January 1998 - Linear Technology

Linear Technology Chronicle •

January 1998

A Showcase of Linear Technology’s Focus Products

Linear Technology Chronicle

January 1998 Vol. 7 No. 1

Product of the Month

The LT1308’s small size, operating

frequency and low power consumption

make this micropower switcher appropriate

for many new portable products that require

a high current capability using a single cell.

The LT1308 is pin compatible with the

LT1307 micropower PWM switching regu-

lator which has a 600mA switching current

capability. This permits the same basic

design to support two different power levels

without costly redesign.

The LT1308 is offered in an SO-8

package and is available in commercial and

industrial versions from stock. A data sheet

and evaluation samples are available by con-

tacting your local Linear Technology sales

office. For more information, visit our web

site at www.linear-tech.com.

600kHz Boost Switcher in SO-8 Delivers

5W from Single Li-Ion Cell

The LT

1308 is a micropower 600kHz

fixed frequency PWM switching regulator

that incorporates a power switch capable of

handling a 2A peak current with a voltage

drop of only 300mV. It also contains a low-

battery detector with a 200mV reference.

The LT1308 can operate with an input volt-

age as low as 1V and delivers 5V at a load

current of 1A (Figure 1) from a single Li-Ion

cell or 3.3V at 300mA from a single NiCd

cell. High efficiency is maintained over a

load range of 1mA to 1A (Figure 2). The

LT1308’s no-load quiescent current is

100µA and it shuts down to less than 3µA.

Constant frequency 600kHz operation keeps

switching noise away from sensitive 455kHz

IF frequencies, important for pager and other

wireless applications. It is well-suited for

applications of a low duty cycle pulsed

nature, such as two-way “answer-back” pag-

ers, cell phones, camera flash units, latching

relay energizers and handheld printers.

The LT1308 features Burst Mode

operation for improved efficiencies at light

loads. Fixed 600kHz current mode operation

allows the use of very small, surface mount-

able components. A 10µF ceramic bypass

capacitor is the only input capacitance

required when operating from a low imped-

ance source such as a NiCd or NiMH battery.

Inductor size and cost is also reduced by

using standard 5µH surface mountable

devices.

LOAD CURRENT (mA)

EFFICIENCY (%)

95

90

85

80

75

70

65 10 100 1000

1308 F01a

= 4.2V

= 3.6V

= 3V

Figure 1. The LT1308 Boost Converter

Contains a Low-Battery Detector with a

200mV Reference. It Delivers 5V at a

Load Current of up to 1A from a

Single Li-Ion Cell

Figure 2. High Efficiency Is

Maintained over a 1mA to 1A Load

Range. The LT1308’s Burst Mode

Operation Maintains Efficiency

at Light Loads

Low Dropout Linear

Regulator in SO-8

Delivers Up to 700mA

with Just 20

Quiescent Current

The LTC

1234 is a micropower CMOS

low dropout linear regulator that is adjust-

able from 2.5V to 10V output for load

currents up to 700mA. It has a typical drop-

out voltage of 250mV for a 5V output with a

500mA load and for a 3.3V output with

250mA output current, the dropout is only

150mV. Typical quiescent current is just

20µA because the LTC1234’s internal

700mA P-channel pass transistor draws no

base current. In fact, the device draws less

than 30µA over an extended temperature

range, independent of output load current.

The adjustable output allows the LTC1234

in an SO-8 package to be used in a variety

of battery-powered, space limited applica-

tions—such as notebook computers and

portable instruments where extended battery

life is crucial.

Continued on page 3

Inside This Issue:

LTC1416: 14-Bit 400ksps ADC Achieves 80dB SINAD at Nyquist, Consumes Only 75mW ...2

LTC1067: Universal Dual Filter in SSOP Offers Rail-to-Rail Operation with 3V Supply ..........2

LT1307B: 12V Wall Cube to 5V/400mA DC/DC Converter Is 85% Efficient ............................ 3

Latest

New Products Catalog and Selection Guides

Now Available........................................ 4

, LTC and LT are registered trademarks of Linear Technology

Corporation. Burst Mode is a trademark of Linear Technology

Corporation.

