PM6686 datasheet(9/50 Pages) STMICROELECTRONICS

9 / 50 page

PM6686

Pin settings

Doc ID 15281 Rev 4

9/50

CP_FB

The CP_FB is used to monitor the optional external 14 V charge pump.

Connect a resistive voltage-divider from 14 V charge pump output to GND. If

CP_FB drops below the threshold voltage, the device performs a no audible

skip cycle. This charges the charge pump output (driven by LGATE1). Leave

CP_FB floating if the charge pump feedback is not needed.

GND

Signal ground reference for internal logic circuitry and LDO. It must be

connected to the signal ground plan of the power supply and to the exposed

pad. The signal ground plan and the power ground plan must be connected

together in one point near the PGND pin.

PGND

Power ground. This pin must be connected to the power ground plan of the

power supply.

LGATE2

Low-side gate driver output for the section 2.

BOOT2

Bootstrap capacitor connection for the switching section 2. It supplies the

high-side gate driver.

PHASE2

Switch node connection and return path for the high-side driver for the

section 2. It is also used as positive and negative current sense input.

HGATE2

High-side gate driver output for section 2.

EN2

Enable input for the switching section 2.

– If EN2 < 0.8 V the switching section OUT2 is turned off and all faults are

cleared.

– If EN2 > 2.4 V the switching section OUT2 is turned on.

If EN2 is connected to VREF2, the switching section OUT2 turns on after

the switching section OUT1 reaches regulation.

PG2

Power Good output signal for the section 2. This pin is an open drain output

and It is pulled down when the output of the switching section 2 is out of

+ 14% / - 10% of its nominal value.

SKIP

Pulse skipping mode control input.

– If the pin is connected to VCC the PWM mode is enabled.

– If the pin is connected to GND, the pulse skip mode is enabled.

– If the pin is connected to VREF2 (or floating) the pulse skip mode is

enabled but and the switching frequency is kept higher than 33 kHz (No-

audible pulse skip mode).

OUT2

Output voltage sense for the switching section 2.This pin must be directly

connected to the output voltage of the switching section. It provides also the

feedback for the switching section 2 when REFIN2 is tied to VREF3/VCC.

ILIM2

Positive current sense input for the switching section 2. It is possible to set a

threshold voltage that is compared with 1/10th of the GND-PHASE2 drop

during the off time.

REFIN2

Feedback input for the switching section 2:

– If this pin is connected to VCC, OUT2 operates at 3.3 V

– If this pin is connected to VREF3, OUT2 operates at 1.05 V

– If this pin is connected to an external reference from 0.7 V to 2.5 V, OUT2

works in tracking with this reference. Bypass REFIN2 to GND with a 100

nF capacitor.

Table 2.

Pin descriptions (continued)

N°

Function

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