® December 1997 R N OT M ECO FOR ED D N ME NE N ESIG WD HI-7151 S 10-Bit, High Speed, A/D Converter with Track and Hold Features Description • Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . 10µs The Intersil HI-7151 is a high speed 10-bit A/D converter which uses a 2-Step Flash algorithm to achieve throughput rates of 100kHz. A unique switched capacitor technique allows a new input voltage to be sampled while a conversion is taking place. • Continuous Throughput Rate . . . . . . . . . . . . . . . 100kHz • No Offset or Gain Adjustments Necessary • Internal Track and Hold Amplifier A Track and Hold amplifier is included on the chip, consisting of two high speed amplifiers and an internal hold capacitor. • Analog and Reference Inputs Fully Buffered • µP Compatible Byte Organized Outputs • Low Power Consumption . . . . . . . . . . . . . . . . . . 150mW • Uses a Single 2.5V Reference for ±2.5 V Input Range Applications Microprocessor bus interfacing is simplified by the use of standard Chip Select, Read, and Write control signals. The digital three-state outputs are byte organized for interfacing the either 8- or 16-bit systems. An Over-Range pin, together with the MSB, can be used to indicate an out-of-range condition. The HI-7151 operates with ±5V supplies. A single +2.5V reference is required to provide a bipolar input range from -2.5V to +2.5V. • µP Controlled Data Acquisition Systems • DSP - Avionics - Sonar Internal high speed CMOS buffers at both the analog and reference inputs simplify external drive requirements. Ordering Information • Process Control - Automotive Transducer Sensing - Industrial PART NUMBER • Robotics LINEARITY (MAX. DLE) TEMP. RANGE (oC) HI3-7151J-5 ±1 LSB 0 to 75 28 Ld PDIP HI3-7151K-5 ±1/2 LSB 0 to 75 28 Ld PDIP PACKAGE • Digital Communications HI3-7151A-9 ±1 LSB 0 to 85 28 Ld PDIP • Image Processing HI3-7151B-9 ±1/2 LSB 0 to 85 28 Ld PDIP HI1-7151S-2 ±1 LSB -55 to 125 28 Ld CERDIP HI1-7151T-2 ±1/2 LSB -55 to 125 28 Ld CERDIP Pinout HI-7151 (PDIP, CERDIP) TOP VIEW GND 1 V- 2 28 V+ 27 OVR VREF 3 26 D9 AG 4 25 D8 VIN 5 24 D7 SET 6 23 D6 BUSY 7 22 D5 CLK 8 21 D4 HOLD 9 20 D3 WR 10 19 D2 CS 11 18 D1 RD 12 17 D0 SMODE 13 16 HBE DG 14 15 BUS 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 1 File Number 3099.1 HI-7151 Functional Diagram VREF 3 REF AMP REF INVERT (+) 5 17 D0 (-) AG (ANALOG GROUND) 4 VIN (ANALOG INPUT) (33) TWO STEP FLASH RESISTOR LADDER LATCHES AND OUTPUT BUFFERS DATA OUTPUTS 26 27 INPUT BUFFER AMP 7 (1) BUS CTRL 15 16 D9 OVR BUSY BUS HBE TRACK HOLD AMP 9 V+ VGND 12 28 2 1 POWER SUPPLY DISTRIBUTION 10 CONTROL LOGIC 11 13 DG 14 (DIGITAL GROUND) 8 6 2 HOLD RD WR CS SMODE CLK SET HI-7151 Pin Descriptions PIN NAME 1 GND Ground return for comparators (0V). 2 V- Negative supply voltage input (-5V). 3 VREF 4 AG Analog ground reference (0V). 5 VIN Analog Input Voltage. 6 SET Connect to V+ for proper operation. 7 BUSY 8 CLK 9 HOLD 10 WR Write input. With CS low, starts conversion when pulsed low; continuous conversions when kept low. 11 CS Chip select input. Active low. 12 RD Read input. With CS low, enables output buffers when pulsed low; outputs updated at end of conversion when kept low. 13 DESCRIPTION Reference voltage input (+2.5V). Output High-Conversion complete. Output Low - Conversion in progress. Output floats when chip is not selected (RD and CS both high). Clock input. Indicates start of conversion. Active low. SMODE Slow memory mode input. Active high. 14 DG Digital ground (0V). 15 BUS Bus select input. High = all outputs enabled together D0 - D9, OVR. Low = outputs enabled by HBE. 16 HBE Byte select (HBE/LBE) input for 8-bit bus. Input high-High byte select, D8-D9, OVR Input low-low byte select, D0-D7. 17 D0 Bit 0 (Least significant, LSB). 18 D1 Bit 1. 19 D2 Bit 2. 20 D3‘ Bit 3. 21 D4 Bit 4. 22 D5 Bit 5. 23 D6 Bit 6. 24 D7 Bit 7. 25 D8 Bit 8 (Most Significant). 