7.5 Charge Injection

The TMUX110x devices 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 as charge injection,

and is denoted by the symbol QC. Figure 7-5 shows the setup used to measure charge injection from source (S)

to drain (D).

VOUT

Output

VS

0 V

VDD

QC = CL ×

VOUT

VSEL

GND

VS

OUTPUT

CL

S

D

SEL

VDD

VDD

0.1 F

VOUT

VSEL

Figure 7-5. Charge-Injection Measurement Setup

7.6 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 (S) of an off-channel. The characteristic impedance, Z0, for the measurement is 50Ω. Figure 7-6

shows the setup used to measure off isolation. Use off isolation equation to compute off isolation.

GND

NETWORK

ANALYZER

VOUT

S

D

50Ÿ

VSIG

RL

50Ÿ

VS

VDD

0.1µF

Figure 7-6. Off Isolation Measurement Setup

OUT

S

V

Off Isolation

20 Log

V

§

·

˜

¨

¸

©

¹

(1)

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TMUX1101, TMUX1102

SCDS410D – MARCH 2019 – REVISED FEBRUARY 2024

Copyright © 2024 Texas Instruments Incorporated

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