RMS-to-DC Converter. LTC1968 Datasheet

LTC1968 Converter. Datasheet pdf. Equivalent

Part LTC1968
Description RMS-to-DC Converter
Feature U U LTC1968 Precision Wide Bandwidth, RMS-to-DC Converter FEATURES ■ High Linearity: 0.02% Lineari.
Manufacture Linear
Datasheet
Download LTC1968 Datasheet



LTC1968
LTC1968
Precision Wide Bandwidth,
RMS-to-DC Converter
FEATURES
High Linearity:
0.02% Linearity Allows Simple System Calibration
Wide Input Bandwidth:
Bandwidth to 1% Additional Gain Error: 500kHz
Bandwidth to 0.1% Additional Gain Error: 150kHz
3dB Bandwidth Independent of Input Voltage
Amplitude
No-Hassle Simplicity:
True RMS-DC Conversion with Only One External
Capacitor
Delta Sigma Conversion Technology
Ultralow Shutdown Current:
0.1µA
Flexible Inputs:
Differential or Single Ended
Rail-to-Rail Common Mode Voltage Range
Up to 1VPEAK Differential Voltage
Flexible Output:
Rail-to-Rail Output
Separate Output Reference Pin Allows Level Shifting
Small Size:
Space Saving 8-Pin MSOP Package
U
APPLICATIO S
True RMS Digital Multimeters and Panel Meters
True RMS AC + DC Measurements
DESCRIPTIO
The LTC®1968 is a true RMS-to-DC converter that uses an
innovative delta-sigma computational technique. The ben-
efits of the LTC1968 proprietary architecture, when com-
pared to conventional log-antilog RMS-to-DC converters,
are higher linearity and accuracy, bandwidth independent
of amplitude and improved temperature behavior.
The LTC1968 operates with single-ended or differential in-
put signals and accurately supports crest factors up to 4.
Common mode input range is rail-to-rail. Differential in-
put range is 1VPEAK, and offers unprecedented linearity. The
LTC1968 allows hassle-free system calibration at any in-
put voltage.
The LTC1968 has a rail-to-rail output with a separate out-
put reference pin providing flexible level shifting; it oper-
ates on a single power supply from 4.5V to 5.5V. A low power
shutdown mode reduces supply current to 0.1µA.
The LTC1968 is packaged in the space-saving MSOP pack-
age, which is ideal for portable applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected under U.S. Patent Numbers 6,359,576, 6,362,677 and 6,516,291
TYPICAL APPLICATIO
Single Supply RMS-to-DC Converter
4.5V TO 5.5V
DIFFERENTIAL
INPUT
0.1µF
OPT. AC
COUPLING
V+
IN1 OUTPUT
LTC1968
IN2 OUT RTN
EN GND
1968 TA01
CAVE
10µF
+
VOUT
Linearity Performance
0.2
LTC1968, ∆Σ
0
–0.2
–0.4
–0.6 CONVENTIONAL
LOG/ANTILOG
–0.8
60Hz SINEWAVE
–1.0
0 100 200
300
VIN (mV ACRMS)
400 500
1968 TA01b
1968f
1



LTC1968
LTC1968
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage
V+ to GND ............................................................. 6V
Input Currents (Note 2) ..................................... ±10mA
Output Current (Note 3) ..................................... ±10mA
ENABLE Voltage ......................................... –0.3V to 6V
OUT RTN Voltage ........................................ –0.3V to V+
Operating Temperature Range (Note 4)
LTC1968C/LTC1968I ......................... – 40°C to 85°C
Specified Temperature Range (Note 5)
LTC1968C/LTC1968I ......................... – 40°C to 85°C
Maximum Junction Temperature ......................... 150°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND 1
IN1 2
IN2 3
NC 4
8 ENABLE
7 V+
6 OUT RTN
5 VOUT
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 220°C/ W
ORDER PART
NUMBER
LTC1968CMS8
LTC1968IMS8
MS8 PART MARKING
LTAFG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The temperature grade (I or C) is indicated on the shipping container.
ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating
temperature range, otherwise specifications are TA = 25°C. V+ = 5V, VOUTRTN = 2.5V, CAVE = 10µF, VIN = 200mVRMS, VENABLE = 0.5V
unless otherwise noted.
SYMBOL
PARAMETER
Conversion Accuracy
GERR Low Frequency Gain Error
VOOS
VOOS/T
LINERR
PSRRG
Output Offset Voltage
Output Offset Voltage Drift
Linearity Error
Power Supply Rejection
VIOS Input Offset Voltage
VIOS/T
Input Offset Voltage Drift
Additional Error vs Crest Factor (CF)
CF = 3
CF = 5
Input Characteristics
VIMAX
IVR
ZIN
Maximum Peak Input Swing
Input Voltage Range
Input Impedance
CMRRI
VIMIN
PSRRI
Input Common Mode Rejection
Minimum RMS Input
Power Supply Rejection
CONDITIONS
50Hz to 20kHz Input (Notes 6, 7)
(Notes 6, 7)
(Note 11)
50mV to 350mV (Notes 7, 8)
(Note 9)
(Notes 6, 7, 10)
(Note 11)
60Hz Fundamental, 200mVRMS
60Hz Fundamental, 200mVRMS
Accuracy = 1% (Note 14)
Average, Differential (Note 12)
Average, Common Mode (Note 12)
(Note 13)
(Note 9)
MIN TYP MAX
UNITS
±0.1 ±0.3
%
±0.4 %
0.2 0.75
mV
2 10 µV/°C
±0.02 ±0.15
%
±0.02 ±0.20
%/V
±0.25
%/V
0.4 1.5
mV
2 10 µV/°C
0.2
5
mV
mV
1
0
1.05
V+
1.2
100
50 400
5
250 700
V
V
M
M
µV/V
mV
µV/V
1968f
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