LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products October 2000 Product of the Month First 1A Switching Regulators in SOT-23 Package Have Low Noise and Switch at 1.2MHz-- LT1930 and LT1931 The LT(R)1930 and LT1931 are the only SOT-23 switching regulators on the market that include an integrated 1A switch. Their high 1.2MHz switching frequency enables the use of small, low cost capacitors and inductors, minimizing the total PCB footprint and maintaining a height profile below 2mm. Their constant high frequency keeps the output noise low and predictable so that output voltage ripple of less than 5mVP-P is easily achievable. With an input voltage range of 2.6V to 16V, the LT1930 and LT1931 are a good fit for a variety of input sources. The onboard switch features a low VCESAT voltage of 400mV at 1A, resulting in very good efficiencies even at high load currents. Their L1 5.6H VIN 5V C1 4.7F SHDN D1 5 1 VIN SW R1 40.2M LT1930 4 SHDN FB VOUT 5V 480mA C2 10F 3 GND 2 C1: TAIYO-YUDEN X5R JMK212BJ475MG C2: TAIYO-YUDEN X5R JMK316BJ106ML D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-SR6 R2 13.3k 1930 TA04 Figure 1. 3.3V to 5V/450mA Step-Up DC/DC Converter 36V switches allow outputs as high as 34V or -34V. The devices are pin compatible with other LTC devices for simple upgrades and design flexibility. An integrated shutdown function limits the supply current to 0.01A (typical) when the part is disabled. Shutdown virtually eliminates battery drain, extending operating time in portable devices. LT1930: 1A Switcher for Boost, SEPIC and Flyback The LT1930 is a 1A boost DC/DC converter in a 5-lead SOT-23 package. It offers the smallest solution size (8mm x 10mm) for generating a 5V (at 400mA) output from a battery voltage as low as 2.6V. The 36V rated switch is useful for boost converters up to 34V, as well as for buck-boost SEPIC (single-ended primary inductance converters) and flyback designs. The LT1930 can generate 480mA at 5V from a 3.3V input (Figure 1) or 300mA at 12V from a 5V input. Small form factor, minimal external parts count and high efficiency make the LT1930 a good choice for conversion needs in modems, xDSL power supplies, PDAs and medical diagnostic equipment. The device is pin-to-pin compatible with the lower power fixed frequency LT1613 and the LT1615 with Burst ModeTM operation. Inside This Issue: 24-Bit No Latency Delta-SigmaTM ADC with Differential Inputs Fits in MSOP Package--LTC2411 ......................................................................................... Amplifier with 42V Common Mode Input Range on a Single 5V Supply Without Sacrificing Differential Gain--LT1884 ........................................................................ Dual and Quad Rail-to-Rail Output, Picoamp Input Precision Op Amps--LT1881/LT1882 ... New LDO Regulators Have Lowest Noise, Withstand Reverse Voltage and Operate with Low Cost Ceramic Capacitors--LT1962/LT1963 ............................................................ Linear Technology Chronicle * October 2000 2 3 3 4 Vol. 9 No. 10 LT1931: Low Noise Inverting 1A Switching Regulator The LT1931 SOT-23 inverting switching regulator has an on-chip 1A switch that allows high output currents. In a typical 5V to - 5V application the part can deliver 350mA. Its low noise architecture makes it perfect for supplying critical negative bias for disk drive MR heads, GaAs FETs, digital camera CCDs and LCDs. The device is pinfor-pin compatible with the lower power constant frequency LT1611 and the LT1617 with Burst Mode operation. Continued on page 4 Low Noise, High Speed Rail-to-Rail Op Amp Operates on Supplies as Low as 2.5V Without Compromising Performance--LT1806 The LT1806 offers a unique combination of low voltage operation, wide bandwidth, low distortion and low noise. The 325MHz unity-gain bandwidth product, low THD of - 80dBc at 5MHz and 3.5nV/ Hz noise ensures high performance at low voltages, perfect for a wide variety