LTC2494 typical perForMance characteristicsPSRR vs Frequency at VCCPSRR vs Frequency at VCC(2x Speed Mode)(2x Speed Mode) 0 0 VCC = 4.1V DC ±1.4V VCC = 4.1V DC ±0.7V REF+ = 2.5V REF+ = 2.5V –20 REF– = GND –20 REF– = GND IN+ = GND IN+ = GND –40 IN– = GND –40 IN– = GND fO = GND fO = GND –60 TA = 25°C –60 TA = 25°C –80 –80 RREJECTION (dB) REJECTION (dB) –100 –100 –120 –120 –140 –140 0 20 40 60 80 100 120 140 160 180 200 220 30600 30650 30700 30750 30800 FREQUENCY AT VCC (Hz) FREQUENCY AT VCC (Hz) 2494 G37 2494 G38 pin FunctionsGND (Pins 1, 3, 4, 5, 6, 31, 32, 33): Ground. Multiple ADCINP (Pin 25): Positive ADC Input. Tie to the output ground pins internally connected for optimum ground of a buffer/amplifier driven by MUXOUTP or tie directly current flow and VCC decoupling. Connect each one of to MUXOUTP. these pins to a common ground plane through a low ADCINN (Pin 26): Negative ADC Input. Tie to the output impedance connection. All eight pins must be connected of a buffer/amplifier driven by MUXOUTN or tie directly to ground for proper operation. to MUXOUTN. NC (Pin 2): No Connection. This pin can be left floating MUXOUTN (Pin 27): Negative Multiplexer Output. Used or tied to GND. to drive an external buffer/amplifier or can be shorted COM (Pin 7): The Common Negative Input (IN–) for All directly to ADCINN. Single-Ended Multiplexer Configurations. The voltage on V CH0 to CH15 and COM pins can have any value between CC (Pin 28): Positive Supply Voltage. Bypass to GND with a 10µF tantalum capacitor in parallel with a 0.1µF ceramic GND – 0.3V to VCC + 0.3V. Within these limits, the two capacitor as close to the part as possible. selected inputs (IN+ and IN–) provide a bipolar input range VIN = (IN+ – IN–) from –0.5 • VREF/Gain to 0.5 • VREF/Gain. REF+ (Pin 29), REF– (Pin 30): Differential Reference Input. Outside this input range, the converter produces unique The voltage on these pins can have any value between overrange and underrange output codes. GND and VCC as long as the reference positive input, REF+, remains more positive than the negative reference CH0 to CH15 (Pins 8 to 23): Analog Inputs. May be pro- input, REF–, by at least 0.1V. The differential voltage V grammed for single-ended or differential mode. REF = (REF+ – REF–) sets the full-scale range (–0.5 • VREF/ MUXOUTP (Pin 24): Positive Multiplexer Output. Used Gain to 0.5 • VREF/Gain) for all input channels. When to drive an external buffer/amplifier or can be shorted performing an on-chip temperature measurement, the directly to ADCINP. minimum value of REF = 2V. 2494fe 10 For more information www.linear.com/LTC2494