MOTOROLA 1508/BEAJC

The MC1408 consists of a reference current amplifier, an R - 2R ladder, and eight high - speed current switches. For many applications, only a reference resistor and reference voltage need be added. The switches are noninverting in operation, therefore a high state on the input turns on the specified output current component. The switch uses curent steering for high speed, and a termination amplifier consisting of an active load gain stage with unity gain feedback. The termination amplifier holds the parasitic capacitance of the ladder at a constant voltage during switching, and provides a low impedance termination of equal voltage for all legs of the ladder. The R - 2R ladder divides the reference amplifier current into binarily - related components, which are fed to the switches. Note that there is always a remainder current which is equal to the least significant bit. This current is shunted to ground, and the maximum output current is 255/256 of the reference amplifier current, or 1.992 mA for a 2.0 mA reference amplifier current if the NPN current source pair is perfectly matched.

• Eight - Bit Accuracy Available in Both Temperature Ranges Relative Accuracy: ±0.19% Error maximum (MC1408L8, MC1408P8, MC1508L8)
• Seven and Six - Bit Accuracy Available with MC1408 Designated by 7 or 6 Suffix after Package Suffix
• Fast Settling Time - 300 ns typical
• Noninverting Digital Inputs are MTTL and CMOS Compatible
• Output Voltage Swing - +0.4V to - 5.0V
• High - Speed Multiplying Input Slew Rate 4.0 mA/μs
• Standard Supply Voltages: +5.0V and - 5.0V to - 15V