DAC888_15 Datasheet, PDF (5/12 Pages) Analog Devices – 8-BIt LevelTriggered Latch

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DAC-888 BYTEDAC~ 8-BIT HIGH-SPEED "MICROPROCESSOR COMPATIBLE" MULTIPLYING D/A CONVERTER
ilTAllNFORMATION
BYTEOAClI" OAC-888 is a monolithic microprocessor
Ipatible Of A converter consisting of an 8-bit level
Jered latch, control circuitry and one 8-bit multiplying
converter housed in an 18-pin dual in line package (01 P I.
or may vary from nearly 0 to +4.0mA. The full range output
currrent is a linear function of the reference current and is
given by:
255
IFR = 256 X IREF where IREF = 110
OAC-888 accepts 8-bit binary bytes at the data inputs.
il access is accomplished when WR and CE are low.
ing the low state of CE and WR, the latches are trans-
mt, therefore, data should be valid from 100ns prior to WR
CE low until CE or WR high. When CE or WR goes high,
In positive reference applications, an external positive refer-
ence voltage current flows through R1Qinto the VREF(+I ter-
minal of the reference amplifier. Alternatively, a negative
reference may be applied to VREFI-j; reference current flows
data stored in the latches will hold the selected output
from ground through R1Qinto VREF(+) as in the positive refer-
!finitely.
ence case. This negative reference connection has the
advantage of a very high impedance presented at pin 11. The
AlOG INFORMATION
;IC POSITIVE REFERENCE OPERATION
MSB
LSB
DB] DB6 DB5 DB4 DBJ DB2 DBl DBO
O_1]
B ₁₆
S _RREF
O ^{Rl0 10}
5.00R0EVFo-vvv
IREF-
L ₁₁
~ ^{ETE R11}
CE
CONTROL & LATCHES
WR
VREF+
lOUT
VREF-
CaMP V-
DAC
GND
lOUT
V+
12
15
1
O.Ol"F 0.1~
18
0.1"F
14-
'OUT
1J~
'OUT
voltage at pin 10 is equal to and tracks the voltage at pin 11
due to the high gain of the internal reference amplifier. R11
(nominally equal to R1Q) is usedto cancel biascurrent errors;
R" may be eliminated with only a minor increase in error.
For most applications the tight relationship between IREFand
IFR will eliminate the need for trimming IREF. If required,
full-scale trimming may be accomplished by adjusting the
value of R 1Qor by using a potentiometer for R1Q.An improved
method of full-scale trimming which eliminates potentio-
BASIC NEGATIVE REFERENCE OPERATION
MSB
LSB
DB] DB6 DB5 DB4 DBJ DB2 DB1 DBO
4=t
16
WR
CONTROL & LATCHES
-=-
-=-
DR FIXED REFERENCE. Tn OPERATION TYPICAL
IALUES ARE:
IREF = 2.5000k
111' RREF
+VREF 255
IFR = RREF x 256
lOUT + lOUr = 'FR
FOR ALL LOGIC STATES
RREF
.L
'V\I\,
R10 101
- ^R11 11
-VREF
IVREF+
DAC
14
lOUT
-1J 'OUT
FERENCE AMPLIFIER SET-UP
! DAC-888 is a multiplying D/A converter in which the
put current is the product of a digital number and the
ut reference current. The reference current may be fixed
SIC UNIPOLAR NEGATIVE OPERATION
MSB
LSB
DB] DB6 DB5 DB4 DBJ DB2 DB1 DBo
. 'FR -VREF x 255
RREF 256
NOTE: RREF SETS IFS: R11 IS FOR BIAS CURRENT CANCELLATION
AND IS EQUAL TO RREF'
EOUT
FULL-SCALE
FULL-SCALE
DB7 DB6 DBS DB4 DB3 DB2 DB1 DBO lamA
1 1 1 1 1 1 1 1 1.992
-1 LSB 1 1 1 1 1 1 1 0 1.984
lamA
0.000
0.008
Eo
-4.980
-4.960
HALF-SCALE + 1 LSB 1 0 0 0 0 0 0 1 1008 0.984 -2.520
HALF-SCALE
1 0 0 0 0 0 0 0 1.000 0.992 -2500
HALF-SCALE -1 LSB 0 1 1 1 1 1 1 1 0.992 1.000 -2.480
ZERO-SCALE +1 LSB 0 0 0 0 0 0 0 1 0.008 1.984 -0.020
ZERO-SCALE
0 0 0 0 0 0 0 0 0000 1.992 -0.000
Eo
0.000
-0.020
-2.460
-2.480
-2.500
-4.960
-4980
._{r~~~~>Z0uv0Z<<JJrr::'::J}
0_rIJ-
~_.......
:0:2
11-105
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7/89, Rev. 8