
S1C63406 TECHNICAL MANUAL
EPSON
95
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (SVD Circuit)
4.12 SVD (Supply Voltage Detection) Circuit
4.12.1 Configuration of SVD circuit
The S1C63406 has a built-in SVD (supply voltage detection) circuit, so that the software can find when the
source voltage lowers.
Turning the SVD circuit ON/OFF and the SVD criteria voltage setting can be done with software.
Figure 4.12.1.1 shows the configuration of the SVD circuit.
V
Detection output
Data
bus
DD
VSS
SVDON
SVDS3
|
SVDS0
Criteria voltage
setting circuit
SVD circuit
SVDDT
Fig. 4.12.1.1 Configuration of SVD circuit
4.12.2 SVD operation
The SVD circuit compares the criteria voltage set by software and the supply voltage (VDD terminal–VSS
terminal) and sets its results into the SVDDT latch. By reading the data of this SVDDT latch, it can be
determined by means of software whether the supply voltage is normal or has dropped.
The criteria voltage can be set for the 16 types shown in Table 4.12.2.1 by the SVDS3–SVDS0 registers.
When "0" is written to the SVDS3–SVDS0 register, the supply voltage detection voltage is set to 1.30 V.
When "8" is written to the SVDS3–SVDS0 register, it is set to 2.10 V.
Table 4.12.2.1 Criteria voltage setting
SVDS3
0
SVDS2
1
0
SVDS1
1
0
1
0
SVDS0
1
0
1
0
1
0
1
0
Criteria
voltage (V)
2.00
1.90
1.80
1.70
1.60
1.50
1.40
1.30
SVDS3
1
SVDS2
1
0
SVDS1
1
0
1
0
SVDS0
1
0
1
0
1
0
1
0
Criteria
voltage (V)
2.80
2.70
2.60
2.50
2.40
2.30
2.20
2.10
When the SVDON register is set to "1", source voltage or external voltage detection by the SVD circuit is
executed. As soon as the SVDON register is reset to "0", the result is loaded to the SVDDT latch and the
SVD circuit goes OFF.
To obtain a stable detection result, the SVD circuit must be ON for at least l00 sec. So, to obtain the SVD
detection result, follow the programming sequence below.
1. Set SVDON to "1"
2. Maintain for 100 sec minimum
3. Set SVDON to "0"
4. Read SVDDT
When the SVD circuit is ON, the IC draws a large current, so keep the SVD circuit off unless it is.