CMOS MIXED SIGNAL 1.What is interconnect ?? 2.What is data transmission?? 3.How does the data travel?? 4.Forms of data transmission a)Analog data transmission b)Digital data transmission c)Serial data transmission d)Parallel data transmission e)Asynchronous data transmission f)Synchronous data transmission 5.What are the types of data transmission mode?? 6.Voltage-mode signaling 7.Current- mode signaling

1. AMITY UNIVERSITY
NOIDA, UTTAR PRADESH
TOPICS  Interconnects and data
transmission, Voltage-mode signaling and
Current- mode signaling data transmission
Prepared by:
Prerna Singh
M. Tech (VLSI)
Semester- 2
CMOS Mixed
Signal Design

2.  What is interconnect ??
 What is data transmission??
 How does the data travel??
 Forms of data transmission
 What are the types of data transmission mode??
 Voltage-mode signaling
 Current- mode signaling

3.  Interconnect is a connection between elements.
 Interconnects in an IC are physical connections between
two transistors and/or the external world.
 Chips are mostly made of wires called interconnect
 Transistors are little things under the wires
 Wires are as important as transistors , it’s affect
Speed
Power
Noise

6. Cont…

7.  Analog data transmission
 Digital data transmission
 Serial data transmission
 Parallel data transmission
 Asynchronous data transmission
 Synchronous data transmission

9. Fig 1.Digital signal waveform

16. Example 
Fig 2.

18. Example 
Fig 3. Half duplex Transmission

20. Voltage-Mode:
 Information is represented by voltage at the
nodes of the circuit.
Current-Mode:
 Information is represented by current flowing in
the branches of the circuit.

21.  In voltage mode signalling , receiver provides high input
impedance (ideally infinity).
 The information is conveyed in the form of voltage.
 The output voltage is a function of input signal and is varied
according to supply voltage.
 Fig.4 shows the theoretical model of conventional voltage
mode interconnect implementation.
Fig.4 Voltage mode filter

22.  The output is terminated by an open circuit.
 This high input impedance of the receiver gives
rise to high input capacitance which leads to high
charging and discharging time for RC interconnect
chain.
 Hence, voltage mode signalling has large delay.
 VM drivers use Thevenin’s equivalent series
termination.

23. •In current mode signalling , receiver provides low
impedance (ideally zero).
•The information is conveyed in the form of current.
•The output current is a function of input signal and is
varied according to supply/input current.
•Fig.5 shows the theoretical model of conventional
current mode interconnect implementation.
Fig.5 Current mode filter

24.  CM drivers use Norton’s equivalent series
termination.
 CM signalling reduced input impedance.
 It offers 84% to 87% reduction in delay
when compared with the conventional
voltage mode signalling

25.  It can be seen that either by reducing
voltage swing or by increasing charging and
discharging current ,delay can be reduced in
CM signalling.
 But in VM signalling,voltage swing can’t be
reduced.
 However charging and discharging current in
current mode circuit can be increased that
will give lesser delay .
 And that how CM circuit can give faster
transient response(stable).

26.  Performance Improvement
 High speed
 Less affected by voltage fluctuations
 Less delay

27. THANK YOU