August 2000 - Linear Technology - searchdatasheet.com

Linear Technology Chronicle

• August 2000 1

A Showcase of Linear Technology’s Focus Products

Product of the Month

, LTC and LT are registered trademarks of Linear Technology

Corporation. No Latency Delta-Sigma, Burst Mode and

OPTI-LOOP are trademarks of Linear Technology Corporation.

C is a trademark of Philips Electronics N.V.

Linear Technology Chronicle

August 2000 Vol. 9 No. 8

Inside This Issue:

Smallest RF Power Controller for Single and Dual Band GSM/PCS

Phones Minimizes Test Time–LTC1757A................................................................................ 2

Single Cell Li-Ion to 3.3V Converter is Tiny and Draws Very Low Power—LT1615 ................ 3

Parallel 16-Bit Rail-to-Rail Output DAC Gives 16-Bit Monotonicity

On a Single 3V Supply—LTC1657L ....................................................................................... 3

Smallest and Most Efficient High Current Synchronous Regulators

for Processors, ASICs and FPGAs ......................................................................................... 4

Figure 1. LTC2410 Directly Digitizes Differential Bridge Output

24-Bit, No Latency Delta-Sigma

ADC with Differ-

ential Inputs and Differential Reference—LTC2410

Continued on page 2

The LTC

2410 is the most accurate,

simplest and smallest 24-bit analog-to-digi-

tal converter with differential inputs on the

market today. This device operates on sup-

plies from 2.7V to 5.5V and can accept any

differential reference voltage from 0.1V to

, providing flexibility in ratiometric and

remote sensing applications. It consumes

just 200µA during conversion and 20µA

during shutdown. The LTC2410’s 16-pin

SSOP package is the same size as an SO-8

and is smaller than any other high resolution

ADC with differential inputs. The

LTC2410’s accuracy, features and small

size mean ease-of-use and ease-of-design in

applications such as weigh scales, tempera-

ture measurements, gas analyzers, strain

gauge transducers and other applications

that demand precise measurement.

The LTC2410 automatically performs

transparent offset and full-scale calibration

on every conversion to provide 5ppm total

unadjusted error, 0.5µV offset error and

2.5ppm full-scale error with unmeasurable

drifts (only 0.001ppm/°C). Its high accu-

racy DNL guarantees true 24-bit output

with no missing codes and its integral non-

linearity (INL) is only 2ppm (2.5V refer-

ence). The output noise of the LTC2410 is

only 800nV with a wide 5V input range,

eliminating the need for PGAs. The

LTC2410 has a proprietary no latency ar-

chitecture that allows single cycle settling

for multiplexed applications. Single cycle

settling and transparent calibration simplify

system design by reducing software over-

head. The performance of the LTC2410

provides the highest level of accuracy for

the most demanding “bridge to bits” appli-

cations (see Figure 1).

The LTC2410 includes a highly accu-

rate on-chip oscillator, eliminating the need

for external frequency setting components

such as crystals or oscillators. Pin selectable

50Hz/60Hz notch frequency of the 4th order

sync filter allows 120dB rejection of line

frequencies ±2% with the on-chip oscillator.

The common mode rejection ratio (CMRR)

of its differential input at 60Hz is an impres-

sive 140dB. When clocked externally, the

LTC2410 allows output word rates up to

15Hz. Faster rates are possible at reduced

resolution. This device eliminates configura-

tion and calibration registers, external com-

ponents and special filtering that other high

resolution ADCs require.

The LTC2410 is available in both

commercial and industrial temperature

ranges in the space saving 16-pin SSOP

package.

LTC2410

REF

–

GND F

–

1µF

SDO

3-WIRE

SPI INTERFACE

SCK

2410 TA02

1, 7, 8

9, 10,

15, 16

BRIDGE

IMPEDANCE

100Ω TO10k

0.05%, 10ppm/

SOT-23 Series Reference

Features 0.1V Dropout

and 35

A Supply Current

—LT1790

Despite its tiny SOT-23 package, the

1790 provides very high precision and

low noise (Table 1). Small size and precision

plus the 35µA supply current and low drop-

out voltage make the LT1790 ideal for use in

battery pack and battery-powered portable

products.

The LT1790 generates noise of only

12µVP-P (0.1Hz to10Hz), the lowest of any

SOT-23 low dropout voltage reference. Low

noise benefits noise-sensitive products such

as precision handheld instruments and base

stations for wireless communications.

Linear Technology Chronicle

• August 2000

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.

