Datasheet

23
90067814f
LTM9008-14/
LTM9007-14/LTM9006-14
APPLICATIONS INFORMATION
Figure 8. Reference Circuit
Figure 9. Using an External 1.25V Reference
Reference
The LTM9008-14/LTM9007-14/LTM9006-14 has an inter-
nal 1.25V voltage reference. For a 2V input range using
the internal reference, connect SENSE to V
DD
. For a 1V
input range using the internal reference, connect SENSE
to ground. For a 2V input range with an external reference,
apply a 1.25V reference voltage
to SENSE (Figure 9).
The input range can be adjusted by applying a voltage to
SENSE that is between 0.625V and 1.30V. The input range
will then be 1.6 • V
SENSE
. The reference is shared by all
eight ADC channels, so it is not possible to independently
adjust the input range of individual channels.
The V
REF
, SENSE, REFH and REFL pins are internally
bypassed, as shown in Figure 8.
V
REF
1.25V
SENSE
TIE TO V
DD
FOR 2V RANGE;
TIE TO GND FOR 1V RANGE;
RANGE = 1.6 • V
SENSE
FOR
0.65V < V
SENSE
< 1.300V
0.1µF2.2µF
INTERNAL ADC
HIGH REFERENCE
BUFFER
90067814 F08
LTM9008-14
5Ω
0.8x
DIFF AMP
INTERNAL ADC
LOW REFERENCE
1.25V BANDGAP
REFERENCE
0.625V
RANGE
DETECT
AND
CONTROL
1µF
0.1µF
0.1µF
0.1µF
SENSE
1.25V
EXTERNAL
REFERENCE
1µF
90067814 F09
LTM9008-14