MCP47CMB02 datasheet(63/124 Pages) MICROCHIP

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DS20006089B-page 63

MCP47CXBXX

Table 5-2 shows the gain bit operation.

The volatile G bit value can be modified by:

• POR Event

• BOR Event

•I2C Write Commands

•I2C General Call Reset Command

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 provided in

Equation 5-2. Examples of Volatile DAC register values

and the corresponding theoretical VOUT voltage for the

MCP47CXBXX devices are shown in Table 5-6.

EQUATION 5-2:

CALCULATING OUTPUT

VOLTAGE (VOUT)

When Gain = 2 (VRL = VREF), if VREF > VDD/2, the VOUT

voltage is limited to VDD. So if VREF = VDD, the VOUT

voltage does not change for Volatile DAC register

values mid-scale and greater, since the output amplifier

is at full-scale output.

The following events update the DAC register value,

and therefore, the analog Voltage Output (VOUT):

• Power-on Reset

• Brown-out Reset

•I2C write command (to Volatile registers) on the

rising edge of the last write command bit

•I2C General Call Reset command; the output is

updated with default POR data or MTP values

•I2C general call wake-up command; the output is

updated with default POR data or MTP values

Next, the VOUT voltage starts driving to the new value

after the event has occurred.

5.3.3

STEP VOLTAGE (VS)

The step voltage depends 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 cal-

culated by using Equation 5-3 (the DAC register value

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

Table 5-3 for several VREF voltages.

EQUATION 5-3:

VS CALCULATION

TABLE 5-3:

THEORETICAL STEP VOLTAGE (VS)(1)

TABLE 5-2:

OUTPUT DRIVER GAIN

Gain Bit

Gain

Comment

Limits VREF pin voltages

relative to device VDD voltage.

Where:

# Resistors in R-Ladder = 4096 (MCP47CXB2X)

1024 (MCP47CXB1X)

256 (MCP47CXB0X)

VOUT

VRL DAC Register Value



# Resistor in Resistor Ladder

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



Where:

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

1024 (10-bit)

256 (8-bit)

VRL

# Resistor in Resistor Ladder

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



Step

Voltage

VREF

5.02.7

1.81.5

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

19.5mV

10.5mV

7.03 mV

5.86mV

3.91 mV

8-bit

Note 1:

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

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