LT1790 from page 1

With the wide –40°C to 125°C operat-

ing temperature range and low thermally

induced hysteresis, the LT1790 is the first

SOT-23 reference suitable for use in harsh

environments such as automotive and indus-

trial systems. The lower thermal resistance

of the 6-pin package provides a greater ther-

mal margin than 3-lead SOT-23 packages in

high ambient temperature conditions.

The long-term drift of 50ppm/

ensures accuracy for remote sensing and

for applications where recalibration is either

impossible or costly. The input voltage

range of 2.6V to 20V allows the device to

be directly powered by a variety of supplies

from a lithium-ion battery to a low cost wall

adapter. The part has the guaranteed ability

to both sink and source ±5mA. It may be

used as a precision voltage regulator and

is easily configured as a negative voltage

reference.

The LT1790 is also the most affordable

precision SOT-23 reference in either of its

two performance grades: LT1790A (0.05%,

10ppm/°C maximum) and LT1790B (0.1%,

25ppm/°C maximum). The 2.5V output ver-

sion is available now. Additional versions,

including 1.25V, 2.048V, 3V, 3.3V, 4.096V

and 5V will be available soon. They are pin

compatible with other series references in 3-

lead and 5-lead SOT-23 packages.

Table 1. Micropower Low Dropout Reference Has High Precision

LT1790ACS6-2.5 LT1790BCS6-2.5

Output Voltage 2.5V 2.5V

Initial Accuracy 0.05% Max 0.1% Max

Temperature Coefficient 10ppm/°C Max 25ppm/°C Max

Dropout Voltage 0.1V Max 0.1V Max

Input Voltage Range 2.6V to 18V 2.6V to 18V

Supply Current 60µA Max 60µA Max

Temperature Hysteresis 40ppm 40ppm

Long-Term Drift 50ppm/

√kHr

50ppm/

√kHr

Noise: 0.1Hz to 10Hz 12µV

P-P

12µV

P-P

Noise: 10Hz to 1kHz 33µV

RMS

33µV

RMS

LT1790

0.1µF 1µF

OUT

= 2.5V

2.6V ≤ V

≤ 18V

Figure 1. Series Precision Reference Has

Small Size and Big Performance

√kHr

Smallest RF Power

Controller for Single and

Dual Band GSM/PCS

Phones Minimizes Test

Time—LTC1757A

The LTC1757A is the smallest and

most accurate RF power amplifier control-

ler for single and dual band GSM/PCS

cellular phones. The product eliminates op

amps, detector diodes, MUXes (multiplex-

ers) and over ten discrete components,

shrinking the design into a tiny MSOP

package (Figure 1). Excellent temperature

stability minimizes a cell phone’s produc-

tion test time by allowing a single calibra-

tion at room temperature. This device

operates directly from a single-cell Li-Ion

battery and supports a wide range of RF

power amplifiers from various manufactur-

ers. Applications include single and dual

band GSM/GPRS phones, PCS devices and

wireless data modems.

A unique autozero function in the

LTC1757A cancels internal and external

offsets as well as temperature dependent

offsets, enabling accurate low power

programming of the RF power amplifier.

The autozero function provides excellent

temperature stability across a broad range

of output power, an arduous task to achieve

with conventional discrete approaches.

High loop gain lets the device control a

variety of power amplifiers and deliver out-

put power that is independent of the PA’s

characteristics. Built-in circuitry protects

both the IC and the power amplifier against

overcurrent and overvoltage conditions. Its

operating voltage of 2.7V to 6V makes it

ideal for use with single cell Li-Ion or

3- or 4-cell NiMH/NiCd battery-powered

cell phones. Standby current of a mere 1mA

drops to less than 1µA in shutdown to con-

serve battery life.

The LTC1757A measures RF output

power using an internal Schottky diode that

is capable of detecting frequencies in the

range of 850MHz to 2GHz. This detected

voltage is compared to the power control

DAC voltage generated by the baseband

circuitry to set the output power. The

LTC1757A-2 dual band controller is of-

fered in a 10-lead MSOP package with an

integrated multiplexer. The LTC1757A-1,

a single/dual band version, does not

include the MUX and comes in an 8-lead

MSOP.

SHDN

BSEL

GND

PCA

PCB

TXEN

PCTL

LTC1757A-2

Li-Ion

SHDN

BSEL TXEN 900MHz

DAC

RF PA

DIRECTIONAL

COUPLER DIPLEXER

1.8GHz/1.9GHz RF PA

50Ω

1757A TA01

33pF

68Ω

Figure 1. LTC1757A-2: Dual Band Cellular Telephone RF Power Controller

Linear Technology Chronicle

• August 2000 3

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.

