LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products December 1997 Product of the Month Step-Down DC/DC Converter Operates from Single Li-Ion Cell VIN 2.7V TO 6V + CIN EFFICIENCY (%) 95 90 85 80 VIN = 3.5V L1 = 33H VOUT = 2.5V RSENSE = 0.1 CT = 270pF 75 70 0.01 0.1 OUTPUT CURRENT (A) 1 1626 F01a Figure 1. LTC1626 Has an Efficiency of 90% over a Load Current Range of 20mA to 500mA GSM cellular telephones or anything that must operate from one Li-Ion cell or three to four NiCd/NiMH cells. The LTC1626 is a cost effective monolithic solution that operates over the entire voltage range of a Li-Ion cell (2.7V to 4.2V) with a maximum input voltage of 7V (see Figure 2). It's ideal for those applications 0.1F 47F 16V PWR VIN VIN SHDN 3900pF that are changing from multiple NiCd or NiMH cells to a single Li-Ion cell in order to reduce the size and weight of the end product. The LTC1626 is offered in a 14-lead SO package. 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. 100 The LTC(R)1626 is the first step-down DC/DC converter that can operate at 100% duty cycle from an input supply as low as 2.5V. Its integrated power switch has an RDS(ON) of only 0.32 (VIN = 4.5V) and is capable of delivering up to 600mA of output current with a peak efficiency of 95%. Its 100% duty cycle and low dropout operation extends the life of a single cell Lithium-Ion battery while Burst ModeTM operation maintains high efficiency at light loads. As shown in Figure 1, the LTC1626 achieves greater than 90% efficiency over a 20mA to 500mA load range. Quiescent current is only 160A and drops down to just 0.5A in shutdown. It is targeted specifically at single cell Li-Ion battery-powered applications such as PDAs, GPSs, low power DSPs, digital cameras, SW LTC1626 PGND L* 33H D1 MBRS130LT RSENSE** 0.1 VOUT 2.5V 0.25A + 470 ITH SENSE + CT SENSE - CT 270pF SGND 1000pF COUT 100F 6.3V 10k VFB * COILTRONICS CTX33-4 ** IRC 1206-R100F AVX TPSD476KO16 AVX TPSC107M006R0150 100pF 10k 1626 F01 Figure 2. The LTC1626 as a High Efficiency 2.5V Step-Down Converter Inside This Issue: LT1460H: First SOT-23 Voltage Reference with Guaranteed 20ppm/C Temperature Coefficient ................................................................................................... 2 LT1316: Micropower Boost Regulator with Programmable Peak Current Limit Extends Battery Life .......................................................................................................... 2 LTC1419: MUX 14-Bit ADC Without Software ......................................................................... 3 LTC1659: Smallest 12-Bit DAC in 8-Pin MSOP Features 0.5LSB Max DNL ......................... 3 LT1510-5: 1.5A Constant-Current/Constant-Voltage Battery Charger in SSOP Package Fits in Cell Phones ............................................................................................................ 4 Linear Technology Chronicle * December 1997 Vol. 6 No. 12 Micropower Op Amp, Comparator and Reference Combined in SO-8 The LTC1541 is a micropower op amp with rail-to-rail outputs, a comparator and a 1.2V reference all combined in a single SO-8 package. It is ideal for cost conscious designs such as battery- or solar-powered systems, GSM phones and IR receivers for remote controls, where it is necessary to put as much functionality (three different building blocks) into as little space as possible. The part operates from a single 2.5V to 12.6V or dual 1.25V to 6.3V supply with a typical quiescent current of just 5A. Both the op amp and comparator feature a common mode input voltage range that extends from the negative supply to within 1.3V of the positive supply. Figure 1 shows the LTC1541 as a pilot light flame detector. The reference output voltage of the LTC1541 is 1.2V 1% over the extended temperature range. The output sources up to 2mA, sinks up to 20A and can drive a bypass capacitor of up to 0.01F without any oscillations. The LTC1541's op amp is internally compensated to be unity-gain stable. Continued on page 4 , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. 