LTC2668CUJ-12TRPBF View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC2668CUJ-12TRPBF
Linear Technology
'LTC2668CUJ-12TRPBF' PDF : 28 Pages View PDF
LTC2668
Operation
allows the use of an external clock or logic signal to toggle
the DAC outputs between A and B. The signals from these
controls are combined as shown in Figure 8.
If the toggle function is not needed, tie TGP (Pin 20) to
ground and leave the toggle select register in its power-on
reset state (cleared to zero). Input registers A then function
as the sole input registers, and registers B are not used.
Toggle Select Register (TSR)
The Toggle Select command (1100b) syntax is shown in
Figure 6. Each bit in the 16-bit TSR data field controls the
DAC channel of the same name: T0 controls channel 0,
T1 channel 1,…, and Tx controls channel x.
The toggle select bits (T0, T1,..., T15) have a dual function.
First, each toggle select bit controls which input register
(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.
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.
TOGGLE SELECT
DON’T CARE
TOGGLE SELECT BITS (16 BITS, ONE FOR EACH CHANNEL)
1 1 0 0 X X X X T15 T14 T13 T12 T11 T10 T9 T8 T7 T6 T5 T4 T3 T2 T1 T0
MSB
LSB
2668 F06
Figure 6. Toggle Select Syntax
GLOBAL
TOGGLE COMMAND
DON’T CARE
GLOBAL
TOGGLE
BIT
1 1 0 1 X X X X X X X X X X X X X X X X X X X TGB
2668 F07
Figure 7. Global Toggle Syntax
2668fa
20
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