LTC1420 UUUPIN FUNCTIONSVDD (Pin 23): Analog 5V Supply. Bypass to GND with a 1µF CLK (Pin 26): Conversion Start Signal. This active high ceramic. signal starts a conversion on its rising edge. GND (Pin 24): Analog Power Ground. OF (Pin 27): Overflow Output. This signal is high when the digital output is 011111111111 or 100000000000. VSS (Pin 25): Negative Supply. Can be – 5V or 0V. If VSS is not shorted to GND, bypass to GND with a 1µF ceramic. GAIN (Pin 28): Gain Select for Input PGA. 5V selects an input gain of 1, 0V selects a gain of 2. UUWFUNCTIONAL BLOCK DIAGRA 5V OPTIONAL 3V LOGIC SUPPLY VDD VDD GAIN (PIN 7) (PIN 23) OVDD +AIN S/H PIPELINED 12-BIT ADC OF –AIN D11 (MSB) OUTPUT VCM BUFFERS DIGITAL CORRECTION MODE SELECT LOGIC D0 (LSB) SENSE 2.5V CLK REFERENCE VREF 2.048V 1420 BD V GND GND OGND SS GND (PIN 6) (PIN 8) (PIN 24) 0V OR –5V W UWTI I G DIAGRA N + 1 ANALOG N N + 2 INPUT N + 3 tCLOCK tH tL CLK tCONV tACQ DATA N – 3 N – 2 N – 1 N OUTPUT 1420 TD 1420fa 7