DA6503.005
14 December 2016
APPLICATION INFORMATION
VDD Level Monitoring Configuration
The MAS6503 has VDD level monitoring feature to
measure supply voltage level which is useful
especially in battery operated systems. In systems
in which VDD can vary the VDD level monitoring
could be also used to compensate VDD
dependency.
In the proper configuration it is necessary to disable
both regulator (ENREG=0) and offset (ENOFS=0)
and select the widest input signal conversion range
373mV (ISCR=00) and the VDD level monitoring
measurement (PTS=01).
Typically the smallest over sampling ratio (OSR)
selection 256 offers sufficient resolution for the
VDD level monitoring.
The VDD level monitoring measurement is started
by writing configuration data to the measurement
control registers 1 (E2/62HEX) and 2 (E3/63HEX).
VDD level monitoring model
The VDD level monitoring model for output code is following.
b
CODE CODEFS a
VDD
The output has inverse relationship to supply voltage VDD. The OSR selects full scale output code range value
CODEFS. See Electrical Characteristics for CODEFS at different OSR values.
The typical VDD level monitoring model parameter values a and b are as follows.
a=1.7064
b=2.9123
Note that these parameter values are subject to about two percent variations.
The supply voltage VDD can be solved from the output result as follows.
b
VDD
CODE
a
CODEFS
Figure 9 presents typical output code as function of supply voltage at OSR=256 (CODEFS=227328).
Figure 10 present supply voltage as function of output code at OSR=256 (CODEFS =227328).
4.1
200000
3.9
3.7
170000
3.5
3.3
140000
3.1
2.9
110000
2.7
2.5
80000
2.3
2.1
1.9
1.7
50000
20000
0
50000
100000
150000
200000
250000
1.8
2
2.2 2.4 2.6 2.8
3
3.2 3.4 3.6
VDD [V]
CODE [LSB]
Figure 9. CODE(VDD) at VDD level monitoring
Figure 10. VDD(CODE) at VDD level monitoring
27 (34)
MAS [ MICRO ANALOG SYSTEMS ]