26 D9 Bit 9 (Sign). 27 OVR 28 V+ Low Byte Output Data Bits (High = True) High Byte Out of Range flag. Valid at end of conversion when output exceeds full scale. Positive supply voltage input (+5V). 3 HI-7151 Absolute Maximum Ratings (Note 1) Thermal Information Supply Voltage V+ to Gnd (DG/AG/GND) . . . . . . . . . . . . . . . . -0.3V < V+ < +5.7V V- to Gnd (DG/AG/GND). . . . . . . . . . . . . . . . . .-5.7V < V- < +0.3V Analog Input Pins . . . . . . . . . . . . . . . . . V- -0.3V < VINA < V+ +0.3V Digital I/O Pins . . . . . . . . . . . . . . . . . . .DG - 0.3V < VI/O < V+ +0.3V Thermal Resistance (Typical) θJA ( oC/W) θJC (oC/W) PDIP Package . . . . . . . . . . . . . . . . . . . __ N/A CERDIP Package . . . . . . . . . . . . . . . . __ __ Maximum Power Dissipation (Note 2). . . . . . . . . . . . . . . . . <500mW Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering, 10s) . . . . . . . . . . . . 300oC Operating Conditions Temperature Range HI3-7151X-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0oC to 75oC HI3-7151X-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -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. NOTES: 1. Input voltages may exceed the supply voltage provided the inputs current is limited to ±1mA. 2. Dissipation rating assumes device is mounted with all leads soldered to printed circuit board (derate above 75oC at -10mW/oC). Electrical Specifications PARAMETER V+ = +5V, V- = -5V, VREF = 2.5V, fCLK = 300kHz, 50% Duty Cycle, Unless Otherwise Specified (Note 4) SYMBOL (NOTE 3) TEMPERATURE J, A GRADE K, B GRADE MIN TYP MAX MIN TYP MAX UNITS TA = -25oC 10 - - 10 - - Bits TMIN to TMAX ACCURACY Resolution (Note 5) (With no missing codes) Integral Linearity Error Differential Linearity Error Bipolar Offset Error Unadjusted Gain Error RES ILE DLE VOS eG+ and eG- 10 - - 10 - - Bits TA = 25oC - ±0.5 ±1.0 - ±0.3 ±-0.5 LSB TMIN to TMAX - ±0.75 ±1.0 - ±0.5 ±0.75 LSB TA = 25oC - - ±1.0 - - ±0.5 LSB TMIN to TMAX - - ±1.0 - - ±0.75 LSB TA = 25oC - ±1.0 ±2.5 - ±0.6 ±1.5 LSB TMIN to TMAX - ±1.5 ±3.0 - ±1.0 ±2.0 LSB TA = 25oC - ±1.0 ±2.5 - ±0.6 ±1.5 LSB TMIN to TMAX - ±1.5 ±3.0 - ±1.0 ±2.0 LSB NOTE: 3. TMIN to TMAX: See Ordering Information Table. DC Electrical Specifications V+ = 5V, V- = -5V, VREF = 2.5V, TA = 25oC, fCLK = 300kHz, 50% Duty Cycle, Unless Otherwise Specified PARAMETER SYMBOL (NOTE 4) CONDITIONS 25oC 0oC to 75oC -40oC to 85oC MIN TYP MAX MIN MAX MIN MAX UNITS -VREF - VREF -VREF VREF -VREF VREF V ANALOG INPUT Analog Input Range VIR Analog INput Bias Current IBI - 0.01 100 - 100 - 100 nA Analog Input Capacitance (Note 5) CVIN - 8 20 - - - - pF 2.2 2.5 2.6 2.2 2.6 2.2 2.6 V VIN = 0V REFERENCE INPUT Reference Input Range (Note 6) VRR Reference Input Bias Current IBR - 0.01 100 - 100 - 100 nA Reference Input Capacitance (Note 5) CVR - 7 20 - - - - pF VREF = 2.5V 4 HI-7151 DC Electrical Specifications V+ = 5V, V- = -5V, VREF = 2.5V, TA = 25oC, fCLK = 300kHz, 50% Duty Cycle, Unless Otherwise Specified (Continued) PARAMETER SYMBOL (NOTE 4) CONDITIONS 25oC 0oC to 75oC -40oC to 85oC MIN TYP MAX MIN MAX MIN MAX UNITS TRACK AND HOLD (See Text) Slew Rate SR - 9 - - - - - V/µs Bandwidth BW - 1.5 - - - - - MHz Aperture Time - 30 - - - - - ns Aperture Uncertainty - 2 - - - - - ns - -80 - - - - - dB - 1.5 - - - - - µs fIN = 100kHz Feedthrough in HOLD Acquisition Time LOGIC INPUTS Input High Voltage VIH 2.0 - - 2.0 - 2.0 - V Input Low Voltage VIL - - 0.8 - 0.8 - 0.8 V Logic Input Current IIL - 0.05 1 - 1 - 1 µA - 5 17 - - - - pF Input Capacitance (Note 5) VIN = 0V, V+ CIN LOGIC OUTPUTS Output High Voltage VOH IOH = -200µA 2.4 - - 2.4 - 2.4 - V Output Low Voltage VOL IOL = 1.6mA - - 0.4 - 0.4 - 0.4 V Output Leakage Current IOL RD = V+, VOUT = V+ - 0.04 1 - 10 - 10 µA RD = V+, VOUT = 0V -1 -0.01 - -10 - -10 - µA High-Z State - 7 15 - - - - pF 4.5 5.0 5.5 4.5 5.5 4.5 5.5 V -4.5 -5.0 -5.5 -4.5 -5.5 -4.5 -5.5 