1 First SOT-23 Voltage Reference with Guaranteed 20ppm/ C Temperature Coefficient The LT (R)1460HCS3-2.5 and LT1460HCS3-5 precision series 2.5V and 5V bandgap references are now available in the ultrasmall SOT-23 package--the smallest package available in the industry (Figure 1). These new references are trimmed to a guaranteed initial accuracy of 0.2% and a maximum temperature drift of only 20ppm/C, less than half the best drift previously available in a SOT-23 reference. They feature a low 100A supply current (125A for the 5V version) and reverse-battery protection at the input. As shown in Figure 2, the LT1460H's typical accuracy shift is less than 0.02% after being soldered onto a PC board. No output capacitor is required for stability, saving component costs and board space. Output current of 20mA also makes the LT1460 well-suited for use as a low power precision voltage regulator. It is ideal for use in portable meters, precision regula- Figure 1. The LT1460 in a SOT-23 Package Offers 0.2% Initial Accuracy and a TC of 20ppm/C. SOT-23 Package Dimensions Are Approximately 3mm x 1.3mm x 1mm High 6 2 CELLS D1 VIN SHDN FB 5V 50mA R1 1M 1% 5 SW 8 + LT1316 NC 2 LBI RSET 3 10k 1% D1: MOTOROLA MBR0520L L1: SUMIDA CD43-470 LBO GND 4 1 C2 47F NC R2 324k 1% 1316 TA01 Figure 1. The LT1316 as a 2-Cell to 5V Step-Up Converter. It Includes a Low-Battery Detector That Is Active in Shutdown 2 36 LT1460HC LIMITS 32 28 24 20 16 12 2.510 2.500 OUTPUT VOLTAGE (V) 1460S3 TA02 Figure 2. Typical Distribution of SOT-23 LT1460HC VOUT After IR Reflow Solder per JEDEC JESD22-A112 90 3.3VIN EFFICIENCY (%) 2.5VIN make the LT1316 an excellent solution for portable 2- to 4-cell battery-powered devices needing boost or SEPIC configurations and the longest possible battery operating lifetime. The programmable peak switch current limit is set by a resistor from the RSET pin to ground, as shown in Figure 1. This feature also allows smaller sized capacitors and inductors to be used in low current applications. Reduced peak input current further improves system operating time from a battery supply, particularly with alkaline cells. L1 47H C1 47F 40 0 2.490 The LT1316 is a micropower boost DC/DC converter in a tiny MSOP package that operates from an input voltage as low as 1.5V and has a quiescent current (IQ) of just 33A. The peak switch current is userprogrammable from 30mA to 500mA by selecting an inexpensive standard value external resistor. This reduces the peak inductor current and eases battery drain. In shutdown mode, current drops to just 3A. It contains an independent low-battery detector that remains active when the device is shut down. Collectively, these features + 44 8 4 Micropower Boost Regulator with Programmable Peak Current Limit Extends Battery Life 7 48 DISTRIBUTION (%) tors and in data conversion applications where space and power are limited. Three electrical grades of the LT1460 in SOT-23 are offered. The prime grade (H) offers an initial accuracy of 0.2% along with the lowest TC available (20ppm/C). The next grade (J) offers the same low TC with 0.4% initial accuracy. The low cost (K) grade offers 0.5% initial accuracy with a TC of less than 50ppm/C. In addition to the 3-lead SOT-23, the LT1460 is also offered in 8-pin PDIP, SO, MSOP and 3-lead TO-92 packages. For a data sheet and evaluation samples, contact your local Linear Technology sales office or visit our web site at www.linear-tech.com for more information. 1.8VIN 80 70 60 0.1 1 10 100 LOAD CURRENT (mA) 1316 TA02 Figure 2. Efficiency vs Load Current for the LT1316 The LT1316 also has a 30V switch voltage which is useful for LCD bias applications that require a 28V bias supply. LCD bias supplies often operate on just milliamps of load current, so the peak switch current needed in such an application is very low. Setting the LT1316's peak switch current limit to match what is needed will greatly increase battery life. Figure 2 shows the efficiency vs load current for three input voltages --3.3V, 2.5V and 1.8V. The LT1316 is available in commercial and industrial temperature range versions in 8-lead MSOP and SO packages. Contact your local Linear Technology sales office for a data sheet and evaluation samples or visit our web site at www.linear-tech.com for more information. Linear Technology Chronicle * December 1997 Application of the Month MUX 14-Bit ADC Without Software to the LTC1419. After each of the eight channels has been selected, the counter rolls over to zero and the process repeats. At any time, the input multiplexer channel can be reset to 0 by applying a logic high pulse to Pin 7 of the counter. 