sx8725 Semtech Corporation, sx8725 Datasheet
sx8725
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sx8725 Summary of contents
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... ADVANCED COMMUNICATIONS & SENSING Description The SX8725 is a data acquisition system based on Semtech’s low power ZoomingADC™ technology. It directly connects most types of miniature sensors with a general purpose microcontroller. With 1 differential input, it can adapt to multiple sensor systems. Its digital outputs are used to bias or reset the sensing elements ...
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... Registers Descriptions .......................................................................................................................................... 28 RC Register........................................................................................................................................................... 28 GPIO Registers ..................................................................................................................................................... 29 ZADC Registers .................................................................................................................................................... 30 Mode Register ....................................................................................................................................................... 31 Optional Operating Modes: External Voltage Reference Option .......................................................................... 32 Application Hints..................................................................................................................................................33 Recommended Operation Mode and Registers Settings...................................................................................... 33 Operation Mode..................................................................................................................................................... 33 V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Table of Contents 2 SX8725 www.semtech.com ...
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... Differential Non-Linearity....................................................................................................................................... 43 Noise ..................................................................................................................................................................... 44 Gain Error and Offset Error ................................................................................................................................... 46 Power Consumption .............................................................................................................................................. 47 PCB Layout Considerations................................................................................................................................49 How to Evaluate....................................................................................................................................................49 Package Outline Drawing: MLPD-W-12 4x4.......................................................................................................50 Land Pattern Drawing: MLPD-W-12 4x4.............................................................................................................51 Tape and Reel Specification ...............................................................................................................................52 V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 3 SX8725 www.semtech.com ...
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... Notes: This device is ESD sensitive. Use of standard ESD handling precautions is required. V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Symbol Comments / Conditions V BATT T STORE T BIAS V VR_P V VR_N T PKG 4 SX8725 Min Max Unit V - 0.3 5 -55 150 ° C -40 140 ° 300 V ...
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... Smin < 4mA < 4mA > 3V BATT V > 3V, ref to 25° C BATT V > 3V, rms, broadband BATT 5 SX8725 Min Typ Max Unit 2.4 5.5 V -40 125 ° C µA 250 300 700 800 1000 1200 µA 150 300 850 75 200 nA 100 ...
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... V -0.3 V +0.3 SS BATT 78 72 133 1027 1.88 0.485 0 2 www.semtech.com SX8725 = 2. ELCONV Unit V/V V/V V/V V/V % ppm/° C V/V V/V % ppm/° µV µV µV Bits Bits % % LSB LSB LSB LSB LSB cycles/f ...
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... Input impedance is proportional OSR can be set between 8 and 1024, in powers ELCONV = (N (OSR + OSR can be set between 8 and 1024, in powers ELCONV S 7 SX8725 Min Typ Max 0 5 OSR 2.4 5 5.5 800/675 260/190 190/170 150/135 200/180 4.0/2.0 3.2/1.6 2.4/1.1 1 ...
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... HD;STA t SU;STO t BUF SU;STA HD;STA SU;STO 2 Figure Start and Stop timings LOW HIGH HD;DAT SU;DAT 2 Figure Data timings 8 SX8725 Min Typ Max 1 0 400 1.3 0.6 100 0 0.6 0.6 0.6 1 BUF t SP www.semtech.com Unit 1/F S kHz µs µ µs µ ...
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... Differential sensor input in conjunction with AC Bottom ground pad ( should also be connected PCB to reduce noise and improve thermal behavior 8725 yyww xxxxx xxxxx yyww = Date code xxxx = Semtech lot number Function ) ) if V supply is too low. BATT BATT 3 2 www.semtech.com SX8725 ...
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... ADVANCED COMMUNICATIONS & SENSING Circuit Description General Description The SX8725 is a complete low-power acquisition path with programmable gain, acquisition speed and resolution. Block Diagram SX8725 + V REF - AC2 AC3 D0/REF OUT D1/REF IN VREF The internally generated trimmed bandgap reference with a nominal value of 1.22V that provides a REF stable voltage reference for the ZoomingADC ...
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... V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing RegOut[ RegMode[ REF - 1 RegMode[0] RegOut[ Figure 4 - GPIO Block Diagram 11 SX8725 RegOut[0] RegIn[0] ZoomingADC RegOut[1] RegIn[1] th www.semtech.com ...
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... V BATT voltage to above 3V but with diode limiting to BATT . BATT whenever the power supply is supposed to be less or drop below 3V. PUMP 12 SX8725 drops below 3V then the block should may be switched BATT . PUMP is too low. When BATT output above. ...
