LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products December 2000 Product of the Month High Performance Op Amps in SOT-23--LT1797, LT1812, LT1393 Linear Technology has made several additions to its family of high performance op amps in the tiny SOT-23 package. The LT(R)1797 is a 10MHz, rail-to-rail input and output op amp. This unity-gain stable op amp brings precision and bandwidth to the SOT-23 package. It operates on single and split supplies with a total supply voltage of 2.7V to 12V. It is fully specified for operation at 3V/5V single supply as well as 5V dual supplies. This wide operating supply range offers flexibility in a multitude of applications. The rail-to-rail input and output maximize dynamic range, an especially important feature in low voltage applications. DC precision has not been neglected. The LT1797 offers a maximum offset voltage of 1.5mV. The LT1797 is available in both commercial and fully specified industrial temperature grades. Competing "guaranteed by design" SOT-23 op amps are only tested at room temperature and use statistical correlation to predict temperature performance. The LT1797 is tested and performance is guaranteed over the entire - 40C to 85C industrial temperature range. Previously only available in SO-8 but now introduced in SOT-23, the LT1812 is designed for high speed (100MHz GBW), low noise (8nV/Hz ) applications where low power consumption (3.6mA maximum supply current) is at a premium. DC performance has not been neglected with a 1.5mV maximum offset voltage. The LT1812 is offered in I grade, guaranteed and tested over the entire - 40C to 85C industrial temperature range. For higher speed applications, Linear Technology now offers the LT1395 in SOT-23. Perfect for video applications, the LT1395 offers 400MHz bandwidth, 800V/s slew rate and a maximum supply current of 6.5mA. The 80mA output current drive makes the part suitable for use as a line or cable driver. The LT1395 runs on supplies as low as 2V to 6V or 4V to 12V single supply. Table 1 offers a summary of these additions to Linear Technology's family of high performance SOT-23 op amps. Vol. 9 No. 12 Differential 24-Bit ADC Offers Simultaneous 50Hz and 60Hz Rejection--LTC2413 The LTC(R)2413 is an accurate, simple, and small 24-bit No Latency analogto-digital converter (ADC) that offers differential inputs and simultaneous 50Hz and 60Hz rejection. This device enables direct digitization of inputs in applications such as weigh scales, temperature measurements, gas analyzers and strain gauge transducers with no microprocessor calibration and no external components. With simultaneous 50Hz and 60Hz rejection, the LTC2413 rejects line noise to better than 87dB anywhere in the world regardless of the country's line frequency standards. The LTC2413 includes all the outstanding features of Linear Technology's family of No Latency analog-to-digital converters (see Table 1), eliminating configuration and calibration registers, external components and special filtering that other high resolution ADCs require. Its high accuracy differential nonlinearity (DNL) guarantees true 24-bit performance with no missing Continued on page 3 + R1 2 Table 1. High Performance Op Amps in SOT-23 Part LT1797 LT1812 LT1395 GBW 10MHz 100MHz 400MHz SR 2.25V/s 750V/s 800V/s VOS 1.5mV 1.5mV 10mV ISUPPLY 1.5mA 3.6mA 6.5mA VSUPPLY 2.7V to 12.6V 4V to 12V 4V to 12V Output R-to-R In/Out Temp C, I C, I C Package SOT-23 350 BRIDGE SOT-23, SO-8 SOT-23, SO-8 LT1019 VREF 3 REF + SDO 4 REF - SCK 5 IN + CS 12 13 11 LTC2413 6 IN - GND R2 FO 14 1, 7, 8, 9, 10, 15, 16 2413 F42 Inside This Issue: Four Tiny New Inductorless DC/DC Converters: High Frequency, Very Low Noise and Load Disconnect in Shutdown--LTC1751, LTC1754, LTC3200, LTC1928-5 ................................. 2 Hot SwapTM Control of Power "Brick" Module with EM Filtering--LT1640 .............................. 