LT1308

L1

4.7µH

4.2V TO 3V

LBO

LBI



47k

R2

100k

5V

R1

301k



22nF

1308F01

C1

10µF

C2

100µF

Li-Ion

CELL

GND

SHDN

C1: CERAMIC

C2: AVX TPS SERIES

D1:INTERNATIONAL RECTIFIER 10BQ015

L1: COILTRONICS CTX5-1

 COILCRAFT DO3316-472



Linear Technology Chronicle •

January 1998

14-Bit 400ksps ADC Achieves 80dB SINAD at

Nyquist, Consumes Only 75mW

den by an external source to improve tem-

perature or time stability. The LTC1416’s

three-state parallel interface easily connects

to DSP and microprocessor parallel ports. It

also has a separate convert start input pin

and a data ready signal (BUSY) pin to facili-

tate these connections.

The LTC1416 14-bit ADC is available

in a 28-pin SSOP package. Contact your

local Linear Technology sales office for a

data sheet and evaluation samples or visit

our web site at www.linear-tech.com for

more information.

The 400ksps LTC1416 14-bit analog-

to-digital converter (ADC) delivers 80dB

SINAD and –90dB total harmonic distortion

(THD) at the Nyquist input frequency of

200kHz while drawing only 75mW from

±5V supplies. The LTC1416’s full-scale

input range is ±2.5V. Maximum DC specifi-

cations include ±1LSB DNL and ±1.25LSB

INL over temperature (see Figure 1). It

offers a simple and cost-effective solution

for upgrading performance of 12-bit data

conversion systems wherever low power

operation is essential.

At 100kHz, the LTC1416 delivers

80.5dB of SINAD, –93dB THD and –95dB

spurious-free dynamic range. The

LTC1416’s differential input sample-and-

hold can acquire single-ended or differential

input signals up to its 15MHz bandwidth.

The 60dB common mode rejection allows

users to eliminate ground loops and common

mode noise by measuring signals differen-

tially from the source. Figure 2 shows a

typical application for the LTC1416 as a low

power, 400ksps sampling ADC. It is avail-

able in a 28-pin SSOP package.

The LTC1416 is capable of going into

two power shutdown modes—nap and sleep,

to save power during inactive periods. In nap

frequency error typically less than ±0.2%.

The LTC1067-50 has a ratio of 50:1 and

consumes just 1mA—less than half the cur-

rent of the LTC1067.

Using a double-sampled architecture,

which places aliasing and imaging compo-

nents at twice the clock frequency, the

LTC1067’s dynamic range on a single 3.3V

supply is over 80dB and noise is less than

Figure 2. Frequency Response of Filter in

Figure 1 Has a Center Frequency Error of

Less Than

0.2%

FREQUENCY (kHz)

4.0

GAIN (dB)

6.0

1067 • TA02

4.5 5.0 5.5

0

–10

–20

–30

–40

Universal Dual Filter in

SSOP Offers Rail-to-Rail

Operation with 3V Supply

rail-to-rail 2nd order filter sections, together

with three to five resistors, allows various

filter functions to be quickly designed—such

as bandpass, lowpass, notch and allpass filter

responses. Like all switched-capacitor

filters, the LTC1067’s corner or center

frequency is adjustable with the clock

frequency. The LTC1067’s internal clock-

to-center frequency ratio is 100:1 with center

Figure 1. The LTC1416 ADC

Guarantees ±1.25LDB INL (Max)

over Temperature but It’s Typically

Only ±0.5LSB

Linear Technology Corporation intro-

duces an SSOP-16 version of its LTC1067

rail-to-rail, low noise, universal dual filter

building block. The smaller SSOP package

occupies an area less than half that of an

SO-16, the package in which the LTC1067

was originally introduced and 86% less area

than a 16-pin DIP package. It operates from

a single 3V to ±5V supply with rail-to-rail

input and output operation and draws only

2.5mA. The smaller SSOP package com-

bined with its high performance at low

supply voltages makes the LTC1067 an

excellent choice for small, portable filters for

data acquisition and telecommunications.

