ltc1967 Linear Technology Corporation, ltc1967 Datasheet - Page 25

• Manufacturer Part Number: ltc1967
• Description: Precision Extended Bandwidth, Rms-to-dc Converter
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
7. Output is noisy with >50kHz inputs.
8. Large errors occur at crest factors approaching, but
9. Screwy results, errors > spec limits, typically 1% to 5%.
– This is a fundamental characteristic of this topol-
less than 4.
– Insufficient averaging.
– High impedance (50k ) and high accuracy (0.1%)
ogy. The LTC1967 is designed to work very well
with inputs of 20kHz or less. It works okay as high
as 1MHz, but it is limited by aliased
Solution: Bandwidth limit the input or digitally filter
the resulting output.
Solution: Increase C
DC Waveforms” section for discussion of output
droop.
require clean boards! Flux residue, finger grime, etc.
all wreak havoc at this level.
Solution: Wash the board.
U
KEEP BOARD CLEAN
LTC1967
AVE
U
. See “Crest Factor and AC +
W
1967 TS09
U
noise.
10. Gain is low by 1% or more, no other problems.
– Probably due to circuit loading. With a DMM or a
– Loading can also be caused by cheap averaging
10 scope probe, Z
output is 50k , resulting in – 0.5% gain error.
Output impedance is higher with the DC accurate
post filter.
Solution: Remove the shunt loading or buffer the
output.
capacitors.
Solution: Use a high quality metal film capacitor
for C
AVE
V
OUT
.
OUT RTN
LTC1967
LOADING DRAGS DOWN GAIN
50k
5
6
IN
200mV
= 10M . The LTC1967
10M
–0.5%
RMS
DMM
IN
1967 TS10
DCV
mV
LTC1967
25
1967f