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SP8528
Micropower Sampling 12-Bit A/D Converter
s s s s s s s s s s s Low Cost 12-Bit Serial Sampling ADC Guaranteed +1.0 LSB Max INL Guaranteed No Missing Codes 8-Pin NSOIC Plastic Package Low Power @ 230A including Automatic Shutdown: 1nA (typ) Full differential input stage Single Supply 3.0V to 5.5V operation Half Duplex Digital Serial Interface Sample Rate: 30.12S Pin Compatible Upgrade to LTC 1286
DESCRIPTION The SP8528 is a very low power 12-Bit A/D converter. The SP8528 typically draws 230A of supply current when sampling at 33.2 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 SP8528 is available in 8-Pin NSOIC packages, specified over Commercial and Industrial temperature ranges. The SP8528 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.
GND VCC
REFL
Internal VCC
12
REFL
DAC
VREF
Csample P
+IN PARALLEL TO SERIAL SHIFT REGISTER
INPUT SWITCHES
-IN
COMPARATOR
SAR
Dout
Csample N
CS/SHDN SCLK
TIMING & CONTROL LOGIC
SP8528 Block Diagram
SP8528DS/01 SP8528 Micropower Sampling 12-Bit A/D Converter (c) Copyright 2000 Sipex Corporation
1
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=+25C 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) ........................................... 0C to 70C Industrial (A, B Version) .......................................... -40C to +85C Lead Temperature (Solder 10Sec) ............................................ +300C Storage Temperature .................................................. -65C to +150C Power Dissipation to 70C ........................................................ 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=25C.
PARAMETERS DC ACCURACY Resolution Integral Linearity J,A K,B Differential Linearity Error J,A K,B Gain Error J,A K,B Offset Error J,A K,B ANALOG INPUT Input Signal FS Range Input Impedance On Channel Off Channel Input Bias Current Analog Input Range CONVERSION SPEED Sample Time Conversion Time Complete Cycle Clock Period Clock High Time Clock Low Time
VCC=5.0V VCC=3.3V MIN. TYP. MAX. MIN. TYP. MAX. 12 +0.6 +2.0 +0.6 +1.0 +0.75 +2.0 +0.75 +1.0 +2.0 +10 +2.0 +8 +1.5 +1.5 0 +5 +3 Vref 0 12 +0.6 +2.0 +0.6 +1.0 +0.75 +2.0 +0.75 +1.0 +2.0 +10 +2.0 +8 +3.0 +3.0 +8 +5 Vref 20 100 3 100 .001 1 VCC+.05 1.5 12 33.2 2.0 .9 .9 3.0 1.4 1.4 22.2
UNITS Bits LSB LSB LSB LSB LSB LSB LSB LSB
CONDITIONS
No Missing Codes
20 100 3 100 .001 1 -.05 VCC+.05 -.05 1.5 12
pF M pF M A Volts clock cycles clock cycles kHz S S S
In Parallel with 100M In Parallel with 100M
See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams See Timing Diagrams
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
2
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=25C.