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... C address set to their programmed values. Once this has been done, the oscillator will be shut down and the chip will enter a sleep state while waiting for an I V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 2 C communication. 13 SX8725 www.semtech.com ...
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... SCL ... 1 9 Ready Master SX8725 Figure 7 - Timing Diagram for Reading an ADC Sample from SX8725 Address 2 The default I C slave address is 1001000 in binary. 2 This is the standard part I C slave address. Other addresses between 1001001 and 1001111 are available by special request. ...
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... V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing PGA1 PGA2 GD2 OFF2 Gain 2 Offset 2 ZOOM combination, the input voltage is modulated and amplified through REF,ADC 15 PGA3 IN,ADC + GD3 - - OFF3 Gain 3 Offset 3 ) are available when REF www.semtech.com SX8725 ADC ...
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... Equation 1 /2 respectively. As will be shown GDoff , ADC TOT IN TOT Equation 2 is the total PGA offset. TOT much higher than the input signal's Nyquist rate (typically -FS/2 to +FS/2 for ADC is related to input voltage V IN,ADC V (V) REF , ADC www.semtech.com SX8725 by the ...
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... A cross) AMUX(2:0) sets the channel BATT REF CONT 010 0 ENABLE[3:0] 0000 PGA2_OFFSET[3:0] 0000 PGA3_GAIN[6:0] 0001100 0000000 00000 125 kHz, 00 62.5 kHz 10. = common reference) AMUX( www.semtech.com SX8725 VMUX 0 ...
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... START bit). As shown in Figure 10, the conversion time is also T . CONV Internal Trig START Request Output Code RegACOut[15:0] IRQ/READY V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing T CONV BUSY T CONV BUSY Figure 10 - ADC "On-Request" Operation 18 SX8725 www.semtech.com ...
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... V INP 01x00 01x01 AC 2 11000 11001 11010 11011 = AC_R REF,ADC 1 V REFN AC_R ( AC_R ( www.semtech.com SX8725 . Let us first = AC - IN1 1 V INN ( REF REF AC_R or 0 and REFP ...
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... PGA3 disabled PGA3 enabled PGA1 Gain GD (V/ PGA3_OFFSET[6:0] PGA2 Gain (RegACCfg4[6:0]) GD (V/ PGA2 Offset GDoff (V/ +0.2 +0.4 +0.6 +0.8 +1 -0.2 -0.4 -0.6 -0 SX8725 PGA3 Gain GD (V/V) 3 0000000 0 0000001 1/12(=0.083) ... ... 0000110 6/12 ... ... 0001100 12/12 0010000 16/12 ... 0100000 32/12 ... 1000000 64/12 ... 1111111 127/12(=10.58) Table 8 - PGA3 Gain Settings PGA3 Offset GDoff (V/V) 3 0000000 ...
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... Equation ( Equation GDoff IN , ADC TOT IN TOT Equation TOT Equation 10 GDoff GDoff GD GDoff TOT 3 3 Equation 11 21 (V) (V) REF , ADC (V) REF , ADC of the ADC is related to IN,ADC V (V) REF , ADC (V/V) (V/V) 2 www.semtech.com SX8725 ...
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... A few additional clock cycles are also required to initiate and end the Elementary Elementary Conversion Conversion 2 N ELCONV - + T CONV FIN[1:0] Over-Sampling Frequency f 00 62.5 kHz 01 125 kHz 10 250 kHz 11 500 kHz 22 elementary incremental conversions and a =1/f s (s) Elementary End Conversion -1 N ELCONV - s . The over-sampling frequency s (Hz) s www.semtech.com SX8725 , i.e.: s Conversion Result noise. ...
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... OSR (-) (RegACCfg0[4:2]) 000 001 010 011 100 128 101 256 110 512 111 1024 Table 11 - Over-Sampling Ratio Settings SET _ NELC ELCONV Equation Elementary SET_NELC[1:0] Conversions (RegACCfg0[6:5]) N ELCONV elementary incremental ELCONV (-) www.semtech.com SX8725 ...
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... Note: shaded area: resolution truncated to 16 bits due to output register size RegACOut[15:0] 24 (Bits) 101 110 111 www.semtech.com SX8725 ...
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... SET_OSR[2:0] and SET_NELC[1:0] CONV s (Normalized to Over-Sampling Period 1/f 16.0 14.0 12.0 10.0 SET_NELC 11 8 6.0 00 4.0 10.0 100.0 1000.0 Normalized Conversion Time - ( 137 133 265 261 521 517 1033 1029 2057 2053 4105 4101 8201 ) s 10000.0 *f [-] CONV S www.semtech.com SX8725 ...
