Data Sheet AS8446

Revision 1.8, Date 2005-03-17

Page 30 of 35

Battery Voltage Monitor and Over / Under Voltage Detection

The Battery voltage monitor has to deliver an analog voltage Vbat_mon in the 5V range which is proportional to the high voltage

supply Vbat (normally VDDH = Vbat). The measurement range of the supply voltage Vbat is programmable via the register

R11<2:0> to adapt the AS8446 to different application supply voltages.

Programming of the MEASUREMENT RANGE of Vbat (programmed by register R11<2:0>

à VBAT_RANGE)

PARAMETER

Programming Register R11

SYMBOL

MIN

MAX

UNIT

NOTE

R11= 0

à VBAT_RANGE = 5

20

V

R11= 1

à VBAT_RANGE = 8

32

V

R11= 2

à VBAT_RANGE = 10

40

V

R11= 3

à VBAT_RANGE = 15

60

V

Programmable

Measurement

Voltage Ranges

of Vbat

R11= 4

à VBAT_RANGE = 20

80

V

(1)

Note (1):

The programmable value of VBAT_RANGE determines the max. value of Vbat measurable by the voltage

monitor (condition: Vbat / VBAT_RANGE < 4 V).

Note (2):

VBAT must not exceed the specified abs. Max. ratings (see Table 3)

PARAMETER

SYMBOL

MIN

MAX

UNIT

NOTE

Tolerance of the division factor

∆VBAT_RANGE

- 6

+ 6

%

Tolerance of the programmed over voltage threshold

∆Vovervolt

-10

+10

%

Tolerance of the programmed ounder voltage threshold

∆Vundervolt

-10

+10

%

a)

Programming of the OVER VOLTAGE detection level of Vbat (programmed by register R12<2:0>

à OVER_VOLT and

R11<2:0>

à VBAT_RANGE)

Remark:

The maximum over voltage limit of Vbat for safe functionality of AS8446 is limited to Vbat < 30 V

and must be respected by appropriate programming.

Programmable steps of OVER_VOLT = 0.25 V * VBAT_RANGE = (1.25 or 2.0 or 2.5 or 3.75 or 5.0 ) V

OVER_VOLT = 0.25 V * VBAT_RANGE * (R12 + 9) = 11.25 V ... 80 V

During an over voltage situation the write access to the Three Wire Interface is blocked and the driver is

switched off.

b)

Programming of the UNDER VOLTAGE detection level of Vbat (programmed by register R13<2:0>

à UNDER_VOLT

and R11<2:0>

à VBAT_RANGE)

Remark:

The minimium Vbat for full functionality of AS8446 is limited to Vbat > 6.5 V (except for Low-battery-

mode reduced functionality is still given between 6V and 6.5V, see Table 4 Operating Conditions).

Programmable steps of UNDER_VOLT = 0.25 V * VBAT_RANGE = (1.25 or 2.0 or 2.5 or 3.75 or 5.0 ) V

UNDER_VOLT = 0.25 V * VBAT_RANGE * (R13 + 1) = 1.25 V ... 40 V