PARAMETERS DIGITAL INPUTS Input Low Voltage, VIL Input High Voltage, VIH Input Current IIN Input Capacitance DIGITAL OUTPUTS Data Format Data Coding VOH VOL AC ACCURACY Spurious free Dynamic Range (SFDR)
VCC=5.0V VCC=3.3V MIN. TYP. MAX. MIN. TYP. MAX. UNITS 0.8 2.0 +2.0 3.0 3.0 2.0 +2.0 0.8 Volts Volts A pF
CONDITIONS VDD=5V +5% VDD=5V +5%
4.0 0.4
2.0 0.4
Volts Volts
See Timing Diagram VDD=5V 5%, IOH=-0.4mA VDD=5V 5%, IOL=+1.6mA
86
86
dB
For all FFT's (Full Differential Mode) If VCC = 5V fsample = 31.25kHz fin = 15kHz
Total Harmonic Distortion (THD) Signal to Noise & Distortion (SINAD) Signal to Noise (SNR) SAMPLING DYNAMICS Acquisition Time to 0.01% -3dB Small Signal BW Aperture Delay Aperture Jitter Common-Mode Rejection Ratio
-83 73 73.5
-80 72 72.5
dB dB dB If VCC = 3.3V fsample = 20.8kHz fin = 5kHz
2 4 20 150 80
3
3 3 30 150 80
4.5
s MHz nS pS dB
70
70
fCM = 15kHz @ 5 volts 2.8kHz @ 3.3 volts
POWER SUPPLIES VCC ICC Operation Mode Shutdown Mode Power Dissipation Operating Mode Shutdown Mode TEMPERATURE RANGE Commercial Industrial Storage
Volts +3.0 +5.0 +5.5 +3.0 +3.3 +5.5 230 .001 1.15 .005 400 0.5 2 10 80 .001 300 0.5 A A mW W (CS=0) 33.2kHz, 5V conversion rate. 22.2kHz 3.3 volts (CS=1)
0.26 0.99 .003 6.6
0 to +70C -40 to +85C -65 to +150C
0 to +70C -40 to +85C -65 to +150C
C C C
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
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SPECIFICATIONS (cont.) Recommended Operating Conditions
SYMBOL VCC fCLK tCVC tsuCS tWHCLK TWHCLK TWHCS PARAMETERS Supply Voltage Clock Frequency Total Cycle Time Setup Time CSv Before CLK^ CLK High Time CLK Low Time CS High Time between Data Transfers Cycles 30.1 100 .9 .9 100 MIN. +3.0 VCC=5.0V TYP. MAX. +5.0 +5.5 500 45.15 150 1.4 1.4 150 MIN. +3.0 VCC=3.3V TYP. MAX. +3.3 +5.5 333 UNITS Volts kHz S nS S S nS
PIN DESCRIPTION
VREF 1 w +IN 2 -IN 3 GND 4
PIN ASSIGNMENTS Pin 1- VREF - Reference Voltage
8
VCC SCLK DOUT CS/SHDN
Pin 2- +IN - Positive Input Pin 3- -IN - Negative Input Pin 4- GND - Ground Pin 5- CS/SHDN - Chip Select Bar/Shutdown
SP8528
7 6 5
Pin 6 - DOUT - Data Out Pin 7- SCLK - Serial Clock Pin 8- VCC - Supply
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
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DESCRIPTION The SP8528 is a 12 bit full differential sampling ADC with a serial data interface. The ADC samples and converts 12 bits of data in 30.1 S with a 5V supply voltage applied. The SP8528 will also operate at a 3.3V supply at 45.15 S throughput. The device automatically shuts down to a +0.5 A (MAX) level as soon as the chip is deselected (CS=1). Serial data output is available in an MSB first or LSB first format. 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. The device uses a capacitive DAC architecture which provides the sampling behavior. This results in full Nyquist performance at the fastest throughput rate (33.2kHz) 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 30.1 S and supply current is 230 A (1.15 mW). With a 3.3V supply the conversion plus sampling time is 45.15 S and current is reduced to 80 A (0.26 mW). ADC TRANSFER FUNCTION INPUT VOLTAGE (+IN - -IN) 0 LSB 1 LSB 2048 LSB 4094 LSB 4095 LSB INPUT VOLTAGE AT VREF = 5V 0V 0.00122V 2.5000V 4.9976V 4.9988V
The device features automatic shutdown and will shutdown to a +0.5 A power level as CS is brought high (de-selected). Power is proportional to conversion duty cycle and varies from 230 A at 30.1 S (Duty cycle = 100%) to 5.75 A at 1.2 ms (Duty cycle = 2.5%). Examples: Conversion rate ICC @ 5V Duty Cycle 30.1 S 230 A 100% 60.2 S 115 A 50% 120 S 57.5 A 25% 1.20 mS 5.75 A 2.5% The device can be configured such that it delivers serial data MSB first requiring 15 clock periods for a full conversion. Alternately, the device can be programmed to deliver 12 bits of data MSB first, followed by the same 12 bits of data LSB first. This sequence will require 26 clock periods to complete. Please refer to the timing diagram. Circuit Operation The SP8528 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. If the MSB first format was chosen, the data will appear at the DOUT pin MSB through LSB in 15 clock periods. If LSB first data is desired, 26 SCLK's are needed to complete a transfer. The LSB OUTPUT appears at clock 15, with CODE successive bits clocked out until the MSB appears at 000000000000 clock 26. All subsequent 000000000001 SCLK's with CS = 0 shift out 100000000000 0. Note that the Chip Select 111111111110 Bar pin must be toggled high 111111111111
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
5
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. Single Ended or Full Differential Operation The SP8528 has a balanced full differential front end. The SP8528 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. Full differential sampling allows flexibility in converting the input signal. If the signal lowside 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 SP8528. Layout Considerations To preserve the high resolution and linearity of the SP8528 attention must be given to circuit board layout, ground impedance and bypassing.
