TDA3681 View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
TDA3681 Datasheet PDF : 28 Pages
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Philips Semiconductors
Multiple voltage regulator with switch and
ignition buffer
Product specification
TDA3681
Application information
NOISE
Table 1 Noise figures
REGULATOR
1
2
3
4
NOISE FIGURE (µV)(1)
Co = 10 µF
170
440
120
85
Co = 47 µF
110
240
100
70
Co = 100 µF
110
190
80
55
Note
1. Measured at a bandwidth of 30 kHz.
The noise on the supply line depends on the value of the
supply capacitor and is caused by a current noise (the
output noise of the regulators is translated to a current
noise by the output capacitors). The noise is minimal when
a high frequency capacitor of 220 nF in parallel with an
electrolytic capacitor of 100 µF is connected directly to the
supply pins VP1, VP2 and GND.
STABILITY
The regulators are stabilized by the externally connected
output capacitors.
The output capacitors can be selected by using the graphs
given in Figs 12 and 13. When an electrolytic capacitor is
used, its temperature behaviour can cause oscillations at
a low temperature. The two examples below show how an
output capacitor value is selected.
Example 1
Regulators 1, 3 and 4 are stabilized with an electrolytic
output capacitor of 220 µF (ESR = 0.15 Ω). At
Tamb = −30 °C, the capacitor value is decreased to 73 µF
and the ESR is increased to 1.1 Ω. The regulator remains
stable at Tamb = −30 °C (see Fig.12).
Example 2
Regulator 2 is stabilized with a 10 µF electrolytic capacitor
(ESR = 3 Ω). At Tamb = −30 °C, the capacitor value is
decreased to 3 µF and the ESR is increased to 23.1 Ω.
As can be seen from Fig.13, the regulator will be unstable
at Tamb = −30 °C.
Solution
To avoid problems with stability at low temperatures, the
use of tantalum capacitors is recommended. Use a
tantalum capacitor of 10 µF or a larger electrolytic
capacitor.
handbook, halfpa2g0e
ESR
(Ω)
15
10
5
0
0.1
MGL912
maximum ESR
stable region
1
10 C (µF) 100
handbook, halfpage
14
ESR
(Ω) 12
10
8
6
4
2
0
−2
0.22
maximum ESR
MGL913
stable region
minimum ESR
1
10 C (µF) 100
Fig.12 Curve for selecting the value of the output
capacitor for regulators 1, 3 and 4.
Fig.13 Curve for selecting the value of the output
capacitor for regulator 2.
2002 Apr 10
21
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