LM2597M-5.0/NOPB National Semiconductor, LM2597M-5.0/NOPB Datasheet - Page 29

• Manufacturer Part Number: LM2597M-5.0/NOPB
• Description: IC REG SIMPLE SWITCHER 8-SOIC
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r
• Type: Step-Down (Buck)r

Specifications of LM2597M-5.0/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 5V
• Current - Output: 500mA
• Frequency - Switching: 150kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Primary Input Voltage: 12V
• No. Of Outputs: 1
• Output Voltage: 5V
• Output Current: 500mA
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Supply Voltage Range: 4.5V To 40V
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Input Voltage Primary Max: 40V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: *LM2597M-5.0; *LM2597M-5.0/NOPB; LM2597M-5.0

Application Information
lNVERTING REGULATOR
The circuit in Figure 29 converts a positive input voltage to a
negative output voltage with a common ground. The circuit
operates by bootstrapping the regulators ground pin to the
negative output voltage, then grounding the feedback pin,
the regulator senses the inverted output voltage and regu-
lates it.
This example uses the LM2597-5 to generate a −5V output,
but other output voltages are possible by selecting other
output voltage versions, including the adjustable version.
Since this regulator topology can produce an output voltage
that is either greater than or less than the input voltage, the
maximum output current greatly depends on both the input
and output voltage. The curve shown in Figure 30 provides a
guide as to the amount of output load current possible for the
different input and output voltage conditions.
FIGURE 28. Typical Circuit Using Shutdown /Soft-start and Error Flag Features
FIGURE 29. Inverting −5V Regulator With Shutdown and Soft-start
(Continued)
29
The maximum voltage appearing across the regulator is the
absolute sum of the input and output voltage, and this must
be limited to a maximum of 40V. In this example, when
converting +20V to −5V, the regulator would see 25V be-
tween the input pin and ground pin. The LM2597 has a
maximum input voltage rating of 40V (60V for the
LM2597HV).
DS012440-48
www.national.com
DS012440-47