7447786004 datasheet(13/34 Pages) MICROCHIP

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DS22285A-page 13

MCP16321/2

3.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 3-1.

3.1

Switch Pin (SW)

The drain of the low-side N-Channel switch is

connected internally to the source of the high-side

N-Channel switch, and externally to the SW node,

consisting of the inductor and bootstrap capacitor. The

SW node can rise very fast as a result of the internal

high-side switch turning on. It should be connected

directly to the 4.7 µH inductor with a wide, short trace.

3.2

Power Supply Input Voltage Pin

(VIN)

Connect the input voltage source to VIN. The input

source should be decoupled to GND using 2 x 10 µF

capacitors. The amount of the capacitance depends on

the impedance of the source and output current. The

input capacitors provide AC current for the high-side

power switch and a stable voltage source for the

internal device power. This capacitor should be

connected as close as possible to the VIN and GND

pins.

3.3

Signal Ground Pin (SGND)

This ground is used for the majority of the device,

including the analog reference, control loop, and other

circuits.

3.4

Feedback Voltage Pin (VFB)

The VFB input pin is used to provide output voltage

regulation by either using a resistor divider or VOUT

directly. For the adjustable version, the VFB will be 0.9V

typical with the output voltage in regulation. For the

fixed version, the VFB will be equal to the

corresponding VOUT value.

3.5

Power Good Pin (PG)

PG is an open drain, active low output. The regulator

output voltage is monitored and the PG line will remain

low until the output voltage reaches the VOUT-UV

threshold. Once the internal comparator detects that

the output voltage is above the VOUT-UV threshold, an

internal delay timer is activated. After a 10 ms delay,

the PG open drain output pin can be pulled high,

indicating that the output voltage is in regulation. The

maximum voltage applied to the PG output pin should

not exceed 6V.

TABLE 3-1:

PIN FUNCTION TABLE

MCP16321/2

3x3 QFN

Symbol

Description

Output switch node, connects to the inductor and the bootstrap capacitor

2VIN

Input supply voltage pin for power and internal biasing

3VIN

Input supply voltage pin for power and internal biasing

SGND

Primary signal ground

5VFB

Output voltage feedback pin. Connect VFB to VOUT for fixed version and output

resistor divider for adjustable version.

No Connection

Power Good open-drain output, pulled up to a maximum of 6V

Enable input pin. Logic high enables the operation. Internally pulled up, pull EN pin

low to disable regulator’s output. Maximum voltage on EN input is 6V.

BOOST

Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor

is connected between the BOOST and SW pins.

VIN

Input supply voltage pin for power and internal biasing

Output switch node, connects to the inductor and the bootstrap capacitor

PGND

GND supply for the internal low-side NMOS/integrated diode

PGND

GND supply for the internal low-side NMOS/integrated diode

Output switch node, connects to the inductor and the bootstrap capacitor

Exposed Thermal Pad (EP); must be connected to GND

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