LM27953 datasheet(4/11 Pages) NSC

4 / 11 page

Electrical Characteristics (Notes 2, 7) (Continued)

Limits in standard typeface are for T

J = 25˚C, and limits in boldface type apply over the full operating temperature range. Un-

less otherwise specified: V

IN = 3.6V; VDx = 0.6V; EN = 1.5V; RSET = 8.35k

Ω;C

IN,C1,C2 , and CPOUT = 1µF. (Note 8)

Symbol

Parameter

Condition

Min

Typ

Max

Units

START

Start-up Time

Dx = 90% steady state

350

µs

1.5x/1x

Charge pump gain cross-over:

Gain = 1.5 when V

IN is below

threshold. Gain = 1 when V

IN is

above threshold.

1.5x to 1x Threshold

4.75

1x to 1.5x Threshold

4.55

Logic Pin Specifications: EN

Input Logic Low

2.7V

≤ V

≤ 5.5V

0.5

Input Logic High

2.7V

≤ V

≤ 5.5V

1.1

LEAK

Input Leakage Current

EN = 0V

0.1

µA

EN = 3V (Note 12)

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

the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the

Electrical Characteristics tables.

Note 2: All voltages are with respect to the potential at the GND pin.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 160˚C (typ.) and disengages at TJ =

120˚C (typ.). The thermal shutdown function is guaranteed by design.

Note 4: The Human body model is a 100pF capacitor discharged through a 1.5k

Ω resistor into each pin. The machine model is a 200pF capacitor discharged

directly into each pin. MIL-STD-883 3015.7

Note 5: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be

derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125˚C), 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).

Note 6: Junction-to-ambient thermal resistance is highly dependent on application and board layout. In applications where high maximum power dissipation exists,

special care must be paid to thermal dissipation issues in board design.

Note 7: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.

Note 8: CIN,CPOUT,C1, and C2 : Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics

Note 9: For the group of outputs on a part, the following are determined: the maximum output current in the group (MAX), the minimum output current in the group

(MIN), and the average output current of the group (AVG). For the group, two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN)/AVG. The largest

number of the two (worst case) is considered the matching figure for the group. The typical specification provided is the most likely norm of the matching figure for

all parts.

Note 10: Output resistance (ROUT) models all voltage losses in the charge pump. ROUT can be used to estimate the voltage at the charge pump output (POUT):

VPout =(1.5xVIN)– (ROUT xIOUT). In the equation, IOUT is the total output current: the sum of all active Dxx output currents and all current drawn from POUT. The

equation applies when the charge pump is operating with a gain of 3/2 (VIN ≤ 4.75V typ.).

Note 11: Headroom voltage: VHR =VPout –VLEDx . If headroom voltage requirement is not met, LED current regulation will be compromised.

Note 12: There is a 300k

Ω(typ.) pull-down resistor connected internally between the enable pin (EN) and GND.

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