CA3310E

CA3310, CA3310A UCT T PROD E T EM EN E L E PL A C t O B SO R D te E en r a ND port C O MM E p C u s S E l /t R a om c NO chnicSheet ersil.c TeData t r n u .i o w t or w w contac TERSIL IN 8 8 1-8 ® CMOS, 10-Bit, A/D Converters with Internal Track and Hold May 2001 • CMOS Low Power (Typ) . . . . . . . . . . . . . . . . . . . . . 15mW The ten data outputs feature full high-speed CMOS threestate bus driver capability, and are latched and held through a full conversion cycle. Separate 8 MSB and 2 LSB enables, a data ready flag, and conversion start and ready reset inputs complete the microprocessor interface. • Single Supply Voltage . . . . . . . . . . . . . . . . . . . . . 3V to 6V • Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13µs • Built-In Track and Hold • Rail-to-Rail Input Range • Latched Three-state Output Drivers • Microprocessor-Compatible Control Lines • Internal or External Clock Applications • Fast, No-Droop, Sample and Hold An internal, adjustable clock is provided and is available as an output. The clock may also be driven from an external source. • Voice Grade Digital Audio Part Number Information • µP Controlled Systems LINEARITY (INL, DNL) TEMP. RANGE (oC) CA3310E ±0.75 LSB -40 to 85 24 Ld PDIP E24.6 CA3310M ±0.75 LSB -40 to 85 24 Ld SOIC M24.3 CA3310AM ±0.5 LSB -40 to 85 24 Ld SOIC M24.3 1 PACKAGE 3095.3 Features The Intersil CA3310 is a fast, low power, 10-bit successive approximation analog-to-digital converter, with microprocessor-compatible outputs. It uses only a single 3V to 6V supply and typically draws just 3mA when operating at 5V. It can accept full rail-to-rail input signals, and features a built-in track and hold. The track and hold will follow high bandwidth input signals, as it has only a 100ns (typical) input time constant. PART NUMBER File Number PKG. NO. • DSP Modems • Remote Low Power Data Acquisition Systems Related Literature • Technical Brief TB363 “Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)” Pinout CA3310, CA3310A (PDIP, SOIC) TOP VIEW D0 (LSB) 1 24 D1 2 23 VIN D2 3 22 VREF + D3 4 21 REXT D4 5 20 CLK D5 6 19 STRT D6 7 18 VREF - D7 8 17 VAA+ VDD D8 9 16 VAA- D9 (MSB) 10 15 OEL DRDY 11 14 OEM VSS (GND) 12 13 DRST CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2002. All Rights Reserved CA3310, CA3310A Functional Block Diagram STRT VDD VSS ALL LOGIC REXT CLOCK CONTROL AND TIMING VIN VREF + CLK DRDY Q CLK CLR DRST OEM 16C D9 (MSB) 8C 50ÞΩ SUBSTRATE RESISTANCE D8 4C D7 2C D6 VAA + C 32 C 31 16C VAA - 8C 10-BIT SUCCESSIVE APPROXIMATION REGISTER 10-BIT EDGE TRIGGERED “D” LATCH D5 D4 D3 4C D2 2C D1 C D0 (LSB) C OEL VREF - 2 CA3310, CA3310A Typical Application Schematics +5V SUPPLY 4.7µF TAN + 0.1µF CER A 8 ICL7663S 3 100Ω ±10% 4.5V 1 75V 6 4 D VDD VREF + 4.7µF + TAN STRT START CONVERSATION DRST RESET FLAG A 5K ADJUST GAIN VAA + 28.7K VREF - 5 HIGH BYTE ENABLE OEL LOW BYTE ENABLE CA3310/A D0 - D9 A A A OEM OUTPUT DATA VAA R3 R2 +8V TO +15V 100 0.1 A R1 8 + VIN A 7 3 + 2 CA3140 - - R4 10K 4 A CLK VDD REXT VIN R5 2MHz CLOCK NC VSS UNLESS NOTED, ALL RESISTORS = 1% METAL FILM, POTS = 10 TURN, CERMET 47pF 1 D ADJUST OFFSET 0.1 -1V TO -15V OPTIONAL CLAMP 6 5 DATA READY FLAG DRDY A A D = DIGITAL GROUND A = ANALOG GROUND D 100 INPUT RANGE R1 R2 R3 R4 R5 0V To 2.5V 4.99K 9.09K OPEN 4.99K 9.09K 0V To 5V 4.99K 4.53K OPEN 4.99K 4.53K 0V To 10V 10K 4.53K OPEN 10K 4.53K -2.5V To +2.5V 4.99K 9.09K 9.09K 4.99K 4.53K -5V To +5V 10K 9.09K 9.09K 10K 4.53K 3 CA3310, CA3310A Absolute Maximum Ratings Thermal Information Digital Supply Voltage VDD . . . . . . . . . . . . . . VSS -0.5V to V SS +7V Analog Supply Voltage (V AA+) . . . . . . . . . . . . . . . . . . . . VDD ±0.5V Any Other Terminal . . . . . . . . . . . . . . . . VSS -0.5V to VDD + 0.5V DC Input Current or Output (Protection Diode) Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±20mA DC Output Drain Current, per Output . . . . . . . . . . . . . . . . . . ±35mA Total DC Supply or Ground Current. . . . . . . . . . . . . . . . . . . . ±70mA Thermal Resistance (Typical, Note 1) Operating Conditions θJA ( oC/W) PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Maximum Junction Temperature Plastic Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150oC Maximum Storage Temperature (TSTG) . