MCP79401 datasheet(8/62 Pages) MICROCHIP

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MCP79400/MCP79401/MCP79402

DS20005009F-page 8

 2011-2016 Microchip Technology Inc.

3.0

PIN DESCRIPTIONS

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

TABLE 3-1:

PIN FUNCTION TABLE

3.1

Oscillator Input/Output (X1, X2)

These pins are used as the connections for an external

32.768 kHz quartz crystal and load capacitors. X1 is

the crystal oscillator input and X2 is the output. The

MCP7940X is designed to allow for the use of external

load capacitors in order to provide additional flexibility

when choosing external crystals. The MCP7940X is

optimized for crystals with a specified load capacitance

of 6-9 pF.

X1 also serves as the external clock input when the

MCP7940X is configured to use an external oscillator.

3.2

Backup Supply (VBAT)

This is the input for a backup supply to maintain the

RTCC and SRAM registers during the time when VCC

is unavailable.

If the battery backup feature is not being used, the

VBAT pin should be connected to VSS.

3.3

Serial Data (SDA)

This is a bidirectional pin used to transfer addresses

and data into and out of the device. It is an open-drain

terminal. Therefore, the SDA bus requires a pull-up

resistor to VCC (typically 10 kΩ for 100 kHz, 2 kΩ

 for

400 kHz). For normal data transfer, SDA is allowed to

change only during SCL low. Changes during SCL high

are reserved for indicating the Start and Stop

conditions.

3.4

Serial Clock (SCL)

This input is used to synchronize the data transfer to

and from the device.

3.5

Multifunction Pin (MFP)

This is an output pin used for the alarm and square

wave output functions. It can also serve as a general

purpose output pin by controlling the OUT bit in the

CONTROL register.

The MFP is an open-drain output and requires a pull-up

resistor to VCC (typically 10 kΩ). This pin may be left

floating if not used.

Name

8-pin

SOIC

8-pin

MSOP

8-pin

TSSOP

8-pin

TDFN

Function

1111

Quartz Crystal Input, External Oscillator Input

2222

Quartz Crystal Output

VBAT

3333

Battery Backup Supply Input

VSS

4444

Ground

SDA

5555

Bidirectional Serial Data (I2C)

SCL

6666

Serial Clock (I2C)

MFP

7777

Multifunction Pin

VCC

8888

Primary Power Supply

Note:

Exposed pad on TFDN can be connected to VSS or left floating.

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