V V+ = 5V, V- = -4.75V, -5.25V - ±0.1 ±0.05 - ±0.6 - ±0.6 LSB V- = -5V, V+ = 4.75V, 5.25V - ±0.1 ±0.5 - ±0.6 - ±0.6 LSB V+ = 5V, V- = -4.75V, -5.25V - ±0.1 ±0.5 - ±0.6 - ±0.6 LSB V- = -5V, V+ = 4.75V, 5.25V - ±0.1 ±0.5 - ±0.6 - ±0.6 LSB V+ = 5V ±10% V- = -5V ±10% VIN = 0V, Digital Outputs are Unloaded - 20 30 - 30 - 30 mA - -10 -15 - -15 - -15 mA - -8 -15 - -15 - -15 mA - -2 -3 - -3 - -3 mA - 0.02 10 - 10 - 10 µA Output Capacitance (Note 5) COUT POWER SUPPLY VOLTAGE RANGE (Note 7) V+ (Note 7) V- Function Operation Only POWER SUPPLY REJECTION V+, V- Gain Coefficient V+, V- Offset Coefficient eGVS VOSVS SUPPLY CURRENTS V+ Supply Current I+ V- Supply Current I- GND Current IGND DG Current IDG AG Current IAG NOTES: 4. FSR (Full Scale Range) = 2 X V REF (5V at VREF = 2.5V). LSB (Least Significant Bit) = FSR/1024 (4.88mV at VREF = 2.5V) 5. Parameter not tested. Parameter guaranteed by design, simulation, or characterization. 6. Only VOS and GAIN ERROR functionality tested at 2.2V and 2.6V. 7. Guaranteed by functionality test. 5 HI-7151 AC Electrical Specifications V+ = 5V ±10%, V- = -5V ±10%, VREF = 2.5V, TA = 25oC, fCLK = 300kHz, 50% Duty Cycle, CL = 100pF (including stray for D0 - D9, OVR, HOLD, BUSY), Unless Otherwise Specified (Note 11) 25oC 0oC to 75oC -40oC to 85oC SYMBOL NOTES MIN TYP MAX MIN MAX MIN MAX UNITS D 5 45 50 55 45 55 45 55 % tSPS 9 - - 3tck - 3tck - 3tck µs 9 60 - 10 60 10 60 10 µs tCONV 5, 8 - - 4tck +0.9 - 4tck +0.9 - 4tck +0.9 µs tCYC 9 - - fCLK/3 - fCLK/3 - fCLK/3/ 3 sps tCK - - 1/fCLK - - - - - CLOCK to HOLD Rise Delay tCKHR 5 150 290 500 140 525 120 525 ns WR Pulse Width tWRL 5, 8, 10 200 113 tck/2 225 tck/2 225 tck/2 ns WR to HOLD Delay tHOLD 5, 8 - 80 170 - 200 - 200 ns tBD 5, 8 - 40 200 - 230 - 230 ns WR to RD Active tWRD 5, 8 100 - - 100 - 100 - ns CLOCK to HOLD Fall Delay tCKHF 5, 9 50 125 250 40 275 25 275 ns HOLD to DATA change tDATA 5, 9 100 200 400 90 550 70 550 ns RD LO to Active tRD 5, 13 - 75 150 - 190 - 190 ns RD HI to Inactive tRX 5, 14 - 25 60 - 80 - 80 ns HBE to DATA tAD 5 - 70 150 - 165 - 165 ns CS to DATA tCD 5 - 95 180 - 210 - 210 ns RD to BUSY tBUSY 5 - 35 200 - 200 - 200 ns Rise Time tr 5, 12 - 50 100 - 125 - 125 ns Fall Time tf 5, 12 - 45 100 - 120 - 120 ns PARAMETER Clock Input Duty Cycle Continuous Conversion Time Slow Memory Mode Conversion Time Continuous Throughput CLOCK Period Busy to Data NOTES: 8. Slow memory mode timing. 9. Fast memory or DMA mode of operation, except the first conversion which is equal to tCONV . 10. Maximum specification to prevent multiple triggering with WR. 11. All input drive signals are specified with tr = tf ≤ 20ns and shall swing from VIL -0.4V to V IH +0.4V for all timing specifications. A signal is considered to change state as it crosses a 1.4V threshold (except tRD and tRX). 12. tr and tf load is CL = 100pF (including stray capacitance) to DG and is measured from the 10 - 90% point. 13. tRD is the time required for the data output level to change by 10% in response to RD crossing a voltage level of 1.4V. High-Z to VOH is measured with RL = 2.5kΩ and C L = 100pF (including stray) to DG. High-Z to VOL is measured with RL = 2.5kΩ to V+ and CL = 100pF (including stray) to DG. 14. trx is the time required for the data output level to change by 10% in response to RD crossing a voltage level of 1.4V. VOH to High-Z is measured with RL = 2.5kΩ and C L = 10pF (including stray) to DG. VOL to High-Z is measured with RL = 2.5 kΩ to V+ and CL = 10pF (including stray) to DG. 6 HI-7151 Timing Diagrams SMODE = +V, BUS = V+, HBE = V+ OR DG 0 1 tCK 2 3 4 5 CLOCK CS WR HOLD TRACK N tWRL tCKHR HOLD N TRACK N+1 tHOLD INTERNAL DATA RD BUSY N DATA tWRD tBUSY tBD D0-D9, OVR DATA N DATA tCONV FIGURE 1A. SLOW MEMORY MODE (16-BIT DATA BUS) 7 6 7 HI-7151 Timing Diagrams (Continued) SMODE = DG, BUS = DG 0 1 2 3 4 5 6 7 CLOCK tCD CS WR HOLD tSPS (WR MAY BE WIRED