January 1996 - Linear Technology

Linear Technology Chronicle •

January 1996

Product of the Month

A Showcase of Linear Technology's Focus Products

Linear Technology Chronicle

January 1996 Vol. 5 No. 1

Low Power Single Chip DCE/DTE V.35 Transceiver

, LTC and LT are registered trademarks of Linear Technology Corporation.

Continued on page 2

Single 5V 250kbaud RS232/RS485 Multiprotocol Transceiver Is Software Configurable....... 2

LTC1430 Provides Efficient GTL Supply ................................................................................. 3

5ppm/°C, 0.05% Accurate, Industrial Grade Voltage Reference in

8-Lead Surface Mount Package ...............................................................................................4

Inside This Issue:

Figure 2. LTC1346A Is Available in a

24-Lead Surface Mount Package for

Industrial Temperature Range

Applications

puts feature ±10kV ESD protection.

The LTC1346A is an ideal V.35 inter-

face chip for modems, data routers and other

telecommunications applications with ±5V

available. For single 5V applications, the

single supply LTC1345 V.35 chip includes a

charge pump to generate –5V from 5V.

The LTC1346A is available in the

24-lead plastic surface mount package.

Device operating temperature is specified

form 0°C to 70°C for the commercial

LTC1346ACS and –40°C to 85°C for the

industrial version, LTC1346AIS. Contact

your local Linear Technology sales office

for a data sheet and free evaluation samples

of the LTC1346A

resistor network IC available from Beckman

Industrial Technologies.

The LTC1346A features three current

output differential transmitters and three

differential receivers. The transmitters can

be configured for DTE or DCE operation or

shut down using three Select pins. In the

shutdown mode, the supply current is re-

duced to below 1

A. The LTC1346A

transceiver operates up to 10Mbaud. All

transmitters feature short-circuit protection.

Both the transmitter outputs and receiver in-

The LTC

1346A is a single chip trans-

ceiver that provides the differential clock

and data signals for a V.35 interface from

±5V supplies. Combined with an LT

1134A

RS232 transceiver for the control signals and

the proper termination resistor network, the

LTC1346A forms a complete low power

DTE or DCE V.35 interface port. Figure 1

shows the LTC1346A used to provide clock

and data signals to another LTC1346A pe-

ripheral port. The BI Technologies chip

shown is a surface mount V.35 termination

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24

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

VEE

VCC

GND

T1

T2

T3

S1

S2

R3

R2

R1

S0



Y1

Z1

Y2

Z2

Y3

Z3

A3

B3

A2

B2

A1

SW PACKAGE

24-LEAD PLASTIC SO

LTC1346AIS

Half-Bridge N-Channel

Power MOSFET Driver

IC for Power Supply and

Motor Control

Applications

The LT1336 is a cost effective half-

bridge N-channel power MOSFET driver

that can drive a topside N-channel power

MOSFET operating with a high voltage

CC1



0.1µF

LTC1346A LTC1346ABI

627T500/1250 BI

627T500/1250

BI TECHNOLOGIES

627T500/1250 (SO)

CC2



0.1µF

TXD (103)

SCTE (113)

TXC (114)

RXC (115)

RXD (104)

GND (102)

DX RX

T T

CC2

CC1

T T

LTC1346 • TA01

50Ω

=125Ω

50Ω

EE2



–5V

0.1µF

EE1



–5V

0.1µF

Figure 1. V.35 Clock and Data Signals Are Supplied by a Single LTC1346A IC

Linear Technology Chronicle •

January 1996

ure 1 shows the LT1336 providing unidirec-

tional motor control.

During low supply or start-up condi-

tions, the undervoltage lockout actively pulls

the driver outputs low to prevent the power

MOSFETs from being partially turned on.

The 0.5V hysteresis allows reliable operation

even with slowly varying supplies.

The LT1336 is an ideal driver for

PWM of high current loads, half-bridge and

full-bridge motor control, synchronous

step-down switching regulators, 3-phase

brushless motor drives, high current trans-

ducer amplifiers and Class D power

amplifiers.