5V AIN O AIN 1 AIN 2 AIN 3 AIN 4 AIN 5 AIN 6 AIN 7 3 CS/LD 1 5 2 4 74HC4520 14 13 12 11 10 1 COM 2 3 4 INH 5 GND VSS 7 3 8 4 + 10F 0.1F 5 6 7 0.1F B C 7 8 3 4 5 6 -5V 10 1Q0 1Q1 1Q2 1Q3 1 1CLK 2Q3 2 1CE 2Q2 7 1CLEAR 2Q1 15 2CLEAR 2Q0 16 VCC 2CE 11 12 13 14 0.1F 0.1F 8 + AIN -A AVDD IN DVDD VREF VSS COMP BUSY AGND CS D13 (MSB) CONVST D12 RD D11 SHDN D10 D0 D9 D1 D8 D2 D7 D3 D6 D4 DGND D5 28 27 26 25 BUSY 24 23 CONVERT CONTROL 22 21 20 19 18 17 16 15 5V GND DATA 0-13 CLEAR COUNT 1419 F00 Figure 1. This Simple Stand-Alone Circuit Requires No Software to Sequentially Sample and Convert Eight Analog Signal Channels at 14-Bit Resolution and 100ksps/Channel buffer amplifier and a 3-wire cascadable serial interface, as shown in Figure 1. Its DNL (differential nonlinearity) of only 0.5LSB (max) guarantees 12-bit monotonic performance, critical in control loop applications. The LTC1659's reference input can be tied to the supply voltage, 2.7V to 5.5V, allowing a rail-to-rail output swing to VCC. The rail-to-rail output amplifier has improved capacitive load handling over competing devices and is capable of REF 12-BIT DAC - VOUT 7 RAIL-TO-RAIL VOLTAGE OUTPUT 4 DOUT TO OTHER DACS 2 6 6 + 12-BIT SHIFT REG AND DAC LATCH 1 3 1F 2CLK 9 2 DIN P 12 0.1F LTC1419 6 VCC 1 CLK 15 16 9 The LTC1659 is a micropower 12-bit rail-to-rail VOUT DAC offered in an 8-pin MSOP package--the smallest 12-bit DAC in the industry. It includes a rail-to-rail output 8 14 0.1F VCC 0 A Smallest 12-Bit DAC in 8-Pin MSOP Features 0.5LSB Max DNL 2.7V TO 5.5V 13 10F + 74HC4051 -5V 10F 5V + The circuit at right uses hardware instead of software routines to select multiplexer channels in a data acquisition system. The circuit features the LTC1419 800ksps 14-bit ADC. It receives and converts signals from a 74HC4051 8-channel multiplexer. Three of the four output bits from an additional circuit, the 74HC4520 dual 4-bit binary counter, are used to select a multiplexer channel. A logic high poweron or processor-generated reset is applied to the counter's Pin 7. After the counter is cleared, the multiplexer's channel selection input is 000 and the input to channel is applied to the LTC1419's S/H input. The channel selection counter is clocked by the rising edge of the convert start (CONVST ) signal that initiates a conversion. As each CONVST pulse increments the counter from 000 to 111, each multiplexer channel is individually selected and its input signal is applied POWER-ON RESET GND 1659 TA01 5 Figure 1. The LTC1659 12-Bit Rail-to-Rail DAC Operates over a 3V to 5V Supply Range and Draws Only 250A Linear Technology Chronicle * December 1997 driving over 1000pF without oscillation. The LTC1659 draws only 250A (typ) quiescent current from a single 5V supply. These features make it well-suited for general trimming applications, portable and batterypowered equipment and in industrial control systems where space is critical. The LTC1659's 3-wire cascadable serial interface is compatible with SPI and MICROWIRETM serial protocols. This eases the connection to the serial interface of most microprocessors and microcontrollers and simplifies transmitting through isolation barriers or to remote locations. Power-on reset insures the DAC starts at zero scale after power-up. The LTC1659's Schmitt trigger clock input permits a direct optocoupler interface. The LTC1659 is immediately available in volume from stock in 8-lead MSOP or SO packages. For a data sheet and evaluation samples, contact your local Linear Technology sales office or visit our web site at www.linear-tech.com for more information. MICROWIRE is a trademark of National Semiconductor Corp. 3 1.5A Constant-Current/Constant-Voltage Battery Charger in SSOP Package Fits in Cell Phones The 500kHz LT1510-5 current mode PWM battery charger delivers up to 1.5A charging current