A6986F datasheet(26/72 Pages) STMICROELECTRONICS

26 / 72 page

Functional description

A6986F

26/72

DocID027739 Rev 1

The ISKIP programmability helps to optimize the performance in terms of the output voltage

ripple or efficiency at the light-load, that are parameters which disagree each other by

definition.

A lower skip current level minimizes the voltage ripple but increases the switching activity

(time between bursts gets closer) since less energy per burst is transfered to the output

voltage at the given load. On the other side, a higher skip level reduces the switching activity

and improves the efficiency at the light-load but worsen the voltage ripple.

No difference in terms of the voltage ripple and conversion efficiency for the medium and

high load current level, that is when the device operates in the discontinuous or continuous

mode (DCM vs. CCM).

Figure 14 and Figure 15 report the efficiency measurements to highlight the ISKIPH and

ISKIPL efficiency gap at the light-load also in comparison with the LNM operation (also

called NOSKIP). The same efficiency at the medium / high load is confirmed at different

ISKIP levels.

Figure 14. Light-load efficiency comparison at different ISKIP - linear scale

Figure 15. Light-load efficiency comparison at different ISKIP - log scale

Table 11. ISKIP programmable current threshold

SYNCH / ISKIP (pin 4)

ISKIP current threshold

LOW

ISKIPH = 0.4 A typical

HIGH

ISKIPL = 0.2 A typical

0.2

0.4

0.6

0.8

1.2

1.4

1.6

A6986F VIN=13.5 VOUT=5V VBIAS ISKIPL

A6986F VIN=13.5 VOUT=5V NOVBIAS ISKIPL

A6986F VIN=13.5 VOUT=5V NOVBIAS ISKIPH

A6986F VIN=13.5 VOUT=5V VBIAS ISKIPH

A6986F VIN=13.5 VOUT=5V NOVBIAS NOSKIP

A6986F VIN=13.5 VOUT=5V VBIAS NOSKIP

LNM

LCM ISKIPH =200mA

LCM ISKIPH =400mA

0.001

0.01

0.1

A6986F VIN=13.5 VOUT=5V VBIAS ISKIPL

A6986F VIN=13.5 VOUT=5V NOVBIAS ISKIPL

A6986F VIN=13.5 VOUT=5V NOVBIAS ISKIPH

A6986F VIN=13.5 VOUT=5V VBIAS ISKIPH

A6986F VIN=13.5 VOUT=5V NOVBIAS NOSKIP

A6986F VIN=13.5 VOUT=5V VBIAS NOSKIP

LNM

LCM IKIPH =200mA

LCM IKIPH =400mA

A6986F датащи(PDF) 26 Page - STMicroelectronics

A6986F датащи(HTML) 26 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72

датащи скачать

ссылки URL