DA6503.005

14 December 2016

27 (34)

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.

The VDD level monitoring measurement is started

by writing configuration data to the measurement

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.

VDD level monitoring model

The VDD level monitoring model for output code is following.











 





VDD

b

a

CODEFS

CODE

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.

CODEFS

CODE

a

b

VDD





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).

20000

50000

80000

110000

140000

170000

200000

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

VDD [V]

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

0

50000

100000

150000

200000

250000

CODE [LSB]

Figure 9. CODE(VDD) at VDD level monitoring

Figure 10. VDD(CODE) at VDD level monitoring