of applications such as high speed data acquisition, broadband digital communications and high performance video systems. In addition to the low voltage noise performance, the overall DC precision of this high speed op amp is unmatched by any competitive device. A maximum offset voltage of less than 0.5mV, CMRR of 106dB and a large-signal voltage gain of 300V/mV dispel any concern about DC accuracy at low voltages. The LT1806 also features a shutdown pin that reduces power consumption to less than 2mW on a 3V supply. Continued on page 2 , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode, No Latency Delta-Sigma, No Latency and C-Load are trademarks of Linear Technology Corporation. 1 24-Bit No Latency DeltaSigma ADC with Differential Inputs Fits in MSOP Package-- LTC2411 Packaged in the tiny 10-pin MSOP, the LTC(R)2411 is the smallest 24-bit analog-todigital converter (ADC) with differential inputs and reference available today. The 10-lead MSOP package is less than half the size of an SO-8 and allows the LTC2411 to fit within the shell of a sensor or transducer. Operating from a supply as low as 2.7V, the part consumes just 200A during conversion and 3A during auto shutdown, extending easily be used to upgrade existing sockets moving to lower supply voltages or requiring higher performance. 3V C1 33F R1 5k + As systems migrate to lower supply voltages, dynamic range becomes precious. The LT1806 maintains its performance for supplies from 2.5V to 12V and is fully specified on 3V, 5V and 5V supplies. The LT1806 has an input range that includes both supply rails and an output that swings within 20mV of either supply rail. This combination of low minimum supply voltage and rail-to-rail input and output maximizes the signal dynamic range in low supply voltage applications. The part's high 85mA output current and low distortion also makes it useful as a line driver, cable driver or buffer amplifier. The LT1806 is available in the 8-pin SO package for operation over the industrial and commercial temperature ranges. Available in the standard 8-pin pinout, the LT1806 can VIN RT 75 3 R2 5k C3 1000F 7 + 6 LT1806 2 - 4 R5 75 75 COAX CABLE VOUT + LT1806 from page 1 RLOAD 75 R4 1k R3 1k C2 150F + 1806 TA01 Figure 1. LT1806 3V Single Supply Video Line Driver battery life in portable instruments. The differential reference voltage can range from 0.1V to VCC, providing the flexibility to operate in ratiometric and remote sensing applications. The LTC2411 is not only small and low power, but also very accurate and offers a host of integrated features that make it very easy to use. The LTC2411 performs transparent offset and full-scale calibration on every conversion to provide 5ppm total unadjusted error, 0.5ppm offset error, 4ppm full-scale error and 4ppm integral nonlinearity (INL). It has a proprietary No Latency TM architecture that allows its digital filter to settle in a single cycle, eliminating the need to throw away data after an input signal step, as required with other high resolution ADCs. VCC 2 BRIDGE IMPEDANCE 100 TO 10k 4 5 1F 1 REF + VCC IN + IN - 3 Transparent calibration and single-cycle settling dramatically simplify system software development. Another integrated feature is the highly accurate on-chip oscillator that eliminates the need for external frequency setting components such as crystals or external clock sources. The 4th order sinc filter rejects line frequencies to 110dB and is pin selectable between 50Hz or 60Hz or can be tuned with an external clock input. The external clock feature allows the LTC2411 to output data as fast as 15Hz without compromising the accuracy or to output data faster with reduced resolution. The LTC2411 is available in the MS-10 package in both commercial and industrial temperature ranges. LTC2411 REF - GND 6 9 SDO 8 SCK 7 CS 3-WIRE SPI INTERFACE FO 10 2411 TA02 Figure 1. LTC2411 Directly Digitizes Bridge Output 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 * October 2000 Application of the Month Amplifier with 42V Common Mode Input Range On a Single 5V Supply Without Sacrificing Differential Gain--LT1884 Measuring small voltages on top of large voltages can be quite difficult. Often, the standard difference amplifier topology is implemented with very high value input resistors and low value divide and feedback resistors, as shown in Figure 1. However, this results in significant differential mode attenuation. The circuit in Figure 2 uses an LT1884 to achieve high common mode input range and rejection without sacrificing differential gain. U1B samples the common mode through R5 and R6 and nulls it through R3 and R4. The R3-R1 ratio must be extremely well matched to the R4-R2 ratio to avoid - + 10k 5V 2 R2 1M 3 - 8 U1A 1/2 LT1884 1 + - R3 - + 7 R8* 1M R5* 10k 6 VOUT 2.5V VDM 5V 4 R4 10k 10k R6* 10k 10k LT1634B-2.5 U1B 1/2 LT1884 + 1M R7* 1M R1 1M VCM = 42VP-P VDM = 2.5V 1M The LT1884 dual op amp combines rail-to-rail outputs, 2MHz gain bandwidth product and excellent DC precision. Its low drift input offset voltage is trimmed to 80V while its input offset and input bias currents are a maximum of 900nA. The LT1884 and the quad LT1885 operate over an input range of 2.7V to 36V (or to 18V). Supply current is 1mA maximum per amplifier. causing a common mode to differential mode translation at this point. Once the common mode is nulled, the differential mode input voltage is converted to a differential input current and appears unattenuated across R7. The common mode input voltage can theoretically be as high as about 250V (limited by the output of U1B going to ground and the /100 ratio maintaining common mode at 2.5V), but is limited in fact by the working voltage of R1 and R2 and by the ratio matching of R1-R3 and R2-R4. 10k 5 DN230 F03 REF DN230 F02 *1% METAL FILM CADDOCK (541) 496-0700 T912 0.01% MATCHED RESISTOR PAIRS Figure 1. Standard Difference Amplifier Can Handle High Voltage Common Mode Inputs, But at Cost of Differential Gain Figure 2. Single Supply Difference Amplifier. U1B Nulls the Common Mode So That U1A Can Concentrate on the Difference Mode Dual and Quad Rail-to-Rail Output, Picoamp Input Precision Op Amps--LT1881/LT1882 The LT1881 and LT1882 offer unsurpassed DC precision in a rail-to-rail op amp. The high input precision includes bias and offset currents of 500pA, input offset voltage of less than 80V and a maximum offset drift of 0.8V/C. The LT1881 is also offered in an A grade with reduced bias and offset current of 200pA max and an input offset voltage of 50V. A high 114dB CMRR and an open-loop gain of 120dB add to the precision performance of the parts. AC specs include a gain bandwidth of 1.1MHz (typ) and 0.4V/s slew rate. The amplifiers work on any total power supply voltage between 2.7V and 36V (fully specified at 5V and 15V). The rail-to-rail output voltage swings to within 40mV of the negative supply and 220mV of the positive supply, making these amplifiers an excellent choice for low voltage single supply operation. Both parts are also C-LoadTM stable, driving capacitive loads of up to 1000pF in unity gain. The dual LT1881 and LT1881A are available with standard pinouts in SO-8 and PDIP packages. The quad LT1882 is in a 14-pin SO package. The LT1881 and LT1882 are available in both commercial and industrial temperature grades. For a higher speed device with similar DC specifications, Linear Technology offers the LT1884/LT1885. Table 1. Dual and Quad Rail-to-Rail Output, Picoamp Input Precision Op Amps Offset Voltage (Max) Offset Drift (Max) Bias Current (Max) Offset Current (Max) Gain Bandwidth (Typ) Slew Rate (Typ) LT1881/LT1882 80V 0.8V/C 500pA 500pA 1.2MHz 0.4V/s LT1881A 50V 0.8V/C 200pA 200pA 1.2MHz 0.4V/s LT1884/LT1885 80V 0.8V/C 900pA 900pA 2MHz 0.9V/s LT1884A 50V 0.8V/C 400pA 300pA 2MHz 0.9V/s 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 * October 2000 3 New LDO Regulators Have Lowest Noise, Withstand