286
CHAPTER 15 D/A CONVERTER
PD78054, 78054Y
ANOn
R
R
1
C
• The input impedance of the buffer amplifier is R
1
.
• If R
1
is not connected, the output becomes
undefined when RESET is low.
µ
15.5 Cautions Related to D/A Converter
(1) Output impedance of D/A converter
Because the output impedance of the D/A converter is high, use of current flowing from the ANOn pins (n =
0,1) is prohibited. If the input impedance of the load for the converter is low, insert a buffer amplifier between
the load and the ANOn pins. In addition, wiring from the ANOn pins to the buffer amplifier or the load should
be as short as possible (because of high output impedance). If the wiring may be long, design the ground
pattern so as to be close to those lines or use some other expedient to achieve shorter wiring.
Figure 15-3. Use Example of Buffer Amplifier
(a) Inverting amplifier
(b) Voltage-follower
(2) Output voltage of D/A converter
Because the output voltage of the converter changes in steps, use the D/A converter output signals in general
by connecting a low-pass filter.
(3) AV
REF1
pin
When only either one of the D/A converter channels is used with AV
REF1
< V
DD
, the other pins that are not used
as analog outputs must be set as follows:
•
Set PM13x bit of the port mode register 13 (PM13) to 1 (input mode) and connect the pin to V
SS
.
•
Set PM13x bit of the port mode register 13 (PM13) to 0 (output mode) and the output latch to 0, to output
low level from the pin.
µ
PD78054, 78054Y
ANOn
R
1
C
R
2
• The input impedance of the buffer amplifier is R
1
.
Summary of Contents for PD78052
Page 2: ...2 MEMO ...
Page 8: ...8 MEMO ...
Page 16: ...16 MEMO ...
Page 36: ...36 MEMO ...
Page 158: ...158 MEMO ...
Page 174: ...174 MEMO ...
Page 240: ...240 MEMO ...
Page 260: ...260 MEMO ...
Page 340: ...340 MEMO ...
Page 392: ...392 MEMO ...
Page 438: ...438 MEMO ...
Page 482: ...482 CHAPTER 20 REAL TIME OUTPUT PORT MEMO ...
Page 510: ...510 MEMO ...
Page 524: ...524 MEMO ...
Page 560: ...560 MEMO ...
Page 576: ...576 MEMO ...
Page 598: ...598 MEMO ...
Page 602: ...602 MEMO ...