ADC0848BCV

ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 ADC0844/ADC0848 8-Bit μP Compatible A/D Converters with Multiplexer Options Check for Samples: ADC0844, ADC0848 FEATURES DESCRIPTION • • The ADC0844 and ADC0848 are CMOS 8-bit successive approximation A/D converters with versatile analog input multiplexers. The 4-channel or 8-channel multiplexers can be software configured for single-ended, differential or pseudo-differential modes of operation. 1 2 • • • • • • Easy Interface to All Microprocessors Operates Ratiometrically or with 5 VDC Voltage Reference No Zero or Full-Scale Adjust Required 4-Channel or 8-Channel Multiplexer with Address Logic Internal Clock 0V to 5V Input Range with Single 5V Power Supply Standard Width 20-Pin or 24-Pin PDIP 28 Pin PLCC Package KEY SPECIFICATIONS • • • • • Resolution: 8 Bits Total Unadjusted Error: ±½ LSB and ± 1 LSB Single Supply: 5 VDC Low Power: 15 mW Conversion Time: 40 μs The differential mode provides low frequency input common mode rejection and allows offsetting the analog range of the converter. In addition, the A/D's reference can be adjusted enabling the conversion of reduced analog ranges with 8-bit resolution. The A/Ds are designed to operate from the control bus of a wide variety of microprocessors. TRI-STATE output latches that directly drive the data bus permit the A/Ds to be configured as memory locations or I/O devices to the microprocessor with no interface logic necessary. Block Diagram * ADC0848 shown in PDIP Package CH5-CH8 not included on the ADC0844 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 1999–2013, Texas Instruments Incorporated ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Connection Diagram Figure 1. PLCC Package (Top View) Figure 2. 20-Pin PDIP (Top View) Figure 3. 28-Pin PDIP (Top View) These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) (3) Supply Voltage (VCC) 6.5V −0.3V to +15V Logic Control Inputs Voltage −0.3V to VCC+0.3V At Other Inputs and Outputs Input Current at Any Pin (4) Package Input Current 5 mA (4) 20 mA −65°C to +150°C Storage Temperature Package Dissipation at TA=25°C ESD Susceptibility 875 mW (5) 800V PDIP Package Lead Temperature (Soldering, 10 seconds) (1) (2) (3) (4) (5) 2 PLCC Package 260°C Vapor Phase (60 seconds) 215°C Infrared (15 seconds) 220°C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its specified operating conditions. All voltages are measured with respect to the ground pins. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. When the input voltage (VIN) at any pin exceeds the power supply rails (VIN < V−or VIN > V+) the absolute value of the current at that pin should be limited to 5 mA or less. The 20 mA package input current limits the number of pins that can exceed the power supply boundaries with a 5 mA current limit to four. Human body model, 100 pF discharged through a 1.5 kΩ resistor. Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 Operating Conditions (1) (2) Supply Voltage (VCC) 4.5 VDC to 6.0 VDC 0°C≤TA≤70°C ADC0844CCN, ADC0848BCN, ADC0848CCN Temperature Range (TMIN≤TA≤TMAX) (1) (2) (3) ADC0844BCJ (3), ADC0844CCJ (3), ADC0848BCV, ADC0848CCV −40°C≤TA≤85°C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its specified operating conditions. All voltages are measured with respect to the ground pins. Product/package combination obsolete; shown for reference only. Electrical Characteristics The following specifications apply for VCC = 5 VDC unless otherwise specified. Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25°C. Parameter Conditions ADC0844CCN, ADC0848BCN, ADC0848CCN, ADC0848BCV, ADC0848CCV ADC0844BCJ (1) ADC0844CCJ (1) Typ (2) Tested Design Limit (3) Limit (4) Typ (2) Limit Units Tested Design Limit (3) Limit (4) CONVERTER AND MULTIPLEXER CHARACTERISTICS Maximum Total ADC0844BCN, ADC0848BCN, BCV Unadjusted Error ADC0844CCN, ADC0848CCN, CCV ±½ ±½ LSB ±1 ±1 LSB VREF = 5.00 VDC (5) ADC0844CCJ (1) ±1 LSB Minimum Reference Input Resistance 2.4 1.1 2.4 1.2 1.1 kΩ Maximum Reference Input Resistance 2.4 5.9 2.4 5.4 5.9 kΩ VCC + 0.05 VCC + 0.05 V GND − 0.05 GND − 0.05 V Maximum Common-Mode Input Voltage See (6) VCC + 0.05 Minimum Common-Mode Input Voltage See (6) GND − 0.05 DC Common-Mode Error Differential Mode ±1/16 ±¼ ±1/16 ±¼ ±¼ LSB Power Supply Sensitivity VCC = 5V±5% ±1/16 ±⅛ ±1/16 ±⅛ ±⅛ LSB Off Channel Leakage Current On Channel = 5V, Off Channel = 0V (7) −1 −0.1 −1 μA On Channel = 0V, Off Channel = 5V 1 0.1 1 μA 2.0 2.0 2.0 V 0.8 DIGITAL AND DC CHARACTERISTICS VIN(1), Logical “1” Input Voltage (Min) VCC = 5.25V VIN(0), Logical “0” Input Voltage (Max) VCC = 4.75V 0.8 V IIN(1), Logical “1” Input Current (Max) VIN = 5.0V 0.005 1 0.005 1 μA IIN(0), Logical “0” Input Current (Max) VIN = 0V −0.005 −1 −0.005 −1 μA (1) (2) (3) (4) (5) (6) (7) 0.8 This product/package combination is obsolete. Shown for reference only. Typical figures are at 25°C and represent most likely parametric norm. Tested limits are specified to TI's AOQL (Average Outgoing Quality Level). Design limits are specified by not 100% tested. These limits are not used to calculate outgoing quality levels. Total unadjusted error includes offset, full-scale, linearity, and multiplexer error. For VIN (−) ≥ VIN(+) the digital output code will be 0000 0000. Two on-chip diodes are tied to each analog input, which will forwardconduct for analog input voltages one diode drop below ground or one diode drop greater than VCC supply. Be careful during testing at low VCC levels (4.5V), as high level analog inputs (5V) can cause this input diode to conduct, especially at elevated temperatures, and cause errors for analog inputs near full-scale. The spec allows 50 mV forward bias of either diode. This means that as long as the analog VIN does not exceed the supply voltage by more than 50 mV, the output code will be correct. To achieve an absolute 0 VDC to 5 VDC input voltage range will therefore require a minimum supply voltage of 4.950 VDC over temperature variations, initial tolerance and loading. Off channel leakage current is measured after the channel selection. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 3 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Electrical Characteristics (continued) The following specifications apply for VCC = 5 VDC unless otherwise specified. Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25°C. Parameter Conditions Typ (2) VOUT(1), Logical “1” Output Voltage (Min) VOUT(0), Logical “0” Output Voltage (Max) ADC0844CCN, ADC0848BCN, ADC0848CCN, ADC0848BCV, ADC0848CCV ADC0844BCJ (1) ADC0844CCJ (1) Tested Design Limit (3) Limit (4) Limit Units Tested Design Limit (3) Limit (4) Typ (2) VCC = 4.75V, IOUT = −360 μA 2.4 2.8 2.4 V IOUT = −10 μA 4.5 4.6 4.5 V VCC = 4.75V, IOUT = 1.6 mA 0.4 0.34 0.4 V μA VOUT = 0V −0.01 −3 −0.01 −0.3 −3 VOUT = 5V 0.01 3 0.01 0.3 3 μA ISOURCE, Output Source Current (Min) VOUT = 0V −14 −6.5 −14 −7.5 −6.5 mA ISINK, Output Sink Current (Min) VOUT = VCC 16 8.0 16 9.0 8.0 mA ICC, Supply Current (Max) CS = 1, VREF Open 1 2.5 1 2.3 2.5 mA IOUT, TRI-STATE Output Current (Max) AC Electrical Characteristics The following specifications apply for VCC = 5VDC, tr = tf = 10 ns unless otherwise specified. Boldface limits apply from TMIN to TMAX; all other limits TA = Tj = 25°C. Parameter Typ (1) Conditions tC, Maximum Conversion Time (See Figure 7) Tested Limit (2) Design Limit (3) Units 60 μs 30 40 tW(WR), Minimum WR Pulse Width See (4) 50 150 tACC, Maximum Access Time (Delay from Falling Edge of RD to Output Data Valid) CL = 100 pF (4) 145 225 ns t1H, t0H, TRI-STATE Control (Maximum Delay from Rising Edge of RD to Hi-Z State) CL = 10 pF, RL = 10k (4) 125 200 ns tWI, tRI, Maximum Delay from Falling Edge of WR or RD to Reset of INTR tDS, Minimum Data Set-Up Time See (4) ns 200 400 ns 50 100 ns tDH, Minimum Data Hold Time 0 50 ns CIN, Capacitance of Logic Inputs 5 pF COUT, Capacitance of Logic Outputs 5 pF (1) (2) (3) (4) 4 Typical figures are at 25°C and represent most likely parametric norm. Tested limits are specified to TI's AOQL (Average Outgoing Quality Level). Design limits are specified by not 100% tested. These limits are not used to calculate outgoing quality levels. The temperature coefficient is 0.3%/°C. Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 Typical Performance Characteristics Logic Input Threshold Voltage vs. Supply Voltage Output Current vs. Temperature Figure 4. Figure 5. Power Supply Current vs. Temperature Linearity Error vs. VREF Figure 6. Figure 7. Conversion Time vs. VSUPPLY Conversion Time vs.Temperature Figure 8. Figure 9. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 5 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unadjusted Offset Error vs. VREF Voltage Figure 10. TRI-STATE Test Circuits and Waveforms t1H t1H, CL = 10 pF t0H t0H, CL = 10 pF tr = 20 ns Leakage Current Test Circuit 6 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 Timing Diagrams Read strobe must occur at least 600 ns after the assertion of interrupt to ensure reset of INTR . MA stands for MUX address. Figure 11. Using the Previously Selected Channel Configuration and Starting a Conversion Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 7 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com ADC0848 Functional Block Diagram 8 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 Functional Description The ADC0844 and ADC0848 contain a 4-channel and 8-channel analog input multiplexer (MUX) respectively. Each MUX can be configured into one of three modes of operation differential, pseudo-differential, and single ended. These modes are discussed in Applications Information. The specific mode is selected by loading the MUX address latch with the proper address (see Table 1 and Table 2). Inputs to the MUX address latch (MA0MA4) are common with data bus lines (DB0-DB4) and are enabled when the RD line is high. A conversion is initiated via the CS and WR lines. If the data from a previous conversion is not read, the INTR line will be low. The falling edge of WR will reset the INTR line high and ready the A/D for a conversion cycle. The rising edge of WR, with RD high, strobes the data on the MA0/DB0-MA4/DB4 inputs into the MUX address latch to select a new input configuration and start a conversion. If the RD line is held low during the entire low period of WR the previous MUX configuration is retained, and the data of the previous conversion is the output on lines DB0-DB7. After the conversion cycle (tC ≤ 40 μs), which is set by the internal clock frequency, the digital data is transferred to the output latch and the INTR is asserted low. Taking CS and RD low resets INTR output high and outputs the conversion result on the data lines (DB0-DB7). APPLICATIONS INFORMATION MULTIPLEXER CONFIGURATION The design of these converters utilizes a sampled-data comparator structure which allows a differential analog input to be converted by a successive approximation routine. The actual voltage converted is always the difference between an assigned “+” input terminal and a “−” input terminal. The polarity of each input terminal of the pair being converted indicates which line the converter expects to be the most positive. If the assigned “+” input is less than the “−” input the converter responds with an all zeros output code. A unique input multiplexing scheme has been utilized to provide multiple analog channels. The input channels can be software configured into three modes: differential, single ended, or pseudo-differential. Figure 12 shows the three modes using the 4-channel MUX ADC0844. The eight inputs of the ADC0848 can also be configured in any of the three modes. In the differential mode, the ADC0844 channel inputs are grouped in pairs, CH1 with CH2 and CH3 with CH4. The polarity assignment of each channel in the pair is interchangeable. The singleended mode has CH1–CH4 assigned as the positive input with the negative input being the analog ground (AGND) of the device. Finally, in the pseudo-differential mode CH1–CH3 are positive inputs referenced to CH4 which is now a pseudo-ground. This pseudo-ground input can be set to any potential within the input commonmode range of the converter. The analog signal conditioning required in transducer-based data acquisition systems is significantly simplified with this type of input flexibility. One converter package can now handle ground referenced inputs and true differential inputs as well as signals with some arbitrary reference voltage. The analog input voltages for each channel can range from 50 mV below ground to 50 mV above VCC (typically 5V) without degrading conversion accuracy. