August 1997 - Linear Technology

Linear Technology Chronicle •

August 1997

A Showcase of Linear Technology’s Focus Products

Linear Technology Chronicle

August 1997 Vol. 6 No. 8

Product of the Month

Inside This Issue:

500ksps Micropower 10-Bit ADCs Fit in 8-Lead MSOP........................................................... 2

Driving Multiple Video Cables with the LT®1206 ..................................................................... 3

1.2V, 10µA Shunt Reference in SO-8 Guarantees 25ppm/°C and 0.05% Initial Accuracy ......3

5V Versions of the LT1460 Precision Reference Now Available ............................................. 4

Triple RS232 Transceiver Now Has ±15kV ESD Protection ................................................... 4

The LTC

1624 is a current mode

switching regulator controller that drives an

external N-channel MOSFET. Operation is

over an input voltage range of 3.5V to 36V

which allows it to be powered from a variety

of batteries and bus voltages. The LTC1624

Versatile, High Efficiency Switching Regulator in

SO-8 Operates Over 3.5V to 36V Range

operates in all standard switching configura-

tions including boost, step-down, inverting

and SEPIC (Figure 1). Its 200kHz fixed fre-

quency PWM operation provides lower

switching noise for RF-sensitive applications

and allows use of small inductors to mini-

Figure 2. The LTC1624 as a High Efficiency

Step-Down Converter

Figure 1. The LTC1624 as a SEPIC Controller Works

Well in Automotive Applications Where the Input Voltage

Can Vary Above and Below the Output Voltage

SENSE

–



/RUN



GND



BOOST

TG

LTC1624

1000pF

100pF



330pF



4.7k

D1

MBRS130LT3



0.1µF

4R2

35.7k

R1

3.92k

OUT



100µF

16V

× 2

M1

Si4412DY

L1a*

L1b*

SENSE



0.068Ω



22µF

35V 22µF

35V

OUT



12V

0.5A



5V TO 15V

1624 F14

*COILTRONICS CTX20-4

0.1µF

SENSE

–



/RUN



GND



BOOST

TG

LTC1624

1000pF

100pF



470pF



6.8k

D1

MBRS340T3



0.1µF

R2

35.7k

R1

20k

OUT



100µF

10V

× 2

M1

Si4412DY

L1

10µH

SENSE



0.05Ω



22µF

35V

× 2

OUT



3.3V



4.8V TO 28V

1624 F01

mize PC board space. The LTC1624 is tar-

geted towards applications requiring up to

36V input and output currents from 1A to

8A. It is ideal for use in automotive and

marine GPS systems, industrial single board

computers and DC power distribution sys-

tems.

In step-down operation, such as shown

in Figure 2, the LTC1624’s output voltage

can range from 1.19V to 30V. The operating

current level is user-programmable via an

external current sense resistor which allows

higher output voltages (especially in boost

mode). A 95% maximum duty cycle pro-

vides low dropout for longer operating time

in portable systems. Peak efficiency in a

3.3V step-down converter approaches 90%

and Burst Mode

operation maintains high

efficiency even at low load currents.

The LTC1624 is screened to the com-

mercial and industrial temperature ranges

and is available from stock in an SO-8 pack-

age.

For a data sheet and evaluation samples,

contact your local Linear Technology sales

office or for more information visit our web

site at www.linear-tech.com.

, LTC and LT are registered trademarks of Linear Technology

Corporation. Burst Mode is a trademark of Linear Technology

Corporation.

Varactor Diode Driver for

Cellular Phones Extends

Frequency Tuning Range

The LTC1340 is a varactor diode

driver specifically targeted for Phase Locked

Loop (PLL) frequency synthesizers in GSM

cellular phone applications. From a 3V sup-

ply, it generates a 5V supply rail to the

internal varactor drive amplifier by means of

a charge pump. The low noise amplifier has

a gain of 2.3, allowing the smaller output

voltage range of the synthesizer phase detec-

tor to drive the varactor diode with a wider

voltage range. The amplifier input stage

includes a built-in offset voltage that allows

Continued on page 2

Linear Technology Chronicle •

August 1997

500ksps Micropower 10-Bit ADCs Fit in 8-Lead MSOP

The LTC1197/LTC1197L and

LTC1199/LTC1199L are single and dual

channel 10-bit analog-to-digital (A/D) con-

verters in an 8-lead MSOP package for 5V

and 3V supply applications where small size,

low power and low cost are critical design

factors. The single channel LTC1197 and

dual channel LTC1199 operate on a single

5V source while achieving sample rates up

to 500kHz and 450kHz, respectively.

