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What are the Switch Characteristics and Timing Characteristics of a bus switch?

“Switch Characteristics” indicate the delay time from when a signal is applied to the input of the switch to when it is output. The switch characteristics represent the propagation delay of the switch alone and the output skew, which is the difference in propagation delay between different switches. The timing characteristic is the time it takes for the switch to operate after a voltage is applied to the power or control input of the switch.

Switching Characteristics and Timing Characteristics are described using the TDS4 Series High-Speed Differential Interface Bus Switches.

The switch characteristics specify the following:

Propagation Delay (t_PLH, t_PHL)
Output Skew (Bit-to-Bit) (t_{SK (b)})
Output Skew (Between Channels) (t_{SK (CH)})

**Table-1 Switching properties of the TDS4 series. (TDS4A212MX)**
Characteristics	Symbol	Test Condition	V_CC (V)	Typ.	Max	Unit
Propagation delay time (Note 1)	t_PLH/t_PHL	R_L = 50Ω, f = 10GHz (Refer to Fig. 13.1 and 13.7 in the datasheet for details.)	3.3	33	-	ps
Output skew (bit to bit) (Note 1)	t_SK(b)	R_L = 50Ω, f = 10GHz (Refer to Fig. 13.1 and 13.8 in the datasheet for details.)	3.3	6	-	ps
Output skew (channel to channel) (Note 1)	t_SK(CH)	R_L = 50Ω, f = 10GHz (Refer to Fig. 13.1 and 13.7 in the datasheet for details.)	3.3	6	-	ps

Note 1: Parameter guaranteed by design.

Fig. 1 Timing chart of propagation delay (tPLH, tPHL) and output skew (tSK (CH), tSK (b) ) — Fig. 1 Timing chart of propagation delay (t_PLH, t_PHL) and output skew (t_{SK (CH)}, t_{SK (b)})

Each item is explained in detail below.

Propagation delay time (t_PLH, t_PHL)
The propagation delay time is the time it takes for a signal to be input to and output from the I/O pins of a switch.
This time is defined as the time it takes for the input and output signals to change between the “L” and “H” levels. The time for the output signal to change from an “L” level to an “H” level is defined as t_PLH, and the time for the output signal to change from an “H” level to an “L” level is defined as t_PHL
Output skew (bit to bit) (t_{SK (b)})
Output skew (bit to bit) indicates the propagation delay time difference between differential pairs (plus and minus signals).
For example, it shows the propagation delay time difference between the path from A0+ to B0+ and the path from A0- to B0-.
Output Skew (channel to channel) (t_{SK (CH)})
Output skew (channel to channel) indicates the propagation delay time difference between channels in a bus switch product with multiple channels.
For example, it shows the propagation delay time difference between the path from A0+ to B0+ and the path from A1+ to B1+.

The timing charts for the propagation delay (t_PLH, t_PHL), output skew (bit to bit) (t_{SK (b)}), and output skew (channel to channel) (t_{SK (CH)}) are shown in Fig. 1.

The Timing characteristics specify the following:

Start-up time (t_sup)
Turn-ON time (t_on)
Turn-OFF time (t_off)
Break before make (TBBM)

**Table-2 Timing-characteristics of the TDS4 series.**
Characteristics	Symbol	Test Condition	V_CC (V)	Min	Typ.	Max	Unit
Start-up time.	t_sup	(Refer to Fig. 13.5 in the datasheet for details.)	1.65 to 3.6	-	-	100	µs
Turn-ON time (SEL to Output)	t_on	R_L = 50Ω, C_L = 5pF (Refer to Fig. 13.5 in the datasheet for details.)	1.65 to 3.6	-	-	180	ns
Turn-ON time (/OE to Output)	t_on		1.65 to 3.6	-	-	100	µs
Turn-OFF time (SEL to Output)	t_off	R_L = 50Ω, C_L = 5pF (Refer to Fig. 13.5 in the datasheet for details.)	1.65 to 3.6	-	-	18	ns
Turn-OFF time (/OE to Output)	t_off		1.65 to 3.6	-	-	21	ns
Break before make	TBBM	R_L = 50Ω, C_L = 5pF (Refer to Fig. 13.6 in the datasheet for details.)	1.65 to 3.6	55	-	160	ns

Fig. 2 Timing chart of start-up time (tsup), turn-on time (ton) and turn-off time (toff) — Fig. 2 Timing chart of start-up time (t_sup), turn-on time (t_on) and turn-off time (t_off)

Each item is explained in detail below.

Start-up time (t_sup)
The Start-up time indicates the time from when the power supply voltage is applied to the switch until the switch operates.
Turn-ON time (t_on)
Turn-ON time indicates the time from when the control input (enable input: /OE, select input: SEL) is switched until the switch is turned on.
Turn-OFF time (t_off)
Turn-OFF time indicates the time from when the control input (enable input: /OE, select input: SEL) is switched until the switch is turned off.

The timing charts for Start-up time (t_sup), Turn-ON time (t_on), and Turn-OFF time (t_off) are shown in Fig. 2.

Fig. 3 Break before make timing chart and measurement diagram

Break before make (TBBM)
Break before make is a period of time during which two switches are not turned on simultaneously when switching a mux (multiplexer) /de-mux (demultiplexer) circuit.
Please see here for details on Break before make.
What is Break Before Make (TBBM)? | Toshiba Electronic Devices & Storage Corporation | Americas – United States
Fig. 3 shows the timing chart and measurement diagram of the Break before make.

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What are the Switch Characteristics and Timing Characteristics of a bus switch?

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