LM2742MTC National Semiconductor, LM2742MTC Datasheet - Page 17

• Manufacturer Part Number: LM2742MTC
• Manufacturer: National Semiconductor

Specifications of LM2742MTC

• Lead Free Status / RoHS Status: Not Compliant

This circuit shows the LM2742 paired with a cost effective
solution to provide the 5V chip power supply, using no extra
components other than the LM78L05 regulator itself. The in-
put voltage comes from a 'brick' power supply which does not
In situations where low cost is very important, the LM2742 can
also be used as an asynchronous controller, as shown in the
above circuit. Although a a schottky diode in place of the bot-
tom FET will not be as efficient, it will cost much less than the
FET. The 5V at low current needed to run the LM2742 could
FIGURE 8. 12V Unregulated to 3.3V, 3A, 750kHz
FIGURE 9. 12V to 5V, 1.8A, 100kHz
17
regulate the 12V line tightly. Additional, inexpensive 10uF ce-
ramic capacitors (Cinx and Cox) help isolate devices with
sensitive databands, such as DSL and cable modems, from
switching noise and harmonics.
come from a zener diode or inexpensive regulator, such as
the one shown in Figure 8. Because the LM2742 senses cur-
rent in the low side MOSFET, the current limit feature will not
function in an asynchronous design. The ISEN pin should be
left open in this case.
20087509
20087508
www.national.com