What’s New with LTspice IV?

What’s New with LTspice IV?
Gabino Alonso
Stepping Parameters
in LTspice IV
NEW HOW-TO VIDEOS
Stepping Parameters
video.linear.com/103
There are two ways to examine a circuit
by changing the value of a parameter.
You can manually enter each value,
then resimulate the circuit, or you can
use the .STEP command to sweep across
a range of values in a single simulation
run for a side-by-side comparison. This
video provides an overview of the basic
steps for using the .STEP command to
perform repeated analysis of a circuit.
FULLY DIFFERENTIAL OPERATIONAL
AMPLIFIER DEMO CIRCUITS
(from Tyler Hutchison)
Analyzing and interfacing with fully
differential op amps in simulation may
prove more complicated than with
familiar, single-ended output op amps.
These demo circuits provide examples of
interfacing to fully differential amplifiers
What is LTspice IV?
LTspice® IV is a high performance SPICE
simulator, schematic capture and waveform
viewer designed to speed the process of power
supply design. LTspice IV adds enhancements
and models to SPICE, significantly reducing
simulation time compared to typical SPICE
simulators, allowing one to view waveforms for
most switching regulators in minutes compared
to hours for other SPICE simulators.
LTspice IV is available free from Linear
Technology at www.linear.com/LTspice. Included
in the download is a complete working version of
LTspice IV, macro models for Linear Technology’s
power products, over 200 op amp models, as
well as models for resistors, transistors and
MOSFETs.
32 | April 2012 : LT Journal of Analog Innovation
Follow @LTspice on Twitter for
up-to-date information on models, demo circuits,
events and user tips: www.twitter.com/LTspice
including single-ended and differential
impedance matching, noise analyses,
mixer and high speed ADC signal chain
models, and gain modification of fixedgain amplifiers with external resistors.
• LTC6405: Fully differential ADC driver
with simplified mixer and ADC models
www.linear.com/LTC6405
• LTC6400-20: Single-ended impedance
matching for fully differential amplifiers www.linear.com/LTC6400-20
• LTM®8048: Isolated µModule
DC/DC converter with LDO post regulator
(4V–30V to 6V at 100m A & 5V at
100m A) www.linear.com/LTM8048
• LTC6400-20: Differential impedance
matching for fully differential amplifiers www.linear.com/LTC6400-20
• LTC6400-20: Noise simulation
for fully differential amplifiers
www.linear.com/LTC6400-20
• LTC6401-8: Unity gain for fully differential
amplifiers with internal feedback
resistors www.linear.com/LTC6401-8
• LTC6404-1: Impedance matching and
noise measurements for fully differential
amplifiers www.linear.com/LTC6404
NEW DEMO CIRCUITS
µModule Regulators
• LTM8052: 36V, 5A, 2-quadrant CVCC stepdown µModule regulator (6V–36V to
2.5V at ±5A) www.linear.com/LTM8052
Switching Regulators
• LT3758: High efficiency SEPIC (8V–72V to
5V at 2A) www.linear.com/LT3758
• LT3759: Boost with low input voltage
range (1.8V–4.5V to 5V at 2A)
www.linear.com/LT3759
• LT3759: SEPIC with wide input voltage
range (2.8V–36V to 12V at 1A)
www.linear.com/LT3759
Download this demo circuit showing impedance matching and noise
measurements for fully differential amplifiers www.linear.com/LTC6404
design ideas
• LTC4000/LTC3891: High voltage high
current step-down, PowerPath
controller & Li-ion battery
charger (24V–60V to 16.8V at 6A)
www.linear.com/LTC4000
Amplifiers, References,
Comparators and TimerBlox ® IC s
• LT6108/LTC6994: Energy-tripped
circuit breaker with
automatic delayed retry
(5V–80V input, 500m A threshold)
www.linear.com/LT6108
PARAMETRIC PLOTS
Plotting results in LTspice IV is as easy as clicking
on a node to show voltage, or a component to show
current—the trace is then displayed in the waveform
viewer. In transient analysis, the horizontal axis
defaults to showing time, but you can always change
the horizontal axis to show other quantities (such as
current) to validate model parameters.
To change the default settings of the x-axis:
1.Click on a node/component to plot its voltage/
current in the waveform viewer.
2.Move the cursor to the horizontal axis of the
waveform viewer (the cursor will turn into a ruler)
and left-click.
3.In the Horizontal Axis dialog, enter an expression for
the “Quantity Plotted.”
4.Click OK.
Happy simulations!
NEW DEVICE
MACRO MODELS
Switching Regulators
• LT8582: Dual 3A boost/inverting/
SEPIC DC/DC converter with fault
protection www.linear.com/LT8582
• LTC3103: 1.8µ A quiescent current, 15V, 300m A synchronous
step-down DC/DC converter
www.linear.com/LTC3103
• LTC3115V–1: 40V, 2A synchronous
buck-boost DC/DC converter
www.linear.com/LTC3115-1
• LTC3613: 24V, 15A monolithic
step-down regulator with
differential output sensing
www.linear.com/LTC3613
• LTC3839: Fast, accurate, 2-phase,
single-output step-down
DC/DC controller with differential output
sensing www.linear.com/LTC3839
• LTC3866: Current mode synchronous
controller for sub-mΩ DCR sensing
www.linear.com/LTC3866
• LTC3876: Dual DC/DC controller
for DDR power with differential
VDDQ sensing and ±50m A VTT reference
http://www.linear.com/LTC3876
This parametric plot compares the
instantaneous power dissipation
(Alt + click on component) of
an LTC4358 5A ideal diode to a
Schottky diode. In this example,
the quantity plotted on the
horizontal axis has been changed
from the default of “time” to
“load current.” The resulting
plot confirms the advantage
of the LTC4358 as a low loss
replacement to Schottky diodes
in high current diode applications.
More information is available at
www.linear.com/LTC4358.
• LTC4366: High voltage surge stopper
www.linear.com/LTC4366 n
LTC4358-BASED, LOW LOSS,
IDEAL DIODE SOLUTION
Power User Tip
Download the LTspice IV demonstration circuit for this energy-tripped
circuit breaker with automatic delayed retry at www.linear.com/LT6108
R3
3.66k
LOAD SUPPLY
5V TO 80V DC
R4
0.667V/A 40.2k
LT6108-2
CURRENT
SENSE AMP
R1
100Ω
RSENSE
10mΩ
–
+
5V
+
60ms TO 350ms
DELAY TIMER
LT1783
IN
R6
64.9k
R3
6.34k
400mV
–
+
LRELAY
Q1
NPN
R2
1.62k
5V
–
COMPARATOR
CIRCUIT BREAKER
Hot Swap™ Controllers and
Surge Stoppers
• LTC4232: 5A integrated Hot Swap
controller www.linear.com/LTC4232
SCHOTTKY DIODE
(B530C)
R14
15k
5
0
CURRENT SENSE
COMPARATOR
500mA TRIP
THRESHOLD
OUT
LTC6994-2
GND
SET
5V
R7
301k
R10
10k
ROPTIONAL
931k
V+
5V
DIV
R8
172k
R9
100k
CLOSED
OPEN
LOAD
April 2012 : LT Journal of Analog Innovation | 33