SNVS084C December 2001 – July 2016 LM2590HV
PRODUCTION DATA.
| PIN | TYPE(1) | 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. |
| 3 | Flag | O | Open collector output that goes active low (≤1 V) when the output of the switching regulator is out of regulation (less than 95% of its nominal value). In this state it can sink maximum 3 mA. When not low, it can be pulled high to signal that the output of the regulator is in regulation (power good). During power-up, it can be programmed to go high after a certain delay as set by the Delay pin (Pin 5). The maximum rating of this pin must not be exceeded, so if the rail to which it will be pulled-up to is higher than 45 V, a resistive divider must be used instead of a single pull-up resistor, as indicated in Test Circuits. |
| 4 | Ground | G | Circuit ground |
| 5 | Delay | O | This sets a programmable power-up delay from the moment that the output reaches regulation, to the high signal output (power good) on Pin 3. A capacitor on this pin starts charging up by means on an internal (3 μA) current source when the regulated output rises to within 5% of its nominal value. Pin 3 goes high (with an external pull-up) when the voltage on the capacitor on Pin 5 exceeds 1.3 V. The voltage on this pin is clamped internally to about 1.7 V. If the regulated output drops out of regulation (less than 95% of its nominal value), the capacitor on Pin 5 is rapidly discharged internally and Pin 3 will be forced low in about 1/1000th of the set power-up delay time. |
| 6 | Feedback | I | Senses the regulated output voltage to complete the feedback loop. This pin is directly connected to the Output for the fixed voltage versions, but is set to 1.23 V by means of a resistive divider from the output for the adjustable version. If a feedforward capacitor is used (adjustable version), then a negative voltage spike is generated on this pin whenever the output is shorted. This happens because the feedforward capacitor cannot discharge fast enough, and since one end of it is dragged to Ground, the other end goes momentarily negative. To prevent the energy rating of this pin from being exceeded, a small-signal Schottky diode to Ground is recommended for DC input voltages above 40 V whenever a feedforward capacitor is present (see Test Circuits). Feedforward capacitor values larger than 0.1 µF are not recommended for the same reason, whatever be the DC input voltage. |
| 7 | SD/SS | I | Shutdown/Soft-start: The regulator is in shutdown mode, drawing about 90 μA, when this pin is driven to a low level (≤0.6 V), and is in normal operation when this Pin is left floating (internal-pullup) or driven to a high level (≥2 V). The typical value of the threshold is 1.3 V and the pin is internally clamped to a maximum of about 7 V. If it is driven higher than the clamp voltage, it must be ensured by means of an external resistor that the current into the pin does not exceed 1 mA. The duty cycle is minimum (0%) if this Pin is below 1.8 V, and increases as the voltage on the pin is increased. The maximum duty cycle (100%) occurs when this pin is at 2.8 V or higher. So adding a capacitor to this pin produces a soft-start feature. An internal current source will charge the capacitor from zero to its internally clamped value. The charging current is about 5 µA when the pin is below 1.3 V but is reduced to only 1.6 µA above 1.3 V, so as to allow the use of smaller soft-start capacitors. |