Application of the Month

Single Cell Li-Ion to 3.3V Converter is Tiny

and Draws Very Low Power—LT1615

Lithium-ion (Li-Ion) is the battery of

choice for systems needing the most

energy with the lightest weight, but with a

cell voltage ranging from 4.2V down to

2.5V, a simple boost topology cannot be

used to provide a 3.3V output. The circuit

in Figure 1 is a SEPIC converter that can

easily do the job, providing 50mA of load

current. The circuit shown uses two sepa-

rate inductors, but a single, dual-winding

inductor (a 1:1 transformer) can be substi-

tuted. Figure 2 shows the switching wave-

forms for this SEPIC converter with an

input voltage of 2.7V and a 50mA load.

This photo illustrates the Burst Mode

op-

eration of the LT1615. The device is in

standby, drawing only 20µA quiescent cur-

rent, between bursts. For the SEPIC, the

switch current is split equally between the

two inductors, with both inductors provid-

ing current to the load when the switch is

turned off. Typical efficiency for this con-

verter is 70%.

With a resistor value change, the cir-

cuit will convert a 4-cell (3V to 6V) input

to a 5V output (see data sheet).

The LT1615 is designed for portable

electronics that need a minimum footprint

and a long battery life. It uses a current

limited, fixed off-time control scheme

which helps achieve high efficiency opera-

tion over a wide range of load currents.

Shutdown quiescent current is 0.5µA. The

LT1615 uses tiny, low profile inductors

and capacitors.

The LT1615 is pin compatible with

the LT1613 current mode, constant fre-

quency device that is capable of producing

larger output currents than the LT1615 at

the expense of higher quiescent current.

Negative output versions include the

LT1617 and LT1611.

VIN SW

LT1615

VIN

2.5V TO

4.2V

10µHD1

1µF

SHDN

604k

1M C2

10µF

VOUT

3.3V

50mA

1615 TA07

GND

4.7µF

C1: TAIYO YUDEN LMK316BJ475 (408) 573-4150

C2: TAIYO YUDEN JMK316BJ106 (408) 573-4150

C3: TAIYO YUDEN JMK107BJ105 (408) 573-4150

L1, L2: MURATA LQH3C100K24 (814) 237-1431

D1: MOTOROLA MBR0520 (800) 441-2447

10µH

15 4.7pF

Figure 1. Li-Ion to 3.3V SEPIC Converter

OUT

20mV/DIV

AC COUPLED

200mA/DIV

5V/DIV

2µs/DIV

Figure 2. Switching Waveforms of the 3.3V

SEPIC Converter with 50mA Load

Parallel 16-Bit Rail-to-Rail Output DAC Gives 16-Bit

Monotonicity On a Single 3V Supply—LTC1657L

The new LTC1657L is a parallel 16-bit

voltage output DAC designed for 3V single

supply operation. The differential nonlinear-

ity (DNL) of the LTC1657L is only ±1LSB

(maximum), guaranteeing true 16-bit mono-

tonic performance over the entire specified

temperature range (see Figure 1). This DC

performance becomes critical in control-loop

applications. The LTC1657L operates on

supplies from 2.7V to 5.5V and consumes

only 650µA (typical) of operating current.

The LTC1657L offers an internal rail-

to-rail output buffer and 1.25V reference,

minimizing external components. A refer-

ence input pin can be driven by an external

reference if different output voltage ranges

are desired. The full-scale output can be one

CODE

–1.0

–0.2

–0.4

–0.6

–0.8

0.2

0.4

0.6

0.8

1.0

DNL ERROR (LSB)

16484 32768

1657 TA02

49152 65535

Figure 1. Differential Nonlinearity

vs Input Code

or two times the reference voltage depending

on how the X1/X2 pin is connected. This device includes a 16-bit or 2-byte

double-buffered architecture that allows a

simple interface to most microprocessors

and DSPs. This parallel architecture allows

faster digital interface than serial devices

with less software overhead, simplifying

system designs.

The LTC1657L’s narrow 28-pin SSOP

package is the smallest in the industry for

16-bit buffered voltage output DACs and

saves precious board space in portable appli-

cations. The LTC1657L is also available in

the 28-pin PDIP. The part is available in

both commercial and industrial temperature

ranges.

Linear Technology Chronicle

• August 2000

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

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.

