TS507 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TS507 Datasheet PDF : 20 Pages
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TS507
3
Application note
Application note
An application note, based on the TS507, describes three compensation techniques for
solving stability issues when driving large capacitive loads. Two of them are briefly explained
here. For more details, refer to the application note on www.st.com. To find it, do a keyword
search for AN2653.
3.1
Out-of-the-loop compensation technique
The first technique, named the out-of-the-loop compensation, uses an isolation resistor,
ROL, added in series between the output of the amplifier and its load (see Figure 27). The
resistor isolates the op-amp feedback network from the capacitive load. This compensation
method is effective, but the drawback is a limitation on the accuracy of Vout depending on
the resistive load value.
Figure 27. Out-of-the-loop compensation schematics
To help implement the compensation, the abacus given in Figure 28 to Figure 29 provide the
ROL value to choose for a given CL and phase/gain margins. These abacus are plotted in
the case of a voltage follower configuration with a load resistor of 10 kΩ at 25°C.
Figure 28. Gain margin abacus : serial resistor Figure 29. Phase margin abacus : serial
to be added in a voltage follower
resistor to be added in a voltage
configuration at 25°C
follower configuration at 25°C
100
STABLE
10
1
0.1
0.01
10p
100p
UNSTABLE
1n
10n
100n
Load Capacitor (F)
V =5V
cc
V = 2,5 V
icm
T = 25 °C
R = 10 kΩ
L
1µ
10µ
100
10
1
0.1
0.01
10p
100p
STABLE
30 °
20 °
10 °
0°
UNSTABLE
1n
10n
100n
Load Capacitor (F)
V =5V
cc
V = 2,5 V
icm
T = 25 °C
R = 10 kΩ
L
1µ
10µ
15/20
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