Datasheet

LTC2261-12
LTC2260-12/LTC2259-12
20
226112fc
For more information www.linear.com/LTC2261-12
applicaTions inForMaTion
25Ω
25Ω
200Ω
200Ω
0.1µF
A
IN
+
A
IN
–
12pF
0.1µF
V
CM
LTC2261-12
226112 F07
–
–
+
+
ANALOG
INPUT
HIGH SPEED
DIFFERENTIAL
AMPLIFIER
0.1µF
Figure 7. Front-End Circuit Using a High Speed
Differential Amplifier
Reference
The LTC2261-12/LTC2260-12/LTC2259-12 have 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
.
V
REF
REFH
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
1.25V
REFL
0.1µF2.2µF
INTERNAL ADC
HIGH REFERENCE
BUFFER
226112 F08
5Ω
0.8x
DIFF AMP
INTERNAL ADC
LOW REFERENCE
1.25V BANDGAP
REFERENCE
0.625V
RANGE
DETECT
AND
CONTROL
1µF
0.1µF
0.1µF
LTC2261-12
Figure 8. Reference Circuit
SENSE
1.25V
EXTERNAL
REFERENCE
1µF
1µF
V
REF
226112 F09
LTC2261-12
Figure 9. Using an External 1.25V Reference
The V
REF
, REFH and REFL pins should be bypassed as
shown in Figure 8. The 0.1µF capacitor between REFH
and REFL should be as close to the pins as possible (not
on the back side of the circuit board).