LTC2421/LTC2422 WUTYPICAL PERFOR A CE CHARACTERISTICSINL vs Output RateINL vs Output RateResolution vs Output Rate 20 20 24 VCC = 5V VCC = 3V VREF = 5V VREF = 2.5V FO = EXTERNAL FO = EXTERNAL 18 18 22 16 T 16 A = –45°C T T A = –45°C A = 25°C 20 14 14 T TA = 25°C T VCC = 5V TUE RESOLUTION (BITS) A = 90°C TUE RESOLUTION (BITS) A = 90°C 18 V 12 12 REF = 5V EFFECTIVE RESOLUTION (BITS) T f A = 25°C O = EXTERNAL T STANDARD DEVIATION A = 90°C T OF 100 SAMPLES A = –45°C 10 10 16 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 0 7.5 25 50 75 100 OUTPUT RATE (Hz) OUTPUT RATE (Hz) OUTPUT RATE (Hz) 24212 G28 24212 G29 24212 G30 UUUPIN FUNCTIONSVCC (Pin 1): Positive Supply Voltage. Bypass to GND be connected directly to a ground plane through a mini- (Pin␣ 6) with a 10µF tantalum capacitor in parallel with mum length trace or it should be the single-point-ground 0.1µF ceramic capacitor as close to the part as possible. in a single-point grounding system. FSSET (Pin 2): Full-Scale Set Input. This pin defines the CS (Pin 7): Active LOW Digital Input. A LOW on this pin full-scale input value. When VIN = FSSET, the ADC outputs enables the SDO digital output and wakes up the ADC. full scale (FFFFFH). The total reference voltage is Following each conversion, the ADC automatically enters FSSET – ZSSET. the Sleep mode and remains in this low power state as long as CS is HIGH. A LOW on CS wakes up the ADC. A CH0, CH1 (Pins 4, 3): Analog Input Channels. The input LOW-to-HIGH transition on this pin disables the SDO voltage range is – 0.125 • VREF to 1.125 • VREF. For digital output. A LOW-to-HIGH transition on CS during the VREF > 2.5V, the input voltage range may be limited by the Data Output transfer aborts the data transfer and starts a absolute maximum rating of – 0.3V to VCC + 0.3V. Conver- new conversion. sions are performed alternately between CH0 and CH1 for the LTC2422. Pin 4 is a No Connect (NC) on SDO (Pin 8): Three-State Digital Output. During the data the LTC2421. output period, this pin is used for serial data output. When the chip select CS is HIGH (CS = V ZS CC), the SDO pin is in a SET (Pin 5): Zero-Scale Set Input. This pin defines the high impedance state. During the Conversion and Sleep zero-scale input value. When VIN = ZSSET, the ADC periods, this pin can be used as a conversion status out- outputs zero scale (00000H). put. The conversion status can be observed by pulling CS GND (Pin 6): Ground. Shared pin for analog ground, LOW. digital ground, reference ground and signal ground. Should 24212f 8