PM6686 datasheet(27/50 Pages) STMICROELECTRONICS

27 / 50 page

PM6686

Device description

Doc ID 15281 Rev 4

27/50

The COT architecture uses a minimum off-time (TOFFMIN) to allow inductor valley current

sense on the synchronous switch and to allow the charge of the bootstrap capacitor. A

minimum on-time is also introduced to assure the start-up sequence.

An adaptive anti-cross conduction algorithm avoids current paths between VIN and GND

during switching transition.

The PM6686 has three different operation modes selectable with SKIP pin: forced PWM

(PWM), pulse SKIP (SKIP) and non audible pulse SKIP (NA SKIP). The following

paragraphs explain in details the different features of these operation modes.

Figure 46.

Constant on time block diagram

Table 9.

Operative mode configurations

Control pin

connected to

Operation mode

SKIP

VCC

PWM

GND

SKIP

VREF2 or floating

NA SKIP

BOOT

SET

CLR

LS Driver

HGAT E

PH ASE

LGATE

PGND

Level

Shifter

HS Driver

SET

CLR

Z.C.

Comparator

Toff min

Ton

generator

PWM

Comparator

OU T

Voltage

Reference

ILIM

VIN

PVCC

PHASE

1/10

0,8V

0,5V

0,25V

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