
Linear Technology Magazine • February 1997
2
EDITOR’S PAGE
Issue Highlights
To mark the new year, we have a
collection of exciting new parts from
the design gurus at LTC. This issue’s
lead article features the new LT1425
isolated flyback converter, which pro-
vides a one-chip solution for low
voltage circuitry, such as local area
networks, isolation amplifiers and
telephone interfaces. The LT1425 is a
275kHz current mode controller with
an integral 1.25A switch, designed to
provide well regulated, isolated volt-
ages from 3V–20V sources.
Other power products featured in
this issue include the LTC1474 and
LTC1475 ultralow quiescent current,
high efficiency step-down switching
regulators. These regulators draw only
10µA at no load and require only four
external components to make a com-
plete, high efficiency (up to 92%)
step-down regulator. Low component
count and the parts’ tiny MSOP pack-
ages provide a minimum-area solution
to meet the limited space require-
ments of portable applications.
Another boon to the designers of
portable, battery-powered equipment
is the LTC1473 dual PowerPath switch
driver, which simplifies the design of
circuitry for switching between two
batteries or a battery and an AC
adapter. Presently, switching between
power sources is implemented with
discrete components—regulators,
comparators, references, glue logic,
MOSFET switches and drivers. These
solutions are expensive and occupy a
lot of printed circuit board space. The
LTC1473 drives low loss N-channel
MOSFET switches that direct power
in the main power path of a single or
dual rechargeable battery system, the
type found in most notebook comput-
ers and other portable equipment.
In the filter department, this issue
introduces the LTC1560-1, a high
frequency, continuous-time, low noise
filter. This device is a single-ended
input and output, 5th order elliptic
lowpass filter with a pin-selectable
cutoff frequency of 1MHz or 500kHz.
It requires no external components or
clocks and provides better than 60dB
LTC in the News…
Results of LTC’s second fiscal quarter
underscore the company’s standing as
an industry leader. Net sales for the
second fiscal quarter of 1997, ended
December 29, 1996, were $90,080,000.
Although this was a decrease of 6% over
net sales of $96,017,000 for the second
quarter of the previous year, this actu-
ally represented phenomenally good
performance, as we will see in just a
moment.
LTC reported net income for the quar-
ter of $31,631,000 or $0.40 per share,
a decrease of 8% from the second quar-
ter of the previous year. Sequentially,
the results for the second quarter were
essentially flat as compared to net sales
and income for the quarter ended Sep-
tember 29, 1996 of $90,063,000 and
$31,358,000 or $0.40 per share, re-
spectively. A cash dividend of $0.05 will
be paid on February 12, 1997 to share-
holders of record on January 24, 1997.
According to Robert H. Swanson,
president and CEO, “Although we en-
tered the quarter with reduced backlog,
we were able to achieve flat sequential
sales and profits with our return on
sales continuing to lead the industry. In
addition, cash and short-term invest-
ments grew by approximately $20 mil-
lion in the quarter. Customers’ demand
picked up moderately throughout the
quarter and our shorter lead times en-
abled us to ship some of their demand
within the quarter. We believe our mar-
ket is improving and we are optimistic
about the future.”
It’s becoming known around the
nation’s regional stock exchanges that
LTC is a leading pace setter and vital
indicator of the economic condition of
the electronics industry. For many
months, the Bloomberg Silicon Valley
Index and the Dean Witter Silicon Val-
ley Stock Index have included LTC’s
business performance in their assess-
ment of the industry.
Now, the New York-based Reuters
America News Service reports that the
Philadelphia Stock Exchange has added
two chip companies—one of which is
LTC—and an equipment maker to its
Semiconductor Index to replace three
stocks the exchange has removed. Late
last month, the exchange added Linear
Technology Corp. (LLTC), Xilinx Inc.
(XLNX.O) and Lam Research Corp.
(LRCX.O). To us at LTC, this move is
further proof that even in the realm of
high finance, “it’s a linear world.”
of stopband attenuation and 75dB
SNR, with only 0.3dB passband ripple.
In the data conversion area, we
debut the LTC1594 and LTC1598,
micropower 12-bit ADCs, which fea-
ture a 4- or 8-channel multiplexer,
respectively. These devices include
an auto shutdown feature that re-
duces power dissipation when the
converter is inactive. Nominal power
dissipation with the converter clocked
at 320kHz is typically 1.6mW. Each
ADC includes a simple, efficient serial
interface that reduces interconnects
and, thereby, possible noise sources.
Reduced interconnections also reduce
board size and allow the use of pro-
cessors having fewer I/O pins, both of
which help reduce system costs.
For data communications, this is-
sue introduces the low cost LT1328
IrDA data receiver. This device con-
tains all the necessary circuitry to
convert current pulses from an exter-
nal photodiode to a digital TTL output
while rejecting unwanted lower fre-
quency interference. The LT1328 plus
six external components are all that
is required to make an IrDA-compat-
ible receiver. Power requirements for
the LT1328 are minimal: a single 5V
supply and 2mA of quiescent current.
This issue includes a varied selec-
tion of Design Ideas, including three
power supplies, a battery charger that
doubles as the main step-down con-
verter, a voltage controlled limiter for
video, a detector circuit for 470MHz
signals, and an evaluation of battery
life under a variety of load conditions.
Penultimately, we present Design
Information on the LT2078/LT2079
and LT2178/LT2179, improved
single-supply, precision surface
mount op amps, and the LT1387
single 5V multiprotocol transceiver.
We conclude with a selection of New
Device Cameos.