Let us take example of MAX9957. Data rate can be calculated from TOC in datasheet as :

Figure 1: MAX9957 Driver 1 V, Signal Response            Figure 2: RS and RL in DUT pin of MAX9957

(RL = 50 Ohm, VDHV = 0.5V and VDLV = 0V) is programmed then the output voltage will be 250mVpp. This 250mVpp (half of programmed VDH value=500mVpp) is seen because of the 50ohm source resistance and a 50ohm RL as shown in Figure 2. The output voltage becomes half of the actual set VDH voltage (voltage divider law).

That’s why, even in above TOC: VDH is set to 1V, but actual swing is 500mVpp as shown in Figure 1.

Maximum data rate at any voltage can be calculated as –

=(Maximum data rate at 1V programmed VDHV) * (RL/RS+RL)/(our desired voltage)-----------1

                 Below are the steps to calculate data rate for this

- Typical Rise/Fall Time at 1V-programmed VDHV_, 20% to 80% = 130ps (From Electrical spec.)

              -  20% to 80% is % of the edge so the ‘full’ rising edge is about 130ps/0.6 = 216.67ps

              - Full NRZ waveform would be two edges or 2 * 216.67ps = 433.33ps

- Maximum data rate at 1V-programmed VDHV_ = 1/ 433.333ps = 2.3Gbps

RS=RL= 50, Putting this formula in equation 1, we get,

=2.3Gbps *( (50/50+50) /0.25

              = 2.3Gbps*0.5/0.25

              =4.6Gbps

Let us take example of MAX9957. Data rate can be calculated from TOC in datasheet as :

Figure 1: MAX9957 Driver 1 V, Signal Response            Figure 2: RS and RL in DUT pin of MAX9957

(RL = 50 Ohm, VDHV = 0.5V and VDLV = 0V) is programmed then the output voltage will be 250mVpp. This 250mVpp (half of programmed VDH value=500mVpp) is seen because of the 50ohm source resistance and a 50ohm RL as shown in Figure 2. The output voltage becomes half of the actual set VDH voltage (voltage divider law).

That’s why, even in above TOC: VDH is set to 1V, but actual swing is 500mVpp as shown in Figure 1.

Maximum data rate at any voltage can be calculated as –

=(Maximum data rate at 1V programmed VDHV) * (RL/RS+RL)/(our desired voltage)-----------1

                 Below are the steps to calculate data rate for this

- Typical Rise/Fall Time at 1V-programmed VDHV_, 20% to 80% = 130ps (From Electrical spec.)

              -  20% to 80% is % of the edge so the ‘full’ rising edge is about 130ps/0.6 = 216.67ps

              - Full NRZ waveform would be two edges or 2 * 216.67ps = 433.33ps

- Maximum data rate at 1V-programmed VDHV_ = 1/ 433.333ps = 2.3Gbps

RS=RL= 50, Putting this formula in equation 1, we get,

=2.3Gbps *( (50/50+50) /0.25

              = 2.3Gbps*0.5/0.25

              =4.6Gbps