
I-84
EPSON
S1C62740 TECHNICAL HARDWARE
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (A/D Converter)
The A/D converter of the S1C62740 has a built-in reference voltage
generation circuit and it generates a reference voltage VR1 for
resistance measurement and a reference voltage VR2 for voltage
measurement. VR1 and VR2 may also be adjusted from outside. Use
of the external adjustment or the internal adjustment can be
selected by the mask option.
In addition, VR1 can be impressed from outside.
Reference voltage
generation circuit
Fig. 4.12.7
Reference voltage generation
circuit configuration
(internal adjustment mode)
(1) Reference voltage VR1
The reference voltage VR1 is generated by the internal voltage
regulation circuit and is used as the reference voltage for resistance
measurement and for the creation of reference voltage for voltage
measurement. The output voltage of VR1 and the temperature
characteristics are as follows.
Output voltage:
-475.0 mV (GND reference, Typ.)
Temperature characteristics: 150 ppm/°C (Typ.)
When the built-in VR1 is used, it is necessary to generate a refer-
ence voltage by writing "1" into the register VRON before doing A/D
conversion. When not using the built-in VR1, you should turn the
reference voltage generation circuit OFF by setting the VRON to "0"
to reduce current consumption.
When the internal adjustment mode has been selected by the mask
option, write "1" into the registers VRON and VRAON to turn the
internal adjustment ON.
(2) Reference voltage VR2
The VR2 is the reference voltage for voltage measurement and is
created by voltage dividing VR1 by means of a resistance. The VR2
output voltage and error are as follows.
Output voltage:
-163.8 mV (GND reference, Typ.)
Error:
±1.0% (during internal adjustment mode)
(3) External adjustment for VR1 and VR2
When the external adjustment mode has been selected by the mask
option, VR1 and VR2 can be adjusted from outside using external
resistors. When adjusting externally, connect the resistance for
adjustment as shown in Figure 4.12.8. Turn the internal adjust-
ment OFF by setting the register VRAON to "0". You should set the
VR1 and VR2 so that the result of measurement error of the A/D
converter becomes a minimum value.
VR1
+
–
VRA
VR2
GND
0.1
F