MCP1643 datasheet(8/28 Pages) MICROCHIP

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MCP1643

DS20005208B-page 8

 2013-2023 Microchip Technology Inc. and its subsidiaries

3.0

PIN DESCRIPTIONS

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

3.1

Enable Pin (EN)

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

disable device switching. Device has low quiescent

current while disabled. A logic high (>75% of VIN) will

enable the regulator output. A logic low (<20% of VIN)

will ensure that the regulator is disabled.

3.2

Feedback Voltage Pin (VFB)

The VFB pin is used to regulate the voltage across the

RSET sense resistor to 120 mV, to keep the output LED

current in regulation.

3.3

Unconnected Pin (NC)

This pin is unconnected.

3.4

Output Voltage Power Pin (VOUT)

High current flows through the integrated P-Channel

and out of this pin to the output capacitor, LED load and

RSET sense resistor. The output voltage must be fil-

tered using a 4.7 µF to 20 µF X7R or X5R ceramic

capacitor. The value of the output capacitor depends

on the load current.

3.5

Switch Node Pin (SW)

Connect the inductor from the input voltage to the SW

pin. The SW pin carries inductor current and can be as

high as 1.6 A typical peak value. The integrated

N-Channel switch drain and integrated P-Channel

switch source are internally connected at the SW node.

3.6

Power Ground (PGND) and Signal

Ground Pins (SGND)

The power ground pin is used as a return for the high-

current N-Channel switch.

The signal ground pin is used as a return for the

integrated VFB and error amplifier.

The length of the trace from input cap return, output

cap return and PGND and SGND should be made as

short as possible to minimize noise on the ground pins.

The SGND and PGND pins are connected externally.

3.7

Power Supply Input Voltage Pin

(VIN)

Connect the input voltage source to VIN. The input

source should be decoupled to GND with a 4.7 µF

minimum capacitor.

3.8

Exposed Thermal Pad (EP)

There is no internal electrical connection between the

Exposed Thermal Pad (EP) and the PGND and SGND

pins. They must be connected to the same potential on

the Printed Circuit Board (PCB).

TABLE 3-1:

PIN FUNCTION TABLE

MCP1643

2x3 mm DFN

MCP1643

MSOP

Symbol

Description

Enable pin. The logic high enables the operation. Do not allow this pin to

float.

VFB

Reference Voltage pin. Connect to the VFB pin, the RSET (LED current set

resistor), and the cathode of the LED load.

Unconnected pin.

VOUT

Boost Converter Output pin. Connect to this pin the anode of the LED load.

An output filter capacitor is required.

Boost and Rectifier Switch Input pin. Connect the boost inductor between

SW and VIN.

PGND

Power Ground Reference pin.

SGND

Signal Ground Reference pin.

VIN

Input Supply Voltage pin. A local bypass capacitor is required.

—

Exposed Thermal Pad; must be connected to PGND and SGND.

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