LOW) TRACK N tCKHF tHOLD HOLD N tCKHR HOLD N+1 TRACK N+1 HOLD N+2 TRACK N+2 TRACK N+3 tDATA INTERNAL DATA N+1 DATA N DATA RD HBE (HBE/LBE) tRD D0-D9, OVR DATA tAD HIGH BYTE BUSY tRX LOW BYTE N DATA HIGH BYTE LOW BYTE N+1 DATA FIGURE 1B. FAST MEMORY MODE (8-BIT DATA BUS) SMODE = +V: RD, WR, AND CS = DG 0 1 2 3 4 5 6 7 CLOCK HOLD INTERNAL DATA TRACK N HOLD N TRACK N+1 HOLD N+1 TRACK N+2 HOLD N+2 N-1 DATA N DATA N+1 DATA N-1 DATA N DATA N+1 DATA BUSY D0-D9, OVR DATA FIGURE 1C. DMA MODE 8 HI-7151 5 TO 32 DECODER (+VREF) AZ VREF 3 AZ 33 AZ + REF(+) AMP 17 AZ 1R AZ 32 AZ AG 4 AZ 1R 2 AZ REF(+) AMP SCAZ 32 TO 5 ENCODER OUTPUT BUFFERS LATCHES AND OUTPUT BUFFERS 1 LATCH BUS CTRL SCAZ (AG) VIN 5 (ANALOG INPUT) + + TRACK BUFFER AMP CH HOLD AMP SCAZ 32C V+ VGND CONTROL LOGIC + (-VREF ) (AG) 16 10 C - HOLD 15 12 SCAZ - 26 9 SCAZ 28 SWITCHED CAP AMP POWER SUPPLY DISTRIBUTION 2 1 DG 14 (DIGITAL GROUND) FIGURE 2. DETAILED BLOCK DIAGRAM 9 DO DATA OUTPUTS 27 7 LATCH AZ AZ (-VREF) LATCH AZ AZ + LATCH 11 13 8 6 D9 OVR BUSY BUS HBE HOLD RD WR CS SMODE CLK SET HI-7151 Detailed Description The 5-bit result of the first flash conversion is latched into the upper five bits of double buffered latches. It is also converted back into an analog signal by choosing the ladder voltage which is closest to but less than the input voltage. The selected voltage (VTAP) is then subtracted from the input voltage. This residue is amplified by a factor of 32 and referenced to the negative reference voltage (VSCA = (VIN VTAP) X 32 + VREF -). This subtraction and amplification operation is performed by a Switched Capacitor Amplifier (SCA). The output of the SCA falls between the positive and negative reference voltages and can therefore be digitized by the original 5-bit flash converter (second flash conversion). The HI-7151 is a high speed 10-bit A/D converter which achieves throughput rates of 100kHz by use of a Two Step Flash algorithm. A pipelined operation has been achieved through the use of switched capacitor techniques which allow the device to sample a new input voltage while a conversion is taking place. The HI-7151 requires a single reference input of +2.5V, which is internally inverted to 2.5V, thereby allowing an input range of -2.5V to +2.5V. 10 bits including sign are two’s complement coded. The analog and reference inputs are internally buffered by high speed CMOS buffers, which greatly simplifies the external analog drive requirements for the device. The 5-bit result of the second flash conversion is latched into the lower five bits of double buffered latches. At the end of a conversion, 10 bits of data plus an Out of Range bit are latched into the second level of latches and can then be put on the digital output pins. A/D Section The HI-7151 uses a conversion algorithm which is generally called a “Two Step Flash” algorithm. This algorithm enables very fast conversion rates without the penalty of high power dissipation or high cost. A detailed functional diagram is presented in Figure 2. The conversion takes place in three clock cycles and is illustrated in Figure 3. When the conversion begins, the track and hold goes into its hold mode for 1 clock cycle. During the first half clock cycle the comparator array is in its auto-zero mode and it samples the input voltage. During the second half clock cycle, the comparators make a comparison between the input voltage and the ladder voltages. At the beginning of the third half clock cycle, the first most significant 5-bit result becomes available. During the first clock cycle, the SCA was sampling the input voltage. After the first flash result becomes available and a ladder tap voltage has been selected the SCA amplifies the residue between the input and ladder tap voltages. During the next three half clock cycles, while the SCA output is settling to its required accuracy, the comparators go into their