TL783C_07 Datasheet, PDF (9/15 Pages) Texas Instruments – HIGH-VOLTAGE ADJUSTABLE REGULATOR

TL783C, TL783Y
HIGH-VOLTAGE ADJUSTABLE REGULATOR
SLVS036C – SEPTEMBER 1981 – REVISED APRIL 1997
TYPICAL CHARACTERISTICS
LINE TRANSIENT RESPONSE
0.4
0.2
ÎÎÎÎ _{TJ = 25°C}
ÎÎÎÎÎ _{Co = 0}
ÎÎÎÎÎÎÎÎÎÎÎÎ _{Co = 10 µF}
0
–0.2
1
0.5
0
0
1
2
3
4
Time – µs
Figure 15
LOAD TRANSIENT RESPONSE
6
4
2
0
–2
–4
–6
0.8
0.6
0.4
0.2
0
0
VI = 35 V
VO = 10 V
Co = 1 µF
TJ = 25°C
40
80 120 160
Time – µs
Figure 16
200 240
DESIGN CONSIDERATIONS
The internal reference (see functional block diagram) generates 1.25 V nominal (V_ref) between OUT and ADJ.
This voltage is developed across R1 and causes a constant current to flow through R1 and the programming
resistor R2, giving an output voltage of:
V_{O =} V_ref (1 + R2/R1) + l_I(ADJ) (R2)
or
V_O ~ V_ref (1 + R2/R1).
The TL783C was designed to minimize the input current at ADJ and maintain consistency over line and load
variations, thereby minimizing the associated (R2) error term.
To maintain I_I(ADJ) at a low level, all quiescent operating current is returned to the output terminal. This quiescent
current must be sunk by the external load and is the minimum load current necessary to prevent the output from
rising. The recommended R1 value of 82 Ω provides a minimum load current of 15 mA. Larger values can be
used when the input-to-output differential voltage is less than 125 V (see output current curve, Figure 14) or
when the load sinks some portion of the minimum current.
bypass capacitors
The TL783C regulator is stable without bypass capacitors; however, any regulator becomes unstable with
certain values of output capacitance if an input capacitor is not used. Therefore, the use of input bypassing is
recommended whenever the regulator is located more than four inches from the power-supply filter capacitor.
A 1-µF tantalum or aluminum electrolytic capacitor is usually sufficient.
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