l6920 STMicroelectronics, l6920 Datasheet - Page 6

• Manufacturer Part Number: l6920
• Description: 1v High Efficiency Syncronous Step Up Converter
• Manufacturer: STMicroelectronics

L6920
Figure 7. PFM mode Condition: V
Trace1: Vout (50mV~/div) Trace 4: IL (100mA/div)
Time div.: 5µs/div
Figure 8. Heavier load - Train pulses overlapping.
Trace1: V
Time div.: 10 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:
Where η is the efficiency and I
Of course, if Iload is greater than Iload_lim the regulation is lost (figure 11).
6/13
out
(100mV~/div) Trace 4: I
I
load_lim
lim
=1A.
out
=
L
= 5V; V
(200mA/div)
---------- -
V
V
out
in
in
⋅
⎛
⎝
=1.5V.
I
lim
–
T
off min
Figure 9. Heavy load - Inductor current ripples
below I
(200mA/div) Time div.: 20 µs/div
Figure 10. Heavy load and High ESR. Regulation
falls in continuous mode of operation. Trace1:
V
div.: 5 µs/div
out
⋅
V
------------------------- -
(100mV~/div) Trace 4: I
out
2 L
lim
⋅
–
Trace1: V
V
in
⎞ η
⎠
⋅
eq. (1)
out
(100mV~/div) Trace 4: I
L
(200mA/div). Time
L