8.5 Charge Injection

Charge injection is a measure of the glitch impulse transferred from the digital input to the analog output during

switching, and is denoted by the symbol QINJ. Figure 8-5 shows the setup used to measure charge injection from

the source to drain.

VOUT

Output

VS

0 V

3 V

VSELx

QINJ = CL ×

VOUT

tr < 20 ns

tf < 20 ns

S1

GND

D1

S4

D4

SW

SW

GND

VS

GND

VS

GND

CL

GND

CL

Output

Output

VDD

VSS

VDD

VSS

GND

0.1 µF

GND

0.1 µF

SELx

VSELx

Figure 8-5. Charge-Injection Measurement Setup

8.6 Off Isolation

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

the source pin (Sx) of an off-channel. The characteristic impedance, ZO, for the measurement is 50 Ω. Figure 8-6

and Equation 1 shows the setup used to measure off isolation.

SELx

GND

VSELx

SX

Dx

VS

VOUT

RS

SW

50

Network Analyzer

VDD

VSS

VDD

VSS

GND

0.1 µF

GND

0.1 µF

50

Other

Sx/ Dx

pins

Figure 8-6. Off Isolation Measurement Setup

Off Isolation = 20 × Log VOUTVS

(1)

TMUX8211, TMUX8212, TMUX8213

SCDS434B – OCTOBER 2021 – REVISED MARCH 2023

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