Reverse Voltage and Operate with Low Cost Ceramic Capacitors--LT1962/LT1963 The LT1962 and LT1963 are the latest members of LTC's advanced low dropout voltage (LDO) regulator family (Table 1). The devices operate from 2.3V to 20V input supplies, offering compatibility with a wide variety of input power sources. Built-in protection circuitry in these regulators guards against reverse current flow without requiring external protection diodes. In addition, the outputs can be pulled below ground without damaging the devices. Other protection includes current limiting and thermal limiting. LT1962: 300mA, 300mV Dropout and Low Supply Current The LT1962 is a micropower regulator that offers the lowest supply current and the lowest noise in the industry. Sourcing up to 300mA with only 270mV* dropout in a tiny 8-lead MSOP package, the device is ideal for powering embedded processors and DSPs in applications such as notebook PCs, PDAs, cellular phones and portable instruments. By using a tiny 0.01F bypass capacitor, only 20VRMS output noise over a 10kHz to 100kHz bandwidth is generated by the LT1962. Supply current is only 30A operating and less than 0.5A in shutdown mode, virtually eliminating battery drain. The design works with all types of capacitors in values as low as 3.3F and is stable using low ESR, low cost ceramic capacitors, allowing the smallest total solution for space-constrained applications. Output voltages are fixed at 1.5V, 1.8V, 2.5V, 3.3V and 5V or can be adjusted between 1.22V and 20V. LT1963: 1.5A with Fast Transient Response The LT1963 is a fast transient response, low noise regulator for multipurpose use over wide input and output voltage ranges. It can deliver up to 1.5A with only a 340mV dropout and with only 40VRMS output noise over a 10Hz to 100kHz bandwidth, which makes it useful for powering noisesensitive RF circuits. Very low dropout means it will regulate 2.5V supplies from a 3.3V input. The LT1963 is ideal for powering FPGAs, ASICs and DSPs in applications such as telecommunications, data processing and networking. Stable with all types of capacitors, including low ESR, surface mount ceramic capacitors, the LT1963 provides the smallest total solution. Its supply current of 1mA is reduced to less than 1A in shutdown. Outputs of 1.5V, 1.8V, 2.5V, 3.3V and a version that can be adjusted between 1.21V and 20V are each available in an 8-lead SO, SOT-223, 5-lead TO-220 and DD packages. *Typical values unless stated otherwise. See data sheets. Table 1. Low Noise, Low Dropout Regulator Family Output Current Quiescent Current RMS Noise 10Hz to 100kHz CBYP = 0.01F Packages Dropout Voltage at Max Output LT1761 100mA 20A 20V SOT-23 0.34V LT1762 150mA 25A 20V MSOP-8 0.27V LT1962 300mA 30A 20V MSOP-8 0.27V LT1763 500mA 30A 20V SO-8 0.3V LT1963 1.5A 1mA 40V SO-8, SOT-223 DD, TO-220 0.34V LT1764 3A 1mA 40V DD, TO-220 0.34V Device Micropower Fast Transient LT1930 and LT1931 from page 1 The LT1931 may use tiny uncoupled inductors to fit within a 0.1 in2 (65mm2) area. This circuit has an output voltage ripple of only 6mVP-P. In applications where soft- start is required, a resistor, a diode and a capacitor may be added to the shutdown circuit to limit how quickly VOUT can be charged. C2 1F L1 10H VIN 5V L2 10H D1 OPTIONAL SOFT-START VIN VSS SW SHDN C1 4.7F R1 29.4k LT1931 NFB GND R2 10k C4 220pF VOUT -5V 350mA C3 22F VOUT C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK325BJ226MM D1: ON SEMICONDUCTOR MBR0520 L1, L2: LQH3C100K04 1931 F01 Linear Technology Products Are Distributed By: Arrow Electronics Arrow/Zeus Components Digi-Key Gerber Electronics Avnet Wyle Electronics Figure 2. 300mA 5V TO - 5V Converter Fits in 0.1in2 (65mm2) (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 Literature Only: 1-800-4-LINEAR 4Linear Technology Corporation * 1630 McCarthy Blvd. * Milpitas, CA 95035-7417 * (408) 432-1900 * FAX: (408) 434-0507 Linear Technology* For Chronicle * October 2000