• Voltage - Output: 5V
• Current - Output: 7A
• Voltage - Input: 5.5 ~ 55V
• Regulator Topology: Buck
• Frequency - Switching: 250kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM5088
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

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Powering and Loading
Considerations
Read this entire page prior to attempting to power the evalu-
ation board.
QUICK SETUP PROCEDURE
Step 1: Set the power supply current limit to 10A. Turn off the
power supply. Connect the power supply to the VIN terminals.
Step 2: Connect the load, with a 7A capability, to the VOUT
terminals.
Step 3: Slowly increase the load while monitoring the output,
VOUT should be in regulation with a nominal 5V output.
Step 4: Slowly sweep the input voltage from 5.5V to 55V,
VOUT should remain in regulation with a nominal 5V output.
POWERING UP
It is suggested that the load be kept low during the first power
up. Set the current limit of the source supply to provide about
1.5 times the anticipated wattage of the load. A quick effi-
ciency check is the best way to confirm that everything is
operating properly. If something is amiss one can be reason-
ably sure that it will affect the efficiency adversely. Few pa-
rameters can be correct in a switching power supply without
creating losses and potentially damaging heat.
OVER CURRENT PROTECTION
The LM5088-1 and LM5088-2 evaluation boards are both
configured with over-current protection schemes. The
LM5088-1 employs a cycle-by-cycle current limiting, while the
LM5088-2 is configured for a hiccup mode restart. Please re-
fer the LM5088 datasheet for more information on RES pin.
SYNCHRONIZATION
A Sync pin has been provided on the evaluation board. This
pin can be used to synchronize the LM5088 to an external
clock. Refer the LM5088 datasheet for complete information.
FIGURE 2. Typical Thermal Profile at 48VIN
2
Step 5: Temporarily short the EN pin to check the shutdown
function, Also, EN pin can be set between 0.4V and 1.2V, for
example, by shorting EN pin to ground with a diode, to check
the standby function.
Step 6: Increase the load beyond the rated current to check
the current limiting. The output current should limit at approx-
imately 10A. The LM5088-1 board will enter cycle-by-cycle
current limiting, while LM5088-2 is configured for a hiccup
mode restart. Cooling is critical in this step.
AIR FLOW
Prolonged operation with high input voltage (>36V) at full load
will cause the LM5088 and MOSFETs to overheat and could
potentially result in thermal shutdown. A fan with a minimum
of 100LFM should always be used to cool the LM5088 eval-
uation board.
ACTIVE LOADS
When using electronic load, it is strongly recommended to
power up the evaluation board at light load and then slowly
increase the load. This is necessary as most of the electronic
loads do not draw any current till the output reaches an inter-
nally set point; this can result in soft-start function to not work
as desired and can trip the current sense comparator. Elec-
tronic loads, in general, are best suited for monitoring steady
state waveforms. If it is desired to power up the evaluation
board at maximum load, resistor banks can be used. This will
ensure a soft-start and evaluation board will perform as de-
sired. Ensure that there is sufficient cooling for both the
resistor banks and the LM5088 evaluation board, while run-
ning at full load.
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