MCP1256 datasheet(11/24 Pages) MICROCHIP

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DS21989A-page 11

MCP1256/7/8/9

3.0

PIN DESCRIPTION

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

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Status Indication (PGOOD, LBO)

3.1.1

POWER-GOOD OUTPUT PIN

(PGOOD)

MCP1256/8: PGOOD is high impedance when the out-

put voltage is in regulation. A logic low is asserted

when the output falls 7% (typical) below the nominal

value. The PGOOD output remains low until VOUT is

within 3% (typical) of its nominal value. On start-up, this

pin indicates when the output voltage reaches its final

value. PGOOD is high impedance when SHDN is low

or when BYPASS is low (MCP1258).

3.1.2

LOW-BATTERY OUTPUT PIN (LBO)

MCP1257/9: LBO is high impedance when the input

voltage is above the low-battery threshold voltage. A

logic low is asserted when the input falls below the low-

battery threshold voltage. The LBO output remains low

until VIN is above the low-battery threshold voltage plus

the low-battery hysteresis voltage. LBO is high

impedance when SHDN is low or when BYPASS is low

(MCP1259).

3.2

Mode Selection (SLEEP, BYPASS)

3.2.1

ACTIVE LOW SLEEP MODE

(SLEEP)

MCP1256/7: A logic low signal applied to this pin

places the device into a SLEEP mode of operation. In

this mode, the device maintains regulation. SLEEP

mode performs pulse skip operation reducing the

current draw of the device at the expense of increased

output voltage ripple.

3.2.2

ACTIVE LOW BYPASS MODE

(BYPASS)

MCP1258/9: A logic low signal applied to this pin

places the device into a BYPASS mode of operation. In

this mode, the input supply voltage is connected

directly to the output.

3.3

Flying Capacitor Negative (C2-)

A 1 μF ceramic flying capacitor is recommended.

3.4

Flying Capacitor Positive (C1+)

A 1 μF ceramic flying capacitor is recommended.

3.5

Regulated Output Voltage (VOUT)

Regulated 3.3V output. Bypass to GND with a

minimum of 2.2 μF.

3.6

Flying Capacitor Positive (C2+)

A 1 μF ceramic flying capacitor is recommended.

3.7

Power Supply Input Voltage (VIN)

A supply voltage of 1.8V to 3.6V is recommended.

Bypass to GND with a minimum of 1 μF.

3.8

Flying Capacitor Negative (C1-)

A 1 μF ceramic flying capacitor is recommended.

3.9

0V Reference (GND)

Connect to negative terminal of and input supply.

3.10

Device Shut Down (SHDN)

A logic low signal applied to this pin disables the

device. A logic high signal applied to this pin allows

normal operation.

Pin No.

Symbol

Function

DFN

MSOP

PGOOD

Power-Good Indication Open-Drain Output Pin: MCP1256 and MCP1258

LBO

Low-Battery Indication Open-Drain Output Pin: MCP1257 and MCP1259

SLEEP

Active Low SLEEP Mode Input Pin: MCP1256 and MCP1257

BYPASS

Active Low BYPASS Mode Input Pin: MCP1258 and MCP1259

C2-

Flying Capacitor Negative Pin

C1+

Flying Capacitor Positive Pin

VOUT

Regulated 3.3V Output Voltage

C2+

Flying Capacitor Positive Pin

VIN

Power Supply Input Voltage

C1-

Flying Capacitor Negative Pin

GND

0V Reference

SHDN

Active Low SHUTDOWN Mode Input Pin

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