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC (SOIC - Lead Tips Only) Temperature Range (TA) . . . . . . . . . . . . . . . . . . . . . . -40oC to 85oC CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTE: 1. θJA is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details. TA = 25×oC, VDD = VAA+ = 5V, VREF + = 4.608V, VSS = VAA- = VREF - = GND, CLK = External 1MHz, Unless Otherwise Specified Electrical Specifications PARAMETER TEST CONDITIONS MIN TYP MAX UNITS ACCURACY (See Text For Definitions) Resolution Differential Linearity Error Integral Linearity Error Gain Error Offset Error 10 - - Bits CA3310 - ±0.5 ±0.75 LSB CA3310A - ±0.25 ±0.5 LSB CA3310 - ±0.5 ±0.75 LSB CA3310A - ±0.25 ±0.5 LSB CA3310 - ±0.25 ±0.5 LSB CA3310A - - ±0.25 LSB CA3310 - ±0.25 ±0.5 LSB CA3310A - - ±0.25 LSB - 330 - Ω ANALOG INPUT Input Resistance In Series with Input Sample Capacitors Input Capacitance During Sample State - 300 - pF Input Capacitance During Hold State - 20 - pF Input Current At VIN = VREF + = 5V - - +300 µA At VIN = VREF - = 0V - - -100 µA Static Input Current STRT = V+, CLK = V+ At VIN = VREF + = 5V - - 1 µA - - -1 µA (Note 3) VREF - +1 - VDD +0.3 V Input - Full-Scale Range (Note 3) V SS -0.3 - VREF + -1 V Input Bandwidth From Input RC Time Constant - 1.5 - MHz At VIN = VREF - = 0V Input + Full-Scale Range DIGITAL INPUTS DRST, OEL, OEM, STRT, CLK High-Level Input Voltage Over V DD = 3V to 6V (Note 3) 70 - - % of VDD Low-Level Input Voltage Over V DD = 3V to 6V (Note 3) - - 30 % of VDD Input Leakage Current Except CLK - - ±1 µA Input Capacitance (Note 3) - - 10 pF Input Current CLK Only (Note 3) - - ±400 µA High-Level Output Voltage ISOURCE = -4mA 4.6 - - V Low-Level Output Voltage ISINK = 6mA - - 0.4 V Three-State Leakage Except DRDY - - ±1 µA Output Capacitance Except DRDY (Note 3) - - 20 pF DIGITAL OUTPUTS D0 - D9, DRDY 4 CA3310, CA3310A TA = 25×oC, VDD = VAA+ = 5V, VREF + = 4.608V, VSS = VAA- = VREF - = GND, CLK = External 1MHz, Unless Otherwise Specified (Continued) Electrical Specifications PARAMETER TEST CONDITIONS MIN TYP MAX UNITS CLK OUTPUT High-Level Output Voltage ISOURCE = 100µA (Note 3) 4 - - V Low-Level Output Voltage ISlNK = 100µA (Note 3) - - 1 V 200 300 400 kHz 600 800 1000 kHz - 4 2 MHz TIMING Internal, CLK and R EXT Open Clock Frequency Internal, CLK Shorted to REXT External, Applied to CLK (Note 3) (Max) 100 10 - kHz Clock Pulse Width, tLOW , tHIGH External, Applied to CLK: See Figure 1 (Note 3) (Min) 100 - - ns Conversion Time Internal, CLK Shorted to REXT 13 - - µs Aperture Delay, tD APR See Figure 1 - 100 - ns Clock to Data Ready Delay, tD1 DRDY See Figure 1 - 150 - ns Clock to Data Ready Delay, tD2 DRDY See Figure 1 - 250 - ns Clock to Data Delay, tD Data See Figure 1 - 200 - ns Start Removal Time, tR STRT See Figures 3 and 4 (Note 2) - -120 - ns Start Setup Time, tSU STRT See Figure 4 - 160 - ns Start Pulse Width, tW STRT See Figures 3 and 4 - 10 - ns Start to Data Ready Delay, tD3 DRDY See Figures 3 and 4 - 170 - ns Clock Delay from Start, tD CLK See Figure 3 - 200 - ns Ready Reset Removal Time, tR DRST See Figure 5 (Note 2) - -80 - ns Ready Reset Pulse Width, tW DRST See Figure 5 - 10 - ns Ready Reset to Data Ready Delay, tD4 DRDY See Figure 5 - 35 - ns Output Enable Delay, tEN See Figure 2 - 40 - ns Output Disable Delay, tDIS See Figure 2 - 50 - ns (Note 3) 3 - 6 V SUPPLIES Supply Operating Range, VDD or VAA Supply Current, IDD + IAA See Figures 14, 15 - 3 8 mA Supply Standby Current Clock Stopped During Cycle 1 - 3.5 - mA Analog Supply Rejection At 120Hz, See Figure 13 - 25 - mV/V Reference Input Current See Figure 10 - 160 - µA Offset Drift At 0 to 1 Code Transition - -4 - µV/ oC Gain Drift At 1022 to 1023 Code Transition - -6 - µV/ oC Internal Clock Speed See Figure 7 - -0.5 - % / oC TEMPERATURE DEPENDENCY NOTES: 2. A (-) removal time means the signal can be removed after the reference signal. 3. Parameter not tested, but guaranteed by design or characterization. 