Datasheet

27
LTC1966
sn1966 1966fas
TROUBLESHOOTING GUIDE
Top Ten LTC1966 Application Mistakes
1. Circuit won’t work–Dead On Arrival–no power drawn.
– Probably forgot to enable the LTC1966 by pulling
Pin␣ 8 low.
Solution: Tie Pin 8 to Pin 1.
2. Circuit won’t work, but draws power. Zero or very
little output, single-ended input application.
– Probably didn’t connect both input pins.
Solution: Tie both inputs to something. See “Input
Connections” in the Design Cookbook.
4. Gain is low by a few percent, along with other screwy
results.
– Probably tried to use output in a floating, differential
manner.
Solution: Tie Pin 6 to a low impedance. See “Output
Connections” in the Design Cookbook.
TYPE 7136
ADC
LTC1966
HI
31
30
5
6
LO
V
OUT
OUT RTN
1966 TS04
GROUND PIN 6
5. Offsets perceived to be out of specification because 0V
in ≠ 0V out.
– The offsets are not specified at 0V in. No RMS-to-
DC converter works well at 0 due to a divide-by-zero
calculation.
Solution: Measure V
IOS
/V
OOS
by extrapolating read-
ings > ±5mV
DC
.
6. Linearity perceived to be out of specification particu-
larly with small input signals.
– This could again be due to using 0V in as one of the
measurement points.
Solution: Check Linearity from 5mV
RMS
to
500mV
RMS
.
– The input offset voltage can cause small AC linear
ityerrors at low input amplitudes as well. See “Error
Analyses” section.
Possible Solution: Include a trim for input offset.
APPLICATIO S I FOR ATIO
WUUU
3. Screwy results, particularly with respect to linearity
or high crest factors; differential input application.
– Probably AC-coupled both input pins.
Solution: Make at least one input DC-coupled. See
“Input Connections” in the Design Cookbook.
LTC1966
CONNECT PIN 3
IN1
2
3
NC
IN2
1966 TS02
LTC1966
IN1
2
3
IN2
1966 TS03
DC-COUPLE ONE INPUT
LTC1966
DC-CONNECT ONE INPUT
IN1
2
3
IN2