MCP48FVB21 datasheet(45/84 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005466A-page 45

MCP48FVBXX

5.5

Latch Pin (LAT)

The Latch pin controls when the volatile DAC Register

value is transferred to the DAC wiper. This is useful for

applications that need to synchronize the wiper(s)

updates to an external event, such as zero crossing or

updates to the other wipers on the device. The LAT pin

is asynchronous to the serial interface operation.

When the LAT pin is high, transfers from the volatile DAC

When the LAT pin is low, the volatile DAC register value

is transferred to the DAC wiper.

Figure 5-8 shows the interaction of the LAT pin and the

loading of the DAC wiper x (from the volatile DAC

LAT pin is held low, the corresponding DAC wiper is

updated as soon as the volatile DAC Register value is

updated.

FIGURE 5-8:

LAT and DAC Interaction.

The LAT pin allows the DAC wiper to be updated to an

external event as well as have multiple DAC

channels/devices update at a common event.

Since the DAC wiper x is updated from the Volatile

DAC Register x, all DACs that are associated with a

given LAT pin can be updated synchronously.

If the application does not require synchronization, then

this signal should be tied low.

Figure 5-9 shows two cases of using the LAT pin to

control when the wiper register is updated relative to

the value of a sine wave signal.

FIGURE 5-9:

Example Use of LAT Pin Operation.

Note:

This allows both the volatile DAC0 and

DAC1 registers to be updated while the

LAT pin is high, and to have outputs

synchronously updated as the LAT pin is

driven low.

Write Command

Vol. DAC Register x

DAC wiper x

16 Clocks

LAT

SYNC

Transfer

Serial Shift Reg

Data

(internal signal)

LAT

SYNC

Transfer

Data

Comment

No Transfer

Vol. DAC Register x

 DAC wiper x

No Transfer

Case 1:

Zero Crossing of sine wave to update volatile DAC0 register (using LAT pin)

Case 2:

Fixed Point Crossing of sine wave to update volatile DAC0 register (using LAT pin)

Indicates where LAT pin pulses active (volatile DAC0 register updated).

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