The LTC1197L and LTC1199L operate

on a single 3V source and dissipates only

2.2mW of power. Auto shutdown

between conversions reduces supply current

to just 1nA, guaranteeing the lowest operat-

ing power for such power sensitive

applications as bar code readers, touch

screen interfaces and handheld instrumenta-

tion. Their speed and resolution are also

well-suited to baseband signal processing

and demodulation for narrowband wireless

data systems.

All of these devices have a 3-wire serial

interface and include an on-chip 200ns

sample-and-hold. The LTC1197/LTC1197L

have a differential analog input with an

external reference input. The LTC1199/

LTC1199L have a software selectable

2-channel MUX. All have excellent DC per-

formance with ±1LSB INL and 10-bit no

missing codes resolution. The offset error is

±2LSB (maximum) and the gain error is

±4LSB (maximum).

The LTC1197/LTC1197L and

LTC1199/LTC1199L are offered in 8-lead

1

2

3

8

7

6

CS

+IN

–IN

GND



CLK

OUT



REF

LTC1197L

1197/99 TA01

ANALOG INPUT

0V TO 2.7V RANGE

2.7V

1µF

SERIAL DATA LINK TO

ASIC, PLD, MPU, DSP

OR SHIFT REGISTERS

Figure 1. A Single 5V Supply, 500ksps,

10-Bit Sampling A/D Converter

SAMPLING FREQUENCY (kHz)

0.01

SUPPLY CURRENT (µA)

100

1000

10000

100

1197/99 G03

0.1 0.1 110 1000

= 5V

CLK

= 7.2MHz

= 2.7V

CLK

= 3.5MHz

MSOP and SO packages. Parts are screened

to the commercial and industrial temperature

ranges and are available from stock. For

more details, see our web site at

www.linear-tech.com. To obtain a data

sheet and evaluation samples, contact your

local Linear Technology sales office.

LTC1340 from page 1

the output voltage to swing to ground with-

out requiring 0V on the input. This feature

controls the phase detector within its linear

range of operation.

The LTC1340 requires only three exter-

nal surface mount capacitors to implement a

complete varactor driver module, as shown

in Figure 1. It is ideal in enhancing cellular

phone operation on 3V supplies and in wire-

less modems for Internet and PC-to-base-

station wireless networking applications.

Although the output current is only about

Figure 1. The LTC1340 Amplifies the Phase Detector Output to the

VCO in PLL Frequency Synthesizer Systems. The Op Amp Bandwidth

is 125kHz with a 1nF Output Capacitance

LTC1340

PGND

VCO

= 2.3

0V TO 5V

1340 TA01

OUT

LOOP

FILTER SHDN

SHUTDOWN

AGND

270pF

0.1µF

PHASE

DETECTOR

Figure 2. Effective Number of Bits

Frequency Response Curve for LTC1197

20µA, it is sufficient to be used in low sup-

ply voltage instrumentation applications.

The LTC1340 features output referred

noise of 15µVRMS, minimizing frequency

deviation in PLL frequency synthesizer sys-

tems. Figure 2 shows the spectral plot of the

VCO output driven by the LTC1340. The op

amp bandwidth is adjustable from 10kHz to

500kHz by adjusting the output capacitance.

The output typically sinks or sources 20µA,

allowing fast output signal changes with a

typical varactor load. When shut down, the

charge pump disconnects the power to the op

amp, reducing supply current to less than

1µA typically.

The LTC1340 is available in the SO-8

as well as the 8-lead MSOP for size critical

applications. 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.

