LTC2662 datasheet(21/28 Pages) AD

21 / 28 page

LTC2662

Rev 0

For more information www.analog.com

OPERATION

Toggle Select Register (TSR)

The toggle select command (1100b) syntax is shown in

Figure 7. Each bit in the 5-bit TSR data field controls the

DAC channel of the same name: T0 controls channel 0,

T1 channel 1… and T4 controls channel 4.

The toggle select bits (T0, T1… T4) have a dual function.

First, each toggle select bit controls which input regis-

ter (A or B) receives data from a write-code operation.

When the toggle select bit of a given channel is high,

write-code operations are directed to input register B of

the addressed channel. When the bit is low, write-code

operations are directed to input register A. Secondly, each

toggle select bit enables the corresponding channel for a

toggle operation.

Writing to Input Registers A and B

Having chosen channels to toggle, write the desired codes

to input registers A for the chosen channels; then set

the channels’ toggle select bits using the toggle select

command; and finally, write the desired codes to input

registers B. Once these steps are completed, the channels

are ready to toggle. For example, to set up channel 3 to

toggle between codes 4096 and 4200:

1) Write code channel 3 (code = 4096) to register A

00000011 00010000 00000000

2) Toggle select (set bit T3)

11000000 00000000 00001000

3) Write code channel 3 (code = 4200) to register B

00000011 00010000 01101000

The write code of step (3) is directed to register B because

in step (2), bit T3 was set to 1. Channel 3 now has input

registers A and B holding the two desired codes, and is

prepared for the toggle operation.

Note: After writing to register B, the code for register A

can still be changed. The state of the Toggle Select bit

determines to which register (A or B) a write is directed.

First, toggle select bit T3 has to be reset to 0:

11000000 00000000 00000000

Then write the new register A code. Let’s say the new code

is 4300, so the instruction would be:

00000011 00010000 11001100

After that, set toggle select bit T3 to 1 again [step 2 above].

It is not necessary to write to register B again; channel 3

is ready for the toggle operation.

Toggling Between Registers A and B

Once input registers A and B have been written to for all

desired channels and the corresponding toggle-select bits

are set high, as in the previous example, the channels are

ready for toggling.

The LTC2662 supports three types of toggle operations:

a first in which all selected channels are toggled together

using the SPI port; a second in which all selected channels

are toggled together using an external clock or logic sig-

nal; and a third in which any combination of channels can

be instructed to update from either input register A or B.

TOGGLE SELECT

2662 F07

MSB

LSB

TOGGLE SELECT BITS

(1-BIT/CHANNEL)

DON’T CARE

GLOBAL TOGGLE

COMMAND

2662 F08

TGB

GLOBAL

TOGGLE

BIT

DON’T CARE

Figure 7. Toggle Select Syntax

Figure 8. Global Toggle Syntax

LTC2662 Datasheet(PDF) 21 Page - Analog Devices

LTC2662 Datasheet(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL