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PM6681A

Dual synchronous step-down controller with adjustable LDO

STMicroelectronics 

Pin settings

PM6681A

Table 2. Pin functions (continued)

N°

Pin

Function

Enable input for the switching section 2.

– The section 2 is enabled applying a voltage greater than 2.4 V to this pin.

4

EN2

– The section 2 is disabled applying a voltage lower than 0.8 V.

When the section is disabled the high side gate driver goes low and Low

Side gate driver goes high. If both EN1 and EN2 pins are low and SHDN pin

is high the device enters in standby mode.

Shutdown control input.

– The device switch off if the SHDN voltage is lower than the device off

threshold (shutdown mode)

5

SHDN

– The device switch on if the SHDN voltage is greater than the device on

threshold.

The SHDN pin can be connected to the battery through a voltage divider to

program an undervoltage lockout. In shutdown mode, the gate drivers of the

two switching sections are in high impedance (high-Z).

Feedback input for the switching section 2 This pin is connected to a

6

FB2

resistive voltage-divider from OUT2 to PGND to adjust the output voltage

from 0.9 V to 3.3 V.

7

LDO

Adjustable internal regulator output. It can be set from 0.9 V to 3.3 V.

LDO pin can provide a 100 mA peak current.

8

OUT2

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

connected to the output voltage of the switching section.

9

BOOT2

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

high-side gate driver.

10

HGATE2

High-side gate driver output for section 2. This is the floating gate driver

output.

11

PHASE2

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

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

Positive current sense input for the switching section 2. This pin must be

12

CSENSE2

connected through a resistor to the drain of the synchronous rectifier

(RDS(on) sensing) to obtain a positive current limit threshold for the power

supply controller.

13

LGATE2 Low-side gate driver output for the section 2.

14

PGND

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

power supply.

15

LGATE1 Low-side gate driver output for the section 1.

Feedback input for the adjustable internal linear regulator. This pin is

16

LDO FB connected to a resistive voltage-divider from LDO to SGND to adjust the

output voltage from 0.9 V to 3.3 V.

Internal 5 V regulator bypass connection.

– If V5SW is connected to OUT5 (or to an external 5 V supply) and V5SW is

17

V5SW

greater than 4.9 V, the LDO5 regulator shuts down and the LDO5 pin is

directly connected to OUT5 through a 3 W (max) switch.

If V5SW is connected to GND, the LDO5 linear regulator is always on if the

device is not in shutdown mode.

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