3 Eliminate Two Step-Down DC/DC Converters with 550kHz Dual Controller--LTC1874 ........ 3 Linear Technology Chronicle * December 2000 R1 AND R2 CAN BE USED TO INCREASE TOLERABLE AC COMPONENT ON REF SIGNALS Figure 1. Simple Bridge Connection , LTC and LT are registered trademarks of Linear Technology Corporation. No Latency , Hot Swap and Burst Mode are trademarks of Linear Technology Corporation. 1 Four Tiny New Inductorless DC/DC Converters: High Frequency, Very Low Noise and Load Disconnect in Shutdown--LTC1751, LTC1754, LTC3200, LTC1928-5 Four new DC/DC converters with unique features are optimized for very small space in portable products (see Table 1). Three are micropower, drawing under 200A of supply current. Two have soft-start for controlled power up. One has very high constant frequency for low interference in RF sensitive products. One includes a linear regulator for low noise and improved regulation. All four require no inductors and only three or four tiny ceramic chip capacitors. All four work from single-cell Li-Ion batteries with inputs as wide as 2V to 5.5V. All switch at high frequencies from 550kHz to 2MHz, for small size and low ripple. In shutdown mode, VIN is disconnected from the output to eliminate battery drain and VOUT is automatically grounded for fault-free operation in all versions. All versions offer short-circuit and thermal protection. LTC1754 and LTC1751: Micropower, SOT-23 and MSOP, 50mA and 100mA The LTC1754 is a micropower charge pump in a 6-lead SOT-23 package that produces up to 50mA of output current. It draws just 13A of quiescent current, 1A in shutdown mode, prolonging battery life. The LTC1754-5 requires only a 1F flying capacitor, a small 10F bypass capacitor at VIN and another at VOUT to form a complete boost converter circuit that fits into a PC board space of just 0.05 square inches. The LTC1754 meets the power source requirements for cellular phones, bar code readers, handheld computers and portable instruments (Figure 1). It comes in 3.3V or 5V output versions. The LTC1751 is a micropower charge pump in the low height (1.1mm max) 8-lead MSOP package that produces up to 100mA of output current. This device plus three small capacitors form a complete boost converter circuit that fits into a board space of 0.06 square inches (39mm2). The LTC1751 includes an internal doubler charge pump that boosts a 2V to 5.5V input to an adjustable 2.5V to 5.25V output. Its low operating current (20A) and shutdown current (0.01A typically) extend battery operating time. The LTC1751 is also available in fixed 3.3V and 5V output versions (Figure 2). The power good pin (PGOOD) on the fixed output versions indicates when the output voltage has reached its final value or if the output has an undervoltage fault condition. The built-in soft-start feature is optional and adjustable. LTC3200: New Architecture for Constant Frequency, SOT-23 and MSOP, 100mA A new design allows the LTC3200 to maintain constant frequency switching down to zero load current. The result is reduced output and input ripple. This voltage doubler produces a regulated output voltage with up to 100mA of current from a 2.7V to 4.5V input. A variable output version in MSOP and a fixed 5V output version in SOT-23 are available. The tiny package plus just three tiny capacitors make the LTC3200 ideally suited for small battery-powered products where low noise is important. Built-in softstart circuitry prevents excessive inrush current during start-up. Its shutdown feature reduces quiescent current to under 1A. The LTC3200 is perfect for LED backlight supplies for color LCD displays (Figure 3) and VIN 2.7V TO 5.5V 3 C2 10F ON OFF CSS 4.7nF 3 2 7 1 SHDN PGOOD LTC1751-5 8 6 SS C+ 4 C- GND R1 100k PGOOD VOUT 5V 4% C1 I 100mA, VIN 3V 10F OUT IOUT 50mA, VIN 2.7V CFLY 1F 5 1751 TA01 Figure 2. Regulated 5V Output from 2.7V to 5.5V 1F 1 6 5 USB 10F PORT VOUT VIN 1F 4 for local 3V to 5V conversion such as