MCP47DA1 datasheet(30/76 Pages) MICROCHIP

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MCP47DA1

DS25118D-page 30

 2012-2013 Microchip Technology Inc.

4.1

POR/BOR Operation

The Power-on Reset is the case where the device is

having power applied to it from VSS. The Brown-out

Reset occurs when a device had power applied to it,

and that power (voltage) drops below the specified

range.

The device’s RAM retention voltage (VRAM) is lower

than the POR/BOR voltage trip point (VPOR/VBOR).

This ensures that when the device Power-on Reset

occurs, the logic can retain the default values that are

loaded. The maximum VPOR/VBOR voltage is less than

1.8V. When VPOR/VBOR < VDD < 2.7V, the DACs’ elec-

trical performance may not meet the data sheet

specifications.

Table 4-2 shows the DAC’s level of functionality across

the entire VDD range, while Figure 4-2 illustrates the

Power-up and Brown-out functionality.

4.1.1

POWER-ON RESET

When the device powers up, the device VDD will cross

the VPOR/VBOR voltage. Once the VDD voltage crosses

the VPOR/VBOR voltage, the following happens:

• Volatile serial shift register/wiper register is loaded

with the default values (see Table 4-1)

• The device is capable of digital operation

TABLE 4-1:

DEFAULT POR WIPER

SETTING SELECTION

4.1.2

BROWN-OUT RESET

When the device powers down, the device VDD will

cross the VPOR/VBOR voltage (VBOR < 1.8V). Once the

VDD voltage decreases below the VPOR/VBOR voltage,

the following happens:

• Serial Interface is disabled

If the VDD voltage decreases below the VRAM voltage,

the following happens:

• Volatile Serial Shift Register (SSR) and wiper

As the voltage recovers above the VPOR/VBOR voltage,

see Section 4.1.1 “Power-on Reset”.

Serial commands not completed due to a brown-out

condition may cause the memory location to become

corrupted.

4.1.3

WIPER REGISTER (RAM)

The wiper register is 7-bit volatile memory that starts

functioning at the RAM retention voltage (VRAM). The

wiper register will be loaded with the default wiper

value when VDD rises above the VPOR/VBOR voltage.

4.1.4

DEVICE CURRENTS

The current of the device can be classified into two

modes of the device operation. These are:

• Serial Interface Inactive (Static Operation)

• Serial Interface Active

Static Operation occurs when a Stop condition is

received. Static Operation is exited when a Start

condition is received.

TABLE 4-2:

DEVICE FUNCTIONALITY AT EACH VDD REGION (Note 1)

Note:

At voltages below VDD(MIN), the electrical

performance of the I2C interface may not

meet the data sheet specifications

Default POR

Wiper Setting

Serial Shift

Wiper Register

Mid-scale

40h

20h

VDD Level

Serial

Interface

VOUT

DAC Register Setting

Comment

VDD < VTH

Ignored

Unknown

VTH < VDD < VBOR Ignored

Pulled Low

Unknown

VBOR  VDD < 1.8V Unknown

Operational with reduced

electrical specifications

DAC register loaded with

POR/BOR value

1.8V

 VDD < 2.7V Accepted Operational with reduced

electrical specifications

DAC register determines

serial Value

Electrical performance may

not meet the data sheet

specifications.

2.7V

 VDD  5.5V Accepted Operational

DAC register determines

serial value

Meets the data sheet

specifications

Note 1: For system voltages below the minimum operating voltage, it is recommended to use a voltage supervisor

to hold the system in Reset. This will ensure that MCP47X1 commands are not attempted out of the oper-

ating range of the device.

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