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 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. 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 SP8528 should be kept as clean as possible. A noise signal of 1.22mV (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 6.8F tantalum and a 0.1F 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. To avoid introducing distortion when driving the A/D converter input, the input signal source should be able to charge the SP8528's equivalent 20 pF of input capacitance from zero volts to the signal level in 1.5 clock periods.
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
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Tcyc PD CSN
1 10 D11 0 D10 D8 D6 D4 D2 D0 D9 D7 D5 D3 D1 15
POWER UP
POWER DOWN
PU Twhcs
SCLK Dout
X HI-Z
X HI-Z
Tconv Tsample
FIGURE 1. MSB FIRST TIMING
Tcyc PD POWER UP POWER DOWN Twhcs CSN
1 10 D11 0 D10 D8 D6 D4 D2 D0 D2 D4 D6 D8 D10 D9 D7 D5 D3 D1 15 D1 D3 20 D5 D7 D9 25 26
PU
SCLK Dout
X HI-Z
D11
X
0
HI-Z
Tconv Tsample
FIGURE 2. LSB FIRST TIMING
Tsucs CSN Tscsu SCLK HI-Z Ten Thdo Twhclk Twlclk Tclk Tdis
Dout
Tf
Tr 10% - 90%
FIGURE 3. DETAILED TIMING SP8528 Timing Diagram
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
7
90.0 80.0 70.0
Icc vs. Sampling Rate (Clock Rate = 333kHz) Vcc = 3.3V
250.0 200.0
Icc vs. Sampling Rate (Clock Rate = 500kHz) Vcc = 5V
Icc (A)
60.0 40.0 30.0 20.0 10.0 0.0 10 100 1000 10000 conversion time (s) 100000 0.0 10 100 1000 10000 conversion time (s) 100000 50.0
Icc (A)
50.0
150.0 100.0
Vcc = 5V Vref = 5V
+1 INLE -1 +1 DNLE -1 +1 INLE -1 +1 DNLE -1
Vcc = 3.3V Vref = 3.3V
0 Vcc = 5V Vref = 3V
+1 INLE
4095
0
4095
Input CMRR Vcc = 5V
100 80
CMRR (dB)
-1 +1 DNLE -1
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)
0
4095
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
8
For all plots, VCC = 5V, Conversion Rate = 31.25kHz. Icc vs. Temperature
250 240 230 6.00 4.00 2.00
Gain vs. Temperature
A
LSB
0.00 -2.00 -4.00 -6.00 -50 -25 0 25 50 75 temperature (C) 100 125
220 210 200 -50
-25
0
25 50 temperature (C)
75
100
125
Offset vs. Temperature
4 2
FFT 20 dB/div
Spectral Density (dB)
0
6
LSB
0 -2 -4 -6 -50 -25 0 25 50 75 temperature (C) 100 125
frequency SNR = 73.01 dB THD = -79.54 dB SINAD = 72.14 dB SFDR = 84.66 dB Vinamp = -0.47 dB
15.6kHz
Spurious Free Dynamic Range
90 80 90 80
SINAD
SFDR (dB)
70 60 50 1000
SINAD (dB)
10000 input frequency (Hz) 100000
70 60 50 1000
10000 input frequency (Hz)
100000
Signal to Noise Ratio
90 80 -50 -60
Total Harmonic Distortion
SNR (dB)
70 60 50 1000
THD (dB)
10000 input frequency (Hz) 100000
-70 -80 -90 1000
10000 input frequency (Hz)
100000
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
9
PACKAGE: PLASTIC DUAL-IN-LINE (NARROW)
E1 E
D1 = 0.005" min. (0.127 min.) D
A1 = 0.015" min. (0.381min.) A = 0.210" max. (5.334 max). A2 C O eA = 0.300 BSC (7.620 BSC) L
e = 0.100 BSC (2.540 BSC)
B1 B
ALTERNATE END PINS (BOTH ENDS)
DIMENSIONS (Inches) Minimum/Maximum (mm) A2 B B1 C D E E1 L O
8-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
14-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
16-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
18-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
20-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
