® SP8527 Micropower Sampling 10-Bit A/D Converter ■ ■ ■ ■ ■ ■ ■ ■ ■ Low Cost 10-Bit Serial Sampling ADC Guaranteed +1.0 LSB Max INL 8-Pin NSOIC Plastic Package Low Power @ 230µA including Automatic Shutdown: 1nA (typ) Full differential input stage Single Supply 3.0V to 5.5V operation Digital Serial Interface Sample Rate: 26.1µS DESCRIPTION The SP8527 is a very low power 10-Bit A/D converter. The SP8527 typically draws 230µA of supply current when sampling at 38.3 kHz. Supply current drops linearly as the sample rate is reduced. The ADC automatically powers down when not performing conversions, drawing only leakage current. The SP8527 is available in 8-Pin NSOIC packages, specified over Commercial and Industrial temperature ranges. The SP8527 is best suited for Battery-Operated Systems, Portable Data Acquisition Instrumentation, Battery Monitoring, and Remote Sensing applications. The serial port allows efficient data transfer to a wide range of microprocessors and microcontrollers over 3 wires. VCC GND Internal VCC REFL 10 REFL DAC VREF Csample P +IN INPUT SWITCHES COMPARATOR SAR PARALLEL TO SERIAL SHIFT REGISTER Dout -IN Csample N CS/SHDN TIMING & CONTROL LOGIC SCLK SP8527 Block Diagram SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 1 © Copyright 2000 Sipex Corporation ABSOLUTE MAXIMUM RATINGS These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. (TA=+25˚C unless otherwise noted) ..................................................... VCC to GND ................................................................................. 7.0V Vin to GND .............................................................. -0.3 to VCC +0.3V Digital input to GND ................................................ -0.3 to VCC +0.3V Digital output to GND .............................................. -0.3 to VCC +0.3V Operating Temperature Range Commercial (J, K Version) ........................................... 0˚C to 70˚C Industrial (A, B Version) .......................................... -40˚C to +85˚C Lead Temperature (Solder 10Sec) ............................................ +300˚C Storage Temperature .................................................. -65˚C to +150˚C Power Dissipation to 70˚C ........................................................ 500mW SPECIFICATIONS Unless otherwise noted the following specifications apply for VCC=5V or 3.3V with limits applicable for Tmin to Tmax. Typical applies for Ta=25˚C. PARAMETERS DC ACCURACY Resolution Integral Linearity K,B VCC=5.0V VCC=3.3V MIN. TYP. MAX. MIN. TYP. MAX. 10 10 UNITS Bits +0.5 +1.0 +0.5 +1.0 LSB Differential Linearity Error K,B +0.6 +2.0 +0.6 +2.0 LSB Gain Error K,B +0.2 +2.0 +0.2 +2.0 LSB Offset Error K,B +0.3 +2.0 +0.3 +3.0 LSB ANALOG INPUT Input Signal FS Range Input Impedance On Channel Off Channel Input Bias Current Analog Input Range 0 Vref 0 Vref 20 100 3 100 .001 1 -.05 VCC+.05 -.05 20 100 3 100 .001 1 VCC+.05 pF MΩ pF MΩ µA Volts clock cycles clock cycles kHz µS µS µS CONVERSION SPEED Sample Time 1.5 1.5 Conversion Time 10 10 Complete Cycle Clock Period Clock High Time Clock Low Time SP8527DS/01 38.3 2.0 .9 .9 CONDITIONS 25.5 3.0 1.4 1.4 SP8527 Micropower Sampling 10-Bit A/D Converter 2 In Parallel with 100MΩ In Parallel with 100MΩ See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams © Copyright 2000 Sipex Corporation SPECIFICATIONS (cont.) Unless otherwise noted the following specifications apply for VCC=5V or 3.3V with limits applicable for Tmin to Tmax. Typical applies for Ta=25˚C. PARAMETERS DIGITAL INPUTS Input Low Voltage, VIL Input High Voltage, VIH Input Current IIN Input Capacitance DIGITAL OUTPUTS Data Format Data Coding VOH VOL VCC=5.0V VCC=3.3V MIN. TYP. MAX. MIN. TYP. MAX. 0.8 2.0 0.8 2.0 +2.0 +2.0 3.0 3.0 4.0 2.0 0.4 0.4 UNITS CONDITIONS Volts Volts µA pF VDD=5V ±5% VDD=5V ±5% Volts Volts AC ACCURACY Spurious free Dynamic Range (SFDR) 70 68 dB Total Harmonic Distortion (THD) -70 -70 dB Signal to Noise & Distortion (SINAD) 60 60 dB Signal to Noise (SNR) 61 61 dB SAMPLING DYNAMICS Acquisition Time to 0.05% 2 -3dB Small Signal BW Aperture Delay Aperture Jitter Common-Mode Rejection Ratio POWER SUPPLIES VCC ICC 70 3 4 20 150 80 3 70 4.5 3 30 150 80 See Timing Diagram VDD=5V +5%, IOH=-0.4mA VDD=5V +5%, IOL=+1.6mA For all FFT’s (Full Differential Mode) If VCC = 5V fsample = 38.3kHz fin = 15kHz If VCC = 3.3V fsample = 25.5kHz fin = 12kHz µs MHz nS pS dB fCM = 15kHz @ 5 volts 2.8kHz @ 3.3 volts Volts +3.0 +5.0 +5.5 +3.0 +3.3 +5.5 Operation Mode 230 400 80 300 µA (CS=0) 38.3kHz, 5V conversion rate. 25.5kHz 3.3 volts Shutdown Mode .001 0.5 .001 0.5 µA (CS=1) Power Dissipation Operating Mode Shutdown Mode 1.15 .005 2 2.5 0.26 0.99 .003 1.7 TEMPERATURE RANGE Commercial Industrial Storage SP8527DS/01 0˚ to +70˚C -40˚ to +85˚C -65˚ to +150˚C 0˚ to +70˚C -40˚ to +85˚C -65˚ to +150˚C mW µW ˚C ˚C ˚C SP8527 Micropower Sampling 10-Bit A/D Converter 3 © Copyright 2000 Sipex Corporation SPECIFICATIONS (cont.) Recommended Operating Conditions MIN. +3.0 VCC=5.0V TYP. MAX. +5.0 +5.5 MIN. +3.0 VCC=3.3V TYP. MAX. +3.3 +5.5 SYMBOL VCC PARAMETERS Supply Voltage fCLK Clock Frequency tCYC Total Cycle Time 26.1 39.2 µS tsuCS Setup Time CSv Before CLK^ 100 150 nS tWHCLK CLK High Time .9 1.4 µS tWLCLK CLK Low Time .9 1.4 µS tWHCS CS High Time between Data Transfers Cycles 100 150 nS tSAMPLE S/H Acquisition Time 2 2 SCLK Cycles tCONV ADC Conversion Time 10 10 SCLK Cycles tCLK Clock Period ten SCLK to DOUT Enable tDIS 500 2.0 333 UNITS Volts kHz µS 3.0 80 200 150 300 nS CSN to DOUT Hi - Z 80 200 150 200 nS tR DOUT Rise Time 5 25 10 50 nS tF DOUT Fall Time 5 25 10 50 nS tHDO DOUT Valid After SCLK 80 200 150 300 nS ▼ ▼ ▼ PIN ASSIGNMENTS PIN DESCRIPTION Pin 1- VREF - Reference Voltage Pin 2- +IN - Positive Input VREF 1 ▼ -IN 3 GND 4 SP8527 +IN 2 8 VCC Pin 3- -IN - Negative Input 7 SCLK Pin 4- GND - Ground 6 DOUT 5 CS/SHDN Pin 5- CS/SHDN - Chip Select Bar/Shutdown Pin 6 - DOUT - Data Out Pin 7- SCLK - Serial Clock Pin 8- VCC - Supply SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 4 © Copyright 2000 Sipex Corporation DESCRIPTION The device features automatic shutdown and will shutdown to a +0.5 µA power level as CS is brought high (de-selected). Power is proportional to conversion duty cycle and varies from 230 µA at 26.1 µS (Duty cycle = 100%) to 5.75 µA at 1.04 ms (Duty cycle = 2.5%). The SP8527 is a 10 bit full differential sampling ADC with a serial data interface. The ADC samples and converts 10 bits of data in 26.1 µS with a 5V supply voltage applied. The SP8527 will also operate at a 3.3V supply at 39.2 µS throughput. The device automatically shuts down to a +0.5 µA (MAX) level as soon as the chip is deselected (CS=1). Serial data output is available in an MSB first format. Examples: Conversion rate ICC @ 5V Duty Cycle 26.1 µS 230 µA 100% 52.2 µS 115 µA 50% 104 µS 57.5 µA 25% 1.04 mS 5.75 µA 2.5% The device is configured such that it delivers serial data MSB first requiring 13 clock periods for a full conversion. Please refer to the timing diagram. FEATURES The input sampling scheme is full differential, where the maximum full scale range is VREF. The signal is applied between +IN and -IN. The signals applied at each input may both be dynamic. This is in contrast with pseudo differential devices which must have input low held at a constant level during conversion. The converter will provide significant common mode rejection because of the full differential sampling. Each input independently must remain between ground and Vcc to avoid clamping the inputs. For proper conversion the differential input (+IN - -IN) must be less than or equal to Vref. Circuit Operation The SP8527 is a SAR converter with full differential sampled front end, capacitive DAC, precision