LM2744

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SNVS292E – SEPTEMBER 2004 – REVISED JANUARY 2012

Pin Descriptions (continued)

SS/TRACK (Pin 9) - Soft-start and tracking pin. This pin is internally connected to the non-inverting input of the error amplifier during soft-

start, and in fact any time the SS/TRACK pin voltage happens to be below the internal reference voltage. For the basic soft-start function, a

capacitor of minimum value 1nF is connected from this pin to ground. To track the rising ramp of another power supply’s output, connect a

resistor divider from the output of that supply to this pin as described in Application Information.

FB (Pin 10) - Feedback pin. This is the inverting input of the error amplifier, which is used for sensing the output voltage and compensating

the control loop.

FREQ (Pin 11) - Frequency adjust pin. The switching frequency is set by connecting a resistor of suitable value between this pin and

ground. The equation for calculating the exact value is provided in Application Information, but some typical values (rounded up to the

nearest standard values) are 324 k

Ω for 100 kHz, 97.6 kΩ for 300 kHz, 56.2 kΩ for 500 kHz, 24.9 kΩ for 1 MHz.

high-side and low-side drives are off. This pin also features a precision threshold for power supply sequencing purposes, as well as a low

threshold to ensure minimal quiescent current.

to 1.5V can be connected to this pin (with appropriate filtering if necessary).

HG (Pin 14) - High-gate drive pin. This is the gate drive for the high-side N-channel MOSFET. This signal is interlocked with LG (Pin 2) to

avoid shoot-through.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

Absolute Maximum Ratings

(1)

-0.3 to 7V

BOOT Voltage

-0.3 to 21V

All other pins

Junction Temperature

150°C

Storage Temperature

−65°C to 150°C

Soldering Information

Lead Temperature

(soldering, 10sec)

260°C

Infrared or Convection (20sec)

235°C

2 kV

(1)

Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for

which the device operates correctly. Opearting Ratings do not imply guaranteed performance limits.

(2)

The human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin.

Operating Ratings

3V to 6V

−40°C to +125°C

Thermal Resistance (

155°C/W

0.5V to 1.5V

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