The LTC1067 is the evolutionary

descendant of the MF10 and the LTC1060

4th order filter but with greatly improved

specifications. Each of the LTC1067’s two

Continued on page 4

Figure 1. The LTC1067 Configured as a

Single 3.3V Supply Rail-to-Rail 4th Order

5kHz Bandpass Filter

0.1µF

1067 TA01

LTC1067



NC



SA

LPA

BPA

HPA/NA

INV A

CLK

AGND

–



SB

LPB

BPB

HPB/NB

INV B

3.3V

R32, 200k

R22, 10k

R31, 200k

R21, 10k

R11

200k

R12, 200k

OUT

1µF

CLK

= 500kHz

TOTAL OUTPUT NOISE: 90µV

RMS



S/N RATIO: 80dB

OUTPUT CODE

INTEGRAL NONLINEARITY (LSB)

16384

1416 TA02

4096 8192 12288

1.0

0.5

0

–0.5

–1.0 2048 6144 10240 14336

mode only the digital logic and reference is

powered up so it can wake up and convert

immediately. In sleep mode all bias currents

are shut down and only leakage current

remains. Wake-up time from sleep mode is

slower since the reference circuit must

power up and settle for full 14-bit accuracy.

In sleep mode it consumes just 10µW and in

nap mode only 4mW.

The internal 2.5V precision reference

can be used for external circuitry or overrid-

Figure 2. The LTC1416 14-Bit ADC

Includes an Internal Reference and

High Dynamic Range Sample-and-

Hold. It Operates from ±5V Supplies

and Draws Only 75mW

While Converting

1

2

3

4

5

6

7

8

9

10

11

12

13

28

27

26

25

24

23

22

21

20

19

18

17

16

15



–A



REF



REFCOMP

AGND

D13(MSB)

D12

D11

D10

D9

D8

D7

D6

DGND



BUSY

CS

CONVST

RD

SHDN

D0

D1

D2

D3

D4

LTC1416

10µF

1µF

DIFFERENTIAL

ANALOG INPUT

(–2.5V TO 2.5V)

10µF

–5V

PARALLEL

OUTPUT

(BITS 6 TO 13) PARALLEL

OUTPUT

(BITS 0 TO 5)

µP

CONTROL

LINES

1416 TA01

REF



OUTPUT

2.50V

Linear Technology Chronicle •

January 1998

Application of the Month

12V Wall Cube to 5V/400mA DC/DC Converter Is 85% Efficient

100 150 200

LOAD CURRENT (mA)

EFFICIENCY (%)

250 300 350 400

1307 F02

VIN = 8V

VIN = 12V

VIN = 18V

OUT

0.5V/DIV

0.5A/DIV

LOAD

0.3A/0.15A

50µs/DIV

Figure 3. Load-Step Response;

the Load Changes from

150mA to 300mA

Figure 2. Efficiency Peaks at 85%;

It Is Above 80% over an Input

Range of 8V to 18V

LTC1234 from page 1

The LTC1234 has internal thermal lim-

iting designed to protect the device during

overload conditions. Its SHDN pin (see

Figure 1) allows the regulator to be shut

down to a 5µA quiescent current while the

comparator and reference remain alive. It

also has an internal micropower comparator

with an open-drain output—useful for sys-

tem or battery monitoring.

The LTC1234 is offered in an SO-8

package and is available from stock. For a

data sheet and evaluation samples, contact

your local Linear Technology sales office or

visit our web site at www.linear-tech.com

for more information.

