Linear Technology LTC1966 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 427B

DESCRIPTION

Demonstration circuit 427B features the LTC1966/7/8 Pre-
cision Micro-power true RMS-to-DC converter. It incorpo-
rates a variety of passive components to support configu-
rations for varied applications. Two optional post-filters
are included to improve averaging ripple and step re-
sponse performance, as illustrated in the Design Cook-
book section of the datasheet. DC427B-A contains the
LTC1966, DC427B-B contains the LTC1967, and DC427B-
C contains the LTC1968.
The LTC1966/7/8 is a patent-pending ∆Σ-based RMS to
DC converter that is simpler, more accurate, more flexible,

QUICK START PROCEDURE

Table 1 shows the Jumper positions and their respective
effects. Be sure that the jumpers are in the bold (default)
positions. Refer to Figure 1 for the connection diagram
and follow the procedure below:
Connect the power supplies as shown. The power labels
1.
of V and V directly correspond to pins 4 and 7 of the
SS DD
LTC1966/7/8, respectively, and combinations other than
±5V may be used. The LTC1966 accepts dual ±5V sup-
plies, and the LTC1967/8 accept single 5V supplies; re-
fer to the respective datasheet and the Supply Voltages
section of this Quick Start Guide.
Apply an input signal to convert from RMS to DC to
2.
IN1. Any signal generator may be used; the LTC1966
works up to 1V with V
PEAK
There is a 50Ω termination to ground on DC427B;
NOTE:
remove if driving IN1 or IN2 with an op-amp.
Observe the output with a digital voltmeter (DVM) con-
3.
nected to terminals E4 and E7.
The LTC1966/7/8 output impedance is high, and
NOTE:
10MΩ DVM input impedance will cause up to –
1% gain error.
To use the optional output filters, reposition JP3 and
4.
observe the output at terminal E1 or E8.
= 5V.
DD
RMS TO DC CONVERTER
LTC1966/LTC1967/LTC1968
and lower power than conventional log-antilog RMS-to-DC
converters. The LTC1966/7/8 accepts single-ended or dif-
ferential inputs with rail-to-rail common-mode range. One
standout feature of the LTC1966/7/8 is its superior linear-
ity, which allows hassle-free system calibration at any in-
put voltage.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Table 1: DC427B Jumpers (default positions in bold)
JUMPER SETTING EFFECT
JP1 Top LTC1966/7/8 shutdown
Bottom LTC1966/7/8 always enabled
Removed LTC1966/7/8 controlled by E2 input
to DC427
JP2 Left IN1 grounded
Right IN1 active (J1 connected to pin 2)
JP3 Top Vout (pin 5) connected to optional
DC-Accurate post-filter
Right Vout connected to output terminal
E4, no filter
Bottom Vout connected to optional buffered
post-filter
JP4 Left IN2 grounded
Right IN2 active (J2 connected to pin 3)
Top OutRtn (pin 6) grounded
JP5
Bottom OutRtn connected to VSS
Removed OutRtn floating; drive with voltage at
terminal E7
JP6 Left LTC1966/7/8 negative supply (Pin
1) connected to VSS
Right Pin 1 grounded
1