Smallest and Most Efficient High Current Synchronous Regulators

for Processors, ASICs and FPGAs

LTC offers the smallest, most efficient

high output current solutions for micropro-

cessors, DSPs, ASICs and FPGAs in applica-

tions such as PCs, workstations, network

routers and telecom switches (Table 1). Many

controllers include the VID function for CPU

core voltage maximization (Figure 1).

Features include:

•All surface mount with no heat sinks

•Outputs operate 180° out of phase to

reduce input ripple current, input capaci-

tance and EMI

•Unique OPTI-LOOP

compensation

allows fewer output capacitors

•Soft-latch overvoltage function saves

components and eliminates nuisance

power supply trips

•300kHz to 550kHz fixed frequency opera-

tion minimizes the inductor size

•Accurate current sharing allows a single

output of up to twelve phases and 200A

under VID control

Table 1. Low Voltage, High Current Synchronous Switching Regulator Controllers

Controller Phases VID Inputs Outputs* Current** Power Good Packages

LT1339 1 – 10V to 60V 1.25V to 5V 50A – 20-Lead SO

LTC1530 1 – 4V to 14V 1.3V to 3.5V 20A – 8-Lead SO

LTC1628 2 – 3.5V to 36V A: 0.8V to 2V B: 0.8V to 5V 25A per Channel Yes 28-Lead SSOP

LTC1629-PG 2 – 4V to 36V 0.8V to 5V 42A Yes 28-Lead SSOP

LTC1649 1 – 2.7V to 6V 1.3V to 2.5V 20A – 16-Lead SO

LTC1702 2 – 3V to 7V A: 0.8V to 2V B: 0.8V to 5V 25A per Channel – 24-Lead Narrow SSOP

LTC1703 2 Mobile 3V to 7V A: 0.8V to 2V B: 0.8V to 5V 25A per Channel – 28-Lead SSOP

LTC1708-PG 2 Mobile 4V to 36V A: 0.8V to 2V B: 0.8V to 5V 25A per Channel Yes 36-Lead SSOP 5.3mm

LTC1709 2 VRM8.4 4V to 36V 1.3V to 3.5V 42A – 36-Lead SSOP 5.3mm

LTC1709-8 2 VRM8.4 4V to 36V 1.3V to 3.5V 42A Yes 36-Lead SSOP 5.3mm

LTC1709-9 2 VRM9.0 4V to 36V 1.3V to 3.5V 42A Yes 36-Lead SSOP 5.3mm

LTC1735-1 1 – 3.5V to 36V 0.8V to 5V 25A Yes 16-Lead Narrow SSOP

LTC1736 1 Mobile 3.5V to 36V 0.8V to 2V 25A Yes 24-Lead SSOP

LTC1753 1 VRM8.4 4.5V to 7V 1.3V to 3.5V 19A – 20-Lead SSOP

LTC1929 2 – 4V to 36V 0.8V to 5V 42A – 28-Lead SSOP

LTC1873 2 VRM8.4 3V to 7V A: 1.3V to 3.5V B: 0.8V to 5V 25A per Channel – 28-Lead SSOP

LTC1628 + 2 VRM8.4 4V to 36V A: 1.3V to 3.5V 25A per Channel Yes 28-Lead SSOP

LTC1706-8X or 9.0 B: 0.8V to 5V (PG Version) 10-Lead MSOP

LTC1709-X + 4 VRM8.4 4V to 36V 1.3V to 3.5V >60A Yes 36-Lead SSOP

LTC1929 or 9.0 28-Lead SSOP

n-LTC1629 + 4 to 12 VRM8.4 4V to 36V 1.3V to 3.5V 200A Yes (n) 28-Lead SSOP

LTC1706-8X (2n) or 9.0 (PG Version) 10-Lead MSOP

*With two outputs, channel A has VID control **Select FETs for the maximum output current required

1709 TA01

TG1

BOOST 1

SW1

BG1

PGND

SENSE1+

SENSE1–

TG2

BOOST2

SW2

BG2

INTVCC

SENSE 2+

SENSE 2–

VIN

RUN/SS

VDIFFOUT

ITH

SENSEIN

FBOUT

EAIN

VID0–VID4

VOS–

VOS+

LTC1709

SGND

0.1µF

1.2nF

5 VID BITS

15k

10µF ×4

35V

COUT

1000µF

×2

VOUT

1.3V TO 3.5V

40A

1µH

0.002Ω

VIN

5V TO 28V

1µH

0.47µF

10µF

Q1–Q4 2× FAIRCHILD FDS7760A OR SILICONIX Si4874

Figure 1. Surface Mount, 40A, 2-Phase Step-Down Converter with VID

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