Figure 2. Spectral Plot of VCO Output

with 300Hz Resolution Bandwidth

FREQUENCY (120kHz/DIV)

0dB

RELATIVE POWER (10dB/DIV)



1340 TA02

900MHz 

= 3V

OUT

= 270pF

Linear Technology Chronicle •

August 1997

Application of the Month

Driving Multiple Video Cables with the LT1206

The combination of a 60MHz

bandwith, 250mA output current capability

and low output impedance makes the

LT1206 ideal for driving multiple video

cables. One concern when driving multiple

transmission lines is the effect of an

unterminated (open) line on the other out-

puts. Since the unterminated line creates a

reflected wave that is incident on the output

of the driver, a nonzero amplifier output

impedance will result in crosstalk to the

other lines. Figure 1 shows the LT1206

connected as a distribution amplifier. Each

line is separately terminated to minimize

the effect of reflections. For systems using

composite video, the differential gain and

phase performance are also important and

have been considered in the internal design

of the device. The differentail phase and

differential gain performance versus supply

is shown in Figures 2 and 3 for 1, 3, 5 and

10 cables. Figure 4 shows the output im-

pedance versus frequency. Note that at

5MHz the output impedance is only 0.6Ω.

Figure 2. Differential Phase

vs Supply Voltage

SUPPLY VOLTAGE (±V)

0.00

DIFFERENTIAL PHASE (DEG)

0.50

AN67 F108

0.40

0.30

0.20

0.10

7 9 11 13

= 15Ω (10 CABLES)

= 30Ω (5 CABLES)

= 50Ω (3 CABLES)

= 150Ω (1 CABLE)

= R

= 560Ω

N PACKAGE

Figure 4. Output Impedance

vs Frequency

FREQUENCY (Hz)

100k

OUTPUT IMPEDANCE (Ω)

1M 100

AN67 F110

0.01

0.1

100

= ±15V

= R

= 560Ω

N PACKAGE

SUPPLY VOLTAGE (±V)

0.00

DIFFERENTIAL GAIN (%)

0.10

AN67 F109

0.08

0.06

0.04

0.02

713

= 15Ω 

(10 CABLES)

= 30Ω (5 CABLES)

= 50Ω 

(3 CABLES)

= 150Ω (1 CABLE)

911

= R

= 560Ω

N PACKAGE

Figure 3. Differential Gain

vs Supply Voltage

Figure 1. LT1206 Distribution Amplifier

–

eIN

AN67 F107

LT1206

75Ω

RF = RG = 560

75Ω

75Ω CABLE

1.2V Shunt Reference in SO-8 Guarantees 25ppm/

C and

0.05% Initial Accuracy, Operates on 10

tee a minimum operating current of only

10µA and low temperature cycling hysteresis.

The compactness of the product makes it

ideal for space limited applications.

The LT1634-1.2 is immediately avail-

able in volume from stock in 8-lead SO or

MSOP surface mount packages (TO-92 pack-

ages will also be released soon). 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 LT1634 is the first device in a

series of precision shunt references—the

initial release in this family being a 1.2V

output device with an initial accuracy of

0.05% and a maximum guaranteed drift of

25ppm/°C. It is stable with any value of out-

put capacitor, including none, saving

components and board space. These features

make it an excellent reference for use in por-

table meters, precision regulators and in data

conversion applications. Advances in design,

processing and packaging techniques guaran-

TEMPERATURE (°C)

–40

REVERSE VOLTAGE CHANGE (mV)

1.5

1634 TA02

–1.0

–20 20

–1.5

–2.0

2.0

1.0

0.5

–0.5

40 60 80 100

IR = 10µA

Figure 1. LT1634 Reference Has Low

Drift Over a Wide Temperature Range

Linear Technology Chronicle •

August 1997

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

5V Versions of the

LT1460 Precision

Reference Now Available

Actual Size of MS8 Versions

The LT1460-5 is a micropower preci-

sion 5V series, bandgap voltage reference

that combines high accuracy and low drift

with low power dissipation and small pack-

aging. The various options available in

electrical grade (shown boldfaced), packag-

ing and temperature grade are described in

Table 1.