5 CA3310, CA3310A Timing Diagrams 1 2 3 4 5 - 12 1 13 2 3 CLK tHIGH tD1 DRDY tLOW tD2 DRDY DRDY tD DATA DATA N DATA N - 1 D0 - D9 HOLD TRACK N + 1 TRACK N INPUT tD APR FIGURE 1. FREE RUNNING, STRT TIED LOW, DRST TIED HIGH OEL OR OEM tDIS tEN D0 - D1 OR D2- D9 OFF TO HIGH 90% 50% ZL = 50pF TO GND 1kΩ TO GND TO OUTPUT PIN OFF TO LOW 50% 10% ZL = 50pF TO GND 1kΩ TO VDD FIGURE 2. OUTPUT ENABLE/DISABLE TIMING DIAGRAM 13 1 2 3 4 5 CLK (INTERNAL) tD CLK tR STRT tW STRT DON’T CARE STRT tD3 DRDY DRDY HOLD INPUT HOLD TRACK FIGURE 3. STRT PULSED LOW, DRST TIED HIGH, INTERNAL CLOCK 6 CA3310, CA3310A Timing Diagrams (Continued) 13 1 2 2 2 3 4 5 CLK (EXTERNAL) tSU STRT tR STRT tW STRT DON’T CARE STRT tD3 DRDY DRDY HOLD HOLD TRACK INPUT FIGURE 4. STRT PULSED LOW, DRST TIED HIGH, EXTERNAL CLOCK 13 1 CLK (INTERNAL OR EXTERNAL) DON’T CARE tR DRST tW DRST DRST tD4 DRDY DRDY FIGURE 5. DRST PULSED LOW, STRT TIED HIGH 800 VDD = 3V - 6V = VAA+ CLOCK FREQUENCY (kHz) 700 5V 600 VDD = 6V 4V 500 400 3V 300 200 100 0 SHORT 10 100 1000 OPEN EXTERNAL RESISTANCE (kΩ) FIGURE 6. INTERNAL CLOCK FREQUENCY vs EXTERNAL RESISTANCE 7 CLOCK FREQUENCY NORMALIZED TO +5V, 25oC OPERATION, REXT = OPEN Typical Performances Curves 5 4 3 VDD = VAA+ = 3V - 6V VDD = 6V INTERNAL CLOCK MAY NOT WORK AT VDD < 4V FOR TEMPERATURE < -40oC REXT = SHORTED REXT = OPEN 5V 4V 6V 2 5V 3V 1 4V 3V 0 -55 -40 0 25 85 125 TEMPERATURE (oC) FIGURE 7. INTERNAL CLOCK FREQUENCY vs TEMPERATURE AND SUPPLY VOLTAGE CA3310, CA3310A Typical Performances Curves (Continued) +80 VAA+ = 6V +40 (+) IPEAK +20 5V 4V 3V 0 6V -20 VAA+ = 3 - 6V VAA+ = VDD = VREF+ CLOCK = INTERNAL, FREE RUNNING +50 PEAK INPUT CURRENT (mA) +60 PEAK INPUT CURRENT (mA) +60 VAA + = 3 - 6V VAA + = VDD = VREF + +40 +30 3V +20 4V +10 0 5V -10 (-) IPEAK -40 VAA = 6V -20 0 1 2 3 4 5 6 0 7 1 2 3 FIGURE 8. PEAK INPUT CURRENT vs INPUT VOLTAGE 5 6 7 8 9 10 FIGURE 9. AVERAGE INPUT CURRENT vs INPUT VOLTAGE 40 VAA+ = VDD = VREF+ CLOCK INTERNAL, FREE RUNNING 30 IPEAK 20 40 20 10 NORMALIZED ERROR 60 IAVE VREF+ CURRENT PEAK (mA) VREF+ CURRENT AVERAGE (mA) 80 5 GAIN 4 3 OFFSET 2 DLE 1 ILE 0 0 0 1 2 3 4 5 6 VREF + VOLTAGE (V) 7 8 0 9 SENSITIVITY, REFERRED TO INPUT (mV/V) 7 6 5 ILE 4 DLE OFFSET 2 1 GAIN 0 0.1 1 2 3 4 5 CLOCK FREQUENCY (MHz) FIGURE 12. NORMALIZED GAIN, OFFSET, INTEGRAL AND DIFFERENTIAL LINEARITY ERRORS vs CLOCK SPEED 8 2 3 4 5 FIGURE 11. NORMALIZED GAIN, OFFSET, INTEGRAL AND DIFFERENTIAL LINEARITY ERRORS vs REFERENCE VOLTAGE 8 3 1 REFERENCE VOLTAGE (V) FIGURE 10. V REF+ CURRENT vs VREF+ VOLTAGE NORMALIZED ERROR 4 INPUT VOLTAGE (V) INPUT VOLTAGE (V) 1000 VDD = VAA = VREF + = 5V fCLOCK = 1MHz VIN = (+) FULL SCALE 100 VIN = (-) FULL SCALE 10 100 1000 10,000 VAA , RIPPLE FREQUENCY (Hz) FIGURE 13. V AA SUPPLY SENSITIVITY 100,000 CA3310, CA3310A Typical Performances Curves (Continued) 8 VDD = 3-6V VDD = VAA = VREF = 3 - 6V LOAD = 50pF/OUTPUT CONTINUOUS CONVERSIONS 10 8 6V 6 4 5V 2 7 SUPPLY CURRENT (IDD +IAA) (mA) SUPPLY CURRENT IDD +IAA (mA) 12 4V AND REXT = OPEN OR SHORTED. CLOCK = INTERNAL, FREE RUNNING VDD = VAA+ 6 VDD = 6V, REXT = SHORT 5 4 5V, OPEN 5V, SHORT VDD = 6V, REXT = OPEN 3 4V, OPEN 2 1 0 0.5 1.0 1.5 2.0 2.5 3.0 0 3.5 3V, SHORT 3V, OPEN 3V 0 4V, SHORT -50 -40 0 25 85 125 TEMPERATURE (oC) CLOCK FREQUENCY (MHz) FIGURE 14. SUPPLY CURRENT vs CLOCK FREQUENCY FIGURE 15. SUPPLY CURRENT vs TEMPERATURE TABLE 1. PIN DESCRIPTIONS PIN NUMBER NAME DESCRIPTION Three-State outputs for data bits representing 20 (LSB) through 29 (MSB). 1-10 D0 - D9 11 DRDY 12 VSS 13 DRST Active low input, resets DRDY. 14 OEM Active low input, three-state enable of D2 - D9. 15 OEL Active low input, three-state enable of D0, D1. 16 VAA- Analog Ground. Output flag signifying new data is available. Goes high at end of clock period 13, goes low when new conversion started. Also reset asynchronously by DRST. Digital Ground. 17 VAA+ Analog + Supply. 18 VREF - Reference input voltage, sets 0 code (-) end of input range. 19 STRT Active Low Start Conversion Input. Recognized after end of clock period 13. 20 CLK Clock input or output. Conversion functions are synchronous to high-going edge. 21 R EXT Clock adjust input when using internal clock. 22 V REF + Reference input voltage, set 1023 code (+) end of input range. 23 V lN Analog Input. 24 VDD Digital + Supply. TABLE 2. OUTPUT CODES CODE DESCRIPTION BINARY OUTPUT CODE INPUT VOLTAGE (NOTE 4) ( VREF+ – V REF- ) = 4.608V MSB (V) D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 DECIMAL COUNT Zero 0.000 0 0 0 0 0 0 0 0 0 0 0 ( V R EF+ – V R EF- ) LSB = ---------------------------------------------1024 LSB 1 LSB 0.0045 0 0 0 0 0 0 0 0 0 1 1 1/ (V 4 REF+ - VREF -) 1/ (V 2 REF+ - VREF -) 3/ (V 4 REF+ - VREF -) 1.152 0 1 0 0 0 0 0 0 0 0 256 2.304 1 0 0 0 0 0 0 0 0 0 512 3.456 1 1 0 0 0 0 0 0 0 0 768 (VREF+ - VREF -) - 1 LSB 4.6035 1 1 1 1 1 1 1 1 1 1 1023 NOTE: 4. The voltages listed above are the ideal centers of each output code shown as a function of its associated reference voltage. 