Digital Electronics: Principles, Devices and Applications

516 Digital ElectronicsClockStart8-Bit A/DControl&TimmingEnd Of Conversion(Interrupt)8 AnalogInputs8 ChannelsMultiplexingAnalogSwitchesComparatorS.A.RSwitchTreeTri-StateOutputLatchBuffer8-BitOutputs3-BitAddressAddressLatch EnableAddressLatchAndDecoder256R ResistorLadderV CC GND REF(+) REF(-) OutputEnableFigure 12.43 Internal architecture of AD 0808.± 12Vor± 15 V operation, guaranteed no missing codes over a temperature range from −25 °C to+85 ˚C and a maximum power dissipation of 595 mW.12.12.4 ADC-84/ADC-85/AD ADC-84/AD ADC-85/AD-5240ADC-84 and ADC-85 families of 10-bit (ADC 84-10 and ADC 85-10) and 12-bit (ADC 84-12 andADC 85-12) converters are complete A/D converters like the industry-standard ADC-80, with aninternal clock (1.9 MHz in the case of the 10-bit converters and 1.35 MHz in the case of the 12-bitconverters), comparator, reference (6.3 V) and input buffer amplifier. These have a conversion timeof 10 s (for 12-bit operation) and 6 s (for 10-bit operation). Figure 12.45 shows an internal blockschematic/pin connection diagram of ADC-84/ADC-85/AD-5240.12.12.5 AD 7820AD 7820 is a P-compatible, eight-bit A/D converter built around half-flash architecture. It incorporatesinternal sample-and-hold circuitry, which eliminates the need for an external sample-and-hold circuitfor signals having slew rates of less than 100 mV/s. Figure 12.46 shows the internal architecture/pinconnection diagram of AD 7820. Other features include a 1.36 s conversion time, a single +5 Vsupply and tristate buffered outputs.