LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products August 2000 Product of the Month 24-Bit, No Latency Delta-SigmaTM ADC with Differential Inputs and Differential Reference--LTC2410 The LTC(R)2410 is the most accurate, simplest and smallest 24-bit analog-to-digital converter with differential inputs on the market today. This device operates on supplies from 2.7V to 5.5V and can accept any differential reference voltage from 0.1V to VCC, providing flexibility in ratiometric and remote sensing applications. It consumes just 200A during conversion and 20A 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, temperature 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, 0.5V offset error and 2.5ppm full-scale error with unmeasurable drifts (only 0.001ppm/C). Its high accuracy DNL guarantees true 24-bit output with no missing codes and its integral nonlinearity (INL) is only 2ppm (2.5V reference). 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 architecture that allows single cycle settling for multiplexed applications. Single cycle settling and transparent calibration simplify system design by reducing software overhead. The performance of the LTC2410 provides the highest level of accuracy for VCC 3 BRIDGE IMPEDANCE 100 TO10k 5 6 2 REF + VCC IN + IN - 4 1F 12 SDO 13 SCK LTC2410 3-WIRE SPI INTERFACE the most demanding "bridge to bits" applications (see Figure 1). The LTC2410 includes a highly accurate 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 impressive 140dB. When clocked externally, the LTC2410 allows output word rates up to 15Hz. Faster rates are possible at reduced resolution. This device eliminates configuration and calibration registers, external components 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. 0.05%, 10ppm/ C, SOT-23 Series Reference Features 0.1V Dropout and 35A Supply Current --LT1790 11 CS REF - GND 1, 7, 8 9, 10, 15, 16 FO 14 2410 TA02 Figure 1. LTC2410 Directly Digitizes Differential Bridge Output 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 Linear Technology Chronicle * August 2000 Vol. 9 No. 8 Despite its tiny SOT-23 package, the LT(R)1790 provides very high precision and low noise (Table 1). Small size and precision plus the 35A supply current and low dropout voltage make the LT1790 ideal for use in battery pack and battery-powered portable products. The LT1790 generates noise of only 12VP-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. Continued on page 2 , 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. I2C is a trademark of Philips Electronics N.V. 1 LT1790 from page 1 With the wide - 40C to 125C operating 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 industrial 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/kHr 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 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 10ppm/C Max 25ppm/C Max 0.1V Max 0.1V Max 2.6V to 18V 2.6V to 18V 60A Max 60A Max 40ppm 40ppm 50ppm/ kHr 50ppm/ kHr Temperature Coefficient Dropout Voltage Input Voltage Range Supply Current Temperature Hysteresis Long-Term Drift Noise: 0.1Hz to 10Hz 12VP-P 12VP-P Noise: 10Hz to 1kHz 33VRMS 33VRMS 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 controller for single and dual band GSM/PCS cellular phones. The product eliminates op amps, detector diodes, MUXes (multiplexers) and over ten discrete components, shrinking the design into a tiny MSOP package (Figure 1). Excellent temperature stability minimizes a cell phone's production test time by allowing a single calibration 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 manufacturers. 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 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 version 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 3lead and 5-lead SOT-23 packages. VOUT = 2.5V 2.6V VIN 18V 0.1F LT1790 1F Figure 1. Series Precision Reference Has Small Size and Big Performance 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 output 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 1A in shutdown to conserve 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 offered 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. 