Datasheet
SLAS412− DECEMBER 2003
www.ti.com
52
The ’AIC26 architecture offers no inherent rejection of noise or voltage variation in regards to using an external reference
input. This is of particular concern when the reference input is tied to the power supply. Any noise and ripple from the supply
appears directly in the digital results. While high frequency noise can be filtered out, voltage variation due to line frequency
(50 Hz or 60 Hz) can be difficult to remove.
The ground pins must be connected to a clean ground point. In many cases, this is the analog ground. Avoid connections
which are too near the grounding point of a microcontroller or digital signal processor. If needed, run a ground trace directly
from the converter to the power supply entry or battery connection point. The ideal layout includes an analog ground plane
dedicated to the converter and associated analog circuitry.
CONVERSION TIME CALCULATION FOR THE ’AIC26
Auxiliary Measurement Operation
The time needed to make temperature, auxiliary, or battery measurements is given by:
t +
NJN
AVG
ƪ
ǒ
N
BITS
) 1
Ǔ
8MHz
ƒ
conv
) n
1
) n
2
ƫ
) 1Nj t
OSC
) 15 t
OSC
) n
3
t
OSC
where:
n
1
= 6 ; if ƒ
conv
= 8 MHz
7 ; if ƒ
conv
≠ 8 MHz
n
2
= 24 ; if measurement is for TEMP1 case
12 ; if measurement is for other than TEMP1 case
n
3
= 0 ; if external reference mode is selected
3 ; if t
REF
= 0 µs or reference is programmed for power up all the time.
1 + t
REF
/125 ns; if t
REF
≠
0 µs and reference needs to power down between conversions.
t
REF
is the reference power up delay time.
Sample,Conversion &
Averaging for
BAT1 input
Reading
BAT1−Data
Register
(PAGE01H,REG01H,
[D15−D14 = 01])
Waiting for Host to write
into REG−00 of PAGE−01
Waiting for Host to
write into REG−00
of PAGE−01
REG−00 of
PAGE−01
is updated
for
BAT1 Scan
Mode
Wait for Reference Powerup Delay in case
of internal ref. mode if applicable.
DAV
SS Deactivated
The time needed for continuous AUX conversion in scan mode is given by:
t +
NJN
AVG
ƪ
ǒ
N
BITS
) 1
Ǔ
8MHz
ƒ
conv
) n
1
) 12
ƫ
) 1Nj t
OSC
) 8 t
OSC
where:
n
1
= 6 ; if ƒ
conv
= 8 MHz
7 ; if ƒ
conv
≠ 8 MHz
NOTE
:
The above equation is valid only from second conversion onwards.