LM2591HVT-3.3 National Semiconductor, LM2591HVT-3.3 Datasheet - Page 17

• Manufacturer Part Number: LM2591HVT-3.3
• Description: Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2591HVT-3.3

• Output Voltage: 3.3VDC
• Output Current: 1A
• No. Of Pins: 5
• Termination Type: Through Hole
• Mounting Type: Through Hole
• Peak Reflow Compatible (260 C): No
• Supply Voltage Max: 60V
• Leaded Process Compatible: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Information
This circuit has hysteresis
C
C
Because of differences in the operation of the inverting
regulator, the standard design procedure is not used to
select the inductor value. In the majority of designs, a 33 µH,
3A inductor is the best choice. Capacitor selection can also
be narrowed down to just a few values.
This type of inverting regulator can require relatively large
amounts of input current when starting up, even with light
loads. Input currents as high as the LM2591HV current limit
(approx 4A) are needed for at least 2 ms or more, until the
output reaches its nominal output voltage. The actual time
depends on the output voltage and the size of the output
capacitor. Input power sources that are current limited or
sources that can not deliver these currents without getting
loaded down, may not work correctly. Because of the rela-
tively high startup currents required by the inverting topology,
the delayed startup feature (C1, R
IN
OUT
Regulator starts switching at V
Regulator stops switching at V
470 µF/50V Elec. Panasonic HFQ
220 µF/25V Elec. Panasonic HFQ
— 68 µF/25V Tant. Sprague 595D
— 47 µF/20V Tant. Sprague 595D
FIGURE 10. Undervoltage Lockout with Hysteresis for Inverting Regulator
FIGURE 11. Inverting −5V Regulator with Delayed Startup
IN
IN
1
= 13V
= 8V
and R
2
(Continued)
) shown in Figure
17
11 is recommended. By delaying the regulator startup, the
input capacitor is allowed to charge up to a higher voltage
before the switcher begins operating. A portion of the high
input current needed for startup is now supplied by the input
capacitor (C
capacitor can be made much larger than normal.
lNVERTING REGULATOR SHUTDOWN METHODS
To use the ON /OFF pin in a standard buck configuration is
simple, pull it below 1.3V (
turn regulator ON, pull it above 1.3V to shut the regulator
OFF. With the inverting configuration, some level shifting is
required, because the ground pin of the regulator is no
longer at ground, but is now setting at the negative output
voltage level. Two different shutdown methods for inverting
regulators are shown in Figure 12 and Figure 13
IN
). For severe start up conditions, the input
10129339
@
25˚C, referenced to ground) to
10129340
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