TDA3665 Datasheet, PDF (8/20 Pages) NXP Semiconductors – Very low dropout voltage/quiescent current 8.5 V voltage regulator

Philips Semiconductors
Very low dropout voltage/quiescent current
8.5 V voltage regulator
Preliminary specification
TDA3665
EXAMPLE 1
The regulator is stabilized with an electrolytic capacitor of
68 µF (ESR = 0.5 Ω). At T_amb = −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 T_amb = −40 °C.
EXAMPLE 2
The regulator is stabilized with an electrolytic capacitor of
10 µF (ESR = 3.3 Ω). At T_amb = −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 T_amb = −40 °C.
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.
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 T_amb = −40 °C.
ndbook, halfpage
VP
C1
1 µF
1
3
TDA3665
VREG = 8.5 V
C2 ⁽²⁾
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:
I_REG(max) = -R----_t--_h---₍-_j---_–--1-_a--5-₎--0-_×----^–-₍--V--T--_P--^a---^m_–----^b_V-----R---_E----_G----₎
2, 4
MBL128
C1 is optional (to minimize supply noise only).
C2 ≤ 4700 µF.
Fig.7 Application circuit with backup function
(SO4 version).
= _{-1---0---01----5-×--0---(--}^–_V----T-P---^a_-–--^m_---8-^b_{--.--5----)(mA)}
When T_amb = 21 °C and V_P = 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.
2000 Apr 25
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