The LM3489 device is a high-efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, cost-effective, switching buck regulator for a wide range of applications. The hysteretic control architecture provides for simple design without any control loop stability concerns using a wide variety of external components. The PFET architecture also allows for low component count as well as ultra-low dropout, 100% duty cycle operation. Another benefit is high efficiency operation at light loads without an increase in output ripple. A dedicated enable pin provides a shutdown mode drawing only 7 µA. Leaving the enable pin unconnected defaults to on.
Current limit protection can be implemented by measuring the voltage across the PFET’s RDS(ON), thus eliminating the need for a sense resistor. A sense resistor may be used to improve current limit accuracy if desired. The cycle-by-cycle current limit can be adjusted with a single resistor, ensuring safe operation over a range of output currents.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM3489 LM3489-Q1 |
VSSOP (8) | 3.00 mm × 3.00 mm |
Changes from B Revision (February 2013) to C Revision
Changes from A Revision (February 2013) to B Revision
PIN | I/O | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
1 | ISENSE | I | The current sense input pin. This pin must be connected to the PFET drain terminal directly or through a series resistor up to 600 Ω for 28 V > VIN > 35 V. |
2 | GND | — | Signal ground |
3 | EN | I | Enable pin. Connect EN pin to ground to shutdown the part or float to enable operation (Internally pulled high). This pin can also be used to perform UVLO function. |
4 | FB | I | The feedback input. Connect the FB to a resistor voltage divider between the output and GND for an adjustable output voltage. |
5 | ADJ | I | Current limit threshold adjustment. Connected to an internal 5.5-µA current source. A resistor is connected between this pin and VIN. The voltage across this resistor is compared with the ISENSE pin voltage to determine if an overcurrent condition has occurred. |
6 | PGND | — | Power ground |
7 | PGATE | O | Gate drive output for the external PFET. PGATE swings between VIN and VIN 5-V. |
8 | VIN | I | Power supply input pin |