LM25007EVAL National Semiconductor, LM25007EVAL Datasheet - Page 3

• Manufacturer Part Number: LM25007EVAL
• Description: BOARD EVALUATION LM25007
• Manufacturer: National Semiconductor

Specifications of LM25007EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 5V
• Current - Output: 450mA
• Voltage - Input: 9 ~ 42V
• Regulator Topology: Buck
• Frequency - Switching: 306kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM25007
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

Output Ripple Control
B) Intermediate Ripple Level Configuration: This configu-
ration generates more ripple at V
R4 is chosen to generate ≥25 mV at V
minimum ripple current in this circuit is 75 mAp-p at minimum
V
ation of the feedback resistors. C6’s minimum value is cal-
culated from:
where t
and R2//R3 is the equivalent parallel value of the feedback
resistors. For this evaluation board t
1800 ns, and R2//R3 = 1.5 kΩ, and C6 calculates to a
minimum of 1200 pF. The resulting ripple at V
IN
. C6 couples that ripple to the FB pin without the attenu-
ON(max)
is the maximum on-time (at minimum V
FIGURE 3. Intermediate Ripple Level Configuration Using C6 and R4
OUT1
ON(max)
OUT1
than the above con-
(Continued)
FIGURE 4. Minimum Cost Configuration
, knowing that the
is approximately
OUT1
ranges
IN
),
3
figuration, but uses one less capacitor. If some ripple can be
tolerated in the application, this configuration is slightly more
economical, and simpler. R4 and C6 are used instead of R6,
C7, and C8, as shown in Figure 3.
from )25 mVp-p to 50 mVp-p over the input voltage range
with the circuit in continuous conduction mode. The ripple
amplitude is higher if the load current is low enough to force
the circuit into discontinuous conduction mode.
C) Minimum Cost Configuration: This configuration is the
same as option B above, but without C6. Since 25 mVp-p are
required at the FB pin, R4 is chosen to generate 50 mvp-p at
V
is 75 mAp-p at minimum V
is used for R4. The resulting ripple at V
)50 mVp-p to )100 mVp-p over the input voltage range. If
the application can accept this ripple level, this is the most
economical solution. The circuit is shown in Figure 4.
OUT1
, knowing that the minimum ripple current in this circuit
20185007
20185009
IN
. To allow for tolerances, 0.68Ω
OUT1
ranges from
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