MCP47FVB01 datasheet(45/92 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005429B-page 45

MCP48FEBXX

5.3.2

OUTPUT VOLTAGE

The volatile DAC Register values, along with the

device’s configuration bits, control the analog VOUT

voltage. The volatile DAC Register’s value is unsigned

binary. The formula for the output voltage is given in

Equation 5-2. Table 5-3 shows examples of volatile

DAC register values and the corresponding theoretical

VOUT voltage for the MCP48FEBXX devices.

EQUATION 5-2:

CALCULATING OUTPUT

VOLTAGE (VOUT)

The following events update the DAC register value

and therefore the analog voltage output (VOUT):

• Power-on Reset

• Brown-out Reset

• Write command

The VOUT voltage will start driving to the new value

after the event has occurred.

5.3.3

STEP VOLTAGE (VS)

The Step Voltage is dependent on the device resolution

and the calculated output voltage range. One LSb is

defined as the ideal voltage difference between two

successive codes. The step voltage can easily be

calculated by using Equation 5-3 (DAC Register Value

is equal to 1). Theoretical step voltages are shown in

Table 5-2 for several VREF voltages.

EQUATION 5-3:

VS CALCULATION

TABLE 5-2:

THEORETICAL STEP

VOLTAGE (VS)

(1)

Note:

When Gain = 2 (VRL = VREF) and

if VREF > VDD / 2, the VOUT voltage will be

limited to VDD. So if VREF = VDD, then the

VOUT voltage will not change for volatile

DAC Register values mid-scale and greater,

since the op amp is at full-scale output.

Where:

# Resistors in R-Ladder = 4096 (MCP48FEB2X)

1024 (MCP48FEB1X)

256 (MCP48FEB0X)

OUT

DAC Register Value



# Resistor in Resistor Ladder

----------------------------------------------------------------------Gain



VREF

5.0

2.7

1.8

1.5

1.0

1.22 mV 659 uV

439 uV

366 uV

244 uV 12-bit

4.88 mV 2.64 mV 1.76 mV 1.46 mV 977 uV 10-bit

19.5 mV 10.5 mV 7.03 mV 5.86 mV 3.91 mV 8-bit

Note 1:

When Gain = 1x, VFS = VRL, and VZS = 0V.

Where:

# Resistors in R-Ladder = 4096 (12-bit)

1024 (10-bit)

256 (8-bit)

# Resistor in Resistor Ladder

----------------------------------------------------------------------Gain



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