The LT1336 is available in 16-lead

plastic dual-in-line and surface mount pack-

ages specified for operation from 0°C to

70°C. Industrial grade versions are also

available specified for operation from –40°C

to 85°C. Please contact your local Linear

Technology sales office for a data sheet and

free evaluation samples of the LT1336.

(HV) rail of up to 60V (absolute maximum).

In PWM operation, an on-chip switching

regulator maintains charge in the bootstrap

capacitor even when approaching and oper-

ating at 100% duty cycle.

The LT1336 has unique adaptive pro-

tection circuitry that prevents shoot thorough

current, eliminating all matching require-

ments for the two MOSFETs. This greatly

eases the design of high efficiency motor

control and switching regulator systems. Fig-

LT1336 from page 1

Figure 1. LT1336 Provides Half-Bridge Motor Drive Control with 40V Capability

Figure 2. LT1336 Is Available in the

16-Lead Surface Mount Package Specified

for Industrial Temperature Range

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

TOP VIEW

16

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12

11

10

9



I SENSE



IN TOP

IN BOTTOM

UV OUT

SGND

PGND

B GATE FB

SWITCH

SW GND

BOOST

T GATE DR

T GATE FB

T SOURCE



B GATE DR

S PACKAGE

16-LEAD PLASTIC SO NARROW

LT1336

Single 5V 250kbaud

RS232/RS485

Multiprotocol

Transceiver Is Software

Configurable

The LTC1334 is a low power CMOS

bidirectional transceiver featuring two

reconfigurable interface ports. It can be con-

figured as two RS485 differential ports, as

two dual RS232 single-ended ports or as one

RS485 differential port and one dual RS232

single-ended port. An onboard charge pump

requires four 0.1µF capacitors to generate

boosted positive and negative supplies, al-

lowing the RS232 drivers to meet the RS232

±5V output swing requirement with only a

single 5V supply. Supply current is typically

8mA and a shutdown mode reduces the sup-

ply current to 10µA. Figure 1 shows a

typical multimode RS232/RS485 port-to-

port connection using LTC1334.

The RS232 transceivers typically oper-

ate to 250kBd and are in full compliance

with RS232 specifications. All interface

drivers feature short-circuit and thermal

shutdown protection. An Enable pin allows

RS485 driver outputs to be forced into high

impedance, which is maintained even when

the outputs are forced beyond the supply rail

or power is off. Both driver outputs and re-

ceiver inputs feature ±10kV ESD protection.

A loopback mode allows the driver outputs

to be connected back to the receiver inputs

for diagnostic self-test. Figure 2 shows vari-

ous configuration schemes possible with the

LTC1334 that enable the loopback feature.

The LTC1334 is an ideal interface de-

vice for use in software selectable RS485/

RS422/RS232/EIA562 port applications or

where multiple protocols need to be imple-

mented simultaneously.

Continued on page 4

5V 85V

5V 20 0V

32728

CC1

5V 120Ω

LTC1334

LTC1334 • TA01

RX OUT

RS485 INTERFACE

DR ENABLE

DR IN 22

LTC1334

RX OUT

DR ENABLE

DR IN

120Ω

4000-FT 24-GAUGE TWISTED PAIR

DR IN 19 424 RX OUT

RX OUT 7DR IN

RS232 INTERFACE

ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE

DR IN 18 525 RX OUT

RX OUT 6DR IN

12 212827

CC2

Figure 1. Typical LTC1334 Interface Connection Diagram



UV OUT

IN TOP

IN BOTTOM

16

14

13

12

11

9

2

10



5

3

SWITCH

BOOST

T GATE DR

T GATE FB

T SOURCE

B GATE DR

B GATE FB



LT1336

I SENSE

1N4148

100µH*

HV = 40V MAX**

BOOST



1µF

10µF

25V

12V

PWM

0Hz TO 100kHz

1336 TA01

IRFZ44

6157

1000µF

100V

SGND PGNDSW GND

1N4148

SENSE



1Ω

1/4W

IN TOP IN BOTTOM T GATE DR B GATE DR

L L L L

LHLH

HLHL

H H L L 



 *DALE 100MB-P

 **FOR HV > 40V SEE “DERIVING THE FLOATING

 SUPPLY WITH THE FLYBACK TOPOLOGY” IN

 APPLICATIONS INFORMATION SECTION OF 

THE DATA SHEET

Linear Technology Chronicle •

January 1996

Application of the Month

LTC1430 Provides Efficient GTL Supply

LOAD CURRENT (A)