auto-zero mode and sample this voltage. During the sixth half clock cycle, the comparators perform another comparison whose 5-bit result becomes available on the next clock edge. The input voltage is first converted into a 5-bit result (plus Out of Range information) by the flash converter. This flash converter consists of an array of 33 auto-zeroed comparators which perform a comparison between the input voltage and subdivisions of the reference voltage. These subdivisions of the reference voltage are formed by forcing the reference voltage and its negative on the two ends of a string of 32 resistors. The reference input to the HI-7151 is buffered by a high speed CMOS amplifier which is used to drive one end of the resistor string. Another high speed amplifier configured in the inverting unity gain mode inverts the reference voltage with respect to analog ground and forces in onto the other end of the resistor string. Both reference amplifiers are offset trimmed at the factory in order to increase the accuracy of the HI-7151 and to simplify its usage. T CONVERSION CLOCK TRACK & HOLD COMPARATOR AUTO-ZERO (AZ) SCA AUTO-ZERO (SCAZ) T + 1 CONVERSION 1 2 3 4 HOLD VIN(T) SAMPLE VIN (T) CONVERT UPPER 5 BITS SAMPLE VIN (T) 5 6 TRACK VIN(T + 1) SAMPLE RESIDUAL AMPLIFY RESIDUAL INTERNAL DATA 10-BITS + OVR HOLD VIN(T + 1) CONVERT LOWER 5 BITS SAMPLE VIN(T + 1) SAMPLE VIN (T + 1) VIN(T) DATA FIGURE 3. INTERNAL ADC TIMING DIAGRAM 10 HI-7151 TABLE 1. A/D OUTPUT CODE TABLE ANALOG INPUT LSB = 2 (VREF) / 1024 OVR SIGN 9 MSB 8 7 6 5 4 3 2 1 LSB 0 2.500V to V+ (+OVR) 1 0 0 0 0 0 0 0 0 0 0 +VREF - 1 LSB 2.49512V (+Full Scale) 0 0 1 1 1 1 1 1 1 1 1 +1 LSB 0.00488V 0 0 0 0 0 0 0 0 0 0 1 0.000V 0 0 0 0 0 0 0 0 0 0 0 -1 LSB -0.00488V 0 1 1 1 1 1 1 1 1 1 1 -VREF -2.500V (-Full Scale) 0 1 0 0 0 0 0 0 0 0 0 -2.50488V to V- (-OVR) 1 1 0 0 0 0 0 0 0 0 0 ≥ +VREF 0 ≤ -VREF - 1 LSB VREF = 2.500V OUTPUT DATA Track and Hold Analog Input All of the internal amplifiers are offset trimmed at the factory to give improved accuracy and to minimize the number of external components. If necessary, offset error can be adjusted either at an external interface buffer or by using digital post correction. A Track and Hold amplifier has been fully integrated on the front end of the A/D converter. Because of the sampling nature of this A/D converter, the input is required to stay constant only during the first clock cycle. Therefore, the Track and Hold (T/H) amplifier “holds” the input voltage only during the first clock cycle and it acquires the input voltage for the next conversion during the remaining two clock cycles. The high input impedance of the T/H input amplifier simplifies analog interfacing. Input signals up to ±VREF can be directly connected to the A/D without buffering. The A/D output code table is shown in Table 1. Reference Input The reference input to the HI-7151 is buffered by a high speed CMOS amplifier. The reference input range is 2.2V to 2.6V. Power Requirements The timing signals for the Track and Hold amplifier are generated internally, and are also provided externally (HOLD) for synchronization purposes. The T/H amplifier consists of two high speed CMOS amplifiers and an internal hold capacitor. Its typical slew rate and bandwidth are 9V/µs and 1.5MHz respectively. It is configured to give a very small hold pedestal without the use of an external hold capacitor. The hold pedestal is typically less than 100µV. Power to the chip should be applied in the following order: V-, V+, and VREF . In applications where V+ is supplied prior to V-, the positive supply current will be approximately 2 times its nominal value until V- is applied (this is not a latchup condition). Initialization Acquisition of the analog input signal is the time required by the T/H for its output to reach its final value within a specified error band. This time is a function