IN

5.25V TO 12V* 1

C2

10µF750k100pF

249k

680k

249k

= 5V

OUT

≤ 500mA

NMI

µP

*POWER DISSIPATION LIMITED 

BY THERMAL RESISTANCE

1234 TA01

OUT

LBI LBO

SENSE

SHDN

GND

LTC1234

C1

10µF

Figure 1. LTC1234 Regulator Offers a Very Low Dropout Combined

with a Constant Low Quiescent Current. It Provides an Adjustable

2.5V to 10V Output Voltage Which is Maintained by the Sense Pin

Reference, Held at 1.226V to Ground

tor to drop the voltage to 5V, a 400mA load

means the linear regulator must dissipate

5W under worst-case conditions. To deal

with this heat, you must provide adequate

heat sinking, increasing your product’s size

The ubiquitous 12V wall cube, power

source of countless electronic products,

generates an unregulated DC voltage

between 8V and 18V, depending on line

voltage and load. If you use a linear regula-

Figure 1. This Negative Buck Converter Delivers 5V at 400mA

from a 7V to 25V Input

SHDN VIN

GND

U1

LT1307B

Q2

2N3904

10k

30k

Q1

2N3904

1µF

CERAMIC

C2

10µF

CERAMIC

1N5818

L1

22µH

R3

100k

Q3

2N3906

C1

33µF

25V

5V

400mA

L1 = SUMIDA CD54-220

12V

UNREGULATED

SUPPLY

–

R2

42.2k, 1%

R1

12.1k

1000pF

1307 F01

and weight. Additionally, the heat is some-

times objectionable to customers. These

factors can negate the cost advantage of a

linear regulator. Figure 1’s circuit, a nega-

tive buck converter, delivers 5V at loads up

to 400mA from a 7V to 25V input with

peak efficiency of 85%, eliminating the

need for a heat sink. Since the LT1307B

(U1) is intended for use with a low input

voltage, Q1 and Q2 are used to make a

simple preregulator, providing 1.9V for

U1’s VIN pin. The IC switches at 600kHz,

allowing a low cost 22µH inductor and

10µF ceramic output capacitor to be used.

Q3 is needed to level shift the output volt-

age because U1’s feedback pin is referenced

to the negative input. Output ripple mea-

sures 10mVP-P at a load of 400mA. The

circuit’s efficiency is detailed in Figure 2

and response to a load step from 150mA to

300mA is shown in Figure 3. Input bypass

capacitor C1 sees worst-case RMS ripple

current equal to one-half the output current

and should have an ESR of less than 0.5Ω.

Take care during construction to keep

R1-R3 and Q3 close to U1’s FB pin and

away from the SW pin to prevent unwanted

coupling. Use a ground plane and keep

traces for the power components short and

direct.

Although it might seem unsettling that

the negative side of the wall cube is not

grounded, remember that the wall cube out-

put floats. The circuit merely regulates the

negative side, rather than the more conven-

tional positive side.

Linear Technology Chronicle •

January 1998

Linear Technology Corporation • 1630 McCarthy Blvd. • Milpitas, CA 95035-7417 • (408) 432-1900 • FAX: (408) 434-0507 • www.linear-tech.com • For Literature Only: 1-800-4-LINEAR

Linear Technology

Products Are

Distributed By:

Almac/Arrow

Arrow/Schweber

Arrow/Zeus

Digi-Key

Electrosonic

Gerber Electronics

Farnell Electronics

Marshall Industries

Phase 1

Latest

New Products Catalog and Selection Guides

Now Available

The Fall/Winter 1997 New Products

Catalog and Selection Guides has just

arrived, hot off the press, available on

request at no charge. It provides an excellent

overview of all new products introduced dur-

ing the past six months as well as selection

guides for Linear Technology’s entire prod-

uct line. Section 1 contains data sheet

summaries for 37 new products, complete

with a brief product summary, key features,

schematics of typical applications and pack-

age pinouts. The selection guides provide

overviews of the products by performance

and application. You’ll also find a complete

section on Design Tools, listing hundreds of

currently available application and design

notes, all catalogs and technical publications,

as well as the latest versions of our design

software. Much of this material is also avail-

able on our web page: www.linear-tech.com

for immediate viewing. Contact your local

Linear Technology sales office for a copy of

the new Fall/Winter 1997 New Products

Catalog.

40µVRMS. Figure 1 shows the LTC1067 as a

3.3V 4th order bandpass filter and Figure 2

shows its frequency response. With LTC’s

FilterCAD

software (Version 1.956 or

later), a user can easily implement a dual

2nd order filter or a single 4th order filter

just by entering the desired filter characteris-

tics, such as cutoff frequency, ripple and

stopband attenuation. The latest version of

FilterCAD is available on the LinearView

CD-ROM (Version 2.0, 4/97) and on our

web site, www.linear-tech.com.

Factory mask programmable versions of

the LTC1067 with on-chip thin film resistors

and custom clock-to-cutoff frequency ratios

are available in an SO-8 package to realize

application specific monolithic filters. Con-

tact the Factory for more information.

The LTC1067 and LTC1067-50 in

SO-16 and SSOP-16 packages are immedi-

ately available in volume in both com-

mercial and industrial temperature versions.

Contact your local Linear Technology sales

office for a data sheet and evaluation

samples. For more information, visit our

web site at www.linear-tech.com.

LTC1067 from page 2

FilterCAD and LinearView are trademarks of Linear

Technology Corporation.