The LM3478 is a versatile Low-Side N-Channel MOSFET controller for switching regulators. It is suitable for use in topologies requiring a low side MOSFET, such as boost, flyback, SEPIC, etc. Moreover, the LM3478 can be operated at extremely high switching frequency in order to reduce the overall solution size. The switching frequency of the LM3478 can be adjusted to any value between 100 kHz and 1 MHz by using a single external resistor. Current mode control provides superior bandwidth and transient response, besides cycle-by-cycle current limiting. Output current can be programmed with a single external resistor.
The LM3478 has built-in features such as thermal shutdown, short-circuit protection, over voltage protection, etc. Power saving shutdown mode reduces the total supply current to 5 µA and allows power supply sequencing. Internal soft-start limits the inrush current at start-up.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM3478 | SOIC (8) | 4.90 mm x 3.91 mm |
VSSOP (8) | 3.00 mm x 3.00 mm |
Changes from W Revision (December 2014) to X Revision
Changes from V Revision (February 2013) to W Revision
Changes from U Revision (February 2013) to V Revision
PIN | I/O | DESCRIPTION | |
---|---|---|---|
NAME | NO. | ||
ISEN | 1 | I | Current sense input pin. Voltage generated across an external sense resistor is fed into this pin. |
COMP | 2 | I | Compensation pin. A resistor, capacitor combination connected to this pin provides compensation for the control loop. |
FB | 3 | I | Feedback pin. The output voltage should be adjusted using a resistor divider to provide 1.26 V at this pin. |
AGND | 4 | G | Analog ground pin. |
PGND | 5 | G | Power ground pin. |
DR | 6 | O | Drive pin. The gate of the external MOSFET should be connected to this pin. |
FA/SD | 7 | I | Frequency adjust and Shutdown pin. A resistor connected to this pin sets the oscillator frequency. A high level on this pin for longer than 30 µs will turn the device off. The device will then draw less than 10µA from the supply. |
VIN | 8 | P | Power Supply Input pin. |