of the logic delay time, op amp slewing time, and settling time. The T/H is in the track mode for 2 clock cycles (6.7µs at CLK = 300kHz) but the output typically settles to within 1/4 LSB in 1.5µs. In fast memory and DMA modes (after proper power, VREF , and clock) up to 6 clock cycles are required for circuit initialization. After circuit initialization, valid data will be available in 3 clock cycles. Aperture delay time is the time required for the T/H switch to open following the internal hold command. This is the delay with respect to falling edge of WR and the internal hold command. It is equal to Thold (type) - 50ns (typ) which is typically 30ns. The HI-7151 can be interfaced to microprocessors through the use of standard Write, Read, Chip Select, and HBE control pins. The digital outputs are two’s complement coded, three-state gated, and byte organized for bus interface with 8- and 16-bit systems. The digital outputs (D0 D9, OVR, and BUSY) may be accessed under control of BUS, byte enable input HBE, chip select, and read inputs for a simple parallel bus interface. The microprocessor can read the current data in the output latches in typically 75ns/byte (trd). An over range pin (OVR) together with the MSB (D9) pin set to either a logic 0 or 1 will indicate a positive or negative over-range condition respectively. All digital output buffers are capable of driving one TTL load. Microprocessor Interface Aperture uncertainty (jitter) is a range of variation in the aperture time. The greater the aperture time the larger the uncertainty in the analog voltage being converted. If the aperture time is nulled out by advancing the hold command (WR) or the signal is repetitively sampled, aperture uncertainty becomes the major source of time error. The aperture uncertainty for the T/H is typically 2ns which sets the maximum input bandwidth to 77.7kHz for 1 LSB resolution. fMAX = 1/(π X 2n X ta), where n = resolution in bits, ta = aperture uncertainty The HI-7151 can be interfaced to a microprocessor using one of three modes: slow memory, fast memory, and DMA mode. 11 HI-7151 Slow Memory Mode TABLE 3. FAST MEMORY MODE I/O TRUTH TABLE (SMODE = DG) In slow memory mode, the conversion will be initiated by the microprocessor by selecting the chip (CS) and pulsing WR low. This mode is selected by hardwiring the SMODE pin to V+. This mode is intended for use with microprocessors (such as the 8086) which can be forced into a WAIT state. For example, in configuration where the BUSY output is tied to the 8086 READY input, an attempt to read the data before the conversion is complete will force the processor into a WAIT state until BUSY goes high, at which time the data at the output is valid. This resembles a 10µs access time RAM. It allows the processor to initiate a conversion, WAIT, and READ data with a single READ instruction. When the 8-bit bus operation is selected, high and low byte data may be accessed in either order. An I/O truth table is presented in Table 2 for the slow memory mode of operation. TABLE 2. SLOW MEMORY MODE I/O TRUTH TABLE (SMODE = V+) CS WR RD 0 0 X X X Initiates a Conversion 1 X X X X Disables All Chip Commands 0 X 0 1 X D0 - D9 and OVR Enabled 0 X 0 0 0 Low Byte Enabled: D0 - D7. 0 X 0 0 1 High Byte Enabled: D8 - D9, OVR X X 1 X X Disables All Outputs (High Impedance) BUS HBE CS WR RD X 0 X X X Continuous Conversion, WR May Be Tied to DG 1 X X X X Disables Only The RD Command 0 X 0 1 X D0 - D9 & OVR Enabled 0 X 0 0 1 High Byte Enabled: D8 - D9, OVR (Enable 1st) 0 X 0 0 0 Low Byte Enabled: D0 - D7 (Must Enable 2nd) X X 1 X X Disables All Outputs (High Impedance) BUS HBE FUNCTION NOTE: X = Don’t Care DMA Mode FUNCTION This mode is a complete hardware mode where the HI-7151 continuously converts. The user implements hardware to store the results in memory, bypassing the microprocessor. This mode is