comparator, Successive Approximations Register, control logic and data output register. After the input is sampled and held the conversion process begins. The DAC MSB is set and its output is compared with the signal input, if the DAC output is less than the input, the comparator outputs a one which is latched into the SAR and simultaneously made available at the ADC serial output pin. Each bit is tested in a similar manner until the SAR contains a code which represents the signal input to within +1/2 LSB. During this process the SAR content has been shifted out of the ADC serially. The data appears at the DOUT pin MSB through LSB in 13 clock periods. Note that the Chip Select Bar pin must be toggled high between conversions. The DOUT pin will be in a high impedance state whenever Chip Select Bar is high. After Chip Select Bar has been toggled and brought low again, the converter begins a new conversion. The device uses a capacitive DAC architecture which provides the sampling behavior. This results in full Nyquist performance at the fastest throughput rate (38.3kHz) the device is capable of. The power supply voltage is variable from 3.0V to 5.5V which provides supply flexibility. At the 5.0V supply level, conversion plus sampling time is 26.1 µS and supply current is 230 µA (1.15 mW). With a 3.3V supply the conversion plus sampling time is 39.2 µS and current is reduced to 80 µA (0.26 mW). ADC TRANSFER FUNCTION INPUT VOLTAGE (+IN - -IN) INPUT VOLTAGE AT VREF = 5V OUTPUT CODE 0 LSB 1 LSB 512 LSB 1022 LSB 1023 LSB 0V 0.0049V 2.5000V 4.9902V 4.9951V 0000000000 0000000001 1000000000 1111111110 1111111111 SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 5 © Copyright 2000 Sipex Corporation referenced to the ground pin of the converter. This prevents any voltage drops that occur in the power supply's common return from appearing in series with the input signal. Single Ended or Full Differential Operation The SP8527 has a balanced full differential front end. The SP8527 can be used in this manner, or it can be used in single-ended circuits as well. For single-ended systems, simply tie the -IN to the Reference Low of the input signal, which is allowed to range from 0V to VCC. For a full differential sampling configuration, both inputs are sampled and held simultaneously. Because of the balanced differential sampling, dynamic common mode noise riding along the input signal is cancelled above and beyond DC noise. This is a significant improvement over psuedodifferential sampling schemes, where the low side of the input must remain constant during the conversion, and therefore only DC noise (i.e. signal offset) is cancelled. If AC common mode noise is left to be converted along with the differental component, the output signal will be degraded. In full differential mode, the high and low side board traces should run close to each other, with the same layout. This will insure that any noise coupling will be common mode, and cancelled by the converters (patent pending) full differential architecture. If separate analog and digital ground planes are not possible, care should be used to prevent coupling between analog and digital signals. If analog and digital lines must cross, they should do so at right angles. Parallel analog and digital lines should be separated by a circuit board trace which is connected to common. The reference pin on the SP8527 should be kept as clean as possible. A noise signal of 4.88mV (for VREF = 5.0V) will produce 1 lsb of error in the output code. For convenience, the VREF pin can be tied to the VCC pin, but now the same care should be taken with the VCC pin as with the VREF pin. Whether or not VCC is tied to VREF, the VCC pin should always be bypassed to the GROUND pin with a parallel combination of a 6.8µF tantalum and a 0.1µF ceramic capacitor. To maintain maximum system accuracy, the