Datasheet

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DAC8555
SLAS475B – NOVEMBER 2005 – REVISED OCTOBER 2006
The DAC8555 also supports a number of different DB16 is a power-down flag. If this flag is set, then
load commands. The load commands can be DB15 and DB14 select one of the four power-down
summarized as follows: modes of the device as described in Table 1 . If DB16
= 1, DB15 and DB14 no longer represent the two
DB21 = 0 and DB20 = 0: Single-channel store.
MSBs of data, but represent a power-down condition
The temporary register (data buffer) corresponding to
described in Table 1 . Similar to data, power-down
a DAC selected by DB18 and DB17 is updated with
conditions can be stored at the temporary registers
the contents of SR data (or power-down).
of each DAC. It is possible to update DACs
simultaneously either with data, power-down, or a
DB21 = 0 and DB20 = 1: Single-channel update.
combination of both.
The temporary register and DAC register
corresponding to a DAC selected by DB18 and DB17
Refer to Table 2 for more information.
are updated with the contents of SR data (or
power-down).
Table 1. DAC8555 Power-Down Modes
DB21 = 1 and DB20 = 0: Simultaneous update. A
PD0 PD1 PD2
channel selected by DB18 and DB17 gets updated
(DB16) (DB15) (DB14) OPERATING MODE
with the SR data, and simultaneously, all the other
1 0 0 Output high impedance
channels get updated with previous stored data (or
1 0 1 Output typically 1k Ω to GND
power-down) from temporary registers.
1 1 0 Output typically 100k Ω to GND
DB21 = 1 and DB20 = 1: Broadcast update. If
1 1 1 Output high impedance
DB18 = 0, then SR data gets ignored, all channels
get updated with previously stored data (or
power-down). If DB18 = 1, then SR data (or
power-down) updates all channels.
Power-down/data selection is as follows:
Table 2. Control Matrix
DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13-DB0
Don't
0 0 LD 1 LD 0 Care DAC Sel 1 DAC Sel 0 PD0 MSB MSB-1 MSB-2...LSB DESCRIPTION
0 0 X 0 0 0 Data Write to buffer A with data
0 0 X 0 1 0 Data Write to buffer B with data
0 0 X 1 0 0 Data Write to buffer C with data
0 0 X 1 1 0 Data Write to buffer D with data
Write to buffer (selected by DB17 and DB18) with
0 0 X (00, 01, 10, or 11) 1 See Table 1 0
power-down command
Write to buffer with data and load DAC (selected by
0 1 X (00, 01, 10, or 11) 0 Data
DB17 and DB18)
Write to buffer with power-down command and load
0 1 X (00, 01, 10, or 11) 1 See Table 1 0
DAC (selected by DB17 and DB18)
Write to buffer with data (selected by DB17 and DB18)
1 0 X (00, 01, 10, or 11) 0 Data and then load all DACs simultaneously from their
corresponding buffers.
Write to buffer with power-down command (selected by
1 0 X (00, 01, 10, or 11) 1 See Table 1 0 DB17 and DB18) and then load all DACs
simultaneously from their corresponding buffers.
Broadcast Modes
0 Simultaneously update all channels of DAC8555 with
X X 1 1 X X X X
data stored in each channels temporary register.
X X 1 1 X 1 X 0 Data Write to all channels and load all DACs with SR data
Write to all channels and load all DACs with
X X 1 1 X 1 X 1 See Table 1 0
power-down command in SR.
16
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