68 VIN 33pF Li-Ion SHDN BSEL LTC1757A-2 1 2 3 4 5 VIN VCC RF VPCA SHDN VPCB BSEL TXEN GND PCTL 10 DIRECTIONAL COUPLER 9 8 7 900MHz DIPLEXER RF PA TXEN 6 50 DAC 1.8GHz /1.9GHz RF PA 1757A TA01 Figure 1. LTC1757A-2: Dual Band Cellular Telephone RF Power Controller 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 * August 2000 Application of the Month Single Cell Li-Ion to 3.3V Converter is Tiny and Draws Very Low Power--LT1615 This photo illustrates the Burst ModeTM operation of the LT1615. The device is in standby, drawing only 20A quiescent current, between bursts. For the SEPIC, the switch current is split equally between the two inductors, with both inductors providing current to the load when the switch is turned off. Typical efficiency for this converter is 70%. With a resistor value change, the circuit 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 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 separate inductors, but a single, dual-winding inductor (a 1:1 transformer) can be substituted. Figure 2 shows the switching waveforms for this SEPIC converter with an input voltage of 2.7V and a 50mA load. C3 1F L1 10H VIN 2.5V TO 4.2V 5 1 VIN SW C1 4.7F FB SHDN VOUT 20mV/DIV AC COUPLED VOUT 3.3V 50mA 4.7pF L2 10H LT1615 4 D1 1M IL1 200mA/DIV C2 10F 3 GND 604k VSW 5V/DIV 2 C1: TAIYO YUDEN LMK316BJ475 C2: TAIYO YUDEN JMK316BJ106 C3: TAIYO YUDEN JMK107BJ105 L1, L2: MURATA LQH3C100K24 D1: MOTOROLA MBR0520 and a long battery life. It uses a current limited, fixed off-time control scheme which helps achieve high efficiency operation over a wide range of load currents. Shutdown quiescent current is 0.5A. The LT1615 uses tiny, low profile inductors and capacitors. The LT1615 is pin compatible with the LT1613 current mode, constant frequency 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. (408) 573-4150 (408) 573-4150 (408) 573-4150 (814) 237-1431 (800) 441-2447 1615 TA07 2s/DIV Figure 2. Switching Waveforms of the 3.3V SEPIC Converter with 50mA Load Figure 1. Li-Ion to 3.3V SEPIC Converter Parallel 16-Bit Rail-to-Rail Output DAC Gives 16-Bit Monotonicity On a Single 3V Supply--LTC1657L or two times the reference voltage depending on how the X1/X2 pin is connected. 1.0 0.8 0.6 DNL ERROR (LSB) The new LTC1657L is a parallel 16-bit voltage output DAC designed for 3V single supply operation. The differential nonlinearity (DNL) of the LTC1657L is only 1LSB (maximum), guaranteeing true 16-bit monotonic 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 650A (typical) of operating current. The LTC1657L offers an internal railto-rail output buffer and 1.25V reference, minimizing external components. A reference input pin can be driven by an external reference if different output voltage ranges are desired. The full-scale output can be one 0.4 0.2 0 - 0.2 - 0.4 - 0.6 - 0.8 - 1.0 0 16484 32768 CODE 49152 65535 1657 TA02 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 applications. The LTC1657L is also available in the 28-pin PDIP. The part is available in both commercial and industrial temperature ranges. Figure 1. Differential Nonlinearity vs Input Code 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 * August 2000 3 Smallest and Most Efficient High Current Synchronous Regulators for Processors, ASICs and FPGAs * Soft-latch overvoltage function saves LTC offers the smallest, most efficient Features include: high output current solutions for micropro* All surface mount with no heat sinks cessors, DSPs, ASICs and FPGAs in applica- * Outputs operate 180 out of phase to reduce input ripple current, input capacitions such as PCs, workstations, network tance and EMI routers and telecom switches (Table 1). Many controllers include the VID function for CPU * Unique OPTI-LOOPTM compensation core voltage maximization (Figure 1). allows fewer output capacitors * * components and eliminates nuisance power supply trips 300kHz to 550kHz fixed frequency operation 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 LT1339 1 - 10V to 60V 1.25V to 5V 50A - 20-Lead SO Packages 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 28-Lead SSOP LTC1629-PG 2 - 4V to 36V 0.8V to 5V 42A Yes LTC1649 1 - 2.7V to 6V 1.3V to 2.5V 20A - 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 16-Lead SO 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 + LTC1706-8X 2 VRM8.4 or 9.0 4V to 36V A: 1.3V to 3.5V B: 0.8V to 5V 25A per Channel Yes (PG Version) 28-Lead SSOP 10-Lead MSOP LTC1709-X + LTC1929 4 VRM8.4 or 9.0 4V to 36V 1.3V to 3.5V > 60A Yes 36-Lead SSOP 28-Lead SSOP 4 to 12 VRM8.4 (2n) or 9.0 4V to 36V 1.3V to 3.5V 200A Yes (PG Version) n-LTC1629 + LTC1706-8X (n) 28-Lead SSOP 10-Lead MSOP *With two outputs, channel A has VID control **Select FETs for the maximum output current required 0.1F VIN TG1 RUN/SS 15k LTC1709 1.2nF ITH SGND S 5 VID BITS VID0-VID4 EAIN Q1 S BOOST 1 0.002 0.47F 1H SW1 S Q2 BG1 PGND SENSE1 + SENSE1 - TG2 Q3 S BOOST2 FBOUT SW2 SENSEIN BG2 SENSE 2 + VOS + SENSE 2 - VOUT 1.3V TO 3.5V 40A 1H S S + INTVCC VOS - 0.002 0.47F S VDIFFOUT VIN 5V TO 28V 10F x4 35V 10F Q4 + Q1-Q4 2x FAIRCHILD FDS7760A OR SILICONIX Si4874 COUT 1000F 4V x2 1709 TA01 Linear Technology Products Are Distributed By: Arrow Electronics Arrow/Zeus Components Digi-Key Gerber Electronics Avnet Wyle Electronics Figure 1. Surface Mount, 40A, 2-Phase Step-Down Converter with VID (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. Linear www.linear-tech.com * For Literature Only: 1-800-4-LINEAR 4 Technology Corporation * 1630 McCarthy Blvd. * Milpitas, CA 95035-7417 * (408) 432-1900 * FAX: (408) 434-0507 *Linear Technology Chronicle * August 2000