LM27952SD/NOPB National Semiconductor, LM27952SD/NOPB Datasheet - Page 4

• Manufacturer Part Number: LM27952SD/NOPB
• Description: IC LED DRIVR WHITE BCKLGT 14-LLP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Backlight, White LEDr

Specifications of LM27952SD/NOPB

• Constant Current: Yes
• Topology: PWM, Switched Capacitor (Charge Pump)
• Number Of Outputs: 4
• Internal Driver: Yes
• Type - Primary: Backlight, General Purpose
• Type - Secondary: White LED
• Frequency: 525kHz ~ 975kHz
• Voltage - Supply: 3 V ~ 5.5 V
• Voltage - Output: 2.5 V ~ 3.9 V
• Mounting Type: Surface Mount
• Package / Case: 14-LLP
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Efficiency: 85%
• For Use With: LM2795EVAL - BOARD EVALUATION LM2795
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM27952SD; LM27952SDTR

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I
I
R
V
t
IH
IL
ON
Symbol
GDX
OUT
Electrical Characteristics
Limits in standard typeface are for T
range (-40˚C to +85 ˚C). Unless otherwise noted, specifications apply to the LM27952 Typical Application Circuit (pg.1) with V
= 3.6V, V(EN) = 1.8V, V(PWM) = 1.8V, 4 LEDs, 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
140˚C (typ.).
Note 4: The Human-body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin.
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 (θ
standard JESD51-7. The test board is a 4 layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2 x 1 array of thermal vias. The ground plane on the board
is 50mm x 50mm. Thickness of copper layers are 36µm/18µm /18µm/36µm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22˚C, still air. Power
dissipation is 1W.
The value of θ
conditions. In applications where high maximum power dissipation exists (high V
information on these topics, please refer to Application Note 1187: Leadless Leadframe Package (LLP) and the Power Efficiency and Power Dissipation
section of this datasheet..
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: LED Current Matching is based on two calculations: [(I
Dx currents, and I
for the part. The typical specification provided is the most likely norm of the matching figure for all parts.
Note 10: Headroom Voltage = V
Note 11: EN Logic Input High Current (I
Note 12: The open loop output resistance (R
output V
V
current drawn from V
Note 13: Turn-on time is measured from when the EN signal is pulled high until the output voltage on V
OUT
= (G x V
OUT
IN
Logic Input High Current
Logic Input Low Current
Charge Pump Output
Resistance (Note 12)
1x to 3/2x Gain Transition
Voltage Threshold on V
Startup Time
, C
and the maximum current capability of the device under low V
JA
IN
OUT
) - (R
of the LM27952 in LLP-14 could fall in a range as wide as 45
AVG
, C
A-MAX
OUT
OUT
1
is the average Dx current of all four current sinks. The largest number of the two calculations (worst case) is considered the matching figure
, C
Parameter
).
2
x I
= T
: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics
OUT
J-MAX-OP
). In the equation, G is the charge pump gain mode, and I
DX
to GND. If headroom voltage requirement is not met, LED current regulation will be compromised.
- (θ
IH
DX
) is due to a 150kΩ (typ.) pull-down resistor connected internally between the EN and GND pins.
JA
A-MAX
D-MAX
OUT
x P
A
= 25˚C, and limits in boldface type apply over the full operating junction temperature
D-MAX
) models all voltage losses in the charge pump. R
JA
) is dependent on the maximum operation junction temperature (T
Input Pin: PWM
V(PWM) = 1.8V
Input Pin: EN
V(EN) = 1.8V (Note 11)
Input Pins: EN, PWM
V(EN, PWM) = 0V
V
I
DX
), and the junction-to ambient thermal resistance of the part/package in the application (θ
) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC
DX
= 90% steady state
).
Falling
(Notes 2, 7) (Continued)
MAX
DX
= 0.45V, C
- I
AVG
Conditions
IN
) ÷ I
o
and high I
C/W to 150
AVG
4
IN
] and [(I
IN
, high I
= C
OUT
o
C/W (if not wider), depending on PWB material, layout, and environmental
OUT
AVG
OUT
OUT
conditions, beyond what is specified in the electrical specifications table:
), special care must be paid to thermal dissipation issues. For more
- I
is the total output current (sum of all active Dx current sinks and all
= 3.3µF, C
MIN
) ÷ I
OUT
AVG
can be used to estimate the voltage at the charge pump
OUT
]. I
1
crosses 90% of its final value.
MAX
= C
Min
and I
2
= 1µF, R
J-MAX-OP
MIN
J
=150˚C (typ.) and disengages at T
are the highest and lowest respective
Typ
450
330
3.3
10
12
10
= 115
SET
= 12.5kΩ (Note 8)
o
C), the maximum power
Max
JA
), as given by the
Units
mV
nA
µA
nA
µs
Ω
J
=
IN