LM2704

SNVS175D – FEBRUARY 2002 – REVISED MAY 2013

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OPERATION

Figure 2. LM2704 Block Diagram

2) Inductor Current, 500mA/div, DC

T = 10µs/div

Figure 3. Typical Switching Waveform

The LM2704 features a constant off-time control scheme. Operation can be best understood by referring to

Figure 2 and Figure 3. Transistors Q1 and Q2 and resistors R3 and R4 of Figure 2 form a bandgap reference

used to control the output voltage. When the voltage at the FB pin is less than 1.237V, the Enable Comp in

Figure 2 enables the device and the NMOS switch is turned on pulling the SW pin to ground. When the NMOS

switch is on, current begins to flow through inductor L while the load current is supplied by the output capacitor

8

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