LTM9006-14_15 Datasheet, PDF (24/38 Pages) Linear Technology – 14-Bit, 65Msps/40Msps/ 25Msps Low Power Octal ADCs

LTM9008-14/
LTM9007-14/LTM9006-14
Applications Information
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 LTM9008-14
1.25V
1µF
5Ω _{1.25V BANDGAP}
REFERENCE
0.625V
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
SENSE
0.1µF
RANGE
DETECT
AND
CONTROL
0.1µF
INTERNAL ADC BUFFER
HIGH REFERENCE
2.2µF
0.1µF
0.1µF
0.8x
DIFF AMP
INTERNAL ADC
LOW REFERENCE
Figure 8. Reference Circuit
90067814 F08
1.25V
EXTERNAL
REFERENCE
LTM9008-14
SENSE
1µF
90067814 F09
Figure 9. Using an External 1.25V Reference
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For more information www.linear.com/LTM9008-14
90067814fa