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... V OSR 1 REF , ADC (LSB) V OSR IN (V/V) (V/V) 2 Output Code in Hex 7FFF 7FFE ... +1 0001 0 0000 -1 8FFF ... 8001 -215=-32'768 8000 = 5V, OSR = 64 bits) REF,ADC SET_NELC = 10 SET_NELC = 11 10000000 100000 1000 100 www.semtech.com SX8725 ... ... 1000000 10000 100 ...
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... Equation 19 of the ADC must satisfy the condition: 1 OSR ADC REFP REFN 2 OSR Equation 20 ADC Bias Current 1/4 IADC x 1/2 IADC IADC (V) 1 (V) 1 PGA Bias Current Max. f 125 x 250 500 125 1/4 IPGA 250 1/2 IPGA IPGA 500 www.semtech.com SX8725 [kHz] s ...
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... MSB of the ADC result 7 ADC conversion control 8 ADC conversion control 8 ADC conversion control 8 ADC conversion control 7 ADC conversion control 8 ADC conversion control 6 Chip operating mode register Reset 000000 unused 1 Enables RC oscillator. Set 0 for low power mode. Table 18 - RegRCen (0x30) 28 SX8725 Description Description www.semtech.com ...
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... Output 00 Unused 0 D1 pad output value. Only valid when D1_DIR = 1 and VREF_D1_IN = pad output value. VREF_D0_OUT = 0 Table - 19 RegOut (0x40) Reset 000000 Unused - D1 pad value - D0 pad value Table - 20 RegIn (0x41) 29 SX8725 Description 0 = Input 0 = Input Only valid when D0_DIR = 1 Description www.semtech.com and ...
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... PGA3 offset selection Table 27 - RegACCfg4 (0x56) Reset 0 ADC activity flag 0 Selects ADC & PGA default configuration 00000 Input channel configuration selector 0 Reference source selector (V Table 28 - RegACCfg5 (0x57) 30 SX8725 Description Description Description Description Description Description Description Description = BATT REF www.semtech.com ...
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... Chop state = 1 00: Chop state = 0 (Note 1) 0 Force charge pump On (takes priority) (Note 2) 1 Force charge pump Off (Note 2) 0 Enable VREF output on D0 pin 0 Enable VREF input on D1 pin Table 29 - RegMode (0x70) 31 SX8725 Function drops below 3V to ensure BATT www.semtech.com ...
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... RegMode[ REF - 1 RegMode[ Digital Input / Output 0 1 RegMode[ REF - 1 RegMode[ Reference Voltage Input input. REF,ADC . Simply substitute BATT www.semtech.com SX8725 GPIO ZoomingADC GPIO GPIO ZoomingADC GPIO ...
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... ADC 250 16 512 2 ON Bit Position OUT[7:0] OUT[15:8] SET_OSR[2:0] 01 110 IB_AMP_PGA[1:0] 01 PGA2_OFFSET[3:0] PGA2_GAIN[1:0] PGA3_GAIN[6:0] 0001100 PGA3_OFFSET[6:0] 0000000 AMUX[4:0] 00001 Table 31 - Registers Settings 33 SX8725 Units V/V V/V V/V V/V V/V V kHz Bits OverSamples / ElementaryConversion ElementaryConversion / Conversion - Hexadecimal Value XXXXXXXX XXXXXXXX CONT - 1 0 ENABLE[3:0] 1001 0000 ...
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... V IN AC3 - + D0 D1 Figure 18 - Recommended Operation Mode Schematic V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing ZoomingADC + - + + V REF - - PGA CONTROL LOGIC CHARGE 4MHz GPIO PUMP OSC 34 SX8725 V BATT TM 5V ADC READY SCL SDA V PUMP VSS www.semtech.com + - MCU ...
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... Z The input impedance on channels that are not selected is very high (>100MΩ). V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 9 768 gain s Equation 21 > 6.1MΩ and to stage gain as given in s (Ω) www.semtech.com SX8725 ...
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... Equation equivalent to a resistor Current integration Sensor ZoomingADC (model) impedence Sensor Node Capacitance Figure 20 - The Switched Capacitor Principle , but these will not influence the measurement. Whereas (A) clock by a factor 10, the www.semtech.com SX8725 ...
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... For lowest output offset error at the output of the ADC, bypass PGA2 and PGA3. Indeed, PGA2 and PGA3 typically introduce an offset of about LSB (16 bit) at their output. Note, however, that the ADC output offset is easily calibrated out by software. V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 37 SX8725 www.semtech.com ...