LT1460-5

GND

IN OUT

1460-5 TA01

C1

0.1µF

5.9V

TO 20V

Figure 1. LT1460-5 Series Reference

Draws Only 130

A of Supply Current

Electrical Temperature

Part Number Package Grade Range Accuracy Drift

LT1460ACN8-5 8-Lead PDIP A 0°C to 70°C 0.075% 10ppm/°C

LT1460ACS8-5 SO-8 A 0°C to 70°C 0.075% 10ppm/°C

LT1460BIN8-5 8-Lead PDIP B –40°C to 85°C 0.100% 10ppm/°C

LT1460BIS8-5 SO-8 B –40°C to 85°C 0.100% 10ppm/°C

LT1460CCMS8-5 8-Lead MSOP C 0°C to 70°C 0.100% 15ppm/°C

LT1460DCN8-5 8-Lead PDIP D 0°C to 70°C 0.100% 20ppm/°C

LT1460DCS8-5 SO-8 D 0°C to 70°C 0.100% 20ppm/°C

LT1460EIN8-5 8-Lead PDIP E –40°C to 85°C 0.125% 20ppm/°C

LT1460EIS8-5 SO-8 E –40°C to 85°C 0.125% 20ppm/°C

LT1460FCMS8-5 8-Lead MSOP F 0°C to 70°C 0.150% 25ppm/°C

LT1460GCZ-5 TO-92 G 0°C to 70°C 0.250% 25ppm/°C

LT1460GIZ-5 TO-92 G –40°C to 85°C 0.250% 25ppm/°C

Table 1. Commercial and Industrial Grade 5V Versions of the LT1460 Reference

The LT1460 uses temperature compen-

sation and trimmed, precision thin-film

resistors to achieve its high accuracy and is

stable with any value of output capacitor,

including none, saving components and

board space. Drawing a maximum of only

130µA of supply current, the LT1460-5 will

source up to 20mA of output current, mak-

ing it ideal for precision regulator

applications. Figure 1 shows the LT1460 in

the MS8 package.

The LT1460-5 precision reference is

available in 8-lead PDIP, SO and MSOP sur-

face mount packages and in a 3-lead TO-92.

Parts are screened to the commercial and

industrial temperature ranges and are avail-

able from stock. 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.

Triple RS232 Transceiver Now Has

15kV ESD Protection

also available without the shutdown or bias

pin functions. (The BIAS pin keeps the

receiver on while in shutdown.) Contact

your local Linear Technology sales office

for a data sheet and evaluation samples.

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

for more information.

The LT1039A Triple RS232 Transceiver’s

Bus Pins Will Withstand

15kV per the

IEC Model

30k

LT1039A

–

GND

12V

BIAS*

RS232 IN

ON/OFF

LOGIC

 * BIAS PIN USED TO KEEP THE RECEIVER ON 

 WHILE IN SHUTDOWN

 ** 50 Ω RESISTORS MAY BE REQUIRED FOR

 IEC-1000-4-2

 ESD PROTECTION DEPENDING UPON PC BOARD

 AND CONNECTOR LEAD LENGTH

RS232 IN

RS232 OUT

RS232 IN

–12V

1039A TA01

30k

50Ω**

The LT1039A triple RS232 transceiver

has much improved ESD protection for those

applications that must be compliant to the

IEC 1000-4-2, ±15kV Electro-Static Dis-

charge standard. The IEC standard is

mandatory for products to achieve the “CE”

mark for sale into Europe. Each receiver of

the LT1039A will accept up to ±30V input

and can drive either TTL or CMOS logic.

The RS232 drivers accept TTL logic inputs,

and output RS232 voltage levels. The out-

puts are fully protected against overload and

can be shorted to ground or up to ±30V

without damage to the drivers. Additionally,

when the system is shut down or power is

off, the outputs are in a high impedance state

allowing data line sharing. On-chip ESD pro-

tection eliminates the need for external

protection devices.

The LT1039A operates off ±5V to

±12V supplies. The LT1039A is available in

an 18-lead SO surface mount package with a

shutdown pin to reduce power consumption.

A 16-lead SO package (LT1039ACS16) is