supply connected to the VCC pin should be well isolated from digital supplies and wide load variations. A separate conductor from the supply regulator to the A/D converter will limit the effects of digital switching elsewhere in the system. Power supply noise can degrade the converters performance. Especially corrupting are noise and spikes from a switching power supply. Full differential sampling allows flexibility in converting the input signal. If the signal low- side is already tied to a ground elsewhere in the system, it can be hardwired to the low side input (i.e., -IN) which acts as a signal ground sense, breaking a potential ground loop. It is also possible to drive the inputs balanced differential, as long as both inputs are within the power rails. In this configuration, both the high and low signals have the same impedance looking back to ground, and therefore pick up the same noise along the physical path from signal source (i.e., sensor, transducer, battery) to the converter. This noise becomes common mode, and is cancelled out by the differential sampling of the SP8527. Layout Considerations To preserve the high resolution and linearity of the SP8527 attention must be given to circuit board layout, ground impedance and bypassing. To avoid introducing distortion when driving the A/D converter input, the input signal source should be able to charge the SP8527's equivalent 20 pF of input capacitance from zero volts to the signal level in 1.5 clock periods. A circuit board layout which includes separate analog and digital ground planes will prevent the coupling of noise into sensitive converter circuits and will help to preserve the dynamic performance of the device. In single ended mode, the analog input signal should be SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 6 © Copyright 2000 Sipex Corporation FIGURE 1. MSB FIRST TIMING FIGURE 2. DETAILED TIMING SP8527 Timing Diagram SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 7 © Copyright 2000 Sipex Corporation Icc vs. Sampling Rate (Clock Rate = 333kHz) Vcc = 3.3V 90.0 Icc vs. Sampling Rate (Clock Rate = 500kHz) Vcc = 5V 250.0 80.0 200.0 60.0 50.0 150.0 Icc (µA) Icc (µA) 70.0 40.0 30.0 100.0 20.0 50.0 10.0 0.0 10 100 1000 10000 conversion time (µs) 0.0 100000 10 100 Vcc = 5V Vref = 5V 1000 10000 conversion time (µs) 100000 Vcc = 3.3V Vref = 3.3V +1 +1 INLE INLE -1 +1 +1 DNLE DNLE -1 -1 -1 0 512 1023 512 0 1023 Input CMRR Vcc = 5V 100 CMRR (dB) 80 60 40 20 0 10.0E+0 100.0E+0 1.0E+3 10.0E+3 100.0E+3 1.0E+6 common mode frequency(Hz) SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 8 © Copyright 2000 Sipex Corporation For all plots, VCC = 5V, Conversion Rate = 38.3kHz. Icc vs. Temperature Gain vs. Temperature 250 1.5 240 1.0 .05 LSB µA 230 220 0.00 -0.5 210 -1.0 200 -50 -1.5 -50 -25 0 25 50 temperature (C) 75 100 125 -25 Offset vs. Temperature LSB .05 0 -0.5 0Hz -1.0 -25 0 25 50 75 temperature (C) 100 1.3kHz/div SNR = THD = SINAD = SFDR = Vinamp = Fund Freq = 125 Spurious Free Dynamic Range 75 70 SINAD (dB) SFDR (dB) 125 65 60 55 50 1000 10000 70 68 66 64 62 60 58 56 54 52 50 1000 input frequency (Hz) 10000 input frequency (Hz) Signal to Noise Ratio 70 68 66 64 62 60 58 56 54 52 50 1000 10.4kHz 61.26 dB -70.7 dB 60.79 dB 70.43 dB -0.49 dB 9.885kHz SINAD 80 Total Harmonic Distortion -50 -55 -60 THD (dB) SNR (dB) 100 Spectral Density (dB) 1.0 -65 -70 -75 -80 1000 10000 input frequency (Hz) SP8527DS/01 25 50 75 temperature (C) FFT 20 dB/div 1.5 -1.5 -50 0 10000 input frequency (Hz) SP8527 Micropower Sampling 10-Bit A/D Converter 9 © Copyright 2000 Sipex Corporation PACKAGE: PLASTIC DUAL–IN–LINE (NARROW) E1 E D1 = 0.005" min. (0.127 min.) A1 = 0.015" min. (0.381min.) D A = 0.210" max. (5.334 max). C A2 B1 B e = 0.100 BSC (2.540 BSC) Ø L eA = 0.300 BSC (7.620 BSC) ALTERNATE END PINS (BOTH ENDS) DIMENSIONS (Inches) Minimum/Maximum (mm) 8–PIN 