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SP8527
Micropower Sampling 10-Bit A/D Converter
s s s s s s s s s Low Cost 10-Bit Serial Sampling ADC Guaranteed +1.0 LSB Max INL 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 Digital Serial Interface Sample Rate: 26.1S
DESCRIPTION The SP8527 is a very low power 10-Bit A/D converter. The SP8527 typically draws 230A 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.
GND VCC
REFL
Internal VCC
10
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
SP8527 Block Diagram
SP8527DS/01 SP8527 Micropower Sampling 10-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 K,B Differential Linearity Error K,B Gain Error K,B Offset Error 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. 10 +0.5 +1.0 +0.6 +2.0 +0.2 +2.0 +0.3 +2.0 0 Vref 0 10 +0.5 +1.0 +0.6 +2.0 +0.2 +2.0 +0.3 +3.0 Vref 20 100 3 100 .001 1 VCC+.05 1.5 10 38.3 2.0 .9 .9 3.0 1.4 1.4 25.5
UNITS Bits LSB LSB LSB LSB
CONDITIONS
20 100 3 100 .001 1 -.05 VCC+.05 -.05 1.5 10
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
SP8527DS/01
SP8527 Micropower Sampling 10-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. 0.8 2.0 +2.0 3.0 3.0 2.0 +2.0 0.8
UNITS 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
70
68
dB
For all FFT's (Full Differential Mode) If VCC = 5V fsample = 38.3kHz fin = 15kHz
Total Harmonic Distortion (THD) Signal to Noise & Distortion (SINAD) Signal to Noise (SNR) SAMPLING DYNAMICS Acquisition Time to 0.05% -3dB Small Signal BW Aperture Delay Aperture Jitter Common-Mode Rejection Ratio
-70 60 61
-70 60 61
dB dB dB If VCC = 3.3V fsample = 25.5kHz fin = 12kHz
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 2.5 80 .001 300 0.5 A A mW W (CS=0) 38.3kHz, 5V conversion rate. 25.5kHz 3.3 volts (CS=1)
0.26 0.99 .003 1.7
0 to +70C -40 to +85C -65 to +150C
0 to +70C -40 to +85C -65 to +150C
C C C
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
3
SPECIFICATIONS (cont.) Recommended Operating Conditions
SYMBOL VCC fCLK tCYC tsuCS tWHCLK tWLCLK tWHCS tSAMPLE tCONV tCLK ten tDIS tR tF tHDO 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 S/H Acquisition Time ADC Conversion Time Clock Period SCLK to DOUT Enable
w
MIN. +3.0
VCC=5.0V TYP. MAX. +5.0 +5.5 500
MIN. +3.0
VCC=3.3V TYP. MAX. +3.3 +5.5 333
UNITS Volts kHz S nS S S nS
26.1 100 .9 .9 100
39.2 150 1.4 1.4 150
2 10 2.0 80 80 5 5
w
2 10 3.0 200 200 25 25 200 150 150 10 10 150 300 200 50 50 300
SCLK Cycles SCLK Cycles S nS nS nS nS nS
CSN to DOUT Hi - Z DOUT Rise Time DOUT Fall Time DOUT Valid After SCLK
PIN DESCRIPTION
VREF 1 w +IN 2 -IN 3 GND 4
SP8527DS/01
w
80
PIN ASSIGNMENTS Pin 1- VREF - Reference Voltage Pin 2- +IN - Positive Input
8
VCC SCLK DOUT CS/SHDN
Pin 3- -IN - Negative Input Pin 4- GND - Ground Pin 5- CS/SHDN - Chip Select Bar/Shutdown Pin 6 - DOUT - Data Out
SP8527
7 6 5
Pin 7- SCLK - Serial Clock Pin 8- VCC - Supply
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
4
DESCRIPTION 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 S with a 5V supply voltage applied. The SP8527 will also operate at a 3.3V supply at 39.2 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 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 (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 S and supply current is 230 A (1.15 mW). With a 3.3V supply the conversion plus sampling time is 39.2 S and current is reduced to 80 A (0.26 mW). ADC TRANSFER FUNCTION INPUT VOLTAGE (+IN - -IN) 0 LSB 1 LSB 512 LSB 1022 LSB 1023 LSB INPUT VOLTAGE AT VREF = 5V 0V 0.0049V 2.5000V 4.9902V 4.9951V
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 26.1 S (Duty cycle = 100%) to 5.75 A at 1.04 ms (Duty cycle = 2.5%). Examples: Conversion rate ICC @ 5V Duty Cycle 26.1 S 230 A 100% 52.2 S 115 A 50% 104 S 57.5 A 25% 1.04 mS 5.75 A 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. 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. OUTPUT CODE 0000000000 0000000001 1000000000 1111111110 1111111111
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
5
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. 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. 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 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 6.8F 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 SP8527's equivalent 20 pF of input capacitance from zero volts to the signal level in 1.5 clock periods.
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
6
FIGURE 1. MSB FIRST TIMING
FIGURE 2. DETAILED TIMING SP8527 Timing Diagram
SP8527DS/01
SP8527 Micropower Sampling 10-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 0 512 1023 +1 INLE -1 +1 DNLE -1 0
Vcc = 3.3V Vref = 3.3V
512
1023
Input CMRR Vcc = 5V
100 80
CMRR (dB)
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
(c) Copyright 2000 Sipex Corporation
8
For all plots, VCC = 5V, Conversion Rate = 38.3kHz.
Icc vs. Temperature
250 240 230 1.5 1.0 .05
Gain vs. Temperature
A
LSB
0.00 -0.5 -1.0 -1.5 -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
1.0 .05
FFT 20 dB/div
Spectral Density (dB)
0Hz
1.5
LSB
0 -0.5 -1.0 -1.5 -50 -25 0 25 50 75 temperature (C) 100 125
1.3kHz/div
SNR = THD = SINAD = SFDR = Vinamp = Fund Freq = 61.26 dB -70.7 dB 60.79 dB 70.43 dB -0.49 dB 9.885kHz
10.4kHz
Spurious Free Dynamic Range
80 75 70 68 66 64 62 60 58 56 54 52 50 1000
SINAD
SFDR (dB)
65 60 55 50 1000 input frequency (Hz) 10000
SINAD (dB)
70
10000 input frequency (Hz)
Signal to Noise Ratio
70 68 66 64 62 60 58 56 54 52 50 1000 input frequency (Hz) -50 -55 -60
Total Harmonic Distortion
SNR (dB)
THD (dB)
10000
-65 -70 -75 -80 1000 input frequency (Hz) 10000
SP8527DS/01
SP8527 Micropower Sampling 10-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)
SP8527DS/01
SP8527 Micropower Sampling 10-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)
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
11
ORDERING INFORMATION
Model ........................................................ Linearity (LSB) ..................... Temperature Range ............................................................... Package SP8527BN .......................................................... 1.0 .................................... -40C to +85C .............................................. 8-pin, 0.3" Plastic DIP SP8527KN .......................................................... 1.0 ..................................... -0C to +70C ............................................... 8-pin, 0.3" Plastic DIP SP8527BS .......................................................... 1.0 .................................... -40C to +85C ......................................... 8-pin, 0.15" Plastic SOIC SP8527KS .......................................................... 1.0 ..................................... -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.
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
(c) Copyright 2000 Sipex Corporation
12

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