WHAT'S NEW IN MULTIPLEXERS? Trench Isolation gives high speed, latch-up protection, and low voltage operation ADG511, ADG512, ADG513: +3. 3v, +5V,#5V specified Ron<509@±5V Switching Time: <200ns@+5V ADG411, ADG412, ADG413:+15v, +12V specified Ron<3592@ ±15 V Switching Time:<150ns@±15V ADG508F, ADG509F, ADG528F:+15V specified Ron 300Q Switching Time:≤250ns Fault-Protection on Inputs and Outputs Figure 6.5 Multiplexer on-resistance is generally slightly dependent on the signal level(often called Ron modulation). This will cause signal distortion if the multiplexer must drive a load resistance, therefore the multiplexer output should therefore be isolated from the load with a suitable buffer amplifier. a separate buffer is not required if the multiplexer drives a high input impedance, such as a Pga, sha or ADC-but beware! Some SHAs and ADCs draw high frequency pulse current at their sampling rate and cannot tolerate being driven by an unbuffered multiplexer. a detailed analysis of multiplexers can be found in Reference 1, Section 8, or Reference 2, Section 2 An M-channel multiplexed data acquisition system is shown in Figure 6.6. The multiplexer output drives a Pga whose gain can be adjusted on a per- channel basis depending on the channel signal level. This ensures that all channels utilize the full dynamic range of the ADC. The PGa gain is changed at the same time as the multiplexer is switched to a new channel. The AdC Convert Command is applied fter the multiplexer and the pga have settled to the required accuracy(ILSB). The maximum sampling frequency(when switching between channels)is limited by the multiplexer switching time tmux, the Pga settling time tmga, and the adc conversion time tony as shown in the formula5 WHAT’S NEW IN MULTIPLEXERS? Trench Isolation gives high speed, latch-up protection, and low￾voltage operation ADG511, ADG512, ADG513: +3.3V, +5V, 5V specified Ron < 50 @ 5V Switching Time: <200ns @ 5V ADG411, ADG412, ADG413: 15V, +12V specified Ron < 35 @ 15V Switching Time: <150ns @ 15V ADG508F, ADG509F, ADG528F: 15V specified Ron < 300 Switching Time: < 250ns Fault-Protection on Inputs and Outputs Figure 6.5 Multiplexer on-resistance is generally slightly dependent on the signal level (often called Ron modulation). This will cause signal distortion if the multiplexer must drive a load resistance, therefore the multiplexer output should therefore be isolated from the load with a suitable buffer amplifier. A separate buffer is not required if the multiplexer drives a high input impedance, such as a PGA, SHA or ADC - but beware! Some SHAs and ADCs draw high frequency pulse current at their sampling rate and cannot tolerate being driven by an unbuffered multiplexer. A detailed analysis of multiplexers can be found in Reference 1, Section 8, or Reference 2, Section 2. An M-channel multiplexed data acquisition system is shown in Figure 6.6. The multiplexer output drives a PGA whose gain can be adjusted on a per-channel basis depending on the channel signal level. This ensures that all channels utilize the full dynamic range of the ADC. The PGA gain is changed at the same time as the multiplexer is switched to a new channel. The ADC Convert Command is applied after the multiplexer and the PGA have settled to the required accuracy (1LSB). The maximum sampling frequency (when switching between channels) is limited by the multiplexer switching time tmux, the PGA settling time tpga, and the ADC conversion time tconv as shown in the formula