======================================================================== 74F500 6-BIT ANALOG-TO-DIGITAL FLASH CONVERTER ======================================================================== Family: Fairchild FAST (Advanced Schottky TTL) Source: 1985 Fairchild FAST Data Book, pages 4-365 ... 4-368. The 1980 data book carries the 'F500 in its Section 3 selection guide only (page 3-29, description and logic symbol). Status: PRELIMINARY -- page 4-365 carries a "Preliminary" watermark. Ratings: Vcc (TTL) = +5.0 V +/-5%, Vee (Analog) = -6.0 V, TA = 0 to +70 deg C DESCRIPTION ----------- The 'F500 is a 6-bit, fully parallel analog-to-digital converter capable of sampling at rates from 0 to 50 MHz. Conversion is accomplished by 63 comparators spaced one quanta apart on a voltage reference ladder. All comparators measure the analog input against their reference simultaneously. The most significant comparator that finds the analog input to be greater than its reference has its output encoded to a 6-bit, active HIGH binary number, stored in latches. Two polarity control inputs are provided: PM complements the most significant output bit and PL complements the lesser five output bits. The circuit operates from +5.0 V and -6.0 V supplies and has separate digital and analog grounds. Both ends of the reference ladder are brought out, one to VRT (nominally zero volts) and the other to VRB (nominally -1.0 V). CONNECTION DIAGRAM (24-pin DIP) ------------------------------- Pin Function Pin Function --- ------------------------ --- ------------------------ 1 Vee Analog supply 24 NC no connection 2 NC no connection 23 NC no connection 3 NC no connection 22 VRT Reference (Top) 4 PM Polarity Control MSB 21 VIN Analog input 5 PL Polarity Control LSB 20 AGnd Analog Ground 6 Vee Analog supply 19 VIN Analog input 7 Vcc TTL supply 18 AGnd Analog Ground 8 DGnd TTL Ground 17 VIN Analog input 9 Q5 Digital output 5 16 VRB Reference (Bottom) 10 Q4 Digital output 4 15 CVT Convert 11 Q3 Digital output 3 14 Q0 Digital output 0 12 Q2 Digital output 2 13 Q1 Digital output 1 Q0 is the MSB and Q5 the LSB. The analog input VIN and the analog ground AGnd are each brought out on three pins (17, 19, 21 and 18, 20 respectively), and the analog supply Vee on two (pins 1 and 6); pins 2, 3, 23 and 24 are no-connect. INPUT LOADING / FAN-OUT ----------------------- Pin Names Description U.L. HIGH/LOW ---------- ------------------------------ ------------- AVee Analog Supply Voltage N/A DVcc TTL Supply Voltage N/A DGnd TTL Ground N/A AGnd Analog Ground N/A Q0 - Q5 Digital Output, Q0=MSB, Q5=LSB 25 / 12.5 PM Polarity Control MSB Output 0.5 / 0.375 PL Polarity Control LSB Outputs 0.5 / 0.375 VRT Reference Voltage (Top) N/A VRB Reference Voltage (Bottom) N/A VIN Analog Voltage Input N/A CVT Convert 0.5 / 0.375 PERFORMANCE CHARACTERISTICS OVER RECOMMENDED OPERATING TEMPERATURE RANGE ------------------------------------------------------------------------ Parameter Min Typ Max Units ----------------------------- --- ----- --- ----- Resolution 6 Bits 1.6 % Input Range 1.0 V Linearity Error 0.4 % Offset Error, Top +27 mV Bottom -27 mV Aperture Jitter 30 psec Bandwidth, Small Signal 3.0 dB 45 MHz 0.1 dB 8 MHz Transient Response 20 ns Signal-to-Noise Ratio Peak Signal/RMS Noise 43 dB 42 dB RMS Signal/RMS Noise 34 dB 33 dB Noise Power Ratio 25.5 dB INTERFACE SPECIFICATIONS OVER RECOMMENDED OPERATING TEMPERATURE RANGE --------------------------------------------------------------------- Power supply, at TA = +25 C, Vcc (TTL) = +5.0 V, Vee (Analog) = -5.0 V, CL = 50 pF: Symbol Parameter Min Typ Max Units ------ --------------- ----- ------ ----- ----- ICC Supply Current 20 30 mA IEE Supply Current -105 -150 mA Vcc Supply Voltage +4.50 +5.00 +5.50 V Vee Supply Voltage -5.75 -6.00 -6.25 V Analog, at the same conditions: Symbol Parameter Min Typ Max Units --------- ------------------------- --- --- --- ----- Signal Input: VIN Input Voltage V RIN Equivalent Input Impedance 15 -- inf kohm CIN Input Capacitance 85 pF IBIAS Constant Input Bus 110 uA IB Clock Synchronous Bias 25 uA Reference Input: IRT Reference Current, Top 8 mA IRB Reference Current Bottom -8 mA R Reference Resistor 1.9 2.0 ohm VRT Reference Voltage -1.1 0 +0.1 V VRB Reference Voltage -0.9 -1.0 -2.1 V VRT-VRB Input Voltage Range 0.8 1.0 1.2 V AC CHARACTERISTICS ------------------ At TA = +25 C, Vcc (TTL) = +5.0 V, Vee (Analog) = -6.0 V, CL = 50 pF. Symbol Parameter Min Typ Max Units ------ ----------------------------- ---- ---- --- ----- fmax Maximum Clock Frequency 25 40 -- MHz tPLH Propagation Delay -- 18.0 -- ns tPHL Aperture Delay -- 18.0 -- ns tA Aperture Delay -- 10.0 -- ns tw (H) Convert Pulse Width, HIGH 12.0 -- -- ns tw (L) Convert Pulse Width, LOW 12.0 -- -- ns