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 9 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Table 1. ADC0844 MUX ADDRESSING (1) MUX Address CS RD MA2 MA1 X L L L L X L L H L X L H L L X L H H L L H L L L L H L H L L H H L L H (1) MA0 WR MA3 NP CH2 CH3 CH4 H + − H − H + + − H − + H NP L H H H L H H L L L H H H L H L H H H L L X X X X L H L MUX Mode Differential − + − + + Single-Ended − − + − + H NP AGND − + H H NP Channel# CH1 + Pseudo- Differential − Previous Channel Configuration X = don't care, NP = negative pulse 4 Single-Ended 2 Differential 3 Pseudo-Differential Combined Figure 12. Analog Input Multiplexer Options REFERENCE CONSIDERATIONS The voltage applied to the reference input of these converters defines the voltage span of the analog input (the difference between VIN(MAX) and VIN(MIN)) over which the 256 possible output codes apply. The devices can be used in either ratiometric applications or in systems requiring absolute accuracy. The reference pin must be connected to a voltage source capable of driving the minimum reference input resistance of 1.1 kΩ. This pin is the top of a resistor divider string used for the successive approximation conversion. In a ratiometric system (Figure 13), the analog input voltage is proportional to the voltage used for the A/D reference. This voltage is typically the system power supply, so the VREF pin can be tied to VCC. This technique relaxes the stability requirements of the system reference as the analog input and A/D reference move together maintaining the same output code for a given input condition. For absolute accuracy (Figure 14), where the analog input varies between very specific voltage limits, the reference pin can be biased with a time and temperature stable voltage source. The LM385 and LM336 reference diodes are good low current devices to use with these converters. The maximum value of the reference is limited to the VCC supply voltage. The minimum value, however, can be quite small (see Typical Performance Characteristics) to allow direct conversions of transducer outputs providing less than a 5V output span. Particular care must be taken with regard to noise pickup, circuit layout and system error voltage sources when operating with a reduced span due to the increased sensitivity of the converter (1 LSB equals VREF/256). 10 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 THE ANALOG INPUTS Analog Differential Voltage Inputs and Common-Mode Rejection The differential input of these converters actually reduces the effects of common-mode input noise, a signal common to both selected “+” and “−” inputs for a conversion (60 Hz is most typical). The time interval between sampling the “+” input and then the “−” inputs is ½ of a clock period. The change in the common-mode voltage during this short time interval can cause conversion errors. For a sinusoidal common-mode signal this error is: where • • • fCM is the frequency of the common-mode signal Vpeak is its peak voltage value tC is the conversion time For a 60 Hz common-mode signal to generate a ¼ LSB error (≈5 mV) with the converter running at 40 μS, its peak value would have to be 5.43V. This large a common-mode signal is much greater than that generally found in a well designed data acquisition system. Table 2. ADC0848 MUX Addressing (1) MUX Address MA3 MA2 MA1 X L L L L L X L L L H L X L L H L L X L L H H L X L H L L L X L H L H X L H H L X L H H L H L L H L L H L (1) MA0 CS MA4 WR RD Channel CH5 CH6 H + − L H − + L H + − H L H − + L L L H L H L H L H L L H H L H H L L H H L L L H L H H L H L H L H H H L L H NP NP CH1 CH2 CH3 CH4 H + − H − + H + − H − + L H H H H L H H L L L L H H H L L H L H H H L H L L H H L H H L H H H L L L H H H H L H L H H H H H