from a 16-lead SSOP package and is small enough to integrate into the tight confines of a miniature cell phone. It provides the constant-voltage/constantcurrent profile required by Li-Ion batteries (see Figure 1) and the constant-current charging needed by NiCd and NiMH batteries. Its 500kHz operation allows use of very small inductors and just a single one-tenth watt resistor is needed to program charging current from milliamps to 1.5A. In a 16-lead SSOP (G-package), the LT1510 has a PCB footprint equal to that of an SO-8. These features make the device ideal for very small cell phone designs that require a charger. It's also well-suited in handheld instruments and electronic organizers where space and height are very limited. The LT1510, offered with switching frequencies of 200kHz or 500kHz (LT1510-5) and in a small outline package, keeps the total PCB solution size very small--less than 0.8in2(5.2cm2). The advantage of a 500kHz switching regulator charger IC is that the required inductor value is smaller for a given charging current, compared to the 200kHz version. New thin inductors as small as 1.8mm in height can requirements of Li-Ion cells. The normal charger-to-battery blocking diode is eliminated since the LT1510 goes into a 3A sleep mode when the charging supply is removed. A soft start capability avoids overloading wall adapter supplies at start-up. The LT1510 is available in 16-lead SSOP, SO and PDIP packages for constantcurrent/constant-voltage chargers and is also available in an SO-8 as a dedicated constantcurrent charger. All devices are available from stock in commercial and industrial temperature versions. Contact your local Linear Technology sales office for a data sheet and evaluation samples. Visit our web site at www.linear-tech.com for more information. now be used in space restricted cell phone designs and other handheld instruments. The LT1510's wide 8V to 28V input voltage range handles all wall adapter and automotive battery inputs. An on-chip 2A saturating power switch permits up to 90% efficiency. Current can be monitored at either battery terminal, allowing the negative terminal to be system ground. The LT1510's 0.5% accurate internal voltage reference meets the critical constant-voltage C1 0.22F D3 MBRM120T3 D1 MBRM120T3 SW VCC BOOST L1** 10H D2 MMBD914L + PROG 1F LT1510-5 GND VC 8.2V TO 20V -+ CIN* 10F 0.1F 300 6.19k 1k OVP SENSE BAT + COUT*** 22F + 4.2V * TOKIN OR MARCON CERAMIC SURFACE MOUNT ** COILTRONICS TP3-100, 10H, 2.2mm HEIGHT (0.8A CHARGING CURRENT) COILTRONICS TP1 SERIES, 10H, 1.8mm HEIGHT (<0.5A CHARGING CURRENT) *** PANASONIC EEFCD1B220 OPTIONAL, SEE APPLICATIONS INFORMATION IN THE DATA SHEET Q3 2N7002 R3 70.6k 0.25% R4 100k 0.25% 1510 F01 Figure 1. The LT1510 as a Li-Ion Constant-Current/Constant-Voltage Battery Charger Uses a Single Resistor to Set the Full Charging Current (1.5A) to Within 5% Accuracy LTC1541 from page 1 The comparator has 3mV of hysteresis to ensure clean output switching, even with slow moving input signals. To minimize pin count, the inverting input of the LTC1541 comparator is internally connected to the reference output. The LTC1541 is screened to the commercial and industrial temperature ranges. For a data sheet and evaluation samples, contact your local Linear Technology sales office. For more information, visit our web site at www.linear-tech.com. Linear Technology Products Are Distributed By: 2M TPO610L TYPE R 2N4391 100k - + 6.2V ZENER 3 100k 2N4391 + 8 1/2 LTC1541 2 1 5 - 6 10M VIN = 8V TO 12V ICC = 9s AT VIN = 9V 82.5k + 1/2 LTC1541 0.1F 7 OUTPUT - VREF = 1.2V LTC1541 * TA01 Figure 1. In This Pilot Light Flame Detector Using an LTC1541, the Thermocouple Signal Is Amplified by the Op Amp and Compared to the Reference to Produce "Digital" Output Almac/Arrow Arrow/Schweber Arrow/Zeus Digi-Key Electrosonic Gerber Electronics Farnell Electronics Marshall Industries Phase 1 (c) 1997 Linear Technology Corporation/Printed in USA 4 Technology Corporation * 1630 McCarthy Blvd. * Milpitas, CA 95035-7417 * (408) 432-1900 * FAX: (408) 434-0507 Linear * www.linear-tech.com * For Literature 1-800-4-LINEAR Linear Technology Chronicle * Only: December 1997