recognized by the chip when SMODE is hardwired to V+ and CS, RD, WR are hardwired to DG. When 8-bit bus operation is selected, high and low byte data may be accessed in either order. BUSY is continuously low when accessed with a read command in this mode. An I/O truth table is presented in Table 4 for the DMA mode of operation. TABLE 4. DMA MODE I/O TRUTH TABLE (SMODE = V+, CS = WR, RD = DG) NOTE: X = Don’t Care Fast Memory Mode The fast memory mode of operation is selected by tying the SMODE and WR pins to DG. In this mode, the chip performs continuous conversions and only CS and RD are required to read the data. Whenever the SMODE pin is low, WR is independent of CS in starting a conversion cycle. During the first conversion cycle, HOLD follows WR going low. BUS HBE FUNCTION 1 X D0 - D9 and OVR Enabled 0 0 Low Byte Enabled: D0 - D7 0 1 High Byte Enabled: D8 - D9, OVR NOTE: X = Don’t Care Optimizing System Performance Data can be read a byte at a time or all 11 bits at once. The internal logic disables the output latches from being updated during a read after the high byte data is accessed. It will continue to be disabled until after the low byte data is accessed. THEREFORE, WHEN 8-BIT BUS OPERATION IS SELECTED, THE DATA MUST BE ACCESSED HIGH BYTE FIRST, LOW BYTE NEXT. If the low byte is accessed first followed by high byte, the results from the next conversion cycle will be lost because the updating of the output latch is disabled. BUSY is continuously low when accessed with a read command in this mode. An I/O truth table is presented in Table 3 for the fast memory mode of operation. The HI-7151 has three ground pins (AG, DG, GND) for improved system accuracy. Proper grounding and bypassing is illustrated in Figure 4. The AG pin is a ground pin that does not carry any current and is used internally as a reference ground. The reference input and analog input should be referenced to the analog ground (AG) pin. The digital inputs and outputs should be referenced to the digital ground (DG) pin. The GND pin is a return point for the supply current of the comparator array. The comparator array is designed such that this current is approximately constant at all times and does not vary with input voltage. By virtue of the switched capacitor nature of the comparators, it is necessary to hold GND firmly at zero volts at all times. Therefore, the system ground star connection should be located as close to this pin as possible. The data can be defined in time by monitoring the HOLD pin. The conversion data can be read after HOLD has gone low. 12 HI-7151 Figure 8 illustrates an application where the HI-7151 is used with an analog multiplexer to form a multi-channel data acquisition system. Either slow memory or fast memory modes of operation can be selected. Fast memory mode should be selected for maximum throughput. Multiplexer channel acquisition should occur approximately 500ns after HOLD goes high. This allows 2 clocks minus 0.5µs for the input to settle. With a 300kHz clock the input has up to 6.2µs to settle. As in any analog system, good supply bypassing is necessary in order to achieve optimum system performance (minimize conversion errors). The power supplies should be bypassed with at least a 20µF tantalum and 0.1µF ceramic capacitors to GND. The reference input should be bypassed with a 0.1µF ceramic capacitor to AG. The capacitor leads should be as short as possible. The pins on the HI-7151 are arranged such that the analog pins are well isolated from the digital pins. In spite of this arrangement, there is always pin to pin coupling. Therefore the analog inputs to the device should not be driven from very high output impedance sources. PC board layout should screen the analog and reference inputs with AG. Using a soldier mask is good practice and helps reduce leakage due to moisture contamination on the PC board. An