L L H X X X X X L L H NP H CH8 AGND MUX Mode Differential − + − + − + H H CH7 − + − + Single-Ended − + − + + − − + − + − + − + PseudoDifferential − + − + + − Previous Channel Configuration X = don't care, NP = negative pulse Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 11 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Input Current Due to the sampling nature of the analog inputs, short duration spikes of current enter the “+” input and exit the “−” input at the clock edges during the actual conversion. These currents decay rapidly and do not cause errors as the internal comparator is strobed at the end of a clock period. Bypass capacitors at the inputs will average these currents and cause an effective DC current to flow through the output resistance of the analog signal source. Bypass capacitors should not be used if the source resistance is greater than 1 kΩ. Input Source Resistance The limitation of the input source resistance due to the DC leakage currents of the input multiplexer is important. A worst-case leakage current of ± 1 μA over temperature will create a 1 mV input error with a 1 kΩ source resistance. An op amp RC active low pass filter can provide both impedance buffering and noise filtering should a high impedance signal source be required. OPTIONAL ADJUSTMENTS Zero Error The zero of the A/D does not require adjustment. If the minimum analog input voltage value, VIN(MIN), is not ground, a zero offset can be done. The converter can be made to output 0000 0000 digital code for this minimum input voltage by biasing any VIN (−) input at this VIN(MIN) value. This is useful for either differential or pseudodifferential modes of input channel configuration. The zero error of the A/D converter relates to the location of the first riser of the transfer function and can be measured by grounding the V− input and applying a small magnitude positive voltage to the V+ input. Zero error is the difference between actual DC input voltage which is necessary to just cause an output digital code transition from 0000 0000 to 0000 0001 and the ideal ½ LSB value (½ LSB=9.8 mV for VREF=5.000 VDC). Full-Scale The full-scale adjustment can be made by applying a differential input voltage which is 1 ½ LSB down from the desired analog full-scale voltage range and then adjusting the magnitude of the VREF input for a digital output code changing from 1111 1110 to 1111 1111. Adjusting for an Arbitrary Analog Input Voltage Range If the analog zero voltage of the A/D is shifted away from ground (for example, to accommodate an analog input signal which does not go to ground), this new zero reference should be properly adjusted first. A VIN (+) voltage which equals this desired zero reference plus ½ LSB (where the LSB is calculated for the desired analog span, 1 LSB = analog span/256) is applied to selected “+” input and the zero reference voltage at the corresponding “−” input should then be adjusted to just obtain the 00HEX to 01HEX code transition. Figure 13. Referencing Examples - Ratiometric 12 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 ADC0844, ADC0848 www.ti.com SNAS523D – JUNE 1999 – REVISED MARCH 2013 Figure 14. Referencing Examples - Absolute with a Reduced Span The full-scale adjustment should be made [with the proper VIN (−) voltage applied] by forcing a voltage to the VIN (+) input which is given by: where • • VMAX = the high end of the analog input range VMIN = the low end (the offset zero) of the analog range. (Both are ground referenced.) (1) The VREF (or VCC) voltage is then adjusted to provide a code change from FEHEX to FFHEX. This completes the adjustment procedure. For an example see the Zero-Shift and Span Adjust circuit below. Figure 15. Zero-Shift and Span Adjust (2V ≤ VIN ≤ 5V) Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: ADC0844 ADC0848 Submit Documentation Feedback 13 ADC0844, ADC0848 SNAS523D – JUNE 1999 – REVISED MARCH 2013 www.ti.com Figure 16. Differential Voltage Input 9-Bit A/D Figure 17. Span Adjust (0V ≤ VIN ≤ 3V) Diodes are 1N914 DO = all 1s if VIN(+)>VIN(−) DO = all 0s if VIN(+)