LM25085MY/NOPB National Semiconductor, LM25085MY/NOPB Datasheet - Page 16

• Manufacturer Part Number: LM25085MY/NOPB
• Description: IC BUCK ADJ 8MSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Step-Down (Buck), Invertingr

Specifications of LM25085MY/NOPB

• Design Resources: LM(2)5085 Quick Start Calculator
• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 42 V
• Frequency - Switching: Up to 1MHz
• Voltage - Input: 4.5 ~ 42 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP Exposed Pad, 8-HMSOP, 8-eMSOP
• Power - Output: 250mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Other names: LM25085MY

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C
vides not only noise filtering and stability for the VCC regula-
tor, but also provides the surge current for the PFET gate
drive. The typical recommended value for C
good quality, low ESR, ceramic capacitor is recommended.
C
VCC pins. If the selected PFET has a Total Gate Charge
specification of 100 nC or larger, or if the circuit is required to
operate at input voltages below 7 volts, a larger capacitor may
be required. The maximum recommended value for C
1 µF.
IC Power Dissipation: The maximum power dissipated in the
LM25085 package is calculated using Equation 12 at the
VCC
VCC
: The capacitor at the VCC pin (from VIN to VCC) pro-
must be located as close as possible to the VIN and
VCC
is 0.47 µF. A
FIGURE 4. Example Circuit
VCC
is
16
maximum input voltage. The Total Gate Charge for the
Si7465 PFET is specified to be 40 nC (max) in its data sheet.
Therefore the total power dissipation within the LM25085 is
calculated to be:
Using an MSOP-8EP package with a θ
a temperature rise of 26°C from junction to ambient.
Final Design Example Circuit
The final circuit is shown in Figure 4, and its performance is
presented in Figure 5 through Figure 8.
P
DISS
= 42V x ((40 nC x 300 kHz) + 1.3 mA) = 559 mW
JA
of 46°C/W produces
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