1

10

100

1000

0.01

0.1

1

10

100

1000

C

60°Phase Margin

45°Phase Margin

C041

0

1/

20

40

60

80

10

100

1k

10k

100k

1M

100

120

10M

100M

Frequency (Hz)

20 dB

ROC

dec

40 dB

1 dec

z

ISO

LOAD

1

f

2

R

C

Œ

u

u

u

p

ISO

o

LOAD

1

f

2

R

R

C

Œ

u

u

u

21

TLV172, TLV2172, TLV4172

www.ti.com

SBOS784 – NOVEMBER 2016

Product Folder Links: TLV172 TLV2172 TLV4172

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Copyright © 2016, Texas Instruments Incorporated

Typical Application (continued)

ROC stability analysis is typically simulated. The validity of the analysis depends on multiple factors, especially

measurement of overshoot percentage and ac gain peaking of the circuit using a function generator,

oscilloscope, and gain and phase analyzer. Phase margin is then calculated from these measurements. Table 3

shows the overshoot percentage and ac gain peaking that correspond to phase margins of 45° and 60°. For

more details on this design and other alternative devices that can be used in place of the TLV172, see the

Capacitive Load Drive Solution Using an Isolation Resistor precision design.

Table 3. Phase Margin versus Overshoot and AC Gain

Peaking

PHASE

MARGIN

OVERSHOOT

AC GAIN PEAKING

45°

23.3%

2.35 dB

60°

8.8%

0.28 dB

9.2.3 Application Curve

capacitive loads were determined. The results are shown in Figure 31.

Figure 31. Isolation Resistor Required for Various Capacitive Loads to Achieve a Target Phase Margin