The LM2599 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 3-A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an adjustable output version.
The LM2598 is a member of the LM259x family, with additional supervisory and performance features added.
Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, improved line and load specifications, fixed-frequency oscillator, Shutdown and Soft-start, error flag delay, and error flag output.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM2599 | TO-220 (7) | 14.986 mm × 10.16 mm |
TO-263 (7) | 10.10 mm × 8.89 mm |
Changes from C Revision (April 2013) to D Revision
Changes from B Revision (April 2013) to C Revision
The LM2599 series operates at a switching frequency of 150 kHz, thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Available in a standard 7-pin TO-220 package with several different lead bend options, and a 7-pin TO-263 surface-mount package.
A standard series of inductors (both through-hole and surface-mount types) are available from several different manufacturers optimized for use with the LM2599 series. This feature greatly simplifies the design of switch-mode power supplies.
Other features include a ±4% tolerance on output voltage under all conditions of input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 80-μA standby current. Self-protection features include a two stage current limit for the output switch and an overtemperature shutdown for complete protection under fault conditions.
PIN | I/O | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
1 | +VIN | I | This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. |
2 | Output | O | Internal switch. The voltage at this pin switches between approximately (+VIN − VSAT) and approximately −0.5 V, with a duty cycle of VOUT/VIN. To minimize coupling to sensitive circuitry, the PCB copper area connected to this pin must be kept to a minimum. |
3 | Error Flag | O | Open-collector output that provides a low signal (flag transistor ON) when the regulated output voltage drops more than 5% from the nominal output voltage. On start up, Error Flag is low until VOUT reaches 95% of the nominal output voltage and a delay time determined by the Delay pin capacitor. This signal can be used as a reset to a microprocessor on power-up. |
4 | Ground | — | Circuit ground. |
5 | Delay | O | At power-up, this pin can be used to provide a time delay between the time the regulated output voltage reaches 95% of the nominal output voltage, and the time the error flag output goes high. |
6 | Feedback | I | Senses the regulated output voltage to complete the feedback loop. |
7 | Shutdown/Soft-start | I | This dual function pin provides the following features: (a) Allows the switching regulator circuit to be shut down using logic level signals thus dropping the total input supply current to approximately 80 μA. (b) Adding a capacitor to this pin provides a soft-start feature which minimizes start-up current and provides a controlled ramp up of the output voltage. |