MCP1661 datasheet(9/34 Pages) MICROCHIP

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DS20005315B-page 9

MCP1661

3.0

PIN DESCRIPTIONS

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

3.1

Feedback Voltage Pin (VFB)

The VFB pin is used to provide output voltage regulation

by using a resistor divider. The VFB voltage is 1.227V

typical.

3.2

Signal Ground Pin (SGND)

The signal ground pin is used as a return for the

integrated reference voltage and error amplifier. The

signal ground and power ground must be connected

externally in one point.

3.3

Switch Node Pin (SW)

Connect the inductor from the input voltage to the SW

pin. The SW pin carries inductor current, which can be

as high as 1.3A peak. The integrated N-Channel switch

drain is internally connected to the SW node.

3.4

Not Connected (NC)

This is an unconnected pin.

3.5

Power Supply Input Voltage Pin

(VIN)

Connect the input voltage source to VIN. The input

source must be decoupled from GND with a 4.7 µF

minimum capacitor.

3.6

Power Ground Pin (PGND)

The power ground pin is used as a return for the

high-current N-Channel switch. The signal ground and

power ground must be connected externally in one

point.

3.7

Enable Pin (EN)

The EN pin is a logic-level input used to enable or

disable device switching and lower quiescent current

while disabled. A logic high (>85% of VIN) will enable

the regulator output. A logic low (<7.5% of VIN) will

ensure that the regulator is disabled.

3.8

Exposed Thermal Pad (EP)

There is no internal electrical connection between the

Exposed Thermal Pad (EP) and the SGND and PGND

pins. They must be connected to the same potential on

the PCB.

3.9

Ground Pin (GND)

The ground or return pin is used for circuit ground

connection. The length of the trace from the input cap

return, the output cap return and the GND pin must be

as short as possible to minimize noise on the GND pin.

The 5-lead SOT-23 package uses a single ground pin.

TABLE 3-1:

PIN FUNCTION TABLE

MCP1661

SOT-23

MCP1661

2x3 TDFN

Symbol

Description

VFB

Feedback Voltage Pin

—2

SGND

Signal Ground Pin (TDFN only)

Switch Node, Boost Inductor Input Pin

—

4, 6

Not Connected

VIN

Input Voltage Pin

—7

PGND

Power Ground Pin (TDFN only)

Enable Control Input Pin

—

Exposed Thermal Pad (EP); must be connected to Ground.

(TDFN only)

—

GND

Ground Pin (SOT-23 only)

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