22-PIN 0.115/0.195 (2.921/4.953) 0.014/0.022 (0.356/0.559) 0.045/0.070 (1.143/1.778) 0.008/0.014 (0.203/0.356)
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) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15) 0.300/0.325 (7.620/8.255) 0.240/0.280 (6.096/7.112) 0.115/0.150 (2.921/3.810) 0/ 15 (0/15)
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
10
PACKAGE: PLASTIC SMALL OUTLINE (SOIC) (NARROW)
E
H
h x 45 D A O e B A1 L
DIMENSIONS (Inches) Minimum/Maximum (mm) A A1 B D E e H h L O
8-PIN 0.053/0.069 (1.346/1.748) 0.004/0.010 (0.102/0.249 0.014/0.019 (0.35/0.49) 0.189/0.197 (4.80/5.00) 0.150/0.157 (3.802/3.988) 0.050 BSC (1.270 BSC) 0.228/0.244 (5.801/6.198) 0.010/0.020 (0.254/0.498) 0.016/0.050 (0.406/1.270) 0/8 (0/8)
14-PIN 0.053/0.069 (1.346/1.748) 0.004/0.010 (0.102/0.249) 0.013/0.020 (0.330/0.508)
16-PIN 0.053/0.069 (1.346/1.748) 0.004/0.010 (0.102/0.249) 0.013/0.020 (0.330/0.508)
0.337/0.344 0.386/0.394 (8.552/8.748) (9.802/10.000) 0.150/0.157 (3.802/3.988) 0.050 BSC (1.270 BSC) 0.228/0.244 (5.801/6.198) 0.010/0.020 (0.254/0.498) 0.016/0.050 (0.406/1.270) 0/8 (0/8) 0.150/0.157 (3.802/3.988) 0.050 BSC (1.270 BSC) 0.228/0.244 (5.801/6.198) 0.010/0.020 (0.254/0.498) 0.016/0.050 (0.406/1.270) 0/8 (0/8)
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
11
ORDERING INFORMATION
Model ........................................................ Linearity (LSB) ..................... Temperature Range ............................................................... Package SP8528BN .......................................................... 1.0 .................................... -40C to +85C .............................................. 8-pin, 0.3" Plastic DIP SP8528KN .......................................................... 1.0 ..................................... -0C to +70C ............................................... 8-pin, 0.3" Plastic DIP SP8528BS .......................................................... 1.0 .................................... -40C to +85C ......................................... 8-pin, 0.15" Plastic SOIC SP8528KS .......................................................... 1.0 ..................................... -0C to +70C .......................................... 8-pin, 0.15" Plastic SOIC SP8528AN .......................................................... 2.0 .................................... -40C to +85C .............................................. 8-pin, 0.3" Plastic DIP SP8528JN ........................................................... 2.0 ..................................... -0C to +70C ............................................... 8-pin, 0.3" Plastic DIP SP8528AS .......................................................... 2.0 .................................... -40C to +85C ......................................... 8-pin, 0.15" Plastic SOIC SP8528JS ........................................................... 2.0 ..................................... -0C to +70C .......................................... 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: sales@sipex.com 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.
SP8528DS/01
SP8528 Micropower Sampling 12-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
12

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