TL783 Datasheet, PDF (8/13 Pages) Texas Instruments – HIGH-VOLTAGE ADJUSTABLE REGULATOR

TL783
HIGH-VOLTAGE ADJUSTABLE REGULATOR
SLVS036E – SEPTEMBER 1981 – REVISED FEBRUARY 2000
TYPICAL CHARACTERISTICS
LINE TRANSIENT RESPONSE
ÎÎÎÎ ^{TJ = 25°C}
ÎÎÎ Co = 0
0.4
ÎÎÎÎÎÎÎÎ _0.2
Co = 10 µF
ÎÎÎÎÎ 0
–0.2
1
0.5
0
0
1
2
3
4
Time – µs
Figure 13
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 14
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 TL783 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 the output-current curve in Figure 14) or when the load
sinks some portion of the minimum current.
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