Datasheet LTC1040 (Analog Devices) - 10

LTC1040
U TYPICAL APPLICATIO S The LTC1040 as a Linear Amplifier
With a simple RC filter, the LTC1040 can be made to should be set to 0.5mV to 1mV for best results. Notice that function as a linear amplifier. By filtering the logic output the higher the sampling frequency, fS, the lower RC can be. and feeding it back to the negative input, the loop forces This is important because the RC filter also sets the loop the output duty cycle [tON/(tON + tOFF)] so that VOUT equals response. A convenient way to keep fS as high as possible VIN (Figure 10). under all conditions is to connect a 100k resistor to pin 16 (OSC) with no capacitance to ground. The RC time constant is set to keep the ripple on the output small. The maximum output ripple is: ∆V = V+/fSRC and V+ + – R V+ V V OUT IN +1/2 LTC1040 0V – C tOFF VOUT = V+ tON tON + tOFF tON LTC1040 • TA08 LTC1040 • TA07
Figure 10. The LTC1040 as a Linear Amplifier 2-Wire 0
°
C to 100
°
C Temperature Transducer with 4mA to 20mA Output
12V TO 40V 0°C = 4mA V+ 100°C = 20mA R LM134 V– 43 1N914 430Ω 1k 3200 ZERO ADJUST 100k 6 6250 16 6 LT1019-5 – 5 18 + 4 1M 1/2 7 2N6657 † † – LTC1040 8 9 4 + + 18k 10 1µF 50Ω + 10µF 5k 182Ω † YELLOW SPRINGS INSTRUMENT PART NO. 44201 RETURN FULL-SCALE ADJUST ACCURACY = ±0.1°C + ±0.2°C = ±0.3°C CIRCUIT ERROR TRANSDUCER AT 25 ERROR LTC1040 • TA09 °C 1040fa 10