required for PCMCIA systems. LTC1928-5: Micropower, SOT-23, 30mA, Internal Linear Regulator The LTC1928-5 takes the standard doubler architecture and adds an internal low dropout voltage linear regulator to reduce ripple and improve regulation. Competing solutions require two ICs. The LTC1928-5 has an output voltage ripple of 90VRMS (100kHz bandwidth) while delivering up to 30mA of output current. It draws just 190A of operating current (4A in shutdown) which makes it ideal as a VCO power supply in cellular phones where it is very important to minimize output noise while prolonging battery life. The LTC1928-5 converts a 2.7V to 4.4V input supply to produce a fixed 5V output and requires only four external capacitors resulting in a circuit footprint of just 34mm2 (< 0.045in2). The 550kHz switching frequency operation permits the use of small ceramic capacitors to save board space. Due to the internal current limiting, the output current VOUT can be shorted to ground indefinitely. The LTC1928-5 is offered in a 6-lead SOT-23 package and is specified over a - 40C to 85C operating temperature range. Also shown in Table 1 is the similar LTC1682. This MSOP package device provides up to 80mA of output current and comes in adjustable, 3.3V and 5V output versions. 1 LTC1754-5 2 VOUT 10F 5V 4% 50mA 3V TO 4.4V Li-Ion BATTERY 1F 1754 TA06 Figure 1. USB Port to Regulated 5V Power Supply VIN 3 C- VOUT 6 (APPLY PWM WAVEFORM FOR ADJUSTABLE BRIGHTNESS CONTROL) SGND SHDN UP TO 6 LEDS 8 1F LTC3200 FB ON OFF 2 C+ PGND 7 5 82 82 82 82 82 82 4 32005 TA04 VSHDN t Figure 3. White or Blue LED Driver with LED Current Control 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. 2 Linear Technology Chronicle * December 2000 Application of the Month Hot Swap Control of a Power "Brick" Module with EMI Filtering--LT1640 The LT1640 is a negative voltage Hot Swap controller that allows a board to be safely inserted and removed from a live backplane. Inrush current is limited to a programmable value by controlling the gate voltage of an external N-channel pass transistor. The pass transistor is turned off if the input voltage is less than the undervoltage threshold (programmable) or greater than the overvoltage threshold. A programmable electronic circuit breaker protects the system against shorts. The LT1640 works directly with voltages ranging from -10V to - 80V and has proven popular in - 48V telecom systems. GND It provides a power good output that can directly enable a power module when the input voltage to the module is within tolerance, without floating supplies or level shifting. The LT1640L version is designed for modules with an active-low enable and the LT1640H for modules with an active-high enable. Many applications place an EMI filter module in the power path to prevent switching noise of the module from being injected back onto the power supply. A typical application using the Lucent FLTR100V10 filter module is shown in Figure 1. When using a filter, an optoisolator is required to prevent 1kV common mode transients--standard fare for telecom equipment--from destroying the PWRGD and ON/OFF pins. For positive 48V inputs, the LTC1641 provides a similar capability. Each of these controllers is available in an 8-pin SO package. The power brick module may be replaced with a design based upon the LT1339, LT1247 or LT1425 switching regulator controllers. (See InfoCards 23 and 25.) (SHORT PIN) LUCENT JW050A1-E GND OPTOISOLATOR R4 562k 1% R5 9.09k 1% 8 PWRGD VDD 3 DRAIN UV 7 LT1640L 2 R6 10k 1% OV GATE VEE 6 1N4148 VIN+ C2 3.3nF 100V R3 18k 5% SENSE 4 3 1 C3 0.1F 100V VIN- 2 VOUT+ LUCENT FLTR100V10 C4 0.1F 100V + C6 0.1F 100V C5 100F 100V VOUT- CASE R2 10 5% C1 150nF 25V 5 R1 0.02 5% * - 48V 1 1 VIN+ VOUT+ SENSE + TRIM ON/OFF 9 7 6 4 SENSE - VOUT- VIN- 5V 8 + C7 100F 16V 5 CASE 3 1640 F14 4 2 Q1 IRF530 * DIODES INC. SMAT70A Figure 1. Hot Swap Application Using a Filter Module LTC2413 from