8.1.7 Charge Injection

The TMUX1308 and TMUX1309 device have a transmission-gate topology. Any mismatch in capacitance

between the NMOS and PMOS transistors results in a charge injected into the drain or source during the falling

or rising edge of the gate signal. The amount of charge injected into the source or drain of the device is known

injection from source (Sx) to drain (D).

OUTPUT

C

L

GND

V

OUT

Output

V

S

0 V

V

DD

V

OUT

V

OUT

V

EN

V

DD

V

DD

0.1…F

V

S

D

S5

S6

S7

S0

EN

A0

A1

A2

Figure 8-7. Charge-Injection Measurement Setup

8.1.8 Off Isolation

Off isolation is defined as the ratio of the signal at the drain pin (D) of the device when a signal is applied to the

source pin (Sx) of an off-channel. Figure 8-8 shows the setup used to measure, and the equation to compute off

isolation.

GND

NETWORK

ANALYZER

V

OUT

S

D

50Q

V

SIG

R

L

50Q

S

X

R

L

50Q

V

S

V

DD

0.1µF

Figure 8-8. Off Isolation Measurement Setup

OUT

S

V

Off Isolation

20 Log

V

§

·

˜

¨

¸

©

¹

(1)

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TMUX1308, TMUX1309

SCDS426C – MARCH 2020 – REVISED AUGUST 2020

Copyright © 2020 Texas Instruments Incorporated

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Product Folder Links: TMUX1308 TMUX1309