9 CA3310, CA3310A Device Operation The CA3310 is a CMOS 10-bit, analog-to-digital converter that uses capacitor-charge balancing to successively approximate the analog input. A binarily weighted capacitor network forms the D-to-A “Heart” of the device. See the Functional Diagram of the CA3310. The capacitor network has a common node which is connected to a comparator. The second terminal of each capacitor is individually switchable to the input, VREF+ or VREF -. During the first three clock periods of a conversion cycle, the switchable end of every capacitor is connected to the input. The comparator is being auto-balanced at its trip point, thus setting the voltage at the capacitor common node. During the fourth period, all capacitors are disconnected from the input, the one representing the MSB (D9) is connected to the VREF + terminal, and the remaining capacitors to V REF -. The capacitor-common node, after the charges balance out, will represent whether the input was above or below 1/2 of (VREF + - VREF). At the end of the fourth period, the comparator output is stored and the MSB capacitor is either left connected to VREF+ (if the comparator was high) or returned to VREF -. This allows the next comparison to be at either 3/4 or 1/4 of (VREF + - VREF -). At the end of periods 5 through 12, capacitors representing the next to MSB (D8) through the next to LSB (D1) are tested, the result stored, and each capacitor either left at VREF + or at VREF -. At the end of the 13th period, when the LSB (D0) capacitor is tested, D0 and all the previous results are shifted to the output registers and drivers. The capacitors are reconnected to the input, the comparator returns to the balance state, and the data-ready output goes active. The conversion cycle is now complete. Clock The CA3310 can operate either from its internal clock or from one externally supplied. The CLK pin functions either as the clock output or input. All converter functions are synchronous with the rising edge of the clock signal. Figure 16 shows the configuration of the internal clock. The clock output drive is low power: if used as an output, it should not have more than 1 CMOS gate load applied, and wiring capacitance should be kept to a minimum. INTERNAL ENABLE INTERNAL CLOCK CLK OPTIONAL EXTERNAL CLOCK OPTIONAL CLOCK ADJUST The REXT pin allows adjusting of the internal clock frequency by connecting a resistor between REXT and CLK. Figure 6 shows the typical relationship between the resistor and clock speed, while Figure 7 shows clock speed versus temperature and supply voltage. The internal clock will shut down if the A/D is not restarted after a conversion. This is described under Control Timing. The clock could also be shut down with an open collector driver applied to the CLK pin. This should only be done during the sample portion (the first three periods) of a conversion cycle, and might be useful for using the device as a digital sample and hold: this is described further under Applications. If an external clock is supplied to the CLK pin, it must have sufficient drive to overcome the internal clock source. The external clock can be shut off, but again only during the sample portion of a conversion cycle. At other times, it must be above the minimum frequency shown in the specifications. If the internal or external clock was shut off during the conversion time (clock cycles 4 through 13) of the A/D, the output might be invalid due to balancing capacitor droop. An external clock must also meet the minimum tLOW and tHIGH times shown in the specifications. A violation may cause an internal miscount and invalidate the results. Control Signals The CA3310 may be synchronized from an external source by using the STRT (Start Conversion) input to initiate conversions, or if STRT is tied low, may be allowed to freerun. In the free-running mode, illustrated in Figure 1, each conversion takes 13 clock periods. The input is tracked from clock period 1 through period 3, then disconnected as the successive approximation takes place. After the start of the next period 1 (specified by TD data), the output is updated. The DRDY (Data Ready) status output goes high (specified by tD1 DRDY) after the start of clock period 1, and returns low (specified by tD2 DRDY) after the start of clock period 2. DRDY may also be asynchronously reset by a low on DRST (to be discussed later). If the output data is to be latched externally by the DRDY signal, the trailing edge of DRDY should be used: there is no guaranteed set-up time to the leading edge. The 10 output data bits are available in parallel on three- state bus driver outputs. When low, the OEM input enables the most significant byte (D2 through D9) while the OEL input enables the two least significant bits (D0, D1). tEN and tDIS specify the output enable and disable times, respectively. See Figure 2. When the STRT input is used to initiate conversions, operation is slightly different depending on whether an internal or external clock is used. 100K REXT 50K FIGURE 16. CLOCK CIRCUITRY 10 18pF Figure 3 illustrates operation with an internal clock. If the STRT signal is removed (at least tR STRT) before clock CA3310, CA3310A period 1, and is not reapplied during that period, the clock will shut off after entering period 2. The input will continue to track the DRDY output will remain high during this time. A low signal applied to STRT (at least tW STRT wide) can now initiate a new conversion. The STRT signal (after a delay of tD3 DRDY) will cause the DRDY flag to drop, and (after a delay of tD CLK) cause the clock to restart. Depending on how long the clock was shut off, the low portion of clock period 2 may be longer than during the remaining cycles. The input will continue to track until the end of period 3, the same as when free-running. Figure 4 illustrates the same operation as above, but with an external clock. If STRT is removed (at least tR STRT) before clock period 1, and not reapplied during that period, the clock will continue to cycle in period 2. A low signal applied to STRT will drop the DRDY flag as before, and with the first positive-going clock edge that meets the tSU STRT set-up time, the converter will continue with clock period 3. The DRDY flag output, as described previously, goes active at the start of period 1, and drops at the start of period 2 or upon a new STRT command, whichever is later. It may also be controlled with the DRST (Data Ready Reset) input. Figure 5 depicts this operation. DRST must be removed (at least tR DRST) before the start of period 1 to allow DRDY to go high. A low level on DRST (at least tW DRST wide) will (after a delay of tD4 DRDY) drop DRDY. Analog Input The analog input pin is a predominantly capacitive load that changes between the track and hold periods of a conversion cycle. During hold, clock period 4 through 13, the input loading is leakage and stray capacitance, typically less than 0.1µA and 20pF. At the start of input tracking, clock period 1, some charge is dumped back to the input pin. The input source must have low enough impedance to dissipate the charge by the end of the tracking period. The amount of charge is dependent on supply and input voltages. Figure 8 shows typical peak input currents for various supply and input voltages, while Figure 9 shows typical average input currents. The average current is also proportional to clock frequency, and should be scaled accordingly. During tracking, the input appears as approximately a 300pF capacitor in series with 330Ω, for a 100ns time constant. A full-scale input swing would settle to 1/2 LSB (1/2048) in 7RC time constants. Doing continuous conversions with a 1MHz clock provides 3µs of tracking time, so up to 1kΩ of external source impedance (400ns time constant) would allow proper settling of a step input. If the clock was slower, or the converter was not restarted immediately (causing a longer sample lime), a higher source impedance could be used. 11 The CA3310s low-input time constant also allows good tracking of dynamic input waveforms. The sampling rate with a 1MHz clock is approximately 80kHz. A Nyquist rate (fSAMPLE/2) input sine wave of 40kHz would have negligible attenuation and a phase lag of only 1.5 degrees. Accuracy Specifications The CA3310 accepts an analog input between the values of VREF - and VREF +, and quantizes it into one of 210 or 1024 output codes. Each code should exist as the input is varied through a range of 1/1024 x (VREF+ - VREF -), referred to as 1 LSB of input voltage. A differential Iinearity error, illustrated in Figure 17, occurs if an output code occurs over other than the ideal (1 LSB) input range. Note that as long as the error does not reach -1 LSB, the converter will not miss any