page 1 codes and its integral nonlinearity (INL) is only 2ppm. The No Latency architecture ensures single cycle settling time, simplifying multiplexed applications and eliminating software overhead. A full-scale error of just 2.5ppm and 800nVRMS noise Table 1. No Latency Analog-to-Digital Converters 1-Channel 800nV Noise 24 Bits LTC2410* LTC2413* 1.5V Noise 24 Bits LTC2400 LTC2411* 3V Noise 24 Bits LTC2401 6V Noise 20 Bits LTC2420 2-Channel 4-Channel 8-Channel LTC2404 LTC2408 LTC2424 LTC2428 LTC2402 allow direct connection to sensors and bridges without the use of a PGA. The LTC2413's differential inputs allow direct connection to bridges without external circuitry (Figure 1). The LTC2413 also offers differential reference inputs, which can range from 0.1V up to VCC for ratiometric and remote sensing applications. The input voltage range is - 0.5VREF to 0.5VREF. The LTC2413 operates on supply voltages from 2.7V to 5.5V, consuming just 200A during conversion and 20A during shutdown. The LTC2413 is available in the space saving 16-pin SSOP package in the commercial and industrial temperature ranges. *Differential Inputs 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. Linear Technology Chronicle * December 2000 3 LTC1751, LTC1754, LTC3200, LTC1928-5 from page 2 Table 1. New Inductorless DC/DC Voltage Converters Are Optimized by Application Parameters* LTC1751 Architecture Advantages Additional Features Input Voltage Output Voltages Regulation LTC1754 Gated Oscillator with Burst Mode Highest Efficiency, Moderate Noise, Lowest IQ LTC3200 LTC1928-5 LTC1682 Constant Frequency Open Loop Charge Pump with LDO Post Regulator Low Noise, Lowest RFI Lowest Noise, Low IQ, Best Regulation Stable with 2F Capacitor On the Output Power Good, UVLO, Soft-Start Tiniest Auto Soft-Start, Tiniest 2V to 5.5V 2V to 4.4V 2.7V to 4.5V 2.7V to 4.4V 1.8V to 4.4V 3.3V, 5V, 2.5V ~ 5.25V 3.3V, 5V 5V, 3V ~ 5.5V 5V 3.3V, 5V, 2.5V ~ 5.5V 4% 4% 4% 2% 2% Output Current 100mA 50mA 100mA 30mA 80mA Switching Frequency 800kHz 600kHz 2MHz 550kHz 550kHz Typical Efficiency** 83% 83% 79% 79% 78% 68mVP-P 65mVP-P -- 800VP-P 500VP-P -- -- 3 to 33mVP-P 90VRMS 60VRMS 20A 13A 4mA 190A 150A VOUT Ripple (2.5MHz BW) Narrow Band Ripple (100kHz) Typical Quiescent Current Typical Shutdown Packages <2A <1A <1A 4A 1A MSOP-8 SOT-23 SOT-23 MSOP-8 SOT-23 MSOP-8 SO-8 * Maximum/minimum values unless stated as typical. ** 3V input to 5V output, for comparison. See data sheets. Eliminate Two StepDown DC/DC Converters with 550kHz Dual Controller--LTC1874 The LTC1874 is a dual output current mode step-down DC/DC converter that includes two 550kHz controllers in a small, thin 16-lead SSOP. This IC replaces two DC/DC converters and allows the use of small inductors and capacitors. The input voltage range for each controller is 2.5V to 10V with output adjustable to as low as 0.8V. Each controller consumes only 270A but can deliver up to 5A of load current. The IC's compact dual output voltage design is ideal in powering ASICs, microcontrollers, memory modules and DSPs in applications ranging from telecom to portable devices. The LTC1874 drives external P-channel MOSFETs and uses sense resistors to accurately deliver power to the load at up to 94% efficiency. Furthermore, the use of P-channel MOSFETS maximizes the life of a battery source by allowing very low dropout operation. Each controller has a separate shutdown pin allowing full control of each output voltage. Linear Technology Products Are Distributed By: Arrow Electronics Arrow/Zeus Components Digi-Key Gerber Electronics Avnet Wyle Electronics (c) 2000 Linear Technology Corporation/Printed in USA 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. * www.linear-tech.com * For Literature 1-800-4-LINEAR 4Linear Technology Corporation * 1630 McCarthy Blvd. * Milpitas, CA 95035-7417 * (408) 432-1900 * FAX: (408) 434-0507 Linear Technology Chronicle * Only: December 2000