EFFICIENCY (%)

di1430_2.eps

0123 654

Figure 2. Efficiency Plot of the

GTL Supply

INDUCTOR

CURRENT

5A/DIV

OUTPUT

VOLTAGE

100mV/DIV

A recent trend in computer bus archi-

tecture is the move toward GTL (Gunning

Transition Logic) for routing high speed

signals between the CPU and chipset

logic. Buses with speeds in excess of

66MHz are using this technology. Several

different GTL supply voltage standards

seem to be evolving, with voltages from

1.2V to 1.5V being discussed most often.

In some implementations of the logic fam-

ily, the GTL supply must both source and

sink currents of 5A to 10A. This causes a

great deal of difficulty for a typical cur-

rent mode control power supply design

that is incapable of controlling negative

load currents. The LTC1430 is a voltage

mode controller, and as such, does not ex-

hibit any problems with negative load cur-

rents.

Most GTL solutions, however, appear

not to require current sinking supplies and

the LTC1430 is well suited for these appli-

cations as well. The circuit shown in Figure

1 switches at 300kHz, regulating a 5V input

down to a 1.5V output while maintaining

good efficiency (see Figure 2). Figure 3

shows the effects of a fast 4A load transient

on the 1.5V output. The initial current was

1A and the final current 5A. The top trace is

the output voltage (100mV/Div) and the

bottom trace is the regulator’s inductor cur-

rent (5A/Div). In Figure 4, the load resistor

is switched from ground to a 3V supply, re-

sulting in bidirectional loading. Current is

switched from 5A to –4A. Again, the top

trace is the output of the 1.5V supply. The

relatively long recovery period is actually

a response to the pertubation that appears

on the input voltage as a result of the large

load change. Voltage mode control suffers

from inherently poor line rejection. In this

case, the lab supply used for the tests ex-

hibits rather poor dynamics. If a better

input supply is used, the overall settling

time will be much faster. The LTC1430

also has a very accurate reference and ex-

hibits good static load regulation, as can

be seen from the very small offset be-

tween the settled light load and heavy load

conditions on the output voltage trace.

L1

2.7µH

MAX

SHDN

COMP

SGND

FSET

CC2

PGND

–SENSE

+SENSE

CC1

U1

LTC1430

R6

10k

R2, 3Ω

R1

R3

3Ω

R4

R5

16.5k

R9

88.7k

R7

15k

R10

3.3k R8

130k

C7

0.1µF

C8

22µF

35V

C12

330

6.3V

OS-CON

C13

330

6.3V

OS-CON

C4

330

6.3V

OS-CON

1.5V OUT

C5

330

6.3V

OS-CON

S/D

C6

0.01µF

C16

0.1µF

C2

680pF

C10

1µF

C9

1µF, 25V

C11

0.068µF

C3

220pF

C1

0.1µFQ1

Si4410

Q2

Si4410

D1

MBRS330T3

di1430_1.eps

330

6.3V

TANT

330

6.3V

TANT

ADDITIONAL

DECOUPLING

AT THE LOAD

+ +

MBR0530T1

Figure 1. Schematic Diagram of GTL Supply

Figure 3. Oscillograph Showing Effects of

4A Load Step on the 1.5V Output Figure 4. Oscillograph Showing Effects

of Bidirectional Loading on the

GTL Supply

1ms/DIV

OUTPUT

VOLTAGE

100mV/DIV

INDUCTOR

CURRENT

5A/DIV

1ms/DIV

Linear Technology Chronicle •

January 1996

Linear Technology Corporation • 1630 McCarthy Blvd. • Milpitas, California 95035-7417 • (408) 432-1900 • FAX: (408) 434-0507 • 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

