LM5033SD-EVAL National Semiconductor, LM5033SD-EVAL Datasheet - Page 2

• Manufacturer Part Number: LM5033SD-EVAL
• Description: BOARD EVALUATION LM5033SD
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM5033SD-EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 9V
• Current - Output: 20A
• Voltage - Input: 40 ~ 60V
• Regulator Topology: Buck
• Frequency - Switching: 315kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM5033
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -
• Lead Free Status / Rohs Status: Not Compliant

www.national.com
Theory of Operation
Board Layout and Probing
The pictorial in Figure 1 and Figure 2 shows the placement
of the significant components which may be probed in evalu-
ating the circuit’s operation. The following should be kept in
mind when the board is powered:
1. The board has two circuit grounds - one associated with
2. The main current carrying components (L1, T1, T2, Q1,
3. Use care when probing the primary side at maximum
4. At maximum load current (20A), the wire size and length
5. The input wires will carry an average of 4A at maximum
Board Connections/Start-Up
When operating at load currents in excess of 5A forced air
flow across the board IS NECESSARY. The input connec-
tions are made to terminals J3 (+) and J1 (-). The source
must be capable of supplying the input current shown in
Figure 5. Upon turn-on the input current increases linearly,
without overshoot, due to the LM5033’s softstart function .
The load is connected to terminals J8 (+) and J4 (-). A
minimum of 14 gauge wire should be used for the 20A load
current.
the input power, and one associated with the output
power. The grounds are DC isolated.
Q2, L2, Q3 and Q4) will be hot to the touch at maximum
load current. USE CAUTION. When operating at load
currents in excess of 5A the use of a fan to provide
forced air flow IS NECESSARY.
input voltage. 60 volts is enough to produce shocks and
sparks
used to connect the load becomes important. Ensure
there is not a significant voltage drop in the wires. A
minimum of 14 gauge wire is recommended.
load current. Ensure these wires are adequately sized.
(Continued)
FIGURE 2. Evaluation Board - Bottom Side
2
Before start-up a voltmeter should be connected to the input
terminals, and one to the output terminals. The input current
should be monitored with an ammeter or a current probe. It
is recommended that the input voltage be increased gradu-
ally until the under-voltage lockout threshold (UVLO, )37V)
is reached, at which time the output becomes active. At this
point the three meters should be checked immediately to
ensure they indicate nominal values.
Performance
Once the circuit is powered up and operating normally, the
output voltage follows the input voltage as shown in Figure 6.
The load regulation is )
impedance of )30 mΩ. The power conversion efficiency,
which exceeds 95%, is shown in Figure 7.
Waveforms
Figure 4 shows some of the significant waveforms for vari-
ous input/output combinations. REMEMBER there are two
circuit grounds, and scope probe grounds must be con-
nected appropriately. When viewing the signal at the CS pin
the scope probe and its ground lead must be directly across
C13.
Primary Side Operation
With V
LM5033 alternating outputs drive the LM5100 Gate Driver.
The LM5100’s LO output drives Q2’s gate with a 0V to 10V
signal, and the HO output drives Q1’s gate with a voltage
which switches between ground and 9V above V
Q1 is on current flows from L1 and out of C1/C2 through Q1,
T1’s primary, T2, and into C3/C4. When Q2 is on current
IN
within the normal operating range (40V to 60V) the
±
350 mV (
±
4%), due to an output
20107702
IN
. When