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... ELCONV 0.8 0.6 0.4 0 [-] These notches occur at: ELCONV ,..., ( ELCONV and . s NELCONV OSR [-] 1024 1024 1024 1024 1024 1024 N ELCONV Normalized Frequency - f *(OSR/f ) [-] S N ELCONV Normalized Frequency - f *(OSR/f ) [-] S www.semtech.com SX8725 N [-] ELCONV ELCONV ...
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... Use lower bias currents in the PGAs and the ADC using the control words IB_AMP_PGA[1:0] and IB_AMP_ADC[1:0]. 5. Reduce sampling frequency. Finally, remember that power reduction is typically traded off with reduced linearity, larger noise and slower maximum sampling speed. V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 39 SX8725 www.semtech.com ...
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... PGA is important and the first stage of the PGA should be used. The following figures show the Integral non linearity for different gain settings over the chip temperature range. -40 ° ° C V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Gain 1 40 SX8725 25 ° C 125 ° C www.semtech.com ...
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... ADVANCED COMMUNICATIONS & SENSING -40 ° ° C -40 ° ° C V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Gain 10 Gain 100 41 SX8725 25 ° C 125 ° ° C 125 ° C www.semtech.com ...
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... ADVANCED COMMUNICATIONS & SENSING -40 ° ° C V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Gain 1000 42 SX8725 25 ° C 125 ° C www.semtech.com ...
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... ADVANCED COMMUNICATIONS & SENSING Differential Non-Linearity The differential non-linearity is generated by the ADC. The PGA does not add differential non-linearity. Figure 22 shows the differential non-linearity. Figure 22 - Differential Non-Linearity of the ADC Converter V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 43 SX8725 www.semtech.com ...
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... OSR N ELCONV Equation 25 PGA1 0.85 205 ( V rms and GD are the PGA gains PGA2 PGA3 1.4 340 (V ) 365 ( ELCONV REF www.semtech.com SX8725 of the N,IN ELCONV 1 ...
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... GD2 GD3 PGA2 GD2 GD3 Figure 25 - Total Input Referred Noise = 10 ( PGA3 bypassed), OSR = 512 PGA1 is dominant over that of PGA2. Using Equation 25 ELCONV ADC f s PGA3 V N3 ADC www.semtech.com SX8725 = 2, ELCONV ...
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... Figure 27 - Offset Error vs. Temperature for Different PGA Gains V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing NORMALIZED TO 25° C 0.2 0.1 0.0 -0.1 -0.2 -0.3 -0.4 -50 - Temperature [°C] NORMALIZED TO 25° C 100 -20 -40 -50 - Temperature [°C] 46 SX8725 100 75 100 100 75 100 www.semtech.com ...
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... Quiescent current consumption vs. temperature is depicted in Figure 30, showing a relative increase of nearly 40% between -45 and +85°C. Figure 28 - Quiescent Current Consumption vs. Supply Voltage Figure 29 - Quiescent Current Consumption vs. Supply Voltage for Different Sampling Frequencies V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 47 SX8725 , as well as the DD www.semtech.com ...
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... DD Table 34 - Typical Quiescent Current Distributions in Acquisition Chain ( bits, f V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing ADC PGA1 PGA2 127 96 86 105 87 73 105 SX8725 PGA3 TOTAL Unit 97 548 µA 96 459 91 453 = 250 kHz) S www.semtech.com ...
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... PCB layout considerations to be taken when using the SX8725 are relatively simple to get the highest performances out of the ZoomingADC. The most important to achieve good performances out the ZoomingADC is to have a good voltage reference. The SX8725 has already an internal reference that is good enough to get the best performances with a minimal amount of external components, but, in case an external reference is needed this one must be as clean as possible in order to get the desired performance ...
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... ADVANCED COMMUNICATIONS & SENSING Package Outline Drawing: MLPD-W-12 4x4 V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 50 SX8725 www.semtech.com ...
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... ADVANCED COMMUNICATIONS & SENSING Land Pattern Drawing: MLPD-W-12 4x4 V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing 51 SX8725 www.semtech.com ...
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... SX8725 QTY per Reel 3000 3000 3000 3000 3000 500/3000 3000 3000 3000 3000 3000 3000 ...
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... Contact Information Advanced Communication and Sensing Products Division V1.5 © 2007 Semtech Corp. ZoomingADC™ for Pressure and Temperature Sensing Semtech Corporation 200 Flynn Road, Camarillo, CA 93012 Phone (805) 498-2111 Fax : (805) 498-3804 53 SX8725 www.semtech.com ...