lm25117psqx National Semiconductor Corporation, lm25117psqx Datasheet - Page 29

• Manufacturer Part Number: lm25117psqx
• Description: Wide Input Range Synchronous Buck Controller With Analog Current Monitor
• Manufacturer: National Semiconductor Corporation

The LM25117 also can be configured as a constant voltage
and constant current regulator, known as CV+CC regulator.
In this configuration, there is much less variation in the current
limiting as compared to peak cycle-by-cycle current limiting of
the inductor current. The LMV431 and the PNP transistor cre-
ate a voltage-to-current amplifier in the current loop. This
amplifier circuitry does not affect the normal operation when
FIGURE 21. Constant Voltage Regulator with Accurate Current Limit
FIGURE 22. Current Limit Comparison
29
the output current is less than the current limit set-point. When
the output current is greater than the set-point, the PNP tran-
sistor sources a current into C
slope of emulated inductor current ramp until the output cur-
rent is less than or equal to the current limit set-point. See
Figure 21
and
301550145
Figure
22.
RAMP
and increases the positive
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