LM2793 datasheet(4/10 Pages) NSC

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Electrical Characteristics

(Notes 2, 8)

(Continued)

Note 5: The human-body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. The machine model is a 200pF capacitor discharged directly

into each pin.

Note 6: Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 100

oC), the maximum power

dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), as given by the

following equation: TA-MAX =TJ-MAX-OP -(θJA xPD-MAX). The ambient temperature operating rating is provided merely for convenience. This part may be operated

outside the listed TA rating, so long as the junction temperature of the device does not exceed the maximum operating rating of 100

oC.

Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists,

special care must be paid to thermal dissipation issues. For more information on these topics, please refer to the Power Dissipation section of this datasheet.

Note 8: All room temperature limits are 100% tested or guaranteed through statistical analysis. All limits at temperature extremes are guaranteed by correlation

using standard Statistical Quality Control methods (SQC). All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are not

guaranteed, but do represent the most likely norm.

Note 9: Maximum LED voltage (VDx) is highly dependent on the application’s minimum input voltage and the amount of current flowing through the LEDs. Maximum

LED voltage for a given application can be approximated with the following equations:

IN-MIN< 3.0V: VDx-MAX =(1.5xVIN-MIN)-(IDXx 25 mV/mA) - (3.5

Ω x2xI

DX)

IN-MIN

≥ 3.0V: V

Dx-MAX =4.3V-(IDX x 25 mV/mA)

The equations above assume LEDs are connected to outputs D1 and D2, and no current drawn from the charge pump output (POUT). For a more precise and

thorough analysis of maximum LED voltage, please refer to text sections of the datasheet (to appear in future datasheet revisions - in the interim, please contact

National Semiconductor for more information).

Note 10: Current sources are connected internally between POUT and IDx. The voltage across each current source, [V(POUT) - V(IDx)], is referred to as headroom

voltage. For current sources to regulate properly, a minimum headroom voltage must be present across them. Minimum required headroom voltage is proportional

to the current flowing through the current source, as dictated by this equation: VHR-min = 400mV x (IDx / 16mA).

Block Diagram

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