codes. UNIFORM TRANSFER CURVE A B OUTPUT CODE C ACTUAL TRANSFER CURVE A = IDEAL 1 LSB STEP B-A = + DIFFERENTIAL LINEARITY ERROR A-C = - DIFFERENTIAL LINEARITY ERROR INPUT VOLTAGE FIGURE 17. DIFFERENTIAL LINEARITY ERROR The CA3310 output should change from a code of 00016 to 001 16 at an input voltage of (V REF - +1 LSB). It should also change from a code of 3FE16 to 3FF16 at an input of (VREF + -1 LSB). Any differences between the actual and expected input voltages that cause these transitions are the offset and gain errors, respectively. Figure 18 illustrates these errors. As the input voltage is increased linearly from the point that causes the 00016 to 00116 transition to the point that causes the 3FE16 to 3FF16 transition, the output code should also increase linearly. Any deviation from this input-to-output correspondence is integral linearity error, illustrated in Figure 19. Note that the integral linearity is referenced to a straight line drawn through the actual end points, not the ideal end points. For absolute accuracy to be equal to the integral linearity, the gain and offset would have to be adjusted to ideal. Offset and Gain Adjustments The VREF + and VREF - pins, references for the two ends of the analog input range, are the only means of doing offset or CA3310, CA3310A There are current pulses that occur, however, during the successive approximation part of a conversion cycle, as the charge-balancing capacitors are switched between VREF - and VREF +. For that reason, VREF - and VREF + should be well bypassed. Figure 10 shows peak and average VREF + current. gain adjustments. In a typical system, the VREF - might be returned to a clean ground, and offset adjustment done on an input amplifier. VREF + would then be adjusted for gain. VREF - could be raised from ground to adjust offset or to accommodate an input source that can’t drive down to ground. 3FF EXPECTED TRANSFER CURVE OUTPUT CODE (HEX) 3FE OFFSET ERROR GAIN ERROR 002 ACTUAL TRANSFER CURVE 001 000 0 1 2 1022 1023 1 1024 1024 1024 1024 INPUT VOLTAGE AS A FRACTION OF (VREF + - VREF -) FIGURE 18. GAIN AND OFFSET ERROR 3FF 3FE ACTUAL TRANSFER CURVE IDEAL TRANSFER CURVE OUTPUT CODE (HEX) INTEGRAL LINEARITY ERROR 001 000 OFFSET POINT INPUT VOLTAGE GAIN POINT FIGURE 19. NORMALIZED GAIN, OFFSET, INTEGRAL AND DIFFERENTIAL LINEARITY ERRORS vs REFERENCE VOLTAGE 12 CA3310, CA3310A Application Circuits Other Accuracy Effects Linearity, offset, and gain errors are dependent on the magnitude of the full-scale input range, V REF + - VREF -. Figure 11 shows how these errors vary with full-scale range. The clocking speed is a second factor that affects conversion accuracy. Figure 12 shows the typical variation of linearity, offset, and gain errors versus clocking speed. Gain and offset drift due to temperature are kept very low by means of auto-balancing the comparator. The specifications show typical offset and gain dependency on temperature. There is also very little linearity change with temperature, only that caused by the slight slowing of CMOS with increasing temperature. At 85oC, for instance, the lLE and DLE would be typically those for a 20% faster clock than at 25oC. Power Supplies and Grounding VDD (+) and VSS(GND) are the digital supply pins: they operate all internal logic and the output drivers. Because the output drivers can cause fast current spikes in the V DD and VSS lines, VSS should have a low impedance path to digital ground and VDD should be well bypassed. Except for VDD +, which is a substrate connection to VDD , all pins have protection diodes connected to VDD and VSS : input transients above VDD or below VSS will get steered to the digital supplies. Current on these pins must be limited by external means to the values specified under maximum ratings. The VAA + and VAA - terminals supply the charge-balancing comparator only. Because the comparator is autobalanced between conversions, it has good low frequency supply rejection. It does not reject well at high frequencies, however: VAA - should be returned to a clean analog ground, and VAA + should be RC decoupled from the digital supply. There is approximately 50ÞΩ of substrate impedance between V DD and VAA +. This can be used, for example, as part of a low-pass RC filter to attenuate switching supply noise. A 10pF capacitor from VAA + to ground would attenuate 30kHz noise by approximately 