LM5166DRCT datasheet(15/53 Pages) TI1

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OUT

SW(PFM)

PK(PFM)

˜ ¨

VREF = 1.233V

ILIM

SLEEP

ACTIVE

SLEEP

ACTIVE

IOUT1

IOUT2

ACTIVE

10mV

VOUT

VIN

SLEEP ACTIVE

Inductor

Current

Voltage

(internal)

Voltage

LM5166

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SNVSA67A – DECEMBER 2016 – REVISED DECEMBER 2016

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Feature Description (continued)

7.3.2.1 PFM Mode Operation

In PFM mode, the LM5166 behaves as a hysteretic voltage regulator operating in boundary conduction mode.

The output voltage is regulated between upper and lower threshold levels according to the PFM feedback

comparator hysteresis of 10 mV. Figure 39 shows the relevant output voltage and inductor current waveforms.

The LM5166 provides the required switching pulses to recharge the output capacitor to the upper threshold,

followed by a sleep period where most of the internal circuits are disabled. The load current is supported by the

output capacitor during this time, and the LM5166 current consumption reduces to 9.7 µA. The sleep period

duration depends on load current and output capacitance.

Figure 39. PFM Mode Output Voltage and Inductor Current Waveforms

When operating in PFM mode at given input and output voltages, the chosen filter inductance dictates the PFM

pulse frequency as

(1)

where IPK(PFM) is one of the programmable levels for peak current limit. See Adjustable Current Limit for more

detail.

One of the supported ILIM settings enables a function that modulates the peak current threshold levels during

the first three switching cycles of each active period as illustrated in Figure 40. This function improves efficiency

under most application conditions at the expense of slightly degraded transient load response.

LM5166DRCT Datasheet(PDF) 15 Page - Texas Instruments

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