intelligent system which performs a scale factor adjustment under software control with the addition of a programmable gain block between the multiplexer and HI-7151 is illustrated in Figure 9. The microprocessor first performs a conversion and then checks the over-range status (OVR) bit. If the OVR bit is high, the microprocessor addresses a precision gain circuit for scale factor adjustment and initiates another conversion. The microprocessor must keep track of the selected scale factor. Applications Typical applications are illustrated in Figures 5 through 7 for the slow memory, fast memory, and DMA modes of operation. The output data is configured for 16-bit bus operation of these three applications. By tying BUS and DG and connecting the HBE input to the system address decoder, the output data can be configured for 8-bit bus systems. The accuracy of the programmable gain amplifier should be better than 0.05%. For optimum system performance, op amp frequency response, settling time, and charge injection of the analog switch must be considered. Figure 10 illustrates the HI-7151 interfaced to FIFO memories for use in DMA applications. 20µF 0.1µF + + 2.5V P.S. -5V P.S. - - + HI-7151 0.1µF 1 GND 20µF 2 V- 0.1µF ANALOG INPUT V+ V+ 28 OVR 27 3 VREF D9 26 4 AG D8 25 5 VIN D7 24 6 SET D6 23 7 BUSY D5 22 8 CLK D4 21 9 HOLD D3 20 10 WR D2 19 11 CS D1 18 12 RD D0 17 13 SMODE HBE 16 14 DG BUS 15 FIGURE 4. GROUND AND POWER SUPPLY DECOUPLING 13 5V P.S. HI-7151 HI-7151 2 V- -5V +5V V+ 28 OVR 27 3 VREF D9 26 0V 4 AG D8 25 ANALOG INPUT 5 VIN D7 24 6 SET D6 23 7 BUSY D5 22 8 CLK D4 21 9 HOLD D3 20 +2.56V V+ 300kHz CLOCK 10 WR D2 19 11 CS D1 18 12 RD D0 17 13 SMODE HBE 16 14 DG BUS 15 CS WR HOLD TRACK N HOLD N TRACK N+1 INTERNAL DATA N DATA RD BUSY D0-D9, OVR DATA N DATA FIGURE 5. SLOW MEMORY MODE APPLICATION 14 16-BIT DATA BUS ADDRESS BUS READY WR LINE RD LINE 1 GND HI-7151 HI-7151 OVR 27 3 VREF D9 26 0V 4 AG D8 25 ANALOG INPUT 5 VIN D7 24 6 SET D6 23 7 BUSY D5 22 8 CLK D4 21 9 HOLD D3 20 +2.56V V+ 300kHz CLOCK 10 WR D2 19 11 CS D1 18 12 RD D0 17 13 SMODE HBE 16 14 DG BUS 15 DATA CS WR HOLD +5V V+ 28 16-BIT DATA BUS 2 V- -5V ADDRESS BUS RD LINE 1 GND (WR MAY BE WIRED LOW) TRACK N HOLD N HOLD N+1 TRACK N+1 INTERNAL DATA TRACK N+2 N DATA HOLD N+2 N+1 DATA RD D0-D9, OVR DATA N DATA BUSY FIGURE 6. FAST MEMORY MODE APPLICATION 15 TRACK N+3 N+1 DATA HI-7151 HI-7151 +5V 1 GND OVR 27 3 VREF D9 26 0V 4 AG D8 25 ANALOG INPUT 5 VIN D7 24 6 SET D6 23 7 BUSY D5 22 8 CLK D4 21 9 HOLD D3 20 +2.56V V+ 300kHz CLOCK V+ TRACK N HOLD V+ 28 2 V- HOLD N INTERNAL DATA D0-D9, OVR 10 WR D2 19 11 CS D1 18 12 RD D0 17 13 SMODE HBE 16 14 DG BUS 15 TRACK N+1 16-BIT DATA BUS -5V HOLD N+1 N-1 DATA TRACK N+2 HOLD N+2 N DATA N+1 DATA 10µs FIGURE 7. DMA MODE APPLICATION ADDRESS BUS ADDRESS DECODER ANALOG INPUTS S1 S2 S3 S4 S5 S6 S7 S8 HBE VIN WR DG528 MUX ADDRESS DECODER DG BUS V+ VDG RS SYSTEM RESET A0-A2, EN +2.56V +5V -5V RD VREF AG SIGNAL GROUND CS V+ HI-7151 ADC (SLOW MEMORY MODE) WR SMOD HOLD MICROPROCESSOR V+ BUSY VDG CLK GND SET D0-D7 D8-D9, OVR 8-BIT DATA BUS FIGURE 8. MULTI-CHANNEL DATA ACQUISITION SYSTEM 16 300kHz CLOCK V+ ADDRESS BUS ADDRESS DECODER ANALOG INPUTS S1 S2 S3 S4 S5 S6 S7 S8 D DG528 MUX V+ VDG HBE BUS CS WR ADDRESS DECODER DG VIN PROGRAMMBLE GAIN AMP +2.56V RD VREF AG SIGNAL GROUND V+ +5V RS SYSTEM RESET CS HI-7151 ADC (SLOW MEMORY MODE) SMOD HOLD DG CLK GND SET D0-D2, EN MICROPROCESSOR V+ BUSY V- -5V WR D0-D7 300kHz CLOCK V+ D8-D9, OVR 8-BIT DATA BUS FIGURE 9. MULTI-CHANNEL DATA ACQUISITION SYSTEM WITH PROGRAMMABLE GAIN V+ ANALOG INPUT +2.56V VREF AG SIGNAL GROUND +5V -5V BUS HBE SMODE D8-D9, OVR VIN V+ VDG GND HI-7151 ADC SET CLK HOLD V+ 300kHz BUSY RD WR CS D0-D3 64 x 4-BIT FIFO D4-D7 64 x 4-BIT FIFO D8-D9, OVR 64 x 4-BIT FIFO SHIFT IN DG FIGURE 10. DMA/FIFO DATA ACQUISITION SYSTEM 17 TO PARALLEL DATA BUS COMPOSITE OUTPUT READY SHIFT OUT