40dB. Note that back-to-back diodes should be placed from VDD to VAA + to handle supply to capacitor turn-on or turn-off current spikes. Figure 16 shows VAA + supply rejection versus frequency. Note that the frequency to be rejected scales with the clock: the 100Hz rejection with a 100kHz clock would be roughly equivalent to the 1kHz rejection with a 1MHz clock. The supply current for the CA3310 is dependent on clock frequency, supply voltage, and temperature. Figure 14 shows the typical current versus frequency and voltage, while Figure 15 shows it versus temperature and voltage. Note that if stopped in auto-balance, the supply current is typically somewhat higher than if free-running. See Specifications. 13 Differential Input A/D System As the CA3310 accepts a unipolar positive-analog input, the accommodation of other ranges requires additional circuitry. The input capacitance and the input energy also force using a low-impedance source for all but slow speed use. Figure 20 shows the CA3310 with a reference, input amplifier, and input-scaling resistors for several input ranges. The ICL7663S regulator was chosen as the reference, as it can deliver less than 0.25V input-to-output (dropout) voltage and uses very little power. As high a reference as possible is generally desirable, resulting in the best linearity and rejection of noise at the CA3310. The tantalum capacitor sources the VREF current spikes during a conversion cycle. This relieves the response and peak current requirements of the reference. The CA3140 operational amplifier provides good slewing capability for high bandwidth input signals and can quickly settle the energy that the CA3310 outputs at its VlN terminal. It can also drive close to the negative supply rail. If system supply sequencing or an unknown input voltage is likely to cause the operational amplifier to drive above the VDD supply, a diode clamp can be added from pin 8 of the operational amplifier to the V DD supply. The minus drive current is low enough not to require protection. With a 2MHz clock (~150kHz sampling), Nyquist criteria would give a maximum input bandwidth of 75kHz. The resistor values chosen are low enough to not seriously degrade system bandwidth (an operational amplifier settling) at that clock frequency. If A/D clock frequency and bandwidth requirements are lower, the resistor values (and input impedance) can be made correspondingly higher. The A/D system would generally be calibrated by tying V lN to ground and applying a voltage to VIN + that is 0.5 LSB (1/2048 of full-scale range) above ground. The operational amplifier offset should be adjusted for an output code dithering between 00016 and 00116 for unipolar use, or 10016 and 10116 for bipolar use. The gain would then be adjusted by applying a voltage that is 1.5 LSB below the positive full scale input, and adjusting the reference for an output dithering between 3FE16 and 3FF16 . Note that R1 through R5 should be very well matched, as they affect the common-mode rejection of the A/D system. Also, if R2 and R3 are not matched, the offset adjust of the operational amplifier may not have enough adjustment range in bipolar systems. The common-mode input range of the system is set by the supply voltage available to the operational amplifier. The range that can be applied to the VIN - terminal can be calculated by:  R4 ------- R5  R4 ------- R5 + 1 VIN- for the most negative, + 1 (VIN + -2.5V) - ( -------- )VREF+ for the most positive.   R4 R5 CA3310, CA3310A CD74HC175 will now release the clock, and the sample will end as it goes positive. Ten cycles later, the conversion will be complete, and DRDY will go active. Single +5V Supply If only a single +5V supply is available, an ICL7660 can be used to provide approximately +8V and -4V to the operational amplifier. Figure 20 shows this approach. Note that the converter and associated capacitors should be grounded to the digital supply. The 1kΩ in series with each supply at the operational amplifier isolates digital and analog grounds. +5V Operating and Handling Considerations Handling All inputs and outputs of Intersil CMOS devices have a network for electrostatic protection during handling. + 10Ω 8 Operating IN914 D 2 ICL7660S OPERATING VOLTAGE + +8V 4 D 5 -4V 3 + D During operation near the maximum supply voltage limit, care should be taken to avoid or suppress power supply turn-on