LTC1334 from page 2

control signal applications. The LTC1334 is

available in 28-lead plastic dual-in-line and

28-lead surface mount packages, specified

for operation from 0°C to 70°C. Contact

Applications for the LTC1334 include

cable repeaters, level translators and CSU/

DSU interface ports in telecommunications

your local Linear Technology Corporation

sales office for a data sheet and evaluation

samples of the LTC1334.

PORT 1 = RS232 MODE

PORT 2 = RS232 MODE

C2C1

SEL1 = 0V

281

SEL2 = 0V 10

GND

LTC1334 • BD02

PORT 1 = RS485 MODE

PORT 2 = RS232 MODE

C2C1

DE1

SEL1 = 5V

281

SEL2 = 0V 10

GND

PORT 1 = RS232 MODE

PORT 2 = RS485 MODE

C2C1

SEL1 = 0V

281

DE2

SEL2 = 5V 10

GND

PORT 1 = RS485 MODE

PORT 2 = RS485 MODE

C2C1

DE1

SEL1 = 5V

281

DE2

SEL2 = 5V 10

GND

LBLBLBLB

Figure 2. LTC1334 Configurations Using Loopback Self Diagnostics Hookup

OUTPUT DRIFT (ppm/°C)

–3

UNITS (%)

–2 –1 0 1

LT1236 TA02

DISTRIBUTION 

OF THREE RUNS

Figure 1. LT1236 Output

Temperature Drift

5ppm/

C, 0.05%

Accurate, Industrial

Grade Voltage

Reference in 8-Lead

Surface Mount Package

The LT1236 is an industrial grade pre-

cision voltage reference in an 8-lead surface

mount package. This new reference com-

bines a tight 0.05% maximum initial

accuracy with a low 5ppm/°C maximum

drift. The drift is guaranteed by measuring

the slope of the output voltage vs tempera-

ture. Most references are specified using the

“box” method, often resulting in a two or

more times worse incremental slope. The

LT1236 5ppm°C is a worst-case specifica-

tion over the full temperature range. The

reference has a typical 0.1Hz to 10Hz noise

level of 3µVP-P and is 100% production

tested for a maximum 10Hz to 1kHz noise

level of only 3.5µVP-P.

The LT1236 is available in both the

8-lead dual-in-line and 8-lead surface mount

packages in three performance grades. De-

vices are provided with 5V and 10V output

voltages for both the commercial and indus-

trial temperature ranges. The output of the

LT1236 sinks and sources 10mA and is al-

most totally immune to input voltage

variations.

As was the case with previous high

performance voltage references, no on-chip

heater is necessary to reach such accurate

performance levels when using the LT1236.

The LT1236 references are based on a bur-

ied Zener diode structure which eliminates

noise and stability problems associated with

surface breakdown devices. Further, a sub-

surface Zener exhibits better temperature

drift and time stability than even the best

bandgap references. Figure 1 shows the

typical distribution of temperature drift with

various production runs of the LT1236

devices.

The LT1236 can be used in series or

shunt mode. The 10V version can be used as

a shunt regulator (2-terminal Zener) with the

same precision characteristics as the 3-termi-

nal connection. Special care has been taken

to minimize thermal regulation effects and

temperature induced hysteresis.

The low power, high accuracy LT1236

is ideal for use in process control, data ac-

quisition and remote sensing applications.

The LT1236-5 and LT1236-10 come in three

performance grades; A, B and C. All ver-

sions are available specified for operation

over the 0°C to 70°C (C) range and –40°C

to 85°C (I) range in the 8-lead dual-in-line

(N8) package as well as the 8-lead surface

mount (S8) package. Contact your local Lin-

ear Technology Corporation sales office for

a data sheet and free evaluation samples of

the LT1236.