MCP4725 datasheet(20/50 Pages) MICROCHIP

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MCP4725

DS22039D-page 20

5.4.2

VDD RAMP RATE AND EEPROM

The MCP4725 uploads the EEPROM data to the DAC

VDD ramp rate is too slow ( <1 V/ms), the device may

not be able to load the EEPROM data to the DAC

ing to the current EEPROM data may not available to

the output pin. It is highly recommended to send a Gen-

eral Call Reset Command (see Section 7.3.1 “Gen-

eral call reset”) after power-up. This command will

reset the device at a stable VDD and make the DAC out-

put available immediately using the EEPROM data.

5.5

Normal and Power-Down Modes

The device has two modes of operation: Normal mode

and power-down mode. The mode is selected by

programming the power-down bits (PD1 and PD0) in

the Configuration register. The user can also program

the two power-down bits in non-volatile EEPROM

memory.

When the normal mode is selected, the device

operates a normal digital-to-analog conversion. If the

power-down mode is selected, the device enters a

power saving condition by shutting down most of the

internal circuits. During the power-down mode, all

internal circuits except the I2C interface are disabled

and there is no data conversion event, and no VOUT is

available. The device also switches the output stage

from the output of the amplifier to a known resistive

load. The value of the resistive load is determined by

the state of the power-down bits (PD1 and PD0).

Table 5-2 shows the outcome of the power-down bit

and the resistive load.

During the power-down mode, the device draws about

60 nA (typical). Although most of internal circuits are

shutdown, the serial interface remains active in order

to receive the I2C command.

The device exits the power-down mode immediately

when (a) it receives a new write command for normal

mode or (b) it receives an I2C General Call Wake-Up

Command.

When the DAC operation mode is changed from

power-down to normal mode, the output settling time

takes less than 10 µs, but greater than the standard

Active mode settling time (6 µs, typical).

TABLE 5-2:

POWER-DOWN BITS

FIGURE 5-1:

Output Stage for Power-

Down Mode.

PD1

PD0

Function

Normal Mode

1kΩ resistor to ground (1)

100 kΩ resistor to ground (1)

500 kΩ resistor to ground (1)

Note 1: In the power-down mode: VOUT is off and

most of internal circuits are disabled.

1kΩ

100 kΩ 500 kΩ

Power-Down

Control Circuit

Resistive

Load

VOUT

Amp

Resistive String DAC

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