lm27953tlx National Semiconductor Corporation, lm27953tlx Datasheet - Page 4

• Manufacturer Part Number: lm27953tlx
• Description: White Led Driver With Four Led Current Sinks And 3/2x Switched Capacitor Boost
• Manufacturer: National Semiconductor Corporation

www.national.com
t
1.5x/1x
Logic Pin Specifications: EN
V
V
I
START
LEAK
Symbol
IL
IH
Electrical Characteristics
Limits in standard typeface are for T
less otherwise specified: V
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 T
120˚C (typ.). The thermal shutdown function is guaranteed by design.
Note 4: The Human body model is a 100pF capacitor discharged through a 1.5kΩ 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 (T
dissipation of the device in the application (P
following equation: T
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: C
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 (R
V
equation applies when the charge pump is operating with a gain of 3/2 (V
Note 11: Headroom voltage: V
Note 12: There is a 300kΩ(typ.) pull-down resistor connected internally between the enable pin (EN) and GND.
Pout
= (1.5 x V
IN
Start-up Time
Charge pump gain cross-over:
Gain = 1.5 when V
threshold. Gain = 1 when V
above threshold.
Input Logic Low
Input Logic High
Input Leakage Current
, C
IN
POUT
) – (R
A-MAX
, C
OUT
1
, and C
Parameter
= T
x I
OUT
J-MAX-OP
OUT
HR
2
IN
). In the equation, I
: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics
= V
) models all voltage losses in the charge pump. R
IN
= 3.6V; V
Pout
is below
– (θ
– V
JA
A-MAX
D-MAX
LEDx
J
x P
IN
= 25˚C, and limits in boldface type apply over the full operating temperature range. Un-
Dx
) is dependent on the maximum operating junction temperature (T
is
D-MAX
), and the junction-to ambient thermal resistance of the part/package in the application (θ
. If headroom voltage requirement is not met, LED current regulation will be compromised.
= 0.6V; EN = 1.5V; R
OUT
(Notes 2, 7) (Continued)
I
1.5x to 1x Threshold
1x to 1.5x Threshold
2.7V ≤ V
2.7V ≤ V
V
V
).
Dx
is the total output current: the sum of all active Dxx output currents and all current drawn from P
EN
EN
= 90% steady state
= 0V
= 3V (Note 12)
IN
IN
≤ 5.5V
≤ 5.5V
IN
≤ 4.75V typ.).
Condition
4
SET
OUT
= 8.35kΩ; C
can be used to estimate the voltage at the charge pump output (P
IN
, C
1
, C
2
, and C
J-MAX-OP
Min
1.1
J
0
= 160˚C (typ.) and disengages at T
POUT
= 125˚C), the maximum power
= 1µF. (Note 8)
4.75
4.55
Typ
350
0.1
10
JA
), as given by the
Max
0.5
V
IN
OUT
Units
OUT
. The
µA
µs
V
V
V
V
J
=
):