and turn-off transients, power supply ripple, or ground noise; any of these conditions must not cause VDD - VSS to exceed the absolute maximum rating. + + D ALL CAPACITORS - 10µF, 10V D = DIGITAL GROUND INPUT SIGNALS To prevent damage to the input protection circuit, input signals should never be greater than VDD +0.3V nor less than VSS -0.3V. Input currents must not exceed 20mA even when the power supply is off. FIGURE 20. USING ICL7660 TO GENERATE SUPPLIES Digital Sample and Hold With a minimum of external logic, the CA3310 can be made to wait at the verge of ending a sample. A start pulse will then, after the internal aperture delay, capture the input and finish the conversion cycle. Figure 21 illustrates this application. UNUSED INPUTS A connection must be provided at every input terminal. All unused Input terminals must be connected to either VDD or VSS , whichever is appropriate. The CA3310 is connected as if to free run. The Data Ready signal is shifted through a CD74HC175, and at the low-going clock edge just before the sample would end, is used to hold the clock low. OUTPUT SHORT CIRCUITS Shorting of outputs to VDD or VSS may damage CMOS devices by exceeding the maximum device dissipation. The same signal, active high, is available to indicate the CA3310 is ready to convert. A low pulse to reset the CA3310/A VDD +5V D +5V DRST STRT D VAA + D0 - D9 VREF + VIN OUTPUT ENABLES DATA READY DRDY VREF VAA VSS A OEL OEM A ANALOG INPUT INPUT BUFFED AS REQUIRED DATA TO SYSTEM A FULL SCALE REFERENCE REXT CLK IN914 1/16 CD74HCO4E D D0 Q0 D1 READY TO CONVERT Q1 D2 Q2 Q2 VDD CP +5V CD74HC175E GND KEEP CAPACITANCE AT R EXT/CLK NODE AS LOW AS POSSIBLE D = DIGITAL GROUND A = ANALOG GROUND D3 Q0 Q1 Q3 Q3 D START CONVERT D NC FIGURE 21. DIGITAL TRACK-AND-HOLD BLOCK DIAGRAM 14 MR CA3310, CA3310A Dual-In-Line Plastic Packages (PDIP) E24.6 (JEDEC MS-011-AA ISSUE B) N 24 LEAD DUAL-IN-LINE PLASTIC PACKAGE E1 INDEX AREA 1 2 3 INCHES N/2 SYMBOL -B-AE D BASE PLANE -C- A2 SEATING PLANE A L D1 e B1 D1 A1 eC B 0.010 (0.25) M C A B S MAX MIN MAX 6.35 NOTES A - 0.250 - A1 0.015 - 0.39 A2 0.125 0.195 3.18 4.95 - B 0.014 0.022 0.356 0.558 - - 4 4 C L B1 0.030 0.070 0.77 1.77 8 eA C 0.008 0.015 0.204 0.381 - D 1.150 1.290 D1 0.005 - C eB NOTES: 1. Controlling Dimensions: INCH. In case of conflict between English and Metric dimensions, the inch dimensions control. 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of Publication No. 95. 4. Dimensions A, A1 and L are measured with the package seated in JEDEC seating plane gauge GS-3. 5. D, D1, and E1 dimensions do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.010 inch (0.25mm). 6. E and eA are measured with the leads constrained to be perpendicular to datum -C- . 7. eB and eC are measured at the lead tips with the leads unconstrained. eC must be zero or greater. 8. B1 maximum dimensions do not include dambar protrusions. Dambar protrusions shall not exceed 0.010 inch (0.25mm). 9. N is the maximum number of terminal positions. 10. Corner leads (1, N, N/2 and N/2 + 1) for E8.3, E16.3, E18.3, E28.3, E42.6 will have a B1 dimension of 0.030 - 0.045 inch (0.76 - 1.14mm). 15 MILLIMETERS MIN 29.3 32.7 5 - 5 0.13 E 0.600 0.625 15.24 15.87 6 E1 0.485 0.580 12.32 14.73 5 e 0.100 BSC 2.54 BSC - eA 0.600 BSC 15.24 BSC 6 eB - 0.700 - 17.78 7 L 0.115 0.200 2.93 5.08 4 N 24 24 9 Rev. 0 12/93 CA3310, CA3310A Small Outline Plastic Packages (SOIC) M24.3 (JEDEC MS-013-AD ISSUE C) N 24 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE INDEX AREA 0.25(0.010) M H B M INCHES E -B1 2 3 L SEATING PLANE -A- h x 45o A D -C- e A1 B 0.25(0.010) M C 0.10(0.004) C A M SYMBOL MIN MAX MIN MAX NOTES A 0.0926 0.1043 2.35 2.65 - A1 0.0040 0.0118 0.10 0.30 - B 0.013 0.020 0.33 0.51 9 C 0.0091 0.0125 0.23 0.32 - D 0.5985 0.6141 15.20 15.60 3 E 0.2914 0.2992 7.40 7.60 4 e µα B S 1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of Publication Number 95. 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Dimension “D” does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area. 6. “L” is the length of terminal for soldering to a substrate. 7. “N” is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch) 10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. 16 0.05 BSC 1.27 BSC - H 0.394 0.419 10.00 10.65 - h 0.010 0.029 0.25 0.75 5 L 0.016 0.050 0.40 1.27 6 N α NOTES: MILLIMETERS 24 0o 24 8o 0o 7 8o Rev. 0 12/93