AD7225CQ AD [Analog Devices], AD7225CQ Datasheet - Page 11

• Manufacturer Part Number: AD7225CQ
• Description: LC2MOS Quad 8-Bit DAC with Separate Reference Inputs
• Manufacturer: AD [Analog Devices]

REV. B
MICROPROCESSOR INTERFACE
8085A/
Figure 22. AD7225 to 8085A/8088 Interface,
Double-Buffered Mode
E OR 2
Figure 23. AD7225 to 6809/6502 Interface,
Single-Buffered Mode
6809/
8088
6502
Z-80
MREQ
ALE
AD7
AD0
A15
R/W
WR
A15
Figure 24. AD7225 to Z-80 Interface,
Double-Buffered Mode
A15
A8
WR
A0
D7
D0
A8
D7
D0
EN
EN
*
ADDRESS
LATCH
*
DECODE
*
LINEAR CIRCUITRY OMITTED FOR CLARITY
LINEAR CIRCUITRY OMITTED FOR CLARITY
LINEAR CIRCUITRY OMITTED FOR CLARITY
EN
ADDRESS
DECODE
ADDRESS DATA BUS
ADDRESS
DECODE
ADDRESS BUS
DATA BUS
ADDRESS BUS
ADDRESS BUS
DATA BUS
A0
A1
LDAC
WR
DB7
DB0
A0
A1
LDAC
WR
DB7
DB0
AD7225*
AD7225*
A0
A1
LDAC
WR
DB7
DB0
AD7225*
–11–
V
Operating the AD7225 from dual supplies results in enhanced
performance over single supply operation on a number of pa-
rameters as previously outlined. Some applications may require
this enhanced performance, but may only have a single power
supply rail available. The circuit of Figure 26 shows a method of
generating a negative voltage using one CD4049, operated from
a V
as an oscillator. The other four inverters are in parallel and used
as buffers for higher output current. The square-wave output is
level translated to a negative-going signal, then rectified and fil-
tered. The circuit configuration shown will provide an output
voltage of –5.1 V for current loadings in the range 0.5 mA to
9 mA. This will satisfy the AD7225 I
commercial operating temperature range.
SS
DD
CD4049AE
GENERATION
510k
of +15 V. Two inverters of the hex inverter chip are used
1/6
68008
DTACK
Figure 25. AD7225 to 68008 Interface,
Single-Buffered Mode
R/W
A23
AS
A1
D7
D0
CD4049AE
Figure 26. V
5.1k
0.02 F
1/6
*
LINEAR CIRCUITRY OMITTED FOR CLARITY
EN
ADDRESS
DECODE
CD4049AE
CD4049AE
CD4049AE
CD4049AE
1/6
1/6
1/6
1/6
SS
DATA BUS
ADDRESS BUS
Generation Circuit
1N4001
47 F
SS
+
requirement over the
1N4001
+
A0
A1
WR
LDAC
DB7
DB0
AD7225*
AD7225
47 F
510
5V1
–V
OUT