L6920 查看數據表（PDF） - STMicroelectronics

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L6920

1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER

STMicroelectronics 

L6920

Figure 7. PFM mode Condition: Vout = 5V; Vin =1.5V.

Trace1: Vout (50mV~/div) Trace 4: IL (100mA/div)

Time div.: 5µs/div

Figure 9. Heavy load - Inductor current ripples

below Ilim Trace1: Vout (100mV~/div) Trace 4: IL

(200mA/div) Time div.: 20 µs/div

Figure 8. Heavier load - Train pulses overlapping.

Trace1: Vout (100mV~/div) Trace 4: IL (200mA/div)

Time div.: 10 µs/div

Figure 10. Heavy load and High ESR. Regulation

falls in continuous mode of operation. Trace1:

Vout (100mV~/div) Trace 4: IL (200mA/div). Time

div.: 5 µs/div

When Iload is heavier, the pulse trains are overlapped. Figures 7 - 8 show some possible behaviors.

Considering that current in the inductor is limited to 1A, the maximum load current is defined by the following

relationship:

Il o a d _lim

=

--V----i--n---

Vout

⋅

⎛

⎝

Il

i

m

–To

ff

min

⋅

-V----o---u2---t--⋅-–--L--V----i--n-⎠⎞

⋅η

eq. (1)

Where η is the efficiency and Ilim =1A.

Of course, if Iload is greater than Iload_lim the regulation is lost (figure 11).

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