LM317HV_15 Datasheet, PDF (14/28 Pages) Texas Instruments – LMx17HV High Voltage Three-Terminal Adjustable Regulator With Overload Protection

LM117HV, LM317HV
SNVS773D – APRIL 2000 – REVISED SEPTEMBER 2015
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NOTE: *Min. output ≈ 1.2 V
Figure 19. Logic Regulator (5-V) With Electronic Shutdown
9.2.4 Slow Turnon 15-V Regulator
An application of LM117HV includes a PNP transistor with a capacitor to implement slow turnon functionality. As
V_IN rises, the PNP sinks current from the ADJ rail. The output voltage at start-up is the addition of the 1.25-V
reference plus the drop across the base to emitter. While this is happening, the capacitor begins to charge and
eventually opens the PNP. At this point, the device functions normally, regulating the output at 15 V. A diode is
placed between C1 and V_OUT to provide a path for the capacitor to discharge. Such controlled turnon is useful for
limiting the in-rush current.
Figure 20. Slow Turnon 15-V Regulator
9.2.5 Adjustable Regulator With Improved Ripple Rejection
To improve ripple rejection, a capacitor is used to bypass the ADJ pin to GND. This is used to smooth output
ripple by cleaning the feedback path and stopping unnecessary noise from being fed back into the device,
propagating the noise.
†Solid tantalum
*Discharges C1 if output is shorted to ground
Figure 21. Adjustable Regulator With Improved Ripple Rejection
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