14–PIN 16–PIN 18–PIN 20–PIN 22–PIN A2 0.115/0.195 (2.921/4.953) 0.115/0.195 (2.921/4.953) 0.115/0.195 (2.921/4.953) 0.115/0.195 (2.921/4.953) 0.115/0.195 (2.921/4.953) 0.115/0.195 (2.921/4.953) B 0.014/0.022 (0.356/0.559) 0.014/0.022 (0.356/0.559) 0.014/0.022 (0.356/0.559) 0.014/0.022 (0.356/0.559) 0.014/0.022 (0.356/0.559) 0.014/0.022 (0.356/0.559) B1 0.045/0.070 (1.143/1.778) 0.045/0.070 (1.143/1.778) 0.045/0.070 (1.143/1.778) 0.045/0.070 (1.143/1.778) 0.045/0.070 (1.143/1.778) 0.045/0.070 (1.143/1.778) C 0.008/0.014 (0.203/0.356) 0.008/0.014 (0.203/0.356) 0.008/0.014 (0.203/0.356) 0.008/0.014 (0.203/0.356) 0.008/0.014 (0.203/0.356) 0.008/0.014 (0.203/0.356) D 0.355/0.400 0.735/0.775 0.780/0.800 0.880/0.920 0.980/1.060 1.145/1.155 (9.017/10.160) (18.669/19.685) (19.812/20.320) (22.352/23.368) (24.892/26.924) (29.083/29.337) E 0.300/0.325 (7.620/8.255) 0.300/0.325 (7.620/8.255) 0.300/0.325 (7.620/8.255) 0.300/0.325 (7.620/8.255) 0.300/0.325 (7.620/8.255) 0.300/0.325 (7.620/8.255) E1 0.240/0.280 (6.096/7.112) 0.240/0.280 (6.096/7.112) 0.240/0.280 (6.096/7.112) 0.240/0.280 (6.096/7.112) 0.240/0.280 (6.096/7.112) 0.240/0.280 (6.096/7.112) L 0.115/0.150 (2.921/3.810) 0.115/0.150 (2.921/3.810) 0.115/0.150 (2.921/3.810) 0.115/0.150 (2.921/3.810) 0.115/0.150 (2.921/3.810) 0.115/0.150 (2.921/3.810) Ø 0°/ 15° (0°/15°) 0°/ 15° (0°/15°) 0°/ 15° (0°/15°) 0°/ 15° (0°/15°) 0°/ 15° (0°/15°) 0°/ 15° (0°/15°) SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 10 © Copyright 2000 Sipex Corporation PACKAGE: PLASTIC SMALL OUTLINE (SOIC) (NARROW) E H h x 45° D A Ø e B A1 L DIMENSIONS (Inches) Minimum/Maximum (mm) SP8527DS/01 8–PIN 14–PIN 16–PIN A 0.053/0.069 (1.346/1.748) 0.053/0.069 (1.346/1.748) 0.053/0.069 (1.346/1.748) A1 0.004/0.010 (0.102/0.249 0.004/0.010 (0.102/0.249) 0.004/0.010 (0.102/0.249) B 0.014/0.019 (0.35/0.49) 0.013/0.020 (0.330/0.508) 0.013/0.020 (0.330/0.508) D 0.189/0.197 (4.80/5.00) 0.337/0.344 0.386/0.394 (8.552/8.748) (9.802/10.000) E 0.150/0.157 (3.802/3.988) 0.150/0.157 (3.802/3.988) 0.150/0.157 (3.802/3.988) e 0.050 BSC (1.270 BSC) 0.050 BSC (1.270 BSC) 0.050 BSC (1.270 BSC) H 0.228/0.244 (5.801/6.198) 0.228/0.244 (5.801/6.198) 0.228/0.244 (5.801/6.198) h 0.010/0.020 (0.254/0.498) 0.010/0.020 (0.254/0.498) 0.010/0.020 (0.254/0.498) L 0.016/0.050 (0.406/1.270) 0.016/0.050 (0.406/1.270) 0.016/0.050 (0.406/1.270) Ø 0°/8° (0°/8°) 0°/8° (0°/8°) 0°/8° (0°/8°) SP8527 Micropower Sampling 10-Bit A/D Converter 11 © Copyright 2000 Sipex Corporation ORDERING INFORMATION Model ........................................................ Linearity (LSB) ..................... Temperature Range ............................................................... Package SP8527BN .......................................................... ±1.0 .................................... –40˚C to +85˚C .............................................. 8-pin, 0.3" Plastic DIP SP8527KN .......................................................... ±1.0 ..................................... –0˚C to +70˚C ............................................... 8-pin, 0.3" Plastic DIP SP8527BS .......................................................... ±1.0 .................................... –40˚C to +85˚C ......................................... 8-pin, 0.15" Plastic SOIC SP8527KS .......................................................... ±1.0 ..................................... –0˚C to +70˚C .......................................... 8-pin, 0.15" Plastic SOIC Please consult the factory for pricing and availability on a Tape-On-Reel option. Corporation SIGNAL PROCESSING EXCELLENCE Sipex Corporation Headquarters and Sales Office 22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: [email protected] Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others. SP8527DS/01 SP8527 Micropower Sampling 10-Bit A/D Converter 12 © Copyright 2000 Sipex Corporation