TDA3665 datasheet(8/20 Pages) PHILIPS

8 / 20 page

2000 Apr 25

Philips Semiconductors

Preliminary speciﬁcation

Very low dropout voltage/quiescent current

8.5 V voltage regulator

TDA3665

EXAMPLE 1

The regulator is stabilized with an electrolytic capacitor of

µF (ESR = 0.5 Ω). At Tamb = −40 °C, the capacitor

value is decreased to 22

µF and the ESR is increased

to 3.5

Ω. The regulator will remain stable at a temperature

of Tamb = −40 °C.

EXAMPLE 2

The regulator is stabilized with an electrolytic capacitor of

µF (ESR = 3.3 Ω). At Tamb = −40 °C, the capacitor

value is decreased to 3

µF and the ESR is increased

to 20

Ω. The regulator will remain stable at a temperature

of Tamb = −40 °C.

EXAMPLE 3

The regulator is stabilized with a 100 nF MKT capacitor

connected to the output. When the output current is over

200

µA full stability is guaranteed.

Because the thermal influence on the capacitor value is

almost zero, the regulator will remain stable at a

temperature of Tamb = −40 °C.

EXAMPLE 4

The regulator is stabilized with a 100 nF capacitor in

parallel with an electrolytic capacitor of 10

µF connected to

the output.

The regulator is now stable under all conditions and

independent of:

• The ESR of the electrolytic capacitor

• The value of the electrolytic capacitor

• The output current.

Application circuits

The maximum output current of the regulator equals:

When Tamb =21 °C and VP = 17.5 V the maximum output

current equals 140 mA.

The total thermal resistance of the TDA3665 can be

decreased from 125 to 50 K/W for the SO8 version. For

the SO4 version it can be decreased from 100 to 40 K/W

when GND pins 2 and 4 of the package are soldered to

the printed-circuit board.

Application circuit with backup function

Sometimes a backup function is needed to supply, for

example, a microcontroller for a short period of time when

the supply voltage spikes to 0 V (or even

−1 V).

This function can easily be built with the TDA3665 by using

an output capacitor with a large value. When the supply

voltage is 0 V (or

−1 V), only a small current will flow into

pin REG from this output capacitor (a few

µA).

The application circuit is given in Fig.7.

REG max

()

150

amb

–

th j

–

()

REG

–

()

-----------------------------------------------------------

150

amb

–

100

8.5

–

()

------------------------------------------ mA

()

ndbook, halfpage

MBL128

2, 4

C2(2)

TDA3665

µF

VREG = 8.5 V

Fig.7

Application circuit with backup function

(SO4 version).

C1 is optional (to minimize supply noise only).

≤ 4700 µF.

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