LM2647 datasheet(7/25 Pages) NSC

7 / 25 page

Electrical Characteristics (Continued)

Specifications with standard typeface are for T

J = 25˚C, and those with boldface apply over full Operating Junction Tempera-

ture range. VDD = V5 = 5V, V

SGND =VPGND = 0V, VIN = 15V, VEN = 3V, RFADJ = 22.1K unless otherwise stated. (Note 5)

Symbol

Parameter

Conditions

Min

(Note 6)

Typical

(Note 7)

Max

(Note 6)

Units

SW_ZERO

Zero-cross Threshold (SW

Pin)

LDRV goes low

-2.2

Osillator

PWM Frequency

FADJ = 22.1k

Ω

255

300

345

kHz

FADJ = 12.4k

Ω

500

FADJ = 30.9k

Ω

200

PWM Ramp Peak-to-peak

Amplitude

VIN = 15V

1.6

VIN = 24V

2.95

PWM Ramp Valley

0.8

Frequency Change with VIN

VIN = 5.5V to 24V

±1%

Frequency Change with VDD

VDD = 4.5V to 5.5V

±2%

Phase Shift Between

Channels

Phase from HDRV1 to HDRV2

165

180

195

deg

FREQ Pin Voltage vs. VIN

0.105

V/V

System

Minimum ON Time

FPWM =3V

VIN = 5.5V

Maxmimum Duty Cycle

VIN = 15V

VIN = 28V, VDD= 4.5V

Gate Drivers

HDRV Source Impedance

HDRV Pin Current (sourcing)= 1.2A

Ω

HDRV Sink Impedance

HDRV Pin Current (sinking) = 1A

Ω

LDRV Source Impedance

LDRV Pin Current (sourcing) =

1.2A

Ω

LDRV Sink Impedance

LDRV Pin Current (sinking) = 2A

Ω

Cross-conduction protection

delay (deadtime)

HDRV Falling to LDRV Rising

LDRV Falling to HDRV Rising

Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the

device is guaranteed. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics table.

Note 2: PGND1, PGND2 and SGND are all electrically connected together on the PCB.

Note 3: The maximum allowable power dissipation is calculated by using PDmax =(TJMAX -TA)/θJA , where TJMAX is the maximum junction temperature, TA is the

ambient temperature, and

θJA is the junction-to-ambient thermal resistance of the specified package. The 1.0W rating of the TSSOP-28 package for example results

from using 125˚C, 25˚C, and 97˚C/W for TJMAX,TA, and θJA respectively. The 2.85W rating of the 28-pin LLP package results from using 125˚C, 25˚C, and 35˚C/W

for TJMAX,TA, and θJA respectively. The rated power dissipation should be derated by 10mW/˚C above 25˚C ambient for the TSSOP package and 29mW/˚C above

25˚C ambient for the LLP package. The

θJA value above represents the worst-case condition with no heat sinking. Heat sinking will permit more power to be

dissipated at higher ambient temperatures. For detailed information on soldering plastic TSSOP and LLP packages, refer to http://www.national.com/packaging/.

Note 4: ESD is applied by the human body model, which is a 100pF capacitor discharged through a 1.5 k

Ω resistor into each pin.

Note 5: RFADJ is the frequency adjust resistor between FREQ pin and Ground.

Note 6: All limits are guaranteed at room temperature (standard face type) and at temperature extremes (bold face type). All room temperature limits are 100%

production tested. All limits at temperature extremes are guaranteed via correlation using Statistical Quality Control (SQC) methods. All limits are used to calculate

Average Outgoing Quality Level (AOQL).

Note 7: Typical numbers are at 25˚C and represent the most likely norm.

Note 8: If the LM2647 starts up with a pre-charged soft start capacitor, it will first discharge the capacitor to VSS_RESET and then begin the normal Soft-start process.

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