The new E-port interface circuits Filip Tavernier CERN

Required modifications to the previous version modify the TX so that it has a high-impedant output when disabled add a programmable (ON/OFF) termination network to the RX modify the RX so that it can handle both SLVS and LVDS signals boost the RX operation speed so that it can handle a 320 MHz clock signal (‘bandwidth switch’ to trade speed for power?) make a bi-directional cell Filip Tavernier - CERN2

Architecture of the SLVS TX signals: – input: digital single-ended voltage – output: analog differential current building blocks: – predriver: converts the input signal into a differential digital voltage – driver: converts the differential voltage into a differential current Filip Tavernier - CERN3

The previous TX predriver Filip Tavernier - CERN4 off = HIGH → outp = LOW & outn = HIGH

The TX driver Filip Tavernier - CERN5 off = LOW – inp = HIGH & inn = LOW → current flows ‘from right to left’ in the termination resistor – inp = LOW & inn = HIGH → ‘from left to right’ off = HIGH – bias1 = bias2= 0 V – a low-impedant path still exists between outp and GND because inn = HIGH and the zero-V t device is not completely off

The new TX predriver Filip Tavernier - CERN6 off = HIGH → outp = LOW & outn = LOW

Simulation of the new SLVS TX Filip Tavernier - CERN7 Simulation of the TX in the bi-directional cell Simulation of RC-extracted netlists Simulation in 3 corners: typical: V DD = 1.2 V (1.5 V) / T = 27° C / TT models slow: V DD = 1.1 V (1.4 V) / T = 100° C / SS models fast: V DD = 1.35 V (1.65 V) / T = -30° C / FF models Simulation with the ‘nominal’ current setting (2 mA) Input signal: Mbit/s Off-chip termination resistor of 100 Ω Package modeled by 1 nH bondwire inductors and 1 pF off-chip parasitic capacitance

Simulation of the SLVS V DD = 1.2 V Filip Tavernier - CERN8 current [mA] / power [mW]: typical: 3.31 / 3.97 slow: 2.73 / 3.00 fast: 4.13 / 5.58

Simulation of the SLVS V DD = 1.5 V Filip Tavernier - CERN9 current [mA] / power [mW]: typical: 4.01 / 6.02 slow: 3.41 / 4.77 fast: 4.93 / 8.13

SLVS TX layout Filip Tavernier - CERN10

SLVS and LVDS signals for the RX single-ended input signal levels when terminated with a differential 100 Ω resistor: →RX termination network needs nMOS (SLVS) and pMOS switch (LVDS) Filip Tavernier - CERN11 → 4 mA in 100 Ω → 2 mA in 100 Ω

Amplifier of the SLVS/LVDS RX Filip Tavernier - CERN12 input pair for SLVS (off for LVDS) input pair for LVDS (off for SLVS) reduce sensitivity of the current wrt variation of V DD

Biasing network of the SLVS/LVDS RX Filip Tavernier - CERN13 current in the 2 branches is equal and completely determined by: (W/L) p, k and R: M 5 is a start-up device to force that biasn ≠ 0 V and biasp ≠ V DD : → V th,1 + |V th,2 | + V th,5 < V DD,min = 1.1 V → V gs,1 + |V gs,2 | + V th,5 > V DD,max = 1.65 V

Simulation of the RX in the bi-directional cell Simulation of RC-extracted netlists Simulation in 3 corners: typical: V DD = 1.2 V (1.5 V) / T = 27° C / TT models slow: V DD = 1.1 V (1.4 V) / T = 100° C / SS models fast: V DD = 1.35 V (1.65 V) / T = -30° C / FF models Simulation with the on-chip termination network activated Input signal: Mbit/s Package modeled by 1 nH bondwire inductors and 1 pF off-chip parasitic capacitance Simulation of the new SLVS/LVDS RX Filip Tavernier - CERN14

Simulation of the V DD = 1.2 V with SLVS input signals Filip Tavernier - CERN15 current [µA] / power [µW]: typical: 320 / 384 slow: 310 / 341 fast: 298 / 402

Simulation of the V DD = 1.5 V with SLVS input signals Filip Tavernier - CERN16 current [µA] / power [µW]: typical: 391 / 587 slow: 439 / 615 fast: 390 / 644

Simulation of the V DD = 1.5 V with LVDS input signals Filip Tavernier - CERN17 current [µA] / power [µW]: typical: 453 / 680 slow: 474 / 664 fast: 481 / 794

Input CM range of the RX amplifier In theory, the RX amplifier has a rail-to-rail CM input range thanks to the input stage with nMOS and pMOS transistors. In reality, the voltage gain changes significantly with varying CM input voltage because the input transistors go out of saturation at ‘extreme’ CM voltages, as such reducing the gain of the amplifier. Note that the correct operation of the RX amplifier relies on the clipping of the signal at the input of the inverter (see slide 12) so that it can make a reliable decision. This means that the amplifier should not work in its linear region. Therefore, the effective CM input range varies with the input signal amplitude (a larger signal can work over a larger CM input range), or alternatively, the minimal signal amplitude depends on the CM input voltage (a smaller signal can be used at the ‘optimal’ CM input voltage than at the extremes). Filip Tavernier - CERN18

Input range of the V DD = 1.2 V for large signals in the typical corner Filip Tavernier - CERN19 → typical corner CM input V DD = 1.2 V for ‘large’ signals : 0 V – 1 V

Input range of the V DD = 1.2 V for small signals in the typical corner Filip Tavernier - CERN20 → typical corner CM input V DD = 1.2 V for ‘small’ signals : 0.1 V – 0.9 V

Input range of the V DD = 1.5 V for large signals in the typical corner Filip Tavernier - CERN21 → typical corner CM input V DD = 1.5 V for ‘large’ signals : 0 V – 1.3 V

Input range of the V DD = 1.5 V for small signals in the typical corner Filip Tavernier - CERN22 → typical corner CM input V DD = 1.5 V for ‘small’ signals : 0.1 V – 1.2 V

Input range of the V DD = 1.2 V for large signals in the slow corner Filip Tavernier - CERN23 → slow corner CM input V DD = 1.2 V for ‘large’ signals : 0.1 V – 0.9 V

Input range of the V DD = 1.2 V for small signals in the slow corner Filip Tavernier - CERN24 offset from inverter threshold → slow corner CM input V DD = 1.2 V for ‘small’ signals : 0.2 V – 0.8 V

Input range of the V DD = 1.5 V for large signals in the slow corner Filip Tavernier - CERN25 → slow corner CM input V DD = 1.5 V for ‘large’ signals : 0 V – 1.2 V

Input range of the V DD = 1.5 V for small signals in the slow corner Filip Tavernier - CERN26 → slow corner CM input V DD = 1.5 V for ‘small’ signals : 0.2 V – 1 V

Input range of the V DD = 1.2 V for large signals in the fast corner Filip Tavernier - CERN27 → fast corner CM input V DD = 1.2 V for ‘large’ signals : 0 V – 1.2 V

Input range of the V DD = 1.2 V for small signals in the fast corner Filip Tavernier - CERN28 → fast corner CM input V DD = 1.2 V for ‘small’ signals : 0 V – 1.1 V

Input range of the V DD = 1.5 V for large signals in the fast corner Filip Tavernier - CERN29 → fast corner CM input V DD = 1.5 V for ‘large’ signals : 0 V – 1.5 V

Input range of the V DD = 1.5 V for small signals in the fast corner Filip Tavernier - CERN30 → fast corner CM input V DD = 1.5 V for ‘small’ signals : 0.1 V – 1.5 V

SLVS/LVDS RX layout Filip Tavernier - CERN31