tc7mb3244cft TOSHIBA Semiconductor CORPORATION, tc7mb3244cft Datasheet - Page 8

• Manufacturer Part Number: tc7mb3244cft
• Description: Low Capacitance Octal Bus Switch
• Manufacturer: TOSHIBA Semiconductor CORPORATION

Rise and Fall Times (tr / tf) of the TC7MB3244C,3245C I/O Signals
The tr(out) and tf(out) values of the output signals are affected by the CR time constant of the input, which consists of
the switch terminal capacitance (C
In practice, the tr(out) and tf(out) values are also affected by the circuit’s capacitance and resistance components other
than those of the TC7MB3244C,3245C.
The tr / tf (out) values can be approximated as follows. (Figure 3 shows the test circuit.)
tr / tf out (approx) = - ( C
Calculation example:
Calculation conditions:
tr out (approx) = - ( 7 + 15 )E-12 ･ ( 120 + 3) ･ ln ( ( ( 4.5 - 0 ) – 2.25 ) / ( 4.5 – 0 ) )
V
Output of the previous IC = digital (i.e., high-level voltage = V
CC
= 4.5V , C
≈ 1.9 ns
Previous IC
R
DRIVE
R
L
DRIVE
= output impedance of the previous IC
= 15pF , R
I/O
+ C
An/Bn
DRIVE
L
) ･ (R
I/O
= 120Ω(output impedance of the previous IC), V
) and the on-resistance (R
TC7MB3244C
TC7MB3245C
(Switch On)
Previous IC
R
DRIVE+
DRIVE
Figure 3
C
R
I/O
ON
R
DRIVE
R
where, R
= output impedance of the previous IC
ON
) ･ ln ( ( ( V
Bn/An
DRIVE
Test Circuit
8
ON
is the output impedance of the previous-stage circuit.
CC
OH
Parameter
; low-level voltage = GND)
) of the input.
TC7MB3244C,3245CFT/FK/FTG
Measure
Measure
– V
Waveform generated with the TC7MB3244C,3245C added
V
M
OL
Waveform generated without the TC7MB3244C,3245C
) – V
M
5.0 ± 0.5 V
) / ( V
V
V
CC
M
CC
tr out
/ 2
= 2.25V (V
OH
V
M
– V
OL
CC
) )
/ 2)
2011-07-01
tf out
V
M
V
CC
GND
V
V
OH
OL